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This study aimed to investigate the clinical outcomes of fixed-bearing medial unicompartmental knee arthroplasty (UKA) for tibia vara knees and the associated changes in joint space malalignment (JSM) and joint line obliquity (JLO). We retrospectively analyzed a consecutive group of 100 patients who underwent fixed-bearing medial UKA with a preoperative medial proximal tibia angle (MPTA) ≥86° (n = 50) and MPTA <86° (n = 50) and who had a minimum 5-year follow-up. Radiological parameters, including the hip-knee-ankle angle, MPTA, and the postoperative JSM and JLO, were measured. Functional evaluation was performed using the range of motion, visual analog scale, Knee Society Knee Score, Knee Society Function Score, and Western Ontario and McMaster Universities Osteoarthritis Index score. The MPTA <86° group showed significantly higher postoperative JLO (91.8 versus 90.4°, respectively; P =.002) and JSM (6.1 versus 4.2°, respectively; P =.026) compared to the MPTA ≥86° group. Functional outcomes, including range of motion, visual analog scale, Knee Society Knee Score, Knee Society Function Score, and Western Ontario and McMaster Universities Osteoarthritis Index scores, were not significantly different between the 2 groups. Fixed-bearing medial UKA is a safe and effective surgical option for patients who have tibia vara knees, as an increase in JLO and JSM postoperatively does not have a clinically relevant impact, even after a minimum 5-year follow-up. [ABSTRACT FROM AUTHOR]

Two related recent reports described high error rates for implant positioning and reduced implant survivorship in manual unicompartmental knee arthroplasty (MUKA) compared to robotic-assisted unicompartmental knee arthroplasty (RUKA). The present study scientifically replicated these reports by comparing MUKAs similarly performed by an experienced high-volume surgeon in similar patients using the same study methods as these reports. A total of 216 consecutive MUKAs were retrospectively evaluated radiographically for achievement of implant positioning targets. Achievement of targets was compared to the published MUKA and RUKA outcomes and correlated with revision rates and patient-reported outcome measures. There were 20% of study MUKAs compared to 88.1% of comparison MUKAs (P <.001) and 31.4% of comparison RUKAs (P <.048) that failed to meet all 7 implant positioning targets. The MUKA revision rates were significantly lower in the study sample than for comparison MUKAs (3.2% versus 14.2%, P <.001). Implant survivorship was 91.7% (95% confidence interval 84.9, 98.5%) at 8.9 years compared to 70.0% (95% confidence interval 56.0, 80.0%) at 10.2 years, respectively. Most patient-reported outcome measures did not differ based on achievement of implant positioning targets (P ≥.072). Present study findings indicate that observations in the 2 recent reports may not be generalizable to all UKA surgeons. Additional data on the relationship between implant positioning and revision as well as functional outcomes are needed to identify appropriate robotic arthroplasty applications. [ABSTRACT FROM AUTHOR]

The factors affecting results after bicompartmental knee arthroplasty (BiKA) have not been fully elucidated. This major ligament-preserving procedure may be more susceptible to overstuffing of the patello-femoral (PF) joint than the major ligament-sacrificing total knee arthroplasty. Currently, we investigated the effect of PF overstuffing after BiKA on its clinical outcome. There were 71 patients (74 knees) who underwent modular unlinked BiKA at our clinic who had a follow-up of 5 to 9 years. Final follow-up results were assessed by evaluating knee range of motion, the 2011 Knee Society Score (2011KSS), Japanese Knee Osteoarthritis Measure, and radiological findings. The degree of postoperative PF overstuffing was evaluated by computed tomography and magnetic resonance images for 55 knees, and the correlation between the degree of overstuffing and postoperative clinical results were examined. Overall clinical results improved significantly after surgery without any revision cases. The X-ray measurements showed the improved coronal alignments and the appropriate implant installation angles. Higher degree of postoperative PF overstuffing caused by insufficient amount of osteotomy on the anterior surface of the femur correlated with worse postoperative total 2011KSS at 2 years after surgery (Spearman's rank correlation coefficient (rs) = −0.387, P =.004), as opposed to no correlation at the time of the final follow-up (Spearman's rank correlation coefficient = 0.068, P =.623). Modular unlinked BiKA provided patients with a high level of satisfaction and functional improvement over 5 to 9 years postoperatively. However, because PF overstuffing affects initial patient satisfaction, the amount of osteotomy should be determined carefully during the surgery. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to assess phenotypic variation in the coronal plane of knees with anteromedial osteoarthritis using the functional knee phenotype classification, before and after treatment with medial unicompartmental knee arthroplasty (UKA). Methods: The study comprised 1000 knees of 835 patients (45% females, 55% males, 90% Caucasian) who underwent medial UKA for anteromedial osteoarthritis. Pre and postoperative alignment was evaluated through the hip‐knee‐ankle angle (HKA), femoral mechanical angle (FMA), and tibial mechanical angle (TMA). Knees were classified according to the functional knee phenotype system which combines limb phenotype (HKA), and femoral and tibial knee phenotypes (FMA and TMA, respectively). Restoration of prearthritic coronal alignment following medial UKA was evaluated by phenotype. Results: Preoperatively, 76 distinct and 25 relevant (prevalence ≥1%) functional knee phenotypes were identified, of which VARHKA6°VARFMA3°NEUTMA0° was the most common (9.4% of knees). The most prevalent limb phenotype, VARHKA6°, comprised 15 distinct knee phenotypes (FMA and TMA combinations). Postoperatively, 58 distinct and 17 relevant functional knee phenotypes were observed, of which VARHKA3°NEUFMA0°NEUTMA0° had the highest prevalence at 18.3%. Knees with combined tibial and femoral deformities were associated with a lower probability of restoration of prearthritic coronal alignment following medial UKA, compared to knees without extra‐articular deformity, or knees with an isolated tibial or femoral deformity. Conclusion: Phenotype analysis using the functional knee phenotype system demonstrated a wide diversity of coronal alignment phenotypes among knees with anteromedial osteoarthritis in a predominantly Caucasian population. Following medial UKA, a reduction from 25 preoperative to 17 postoperative relevant phenotypes was observed. Consideration of phenotypic variation can be of importance when aiming to restore prearthritic coronal alignment during medial UKA. Level of Evidence: Level III, retrospective cohort study. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to demonstrate the clinical utility of controlled posterior condylar milling (CPCM) in gap balancing while minimally resecting the tibia during fixed‐bearing unicompartmental knee arthroplasty (UKA). Methods: This study is a retrospective cohort study. Patients who underwent medial UKA for isolated medial compartment osteoarthritis with a minimum follow‐up of 2 years were included. The patients were divided into two groups: the conventional group (n = 56) and the CPCM group (n = 66). In the CPCM group, the proximal tibia was resected at the level of the distal end of the subchondral bone. If the flexion gap was tighter than extension, the posterior condyle was additionally milled to adjust gap tightness. Standing knee X‐ray and scanogram were used to evaluate alignment and tibia resection amount. Range of motion (ROM) and Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) scores were used to evaluate clinical outcomes. Results: The CPCM group showed significantly smaller tibia resection (3.6 ± 1.9 mm) compared to the conventional group (5.2 ± 2.7 mm) (p < 0.001). Postoperative ROM (133.0 ± 8.3°, 135.2 ± 7.2°, n.s.) and WOMAC (19.3 ± 13.6, 23.6 ± 17.7, n.s.) were not significantly different between the two groups. Postoperative periprosthetic fractures occurred in two patients in conventional group, while the CPCM group had no periprosthetic fractures. Conclusion: The CPCM technique may be a simple and useful intraoperative technique that can achieve minimal tibia resection and promising clinical outcomes while easily adjusting gap tightness between flexion and extension during medial fixed‐bearing UKA. Level of Evidence: Level III. [ABSTRACT FROM AUTHOR]

Objective To conduct a comparative stress analysis of polyethylene inserts and tibial plateaus during unicompartmental knee arthroplasty with mobile platform, specifically focusing on two posterior slopes of the tibial component and three positions of the femoral component in order to provide a reference for the optimal placement of the prosthesis.Methods Finite element models of normal knee joints and unicompartmental knee arthroplasty with mobile platform were developed using software such as Mimics, Solidwork, and Geomagic Studio. In the Magics software, we simulated the unicompartmental knee replacement surgery, and adjusted the tibial component posterior slope to 0° and 7°. The femoral component was placed at three locations: the center of the medial condyle of femur, shifted 5 mm inward, and shifted 5 mm outward. Stress values and distribution on polyethylene inserts and tibial plateaus were observed at knee flexion angles of 0°, 30°, 60°, and 90°. Results When the tibial component had posterior slopes of 0° and 7°, compared to placing the femoral component 5 mm inward, positioning it at the center and 5 mm outward resulted in significantly lower stress values on both polyethylene inserts and tibial plateaus (all P＜0. 05) . When the femoral component was placed at the center and 5 mm outward positions, the stress distribution on polyethylene inserts and tibial plateaus was found to be uniform. With an increase in the posterior slope of the tibial component, there was no significant alteration in stress on polyethylene inserts and tibial plateaus. Conclusion In the unicompartmental knee arthroplasty, when the femoral component is placed at the center of the medial condyle of femur or slightly outward, and the posterior slope of the tibial component is controlled at 0°to 7°, the stress value of the polyethylene insert and the tibial plateau is the smallest, and the stress distribution is uniform. [ABSTRACT FROM AUTHOR]

Introduction: Few information has been published on the survival of unicompartmental knee arthroplasty (UKA) and fixed-bearing tibial components. The aim of this study is to analyze if UKA survival varies according to UKA model used and to analyze the possible risk factors for UKA revision. Materials and methods: A retrospective study analyzing 301 UKAs (ACCURIS, all-polyethylene tibial component, 152; Triathlon PKR, metal-backed tibial component, 149) was performed. Demographic parameters as well as implant survival and cause of prosthetic revision were analyzed. The Kaplan–Meier survival analysis, the log-rank test and the Cox multiple regression were used for the analysis. Results: Average follow-up was 8.1 ± 3.08-years. Average age was 68.1 ± 8.6-years; 70.4% of subjects were women. The ACCURIS UKA group had a UKA revision rate higher compared to the Triathlon PKR group (16/152, 10.6% vs 5/149, 3.4%, respectively; p < 0.001). The main cause of prosthetic revision was aseptic loosening (5/21, 23.8%). All aseptic loosening cases and tibial component collapse were reported with the ACCURIS UKA group. Overall UKA survival was 98.01% (95% CI 95.62–99.1) at 1-year, 94.27% (95% CI 90.95–96.4) at 5-years and 92.38% (95% CI 88.48–94.99) at 10-years' follow-up. There were no differences in the Kaplan–Meier survival curves regarding operated side or affected tibiofemoral compartment (log-rank test = 0.614 and 0.763, respectively). However, Kaplan–Meier survival curve according to UKA model used was different (log-rank test = 0.033). The metal-backed component appeared to be a protector factor for UKA revision when adjusted for age, sex, operated side, and affected tibiofemoral compartment (Hazard Ratio 0.32, p = 0.031). Conclusion: Fixed-bearing UKAs showed excellent mid- and long-term survival rates. Aseptic loosening is the main cause of implant failure. PKR group (metal-backed component) seem to be a protector factor to UKA revision when it was compared with ACCURIS UKA group (all-polyethylene tibial component). [ABSTRACT FROM AUTHOR]

Background: The relationship between the severity of preoperative varus deformity and the amount of its correction in unicompartmental knee arthroplasty (UKA) as well as the thickness of the insert has not been well known.Methods: One hundred and three patients who underwent medial fixed-bearing UKA with the use of the spacer block method were assessed. After the component gap in extension was measured using a UKA tensor, the pre-osteotomy gap was calculated from the thickness of the bone cuts. The relationship between the preoperative hip-knee-ankle (HKA) angle as well as the pre-osteotomy gap and the amount of change in HKA angle were analysed. Also, preoperative HKA angle and the thickness of the bone cuts were compared among groups by the insert thickness.Results: The mean preoperative HKA angle was 7.7 ± 3.1° varus. Patients with more varus deformity and those with a wider pre-osteotomy gap showed a more valgus change in HKA angle. As for the thickness of the insert, the preoperative HKA angle of the patients with the thinnest insert was significantly smaller (less varus) than that of those with the thicker insert while no statistically significant difference was found among the insert groups regarding the amount of the bone cuts.Conclusions: The severity of the preoperative varus deformity as well as the intraoperative pre-osteotomy gap related to the amount of change in HKA angle. As thick inserts tended to be used in severe varus knees, the tibial bone cut can be reduced in such cases. [ABSTRACT FROM AUTHOR]

Purpose: Purpose of this study is to compare the short-term results of unicompartmental knee arthroplasty applied stable knees regardless of the condition of the ACL and the application of unicompartmental knee arthroplasty and ACL reconstruction combined surgery applied to ACL deficient cases with anterior instability and to identify the condition and function of the ACL for success in this surgery. Patients and Methods: 80 out of the 105 patients who were operated in 2013-2015 and came for follow-up were included in the study and the patients were divided into four groups. The VAS pain score, KSS Score, WOMAC score, OKS questionnaires and joint range of motion measurements were conducted pre-operatively and post-operatively. One leg standing test, joint position sense measurement, and isokinetic muscle strength test were performed in post-operative controls. Results: There was no statistically significant difference between the demographic data and follow-up of the groups (p>0.05). While there was a statistically significant difference in knee flexion between Group 2-Group 4 and Group 3-Group 4 in the pre-operative period, no difference was found in the post-operative period (p>0.05). While there was no difference among the groups, knee joint range of motion in direction of extension declined in a statistically significant way in all four groups (p<0.05). Pain felt postoperatively was the most in Group 1 and the least in Group 3. A statistically significant difference was found between Group 1 and Group 3 in the test performed with the eyes closed (p<0.05). Conclusion: The presence of a functional anterior cruciate ligament is expected to make a positive contribution to surgical results especially in young patients with high activity expectation. Whether the patient's ACL rupture is primary or secondary and his/her activity expectation should be effective in the choice of a surgical method. [ABSTRACT FROM AUTHOR]

Unicompartmental knee arthroplasty (UKA) represents a treatment option to address knee pain deriving from either the medial or lateral compartment of the knee. Compared to total knee arthroplasty, UKA offers the advantages of preserving native bone stock, offering less surgical exposure and risks, and better restoring native knee kinematics. The UKA is a specialized procedure that has its best outcomes in the hands of an experienced surgeon who performs UKA repeatedly and with proper patient selection. In this review, we discuss current concepts for both medial UKA and lateral UKA with regard to indications, isolated knee compartment osteoarthritis clinical and radiographic work-up, surgical approaches, and patient outcomes, as well as analyzing the differences between fixed-bearing and mobile-bearing implant designs. [ABSTRACT FROM AUTHOR]

Change in leg length and leg-length discrepancy (LLD) are common concerns among patients undergoing medial unicompartmental knee arthroplasty (UKA). This study aimed to quantify the magnitude of leg-length change, prevalence of postoperative LLD, and their clinical implications following medial UKA. Leg length and mechanical hip-knee-ankle angle (mHKA) were retrospectively measured in 332 patients following unilateral robotic-arm assisted medial UKA for medial compartment osteoarthritis, using calibrated long-leg radiographs. The Knee Injury and Osteoarthritis Otcome Score for Joint Replacement and patient satisfaction were analyzed to assess impact of leg-length change and LLD on outcomes. Following medial UKA, median leg-length change was 2.0 mm (interquartile range, −1.0 to 5.0 mm; P <.001) with a mean correction in mHKA of 4.4° ± 2.7 (P <.001). A total of 158 patients (48%) had a leg-length increase by 0 to 5 mm, 64 (19%) by 6 to 10 mm, and 11 (3%) by >10 mm. Leg-length change was positively correlated with mHKA correction (R = 0.44, P <.001). Postoperatively, moderate (5 to 10 mm) and substantial LLD (≥10 mm) were present in 49% and 17% of patients, respectively. Four-year Knee Injury and Osteoarthritis Outcome Score for Joint Replacement were comparable between patients with and without substantial postoperative LLD (P =.976). Proportions of satisfied patients were similar between groups (P =.687). Following medial UKA, the majority of patients had a moderate increase in leg length, the magnitude of which was positively correlated to the correction in mechanical alignment. Postoperative substantial LLD was not uncommon (17% prevalence); however, it had no significant impact on patient-reported outcomes or satisfaction at 4 years follow-up. [ABSTRACT FROM AUTHOR]

We report a case of previously undescribed medial unicompartmental knee arthroplasty failure due to femoral component implant fracture. The patient experienced sudden pain and locking while ambulating 8 years postoperatively. Radiographs revealed catastrophic femoral component failure with a transverse break through the metal. The patient underwent revision to total knee arthroplasty. At 1-year follow-up, the patient had no pain and a range of motion of 130 degrees. Particular attention should be paid to obtaining adequate femoral component posterior flange fixation during unicompartmental knee arthroplasty. Patient education regarding maintaining a healthy weight is crucial to preventing this complication.

Abstract Background To investigate whether patient-specific instrumentation (PSI) improves the femoral component positioning of implants during unicompartmental knee arthroplasty (UKA) using cadaver bone models. Methods Fifty adult cadaveric femoral bone specimens collected from February 2016–2018, were randomized to receive medial UKA with a PSI guide (n = 25) or conventional instrumentation (CI) (n = 25). Standard anteroposterior and lateral view radiographs were obtained postoperatively to assess the coronal and sagittal positioning of the femoral prostheses, respectively. The osteotomy time was recorded to assess the convenience of PSI in guiding osteotomy. Results Osteotomy time significantly shortened in the PSI group (3.12 ± 0.65 versus 4.33 ± 0.73 min, p

Purpose: Outcomes after combination of anterior cruciate ligament (ACL) reconstruction (ACLR) with unicompartmental knee arthroplasty (UKA) or high tibial osteotomy (HTO) have been widely reported, but previous systematic reviews have included articles published before 2000 and do not necessarily reflect recent trends. We conducted a thorough investigation to address (1): What are the recent surgical trends in simultaneous ACLR and UKA or HTO? and (2) What are the issues in these surgeries? based on a comprehensive systematic analysis. Methods: A systematic surveillance was performed in accordance with the PRISMA guideline. The inclusion criteria were as follows: simultaneous ACLR and UKA or HTO for medial osteoarthritis (OA) with ACL deficiency; clinical outcomes and complications recorded; publication date after 2000.A total of 1466 potentially relevant articles were identified; after exclusions, 31 articles that included 744 knees were analyzed. Fourteen articles included 330 knees underwent simultaneous ACLR and UKA (UKA group) and 17 articles included 414 knees underwent simultaneous ACLR and HTO (HTO group). Results: Overall, complications were found in 14 knees (4.2%) in the UKA group and 47 knees (11.3%) in the HTO group. Re-rupture of the ACL was observed in only the HTO group (6 knees: 1.4%). Revision to TKA occurred in 8 knees (2.4%) in the UKA group and 1 knee (0.2%) in the HTO group. No standardized outcome measures for clinical assessment were used for all studies. Conclusion: The systematic surveillance of studies published since 2000 on the outcomes and complications of simultaneous ACLR and UKA or HTO for medial OA with ACL deficiency indicates an increasing number of reports on simultaneous ACLR and HTO or UKA in recent years. Favorable clinical results were achieved in both treatment groups.

Aims: The aim of this study was to describe the pattern of revision indications for unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) and any change to this pattern for UKA patients over the last 20 years, and to investigate potential associations to changes in surgical practice over time. Methods: All primary knee arthroplasty surgeries performed due to primary osteoarthritis and their revisions reported to the Danish Knee Arthroplasty Register from 1997 to 2017 were included. Complex surgeries were excluded. The data was linked to the National Patient Register and the Civil Registration System for comorbidity, mortality, and emigration status. TKAs were propensity score matched 4:1 to UKAs. Revision risks were compared using competing risk Cox proportional hazard regression with a shared γ frailty component. Results: Aseptic loosening (loosening) was the most common revision indication for both UKA (26.7%) and TKA (29.5%). Pain and disease progression accounted for 54.6% of the remaining UKA revisions. Infections and instability accounted for 56.1% of the remaining TKA revision. The incidence of revision due to loosening or pain decreased over the last decade, being the second and third least common indications in 2017. There was a decrease associated with fixation method for pain (hazard ratio (HR) 0.40; 95% confidence interval (CI) 0.17 to 0.94) and loosening (HR 0.29; 95% CI 0.10 to 0.81) for cementless compared to cemented, and units UKA usage for pain (HR 0.67, 95% CI 0.50 to 0.91), and loosening (HR 0.51; 95% CI 0.37 to 0.70) for high usage. Conclusion: The overall revision patterns for UKA and TKA for the last 20 years are comparable to previous published patterns. We found large changes to UKA revision patterns in the last decade, and with the current surgical practice, revision due to pain or loosening are significantly less likely. Cite this article: Bone Jt Open 2023;4(12):923–931.

Aims: Unicompartmental knee arthroplasty (UKA) is the preferred treatment for anterior medial knee osteoarthritis (OA) owing to the rapid postoperative recovery. However, the risk factors for UKA failure remain controversial. Methods: The clinical data of Oxford mobile-bearing UKAs performed between 2011 and 2017 with a minimum follow-up of five years were retrospectively analyzed. Demographic, surgical, and follow-up data were collected. The Cox proportional hazards model was used to identify the risk factors that contribute to UKA failure. Kaplan-Meier survival was used to compare the effect of the prosthesis position on UKA survival. Results: A total of 407 patients who underwent UKA were included in the study. The mean age of patients was 61.8 years, and the mean follow-up period of the patients was 91.7 months. The mean Knee Society Score (KSS) preoperatively and at the last follow-up were 64.2 and 89.7, respectively (p = 0.001). Overall, 28 patients (6.9%) with UKA underwent revision due to prosthesis loosening (16 patients), dislocation (eight patients), and persistent pain (four patients). Cox proportional hazards model analysis identified malposition of the prostheses as a high-risk factor for UKA failure (p = 0.007). Kaplan-Meier analysis revealed that the five-year survival rate of the group with malposition was 85.1%, which was significantly lower than that of the group with normal position (96.2%; p < 0.001). Conclusion: UKA constitutes an effective method for treating anteromedial knee OA, with an excellent five-year survival rate. Aseptic loosening caused by prosthesis malposition was identified as the main cause of UKA failure. Surgeons should pay close attention to prevent the potential occurrence of this problem. Cite this article: Bone Jt Open 2023;4(12):914–922.

Abstract Background Bicruciate-retaining (BCR) prosthesis has been introduced to recreate normal knee movement by preserving both the anterior and posterior cruciate ligaments. However, the use of BCR total knee arthroplasty (TKA) is still debatable because of several disappointing reports. We have been performing BCR TKAs with personalized alignment (PA). This study aimed to reveal the limb alignment and soft tissue balance of FA-BCR TKAs and compare the clinical outcomes of FA-BCR TKAs with those of unicompartmental knee arthroplasty (UKA). Methods Fifty BCR TKAs and 58 UKAs were included in this study. The joint component gaps of BCR TKA were evaluated intraoperatively and the postoperative hip–knee–ankle (HKA) angle, medial proximal tibial angle (MPTA), and lateral distal femoral angle (LDFA) were measured using full-length standing radiography. The short-term clinical outcomes of BCR TKAs were compared with those of UKA using the scoring system of 2011 Knee Society Scoring (KSS) and the knee injury and osteoarthritis outcome score (KOOS) at an average of 2 years postoperatively (1-4yeras). Results The coronal alignment values of PA-BCR TKA were as follows: HKA angle, 177.9° ± 2.3°; MPTA, 85.4° ± 1.9°; and LDFA, 87.5° ± 1.9°. The joint component gaps at flexion angles of 10°, 30°, 60°, and 90° were 11.1 ± 1.2, 10.9 ± 1.4, 10.7 ± 1.3, and 11.2 ± 1.4 mm for the medial compartment and 12.9 ± 1.5, 12.6 ± 1.8, 12.5 ± 1.8 and 12.5 ± 1.7 mm for the lateral compartment, respectively. The patient expectation score and maximum extension angle of PA-BCR TKA were significantly better than those of UKAs. Conclusions The short-term clinical outcomes of PA-BCR TKA were comparable or a slightly superior to those of UKAs.

AbstractBackground Infections are rare and poorly studied complications of unicompartmental knee arthroplasty (UKA) surgery. They are significantly less common compared to infections after total knee arthroplasties (TKAs). Optimal management of periprosthetic joint infections (PJIs) after a UKA is not clearly defined in the literature. This article presents the results of the largest multicentre clinical study of UKA PJIs treated with Debridement, Antibiotics and Implant Retention (DAIR).Materials and Methods In this retrospective case series, patients presenting between January 2016 and December 2019 with early UKA infection were identified at three specialist centres using the Musculoskeletal Infection Society (MSIS) criteria. All patients underwent a standardized treatment protocol consisting of the DAIR procedure and antibiotic therapy comprising two weeks of intravenous (IV) antibiotics followed by six weeks of oral therapy. The main outcome measure was overall survivorship free from reoperation for infection.Results A total of 3225 UKAs (2793 (86.2%) medial and 432 (13.8%) lateral UKAs) were performed between January 2016 and December 2019. Nineteen patients had early infections necessitating DAIR. The mean follow-up period was 32.5 months. DAIR showed an overall survivorship free from septic reoperation of 84.2%, with overall survivorship free from all-cause reoperation of 78.95%.The most common bacteria were Coagulase-negative Staphylococci, Staphylococcus aureus and Group B Streptococci. Three patients required a second DAIR procedure but remained free from re-infection at follow-up obviating the need for more demanding, staged revision surgery.Conclusions In infected UKAs, the DAIR procedure produces a high rate of success, with a high survivorship of the implant.Key messagesDebridement, Antibiotics and Implant Retention (DAIR) is a successful and minimally invasive surgical option for the management of periprosthetic joint infections (PJIs) after UKA.The surface area available for bacteria to colonise is much smaller in UKAs compared to total knee arthroplasties (TKAs), and this may account for the higher success rates of the DAIR procedure in infected UKAs versus infected TKAs.A second DAIR procedure can be considered in the management of the early recurrence of PJIs with a well-fixed UKA.

Abstract Background Different posterior inclinations of tibial component after unicompartmental knee arthroplasty (UKA) may lead to different biomechanical characteristics of the knee joint. This finite element study was designed to investigate the tibiofemoral contact pressures after UKA with different posterior inclinations of tibial component. Methods Finite element model of a healthy knee joint was constructed, and mobile-bearing (MB) UKA models with 5 different posterior inclinations (3°, 5°, 7°, 9° and 11°) of tibial components were simulated. The maximum contact pressures of tibial plateau cartilage in the lateral compartment and polyethylene insert in the medial compartment were calculated based on the ground reaction force and the angle of the knee flexion obtained by 3D motion capture system. Results The loading ratio of medial and lateral compartments during standing stance (medial 54.49%, lateral 45.51%) and tibial anterior displacement (134 N, 3.89 mm) of healthy knee was basically consistent with previous experimental data. The maximum contact pressures of the medial meniscus and lateral tibial plateau cartilage of the healthy knee during standing stance were 2.14 MPa and 1.57 MPa, respectively. At the static standing phase, the maximum contact pressures of the polyethylene insert decreased from 17.90 to 17.29 Mpa, and the maximum contact pressures of the tibial plateau cartilage in the lateral compartment increased from 0.81 to 0.92 Mpa following an increase in the posterior inclination of the tibial component. At the first peak of ground reaction force, the maximum contact pressures of polyethylene insert increased from 22.37 to 25.16 MPa, and the maximum contact pressures of tibial plateau cartilage in the lateral compartment increased from 3.03 to 3.33 MPa, with the increase in the posterior inclination of the tibial component. At the second peak of ground reaction force, the maximum contact pressures of polyethylene insert decreased from 2.34 to 2.22 MPa with the increase in posterior inclination of tibial component. Conclusion The preoperative and postoperative finite element models of MB UKA were well established. The results showed that the maximum contact pressures of the polyethylene insert did not change significantly with the increase in the posterior inclination of the tibial prosthesis, while the maximum contact pressures of the tibial plateau cartilage of the lateral compartment increased when the posterior inclination of the tibial prosthesis was > 7°. Our results also show that the maximum contact pressures were greater with an excessive inclination angle (11°) of the tibial component, and the pressures of the tibial plateau cartilage in the lateral compartment were more concentrated on the posterior area. This study, therefore, proposes that excessive osteotomy should be avoided.

Abstract Introduction Unicompartmental knee arthroplasty (UKA) is an effective surgical treatment for medial compartment arthritis of the knee, yet surgical outcomes are directly related to surgical execution. Robotic arm-assisted surgery aims to address these difficulties by allowing for detailed preoperative planning, real-time intraoperative assessment and haptic-controlled bone removal. This study aimed to compare the clinical and radiological outcomes between conventional manual mobile bearing and robot arm-assisted fixed bearing medial UKA in our local population. Materials and methods This is a retrospective case–control study of 148 UKAs performed at an academic institution with a minimum of 1-year follow-up. 74 robotic arm-assisted UKAs were matched to 74 conventional UKAs via propensity score matching. Radiological outcomes included postoperative mechanical axis and individual component alignment. Clinical parameters included a range of motion, Knee Society knee score and functional assessment taken before, 6 and 12 months after the operation. Results Robot arm-assisted UKA produced a more neutral component coronal alignment in both femoral component (robotic -0.2 ± 2.8, manual 2.6 ± 2.3; P = 0.043) and tibial component (robotic -0.3 ± 4.0, manual 1.7 ± 5.3; P

Background and Objectives: The ten-year survivorship of unicompartmental knee arthroplasty (UKA) is up to 96%, varying from implants and hospitals; however, most of registry studies do not distinguish between metal-back (MB) tibial implants and all-polyethylene (AP) tibial implants. The aim of the present retrospective clinical study was to analyze the clinical outcomes and survivorship of medial and lateral UKA with a newly designed all-polyethylene tibial plateau at short-term follow-up. Materials and Methods: A retrospective analysis of prospectively collected consecutive patients who underwent medial or lateral UKA with AP tibial plateau was conducted, with a minimum follow-up of 1 year. Primary outcomes were clinical score (VAS, OKS, and KOOS) variations from baseline up to the latest follow-up. Secondary outcomes were Likert scale variations from baseline to the follow-up, evaluation of the influence of demographic factors (age and BMI) at the time of surgery on the clinical outcomes, and evaluation of revision rate up to the last follow-up. Results: The final study population included 99 knees. The mean VAS score for the medial group significantly decreased from 7.61 ± 1.65 (pre-intervention) to 2.74 ± 2.26 (post-intervention). Similar improvements were registered for the OKS as well, for both the medial group (from 22.5 ± 12.6 to 36.6 ± 10.6, with a delta of 14.11 (10.05 to 18.17)) and the lateral group (from 22.6 ± 12.6 to 36.9 ± 11.8, with a delta of 14.24 (8.65 to 19.83)). Moreover, all the KOOS subscales reported an amelioration, both in medial UKA and lateral UKA. Furthermore, a logistic regression of delta VAS was performed in relation to the other clinical questionnaires and the demographic factors. For both medial and lateral UKAs, no statistically significant correlation was found between the VAS scale regression and the demographic factors. The survival rate free from any revision of the cohort at the latest follow-up was 96.32%. Conclusions: All-polyethylene tibial component in unicompartmental knee arthroplasty demonstrates significant improvements in clinical scores and a low failure rate at short-term follow-up.

Abstract Background The cartilage quality of the lateral compartment needs to be clarified prior to medial unicompartmental knee arthroplasty (UKA). Valgus stress radiograph has been recommended as the preferred tool. Some studies also show that magnetic resonance imaging (MRI) has a higher diagnostic value. So, we conducted this study to compare whether valgus stress radiographic lateral joint space width (LJSW) and MRI grading can accurately reflect cartilage quality and its screening value for UKA-suitable patients. Methods One hundred and thirty eight knees proposed for UKA were enrolled prospectively. Valgus stress radiograph was taken to measure LJSW. LJSW > 4 mm was considered normal and suitable for UKA. For weight-bearing area cartilage of lateral femoral condyle, Recht grade was assessed by MRI preoperatively. Recht grades ≤ 2 were treated as non-high-grade injuries while Recht grades > 2 were treated as high-grade injuries. Outerbridge grade was the gold standard and was assessed intraoperatively. Patients with Outerbridge grades 0–2 (non-high-grade injuries) underwent UKA, and patients with Outerbridge grades 3–4 (high-grade injuries) underwent total knee arthroplasty (TKA). The diagnostic parameters of valgus stress radiograph and MRI for the selection of UKA candidates were calculated, and receiver operating characteristic curves were drawn. P

This meta-analysis aimed to assess whether administration tranexamic acid (TXA) could reduce blood loss and vascular events in patients undergoing unicompartmental knee arthroplasty (UKA).We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) and case control trials (CCT) that compared outcomes of patients who did and did not receive TXA during UKA. We searched Cochrane Central Register of including PubMed, EMBASE, Web of Science, the Cochrane Library, Wan Fang data, CBM and CNKI for relevant studies. We assessed the risk of bias of the included studies and calculated pooled risk estimates. The primary outcome was operation time, intraoperative blood loss, postoperative HCT, postoperative HB, transfusion rate, dominant blood loss, postoperative drainage volume, hidden blood loss, total blood loss, postoperative ROM,postoperative VAS score, postoperative complications. Data were using fixed-effects or random-effects models with standard mean differences and risk ratios for continuous and dichotomous variables, respectively.Finally, 9 clinical studies with 744 patients were included in this meta-analysis. Compared with the control group, TXA group could reduced transfusion rate, dominant blood loss, postoperative drainage volume, hidden blood loss, and total blood loss, and increased postoperative HB with statistically significance.The main findings of this meta-analysis are that the transfusion rate, dominant blood loss, postoperative drainage volume, hidden blood loss, total blood loss and postoperative HB in the tranexamic acid group were superior to those in the routine group. Additional high-quality RCTs should be conducted in the future.

Objective Finding reliable tools to predict alignment change after medial mobile‐bearing unicompartmental knee arthroplasty (UKA) can help surgeons avoid under‐ or over‐correction. This prospective study aimed to investigate whether the parameters related to medial collateral ligament tension on valgus stress radiograph can predict the alignment change of medial mobile‐bearing UKA and establish a prediction model. Methods This study prospectively included the patients undergoing medial mobile‐bearing UKA for knee osteoarthritis from November 2018 and April 2021. Patients took valgus stress radiograph and MRI preoperatively and took full‐length weight‐bearing anterior–posterior radiograph of the lower extremity preoperatively and postoperatively. The medial joint space width (MJSW) on valgus stress radiograph, area of femoral and tibial osteophyte on MRI, medial extrusion distance (MED) of the meniscus on MRI, and the change in hip‐knee‐ankle angle (∆HKAA) were measured. Factors influencing ∆HKAA were analyzed by correlation analysis. Univariable and multivariable linear regression analysis was performed to establish a prediction model of ∆HKAA. Results One hundred and seven knees were included. On average, the preoperative HKAA was 170.84° ± 3.73°, and UKA corrected the alignment to 175.16° ± 3.21° postoperatively (p

Abstract Objective This study aims to investigate the efficacy and outcomes of different surgical procedures, namely unicompartmental knee arthroplasty (UKA) and high tibial osteotomy (HTO), for the treatment of bilateral medial compartment knee osteoarthritis in the same patient. The joint awareness and function of these two surgical methods were evaluated. Methods A total of 15 patients with bilateral medial compartment knee osteoarthritis who underwent either UKA or HTO between 2012 and 2020 were included in the study. Patient data, including age, gender, body mass index and length of hospital stay, were collected. Pre- and post-operative measurements were conducted, including tibiofemoral angle, tibial plateau posterior inclination angle, proximal tibial medial angle, distance from mechanical axis to knee joint center, hip-knee-ankle angle, pre- and post-operative knee joint scores, knee joint range of motion, and FIS-12 scores at 3, 6, 12, and 24 months postoperatively. The latest follow-up was used for evaluating the outcomes of osteoarthritis treatment. Normality of continuous variables was assessed using the Shapiro–Wilk test. Between-group comparisons were performed using the paired sample t-test or Wilcoxon rank-sum test. Repeated measures analysis of variance was utilized to analyze FJS-12 measurements at different time points, and the correlation between FJS-12 and postoperative clinical results was examined using Pearson's correlation coefficient. Statistical significance was set at P

Aim: The overall goal of this review was to examine the cost-utility of robotic-arm assisted surgery versus manual surgery. Methods: We performed a systematic review of all health economic studies that compared CT-based robotic-arm assisted unicompartmental knee arthroplasty, total knee arthroplasty and total hip arthroplasty with manual techniques. The papers selected focused on various cost-utility measures. In addition, where appropriate, secondary aims encompassed various clinical outcomes (e.g., readmissions, discharges to subacute care, etc.). Only articles directly comparing CT-based robotic-arm assisted joint arthroplasty with manual joint arthroplasty were included, for a resulting total of 21 reports. Results: Almost all twenty-one studies demonstrated a positive effect of CT scan-guided robotic-assisted joint arthroplasty on health economic outcomes. For studies reporting on 90-day episodes of costs, 10 out of 12 found lower costs in the robotic-arm assisted groups. Conclusion: Robotic-arm assisted joint arthroplasty patients had shorter lengths of stay and cost savings based on their 90-day episodes of care, among other metrics. Payors would likely benefit from encouraging the use of this CT-based robotic technology.

BACKGROUND: Unicompartmental knee arthroplasty is an effective treatment for end-stage knee osteoarthritis, and its surgical procedures are relatively standard and uniform. The trauma caused by surgery in different patients is quite similar, but its postoperative recovery rate and degree are not the same. Perioperative sleep disorders have a high incidence in knee arthroplasty; however, there is still a lack of studies on the correlation between preoperative sleep quality and early rehabilitation after unicompartmental knee arthroplasty in China. OBJECTIVE: To investigate the effect of preoperative sleep quality on early rehabilitation after unicompartmental knee arthroplasty. METHODS: A total of 218 patients with knee osteoarthritis who underwent unicompartmental knee arthroplasty in The First Affiliated Hospital of Anhui Medical University from July 2018 to July 2022 were enrolled. Pittsburgh Sleep Quality Index was used to evaluate sleep quality before operation. The study subjects were divided into a high preoperative sleep quality group (Pittsburgh Sleep Quality Index score ≤ 5, n=102) and a low preoperative sleep quality group (Pittsburgh Sleep Quality Index score > 5, n=116) according to the results. The visual analog scale score of pain at 12, 24, 48 and 72 hours after operation, the number of days required for 90° of knee flexion after operation (knee flexed at least 90° without applying external force and without unbearable pain) and the length of postoperative hospital stay were compared between the two groups. The postoperative opioid analgesic use (converted to oral morphine equivalent) was also recorded between the two groups. RESULTS AND CONCLUSION: (1) There was no significant difference in age, height, body mass index, joint side, preoperative knee range of motion, preoperative visual analog scale score, preoperative Hospital for Special Surgery score and preoperative hemoglobin concentration, and albumin concentration between the two groups (P > 0.05). (2) Compared with the low preoperative sleep quality group, the high preoperative sleep quality group had significantly lower postoperative visual analog scale scores at 12, 24, 48, and 72 hours, opioid analgesic use, hemoglobin difference and albumin difference before and after operation, the number of days required for 90° of knee flexion, the length of postoperative hospital stay, and the differences were statistically significant (P < 0.05). (3) The results show that improving preoperative sleep quality is of great significance in improving prognosis, reducing the use of analgesics, improving patient satisfaction, and reducing social burden, and can directly or indirectly accelerate early rehabilitation after unicompartmental knee arthroplasty from multiple aspects and dimensions. [ABSTRACT FROM AUTHOR]

Background: To investigate whether patient-specific instrumentation (PSI) improves the femoral component positioning of implants during unicompartmental knee arthroplasty (UKA) using cadaver bone models. Methods: Fifty adult cadaveric femoral bone specimens collected from February 2016–2018, were randomized to receive medial UKA with a PSI guide (n = 25) or conventional instrumentation (CI) (n = 25). Standard anteroposterior and lateral view radiographs were obtained postoperatively to assess the coronal and sagittal positioning of the femoral prostheses, respectively. The osteotomy time was recorded to assess the convenience of PSI in guiding osteotomy. Results: Osteotomy time significantly shortened in the PSI group (3.12 ± 0.65 versus 4.33 ± 0.73 min, p < 0.001). There was a significant difference in the postoperative coronal alignment of the femoral component between the PSI and CI groups (varus/valgus angle: 1.43 ± 0.93° vs. 2.65 ± 1.50°, p = 0.001). The prevalence of outliers in coronal alignment was lower in the PSI than the CI group (2/25, 8% vs. 9/25, 36%). Sagittal posterior slope angle of the femoral component was significantly different between the two groups (8.80 ± 0.65° and 6.29 ± 1.88° in the CI and PSI groups, respectively, p < 0.001). The malalignment rate of the femoral component in the sagittal plane was 60% in the CI group, whereas no positioning deviation was observed in the PSI group. Conclusion: This study used a cadaver model to support the fact that CT-based PSI shows an advantage over CI in optimizing implant positioning for UKAs. [ABSTRACT FROM AUTHOR]

Background: Bicruciate-retaining (BCR) prosthesis has been introduced to recreate normal knee movement by preserving both the anterior and posterior cruciate ligaments. However, the use of BCR total knee arthroplasty (TKA) is still debatable because of several disappointing reports. We have been performing BCR TKAs with personalized alignment (PA). This study aimed to reveal the limb alignment and soft tissue balance of FA-BCR TKAs and compare the clinical outcomes of FA-BCR TKAs with those of unicompartmental knee arthroplasty (UKA). Methods: Fifty BCR TKAs and 58 UKAs were included in this study. The joint component gaps of BCR TKA were evaluated intraoperatively and the postoperative hip–knee–ankle (HKA) angle, medial proximal tibial angle (MPTA), and lateral distal femoral angle (LDFA) were measured using full-length standing radiography. The short-term clinical outcomes of BCR TKAs were compared with those of UKA using the scoring system of 2011 Knee Society Scoring (KSS) and the knee injury and osteoarthritis outcome score (KOOS) at an average of 2 years postoperatively (1-4yeras). Results: The coronal alignment values of PA-BCR TKA were as follows: HKA angle, 177.9° ± 2.3°; MPTA, 85.4° ± 1.9°; and LDFA, 87.5° ± 1.9°. The joint component gaps at flexion angles of 10°, 30°, 60°, and 90° were 11.1 ± 1.2, 10.9 ± 1.4, 10.7 ± 1.3, and 11.2 ± 1.4 mm for the medial compartment and 12.9 ± 1.5, 12.6 ± 1.8, 12.5 ± 1.8 and 12.5 ± 1.7 mm for the lateral compartment, respectively. The patient expectation score and maximum extension angle of PA-BCR TKA were significantly better than those of UKAs. Conclusions: The short-term clinical outcomes of PA-BCR TKA were comparable or a slightly superior to those of UKAs. [ABSTRACT FROM AUTHOR]

Purpose: In patients with monocompartmental knee osteoarthritis, unicompartmental knee arthroplasty (UKA) can be performed. This study compared the medial versus lateral UKA in patients with monocompartimental knee arthroplasty. It was hypothesised that both implants achieve a similar outcome in OKS. Methods: The UKAs were fixed-bearing medial PPK (Zimmer-Biomet, Warsaw, Indiana, USA) and fixed-bearing lateral Zuk (Lima Corporate, Udine, Italy). An intraarticular drain was placed and removed on the first postoperative day. Enoxaparin sodium 4000 units subcutaneously daily for 45 days was used as thromboembolic prophylaxis. The Italian version of the OKS was used for the clinical assessment. The following complications were also recorded: anterior knee pain, infection and revision surgeries. Results: Data from 203 patients were collected. The mean age of the patients was 68.9 ± 6.7 years and the mean BMI was 28.1 ± 4.1 kg/m2. The mean OKS on admission was 22.1 ± 4.5 points. On admission, women, patients older than 70 years, and those with a BMI lower than 28 kg/m2 who underwent lateral UKA evidenced lower OKS. At the last follow-up, 26.7 and 26.9 months for the lateral and medial UKA, respectively, no between groups difference in OKS was evidenced. No patients experienced complications. Conclusion: Medial and lateral UKA achieve similar outcomes in OKS at a minimum of two years of follow-up. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to compare patellofemoral joint alignment of knees with restored pre-arthritic coronal alignment versus knees with under- or overcorrection from their pre-arthritic coronal alignment following medial unicompartmental knee arthroplasty (UKA) and evaluate the effect of patellofemoral joint alignment on patient-reported outcomes. Methods: A retrospective analysis of 517 knees following robotic-arm assisted medial UKA was conducted. Postoperative mechanical hip-knee-ankle angle (mHKA) was compared to estimated pre-arthritic coronal alignment, using the arithmetic hip-knee-ankle angle (aHKA). Knees were considered restored to the pre-arthritic coronal alignment if mHKA was within 2.0° of aHKA (Group 1). Non-restored knees were subdivided into > 2.0° over correction (Group 2), or > 2.0° under correction (Group 3) from the pre-arthritic coronal alignment. Patellar congruence and patellar tilt angles were compared between groups. The Kujala score and Knee Injury and Osteoarthritic Outcome Score for Joint Replacement (KOOS, JR) were analyzed by group. Continuous data was compared using analysis of variance or Kruskal–Wallis tests. Chi-squared tests were used to compare discrete variables. Logistic regressions were conducted to estimate the probability of postoperative patellofemoral malalignment. Results: Group 1 included 357 knees (69.1%), Group 2 included 57 knees (11.0%), and Group 3 included 57 knees (11.0%). The prevalence of postoperative abnormal patellar congruence (i.e. ≥ 17°) was higher in Group 3 at 40.4% (p = 0.009), with a higher odds ratio of having an abnormal patellar congruence angle (2.3, p = 0.01) compared to Group 1. The prevalence of postoperative abnormal patellar tilt (i.e. ≥ 14°) was comparable between groups (n.s.). At mean follow up of 4.4 ± 1.6 years, Kujala was worse in Group 3 (76.6 ± 17.4 compared to 84.0 ± 14.9 and 85.0 ± 14.4 in Groups 1 and 2, respectively; p = 0.006). Mean KOOS, JR outcomes were comparable among groups. No significantly inferior Kujala or KOOS, JR outcomes were observed in patients across all groups with abnormal patellar congruence or tilt angles. Conclusion: Knees with under correction from their pre-arthritic coronal alignment following medial UKA were associated with a two-fold higher probability of having postoperative patellofemoral incongruence, as well as inferior mid-term Kujala scores compared to knees with restored pre-arthritic coronal alignment and knees with overcorrection from their pre-arthritic coronal alignment. Patellofemoral incongruence alone did not negatively impact functional outcome scores. Level of Evidence: IV, case series. [ABSTRACT FROM AUTHOR]

Purpose: The primary aim of this study was to evaluate the phenotypic variation using the Coronal Plane Alignment of the Knee (CPAK) classification among 1000 knees with anteromedial osteoarthritis (OA) both prior to and following medial unicompartmental knee arthroplasty (UKA). The secondary aim of this study was to investigate whether knees maintained their preoperative CPAK phenotype and to evaluate the phenotypic alterations following medial UKA. Methods: The CPAK classification was used to analyze 1000 knees that underwent medial UKA as treatment for anteromedial OA. Knees were categorized into nine distinct CPAK phenotypes based on their arithmetic hip–knee–ankle angle (aHKA), which estimates the pre-arthritic alignment, and joint line obliquity (JLO), both pre- and postoperatively. Phenotypic variation was analyzed by sex and age, and the phenotypic alterations following medial UKA were evaluated by phenotype. Results: Preoperatively, CPAK phenotype I had the highest prevalence (45.0%). Among males, the preoperative prevalence of CPAK phenotype I was significantly higher compared to females (53.2% vs. 35.0%, respectively; p ≤.001), whereas females exhibited a significantly higher occurrence of CPAK phenotype V compared to males (9.8% vs. 4.4%, respectively; p ≤.015). Following medial UKA, CPAK phenotype II had the highest prevalence (53.3%). Overall, 45.1% of knees maintained their preoperative CPAK phenotype following medial UKA, which was most frequently observed among CPAK phenotype II (67.7%) and III (65.8%). Conclusion: There is a substantial variation in CPAK phenotypes among knees with anteromedial OA, as well as following treatment with medial UKA. This variability challenges the assumption of uniform characteristics among knees with an identical wear pattern associated with anteromedial OA and emphasizes the complexity and variability of this specific form of OA. Level of evidence: III, Retrospective cohort study. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the present study was to determine the incidence of revision and report on clinical outcomes at a minimum of 10 years follow-up in patients who had received a medial unicompartmental knee arthroplasty (UKA) with an three-dimensional image-based robotic system. Methods: A total of 239 patients (247 knees), who underwent medial robotic-arm assisted (RA)-UKA at a single center between April 2011 and June 2013, were assessed. The mean age at surgery was 67.0 years (SD 8.4). Post-operatively, patients were administered the Forgotten Joint Score-12 (FJS-12) and asked about their satisfaction (from 1 to 5). Post-operative complications were recorded. Failure mechanisms, revisions and reoperations were collected. Kaplan–Meier survival curves were calculated, considering revision as the event of interest. Results: A total of 188 patients (196 knees) were assessed at a mean follow-up of 11.1 years (SD 0.5, range 10.0–11.9), resulting in a 79.4% follow-up rate. Seven RA-UKA underwent revision, resulting in a survivorship rate of 96.4% (CI 94.6%–99.2%). Causes of revision included aseptic loosening (2 cases), infection (1 case), post-traumatic (1 case), and unexplained pain (3 cases). The mean FJS-12 and satisfaction were 82.2 (SD 23.9) and 4.4 (SD 0.9), respectively. Majority of cases (174/196, 88.8%) attained the Patient Acceptable Symptoms State (PASS, FJS-12 > 40.63). Male subjects had a higher probability of attaining a "forgotten joint" (p < 0.001) and high satisfaction (equal to 5, p < 0.05), when compared to females. Conclusions: Three-dimensional image-based RA-UKA demonstrated high implant survivorship and good-to-excellent clinical outcomes at minimum 10 years follow-up. Pain of unknown origin represented the most common reason for RA-UKA revision. Level of evidence: III. [ABSTRACT FROM AUTHOR]

Background: Early post-operative medial tibial bone loss in both unicompartmental knee replacement and total knee replacement has been reported in our previous studies and many other studies. Significant bone loss can contribute to a tibial stress fracture, bone pain and early implant failure. The bone loss appeared to be greater in total knee replacement. Therefore, the aim of the study is to look for any significant difference in medial tibial bone loss in both unicompartmental knee replacement and total knee replacement in the first 3 years and to investigate the underlying pathophysiology. Methods: Cases of fixed-bearing unicompartmental knee replacement and posterior stabilising total knee replacement performed in 2015–2016 were recruited. The change in medial tibial bone loss (expressed in grayscale Gy) over a three-year post-operative period was measured using the method of digital radiological densitometry. Potential predictors and correlations were analysed. Results: Forty-four cases of unicompartmental knee replacement and 52 cases of total knee replacement were recruited. The cumulative drop in 3 years was 23.3% in unicompartmental knee replacement and 33.7% in total knee replacement, respectively, a difference of up to 10%. The cumulative drop between the two groups at 12 months (p < 0.05) and 36 months (p < 0.05), respectively, were significantly different. Angle correction has not been shown to affect medial tibial bone loss in this study. No surgical complication was documented during the follow-up period. Conclusion: Total knee replacement results in 10% greater medial tibial bone loss than unicompartmental knee replacement at the three-year time. The effect is greatest in the first year. In addition to possible stress shielding, early physiological bone remodelling in response to surgical trauma can contribute to the difference in medial tibial bone loss of unicompartmental knee replacement and total knee replacement. This is supported by the insignificant correlation between angle correction and medial tibial bone loss in the result. [ABSTRACT FROM AUTHOR]

Objective. Suboptimal fixation of the tibial component is one of the main factors leading to aseptic loosening in unicompartmental knee arthroplasty (UKA). Improvements in primary fixation in cemented UKA have been suggested to be a key issue for long-term survival. In this context, it has been questioned whether specific implant design features influence interface strength, lowering aseptic loosening and post-operative pain rates. The aim of this study is to compare two different tibial tray designs in cemented UKA in terms of clinical outcome, failures, implant survival, and complications. Materials and methods. This is a prospective consecutive study of two different tibial component fixation in 100 cemented UKA. 50 patients received a flat cemented tibial tray design, and 50 a two-peg cemented tibial component UKA. Both groups were similar in terms of age, sex, comorbidities, and BMI. Results. No significant difference was found in clinical outcomes and overall failure rates. In the flat tray group, the mean preoperative KSS was 57.2, which increased at 1-year follow-up after surgery to 92.28, and remained stable at the 3 and 6 year control visits. In parallel, the mean pre-operative KOOS of 59 increased to 87.20. The mean preoperative KSS score in the 2 pegs group was 56.8 and the mean KOOS 58.1. At 1-year follow-up the KSS score increased to 94.1 and the KOOS score to 89.22, remaining stable at the 3- and 6-year follow-ups. Two-peg tibial component showed a significantly lower rate of persistent pain on the tibial side, 8% of patients at 1 year follow-up and 2% at 2 years, compared to 20% at 1 year and 6% at 2-year follow-up in the flat tray group (p < 0.05). In both groups, patients with pain at the 2-year control, 4 patients in total, still complained of mild and intermittent pain, VAS 1 to 2, at the 6 year visit. There was also a lower incidence of radiolucent lines compared to flat design prosthesis, none versus 6 at 3-yeas radiographic control. Radiolucent lines were not related to pain. No difference was detected regarding range of motion between the two groups. Conclusions. This study reveals that the clinical results and failure rates arising from the use of two different tibial components, one flat and one with 2 pegs, are similar. However, a lower rate of pain and radiolucent lines are detected on the tibial side with the use of a two-peg tibial component design. This outcome could denote a better fixation of the 2 peg metal-backed tibial component implant. [ABSTRACT FROM AUTHOR]

Infections are rare and poorly studied complications of unicompartmental knee arthroplasty (UKA) surgery. They are significantly less common compared to infections after total knee arthroplasties (TKAs). Optimal management of periprosthetic joint infections (PJIs) after a UKA is not clearly defined in the literature. This article presents the results of the largest multicentre clinical study of UKA PJIs treated with Debridement, Antibiotics and Implant Retention (DAIR). In this retrospective case series, patients presenting between January 2016 and December 2019 with early UKA infection were identified at three specialist centres using the Musculoskeletal Infection Society (MSIS) criteria. All patients underwent a standardized treatment protocol consisting of the DAIR procedure and antibiotic therapy comprising two weeks of intravenous (IV) antibiotics followed by six weeks of oral therapy. The main outcome measure was overall survivorship free from reoperation for infection. A total of 3225 UKAs (2793 (86.2%) medial and 432 (13.8%) lateral UKAs) were performed between January 2016 and December 2019. Nineteen patients had early infections necessitating DAIR. The mean follow-up period was 32.5 months. DAIR showed an overall survivorship free from septic reoperation of 84.2%, with overall survivorship free from all-cause reoperation of 78.95%. The most common bacteria were Coagulase-negative Staphylococci, Staphylococcus aureus and Group B Streptococci. Three patients required a second DAIR procedure but remained free from re-infection at follow-up obviating the need for more demanding, staged revision surgery. In infected UKAs, the DAIR procedure produces a high rate of success, with a high survivorship of the implant. Debridement, Antibiotics and Implant Retention (DAIR) is a successful and minimally invasive surgical option for the management of periprosthetic joint infections (PJIs) after UKA. The surface area available for bacteria to colonise is much smaller in UKAs compared to total knee arthroplasties (TKAs), and this may account for the higher success rates of the DAIR procedure in infected UKAs versus infected TKAs. A second DAIR procedure can be considered in the management of the early recurrence of PJIs with a well-fixed UKA. [ABSTRACT FROM AUTHOR]

Background: Different posterior inclinations of tibial component after unicompartmental knee arthroplasty (UKA) may lead to different biomechanical characteristics of the knee joint. This finite element study was designed to investigate the tibiofemoral contact pressures after UKA with different posterior inclinations of tibial component. Methods: Finite element model of a healthy knee joint was constructed, and mobile-bearing (MB) UKA models with 5 different posterior inclinations (3°, 5°, 7°, 9° and 11°) of tibial components were simulated. The maximum contact pressures of tibial plateau cartilage in the lateral compartment and polyethylene insert in the medial compartment were calculated based on the ground reaction force and the angle of the knee flexion obtained by 3D motion capture system. Results: The loading ratio of medial and lateral compartments during standing stance (medial 54.49%, lateral 45.51%) and tibial anterior displacement (134 N, 3.89 mm) of healthy knee was basically consistent with previous experimental data. The maximum contact pressures of the medial meniscus and lateral tibial plateau cartilage of the healthy knee during standing stance were 2.14 MPa and 1.57 MPa, respectively. At the static standing phase, the maximum contact pressures of the polyethylene insert decreased from 17.90 to 17.29 Mpa, and the maximum contact pressures of the tibial plateau cartilage in the lateral compartment increased from 0.81 to 0.92 Mpa following an increase in the posterior inclination of the tibial component. At the first peak of ground reaction force, the maximum contact pressures of polyethylene insert increased from 22.37 to 25.16 MPa, and the maximum contact pressures of tibial plateau cartilage in the lateral compartment increased from 3.03 to 3.33 MPa, with the increase in the posterior inclination of the tibial component. At the second peak of ground reaction force, the maximum contact pressures of polyethylene insert decreased from 2.34 to 2.22 MPa with the increase in posterior inclination of tibial component. Conclusion: The preoperative and postoperative finite element models of MB UKA were well established. The results showed that the maximum contact pressures of the polyethylene insert did not change significantly with the increase in the posterior inclination of the tibial prosthesis, while the maximum contact pressures of the tibial plateau cartilage of the lateral compartment increased when the posterior inclination of the tibial prosthesis was > 7°. Our results also show that the maximum contact pressures were greater with an excessive inclination angle (11°) of the tibial component, and the pressures of the tibial plateau cartilage in the lateral compartment were more concentrated on the posterior area. This study, therefore, proposes that excessive osteotomy should be avoided. [ABSTRACT FROM AUTHOR]

BACKGROUND: Artificial knee arthroplasty is widely used in the field of joint surgery as the most effective treatment for various end-stage joint diseases such as knee osteoarthritis and rheumatoid arthritis. Finite element analysis is a biomechanical research method developed gradually with the continuous progress of computer technology, which has a strong modeling function and three-dimensional simulation characteristics. At present, finite element analysis has been widely used in orthopedic biomechanical studies. OBJECTIVE: To review the current status and progress of finite element analysis in various types of total knee arthroplasty. METHODS: Articles related to finite element analysis and artificial knee arthroplasty published from inception to August 2022 were searched on PubMed, CNKI and WanFang databases by computer. English search terms were “finite element analysis, TKA, UKA, revision total knee arthroplasty, knee osteoarthritis, knee joint, femoral component, tibia component”. Chinese search terms were “finite element analysis, total knee arthroplasty, unicompartmental knee arthroplasty, knee revision, knee, femoral prosthesis, tibial prosthesis”. A total of 53 articles were finally included for review. RESULTS AND CONCLUSION: (1) In total knee arthroplasty, the mobile bearing reduces the tibiofemoral joint contact surface stress compared with the fixed bearing, thereby reducing the wear of the polyethylene bearing. Compared with mechanical alignment, total knee arthroplasty with kinematic alignment reduces the maximum stress and maximum strain value of femoral prosthesis and polyethylene insert of the artificial joint, and generates lower stress, thus reducing the wear of joint contact surface and prolonging the life of the prosthesis. (2) In unicompartmental knee arthroplasty, the femoral and tibial prostheses of the mobile platform have better conformity and can reduce prosthesis wear; while the fixed platform prosthesis in unicompartmental knee arthroplasty should avoid local stress concentration caused by overconformity and lead to accelerated prosthesis wear. (3) In revision total knee arthroplasty, the design length of the stem extension should maintain the best balance between preserving bone quality and reducing periprosthetic stress after implantation. Pressfit stems showed higher micromotion compared to cemented stems. (4) Compared with traditional mechanical research, finite element analysis can carry out relatively accurate simulations and make up for the shortcomings of traditional mechanics in knee joint research, so it has a high application value in the medical field. [ABSTRACT FROM AUTHOR]

Introduction: Unicompartmental knee arthroplasty (UKA) is an effective surgical treatment for medial compartment arthritis of the knee, yet surgical outcomes are directly related to surgical execution. Robotic arm-assisted surgery aims to address these difficulties by allowing for detailed preoperative planning, real-time intraoperative assessment and haptic-controlled bone removal. This study aimed to compare the clinical and radiological outcomes between conventional manual mobile bearing and robot arm-assisted fixed bearing medial UKA in our local population. Materials and methods: This is a retrospective case–control study of 148 UKAs performed at an academic institution with a minimum of 1-year follow-up. 74 robotic arm-assisted UKAs were matched to 74 conventional UKAs via propensity score matching. Radiological outcomes included postoperative mechanical axis and individual component alignment. Clinical parameters included a range of motion, Knee Society knee score and functional assessment taken before, 6 and 12 months after the operation. Results: Robot arm-assisted UKA produced a more neutral component coronal alignment in both femoral component (robotic -0.2 ± 2.8, manual 2.6 ± 2.3; P = 0.043) and tibial component (robotic -0.3 ± 4.0, manual 1.7 ± 5.3; P < 0.001). While the postoperative mechanical axis was comparable, robot arm-assisted UKA demonstrated a smaller posterior tibial slope (robotic 5.7 ± 2.7, manual 8.2 ± 3.3; P = 0.02). Clinical outcomes did not show any statistically significant differences. Conclusion: Compared with conventional UKA, robotic arm-assisted UKA demonstrated improved component alignment and comparable clinical outcomes. Improved radiological accuracy with robotic-arm assistance demonstrated promising early results. [ABSTRACT FROM AUTHOR]

Purpose: It is always a challenge for orthopaedic surgeons to minimise surgical incisions while ensuring excellent surgical results. We propose the minimally invasive small incision (MISI) technique and an extramedullary positioning technique in the unicompartmental knee arthroplasty (UKA) surgery. This study aimed to clarify the early postoperative clinical outcomes and component alignment between MISI and conventional minimally invasive surgical (MIS) techniques. Methods: We prospectively enrolled 60 patients who underwent MISI-UKA and 60 patients who underwent MIS-UKA as controls. Clinical parameters include the time of straight leg raising, postoperative walking time with walker assistance, hospital stay, Numerical Rating Scale (NRS) pain score and Knee Society Score (KSS). The postoperative components and lower extremity alignment were compared between the two groups with radiographic image measurement. Results: The MISI group obtained a smaller incision during knee extension (P < 0.001) but a longer tourniquet usage time than the MIS group. The MISI group lost less blood (P < 0.001). The MISI group achieved straight leg raising and walking with aid earlier after surgery, with a shorter hospital stay than the MIS group (P < 0.001). Range of motion (ROM), NRS and KSS scores revealed no significant difference between the two groups in six months postoperative follow-up (P > 0.05). Radiographic measurement results between the two groups revealed no statistical difference (P > 0.05) Conclusion: The MISI-UKA could achieve faster earlier recovery after surgery and shorter hospital stays without compromising the principles of proper prosthesis position and limb alignment compared with the conventional MIS-UKA. [ABSTRACT FROM AUTHOR]

Background: The presence of significant patellofemoral arthritis (PFA) is still considered a contraindication for unicondylar knee arthroplasty (UKA) by many surgeons. The purpose of this study was to determine if the presence of severe PFA at the time of UKA compromised early (< 6 months) post-operative knee range of motion or functional outcomes. Methods: This retrospective review evaluated unilateral and bilateral UKA (323 patients; 418 knees) between 2015 and 2019. Procedures were grouped by degree of PFA present at the time of surgery, including mild PFA (Group 1; N = 266), moderate to severe PFA (Group 2; N = 101), and severe PFA with lateral compartment bone-on-bone contact (Group 3; N = 51). Knee range of motion and Knee Society Knee (KSS-K) and Function (KSS-F) scores were collected both before and at 6 months following surgery. Group differences were evaluated with Kruskal–Wallis and Chi-square tests for continuous and categorical variables, respectively. Univariate and multivariable logistic regressions were performed to determine influential variables associated with post-operative knee flexion being ≤ 120° and presented as odds ratios (OR) and 95% confidence intervals (CI). Results: Pre-operative flexion was lowest in Group 3 (p = 0.010) with 17.6% of knees having flexion ≤ 120°. Post-operative flexion was lowest in Group 3 (119.1° ± 8.4°, p = 0.003) with 19.6% knees having flexion ≤ 120° compared to 9.8% and 8.9% in Groups 1 and 2, respectively. No significant difference in KSS-F following surgery was found; all three groups demonstrated similar clinical improvement. Increased age (OR 1.089, CI 1.036–1.144; p = 0.001) and body mass index (OR 1.082, CI 1.006–1.163; p = 0.034) were found to be associated with post-operative knee flexion ≤ 120°, while high pre-operative flexion (OR 0.949, CI 0.921–0.978; p = 0.001) was found to be inversely associated with poor knee flexion following surgery. Conclusion: Patients with severe PFA demonstrate similar clinical improvement following UKA at 6 months as patients with less severe PFA. [ABSTRACT FROM AUTHOR]

Background: Functional demands of patients undergoing knee arthroplasty are increasing. However, it remains unclear which patient-specific factors have an impact on postoperative activity and whether there is a difference between total and unicompartmental knee arthroplasties (TKA/UKA). Materials and methods: This retrospective study analyzed 1907 knees with TKA (n = 1746) or UKA (n = 161), implanted for primary osteoarthritis. Pain and activity (lower extremity activity scale, LEAS) were assessed 2 years after surgery. High activity was defined as LEAS ≥ 14. Cohorts were compared using Kruskal–Wallis or Pearson-Chi-square test. A generalized least squares model was used to predict LEAS scores between cohorts adjusted for age, sex, BMI, Charlson Comorbidity Index, ASA score, and preoperative LEAS. Result: There was no difference in pain 2 years after surgery between UKA and TKA (p = 0.952). Preoperative LEAS was similar for UKA and TKA (p = 0.994), and both groups showed significant (p < 0.001 respectively) and similar improvements after surgery (p = 0.068). LEAS 2 years after surgery was 11.1 (SD 3.2) for TKA and 11.9 (SD 3.5) for the UKA group (p = 0.004). After adjusting for preoperative LEAS, age, sex, BMI, CCI and ASA, the difference was not significant (p = 0.225). Male sex, lower BMI, higher preoperative LEAS, and younger age were associated with higher postoperative LEAS (p < 0.001, respectively). Conclusion: Patients can achieve a high level of activity following both TKA and UKA. While the postoperative activity level did not depend on the type of the procedure, younger age, male sex, lower BMI, and a higher preoperative activity level were associated with a higher postoperative activity level. [ABSTRACT FROM AUTHOR]

Purpose: Previous studies comparing high tibial osteotomy (HTO) with unicompartmental knee arthroplasty (UKA) have seldom accounted for differing patient characteristics between both groups. This study compared patient-reported outcomes (PROs) of HTO and UKA patients, adjusted for preoperative PROs, osteoarthritis grade and sex. Methods: A retrospective study was performed analysing prospectively collected PROs, namely the Oxford Knee Score (OKS) and pain/satisfaction scores, collected preoperatively and at 6 months, 12 months and 24 months postoperatively. Consecutive medial opening-wedge HTOs and medial UKAs from 2016–2019, with a preoperative Kellgren–Lawrence grade ≥ 3, aged 50–60 years, were included. Linear mixed model analyses, with the OKS over time as the primary outcome, were used. Results: We included 84 HTO patients (mean age 55.0 ± 3.0, 79% male, mean BMI 27.8 ± 3.4, 75% Kellgren–Lawrence grade 3) and 130 UKA patients (mean age 55.7 ± 2.8, 47% male, mean BMI 28.7 ± 4.0, 36% Kellgren–Lawrence grade 3). Response rates were ≥ 87% at all time points. Corrected for preoperative PROs, Kellgren–Lawrence grade and sex, the HTO group had a 2.5 (95% CI 1.0–4.0) points lower OKS over time than the UKA group (p = 0.001). The Numeric Rating Scale scores (NRS; 0–10) for pain at rest and during activity were higher (p < 0.01) in the HTO group. The EQ-5D-descriptive system (p < 0.01), NRS satisfaction (p < 0.01), anchor function and pain scores (p < 0.01) were lower over time in the HTO group. Conclusion: UKA patients had better OKS scores, pain and satisfaction scores over time than HTO patients. However, the observed differences were below their established minimal clinically important differences. Therefore, from the patients' perspective, HTO did not appear to be inferior to UKA under the indications outlined in this study. Level of evidence Level IV. [ABSTRACT FROM AUTHOR]

Purpose: Does patients revised for unexplained pain after mUKA present the same PROM and satisfaction scores 1–3 years after revision as patients revised for aseptic loosening?". Methods: 104 patients undergoing revision of mUKA's for the indications unexplained pain and aseptic loosening were included in the period January 1, 2018 to December 31, 2020. from the Danish Knee Arthroplasty Register. 52 patients were revised for unexplained pain and 52 for aseptic loosening. Patient demographics did not differ between the two groups. PROMs [Oxford Knee Score (OKS), EQ-5D-5L, Forgotten Joint Score (FJS)] and questions about satisfaction with the surgery were sent to digitally secured mailboxes. Pearson's Chi-square test and Wilcoxon Rank Sum test were used to test for statistical differences between groups. Results: The median OKS 1–3 years after revision was 26 (IQR 22) for unexplained pain vs 34 (IQR 12) for aseptic loosening, p = 0.033. The median EQ-5D-5L Index after revision was 0.7 (IQR 0.6) for unexplained vs 0.8 (IQR 0.1) for aseptic loosening, p = 0.014. The median FJS after revision was 48 (IQR 10) for unexplained pain vs 52 (IQR 14) for aseptic loosening, p = 0.1. The mean satisfaction with the surgery on a 0–100 scale (100 = not satisfied; 0 = very satisfied) was 55 (IQR 60) for unexplained pain vs 50 (IQR 67) for aseptic loosening, p = 0.087, and patients revised for unexplained pain were less likely to find their knee problem importantly improved (p = 0.032). Conclusion: Patients undergoing revision of mUKAs for unexplained pain presented poor postoperative PROM scores, and PROM scores were worse compared to those of patients revised for aseptic loosening. Patients revised for unexplained pain were less likely to find their knee problem importantly improved. This study support the evidence against revisions for unexplained pain. Level of evidence: Level III. [ABSTRACT FROM AUTHOR]

Outliers in implant positioning, malalignment, and joint line height change are risk factors for unicompartmental knee arthroplasty (UKA) failure. However, their relationships and patterns in large datasets remain unexplored. This study assessed medial UKA survival in a large cohort and explored associated risk factors. This was a retrospective cohort study on medial UKA patients (2011 to 2019). Radiological outcomes included tibial implant positioning in the coronal plane, posterior tibial slope, residual knee deformity, and joint line restitution. Survival rate at last follow-up was recorded. Multinomial logistic regression analyzed risk factors, incorporating demographic and univariate analysis data. Three hundred and sixty-six knees met inclusion criteria, with 10 lost to follow-up (2.7%). Mean follow-up was 61.3 months [24.1 to 135.1]. 5- and 10-year implant survival rates were 92% ± 1.6 and 88.4% ± 3.8, respectively. Multivariate analysis identified post-operative hip-knee-ankle angle (HKA) ≤ 175° (OR = 5.30 [1.64 to 17.13], P =.005) and joint line lowering ≥2 mm (OR = 8.86 [2.06 to 38.06]) as significant risk factors for tibial implant failure. Their combination carried a significantly high risk of failure (OR = 10.3 [3.1 to 34.3]). Post-operative HKA < 175° was common in knees with pre-operative HKA < 172°. This study reports encouraging 5- and 10-year survival outcomes for medial UKA. Tibial loosening was the main reason for revision. Patients with joint line lowering ≥ 2 mm and post-operative HKA ≤ 175° were at high risk of tibial implant failure. Surgeons should carefully restore the joint line in cases of pre-operative HKA < 172°. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of concomitant lateral patellar retinacular release (LPRR) during medial unicompartmental knee arthroplasty (UKA). We retrospectively analyzed 100 patients who had patello-femoral joint (PFJ) arthritis who underwent medial UKA with (n = 50) and without (n = 50) LPRR who had ≥2 years follow-up. Radiological parameters associated with lateral retinacular tightness, including patellar tilt angle (PTA), lateral patello-femoral angle (LPFA), and congruence angle, were measured. Functional evaluation was performed using the Knee Society Pain Score, Knee Society Function Score (KSFS), Kujala Score, and the Western Ontario McMaster Universities Osteoarthritis Index score. Intraoperative patello-femoral pressure evaluation was performed on 10 knees to evaluate the pressure changes before and after LPRR. Mann–Whitney U-tests were used for statistical analyses. Demographic data did not differ between the LPRR(+) and LPRR(−) groups. A decrease in PTA and an increase in LPFA were observed in the LPRR(+) group compared to those in the LPRR(−) group (PTA; −0.54 versus −1.74, P =.002, LPFA; 0.51 versus 2.01, P =.010). The LPRR(+) group showed significantly better KSFS and Kujala scores than the LPRR(−) group (KSFS: 90 versus 80, P =.017; Kujala score: 86 versus 79, P =.009). Intraoperative patello-femoral pressure analysis showed a 22.6% reduction in the PFJ contact pressure and an 18.7% reduction in PFJ peak pressure after LPRR. (P =.0015, P <.0001, respectively) A LPRR during UKA may be a simple and useful adjunct procedure to relieve PFJ symptoms with concomitant PFJOA. [ABSTRACT FROM AUTHOR]