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Knowledge regarding the normal alignment of the lower limb is important when considering alignment for total knee arthroplasty. However, few studies have explored the lower limb alignment of healthy Japanese subjects.Between July and October 2020, we performed whole leg standing radiography of 120 legs of 60 healthy adult Japanese volunteers aged50 years in the closed-leg stance. The measurement parameters were hip knee ankle angle (positive for varus), percentage of constitutional varus (hip knee ankle angle ≥ 3°), mechanical axis deviation ratio, mechanical lateral distal femoral angle, medial proximal tibial angle, joint line convergence angle (positive for lateral opening), and tibial joint line angle (positive for medial inclination).The mean measured values for all volunteers, men and women, were as follows: hip knee ankle angle (°), 2.3, 2.6, and 2.0; mechanical axis deviation ratio, 35.8, 35.6, and 36.9; mechanical lateral distal femoral angle (°), 86.7, 87.0, and 86.7; medial proximal tibial angle (°), 85.6, 85.0, and 86.2; joint line convergence angle (°), 0.6, 0.3, and 0.8; and tibial joint line angle (°), -1.0, -0.7, -1.4, respectively. The percentage of constitutional varus was 35.8% overall, 35.8% in men and 35.3% in women. Only the medial proximal tibial angle was smaller in men than that in women (p = 0.003).The mechanical lateral distal femoral and medial proximal tibial angles were smaller, hip knee ankle angle was larger, and percentage of constitutional varus was higher in Japanese subjects than those reported for subjects in other countries. Our findings improve the understanding of Japanese-specific alignments when considering alignment for lower limb surgery, especially, total knee arthroplasty.

This study aimed to evaluate the permissible joint-line obliquity (JLO) based on radiologic and clinical outcomes with midterm follow-up after medial open-wedge high tibial osteotomy (MOWHTO).Patients who had undergone MOWHTO from March 2014 to May 2016 were retrospectively evaluated. They were divided into 4 groups based on JLO as represented by postoperative medial proximal tibial angle (MPTA). Radiologic parameters including MPTA, joint-line orientation angle (JLOA), joint-line convergence angle (JLCA), posterior tibial slope, weightbearing line ratio (WBLR), and coronal translation were analyzed. Clinical outcomes were evaluated with American Knee Society Score (AKSS), Western Ontario and McMaster University Index, and short-form 36 health survey (SF-36). The changes between preoperation and final follow-up in JLOA and MPTA were defined as ΔJLOA and ΔMPTA.A total of 135 knees were finally included (MPTA ≤90.32° as group I; 90.33° to 92.62° as group II; 92.74° to 95.22° as group III; and ≥95.23° as group IV). The last follow-up MPTA, JLOA, and JLCA values were different between the groups (P.001, P.001, and P = .015, respectively). WBLR and JLOA positively correlated with MPTA; however, WBLR showed an abrupt increase at MPTA96.5°, and the JLOA distribution tended to be greater than the regression line at MPTA96°. Moreover, ΔJLOA was not as large as ΔMPTA. The percentage of patients attaining a minimal clinically important difference was significantly lower in the AKSS-functional score and SF-36 physical component summary in group IV (P = .008 and 0.021, respectively).The JLOA did not change as much as the MPTA, but an MPTA95.2° abruptly increased the JLOA and valgus overcorrection after MOWHTO. Poor clinical outcomes were more evident in excessive MPTA (95.2°) than in mildly undercorrected or properly corrected MPTA (95.2°).III, retrospective cohort study.

Purpose It is known that in uni-compartmental knee arthroplasty (UKA) low-volume surgeons have a higher complication and revision rate than high-volume surgeons. Further, robotic-assisted UKA leads to lower early revision rate as well as fewer limb and joint line outliers compared to conventional UKA. The purpose of this study was to retrospectively analyze the outliers’ and revision rate of low-volume UKA surgeons with different robotic systems at short-term follow-up. Methods In this case–control study, 103 robotic-assisted UKAs were included. The procedures were performed between 2016 and 2019 from two low-volume UKA surgeons with an imageless (IL) (63 patients) and image-based (IB) (40 patients) robotic system. Alignment outliers, joint line (JL) reconstruction, complication and revision rates of the two different robotic systems were analyzed. The minimum follow-up was two years. Outliers were defined as a postoperative valgus malalignment greater than 182°. The surgery time for all procedures was evaluated. Results The overall revision rate was 3.9% (4 of 103). Two occurred in the IB group (5.0%) and two in the IL group (3.2%). No valgus malalignment outliers were observed in both groups. The mean JL was not distalized by more than 2 mm in both groups (IL: 1.3 ± 1.6 mm vs. IB: 1.8 ± 0.9 mm, p value 0.08). The IL procedures had a significant lower mean surgery time (55 ± 13 min vs. 68 ± 14, p value 0.001). Conclusion Robotic-assisted UKA is a safe procedure in the hand of low-volume UKA surgeons. Robotic-assisted UKA minimizes overcorrection into valgus mal-alignment. Low revision rates are observed at short-term follow-up for robotic-assisted UKA. The choice of the different robotic systems has no impact on the outcome.

In total knee arthroplasty (TKA), knee phenotypes including joint line obliquity are of interest regarding surgical realignment strategies. The hypothesis of this study is that better clinical results, including decreased postoperative knee pain, will be observed for patients with a restored knee phenotype. A retrospective analysis was performed on prospective data, including 1078 primary osteoarthritic knees in 936 patients. The male:female ratio was 780:298, mean age at surgery was 71.3 years ± 8.0. International Knee Society Scores and standardized long-leg radiographs (LLR) were collected preoperatively and at 2 years follow-up after TKA. Patients were categorized using the Coronal Plane Alignment of the Knee (CPAK) classification including the lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) measured on LLR by a single observer, allowing knee phenotypes to be categorized considering the arithmetic hip–knee–ankle (aHKA) angle (MPTA-LDFA) as measure of constitutional alignment, and joint line obliquity (JLO) (MPTA + LDFA). Clinical results were compared between patients with surgically restored preoperative constitutional knee phenotype to patients without restored constitutional knee phenotypes. Descriptive data analysis such as means, standard deviations and ranges were performed. T tests for independent samples were performed to compare group differences. Comparisons of categorical data were performed using the χ2 test. Significance was set at p

Objectives: The aim of this study was to assess the incidence and significance of pes anserine exostosis. Material and Methods: A retrospective search of radiological reports of an individual radiologist over a 12-year period with the term “anserine” was performed. Results: There were 34 pes anserine exostoses which arose at an average of 3.6 cm from the medial joint line. The average incidence of pes anserine exostosis is 1 in 1500 patients undergoing radiographs of one or both knees. Conclusion: Pes anserine exostosis is an incidental finding and is of doubtful clinical significance with no evidence of associated pes anserine bursitis. This is the largest series of pes anserine exostosis.

AimsSurgeons commonly resect additional distal femur during primary total knee arthroplasty (TKA) to correct a flexion contracture, which leads to femoral joint line elevation. There is a paucity of data describing the effect of joint line elevation on mid-flexion stability and knee kinematics. Thus, the goal of this study was to quantify the effect of joint line elevation on mid-flexion laxity.MethodsSix computational knee models with cadaver-specific capsular and collateral ligament properties were implanted with a posterior-stabilized (PS) TKA. A 10° flexion contracture was created in each model to simulate a capsular contracture. Distal femoral resections of + 2 mm and + 4 mm were then simulated for each knee. The knee models were then extended under a standard moment. Subsequently, varus and valgus moments of 10 Nm were applied as the knee was flexed from 0° to 90° at baseline and repeated after each of the two distal resections. Coronal laxity (the sum of varus and valgus angulation with respective maximum moments) was measured throughout flexion.ResultsWith + 2 mm resection at 30° and 45° of flexion, mean coronal laxity increased by a mean of 3.1° (SD 0.18°) (p < 0.001) and 2.7° (SD 0.30°) (p < 0.001), respectively. With + 4 mm resection at 30° and 45° of flexion, mean coronal laxity increased by 6.5° (SD 0.56°) (p < 0.001) and 5.5° (SD 0.72°) (p < 0.001), respectively. Maximum increased coronal laxity for a + 4 mm resection occurred at a mean 15.7° (11° to 33°) of flexion with a mean increase of 7.8° (SD 0.2°) from baseline.ConclusionWith joint line elevation in primary PS TKA, coronal laxity peaks early (about 16°) with a maximum laxity of 8°. Surgeons should restore the joint line if possible; however, if joint line elevation is necessary, we recommend assessment of coronal laxity at 15° to 30° of knee flexion to assess for mid-flexion instability. Further in vivo studies are warranted to understand if this mid-flexion coronal laxity has negative clinical implications. Cite this article: Bone Joint J 2021;103-B(6 Supple A):87–93.

Background The systems for precisely locating the joint line during primary and revision total knee arthroplasty are still controversial, and they should be better evaluated in the Chinese population. Methods A total of 451 standard anteroposterior knee radiographs from 451 healthy Chinese people (283 males and 168 females, the average age of 33.26 years, range 20–50 years) were included to measure the femoral width (FW) and the distances from the adductor tubercle (AT), the medial epicondyle (ME), the lateral epicondyle (LE), and the fibular head (FH) to the joint line (JL). Correlation between FW and distances from landmarks to the joint line was evaluated using Pearson correlation coefficient, and the ratios of ATJL, MEJL, LEJL, FHJL to FW were calculated. Results The average distances from the AT, the ME, the LE, the FH to the JL were 49.4 ± 5.0 mm, 28.3 ± 3.1 mm, 26.9 ± 2.9 mm, 20.0 ± 4.0 mm, respectively. An excellent linear correlation was found between FW and the distance from AT to the joint line (R = 0.836, R2 = 0.698); it was more reliable than the LE (R = 0.686, R2 = 0.471) and the ME (R = 0.672, R2 = 0.452). The average ratios of ATJL/FW, MEJL/FW, LEJL/FW were 0.553, 0.317, and 0.302, respectively. There were significant differences between our results and the studies based on the Western people. Conclusion The AT can be used as a reliable landmark to locate the JL precisely by the formula (ATJL = 0.548 × FW in males; ATJL = 0.562 × FW in females) in the Chinese population. The LE and ME can be the second choices. Moreover, it may be better to use ratios from the research based on the same race.

Instability is an increasingly common cause and symptom of failure of Total Knee Arthroplasty (TKA). Patients seek ‘Functional Stability’, which is the sum of both a balanced joint and, if necessary, mechanical constraint. The objective of this paper is to classify the different types of TKA instability and their causes. Based on this classification, the authors give methodical recommendations for instability management. Instability classification Instability in revision TKA can be classified into 3 types based on the management of bone loss and ligamentous deficiency which directs the level of constraint required to achieve functional stability. Type 1 Bone deficiency: Revision with restoration of joint line and rebuilding the bony anatomy results in a balanced joint. No increased constraint is needed. Type 2 Ligament and soft tissue deficiency: Requires increased constraint to overcome instability Type 3 Composite (Total) deficiency: (combined Type 1 and 2). The multiple causes of instability are outlined for each Instability type along with an algorithm for restoring the joint line and adding titrated constraint to restore functional stability.

To compare the radiographic, clinical, and arthroscopic outcomes of varus osteoarthritic knees treated with an open-wedge high tibial osteotomy (OWHTO) alone or with a double-level osteotomy (DLO). It was hypothesized that treatment with DLO would maintain the joint line obliquity (JLO) and acquire better arthroscopic and clinical outcomes after surgery than OWHTO alone. Knees with predicted medial proximal tibial angle (MPTA) > 95° were treated with OWHTO alone or with DLO. Preoperatively, age, body mass index, and hip-knee-ankle angle (HKA) differed between the two groups. Therefore, after adjustment for those factors, 34 knees with OWHTO alone and 34 knees with DLO were compared. On whole-leg radiographs for a single leg, HKA, weightbearing line (WBL) ratio, lateral distal femoral angle (LDFA), MPTA, and JLO were measured before and 2 years after surgery. Clinical outcomes were evaluated by the Knee Society Score (KSS) knee, KSS function, Lysholm, and Knee injury and Osteoarthritis Outcome Score (KOOS) scores before and 2 years after surgery. Arthroscopic findings were obtained before and 1 year after surgery. Various factors were compared between the two groups. JLO increased significantly from 1.4° to 6.3° in the OWHTO group (p

Background Joint line orientation angle (JLOA) is the angle between the knee joint line and the floor. It has been reported to be related to postoperative outcome after TKA. Regarding unicompartmental knee arthroplasty (UKA), although it can be horizontal after UKA because it is a resurfacing surgery, there are few reports about the JLOA after UKA and its impact on clinical outcomes. Purpose The purpose of this study was to reveal the relationship between JLOA and clinical outcome after UKA. Methods This study included 106 knees in 53 consecutive patients with osteoarthritis who underwent simultaneous bilateral mobile-bearing UKA. Their pre- and postoperative JLOAs were measured by full-leg-length standing coronal radiographs. We also evaluated the tibial component height (TCH) as the factor which we assumed could influence JLOA. We analyzed the patients’ JLOAs, TCHs and clinical outcomes. Results Pre- and postoperative JLOA were 0.4 ± 2.4° and 2.7 ± 2.6°, respectively. The JLOA significantly tilted medially (P Conclusion The JLOA significantly tilted medially after UKA. An excessive medial tilt of the JLOA was associated with poorer postoperative outcomes of UKA. It is therefore recommended to keep the JLOA horizontal and to avoid a lower tibial cut.

Background: The number of total knee arthroplasty (TKA) surgeries performed each year is increasing worldwide and mechanical alignment (MA) is currently seen as the gold standard procedure. However, taking neutral alignment as the universal goal may be mistaken. In our hospital, we currently conduct kinematically aligned TKA (KA-TKA). Three different types of implants are used: the cruciate-retaining (CR) type, cruciate-sacrificing (CS) type, or bi-cruciate-retained (BCR) type. We aimed to compare the coronal alignment observed following KA-TKA and MA-TKA and in normal knees, as well as that achieved with different types of implants. Methods: The study comprised 206 knees of Japanese patients who underwent KA-TKA using varying implants in our Hospital between May 2019 and April 2020. Measurements of pre- and postoperative coronal alignment were determined from weight-bearing full-leg standing radiographs. The postoperative results were compared to measurements taken from patients who underwent MA-TKA (N = 96) and normal knees (N = 60). Results: No significant differences between the KA-TKA group and normal knees were found for the medial proximal tibial angle (MPTA) (–4.2° ± 2.6° vs –3.8° ± 2.5°) or joint line orientation angle (JLOA) (0.2° ± 1.9° vs 0.3° ± 1.4°). However, when MA-TKA was compared to KA-TKA and normal knees, there were significant differences in both the MPTA and JLOA (p Conclusions: Here, we demonstrated that following KA-TKA, the articular surface of the tibia exhibited a similar varus alignment as that of normal knees, meaning that the technique reproduces the native knee. Furthermore, KA is patient-specific, and does not have the same failures as MA-TKA. Therefore, we anticipate a paradigm shift from mechanical to kinematic alignment, which may help reduce the dissatisfaction rate of TKA patients.

Metaphyseal sleeves have become an integral part of surgeons’ armamentarium in dealing with complex revision knee arthroplasty. They offer the advantages of addressing bone defects with biological fixation techniques, efficient surgical preparation providing a stable tibial platform which optimises joint line positioning and gap balancing leading to excellent long-term survivorship and clinical outcomes. Here, we review the concept of metaphyseal fixation, indications of metaphyseal sleeves and their limitations with our surgical tips on how to remove well-fixed sleeves. We also present our tertiary experience and review clinical outcome studies of metaphyseal sleeves in revision knee arthroplasty literature.

Background: Difference in the clinical course and outcomes between simultaneous- and staged-bilateral medial opening wedge high tibial osteotomies (OWHTOs) over time was unknown. The study hypothesis was that patients who underwent simultaneous-bilateral OWHTO (SMBO) have a more rapid improvement in knee function than those who underwent staged-bilateral OWHTO (STBO) due to difference in the change of lower limb alignment between SMBO and STBO. Methods: The records of 56 knees in 28 patients who underwent either SMBO (n = 28) or STBO (n = 28) were retrospectively analysed. The time course data of weight-bearing line percentage (%WBL), joint line convergence angle (JLCA), and Knee Society Score were compared between the two procedures. Results: Hospitalisation for SMBO was longer than that for STBO by 1 week. No significant difference was observed in %WBL between the two procedures. The JLCA was significantly lower with SMBO than with the first-stage surgery of STBO (P

Purpose To compare joint line restoration after unicompartmental knee arthroplasty (UKA) between conventional and robotic-assisted surgery. Previous studies have shown that joint line distalization can lead to higher failure rates. The hypothesis was that robotic-assisted UKA is associated with less femoral component distalization and a precise tibial cut, which allows a more anatomical restitution of the knee joint line. Methods Retrospective cohort study of patients undergoing medial or lateral UKA between May 2018 and March 2020. Preoperative and postoperative radiologic assessment of the joint line was performed by two observers, using three different methods, one for tibial slope and one for tibial resection. Robotic assisted UKA and conventional UKA groups were compared. Results Sixty UKA were included, of which 48 (77.42%) were medial. Robotic-assisted UKA were 40 (64.52%) and 22(35.48%) were conventional The distalization of the femoral component was higher in the conventional group despite the method of measurement used In both Weber methods, the difference was statistically different: Conventional 2.3 (0.9 to 5.6) v/s Robotic 1.5 (− 1.1 to 4.1) (p =0.0025*). A higher proportion of patients achieved a femoral component position ≤ two millimeters from the joint line using robotic-assisted UKA compared to the conventional technique . No statistical difference between robotic-assisted and conventional UKA was found in tibial resection and slope. Conclusion Robotic-assisted UKA shows a better rate of joint line restoration due to less femoral component distalization than conventional UKA. No difference was found in the amount of tibial resection between groups in this study. Level of evidence III

Background:Although joint-line obliquity (JLO) after open-wedge high tibial osteotomy (OWHTO) is commonly encountered, especially in cases of overcorrection, its effect has not been fully elucidated or has been assessed only in the short term. The acceptable range of JLO, often recognized as ≤4°, has not been determined as per the midterm outcomes of OWHTO.Hypothesis:Joint-line obliquity exceeding the acceptable limit after OWHTO would accelerate cartilage degeneration and adversely affect midterm clinical outcomes.Study Design:Cohort study; Level of evidence, 3.Methods:A total of 109 patients who underwent OWHTO between 2010 and 2015 with a mean follow-up period of 55.0 months (range, 24-102 months) were reviewed. JLO was defined as the angle between the lines parallel to the floor and to the tibial plateau on a long-standing hip-to-ankle radiograph. For radiologic evaluation according to JLO, the medial joint space width (JSW) was measured on a standing 45° flexion posteroanterior view and standardized with the width of the tibial plateau as reference, after which changes in JSW (ΔJSW) between the 6- and 12-month postoperative period and the latest follow-up were calculated. ΔJSW was analyzed according to 2 different cutoff values of JLO: JLO of 4°, which is currently recognized as the acceptable limit, and that derived from the receiver operating characteristic (ROC) curve for the third quartile of ΔJSW. Multivariate regression analysis including JLO as well as other demographic and radiologic factors was performed. Clinical outcomes were evaluated in the same way using Knee Society (KS) objective and functional scores.Results:With a JLO cutoff of 4° in the multivariate regression analysis, JLO was not significantly associated with ΔJSW ( P = .545). However, in the KS objective and functional score analyses, JLO ≥4° was found to be a significant factor ( P = .045 and .005, respectively). The ROC curve showed a cutoff JLO of 6°, which was significantly associated with ΔJSW ( P = .001). JLO ≥6° remained significant in the analyses for KS objective and functional score ( P = .012 and .001, respectively).Conclusion:The adverse effect of JLO on radiologic outcomes was shown when JLO was ≥6°. In clinical aspects, worse outcomes were found in cases of JLO ≥4°.

The objectives of this study were to examine the relation between clinical outcomes 1 year postoperatively, in a cohort of mechanically aligned total knee arthroplasties (TKA), and (1) the degrees of alignment change of the tibial, femoral and the hip–knee–ankle (HKA) angle; (2) the change of phenotype; (3) the postoperative knee joint line orientation to the floor. Pre-operative and postoperative long-leg X-rays of 90 patients were used to determine the coronal alignment. The absolute difference between the pre-operative and postoperative measurements was determined and the outcomes were categorized in whether or not a change in phenotype had occurred. Finally, the orientation of the knee joint line relative to the floor (tibial joint line angle—TJLA) was measured. Clinical outcomes were determined with the KOOS and KSS at 1-year follow-up. The clinical outcomes (1) did not correlate with the absolute difference of the alignment measured; (2) did not show a difference between patients with or without a change in phenotype; and (3) were higher (KOOS ADL, Sport and QoL) in patients with a medial open TJLA. This study showed no correlation between clinical outcomes and joint line restoration of the femur, tibia or HKA in patients after TKA. Leaving the prosthesis with some degrees of under correction on the coronal plane maintaining the phenotype, was not associated to better clinical results compared to TKA overcorrection. Nevertheless, the results showed that patients with a medial open TJLA had better clinical outcomes than patients with a lateral open TJLA. III.

A considerable proportion of patients (19%) are dissatisfied after total knee arthroplasty (TKA). Possible factors contributing to this dissatisfaction are decreased posterior condylar offset (PCO) with subsequent joint line elevation, leading to mid-flexion instability. Secondly, the pre-disease mechanical alignment is changed into a neutral alignment. The Flexion First Balancer was developed to avoid these problems. This technique aims to maintain MCL isometry by restoring medial PCO and medial joint line to its pre-disease level. Also, to reconstruct the pre-disease mechanical alignment by adjusting the distal femoral angle. In this study we provide a detailed technical overview of the Flexion First Balancer technique.

Dissatisfaction following total knee arthroplasty is a well-documented phenomenon. Although many factors have been implicated, including modifiable and nonmodifiable patient factors, emphasis over the past decade has been on implant alignment and stability as both a cause of, and a solution to, this problem. Several alignment targets have evolved with a proliferation of techniques following the introduction of computer and robotic-assisted surgery. Mechanical alignment targets may achieve mechanically-sound alignment while ignoring the soft tissue envelope; kinematic alignment respects the soft tissue envelope while ignoring the mechanical environment. Functional alignment is proposed as a hybrid technique to allow mechanically-sound, soft tissue-friendly alignment targets to be identified and achieved.Cite this article: Bone Joint J 2020;102-B(3):276–279.

The aim of this systematic review was to evaluate the evidence on reservation of Posterior Femoral Condylar Offset (PFCO) and Joint Line (JL) after Revision Total Knee Arthroplasty (RTKA) for im- proved functional outcomes. A comprehensive search of PubMed, Medline, Cochrane, CINAHL, and Embase databases was conducted, with papers published from the inception of the database to October 2020 included. All relevant articles were retrieved, and their bibliographies were hand searched for further references on Posterior condylar offset and revision total knee arthroplasty. The search strategy yielded 28 articles. After duplicate titles were excluded, abstracts and full text were reviewed. Nine studies were assessed for eligibility, four studies were excluded because they did not fully comply with the inclusion criteria. Six articles were finally included in this systematic review. Based on this systematic review restoration of the JL and PFCO in RTKR is associated with a significant improvement in the post-operative range of motion, KSS, OKS, patellar function, and SF-36. Reservation of JL should be a major consideration when undertaking RTKA. Of note, increasing PFCO to balance the flexion gap while maintaining joint line should be well assessed intra-operatively. The upper limit of the PFCO that widely accepted is up to 40 % greater than that of the native knee. 4 mm is the upper limit for JL restoration. Level of evidence III.

Aims Nearly 99,000 total knee arthroplasties (TKAs) are performed in UK annually. Despite plenty of research, the satisfaction rate of this surgery is around 80%. One of the important intraoperative factors affecting the outcome is alignment. The relationship between joint obliquity and functional outcomes is not well understood. Therefore, a study is required to investigate and compare the effects of two types of alignment (mechanical and kinematic) on functional outcomes and range of motion. Methods The aim of the study is to compare navigated kinematically aligned TKAs (KA TKAs) with navigated mechanically aligned TKA (MA TKA) in terms of function and ROM. We aim to recruit a total of 96 patients in the trial. The patients will be recruited from clinics of various consultants working in the trust after screening them for eligibility criteria and obtaining their informed consent to participate in this study. Randomization will be done prior to surgery by a software. The primary outcome measure will be the Knee injury and Osteoarthritis Outcome Score The secondary outcome measures include Oxford Knee Score, ROM, EuroQol five-dimension questionnaire, EuroQol visual analogue scale, 12-Item Short-Form Health Survey (SF-12), and Forgotten Joint Score. The scores will be calculated preoperatively and then at six weeks, six months, and one year after surgery. The scores will undergo a statistical analysis. Discussion There is no clear evidence on the best alignment for a knee arthroplasty. This randomized controlled trial will test the null hypothesis that navigated KA TKAs do not perform better than navigated MA TKAs. Cite this article: Bone Jt Open 2021;2(11):945–950.

Purpose To assess a novel method of three-dimensional (3D) joint line (JL) restoration based on the contralateral tibia and fibula. Methods 3D triangular surface models were generated from computed tomographic data of 96 paired lower legs (48 cadavers) without signs of pathology. Three segments of the tibia and fibula, excluding the tibia plateau, were defined (tibia, fibula, tibial tuberosity (TT) and fibular tip). A surface registration algorithm was used to superimpose the mirrored contralateral model onto the original model. JL approximation and absolute mean errors for each segment registration were measured and its relationship to gender, height, weight and tibia and fibula length side-to-side differences analyzed. Fibular tip to JL distance was measured and analyzed. Results Mean JL approximation did not yield significant differences among the three segments. Mean absolute JL error was highest for the tibia 1.4 ± 1.4 mm (range: 0 to 6.0 mm) and decreased for the fibula 0.8 ± 1.0 mm (range: 0 to 3.7 mm) and for TT and fibular tip segment 0.7 ± 0.6 (range: 0 to 2.4 mm) (p = 0.03). Mean absolute JL error of the TT and fibular tip segment was independent of gender, height, weight and tibia and fibula length side-to-side differences. Mean fibular tip to JL distance was 11.9 ± 3.4 mm (range: 3.4 to 22.1 mm) with a mean absolute side-to-side difference of 1.6 ± 1.1 mm (range: 0 to 5.3 mm). Conclusion 3D registration of the contralateral tibia and fibula reliably approximated the original JL. The registration of, TT and fibular tip, as robust anatomical landmarks, improved the accuracy of JL restoration independent of tibia and fibula length side-to-side differences. Level of evidence IV

Introduction:After a better understanding of normal knee anatomy and physiology, the Kinematic Alignment (KA) technique was introduced to improve clinical outcomes of total knee arthroplasty (TKA). The goal of the KA technique is to restore the pre-arthritic constitutional lower limb alignment of the patient. There is, however, a large range of normal knee anatomy. Unusual anatomies may be biomechanically inferior and affect TKA biomechanics and wear patterns. In 2011, the leading author proposed the restricted kinematic alignment (rKA) protocol, setting boundaries to KA for patients with an outlier or atypical knee anatomy.Material and Equipment:rKA aims to reproduce the constitutional knee anatomy of the patient within a safe range. Its fundamentals are based on sound comprehension of lower limb anatomy variation. There are five principles describing rKA: (1) Combined lower limb coronal orientation should be ± 3° of neutral; (2) Joint line orientation coronal alignment should be within ± 5° of neutral; (3) Natural knee's soft tissues tension/ laxities should be preserved/restored; (4) Femoral anatomy preservation is prioritized; (5) The unloaded/most intact knee compartment should be resurfaced and used as the pivot point when anatomical adjustment is required. An algorithm was developed to facilitate the decision-making.Methods:Since ~50% of patients will require anatomic modification to fit within rKA boundaries, rKA is ideally performed with patient-specific instrumentation (PSI), intra-operative computer navigation or robotic assistance. rKA surgical technique is presented in a stepwise manner, following the five principles in the algorithm.Results:rKA produced excellent mid-term clinical results in cemented or cementless TKA. Gait analysis showed that rKA TKA patients had gait patterns that were very close to a non-operated control group, and these kinematics differences translated into significantly better postoperative patient-reported scores than mechanical alignment (MA) TKA cases.Discussion:Aiming to improve the results of MA TKA, rKA protocol offers a satisfactory compromise that recreates patients' anatomy in most cases, omitting the need for extensive corrections and soft tissue releases that are often required with MA. Moreover, it precludes the reproduction of extreme anatomies seen with KA.

To assess the usefulness of a whole-leg radiograph standing on lateral-wedge insole (LWI) for predicting the change in joint line convergence angle (JLCA) before vs. after high tibial osteotomy (HTO). Forty knees with medial osteoarthritis underwent open-wedge HTO. Pre-operatively, all patients had whole-leg radiographs taken in three different conditions: supine, standing, and standing on LWI inclined at 20°. A standing whole-leg radiograph was also obtained post-operatively. Radiological measurements including JLCA and percentage of mechanical axis (%MA) were compared. Using pre-operative radiographs, correction angles were calculated with the target %MA at 62.5%. Correlations between the difference in calculated correction angle among the three pre-operative conditions and the change in JLCA before vs. after HTO were assessed. In the pre-operative standing conditions, the mean JLCA of 3.8° was significantly decreased to 3.2° using LWI, which did not differ from post-operative JLCA of 3.1°. Mean %MA significantly shifted laterally from 20.6 to 24.8% using LWI, and was strongly correlated with the change in JLCA (coefficient, 0.83). Calculated correction angles differed significantly among the three pre-operative conditions. The difference in calculated correction angle between standing with and without LWI was strongly correlated to the change in standing JLCA before vs. after HTO (coefficient, 0.73). Larger differences in calculated correction angles between pre-operative radiographs standing with and without LWI predicted larger changes in JLCA after HTO. Whole-leg radiograph standing on LWI is a promising modality for correct pre-operative planning considering patient-specific changes in JLCA before vs. after HTO. IV.

The aim of this study was to demonstrate, whether the degree of limb alignment correction in varus knee osteoarthritis correlated with an increase in ankle symptoms and to define a cut-off value concerning the degree of correction above which to expect ankle problems. Ninety-nine consecutive patients with preoperative intraarticular varus knee deformities who underwent total knee arthroplasty were retrospectively analyzed. Patients were examined clinically (Knee Society Score, Forgotten Joint Score, Foot Function Index, Range of Motion of the knee and ankle joint, pain scales) as well as radiologically. The mean follow-up time was 57 months. The degree of operative limb alignment correction strongly correlated with the Foot Function Index (R = 0.91, p

Coronal correction errors after medial opening wedge high tibial osteotomy (MOWHTO) occasionally occur even with the assistance of navigation. The purpose of the present study was to determine the navigation accuracy in MOWHTO and to identify factors that affect the coronal correction error after navigation-assisted MOWHTO. A total of 114 knees treated with navigation-assisted MOWHTO were reviewed retrospectively. Mechanical axis (MA) on standing radiograph and medial proximal tibial angle (MPTA) were measured preoperatively and at 6 months postoperatively, and the differences (ΔMA and ΔMPTA) were calculated. Joint line convergence angle (JLCA) on supine and standing radiographs was measured preoperatively, and their difference (ΔJLCA) was calculated. To assess the navigation accuracy, ΔMA and ΔMPTA were compared with the coronal correction by navigation (ΔNMA) using intraclass correlation coefficients (ICCs). Univariable and multivariable regression analyses were used to identify factors that affect coronal correction discrepancy (ΔMA − ΔNMA). The reliability of navigation was good in terms of bony correction (ICC between ΔNMA and ΔMPTA, 0.844) and fair in terms of MA correction (ICC between ΔNMA and ΔMA, 0.706). The mean coronal correction discrepancy was 2.0° ± 2.4°. In the multivariable analysis, ΔJLCA was shown to be a predictive factor of coronal correction discrepancy (unstandardized coefficient, 1.026; R2, 0.470). Navigation in MOWHTO provided reliable information about bony correction; however, MA tended to be overcorrected. The difference in JLCA between the supine and standing radiographs was the most important preoperative factor that predicted the coronal correction discrepancy after MOWHTO. In patients with larger ΔJLCA, each degree of ΔJLCA should be subtracted from the planned amount of correction angle when preoperative planning is performed using standing radiographs. IV.

The efficacy and outcomes for the concurrent repair of medial meniscus posterior horn root tear (MMPHRT) during open wedge high tibial osteotomy (OWHTO) are unclear. This study compared the radiologic, arthroscopic, and clinical outcomes between repaired and unrepaired MMPHRT during OWHTO. Fifty-seven patients were prospectively enrolled from 2014 to 2016. The radiologic, arthroscopic, and clinical outcomes were compared between 25 patients who underwent OWHTO with all-inside repair of MMPRT using FasT-Fix (repaired group) and 32 patients who underwent OWHTO without repair of MMPRT (unrepaired group) with a mean 2-year follow up in both groups. The meniscal healing status was classified as complete, partial, or no healing, according to second-look arthroscopic findings. The medial meniscal extrusion (MME) was evaluated using magnetic resonance imaging. The width of medial joint space, joint line convergence angle (JLCA), posterior tibial slope (PTS), Kellgren–Lawrence (KL) grade, hip-knee-ankle angle, and weight-bearing line ratio was evaluated on simple standing. The clinical outcomes were evaluated using the Knee Society score and the Western Ontario and McMaster University score. Healing rates (partial and complete) of the MMPHRT showed a statistical difference between the two groups (repaired group vs. unrepaired group, 19/25 (76%) vs. 13/32 (40.6%), p = 0.008). The postoperative MME showed no statistical differences between groups (repaired versus unrepaired group: 4.5 ± 1.3 mm vs. 4.5 ± 2.1 mm, p = 0.909). The postoperative width of medial joint space, JLCA, PTS, and KL grade all showed no statistical differences between groups after 2 years of OWHTO. Other radiologic parameters and clinical outcomes showed no statistical differences between groups. Repair of the MMPHRT during OWHTO showed a superior healing rate to the unrepaired MMPHRT. However, repair of the MMPHRT was not related to the radiologic and clinical outcomes. Therefore, there is no clear evidence of the need for the MMPHRT repair during OWHTO.

Background The adductor tubercle (AT) has been used intraoperatively as a landmark to evaluate the joint line position in knee arthroplasty. The purpose of this study was to determine whether the AT could be clearly identified on radiographic imaging as well as if the AT to joint line distance could be accurately measured for use as a radiographic landmark. Methods The distance from the AT to the joint line was measured on each of 78 knees during total knee arthroplasty. Next, the AT was marked with a metal marker for radiographic analysis. On the postoperative radiograph, the location of the AT was determined by tracing the metal marker. Subsequently, the radiographic joint line distance (RJLD) was measured and compared with the intraoperative joint line distance (IJLD) to test the agreement of the measurements. Results Location analysis indicated that the inflection point on the radiographic contour of the distal femur was the predicted location for the AT. The mean IJLD was 45 ± 3 mm and the RJLD was 45 ± 4 mm. The intraclass correlation coefficient was used to evaluate the inter-rater reliability between the two methods; that coefficient was 0.751, indicating good agreement between them. Measurements on the radiograph were comparable to the intraoperative measurements of the operated knees. Conclusions In addition to being an intraoperative landmark, the AT may also be an eligible radiographic landmark for analyzing joint line level. The RJLD measurement may be obtained to plan the joint line position in knees with significant bone loss preoperatively and to follow up the results of surgery postoperatively.

Aim The screw length is important to achieve a stable fixation for medial malleoli fractures. We aimed to evaluate the optimal screw length for different age groups in surgically treated medial malleoli fractures. The second aim was to identify the utility of the distance of epiphyseal scar to joint line or joint line to medullary space for assessment of screw length. Material method 368 X-rays and computed tomography (CT) images of ankle joints were retrospectively evaluated for optimal screw length, epiphyseal scar to joint line distance, joint to medullary space distance. The mean screw length for each decade was calculated. The correlations of screw length with age, screw length with distance of epiphyseal scar to joint line, and screw length with distance of joint line to medullary space were evaluated. Results The optimal screw length was obviously decreased in patients in 61–70 and >70 years old group (p = 0.002). As the distance of epiphyseal scar from joint line was increased, the optimal length of screw was also increased (p = 0.001). The distance of epiphyseal scar from joint line was decreased by age (p = 0.011). Conclusion The optimal screw length was decreased by age and the epiphyseal scar to joint line distance could be a clue for optimal screw length in medial malleoli fractures.

To propose a geometric model to quantify the bone defect and the glenoid medialisation (in millimetres) compared to the native joint line. We also evaluated the reliability of this geometric model. Using two-dimensional CT imaging, we built a hypothetical triangle on the axial scan consisting of the following: side A, length (millimetres) of the glenoid bone; side B, average length (millimetres) of the glenoid in a healthy population; side C, the missing side; and angle α, the retroversion angle calculated using the Friedman method. The resulting triangle represents the bone defect, and its height represents the medialisation of the native joint line. To estimate inter-operator reliability, two physicians (operator 1 and operator 2) took the following measurements: angle α, side A, side C, semi-perimeter, area defect and height. Forty participants (mean age ± SD 45 ± 10 years, range 26–43 years)—22 women and 18 men—participated in the study. We applied the cosine theorem (Carnot theorem) to calculate side C. After obtaining the three sides, the area of the triangle can be determined. Once the area is known, it is possible to extrapolate the height of the triangle, which corresponds to the loss of vault depth due to the bone defect. With respect to inter-operator reliability, the ICCs for all measurements were > 0.99, exhibiting a very high correlation. The proposed geometric model can be used to quantify the glenoid bone deficit and the glenoid medialisation compared to the native joint line, which can be used to improve surgical treatment.

Background The biomechanical effects of joint-line medialization during shoulder surgery are poorly understood. It was therefore the purpose of this study to investigate whether medialization of the joint line especially associated with total shoulder arthroplasty leads to changes in the rotator cuff muscle forces required to stabilize the arm in space. Methods A validated computational 3-D rigid body simulation model was used to calculate generated muscle forces, instability ratios, muscle-tendon lengths and moment arms during scapular plane elevation. Measurements took place with the anatomical and a 2 mm and 6 mm lateralized or medialized joint line. Results When the joint line was medialized, increased deltoid muscle activity was recorded throughout glenohumeral joint elevation. The rotator cuff muscle forces increased with medialization of the joint line in the early phases of elevation. Lateralization of the joint line led to higher rotator cuff muscle forces after 52° of glenohumeral elevation and to higher absolute values in muscle activity. A maximum instability ratio of >0.6 was recorded with 6 mm of joint-line medialization. Conclusion In this biomechanical study, medialization and lateralization of the normal joint line during total shoulder arthroplasty led to substantial load changes on the shoulder muscles used for stabilizing the arm in space. Specifically, medialization does not only lead to muscular shortening but also to increased load on the supraspinatus tendon during early arm elevation, the position which is already most loaded in the native joint.

The present study evaluated the outcomes of internal fixation with a joint line plate in the treatment of tibial plateau fractures caused by hyperextension of the varus. The study included 25 cases (13 males and 12 females; age, 19-71 years) of tibial plateau fracture caused by hyperextension of the varus, which were treated at Puai Hospital, Tongji Medical College (Wuhan, China) between January 2015 and June 2017. Fractures were treated with internal fixations of the inner cortex with a self-clipped joint line plate made of steel. After the surgery, patients were examined immediately and at 3, 6 and 12 months. Healing was evaluated by X-ray examination. All cases were cured during follow-up. After surgery, one patient developed partial necrosis of the skin margin of the incision and recovered after a dressing change. Furthermore, one patient with a concomitant peroneal nerve injury and hypoesthesia recovered after treatment with neurotrophic drugs. No screw loosening, fractures or failure of the internal fixations occurred. According to the X-ray results, there were significant differences in the tibial plateau angle (TPA) and medial posterior slope angle (m-PSA) between the pre-operative stage and 12 months post-operatively (P0.05). In conclusion, internal fixation with a joint line plate is an appropriate treatment for tibial plateau fractures involving the anteromedial margin with good clinical efficacy.

Purpose One of the key factors to the successful revision of total knee arthroplasty (rTKA) is the reconstruction of the joint line, which can be determined using the epicondylar ratio (ER). The measurement is established in X-ray and MRI. However, it is not known whether computed tomography (CT) allows a more reliable determination. The objective was to assess the reliability of the ER in CT and to determine the correlation between the ER in CT and a.p. X-ray of the knee. Methods The ER was determined on X-ray and CT images of a consecutive series of 107 patients, who underwent rTKA. Measurements were made by two blinded observes, one measured twice. The inter- and intraobserver agreement, as well as the correlation between the two methods, were quantified with the Intraclass Correlation Coefficient. Results The average lateral ER was 0.32 (± 0.04) in X-ray and 0.32 (± 0.04) in CT. On the medial side, the average ER was 0.34 (± 0.04) in X-ray and 0.35 (± 0.04) in CT. The interobserver agreement for the same imaging modality was lateral 0.81 and medial 0.81 in X-ray as well as lateral 0.74 and medial 0.85 in CT. The correlation between the two methods was lateral 0.81 and medial 0.79. Conclusions The ER can be reliably determined in X-ray and CT. Measurements of the two image modalities correlate. Prior to rTKA, the sole use of the X-ray is possible., publishedVersion

Realignment of the weightbearing axis by high tibial osteotomy (HTO) can alter the forces acting on the articular cartilage within the knee, reducing the load on the medial compartment. This unloading effect is thought to allow the repair of the articular cartilage of the affected compartment. It is important to evaluate the serial changes of joint space width (JSW) after HTO for assessing the state of the cartilage and the unloading effect by HTO. However, early postoperative knee JSW change is attributable to change in the joint line convergence angle after HTO and may not reflect cartilage regeneration. In addition, the soft tissue laxity of the knee and changes in joint line convergence angle after HTO should be considered for assessing these early postoperative JSW changes.

Prior studies have reported a negative effect on both clinical outcomes and patient-reported outcome measures (PROMS) following joint line elevation (JLE) in cruciate-retaining (CR) total knee arthroplasty (TKA) and posterior stabilized (PS) TKA designs. This experimental study was aimed to quantify the effect of JLE on in vivo knee kinematics in patients with bicruciate retaining (BCR) TKA during strenuous activities. Thirty unilateral BCR TKA patients were evaluated during single-leg deep lunge and sit-to-stand using a validated combined computer tomography and dual fluoroscopic imaging system. Correlation analysis was performed to quantify any correlations between JLE and in vivo kinematics, as well as PROMS. There was a significant negative correlation between JLE and maximum flexion angle during single-leg deep lunge (ρ = −0.34, p = 0.02), maximum varus joint angles during single-leg deep lunge (ρ = −0.37, p = 0.04), and sit-to-stand (ρ = −0.29, p = 0.05). There was a significant negative correlation between JLE and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score (ρ = −0.39, p = 0.01) and knee disability and osteoarthritis outcome score physical function (KOOS-PS; ρ = −0.33, p = 0.03). The JLE that yields a significant loss in PROMS and maximum flexion angles were 2.6 and 2.3 mm, respectively. There was a linear negative correlation of JLE with both in vivo knee kinematics and PROMS, with changes in JLE of greater than 2.6 and 2.3 mm, leading to a clinically significant loss in PROMS and maximum flexion angles, respectively, suggesting an increased need to improve surgical precision to optimize patient outcomes following BCR TKA.

Purpose This study aimed to validate a new joint line measurement technique in total knee arthroplasty for separated assessment of the medial and lateral femoral joint line alteration with 3D-surface scan technology. Separate assessment of the medial and lateral joint line alteration may improve TKA alignment assessment regarding to joint line restoration in kinematic alignment and use of robotic-assisted TKA surgery. Methods The medial and lateral joint line difference after TKA implantation on an artificial bone model was analyzed and compared with a 3D-scan and full femoral radiographs pre- and postoperatively. Radiographic analysis included the perpendicular distance between the most distal point of the medial and lateral condyle and the reproduced preoperative lateral distal femoral angle (LDFA). For evaluation of validity and reliability, radiographs were captured initially with true anteroposterior view and subsequently with combined flexion and rotation malpositioning. Reliability of the introduced measurement technique in between three observers was tested with intraclass correlation coefficient (ICC). Results Radiographic measurement showed a mean difference of 0.9 mm on the medial side and 0.6 mm on the lateral side when compared to the 3D-surface scan measurement. The reliability of measurement accuracy was ≤ 1 mm in x-rays with Conclusion The new introduced joint line measurement method showed a sufficient reliability, accuracy and precision. It provides separated information about medial and lateral joint line alteration in TKA surgery in absolute values. Level of evidence V - Experimental Study

Background Preservation of joint line height is an important factor in post-operative function after Total Knee Arthroplasty (TKA). This is the first study investigating the reliability of the novel Imperial Joint Line Congruency Measurement (IJLCM) technique for the assessment of joint line height using plain radiographs. Methods The reliability of two techniques used to measure joint line height on pre-operative and post-operative plain radiographs is presented. 120 patients that underwent TKA from 6 different international centres were included. Measurements were performed using each technique by two senior orthopaedic surgeons at two different timepoints (test-retest). Two undergraduate medical students performed joint line measurements using the most reproducible of the two techniques on 40 pre-operative and post-operative images to establish the reliability of the measurement technique. Results The IJLCM demonstrated an average absolute difference of 1.83mm (CI 1.56–2.10mm) and excellent inter and intra-rater reliability between senior orthopaedic surgeons (>0.92 (CI 0.88–0.94) when measuring joint line height on plain radiographs. Overall Crohnbach’s alpha over 0.92 confirmed internal consistency. Measurements performed using the control technique as previously described by Figgie et al. had an average absolute difference of 5.75mm (5.17–6.32mm). Comparison of measurements by senior orthopaedic surgeons and medical students using the IJLCM technique with ANOVA and student’s t-test demonstrated acceptable agreement and inter-rater reliability of >0.92 (0.87–0.95). Conclusion This study shows excellent accuracy, precision, and reliability of the novel IJLCM technique. Furthermore, excellent agreement between senior orthopaedic surgeons and medical students when using the IJLCM could be shown. The IJLCM technique is reliable for joint line assessment.

Joint line (JL) restoration is one of the major challenges in revision total knee arthroplasty (rTKA). There is debate regarding the most reliable methodology for the assessment of JL level during revision surgery. Among the strategies, the use of adductor tubercle (AT) as an anatomical landmark has been proposed. The purpose of this paper is to systematically review the available literature to understand the reliability of AT ratio to identify the JL, and the advantages and drawbacks of its application. A research was performed on the PubMed, Embase, Cochrane and Google Scholar databases based on the following inclusion criteria for articles' selection: (I) clinical reports of any level of evidence, (II) written in the English language, (III) published from 2010 to 2020, (IV) dealing with the use of the adductor tubercle as a landmark to restore JL in revision TKA. All relevant data were extracted by two independent investigators, and discrepancies were resolved by discussion and consensus. A total of 13 studies were included: nine were radiographic evaluations, 3 clinical reports and 1 was an ex-vivo study. Radiographic studies highlighted that AT is a landmark easy to identify, with high intra and inter-observer agreement, irrespective of gender, age and size of the patient. The comparison with other bony landmarks revealed superior reliability in favor of AT. Also during surgical procedures, AT can be safely located and some clinical studies confirmed that AT ratio helps surgeon in re-establishing a correct JL and achieve ligament balancing even in complex revision cases. AT is a reliable and easily detectable landmark, and AT ratio is a valid tool to determine the JL level and help surgeons to restore the JL and simultaneously achieve knee ligament balancing in r-TKA.

We assessed the impact of a minimal medial soft-tissue release with complete peripheral osteophyte removal on the ability to attain manual preresection deformity correction during navigation-assisted total knee arthroplasty (TKA) for varus osteoarthritis. We included 131 TKAs for 109 patients with medial compartment predominant osteoarthritis. The steps for achieving minimal medial soft-tissue release were performed as follows: (1) elevation of a periosteal sleeve to 5-mm distal to the joint line and (2) complete removal of peripheral osteophytes. The evaluation criteria of this study were as follows: (1) age, (2) height, (3) weight, (4) body mass index (BMI), (5) sex, (6) the preoperative femorotibial mechanical angle in the neutral position before medial release and (7) the mechanical angle in maximum manual valgus stress after the two-step medial-release procedure (measured on the navigation screens). Multiple regression analysis of the criteria was performed to determine the degree of varus deformity that allowed neutral alignment but required extensive medial release. The femorotibial mechanical angle in the neutral position before medial release and sex correlated with the mechanical angle in maximum manual valgus stress on the navigation screen after medial release (r = 0.72, p

There is a tendency of orthopaedic surgeons to elevate joint line (JL) in revision total knee arthroplasty (RTKA). Here, we ascertain the use of the spacer block tool (SBT) to determine JL more accurately for less experienced RTKA surgeons. To perform more precise restoration of JL, an SBT with markers was developed and produced using computer software and three-dimensional printers. The study was planned prospectively to include patients who received either condylar constrained or rotating hinge RTKA between January 2016 and December 2019. To determine JL, distance from fibular head (FH), adductor tubercle (AT), and medial epicondyle (ME) were measured on contralateral knee preoperative radiographs and on operated knee postoperative radiographs. Patients were randomized and grouped according to the technique of JL reconstruction. In Group 1, conventional methods by evaluating aforementioned landmarks and preoperative contralateral knee measurements were used to determine JL, whereas in Group 2, the SBT was used. The main outcome measure was the JL change in revised knee postoperatively in contrast to contralateral knee to compare effective restoration of JL between the groups. Twenty-five patients in Group 1 (3 males, 22 females, 72 years, body mass index [BMI] 32.04 ± 4.45) and 20 patients (7 males, 13 females, 74 years, BMI 30.12 ± 5.02) in Group 2 were included in the study. JL measurements for the whole group were FH-JL = 18.3 ± 3.8 mm, AT-JL = 45.8 ± 4.6 mm, and ME-JL = 27.1 ± 2.8 mm preoperatively, and FH-JL = 20.7 ± 4.2 mm, AT-JL = 43.4 ± 5.2 mm, and ME-JL = 24.7 ± 3.1 mm postoperatively. JL level differences in reference to FH, AT, and ME in Group 1 were 3.6 ± 3.1, 3.6 ± 3.5, and 3.4 ± 3.1 mm, respectively, and in Group 2 were 1.0 ± .0.9, 1.3 ± 1.3, and 1.1 ± 1.3 mm, respectively. There were statistically significant differences between the two groups in JL changes referenced to all of the specific landmarks (p

BackgroundThe alignment correction after high tibial osteotomy (HTO) is made both by bony correction and soft-tissue correction around the knee. Change of the joint-line convergence angle (JLCA) represents the soft-tissue correction after HTO, which is the angle made by a tangential line between the femoral condyles and the tibial plateau. We described the patterns of JLCA change and related factors after HTO and investigated the appropriate preoperative planning method.MethodsEighty patients who underwent HTO between 2013 and 2016 were included for this retrospective study. Standing, whole-limb radiograph, supine knee anteroposterior (AP) and lateral were measured on the preoperative and postoperative radiographs. The patterns of JLCA changes and related factors were analyzed.ResultsJLCA decreased by a mean of 0.9° ± 1.2° (P P P P ConclusionsSurgeons should consider the effect of the JLCA change during the preoperative planning and intraoperative procedure to avoid unintended overcorrection.

Background: Discrepancies in bone resection between the medial and lateral compartments is very common in total knee replacement (TKA) when mechanical alignment (MA) is used. The purpose of this study was to explore whether and how joint line orientation affects the gross amount of bone resected in mechanically aligned TKA.Methods: A total of 112 patients (137 knees) diagnosed with osteoarthritis (OA) were included. Bone resection simulations were conducted in the coronal view using full-length weight-bearing radiographs per the technical parameters of MA, and the feasibility of simulated osteotomy was verified via intraoperative caliper measurement. Correlation and regression analyses were conducted comparing the amount of bone resected and various parameters, including hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), joint line congruency angle (JLCA), and medial proximal tibial angle (MPTA). Moreover, any intraoperative bone resection adjustments that were made were retrospectively collected using a medical record query system.Results: All knees in the current case series could be artificially divided into 4 subgroups: 84 varus knees (61.3%) with valgus femurs in subgroup 1, 32 varus knees (23.4%) with varus femurs in subgroup 2, 14 valgus knees (10.2%) with varus tibias in subgroup 3, and 7 valgus knees (5.1%) with valgus tibias in subgroup 4. Simulated bone resection thickness was highly consistent with intraoperative measurements. MPTA and mLDFA were positively correlated with the amount of bone resected in subgroup 1. The regression equation was: Maximum resection thickness (mm) = 0.556*mLDFA (deg.) + 0.098*MPTA (deg.) -39.74; R2=0.808. Similarly, intraoperative bone resection adjustments also showed a correlation with mLDFA in subgroup 1.Conclusions: Deformities in knee OA can be divided into 4 subgroups based on the alignment of extremities and the joint line orientation. When TKA is performed in varus knees with valgus femurs using conventional instruments and mechanical alignment techniques, the amount of bone resected in the coronal plane demonstrates a linear relationship with the patient’s mLDFA.

INTRODUCTION Functional alignment (FA) in total knee arthroplasty (TKA) has been introduced to restore the native joint line obliquity, respect the joint line height and minimize the need of soft tissue releases. The purpose of this study was to assess the intraoperative joint line alignment and compare it with the preoperative epiphyseal orientation of the femur and tibia in patients undergoing robotic-arm-assisted (RA)-TKA using FA. MATERIALS AND METHODS This retrospective study included a consecutive series of patients undergoing RA-TKA between February 2019 and February 2021. The joint line orientation of the femur and tibia in the three-dimensions was calculated and classified on preoperative CT-scans and compared with the intraoperative implant alignment. The tibial cut was performed according to the tibial preoperative anatomy. The femoral cuts were fine-tuned based on tensioned soft tissues, aiming for balanced medial and lateral gaps in flexion and extension. RESULTS A total of 115 RA-TKAs were assessed. On average, the tibial component was placed at 1.8° varus (SD 1.3), while the femur was placed at 0.8° valgus (SD 2.2) and 0.6° external rotation (SD 2.6) relative to the surgical transepicondylar axis. Moderate to strong, statistically significant relationships were described between preoperative tibial coronal alignment and tibial cut orientation (r = 0.7, p