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Printed porous titanium metaphyseal cones have become a mainstay for managing bone loss in revision total knee arthroplasty (rTKA). A short or long stem is routinely used when implanting a cone to augment fixation and offload stresses. This retrospective analysis compared the short-term survivorships and functional outcomes for use of a short or long stem with a metaphyseal cone.A total of 179 cases using metaphyseal cones and stems with median follow-up of 1.95 years (interquartile range, 1.00-2.14) were compared based on stem type. There were 55 cases with long stem(s) and 124 cases with short stem(s). Cases with both long and short stems were excluded. Demographics, Kaplan-Meier survivorships, and preoperative and 1-year postoperative patient-reported outcome measures (PROMs; 2011 Knee Society Score [KSS] objective knee score, function, and satisfaction scores; EuroQol five-dimension scale; and Short Form Survey Physical Component Summary and Mental Component Summary scores) were compared using t -tests with a significance level of α = 0.05. There were no significant differences in body mass index (mean ± standard deviation) or sex (men [%]) between the short and long stem cohorts (32.3 ± 5.3, 36.3% and 31.5 ± 5.5, 38.2%, respectively; p  > 0.05). Patients who had short stems were younger (65.9 ± 8.8 vs. 69.0 ± 9.4, p  = 0.0323).Revision-free survivorship for the femoral or tibial component was 100% for long stems and 98.2% for short stems at 1 and 2 years, respectively (log-rank p  = 0.6330). The two revisions in the short group were for infection, thus the survivorship for aseptic loosening was 100% at 2 years for both cohorts. There were no significant differences in preoperative or postoperative PROMs.This study demonstrated that highly porous printed metaphyseal cones provided rTKA with excellent early survivorship and similar PROMs whether a short or long stem was used. Additional studies will be needed to discern longer term differences., Competing Interests: None declared., (Thieme. All rights reserved.)

Arthrofibrosis following primary total knee arthroplasty (TKA) can result in pain and limit postoperative range of motion (ROM), jeopardizing clinical outcomes and patient satisfaction. This study aims to identify preoperative risk factors associated with necessitating a manipulation under anesthesia (MUA) following primary TKA.We retrospectively reviewed 950 cases of consecutive primary TKAs performed at one institution by three arthroplasty surgeons between May 2017 and May 2019. Recorded preoperative variables included smoking status, race, preoperative ROM, presence of effusion or positive anterior drawer, and medical comorbidities. Demographic characteristics were compared with Student's t -tests or chi-square tests as appropriate. For each preoperative factor, we obtained an odds ratio (OR) for MUA risk using multivariate logistic regression.Twenty (2.3%) patients underwent MUA following their index primary TKA surgery. History of ipsilateral knee surgery (OR: 2.727, p  = 0.047) and diagnosed hypertension (OR: 4.764, p  = 0.016) were identified as risk factors associated with significantly increased risk of MUA. The greater the preoperative ROM, the higher likelihood needed of MUA (OR: 1.031, p  = 0.034).Patients who had diagnosed hypertension or a history of prior ipsilateral knee surgery were associated with increased risk of necessitating an MUA following primary TKA. Additionally, a greater total arc of motion preoperatively increased the odds of needing MUA.Level III of evidence was present., Competing Interests: None declared., (Thieme. All rights reserved.)

The spacer block technique is widely used in medial fixed-bearing unicompartmental knee arthroplasty (UKA) for osteoarthritis (OA) and osteonecrosis (ON), while it is still unclear if there is any difference in the extension gap between UKAs for the two conditions. To clarify the question, the data from 87 consecutive patients (OA: 57 patients and ON: 30 patients) who underwent medial fixed-bearing UKA with the spacer block technique were retrospectively collected and analyzed. The component gap between the medial tibial osteotomy surface and the femoral trial prosthesis in extension was measured using a UKA tensor, and the preosteotomy gap was calculated in each condition. Also, pre- and postoperative coronal hip-knee-ankle (HKA) angles, the thickness of the insert, and the amount of distal femoral and proximal tibial osteotomy were measured and compared between the two groups. As a result, the mean preosteotomy gap in Group OA and Group ON was 5.4 and 3.7 mm, respectively ( p  < 0.001). The amount of change in HKA angle following UKA in Group OA and Group ON was 4.4and 3.8 degrees, respectively ( p  = 0.044), while no significant difference was found regarding pre- and postoperative HKA angle between them. Also, thinner inserts tended to be used in Group ON than in Group OA, while no significant difference in the amount of osteotomies was found between them. Since knees with OA and ON showed different biomechanical conditions at medial fixed-bearing UKA probably for the difference in the amount of remaining cartilage, the surgical technique should be carefully considered for each condition., Competing Interests: R.K. declares Consulting fees from Medacta lnternational, Arthrex, lnc., and Japan Tissue Engineering Co., Ltd, Payment or honoraria from Zimmer Biomet, Smith & Nephew KK, Johnson & Johnson KK, Japan Tissue Engineering Co., Ltd, Arthrex Japan G.K. He is Associate Editor for Knee Surgery, Sports Traumatology, Arthroscopy (KSSTA)., (Thieme. All rights reserved.)

Meniscus allograft transplantation (MAT) is a proven treatment option for patients with symptomatic irreparable meniscus deficiency. When patients are adherent to prescribed postoperative restriction and rehabilitation protocols, outcomes after MAT are considered good to excellent. However, nonadherence to standard protocols is common and can be associated with undesirable outcomes and patient dissatisfaction. Based on demonstrated safety for early weight-bearing following MAT in conjunction with significant advances in graft preservation and surgical techniques, our joint preservation center implemented a shift in practice toward accelerated weight-bearing following MAT and designed this study to test the hypothesis that accelerated rehabilitation would be associated with superior adherence, patient-reported outcomes, and patient satisfaction, without diminishing patient safety, when compared with standard rehabilitation. Patients were included for analyses when they had undergone fresh or fresh-frozen MAT using a double bone plug technique for treatment of medial or lateral meniscus deficiency and had at least 1-year treatment outcomes recorded. The results of this study revealed that patients who were prescribed accelerated rehabilitation after MAT were significantly more adherent than patients who were prescribed standard rehabilitation and reported statistically significant and clinically meaningful improvements in knee pain and function for at least 1-year following MAT, whereas those in the standard cohort did not. While not statistically different, treatment failure rate was lower in the accelerated rehabilitation cohort when compared with the standard rehabilitation cohort (11 vs. 29%). Importantly, initial outcomes for revision MAT were associated with short-term success in all the patients who opted for this option in the study population. These data suggest that accelerated weight-bearing after MAT is safe, promotes patient adherence, and is associated with statistically significant and clinically meaningful improvements in patient-reported knee pain and function at early and mid-term follow-up., Competing Interests: • J.P.S. is a board or committee member for the American Orthopaedic Association; is a board or committee member for AO Foundation; is a board or committee member for AO North America; is a paid consultant and receives research support from Arthrex, Inc; is a paid consultant for DePuy, Johnson & Johnson Company; is on the editorial or governing board for the Journal of Knee Surgery; is a board or committee member for Mid-America Orthopaedic Association; receives research support from National Institutes of Health (NIAMS & NICHD); is a paid consultant for Orthopedic Designs North America; is a paid consultant for Smith & Nephew; receives publishing royalties, financial or material support from Thieme; and receives research support from U.S. Department of Defense.• C.W.N. is a board or committee member for AAOS; is a board or committee member for American Orthopaedic Society for Sports Medicine; receives other financial or material support from AO Foundation; is a paid presenter or speaker for Arthrex, Inc; is on the editorial or governing board, receives publishing royalties, financial or material support from Arthroscopy; is a board or committee member for Arthroscopy Association of North America; is a paid consultant for Guidepoint Consulting; and is a paid presenter or speaker for Vericel, Inc.• J.L.C. receives research support from AANA; receives research support from AO Trauma; receives IP royalties, is a paid consultant and receives research support from Arthrex, Inc; is a paid consultant from Bioventus; is a paid consultant for Boehringer Ingelheim; is a paid consultant and receives research support from Collagen Matrix Inc; receives research support from GE Healthcare; is on the editorial or governing board of the Journal of Knee Surgery; is a board or committee member for Midwest Transplant Network; is a board or committee member, receives IP royalties and research support from Musculoskeletal Transplant Foundation; receives research support from National Institutes of Health (NIAMS & NICHD); receives research support from OREF; receives research support from Orthopaedic Trauma Association; receives research support from PCORI; receives research support from Regenosine; receives research support from SITES Medical; receives publishing royalties, financial or material support from Thieme; is a paid consultant for Trupanion; and receives research support from U.S. Department of Defense.• K.R. and C.C. have no conflict of interest to disclose., (Thieme. All rights reserved.)

This study examines the correlation between the weight-bearing (WB) long leg radiograph (LLR)-derived hip-knee-ankle angle (HKAA) and intraoperative supine computer-assisted surgery (CAS)-derived HKAA measurements at the beginning and end of total knee arthroplasty (TKA). The primary aim of the study was to determine if WB alignment could be mimicked or inferred based on intraoperative alignment findings. We conducted a prospective analysis from a cohort of 129 TKAs undergoing a CAS TKA at a single center by a single surgeon. The HKAA was recorded using the CAS navigation system immediately postregistration of navigation data and after implantation of the prosthesis. The intraoperative HKAA was recorded in both the supine "resting" position of the knee and also while the knee was manipulated in an effort to replicate the patient's WB alignment. These measurements were compared with the HKAA recorded on pre- and postoperative WB LLRs. There was a strong correlation between the preoperative WB LLR HKAA and the intraoperative preimplant CAS-derived stressed HKAA ( R  = 0.946). However, there was no correlation between the postoperative WB LLR HKAA and the postimplant insertion HKAA as measured intraoperatively via CAS for either a "resting" or "stressed" position of the operated knee ( R  = 0.165 and R  = 0.041, respectively). Thus, the interpretation of intraoperative alignment data is potentially problematic. Despite technological advances in the development and utilization of computer navigation and robotics in arthroplasty to help obtain the optimal alignment, it would seem apparent from our study that this alignment does not correlate to upright stance postoperatively. Surgeons should apply caution to the strength of assumptions they place on intraoperative coronal plane alignment findings., Competing Interests: None declared., (Thieme. All rights reserved.)

Following knee surgery, clinicians have traditionally used visually rated or time-based assessments of lower extremity movement quality to measure surgical outcomes, plan rehabilitation interventions, and measure success. These methods of assessment are prone to error and do not fully capture a patient's inefficient movement patterns post surgery. Further, currently available systems which objectively measure kinematics during these tasks are expensive and unidimensional. For these reasons, recent research has called for the development of objective and low-cost precision rehabilitation tools to improve clinical measurement of movement tasks. The purpose of this article is to highlight two such tools and their applications to knee surgery. The systems highlighted within this article are the Mizzou Point-of-Care Assessment System (MPASS) and the Mizzou Knee Arthrometer Testing System (MKATS). MPASS has demonstrated high levels of agreement with the gold-standard Vicon system in measuring kinematics during sit-to-stand ( R  > 0.71), lateral step-down (intraclass correlation coefficient [ICC] > 0.55, apart from ankle flexion), and drop vertical jump tasks (ICC > 0.62), as well as gait ( R  > 0.87). MKATS has been used to quantify differences in tibiofemoral motion between groups during lateral step-down, step-up-and-over, and step-up/step-down tasks. Objective measurement of clinical tasks using portable and inexpensive instruments, such as the MPASS and MKATS, can help clinicians identify inefficient movement patterns and asymmetries which may damage and wear down supporting structures within the knee and throughout the kinetic chain causing pain and discomfort. Identifying these issues can help clinicians to plan interventions and measure their progress at a lower cost than currently available systems. The MPASS and MKATS are useful tools which have many applications to knee surgery., Competing Interests: T.G. reports grants from University of Missouri Coulter Biomedical Accelerator. T.G. and J.H. report patents “Joint Motion Measurement Apparatus and Method of Use (application 17/797,038)” and “Point-of-care Assessment System (no. 17/970095).”, (Thieme. All rights reserved.)

The aim of this study was to reveal the influence of the morphological variations of the Blumensaat's line on anteromedial (AM) and posterolateral (PL) femoral tunnel position in anatomical double-bundle anterior cruciate ligament (ACL) reconstruction.Fifty-three subjects undergoing anatomical double-bundle ACL reconstruction were included (29 female, 24 male; median age 27.4 years; range: 14-50 years). Using an inside-out transportal technique, the PL tunnel position was made on a line drawn vertically from the bottommost point of the lateral condyle at 90 degrees of knee flexion, spanning a distance of 5 to 8 mm, to the edge of the joint cartilage. AM tunnel position was made 2 mm distal to the PL tunnel position. Following Iriuchishima's classification, the morphology of the Blumensaat's line was classified into straight and hill (large and small) types. Femoral tunnel position was determined using the quadrant method. A Mann-Whitney U test was performed to compare straight and hill type knees according to AM and PL femoral tunnel position.There were 18 straight and 35 hill type knees (13 small and 22 large hill). AM and PL femoral tunnel position in straight type knees were 21.7 ± 7.0 and 33.6 ± 10.5% in the shallow-deep direction, and 42.1 ± 11.1 and 72.1 ± 8.5% in the high-low direction, respectively. In hill type knees, AM and PL femoral tunnel position were 21.3 ± 5.8 and 36.9 ± 7.1% in the shallow-deep direction, and 44.6 ± 10.7 and 72.1 ± 9.7% in the high-low direction, respectively. No significant difference in AM or PL femoral tunnel position was detected between straight and hill type knees.AM and PL femoral tunnel position in anatomical double-bundle ACL reconstruction was not affected by the morphological variations of the Blumensaat's line. Surgeons do not need to consider Blumensaat's line morphology if AM and PL femoral tunnel position is targeted at the bottommost point of the lateral condyle. This was a level of evidence III study., Competing Interests: None declared., (Thieme. All rights reserved.)

Competing Interests: J.L.C. receives research support from AANA; receives research support from AO Trauma; receives IP royalties, is a paid consultant and receives research support from Arthrex, Inc; is a paid consultant for Bioventus; is a paid consultant for Boehringer Ingelheim; is a paid consultant and receives research support from Collagen Matrix Inc; receives research support from GE Healthcare; is on the editorial or governing board for the Journal of Knee Surgery; is a board or committee member for Midwest Transplant Network; is a board or committee member, receives IP royalties and research support from Musculoskeletal Transplant Foundation; receives research support from the National Institutes of Health (NIAMS & NICHD); receives research support from OREF; receives research support from Orthopaedic Trauma Association; receives research support from PCORI; receives research support from Regenosine; receives research support from SITES Medical; receives publishing royalties, financial or material support from Thieme; is a paid consultant for Trupanion; and receives research support from U.S. Department of Defense.

We analyzed the intraoperative kinematics of total knee arthroplasty (TKA) using a navigation system to investigate the influence of different inserts on kinematics. This was a retrospective observational study. The Vanguard individualized design (33 patients, 33 knees) XP and anterior-stabilized (AS) inserts were used in TKA for osteoarthritis. Kinematic data were intraoperatively recorded. The range of motion, tibiofemoral rotational angle, anteroposterior translation of the femur, and varus-valgus laxity were compared between the two inserts (XP vs. AS). There was no significant difference in the range of motion (extension: XP, 3.7° ± 3.3° vs. AS, 3.8° ± 3.3°, p  = 0.84; flexion: XP, 138.1° ± 10.2° vs. AS, 139.0° ± 13.3°, p  = 0.73). With the AS insert, the tibia was gradually internally rotated as the knee was flexed. At maximum extension, the internal rotation was smallest with AS (XP 6.5° ± 4.0° vs. AS 5.1° ± 3.4°, p  = 0.022), which was also associated with smaller anterior femoral translation (maximum extension: XP, 14.1 ± 4.8 mm vs. AS, 11.3 ± 4.7 mm, p  = 0.00036; 30°: XP, 23.7 ± 5.6 mm vs. AS, 20.7 ± 5.1 mm, p  = 0.000033; 45°: XP, 24.4 ± 4.9 mm vs. AS, 23.2 ± 4.5 mm, p  = 0.0038). The AS was associated with a lower varus-valgus laxity (30° XP 4.1° ± 3.4 vs. AS 3.3° ± 2.7°, p  = 0.036; 60°: XP, 3.2° ± 3.0° vs. AS, 2.4° ± 3.3°, p  = 0.0089). The AS insert facilitated sequential tibiofemoral rotation with varus-valgus stability in mid-flexion without restricting the range of motion., Competing Interests: None declared., (Thieme. All rights reserved.)

The knee joint plays a pivotal role in mobility and stability during ambulatory and standing activities of daily living (ADL). Increased incidence of knee joint pathologies and resulting surgeries has led to a growing need to understand the kinematics and kinetics of the knee. In vivo, in silico, and in vitro testing domains provide researchers different avenues to explore the effects of surgical interactions on the knee. Recent hardware and software advancements have increased the flexibility of in vitro testing, opening further opportunities to answer clinical questions. This paper describes best practices for conducting in vitro knee biomechanical testing by providing guidelines for future research. Prior to beginning an in vitro knee study, the clinical question must be identified by the research and clinical teams to determine if in vitro testing is necessary to answer the question and serve as the gold standard for problem resolution. After determining the clinical question, a series of questions ( What surgical or experimental conditions should be varied to answer the clinical question, what measurements are needed for each surgical or experimental condition, what loading conditions will generate the desired measurements, and do the loading conditions require muscle actuation? ) must be discussed to help dictate the type of hardware and software necessary to adequately answer the clinical question. Hardware (type of robot, load cell, actuators, fixtures, motion capture, ancillary sensors) and software (type of coordinate systems used for kinematics and kinetics, type of control) can then be acquired to create a testing system tailored to the desired testing conditions. Study design and verification steps should be decided upon prior to testing to maintain the accuracy of the collected data. Collected data should be reported with any supplementary metrics (RMS error, dynamic statistics) that help illuminate the reported results. An example study comparing two different anterior cruciate ligament reconstruction techniques is provided to demonstrate the application of these guidelines. Adoption of these guidelines may allow for better interlaboratory result comparison to improve clinical outcomes., Competing Interests: R.C., J.L., C.G., and T.N. receive royalties for simVITRO system licensed through Cleveland Clinic Innovations Department., (Thieme. All rights reserved.)

Postoperative flexion after unicompartmental knee arthroplasty might be predicted from the preoperative range of motion and other preoperative factors, but this has not been sufficiently investigated. Between 2013 and 2017, 198 patients (198 knees) underwent unilateral knee arthroplasty with medial mobile-bearing unicompartmental knee arthroplasty. Range of motion was measured preoperatively and at the time of final follow-up. To investigate the accuracy of the prediction of preoperative to postoperative gain or loss of the flexion angle, we performed receiver operating characteristic analysis. Logistic regression analysis was used to evaluate other predictive factors. Change in flexion angle was significantly strongly and negatively correlated with the preoperative flexion angle ( R  = - 0.688; 95% confidence interval: -0.755 to -0.607; p  < 0.001). Preoperative flexion angle was suggested to be a significant predictor of gain or loss of the flexion angle with the area under the curve of 0.781; the cutoff value calculated using the Youden index was 140 degrees. Logistic regression analysis showed that in addition to the preoperative flexion angle of the operated side, the postoperative flexion range was significantly affected by the patient's height and by the preoperative flexion angle of the contralateral knee. If the preoperative flexion angle in Oxford mobile-bearing medial unicompartmental knee arthroplasty is <140 degrees, the postoperative flexion angle may be improved; if it exceeds 140 degrees, the postoperative flexion angle may worsen. This predictive ability is further improved by consideration of the patient's height and the range of motion on the contralateral side., Competing Interests: None declared., (Thieme. All rights reserved.)

One of the critical steps in total knee arthroplasty is femoral component positioning and sizing. Historically, there was wider variability between femoral component sizes, necessitating the concepts of anterior referencing (AR) and posterior referencing (PR). With the introduction of smaller increments between sizes, the concept of anatomic referencing has been introduced to replace AR and PR. The intent of this study was to validate the concept of anatomic referencing and show that with 2 mm increments in femoral sizes, the femoral component can be placed flush to the anterior cortex while maintaining posterior condylar offset (PCO). Digital surface models were created using 515 femurs from an established computed tomography database. Virtual bone resections, component sizing and placement were performed assuming neutral mechanical axis and a cartilage thickness of 2 mm. The appropriately sized femoral component, which had 2 mm incremental sizes, was placed flush with the anterior cortex with restoration of the PCO. The anterior-posterior distance from the posterior surface of the component to the medial and lateral surfaces of the posterior condylar cartilage were measured. The medial condyle was the limiting condyle in the majority of cases (73%). The average medial gap after appropriate femoral component matching was 0.6 mm (0.39-1.41 mm) across all sizes. The overall average condylar gap was 1.02 mm. The most common femoral component was a size 7 (57.2 mm) and the average femoral AP width was 55.9 mm. Anatomic referencing with an implant system that has 2-mm increments in femoral component sizing provides an alternative to AR and PR without compromise. Anatomic referencing allows for perfect alignment of the anterior flange of the femoral component to the anterior cortex of the femur while restoring the native PCO to within 1 mm. This avoids having to choose between AR or PR when in between femoral sizes., Competing Interests: J.B. reports being a board member of Orthopaedic Research Society. Stocks Zimmer Biomet. G.R.S. reports royalties from Zimmer Biomet. Consulting fee from Zimmer Biomet, 3M KCI, and Canary. Payment or honoraria from Zimmer Biomet and 3M KCI. Participation on a Advisory Board of Canary and Enhanced Medical Nutrition. Stocks of ROM Tech, KAT Robotics, and Enhanced Medical Nutrition., (Thieme. All rights reserved.)

Soft-tissue balancing is an important factor in primary total knee arthroplasty (TKA), with 30 to 50% of TKA revisions attributed to technical operative factors including soft-tissue balancing. Robotic-assisted TKA (RATKA) offers opportunities for improved soft-tissue balancing methods. This study aimed to evaluate the repeatability and reproducibility of ligamentous laxity assessments during RATKA using a digital tensioner.Three experienced RATKA surgeons assessed preresection and trialing phases of 12 human cadaveric knees with varying degrees of arthritis. Ligamentous laxity was assessed with manual varus and valgus stresses in extension and flexion, with a digital tensioner providing feedback on the change of laxity displacement. Intraclass correlation coefficient (ICC) analyses were used to determine the repeatability within a single surgeon and reproducibility between the three surgeons.The results showed excellent repeatability and reproducibility in ligamentous laxity assessment during RATKA. Surgeons had excellent repeatability for preresection and trialing assessments, with median ICC values representing excellent reproducibility between surgeons. Surgeons were repeatable within 1 or 1.5 mm for preresection and trialing assessments. On average, the variation within a surgeon was 0.33 ± 0.26 mm during preresection and 0.29 ± 0.28 mm during trialing. When comparing surgeons to each other, they were reproducible within an average of 0.69 ± 0.33 mm for preresection and 0.65 ± 0.31 mm for trialing.This study demonstrated the reliability of robotic-assisted soft-tissue balancing techniques, providing control over ligamentous laxity assessments, and potentially leading to better patient outcomes. The digital tensioner used in this study provided excellent repeatability and reproducibility in ligamentous laxity assessment during RATKA, highlighting the potential benefits of incorporating robotics in TKA procedures., Competing Interests: None declared., (Thieme. All rights reserved.)

Mobile-bearing (MB) unicompartmental knee arthroplasty (UKA) has high conformity between the femoral articular surface and the meniscal bearing; therefore, the surface and subsurface contact stress is reduced. Additionally, the survival rate is high. However, the in vivo kinematics of MB UKA knees during high-flexion activities of daily living remain unknown. The aim of this study was to investigate in vivo the three-dimensional kinematics of MB UKA knees during high-flexion activities of daily living. A total of 17 knees of 17 patients who could achieve kneeling after MB UKA were examined. Under fluoroscopy, each patient performed squatting and kneeling motions. To estimate the spatial position and orientation of the knee, a two-dimensional/three-dimensional registration technique was used. We evaluated the femoral rotation and varus-valgus angle relative to the tibia and the anteroposterior translation of the medial sulcus (medial side) and lateral epicondyle (lateral side) of the femur on the plane perpendicular to the tibial mechanical axis in each flexion angle. From 130° to 140° of flexion, the femoral external rotation during squatting was significantly smaller than that during kneeling. Additionally, the medial side of the femur during squatting was significantly more posteriorly located compared with that during kneeling. There was no significant difference between squatting and kneeling in terms of the lateral side of the femur and the varus-valgus position in each flexion angle. At high flexion angle, the kinematics of MB UKA knees may differ depending on the performance., Competing Interests: None declared., (Thieme. All rights reserved.)

The effect of osteotomy type on the initial stiffness of the bone-implant construct in lateral opening-wedge distal femoral osteotomy (LOWDFO) using a uniplanar compared with a biplanar technique has been investigated. However, no study has explored the biomechanical risk factors for medial hinge fracture. This study aimed to compare the biomechanical strength of uniplanar versus biplanar LOWDFO regarding the risk for medial hinge fracture during gap opening. Twelve composite femora were divided into two groups (six in each group) based on the distal femoral osteotomy technique: uniplanar versus biplanar LOWDFO. All LOWDFO models were subjected to incremental static loading. The gap distance was expanded by 1 mm, and displacement values were recorded as anterior and posterior gap distances (mm) . The average force values of all samples at certain gap distances were recorded, and the head distance was measured. The uniplanar group had higher load values than the biplanar group at all anterior gap distances. These differences were only significant at 2- and 3-mm gap distances ( p  = 0.025 and 0.037). At all posterior gap distances, the uniplanar group had higher load values than the biplanar group, but these differences only reached statistical significance at 2 mm ( p  = 0.037). Both groups had similar anterior, posterior, and average gap distances ( p  = 0.75, 0.522, 0.873). The uniplanar group had a higher head insertion distance (15.3 ± 5.7) than the biplanar group (14.7 ± 2.9), but it was not significant ( p  = 0.87). The uniplanar group had a lower average load before medial hinge fracture (46.41 ± 13.91 N) than the biplanar group (54.92 ± 31.94, p  = 0.81). The biplanar group had an average maximum load value of 64.18 ± 25.6 N, while the uniplanar group had 57.90 ± 12.21 N ( p  = 0.81). This study revealed that the biplanar osteotomy technique allows a wider opening wedge gap with less risk of a medial hinge fracture than uniplanar LOWDFO.Level of evidence was level 3, case-control series., Competing Interests: None declared., (Thieme. All rights reserved.)

The purpose of this study was to reveal the correlation between anteromedial (AM) and posterolateral (PL) femoral tunnel lengths in anatomical double-bundle anterior cruciate ligament (ACL) reconstruction and body size and knee morphology. Thirty-four subjects undergoing anatomical double-bundle ACL reconstruction were included in this study. Preoperative body size (height, body weight, and body mass index) was measured. Using preoperative magnetic resonance imaging (MRI), quadriceps tendon thickness and the whole anterior-posterior length of the knee were measured. Using postoperative computed tomography (CT), axial and sagittal views of the femoral condyle were evaluated. The correlation between measured intraoperative AM and PL femoral tunnel lengths, and body size and knee morphology using preoperative MRI and postoperative CT parameters was statistically analyzed. Both AM and PL femoral tunnel lengths were significantly correlated with height, body weight, posterior condylar length, and Blumensaat's line length. These results suggest that the femoral ACL tunnel length created using a transportal technique can be estimated preoperatively by measuring the subject's body size and/or the knee morphology using MRI or CT. For clinical relevance, surgeons should be careful to create femoral tunnel of sufficient length when using a transportal technique, especially in knees of subjects with smaller body size and knee morphology. Level of evidence is III., Competing Interests: None declared., (Thieme. All rights reserved.)

The conventional approach for total knee arthroplasty (TKA) is a medial parapatellar approach (MPA). We aimed to study patient outcomes and kinematics with a quadriceps sparing lateral subvastus lateralis approach (SLA). Patients with neutral/varus alignment undergoing primary TKA were consented to undergo the SLA. At 1-year postoperative, patients underwent radiostereometric analysis. Patients were administered the Short Form 12 (SF-12), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Knee Society Score (KSS). Kinematics and outcome data were compared to a group undergoing TKA via conventional MPA. Fourteen patients underwent TKA via SLA with a mean age 71.5 ± 8.0 and mean body mass index (BMI) 31.0 ± 4.5. The MPA group had 13 patients with mean age 63.4 ± 5.5 ( p  = 0.006) and mean BMI 31.2 ± 4.6 ( p  = 0.95). The SLA resulted in a significantly more posterior medial contact point at 0 ( p  = 0.011), 20 ( p  = 0.020), and 40 ( p  = 0.039) degrees of flexion. There was no significant difference in medial contact point from 60 to 120 degrees, lateral contact point at any degree of flexion, or axial rotation. There was no difference in improvement in postoperative WOMAC, SF-12, KSS function, and total KSS knee scores between groups. The MPA group had a significantly greater improvement in KSS knee scores at 3 months ( p  < 0.001), 1 year ( p  = 0.003), and 2 years ( p  = 0.017). The SLA resulted in increased medial femoral rollback early in flexion. Although both approaches resulted in improved postoperative outcomes, the MPA group showed significantly greater improvements in KSS knee scores at 3 months, 1 year, and 2 years. Further studies are required to identify any benefits that the SLA may offer. LEVEL OF EVIDENCE:  Therapeutic Level II., Competing Interests: None declared., (Thieme. All rights reserved.)

The alignment philosophy in total knee arthroplasty (TKA) has tended to shift from the gold standard of mechanically aligned technique to personalized alignment, such as the kinematically aligned (KA) technique. However, the influences of different surgical techniques on lower limb alignment relative to the ground are not fully investigated. This study investigated the influence of the ankle and hindlimb alignment change after mechanically aligned TKA and KA-TKA. The varus osteoarthritic patients who underwent TKAs were divided into a mechanically aligned TKA group (group M, n  = 50) and a KA-TKA group (group K, n  = 50). Radiographic parameters (hip-knee-calcaneus [HKC] angle, hip-knee-ankle [HKA] angle, talar tilt angle [TTA], and tibiocalcaneal angle [TCA]) were investigated using full-length standing radiographs. The deviation angle (ΔTA; angle between the tibial mechanical axis [TMA] and the ground tibial mechanical axis [gTMA]) and the change of ΔTA (cΔTA) were also assessed. These parameters were compared between the two groups, along with the correlation between the preoperative HKA angle and other parameters. ΔTA, TTA, and TCA showed no differences between the groups pre- and postoperatively, and no significant changes were observed postoperatively. The preoperative HKA angle showed a significant negative correlation with cΔTA in both groups (group M: r  = -0.33, p  = 0.02; group K: r  = -0.29, p  = 0.04) although no correlation was observed the with preoperative TTA and TCA. Despite no change in ΔTA after surgery, the preoperative varus deformity was associated with a change in the deviation between gTMA and TMA after surgery. A severely varus knee may be inappropriate for ground KA-TKA., Competing Interests: None declared., (Thieme. All rights reserved.)

The annual demand for knee arthroplasty has been steadily rising, particularly in younger patients. The primary objective of this systematic review was to determine the impact of knee arthroplasties on knee function and activity levels in young (≤55 years) patients. A PubMed search from inception (1977) to March 2022 to identify eligible studies produced 640 peer-reviewed studies for consideration. A total of 18 studies including 4,186 knee arthroplasties in 3,200 patients (mean patient age at the time of surgery: 47.4 years, range: 18-55 years) were ultimately included for analysis. Mean final follow-up (FFU) duration was 5.8 years (range: 2-25.1 years). Mean FFU improvement in Knee Society Clinical Score was 48.0 (1,625 knees, range: 20.9-69.0), Knee Society Function Score was 37.4 (1,284 knees, range: 20-65). Mean FFU for the Tegner and Lysholm activity scale was 2.8 (4 studies, 548 knees, range: 0.7-4.2); University of California Los Angeles Physical Activity Questionnaire score was 2.8 (3 studies, 387 knees, range: 1.2-5); lower extremity activity scale was 1.84 (529 knees). The available evidence suggest that young patients typically realize sustained improvements in knee function compared to preoperative levels; however, these improvements do not typically translate into a return to desired activity levels or quality of life, and this patient population should expect a higher and earlier risk for revision than their older counterparts. Further research, including robust registry data, is needed to establish evidence-based indications, expectations, and prognoses for outcomes after knee arthroplasty in young and active patients., Competing Interests: C. W. N. is a board or committee member for AAOS; is a board or committee member for American Orthopaedic Society for Sports Medicine; receives other financial or material support from AO Foundation; is a paid presenter or speaker for Arthrex, Inc; is on the editorial or governing board, receives publishing royalties, financial or material support from Arthroscopy; is a board or committee member for Arthroscopy Association of North America; is a paid consultant for Guidepoint Consulting; and is a paid presenter or speaker for Vericel, Inc.J. P. S. is a board or committee member for American Orthopaedic Association; is a board or committee member for AO Foundation; is a board or committee member for AO North America; is a paid consultant and receives research support from Arthrex, Inc; is a paid consultant for DePuy, A Johnson & Johnson Company; is on the editorial or governing board (Editor-in-Chief) for the Journal of Knee Surgery; is a board or committee member for Mid-America Orthopaedic Association; receives research support from National Institutes of Health (NIAMS & NICHD); is a paid consultant for Orthopedic Designs North America; is a paid consultant for Smith & Nephew; receives publishing royalties, financial or material support from Thieme; receives research support from U.S. Department of Defense.J. L C. receives research support from AO Trauma; receives IP royalties, is a paid consultant and receives research support from Arthrex, Inc; receives research support from Collagen Matrix Inc; receives research support from DePuy, A Johnson & Johnson Company; is on the editorial or governing board (Associate Editor) for the Journal of Knee Surgery; is a board or committee member for Midwest Transplant Network; is a board or committee member, receives IP royalties and research support from Musculoskeletal Transplant Foundation; receives research support from National Institutes of Health (NIAMS & NICHD); receives research support from Orthopaedic Trauma Association; receives research support from Purina; receives research support from Regenosine; receives research support from SITES Medical; receives publishing royalties, financial or material support from Thieme; is a paid consultant for Trupanion and receives research support from U.S. Department of Defense., (Thieme. All rights reserved.)

This study aimed to determine whether there was a relationship between preoperative patient-reported outcome measures (PROMs) and satisfaction after total knee arthroplasty (TKA), and whether there was a relationship between the amount of improvement in PROM or final PROM and satisfaction and whether that relationship differed 1 and 2 years after TKA. The Western Ontario and McMaster University Osteoarthritis Index (WOMAC) and satisfaction of 267 limbs who underwent TKA were analyzed. Logistic regression analysis was performed to determine whether there was a relationship between preoperative WOMAC or improvement in WOMAC or final WOMAC and satisfaction at 1 and 2 years after TKA. Pearson and Filon's z test was performed to determine whether there was a difference in evaluating satisfaction between the amount of improvement in WOMAC and final WOMAC. There was no significant relationship between preoperative WOMAC and satisfaction. A higher improvement in WOMAC total score and better final WOMAC total scores at 1 and 2 years after TKA were related to greater satisfaction. At 1 year after TKA, there was no significant difference in evaluating satisfaction between the amount of improvement in WOMAC and final WOMAC. However, 2 years after TKA, the final WOMAC function and total score were more related to satisfaction than the amount of improvement in WOMAC function and total score. In the early postoperative period, there was no difference in evaluating satisfaction between the amount of improvement in WOMAC and final WOMAC, whereas over time, the final WOMAC was more related to satisfaction., Competing Interests: None declared., (Thieme. All rights reserved.)

The purpose of this study was to reveal the correlation and proportion between the anterior cruciate ligament (ACL) cross-sectional area and the femoral intercondylar notch area. Sixty-three subjects (33 female and 30 male) less than 50 years old were included in this study. All subjects complained of knee pain, although magnetic resonance imaging (MRI) showed no structural damage of the knee. Using the T2 axial slice of the MRI perpendicular to the bone shaft, the ACL cross-sectional area and the femoral intercondylar notch area were measured. Measurements were made at the most proximal (S1), ⅓ (S2), ⅔ (S3), and the most distal (S4) Blumensaat's line levels. The correlation and the proportion between the ACL cross-sectional area and the notch area were calculated. The ACL cross-sectional area was: S1: 35.9 ± 10mm 2 , S2: 59.9 ± 14mm 2 , S3: 67.2 ± 19.5mm 2 , and S4: 70.7 ± 20.3mm 2 . The notch area was: S1: 215.5 ± 43mm 2 , S2: 311.8 ± 65mm 2 , S3: 453.8 ± 86mm 2 , and S4: 503.7 ± 99.8mm 2 . The ACL cross-sectional area and the notch area were found to be significantly correlated at the S3 (Pearson's coefficient correlation: 0.510, p  = 0.000) and S4 (Pearson's coefficient correlation: 0.529, p  = 0.000) levels. The proportion of the ACL cross-sectional area to the notch area was 15% in S3 and 14% in S4. The ACL cross-sectional area was found to be significantly correlated with the femoral intercondylar notch area at the distal level of the Blumensaat's line. The ACL cross-sectional area was found to be approximately 15% of the notch area. The ACL cross-sectional area can be predicted by measuring the femoral intercondylar notch area. This finding can be useful for achieving greater accuracy in anatomical ACL reconstruction. LEVEL OF EVIDENCE:  III., Competing Interests: None declared., (Thieme. All rights reserved.)

Untreated osteoarthritis (OA)-related bone marrow lesions (OA-BML) can hasten the progression of knee OA. Previous studies have shown that fluoroscopically guided intraosseous calcium-phosphate (CaP) injections of OA-BML during knee arthroscopy can lead to pain reduction, improved functionality, and prolonged time until conversion to total knee arthroplasty (TKA). The purpose of this retrospective study is to compare the clinical outcomes of patients who underwent knee arthroscopy and CaP injection for OA-BML versus knee arthroscopy for non-OA-BML pathologies. Two-year follow-up data and patient-reported outcomes including knee injury and operative outcome scores, joint replacement scores (KOOS, JR) were available for 53 patients in the CaP group and 30 patients in the knee arthroscopy group. Results indicate that patients in the CaP group had less frequent conversion to TKA compared with patients in the knee arthroscopy group. Statistical analysis demonstrated a statistical difference between preoperative and postoperative KOOS, JR within the CaP group but not for the knee arthroscopy group. Two-year postoperative KOOS, JR for CaP patients was statistically greater than the 2-year postoperative KOOS, JR of knee arthroscopy patients. Results indicate greater improvement in functional outcomes with knee arthroscopy and CaP injection of OA-BML compared with knee arthroscopy alone for non-OA-BML diagnoses. The results of this retrospective study help to distinguish the benefits of knee arthroscopy accompanied by CaP intraosseous injection from that of knee arthroscopy alone., Competing Interests: None declared., (Thieme. All rights reserved.)

Early results with robotic-arm-assisted total knee arthroplasty (TKA) are encouraging; nevertheless, literature might be unrepresentative, as it comes mostly from American, European, and Asian countries. There is limited experience and no comparative clinical reports in Latin America, a region of mainly low- and middle-income countries with limited access to these promising technologies. This study aims to compare the early postoperative results of the first Latin American experience with robotic-arm-assisted TKA versus conventional TKA. A cohort study was performed, including 181 consecutive patients (195 knees) with advanced symptomatic knee osteoarthritis (OA) undergoing primary TKA between March 2016 and October 2019. The cohort included 111 consecutive patients (123 knees) undergoing conventional TKA, followed by 70 consecutive patients (72 knees) undergoing robotic-arm-assisted TKA. The same surgical team (surgeon 1 and surgeon 2) performed all procedures. Patients with previous osteotomy, posttraumatic OA, and revision components were not considered. The same anesthetic and rehabilitation protocol was followed. The investigated clinical outcomes (for the first 60 postoperative days) were: surgical tourniquet time, time to home discharge, time to ambulation, postoperative daily pain (Visual Analog Scale), opioid use, range of motion, blood loss, complications, and postoperative mechanical axis. The early clinical postoperative results of this first Latin American comparative experience of robotic-arm-assisted TKA versus conventional technique showed lower opioids requirements and faster functional recovery of ambulation in those patients operated with the robotic system; nevertheless, surgical times were higher, without differences in total postoperative complications and other clinical outcomes., Competing Interests: D.F. reports personal fees from Stryker, Smith and Nephew, and Conmed, outside the submitted work; and he is a Director of Revista Chilena de Ortopedia y Traumatologia, member of the Editorial Board of the Journal of ISAKOS, Consultant of Revista de Artroscopia, and Board Directors of ISAKOS. A.V. reports personal fees from Arthrex, outside the submitted work; and he is an Editorial member of Revista Chilena de Ortopedia y Traumatologia and Orthopaedic Journal of Sports Medicine, and President of the Board Directors of Sociedad Chilena de Ortopedia y Traumartologia. R.C. reports personal fees from Stryker, Smith and Nephew, outside the submitted work; and he is an Editorial member of Revista Chilena de Ortopedia y Traumatoligia and Revista Artroscopia SLARD., (Thieme. All rights reserved.)

A portable accelerometer-based navigation system can be useful for achieving the target alignment. Tibial registration is based on the medial and lateral malleoli; however, the identification of landmarks may be difficult in obese (body mass index [BMI] >30 kg/m 2 ) patients whose bones are not easily palpable from the body surface. This study compared tibial component alignment achieved using a portable accelerometer-based navigation system (Knee Align 2 [KA2]) in obese and control groups and aimed to validate the accuracy of bone cutting in obese patients. A total of 210 knees that underwent primary total knee arthroplasty using the KA2 system were included. After 1:3 propensity score matching, there were 32 and 96 knees in the BMI >30 group (group O) and BMI ≤30 group (group C), respectively. The absolute deviations of the tibial implant from the intended alignment were evaluated in the coronal plane (hip-knee-ankle [HKA] angle and medial proximal tibial angle) and sagittal plane (posterior tibial slope [PTS]). The inlier rate of each cohort, which was defined as tibial component alignment within 2 degrees of the intended alignment, was investigated. In the coronal plane, the absolute deviations of the HKA and MPTA from the intended alignment were 2.2 ± 1.8 degrees and 1.8 ± 1.5 degrees in group C and 1.7 ± 1.5 degrees and 1.7 ± 1.0 degrees in group O ( p  = 1.26, and p  = 0.532). In the sagittal plane, the absolute deviations of the tibial implant were 1.6 ± 1.2 degrees in group C and 1.5 ± 1.1 degrees in group O ( p  = 0.570). The inlier rate was not significantly different between group C and group O (HKA: 64.6 vs. 71.9%, p  = 0.521; MPTA: 67.7 vs. 78.1%, p  = 0.372; PTS: 82.2 vs. 77.8%, p  = 0.667). The accuracy of tibial bone cutting for the obese group was comparable to that of the control group. An accelerometer-based portable navigation system can be useful when attempting to achieve the target tibial alignment in obese patients. LEVEL OF EVIDENCE:  Level IV., Competing Interests: None declared., (Thieme. All rights reserved.)

Intramedullary stems are often required in patients undergoing revision total knee arthroplasty (rTKA) to achieve stable fixation. Significant bone loss may require the addition of a metal cone to maximize fixation and osteointegration. The purpose of this study was to investigate clinical outcomes in rTKA using different fixation techniques. We conducted a single-institution retrospective review of all patients who received a tibial and femoral stem during rTKA between August 2011 and July 2021. Patients were separated into three cohorts based on fixation construct: press-fit stem with an offset coupler (OS), fully cemented straight (CS) stem, and press-fit straight (PFS) stem. A subanalysis of patients who received tibial cone augmentation was also conducted. A total of 358 patients who underwent rTKA were included in this study, of which 102 (28.5%) had a minimum 2-year follow-up and 25 (7.0%) had a minimum 5-year follow-up. In the primary analysis, 194 patients were included in the OS cohort, 72 in the CS cohort, and 92 in the PFS cohort. When stem type alone was considered, there was no significant difference in rerevision rate ( p  = 0.431) between cohorts. Subanalysis of patients who received augmentation with a tibial cone demonstrated that OS implants led to significantly higher rates of rerevision compared with the other two stem types (OS: 18.2% vs. CS: 2.1% vs. PFS: 11.1%; p  = 0.037). The findings of the present analysis demonstrate that CS and cones in rTKA may provide more reliable long-term outcomes compared with press-fit stems with OS. LEVEL III EVIDENCE:  Retrospective Cohort Study., Competing Interests: None declared., (Thieme. All rights reserved.)

A small posterior tibial slope (PTS) is generally recommended in posterior stabilized (PS) total knee arthroplasty (TKA). An unwanted anterior tibial slope (ATS), which can affect postoperative results, may be created in PS TKA because of the inaccuracy of surgical instruments and techniques, as well as high interpatient variability. We compared midterm clinical and radiographic results of PS TKAs with ATS and PTS performed on paired knees using the same prosthesis. One-hundred-twenty-four patients who underwent TKAs with ATS and PTS on paired knees using ATTUNE posterior-stabilized prostheses were retrospectively reviewed after a minimum follow-up period of 5 years. The mean follow-up period was 5.4 years. The Knee Society Knee and Function scores, Western Ontario and McMaster Universities Osteoarthritis Index, Feller and Kujalar scores, and range of motion (ROM) were evaluated. The preferred TKA out of ATS and PTS was also investigated. The hip-knee-ankle angle, component positions, tibial slope, posterior femoral offset, Insall-Salvati ratio, and knee sagittal angle were measured by radiography. There were no significant differences in the clinical results, including ROM, between TKAs with ATS and PTS preoperatively and at the last follow-up. Regarding patient preference, 58 patients (46.8%) were satisfied with bilateral knees, 30 (24.2%) preferred knees with ATS, and 36 (29%) preferred knees with PTS. There was no significant difference in the rate of preference between TKAs with ATS and PTS ( p  = 0.539). Except for the postoperative tibial slope (-1.8 vs. 2.5 degrees, p  < 0.001), there were also no significant differences in the radiographic results, including the knee sagittal angle, preoperatively and at the last follow-up. The midterm outcomes were similar between PS TKAs with ATS and PTS performed on paired knees at a minimum of 5 years of follow-up. Nonsevere ATS did not affect midterm outcomes in PS TKA with proper soft tissue balancing and the current prosthesis of improved design. However, a long-term follow-up study is required to confirm the safety of nonsevere ATS in PS TKA. LEVEL OF EVIDENCE::  III., Competing Interests: None declared., (Thieme. All rights reserved.)

Prior to unicompartmental knee arthroplasty (UKA), corticosteroid injections (CSI) are a common nonoperative treatment for arthritis. It is unclear whether CSI prior to UKA impacts the likelihood of postoperative infection. This study sought to determine if there is a time- and/or dose-dependent relationship between preoperative CSI and postoperative infection. An administrative claims database was queried for patients undergoing UKA with more than 1 year of pre-enrollment and follow-up. Of 31,676 patients with a UKA who met enrollment criteria, 8,628 patients had a CSI 0 to 3 months prior to surgery, 111 had a CSI 3 to 12 months prior to surgery, and 22,937 never received an injection. Overall, 246 postoperative deep infections were reported (0.8%). Time-dependent and dose-dependent relationships were modeled using multivariable logistic regressions. Postoperative deep infections occurred in 64 patients with CSI 0 to 3 months prior to surgery (0.7%), compared with 0 patients with CSI 3 to 12 months before surgery (0.0%) and 182 controls (0.8%, p  = 0.58). CSI within 1 month prior to UKA was not statistically associated with postoperative infection ( p  = 0.66). Two or more CSI within 3 months prior to UKA were associated with a twofold elevated odds of infection, compared with receiving a single injection (odds ratio [OR]: 2.08, p  = 0.03). Univariable predictors of infection included younger age, increasing Charlson Comorbidity Index, smoking, asthma, chronic obstructive pulmonary disease, chronic kidney disease, diabetes, liver disease, and obesity. Multivariable analysis controlling for these characteristics elicited no relationship between recent CSI administration and postoperative infection. CSI within 3 months of surgery (1.5%) or 3 to 12 months (1.8%) were associated with increased conversion to total knee arthroplasty (TKA) compared with those who did not receive an injection (1.1%, p  = 0.01), although TKA for indication of periprosthetic joint infection was not statistically different ( p  = 0.72). Preoperative CSI within 3 months of UKA is not associated with postoperative infection, although significant medical comorbidity does show an association. Preoperative CSI is associated with increased conversion from UKA to TKA for noninfectious indications., Competing Interests: None declared., (Thieme. All rights reserved.)

The effect of the posterior tibial slope (PTS) in cruciate-retaining total knee arthroplasty (CR-TKA) on clinical outcomes remains unclear. We aimed to investigate (1) the effect of alteration of the PTS on clinical outcomes, including patient satisfaction and joint awareness, and (2) the relationship between the patient-reported outcomes, the PTS, and compartment loading. Based on the alteration of the PTS after CR-TKA, 39 and 16 patients were stratified into increased and decreased PTS groups, respectively. Clinical evaluation was performed by the Knee Society Score (KSS) 2011 and the Forgotten Joint Score-12 (FJS-12). Compartment loading was intraoperatively assessed. KSS 2011 (symptoms, satisfaction, and total score) was significantly higher ( p  = 0.018, 0.023, and 0.040, respectively), and FJS ("climbing stairs?") was significantly lower ( p  = 0.025) in the increased PTS group compared with the decreased PTS group. The decrease in both medial and lateral compartment loading of Δ45°, Δ90°, and ΔFull was significantly greater in the increased PTS group than in the decreased PTS group ( p < 0.01 for both comparisons). Medial compartment loading of Δ45°, Δ90°, and ΔFull significantly correlated with KSS 2011 for "symptom" ( r  = - 0.4042, -0.4164, and -0.4010, respectively; p  = 0.0267, 0.0246, and 0.0311, respectively). ΔPTS significantly correlated with medial compartment loading differentials of Δ45°, Δ90°, and ΔFull ( r  = - 0.3288, -0.3792, and -0.4424, respectively; p  = 0.0358, 0.01558, and 0.0043, respectively). Patients with increased PTS showed better symptoms and higher patient satisfaction compared with those with decreased PTS following CR-TKA, possibly due to a greater decrease in compartment loading during knee flexion.Level of evidence:level IV, therapeutic case series., Competing Interests: None declared., (Thieme. All rights reserved.)

Bicruciate-retaining total knee arthroplasty (BCR TKA) results in kinematics closer to the native knee and in greater patient satisfaction but information concerning its outcome and complications is lacking.The goal of this study is to report the clinical and radiological outcomes of BCR prosthesis implanted using a spacer-based gap balancing technique and to assess if some preoperative factors are associated with a worse prognosis.A cohort of 207 knees in 194 patients who underwent BCR TKA, with a minimum 1-year follow-up, was retrospectively analyzed.Patients were followed at 6 weeks, 6 months, 1 year, and then every following year postoperatively, and filled questionnaires (Knee Society and Knee injury and Osteoarthritis Outcome Score) at every visit. Clinical and radiological assessments included range of motion, knee alignment, pain, and complications as defined by the Knee Society's Standardized list and definition of Complication of Total Knee Arthroplasty.Forty-three knees (20.8%) suffered major complications. Twenty-one knees (10.1%) underwent revision at an average of 32.1 months after the index procedure. Revision-free survival at 100 months was 85.7%. Revision was performed for aseptic tibial loosening in eight knees (3.9%) and stiffness in five knees (2.4%). There were 29 reoperations other than revision (14.0%), the most frequent procedure being manipulation under anesthesia in 14 knees (6.8%). Minor complications included tendonitis (20.8%), persistent synovitis (6.8%), and superficial wound infections (6.3%).All outcomes scores were greatly improved at the 1-year follow-up compared with preoperatively ( p  < 0.001). However, maximum flexion at the last follow-up was significantly reduced compared with preoperatively (mean maximum flexion ± standard deviation: 119.9 ± 15.6 vs. 129.9 ± 14.4, p  < 0.001). Aseptic tibial loosening was associated with a hypercorrection in varus of preoperative valgus knees ( p  = 0.012).BCR TKA can give functional results similar to other types of prostheses but involves a substantial risk of complications. Important factors that can explain failed BCR TKA and guide its use were identified, more particularly knee alignment and its role in aseptic tibial loosening., Competing Interests: None declared., (Thieme. All rights reserved.)

Osteochondral allograft (OCA) transplantation has been largely successful in treating symptomatic articular cartilage lesions; however, treatment failures persist. While OCA biomechanics have been consistently cited as mechanisms of treatment failure, the relationships among mechanical and biological variables that contribute to success after OCA transplantation have yet to be fully characterized. The purpose of this systematic review was to synthesize the clinically relevant peer-reviewed evidence targeting the biomechanics of OCAs and the impact on graft integration and functional survival toward developing and implementing strategies for improving patient outcomes. The Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, MEDLINE, PubMed, Cumulative Index to Nursing and Allied Health (CINAHL), Google Scholar, and EMBASE were searched to identify articles for systematic review. This review of relevant peer-reviewed literature provided evidence that the biomechanics related to OCA transplantation in the knee have direct and indirect effects on functional graft survival and patient outcomes. The evidence suggests that biomechanical variables can be optimized further to enhance benefits and mitigate detrimental effects. Each of these modifiable variables should be considered regarding indications, patient selection criteria, graft preservation methodology, graft preparation, transplantation, fixation techniques, and prescribed postoperative restriction and rehabilitation protocols. Criteria, methods, techniques, and protocols should target OCA quality (chondrocyte viability, extracellular matrix integrity, material properties), favorable patient and joint characteristics, rigid fixation with protected loading, and innovative ways to foster rapid and complete OCA cartilage and bone integration to optimize outcomes for OCA transplant patients., Competing Interests: T.M.G. is on the editorial or governing board for Advances in Biomechanics and Applications.J.P.S. is a board or committee member for American Orthopaedic Association; is a board or committee member for AO Foundation; is a board or committee member for AO North America; is a paid consultant and receives research support from Arthrex, Inc; is a paid consultant for DePuy, a Johnson & Johnson Company; is on the editorial or governing board of the Journal of Knee Surgery; is a board or committee member for Mid-America Orthopaedic Association; receives research support from the National Institutes of Health (NIAMS & NICHD); is a paid consultant for Orthopedic Designs North America; is a paid consultant for Smith & Nephew; receives publishing royalties, financial or material support from Thieme and receives research support from U.S. Department of Defense.J.L.C. receives research support from AO Trauma; receives IP royalties, is a paid consultant and receives research support from Arthrex, Inc; receives research support from Collagen Matrix Inc; receives research support from DePuy, a Johnson & Johnson Company; is on the editorial or governing board of Journal of Knee Surgery; is a board or committee member for Midwest Transplant Network; is a board or committee member, receives IP royalties and research support from Musculoskeletal Transplant Foundation; receives research support from National Institutes of Health (NIAMS & NICHD); receives research support from Orthopaedic Trauma Association; receives research support from Purina; receives research support Regenosine; receives research support from SITES Medical; receives publishing royalties, financial or material support from Thieme; is a paid consultant for Trupanion; and receives research support from U.S. Department of Defense., (Thieme. All rights reserved.)

Clinical and radiographic characteristics of mucoid degeneration of the anterior cruciate ligament (MD-ACL) were poorly documented in previous literature. And the optimal management strategy for MD-ACL remains unclear. Here, we summarized the characteristics associated with MD-ACL, and evaluated the clinical outcome of conservative management to MD-ACL.A total of 18 knees in 18 patients diagnosed with MD-ACL were collected and reviewed retrospectively. Sixteen patients underwent conservative management and two patients underwent arthroscopic surgery. Baseline demographic, clinical data, and pathologic changes of knee in magnetic resonance imaging (MRI) were recorded. Clinical outcome was evaluated with Visual Analogue Scale (VAS) and Oxford Knee Score (OKS).The most common clinical characteristic in patients with MD-ACL was knee pain (18/18), and seconded by mobility limitation (38.9%, 7/18). All patients presented a typical celery stalk sign with increased signal and diffuse thickening volume in the ACL in MRI. Thirteen patients companied with meniscus tear (72.2%, 13/18), and nine complicated with cartilage injury (50.0%, 9/18). Sixteen patients who underwent conservative treatment were followed up for 21.8 months, and a positive clinical outcome was observed with VAS decreasing from 5.3 ± 2.3 to 1.5 ± 1.9 and OKS decreasing from 27.5 ± 12.7 to 17.9 ± 11.8 ( p  < 0.001). The post-OKS score was highly correlated with age, duration of disease, and meniscus tear ( r  = 0.844, 0.707, and 0.474, p  < 0.05, respectively). And the post-VAS highly correlated with age ( r  = 0.693, p  < 0.05). Two patients who underwent arthroscopic surgery were followed up for 24.5 months, and the pain and function of knee was improved.Knee pain and meniscus tear was the main characteristic of MD-ACL in clinical and radiographic exam. Conservative treatment could be an alternative management for treatment of MD-ACL with positive clinical outcome. Old age, long duration of disease and complications from meniscus tears were associated with inferior outcome of conservative treatment for MD-ACL. LEVEL OF EVIDENCE:  IV., Competing Interests: None declared., (Thieme. All rights reserved.)

Surgical reconstruction is recommended for symptomatic posterior cruciate ligament (PCL) deficiency. While anatomic double-bundle PCL reconstruction (PCLR) has been reported to be associated with biomechanical and clinical advantages over other methods, there is still debate regarding the optimal technique for tibial positioning and fixation. Based on reported advantages and disadvantages, we employed two tibial fixation techniques, transtibial (TT) and tibial inlay (TI) for anatomic double-bundle PCLR with technique selection based on body mass index, comorbidities, and primary versus revision surgery. This study aimed to compare clinical outcomes following PCLR utilizing either TT or TI techniques to validate relative advantages, disadvantages, and indications for each based on the review of prospectively collected registry data. For 37 patients meeting inclusion criteria, 26 underwent arthroscopic TT PCLR using all-soft- tissue allograft with suspensory fixation in the tibia and 11 patients underwent open TI PCLR using an allograft with calcaneal bone block and screw fixation in the tibia. There were no significant preoperative differences between cohorts. Success rates were 96% for TT and 91% for TI with all successful cases documented to be associated with good-to-excellent posterior stability and range of motion in the knee at the final follow-up. In addition, patient-reported outcome scores were within clinically meaningful ranges for pain, function, and mental health after PCLR in both cohorts, suggesting similarly favorable functional, social, and psychological outcomes. Patient-reported pain scores at 6 months postoperatively were significantly ( p  = 0.042) lower in the TT cohort, which was the only statistically significant difference in outcomes noted. The results of this study support the use of TT and TI techniques for double-bundle anatomic PCLR in restoring knee stability and patient function when used for the treatment of isolated and multiligamentous PCL injuries. The choice between tibial fixation methods for PCLR can be appropriately based on patient and injury characteristics that optimize respective advantages for each technique., Competing Interests: • J.L.C. received research support from AO Trauma, received IP royalties and is a paid consultant for Arthrex, Inc; received research support from Collagen Matrix Inc; received research support from DePuy, A Johnson & Johnson Company; is on the editorial or governing board of the Journal of Knee Surgery; is a board or committee member for Midwest Transplant Network; is a board or committee member; received IP royalties and research support from Musculoskeletal Transplant Foundation; received research support from National Institutes of Health (NIAMS & NICHD); received research support from Orthopaedic Trauma Association; received research support from Purina; received research support from Regenosine; received research support from SITES Medical; received publishing royalties, financial, or material support from Thieme; is a paid consultant for Trupanion; and received research support from the U.S. Department of Defense.• J.P.S. is a board or committee member for the American Orthopaedic Association; is a board or committee member for AO Foundation; is a board or committee member for AO North America; is a paid consultant and receives research support from Arthrex, Inc; is a paid consultant for DePuy, A Johnson & Johnson Company; is on the editorial or governing board for the Journal of Knee Surgery; is a board or committee member for Mid-America Orthopaedic Association; receives research support from the National Institutes of Health (NIAMS & NICHD); is a paid consultant for Orthopedic Designs North America; is a paid consultant for Smith & Nephew; received publishing royalties, financial or material support from Thieme and received research support from the U.S. Department of Defense.• J.T., K.R., A.M., and J.B.deA. II declare no conflict of interest., (Thieme. All rights reserved.)

Several combined procedures have been reported for treating recurrent patellofemoral instability (RPI) with various types and severity of morphological abnormalities, but none have identified absolute threshold values as indications for surgery. We performed medial patellofemoral ligament (MPFL) reconstruction combined with a modified Elmslie-Trillat (ET) procedure on 24 knees (10 male and 11 female patients) to treat RPI with morphological abnormalities corresponding to elevated tibial tubercle-trochlear groove (TT-TG) distance, significant patella alta, and trochlear dysplasia. The inclusion criteria were RPI with morphological abnormalities corresponding to one or more of the following: sulcus angle > 160 degrees, trochlear dysplasia of Dejour classification C or D, Caton-Deschamps index > 1.5, lateral shift ratio > 50%, congruence angle > 15 degrees, or TT-TG distance > 20 mm, including habitual dislocation of the patella. Skeletally immature patients and those with congenital dislocation of the patella were excluded. The Kujala score, International Knee Documentation Committee subjective score, Knee Injury and Osteoarthritis Outcome score (KOOS), and each item of the KOOS improved significantly after surgery. Patellar apprehension sign was present preoperatively in all cases, but all disappeared postoperatively. No instance of postoperative redislocation was observed. On radiographic examination, the mean Q angle, tilting angle, lateral shift ratio, congruence angle, Caton-Deschamps index, Insall-Salvati index, and TT-TG distance improved significantly after surgery. There were no significant differences in sulcus angle after surgery. These results suggest MPFL reconstruction combined with a modified ET procedure provides satisfactory outcomes based on radiological and clinical evaluations for RPI with morphological abnormalities corresponding to elevated TT-TG distance, significant patella alta, and trochlear dysplasia., Competing Interests: M.S. reports grants from Japan Agency for Medical Research and Development and personal fees from CellSeed, Inc., outside the submitted work., (Thieme. All rights reserved.)

Many studies have compared outcomes in total knee arthroplasty (TKA) versus unicompartmental knee arthroplasty (UKA); however, to the authors' knowledge, there is no study evaluating complication rates in patients with significant comorbidities. The purpose of this retrospective study was to compare the incidence of postoperative complications, readmission and reoperation rates, length of stay (LOS), and discharge location for patients with significant medical comorbidities undergoing TKA versus UKA. Using the NSQIP database from 2008 to 2018, patients were identified by CPT code (27447 or 27446) and admission diagnostic code of primary osteoarthritis and included in the study if they had an American Society of Anesthesia score greater than or equal to 3. Chi-square test was used to compare categorical variables and t -test for continuous variables. Multivariate regression was used to compare outcomes of interest between groups. A total of 167,054 patients were analyzed with 97.3% undergoing TKA. TKA patients had a greater overall complication rate than those undergoing UKA ( p  < 0.001). Readmission rates were approximately 1.5 times higher in TKA compared with UKA ( p  = 0.002), while no statistically significant difference was discovered in reoperation rates ( p  = 0.868). TKA was also associated with decreased rates of same day discharge, discharge within 24 hours of surgery, and discharge home ( p  < 0.001, <0.001, and <0.001, respectively). This study found an increase in complication rates, readmission rates, and LOS, along with a lower likelihood of discharge home when undergoing a TKA. These findings suggest that patients with significant medical comorbidities at baseline may benefit from UKA over TKA when anatomically indicated., Competing Interests: None declared., (Thieme. All rights reserved.)

Restoring sagittal alignment in kinematically aligned (KA) total knee arthroplasty (TKA) is crucial to avoid patellofemoral joint instability or overstuffing and to restore an adequate range of motion. This prospective study compared the accuracy of conventional instrumentation (CI) versus patient-specific instrumentation (PSI) in restoring sagittal alignment of KA TKA measured by the tibial slope and degree of flexion of the femoral component to the sagittal femoral axis. One hundred patients were randomized to receive either CI ( n  = 50) or PSI ( n  = 50) for KA TKA. Two observers measured pre- and postoperative X-rays to assess restoration of the tibial slope and sagittal flexion. Inter- and intraclass correlations were calculated, and postoperative tibial and femoral components were compared with preoperative anatomy. In 50 CI patients, 86% ( n  = 43) had the tibial slope restored exactly, and no deviation more than 1 degree was found. Deviations of 0 to 1 degree were detected in 14% ( n  = 7). In 50 patients of the PSI group, 56% ( n  = 28) achieved an exact anatomic tibial slope restoration and 20% ( n  = 10) showed a deviation more than 2 degrees compared with the preoperative measurement. Deviations ranging between 0 to 1 and 1 to 2 degrees were found in 22% ( n  = 11) and 2% ( n  = 1) of cases, respectively. Sagittal alignment of the femoral component showed in both groups no deviation exceeding 1 degree. The restoration of sagittal alignment in KA TKA was statistically significantly differently distributed between CI and PSI ( p  = < 0.001) without clinical relevance. We found that PSI increased the odds for deviations >2 degrees in tibial slope reconstructions from 0 to 0.20 ([95% confidence interval: 0.09-0.31]; p  = 0.001). Both CI and PSI revealed adequate results with respect to restoring sagittal alignment of the tibial and femoral components in KA TKA. The conventional technique requires adequate adjustment of the intramedullary rod to avoid hyperflexion of the femoral component and attention must be paid when restoring the tibial slope using PSI. This is a prospective Level II study., Competing Interests: None declared., (Thieme. All rights reserved.)

Robotic-assisted surgery (RAS) in total knee arthroplasty (TKA) is becoming popular due to better precision, when compared with other instrumentation. Although RAS has been validated in comparison with computer-assisted surgery (CAS), data from clinical settings comparing these two techniques are lacking. This is especially the case for sagittal alignment. Whereas pure mechanical alignment (MA) aims for 0 to 3 degrees of flexion of the femoral component and 3° of posterior slope for the tibial component, adjusted MA (aMA) mostly used with RAS allows for flexing of the femoral component for downsizing and increase of slope for an increase of the flexion gap. In the present study, we compared sagittal alignment after TKA using RAS with aMA and CAS targeting MA, which has been the standard in the center for more than 10 years. We analyzed a prospectively collected database of patients undergoing TKA in a single center. Femoral component flexion and tibial slope were compared for both techniques. In 140 patients, 68 CAS and 72 RAS, we found no difference in tibial slope ( p  = 0.661), 1° median femoral component flexion ( p  = 0.023), and no difference in outliers (femur, p  = 0.276, tibia, p  = 0.289). RAS slightly increases femoral component flexion, but has no influence on tibial slope, when compared with CAS in TKA. If MA is the target, RAS provides no benefit over CAS for achieving the targeted sagittal alignment. LEVEL OF EVIDENCE:  Level III retrospective study., Competing Interests: None declared., (Thieme. All rights reserved.)

Competing Interests: Disclosure The authors report no conflicts of interest in this work.

Varus knee deformity is one of the most common deformities presenting for total knee arthroplasty (TKA). When present, a varus knee deformity contributes to overload of the medial joint compartment during gait, leading to increased medial compartment forces as well as lateral soft tissue lengthening. Additionally, a fixed varus deformity is associated with medial soft tissue contractures of the deep and superficial medial collateral ligament (MCL) and posteromedial capsule. With a fixed varus deformity, soft tissue releases may be necessary to create equivalent and rectangular flexion and extension gaps. There may also be anteromedial tibial bone defects, medial femoral condyle defects, and occasionally flexion contractures, especially in more severe cases. In cases of severe varus deformity with medial tibial bone loss, bone defects must be addressed to ensure adequate implant support. In many cases, a primary knee implant can be utilized in cases of varus knee deformity, but occasionally prostheses with higher levels of constraint may be required to balance and stabilize the knee. TKA has had a successful track record, with high levels of long-term implant survivorship even in cases of severe varus. Iatrogenic MCL instability and tibial aseptic loosening are complications associated with TKA in cases of severe varus, and multiple methods to avoid complications are presented here., Competing Interests: None declared., (Thieme. All rights reserved.)

Historically, anterior referencing and posterior referencing are two specific techniques that surgeons can use for proper sizing of the femoral component in total knee arthroplasty (TKA). In this review, we introduce the concept of "anatomic referencing" which has become useful with more incremental sizes of the femoral component to more perfectly match the native anatomy of each patient and reduce overstuffing of the patellofemoral joint and medial-lateral (ML) overhang. Fifty consecutive TKA cases were reviewed where the novel anatomic referencing technique was used. Lateral radiographic projections were obtained preoperatively and postoperatively. The posterior condylar offset (PCO) was evaluated on the lateral radiographs by measuring the distance between the tangent line of the femoral diaphysis posterior cortex and the posterior condylar margin. PCO ratio (PCOR) was calculated by dividing the PCO by the distance between the posterior condylar border and a tangent line along the anterior cortex of the femoral diaphysis. Forty-five patients (50 TKAs) were reviewed. Average age of the patients was 70.34, range: 47-91. There were 19 males and 26 females reviewed in this series. On average, the delta PCOR was 0.022 (standard deviation = 0.032; min: -0.049, max: 0.082). When grouping our results into three main groups: < -0.03, -0.03 to 0.03, and > 0.03, we found that 62% fell within the -0.03 to 0.03 range. There was no statistically significant difference in delta PCOR between standard and narrow implants ( p  = 0.418). The proposed novel anatomic referencing technique has allowed for proper sizing of patients' femurs in the anteroposterior and ML direction while avoiding component overhang or the need for component downsizing to obtain a proper ML fit. This radiographic review confirmed this to be a highly accurate and reproducible technique., Competing Interests: None declared., (Thieme. All rights reserved.)

Subchondral insufficiency fractures of the knee (SIFK) can result in high rates of osteoarthritis and arthroplasty. The implantable shock absorber (ISA) implant is a titanium and polycarbonate urethane device which reduces the load on the medial compartment of the knee by acting as an extra-articular load absorber while preserving the joint itself. The purpose of this study was to evaluate whether partially unloading the knee with the ISA altered the likelihood of progression to arthroplasty utilizing a validated predictive risk model (SIFK score). A retrospective case-control (2:1) study was performed on patients with SIFK without any previous surgery and on those implanted with the ISA with the primary outcome being progression to arthroplasty compared with nonoperative treatment at 2 years. Baseline and final radiographs, as well as magnetic resonance imagings, were reviewed for the evaluation of meniscus or ligament injuries, insufficiency fractures, and subchondral edema. Patients from a prospective study were matched using the exact SIFK Score, a validated predictive score for progression to arthroplasty in patients with SIFK, to those who received the ISA implant. Kaplan-Meier analysis was conducted to assess survival. A total of 57 patients (38 controls:19 ISA) with a mean age of 60.6 years and 54% female were included. The SIFK score was matched exactly between cases and controls for all patients. The 2-year survival rate of 100% for the ISA group was significantly higher than the corresponding rate of 61% for the control group ( p  < 0.01). In ISA, 0% of the patients converted to arthroplasty at 2 years, and 5% (one patient) had hardware removal at 1 year. When stratified by risk, the ISA group did not have a significantly higher survival compared with low-risk ( p  = 0.3) or medium-risk ( p  = 0.2) controls, though it had a significantly higher survival for high-risk groups at 2 years (100 vs. 15%, p  < 0.01). SIFK of the medial knee can lead to significant functional limitation and high rates of conversion to arthroplasty. Implants such as the ISA have the potential to alter the progression to arthroplasty in these patients, especially those at high risk., Competing Interests: None declared., (Thieme. All rights reserved.)

In restricted kinematic alignment total knee arthroplasty (TKA), bone resection is performed within a safe range to help protect against failure from extreme alignments. Patient-specific instrumentation, navigations, and robotics are often required for restricting bone cuts within a specified safe zone. We hypothesized that the lateral malleolus could be used as a landmark for restricting the tibial osteotomy using a mechanical jig. Here, we examine its feasibility in anatomical and clinical settings. We studied long-leg standing radiographs of 114 consecutive patients (228 knees) who underwent knee arthroplasty in our institution. We measured the lateral malleolus angle (LMA), the angle between the tibial axis and the line between the center of the knee and the lateral surface of the lateral malleolus. The medial proximal tibial angle was also measured before and after restricted kinematic alignment TKA under restriction with reference to the lateral malleolus. Mean LMA was 5.5 ± 0.5 degrees. This was relatively consistent and independent of patient's height, weight, and body mass index. The lateral malleolus is a reliable bone landmark that can be used to recognize approximately 5.5 degrees of varus intraoperatively. A surgeon can use this as a restriction of the tibial varus cut up to 6 degrees without the requirement for expensive assistive technologies., Competing Interests: The corresponding author is a paid presenter and instructor of Zimmer Biomet., (Thieme. All rights reserved.)

This study examines the potential cost savings for the health system and the community in a broadly accessible model through the increased utilization of unicompartmental knee arthroplasty (UKA) using robotic arm-assisted UKA (raUKA) versus conventional total knee arthroplasty (cTKA). We retrospectively reviewed 240 patients where the first 120 consecutive raUKA performed during this period were matched to 120 cTKAs. Clinical data from the medical records and costs for procedure for each component were collected. Bivariate analyses were performed on the data to determine if there were statistically significant differences by surgery type in clinical outcomes and financial costs. There was a significantly lower cost incurred for raUKA versus cTKA with an average saving of AU$7,179 per case. The operating time (86.0 vs. 75.9 minutes; p  = 0.004) was significantly higher for raUKA, but the length of stay was significantly lower (1.8 vs. 4.8 days; p  < 0.001). There was a significant difference in the use of opioids between raUKA and cTKA (125.0 morphine equivalent [ME] vs. 522.1 ME, p  < 0.001). This study demonstrated that the use of raUKA rather than cTKA in suitably indicated patients may realize significant cost savings., Competing Interests: None declared., (Thieme. All rights reserved.)

Competing Interests: None declared.

An estimated 10 to 15% of total knee arthroplasties (TKAs) are implanted for a diagnosis of arthritis when a valgus deformity is present. There are various techniques and considerations that must be considered for a successful TKA in a patient with a valgus deformity. This article provides a detailed summary of the anatomy, pathology, bone preparation, soft tissue management, implant selection, and complications when performing a TKA in a patient with valgus deformity., Competing Interests: None declared., (Thieme. All rights reserved.)

One-week staged bilateral open-wedge high tibial osteotomies (OWHTOs) can be a safe procedure, with the added advantage of fast functional recovery, cost saving, and reduced hospital stay. However, there can be concerns about correction loss after 1-week staged OWHTOs because high loading is inevitably applied to osteotomy sites during postoperative weight bearing. Although leaving the osteotomy site with no grafts is possible in OWHTOs, the use of grafts can provide additional stability to the osteotomy site and prevent correction loss. We compared the amount and incidence of correction loss between 1-week staged bilateral OWHTOs with and without allogenic bone grafts. Seventy-five patients who underwent 1-week staged bilateral OWHTOs with a locking spacer plate (Nowmedipia, Seoul, Korea) by a single surgeon were retrospectively reviewed. Allogenic cancellous bone grafts were applied in 53 patients (group G; 106 knees, operated consecutively between 2012 and 2017) but not in 22 patients (group N; 44 knees, operated consecutively between 2017 and 2019). Demographics were similar between the groups. Radiographically, the mechanical axis (MA), medial proximal tibial angle (MPTA), and posterior tibial slope (PTS) were evaluated preoperatively and within 1 year postoperatively. Unstable hinge fracture was investigated using computed tomography in all cases. The incidence of correction loss (MPTA loss ≥ 3 degrees) was determined. There were no significant differences in the MA, MPTA, and PTS between the groups preoperatively and 2 weeks postoperatively. The incidence of unstable hinge fractures did not differ. The losses in MA, MPTA, and PTS during the first postoperative year were significantly greater in group N than in group G (MA, -5.5 vs. -2.3 degrees; MPTA, -3.0 vs. 0 degrees; PTS, -2.0 vs. -0.7 degrees; p  < 0.05 on all parameters). The correction loss incidence was 6.6% (7/106) and 31.8% (14/44) in groups G and N, respectively ( p  < 0.001). Appropriate treatment is necessary to prevent correction loss in 1-week staged bilateral OWHTOs. Grafting, which provides additional stability to the osteotomy site, is a recommended method. Level of evidence is IV., Competing Interests: None declared., (Thieme. All rights reserved.)

The optimal force applied during ligament balancing in total knee arthroplasty (TKA) is not well understood. We quantified the effect of increasing distraction force on medial and lateral gaps throughout the range of knee motion, both prior to and after femoral resections in tibial-first gap-balancing TKA. Twenty-five consecutive knees in 21 patients underwent robotic-assisted TKA. The posterior cruciate ligament was resected, and the tibia was cut neutral to the mechanical axis. A digital ligament tensioning tool recorded gaps and applied equal mediolateral loads of 70 N (baseline), 90 N, and 110 N from 90 degrees to full extension. A gap-balancing algorithm planned the femoral implant position to achieve a balanced knee throughout flexion. After femoral resections, gap measurements were repeated under the same conditions. Paired t -tests identified gap differences between load levels, medial/lateral compartments, and flexion angle. Gaps increased from 0 to 20 degrees in flexion, then remain consistent through 90 degrees of flexion. Baseline medial gap was significantly smaller than lateral gap throughout flexion ( p <0.05). Increasing load had a larger effect on the lateral versus medial gaps ( p <0.05) and on flexion versus extension gaps. Increasing distraction force resulted in non-linear and asymmetric gap changes mediolaterally and from flexion to extension. Digital ligament tensioning devices can give better understanding of the relationship between joint distraction, ligament tension, and knee stiffness throughout the range of flexion. This can aid in informed surgical decision making and optimal soft tissue tensioning during TKA., Competing Interests: A.K.S. declares that he has no conflict of interest. C.P., reports that he is an employee of Corin Group/Omni and that he holds stock options in Corin Group/Omni. S.S. reports that he is an employee of Corin Group/Omni. D.L. declares that he has no conflict of interest. J.M.V. reports receiving personal fees from Corin Group, Intellijoint Surgical, Medacta, and Zimmer, receiving payments as a consultant for Corin Group, Intellijoint Surgical, Medacta, and Zimmer, holding stock options in Intellijoint Surgical and Motion Insights, and receiving research funding from Corin Group. J.L. reports receiving consulting fees from Corin Group., (Thieme. All rights reserved.)

Meniscal allograft transplantation (MAT) is an effective reconstructive procedure for treating a symptomatic postmeniscectomy syndrome. It consists of replacing the lost meniscal tissue aiming to improve the clinical outcomes and prevent progressive deterioration of the joint. The aim of this study was to evaluate meniscal graft survivorship and report on the radiographic (in terms of graft extrusion and joint space width and alignment) and the functional results through a midterm follow-up of lateral MAT performed with a soft tissue fixation technique after capsulodesis. In total, 23 patients who underwent lateral MAT as a single procedure were included. The Knee injury and Osteoarthritis Outcome Score, Lysholm, Tegner, and visual analog scale scales were used for patient assessment. Magnetic resonance imaging and a complete radiographic protocol were conducted to determine the degree of meniscal extrusion and the changes in the degree of osteoarthritis and coronal alignment. Assessments were performed after 2 and 7 years of follow-up. A significant improvement in all the scores, relative to preoperative values, was found after 7 years of follow-up. This improvement remained consistent throughout the first and second follow-up periods. A mean absolute extrusion of 2.2 mm ± 1.6 and an extrusion percentage of 28.0% ± 11.43 were found, with no significant differences throughout the follow-up periods. There was no statistically significant difference in terms of the frontal mechanical axis and joint space narrowing between the preoperative value and at the first and second follow-up periods. A survival rate of 85.7% was found after 7 years of follow-up. Capsulodesis results in a low degree of meniscal extrusion in isolated lateral MAT fixed with a suture-only technique, which is maintained after 7 years of follow-up, with a high graft survival index (>85%) and satisfactory results on the functional scales., Competing Interests: None declared., (Thieme. All rights reserved.)

The objective of this prospective study was to assess the precision of restoring the anatomical tibial obliquity, as measured by the medial proximal tibial angle (MPTA) on conventional X-rays, in relation to the surgical technique employed. Specifically, the study aimed to compare the accuracy of tibial obliquity restoration between kinematic alignment (KA) and conventional mechanical alignment (MA) in total knee arthroplasty (TKA). Two-hundred-and-sixty patients underwent either mechanically aligned TKA ( n  = 139) or kinematically aligned TKA ( n  = 121) using conventional instrumentation (CI). Pre- and postoperative X-rays were measured twice by two observers, with a 2-week interval. Inter- and intraclass correlations were calculated, and postoperative tibial obliquity was compared to the preoperative anatomy. In the group of 139 patients with mechanically aligned TKA, no cases with an MPTA deviation greater than 1 degree from 90 degrees were observed. Sixteen percent of the cases ( n  = 22) had a deviation of 0 to 1 degree. The remaining 84% of the cases ( n  = 117) had their MPTA of 90 degrees achieved. In the group of 121 patients with kinematically aligned TKA, no cases had a deviation greater than 1 degree compared with the preoperative MPTA. Thirty-one percent of the cases ( n  = 37) had a deviation of 0 to 1 degree with respect to preoperative MPTA. The remaining 69% of the cases ( n  = 84) had their tibial obliquity restored. Mechanically aligned TKA revealed statistically significant smaller deviations of accuracy compared to kinematically aligned TKA ( p  = 0.005). The inter- and intraclass correlations indicated substantial agreement of all measurements (intraclass correlation coefficient [ICC] < 0.90). Both mechanically aligned and kinematically aligned TKA demonstrated satisfactory outcomes in terms of restoring tibial obliquity or a neutral MPTA of 90 degrees using CI. However, MA showed superior results regarding precision compared to KA. When starting with kinematical alignment using CI, the surgeons should be aware that the learning curve according to accuracy differs to MA. It was a Prospective Level II study., Competing Interests: None declared., (Thieme. All rights reserved.)

Although the accuracy of other types of robotic systems for total knee arthroplasty (TKA) has been assessed in cadaveric studies, no investigations have been performed to evaluate this newly advanced active robotic system. Therefore, the authors aimed to analyze the accuracy of bone resection in terms of thickness and alignment in a cadaveric study. Three cadaveric specimens (six knees) and an active robotic system (CUVIS Joint, CUREXO) were used in the study. Three surgeons with different experiences in robotic TKAs performed this cadaveric study using the same robotic protocol with two different implant designs. The thickness and angle of bone resection planes obtained from the optical tracking system and the difference between resection planes and the planning data were assessed to determine accuracy. With respect to the overall resection accuracy compared to the plan, the cutting depth accuracy was within 1.0 mm mean of root mean square (RMS), and the resection angle accuracy in terms of sagittal, coronal, and axial planes was within 1.0 degree mean RMS. In contrast, no significant differences were observed between the planned and measured values in terms of the resection angles and cutting thickness. The hip-knee-ankle angle at postoperative evaluation was 0.7 degrees ± 0.7 degrees (RMS 1.0 degrees). This in vivo study suggests that the use of this newly advanced active robotic system for TKA demonstrates a high degree of accuracy in terms of resection thickness and alignment. This finding supports the clinical application of this advanced robotic system. LEVEL OF EVIDENCE:  Cadaveric study, Level V., Competing Interests: Y.-B.P. is a paid consultant for CUREXO.B.-O.K. is employed by CUREXO., (Thieme. All rights reserved.)

The use of robotic-assisted surgery (RAS) in total knee arthroplasty (TKA) is becoming increasingly popular due to better precision, potentially superior outcomes and the ability to achieve alternative alignment strategies. The most commonly used alignment strategy with RAS is a modification of mechanical alignment (MA), labeled adjusted MA (aMA). This strategy allows slight joint line obliquity of the tibial component to achieve superior balancing. In the present study, we compared coronal alignment after TKA using RAS with aMA and computer-assisted surgery (CAS) with MA that has been the standard in the center for more than 10 years. We analyzed a prospectively collected database of patients undergoing TKA in a single center. Lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) were compared for both techniques. In 140 patients, 68 CASs and 72 RASs, we observed no difference in postoperative measurements (median 90 degrees for all, LDFA p  = 0.676, MPTA p  = 0.947) and no difference in outliers <2 degrees (LDFA p  = 0.540, MPTA p  = 0.250). The present study demonstrates no benefit in eliminating outliers or achieving neutral alignment of both the femoral and the tibial components in robotic-assisted versus computer-assisted TKA if MA is the target. To utilize the precision of RAS, it is recommended to aim for more personalized alignment strategies. The level of evidence is level III retrospective study., Competing Interests: None declared., (Thieme. All rights reserved.)