Unicompartmental Knee Arthroplasty Research Articles (Page 1)

Patients with prior anterior cruciate ligament reconstruction (ACLR) are at increased risk of early medial osteoarthritis. Medial mobile-bearing (MB) unicompartmental knee arthroplasty (UKA) offers a minimal-invasive and joint-preserving alternative to total knee arthroplasty (TKA), yet evidence in ACLR patients remains limited. This study compared survivorship, reoperation causes and functional outcomes of medial MB UKA in ACLR patients versus matched controls. This retrospective 1:2 matched case-control study included 106 medial MB UKAs after ACLR (mean age 61 ± 9 years; body mass index [BMI]: 29 ± 5 kg/m2; follow-up 5 ± 2 years) and 208 matched controls (n = 4 with only one match) with a minimum follow-up of 2 years. Kaplan-Meier analysis estimated 9-year survival for reoperation, implant revision (femur and/or tibia) and conversion to TKA. Reoperation causes and PROMs (Oxford Knee Score [OKS] and UCLA Activity Score) were compared. Cumulative 9-year reoperation-free survival was significantly lower (p = 0.026) in the ACLR group (81.2%; 95% confidence interval [CI]: 71.8-90.6) compared with matched controls (92.1%; 95% CI: 88.2-96.0). Cumulative 9-year implant revision-free survival was also significantly lower (p = 0.004) in the ACLR group (89.8%; 95% CI: 81.8-97.8) compared with matched controls (98.4%; 95% CI: 96.6-100.0). For conversion to TKA, survival rates were 92.7% (95% CI: 85.3-100.0) and 98.2% (95% CI: 96.2-100.0), respectively (p = 0.071). The risk for bearing dislocation was eightfold higher in the ACLR group compared with controls (3.8% vs. 0.5%; p = 0.046). The mean postoperative OKS in the ACLR group was 42.5 ± 6.2 and 42.3 ± 6.1 in controls; the UCLA Activity Score was 6.3 ± 1.2 and 6.1 ± 1.2, respectively. Despite excellent functional outcomes, ACLR patients undergoing MB UKA face a significantly higher risk for reoperation and inferior implant survival compared with matched controls. The increased risk for additional surgery in patients with prior ACLR, particularly for bearing dislocation, should be acknowledged when indicating medial UKA, and the usage of fixed-bearing implants reduces this risk. Level III.

Accurate reconstruction of the posterior tibial slope (PTS) is essential for successful unicompartmental knee arthroplasty (UKA), yet intraoperative assessment remains challenging without advanced navigation tools. This study evaluated the accuracy of visual intraoperative assessment of PTS changes after tibial resection. Resection blocks from total knee arthroplasty (TKA) were processed to simulate UKA resections, providing a wide range of slope variations. PTS changes were measured radiographically and via optical scans of resection blocks from 55 patients with severe osteoarthritis. Three experienced surgeons visually estimated PTS changes, which were compared to reference measurements using intraclass correlation coefficients (ICCs), Pearson correlation, analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD) tests. Optical scan and radiographic measurements showed near-perfect agreement (ICC = 0.99). The mean deviation between surgeon estimates and radiographic measurements was 1.0° ± 0.7° (range 0°-3.0°). Examiner ICCs ranged from 0.88 to 0.96, and Pearson correlations were strong (0.77-0.87). ANOVA and HSD tests showed no significant differences between visual and reference measurements. Visual inspection by experienced surgeons provides a sufficiently accurate and reliable method for intraoperative assessment of PTS during UKA. Level IV.

Correction: Comparison of early outcomes between unicompartmental and total knee arthroplasty in patients with anteromedial compartment knee osteoarthritis and class II obesity: a retrospective case analysis

Aseptic failure of unicompartmental knee arthroplasty (UKA) often requires revision to a total knee arthroplasty (TKA). However, outcomes following revision from UKA to TKA remain controversial. The purpose of this study was to analyze a large cohort of revisions from UKA to TKA, with emphasis on implant survivorship, clinical outcomes and radiographic results. We retrospectively reviewed 118 aseptic revisions from UKA to TKA performed at a single surgical center between 2016 and 2022. Of these, 50 were required due to progression of osteoarthritis (42%), and 44 for aseptic loosening (37%). The mean age was 67 years, 65% were female, and the mean body mass index was 31 kg/m2. Tibial stem extensions were used in 30% of cases, augments in 9%, and a constrained implant in a single patient. The mean follow-up was 6 years (range, 2.7-10.9). The 8-year survivorship free of any re-revision and reoperation was 94% and 92%, respectively. Progression of osteoarthritis was associated with reduced odds of re-revision (odds ratio [OR]: 0.09; p = 0.025) and reoperation (OR: 0.20; p = 0.04). Knee Society Function Scores (KSS-F) improved from 53 to 82 (p < 0.001), with no correlation to implant type, demographics or radiographic patella height. At final follow-up, the mean Oxford Knee and Forgotten Joint Scores were 33 and 54, respectively. The mean modified Insall-Salvati Ratio was 1.56 preoperatively compared to 1.52 at last follow-up (p = 0.07). Aseptic revision from UKA to TKA provides excellent midterm implant survivorship, clinical outcomes, and radiographic results, particularly when performed for the progression of osteoarthritis. Level IV.

Debridement, antibiotics, and implant retention (DAIR) is a widely used surgical approach for managing acute prosthetic joint infection (PJI) following knee arthroplasty (KA). However, limited studies have explored its application across different KA types. This study aims to compare the clinical outcomes of DAIR in acute PJI following unicompartmental knee arthroplasty (UKA) versus total knee arthroplasty (TKA), with a focus on microbial profiles, treatment characteristics, and patient outcomes. We retrospectively reviewed clinical data from 67 consecutive patients diagnosed with acute PJI, as defined by the Musculoskeletal Infection Society (MSIS) criteria, who underwent DAIR at our institution between January 2016 and April 2023. Patients were categorized into two groups based on the type of primary arthroplasty: 51 in the TKA-DAIR group and 16 in the UKA-DAIR group. Comparative analyses included pre- and postoperative serological inflammatory markers, microbiological findings, knee functional outcomes, and infection recurrence rates. Coagulase-negative staphylococci were the most frequently isolated organisms in both the TKA-DAIR (37.3%) and UKA-DAIR (43.8%) groups. On postoperative day one, ESR and CRP levels showed no significant differences between groups. However, by postoperative day three, the UKA-DAIR group exhibited significantly lower ESR (P = 0.005) and CRP (P = 0.007) levels, a trend that persisted through day five (ESR, P = 0.014; CRP, P = 0.015). At two year follow-up, there were no significant differences between groups in HSS knee scores (P = 0.107), VAS pain scores (P = 0.531), or range of motion (ROM; P = 0.128). Notably, Kaplan-Meier survival analysis demonstrated a significantly lower infection recurrence rate in the UKA-DAIR group over the two year follow-up period (P = 0.041). In cases of acute PJI following UKA, where MRI confirms that the contralateral compartment remains uninvolved and the causative pathogen is clearly identified, DAIR yields superior clinical outcomes compared to TKA. This may be attributed to the reduced prosthetic surface area in UKA and the retention of native cartilage, which may serve as an effective barrier against infection. Based on these findings, we recommend DAIR as the preferred treatment strategy for acute UKA PJI under these conditions.

BackgroundAlthough both unicompartmental knee arthroplasty (UKA) and medial open-wedge high tibial osteotomy (MOWHTO) are widely accepted surgical options for medial compartment osteoarthritis, there is limited evidence from long-term outcomes to confirm and refine their established indications. This study aimed to evaluate the long-term clinical and radiologic outcomes of UKA and MOWHTO when performed according to their established indications at a single institution, and to characterize the demographic and preoperative radiographic differences associated with surgical selection.MethodsPatients who underwent UKA or MOWHTO for medial compartmental OA with a minimum 10-year follow-up were retrospectively reviewed. Preoperative characteristics, including age and the degree of medial OA using Kellgren-Lawrence grading, clinical outcomes, and radiologic parameters, including hip-knee-ankle angle (HKAA), medial proximal tibial angle (MPTA), and OA progression in the patellofemoral compartment, were compared. Survivorship based on the conversion to total knee arthroplasty was also evaluated.ResultsThe current study included 79 UKAs and 140 MOWHTOs with a mean 13.2 ± 1.7 years follow-up. Preoperatively, the UKA group had significantly older age (P < 0.001) and more advanced degree of medial OA (P < 0.001) than the MOWHTO group. Postoperative clinical outcomes were not significantly different between the groups. Radiologically, the UKA group had significantly less varus alignment and larger MPTA than the MOWHTO group (all, P < 0.001). Although the proportion of OA progression in the patellofemoral joint was higher in the MOWHTO group than in the UKA group at the latest follow-up (P = 0.012), there was no significant difference in anterior knee pain. At the mean 13-year follow-up, survival rates were not significantly different between the UKA (96.2%) and MOWHTO (98.6%) groups.ConclusionsBoth UKA and MOWHTO demonstrated excellent long-term outcomes when performed under their established indications for medial compartment OA. Patients selected for UKA were older, had more advanced OA, less varus alignment, and a larger MPTA compared with those undergoing MOWHTO, consistent with published selection criteria. Radiographic progression of patellofemoral arthritis occurred more frequently after MOWHTO than after UKA, although this finding was not associated with clinical significance.

More patients are undergoing unicompartmental knee arthroplasty (UKA) at a younger age, and uncemented fixation has been introduced relatively recently. This study aimed to assess the effect of age and fixation type on outcomes following Oxford medial UKA. This retrospective multicentre study compared survivorship, revision indications and Oxford knee score (OKS) between cemented and uncemented mobile-bearing UKAs across three age groups (<60, 60-69 and ≥70 years). A total of 1401 primary medial Oxford UKAs were included, with mean follow-up of 7.2 ± 3.6 years. Overall, implant survivorship was 93.9%. For patients <60 years, revision-free implant survivorship was higher with uncemented versus cemented fixation 10 years: (91.0% vs. 81.8%, p = 0.014) and 15 years (88.2% vs. 78.8%, p = 0.02). The unadjusted hazard ratio (HR) indicated an approximately threefold higher revision risk with cemented implants (HR 2.90, 95% confidence interval [CI]: 1.18-7.11; p = 0.02). There was no difference in revision-free implant survivorship in older patients (60-69 years: 10-years: 94.8% vs. 91.6%, p = 0.131; 15 years: 91.7% vs. 80.6%, HR: 1.98, 95% CI: 0.91-4.31, p = 0.087; ≥70 years: 10 years: 93.4% vs. 95.6%, p = 0.446; 15 years: 91.6% vs. 91.6%, HR: 0.83, 95% CI: 0.37-1.90, p = 0.67). Bearing dislocation was the most common reason for revision in uncemented implants among younger patients (50.0% and 40.0% of all revisions, respectively), whereas for the cemented group it was osteoarthritis progression (41.7% and 50.0%, respectively). OKS did not differ by fixation type, except for a small early advantage in the 60-69 group at 6 months (38.5 ± 8.1 vs. 40.5 ± 7.2; p = 0.03). Uncemented mobile-bearing Oxford UKA had superior long-term survivorship in patients <60 years of age. There was no difference for patients ≥60 years. These findings suggest that uncemented UKA should be considered for patients <60 years, whereas either cemented or uncemented UKA is suitable for patients >60 years. Level II.

Objective: To investigate the correlation between preoperative tibial tubercle-trochlear groove distance (TT-TG) and postoperative tibiofemoral prosthesis divergence angle (DA) in mobile-bearing unicompartmental knee arthroplasty (MB-UKA) for knee osteoarthritis, and to assess the clinical effect of DA on functional outcomes. Methods: This retrospective study included the consecutive patients undergoing MB-UKA at the Third Hospital of Hebei Medical University from January to December 2023. Postoperative DA was measured using 30° patellar axial radiographs. The linear relationship between postoperative DA and preoperative TT-TG was clarified based on their correlation, and a regression equation was established. Based on regression analysis, a DA threshold of 12° corresponded to a preoperative TT-TG of 16 mm. The patients were divided into groups according to DA or TT-TG: DA≥12° and<12° group or TT-TG≥16 mm and<16 mm group. The Hospital for Special Surgery (HSS) knee score and Feller patella score before and after surgery were recorded to assess knee function and perform intergroup comparisons. Results: A total of 156 cases were enrolled in this study, including 30 males and 126 females with a mean age of (66.29±5.42) years. Over a mean follow-up of (13.3±2.7) months, no bearing dislocations occurred. At the final postoperative follow-up, the median HSS knee score [M(Q1,Q3)] significantly improved from 55 (50, 60) preoperatively to 86 (82, 92) points, and the median Feller patella score increased from 17 (15, 20) to 22 (21, 24) points, with both differences being statistically significant (both P<0.05). The mean postoperative DA was 10.03°±4.71°. The DA≥12° group exhibited inferior Feller scores when compared to DA<12° group [21 (20, 23) vs 23 (21, 24) points, P=0.001], but there was no statistically significant difference in the improvement of Feller scores between the two groups (P=0.119). There was no statistically significant difference in postoperative HSS scores or the improvement of HSS scores compared to preoperative values between the two groups (both P>0.05). Preoperative TT-TG values were significantly higher in the DA≥12° subgroup than that in DA<12° group [12.7 (11.3, 15.3) vs 10.7 (8.3, 13.6)mm, P<0.001]. Patients with a preoperative TT-TG≥16 mm demonstrated greater DA than those with a TT-TG<16 mm (12.50°±4.70° vs 9.65°±4.61°, P=0.009); no statistically significant differences were found between the two groups in terms of HSS scores, Feller scores, or their postoperative improvements compared to preoperative values (all P>0.05). Conclusions: DA demonstrates a significant association with preoperative TT-TG, emphasizing the necessity of TT-TG evaluation during MB-UKA preoperative planning, particularly for cases with TT-TG>16 mm. Furthermore, DA critically influences postoperative clinical outcomes, with DA<12° being associated with favorable early functional recovery.

Background and purposeContemporary data on the risk of chronic pain after total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA) is limited. Therefore, we aimed to investigate the incidence of chronic pain, pain characteristics, patterns of analgesic use, patient satisfaction, and willingness to undergo the same surgery again, 1 year after primary TKA and UKA for osteoarthritis.MethodsWe conducted a nationwide online survey among unselected patients who underwent primary TKA or medial UKA for primary osteoarthritis in Denmark. At 1 year postoperatively, we assessed the incidence of moderate to severe pain (≥ 4 on the 0–10 numerical rating scale), frequency of pain, pain interference with everyday life, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain domain, the Douleur Neuropathique 4 interview (DN4i), use of analgesics, satisfaction, and willingness to undergo the same surgery again.ResultsWe sent survey invitations to 2,580 TKA patients and 1,007 UKA patients who underwent surgery in 2022. Of the 70% TKA respondents, 25% had moderate to severe chronic pain, 82% were satisfied/very satisfied with the result of surgery, and 86% indicated that they would choose to undergo surgery again. Of the 75% UKA respondents, 23% had moderate to severe chronic pain, 86% were satisfied/very satisfied, and 88% would undergo the same surgery again.ConclusionIn Denmark, 25% of TKA patients and 23% of medial UKA patients experienced moderate to severe knee pain after 1 year. These numbers were higher than most previous estimates. Most patients were satisfied with the result of surgery and would undergo the same surgery again.

To analyze meniscus allograft failure rates, timing, and mechanisms to characterize risk factors and identify modifiable variables that could be addressed to optimize outcomes after meniscus allograft transplantation (MAT). Using prospectively collected registry data, patients who underwent primary fresh MAT at a single institution between 2016 and 2023 with a minimum follow-up of 2 years were analyzed. Initial treatment failure was defined as re-operation, including partial or complete allograft removal, revision MAT, or conversion to unicompartmental or total knee arthroplasty. Treatment failure mechanisms included joint disease progression, meniscus tearing, meniscus extrusion, graft shrinkage, malunion/nonunion, and fixation failure. Treatment failure and nonfailure cohorts were compared, as well as failure mechanism subcohorts, based on patient sex, age, body mass index, laterality, nicotine use, concomitant procedures, graft preservation method, MAT technique, and adherence. A total of 61 patients with a mean age of 33 years (range, 15-62 years) and mean follow-up of 47.2 months (range, 24-88 months) were included. Thirteen patients underwent medial MAT and 44 patients underwent lateral MAT. Seven patients (11.5%) were found to have initial treatment failure at a mean of 18.1 months versus 54 patients (88.5%) who had functional graft survival. All failures involved medial MAT. Patients were more likely to experience treatment failure if they used nicotine (odds ratio [OR], 19.5) or had concomitant OCAT (OR, 8.8). The most common mechanism of failure was the progression of degenerative joint disease (n = 5, 71.4%), followed by meniscus tears (n = 2, 28.6%). Four failures underwent revision MAT, while three underwent TKAs. Two of the patients who underwent revision MAT remained as nonfailures at >2 years after revision surgery, resulting in a 91.8% overall MAT functional survival. Fresh MAT resulted in a high (92%) short- to mid-term functional survival rate, with nicotine use and concomitant cartilage restoration procedure(s) being significant risk factors for treatment failure; joint disease progression and meniscus allograft tears were the primary mechanisms of failure. Level III, cross-sectional analysis of prospectively collected registry data.

BackgroundThis study comprehensively and methodically assessed the effectiveness of proximal fibular osteotomy (PFO) compared to unicompartmental knee arthroplasty (UKA) as treatment for medial compartment knee osteoarthritis (KOA) to offer direction and evidence to support clinical surgical decision-making.MethodsLiterature screening was strictly conducted according to the inclusion criteria, and reasonable outcome indicators were selected from the included studies. The PubMed, Web of Science, Wanfang Data, CQVIP, and CNKI databases were searched using a predefined search strategy. Quality assessment was stratified by study design: the Cochrane Risk of Bias 2.0 tool for randomized controlled trials (RCTs) and the Newcastle-Ottawa Scale (NOS) for non-RCTs. After extracting relevant data from the included studies, a meta-analysis was performed using RevMan 5.4 software.ResultsThirteen studies involving 698 patients were included, with 355 and 343 patients in the PFO and UKA groups, respectively. The meta-analysis revealed that the PFO group had a shorter surgical duration, less intraoperative blood loss, shorter hospital stay, and lower hospitalization costs than the UKA group. Nevertheless, no statistically significant differences in the postoperative visual analog scale scores (VAS), Hospital for Special Surgery (HSS) scores, knee range of motion (ROM), Knee Society Score (KSS), femorotibial angle, and incidence of postoperative complications were observed between the PFO and UKA groups.ConclusionsPFO and UKA provide comparable short-term functional outcomes for medial compartment KOA, with PFO offering advantages in surgical efficiency and cost. However, given the high heterogeneity and limited long-term data, these findings should be interpreted cautiously, and further high-quality studies are needed to confirm the durability and broader applicability of PFO.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12893-025-03262-4.

Comparison of implant complications, lengths of stay, and costs among patients undergoing robotic-assisted versus conventional unicompartmental knee arthroplasty.

Unicompartmental Knee Arthroplasty for Isolated Compartment Osteonecrosis: A 20-Year Experience.

Periprosthetic Joint Infections After Unicompartmental Knee Arthroplasty Occur More Commonly in Patients Who Have Rheumatoid Arthritis.

Primary spontaneous osteonecrosis of the knee (SONK) is a debilitating condition that primarily affects elderly patients with an unknown etiology. Denosumab has emerged as a novel therapeutic agent for osteoporosis treatment. This study aimed to investigate whether denosumab improves knee function and osteoporosis in SONK patients undergoing unicompartmental knee arthroplasty (UKA). Between January 1, 2018, and December 31, 2022, patients with knee osteonecrosis undergoing UKA were enrolled. Thirty-five patients (Group A) received vitamin D3 and calcium supplements only, while 36 patients (Group B) received subcutaneous denosumab (60 mg every 6 months) plus supplements. Patients were evaluated through serum biomarkers, clinical examination, radiography, and MRI. A predictive model was developed using the least absolute shrinkage and selection operator (LASSO) regression. The mean follow-up was 2.11 ± 0.99 years. One patient developed tibial plateau collapse and fibular head fracture. At 24 months, Group B showed significantly better HSS scores (T = 15.07, P = 0.04), VAS scores (T = 1.11, P = 0.04), and ROM (T = 15.07, P = 0.02) compared to Group A. Group B exhibited higher PTH levels at 12, 18, and 24 months, and higher OCN levels at 18 and 24 months. At 24 months, Group B had lower CTX but higher T-scores and BMD. Radiographic analysis revealed component malposition in some cases, with a mean postoperative femoral angle of 176.1° ± 2.3°. The prediction nomogram incorporating CTX, BMD, and ROM showed excellent discrimination (C-index = 0.925, 95% CI: 0.881-0.969), confirmed by internal validation (C-index = 0.97). Clinically, the 7-point improvement in HSS scores observed in Group B corresponds to a transition from 'poor' to 'good' knee function, while the 0.8-unit increase in femoral neck T-score translates into a 30% reduction in major-fracture risk over 10 years (FRAX-adjusted), indicating meaningful gains in patient mobility, pain relief, and long-term skeletal protection.

Registry data suggests that robotic-assisted unicompartmental knee arthroplasty (rUKA) significantly reduces all-cause revisions compared to conventional implantation (cUKA). This study aims to compare joint line-related parameters and their reconstruction accuracy between rUKA and cUKA. Five databases were searched using a pre-defined strategy and inclusion criteria: (1) comparative studies reporting radiological outcomes, (2) human studies, (3) English language, and (4) meta-analyses for cross-referencing. Cadaveric or saw-bone studies were excluded. Data extracted included demographics data, pre- and postoperative radiological parameters (HKA, MPTA, LDFA, posterior tibial slope, femoral sagittal angle, joint line height, implant congruency), and outliers. A random-effects meta-analysis was conducted using mean difference (MD) and odds ratio (OR) as main effect estimators. Risk of bias was assessed using the Newcastle-Ottawa Scale (NOS), and publication bias was evaluated with funnel plots. A total of 18 studies assessing 2470 patients (1112 rUKA, 1358 cUKA) were included in the analysis. No significant baseline differences were found in age, sex, BMI, follow-up period, MPTA, LDFA, or tibial slope. Postoperative radiological parameters showed no significant differences between groups for HKA, LDFA, MPTA, or tibial slope (p > 0.05). Joint line height was significantly lower in cUKA compared to rUKA (MD = -1.37mm, 95% CI: -2.06 to -0.69, p < 0.001). Outlier analysis revealed that rUKA had significantly fewer outliers across relevant radiological parameters, including HKA, joint line height, tibial slope, femoral flexion, femoral implant congruency, and medial, anterior, and posterior tibial congruency. Reporting pre- and postoperative mean alignment parameters undermines patient-specific anatomy reconstruction with advanced technologies. Outlier reporting showed significant variability, with limited evidence supporting its clinical relevance. Future studies should focus on patient-specific reconstruction and define clinical thresholds for outliers.

Unicompartmental knee arthroplasty (UKA) and high tibial osteotomy (HTO) surgeries are often preferred in individuals with medial knee osteoarthritis (OA). The aim of the study was to compare the functional outcomes of patients with UKA and HTO. Seventy-seven individuals were included in the study, of which 39 individuals had undergone HTO surgery (median age = 58.38 ± 7.99, median body mass index [BMI] = 30.93 ± 3.33 kg/m2) and 38 individuals had undergone UKA surgery (median age = 62.95 ± 7.74 years, median BMI = 30.48 ± 3.57 kg/m2). Pain was evaluated before and after surgery. Pain severity, 6-Minute Walk Test (6MWT), 10-Repetition Sitto-Stand Test (10 × STS), stairs test, Timed Up and Go (TUG), and Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire were used for functional evaluation. There were no differences in demographic characteristics between groups (p > 0.05). The HTO group had lower postoperative pain (p = 0.043) and KOOS pain subscale scores (p = 0.043), better stairs test (p = 0.041), and 10 × STS results (p = 0.007). There were no significant differences between the groups in terms of the 6MWT, TUG, and KOOS total scores (p > 0.05). The results showed that individuals who underwent HTO surgery experienced less postoperative pain and had better functional levels compared with those who underwent UKA surgery. It shows that good functional performance can be achieved with HTO surgery in early medial compartment OA.

BackgroundPeriprosthetic fractures (PPFs) following unicompartmental knee arthroplasty (UKA) are a significant clinical challenge. Tibial component positioning may influence fracture risk, but the biomechanical effects of varus inclination on fracture loading remain unclear.MethodsWe investigated the effect of tibial component varus inclination on fracture load using the Oxford® Partial Knee implant system, synthetic tibiae and a dynamic loading model. Tibial components were implanted at neutral (0°), 3° and 6° varus angles. Vertical loading was applied until fracture and fracture loads were compared between groups.ResultsA 3° varus position significantly increased fracture load by 34% compared to neutral (p < 0.05). No further statistically significant increase was observed at 6° varus. The dynamic model suggested that the mobile meniscal bearing may contribute to an improved load distribution, thereby increasing fracture resistance.ConclusionSlight varus inclination of the tibial component in UKA increases the medial tibial fracture load, potentially reducing the risk of PPF. Our findings highlight the biomechanical advantages of controlled varus positioning and provide insight into optimizing implant alignment.

Background: Unicompartmental knee arthroplasty (UKA) represents a well-recognized treatment option for isolated medial compartment osteoarthritis; however, the debate regarding the superiority of fixed-bearing versus mobile-bearing designs continues. We aimed to evaluate the mid- to long-term outcomes of medial UKA comparing mobile- versus fixed-bearing designs within a single institution over an average 10-year follow-up. Methods: This retrospective study included 81 consecutive patients who underwent primary medial UKA (45 fixed-bearing and 36 mobile-bearing) with a minimum five-year follow-up. Clinical outcomes were measured using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score and range of motion (ROM). Radiological measurements included hip-knee-ankle axis angle (HKA) and osteoarthritis progression. Implant survivorship was evaluated using Kaplan–Meier analysis, with failure defined as either conversion to total knee arthroplasty (TKA) or polyethylene (PE) exchange. Results: At a mean follow-up of 10.6 years, WOMAC scores, ROM, and radiological outcomes showed no statistically significant differences between the fixed-bearing and mobile-bearing groups. Significantly higher failure rates were observed in the mobile-bearing group, both when considering conversion only (p = 0.041) and when including conversion or PE exchange (p = 0.009). Survival analysis demonstrated 10-year rates of 97.8% for fixed-bearing and 88.9% for mobile-bearing with TKA conversion defined as failure (p = 0.066). Using combined failure criteria of TKA conversion or PE exchange, 10-year survival rates were 97.8% for fixed-bearing and 83.3% for mobile-bearing (p = 0.015). Conclusions: At a mean 10.6-year follow-up, clinical and radiological outcomes were comparable, but fixed-bearing UKA demonstrated superior survivorship.

Background:A periprosthetic tibial fracture (PPTF) is a known complication of medial unicompartmental knee arthroplasty (mUKA). Treatment options include conversion to total knee arthroplasty (cTKA), open reduction internal fixation (ORIF), and nonoperative treatment. The risk of reoperation after initial treatment of PPTFs is not well examined. Given the rise of cementless mUKA and its association with early (≤4 months), likely surgery-related fractures, this group is particularly interesting. The aim of this study was to (1) report the 2-year risk of reoperation according to initial treatment and (2) report the need for delayed conversion to TKA (dcTKA) after ORIF or nonoperative treatment, or the need for revision TKA (rTKA) after cTKA.Methods:Using data from the Danish Knee Arthroplasty Register and the Danish National Patient Register, all PPTFs after mUKAs between 1997 and 2022 were included and stratified by treatment. Subsequent reoperations and need for dcTKA or rTKA within 2 years were outcomes.Results:We identified 177 PPTFs after mUKA with complete 2-year follow-up. When the treatment of the PPTF was cTKA (69 cases), 5 cases (7%) underwent reoperation and fewer than 5 required rTKA. For nonoperative treatment (46 cases), 13 cases (28%) underwent reoperation, with 10 cases requiring dcTKA. When treated with ORIF (62 cases), 25 cases (40%) underwent reoperation, with 19 cases requiring dcTKA. PPTFs after cemented mUKA were mostly late PPTFs (70%) and were often treated nonoperatively, where PPTFs after cementless mUKA were often early PPTFs (74-78%) and very rarely treated nonoperatively. Fixation of mUKA was not associated with the risk of reoperation within each treatment group. Among 74 early PPTFs after cementless mUKA, 35 cases were treated with cTKA with fewer than 5 reoperations within 2 years and 0 cases needing rTKA. In contrast after ORIF (39 cases), 16 cases (41%) underwent reoperation, with 12 cases requiring dcTKA.Conclusion:PPTFs treated with ORIF were associated with higher rates of reoperation and need for dcTKA compared with PPTFs treated with cTKA and nonoperative treatment. These data suggest that careful consideration is needed before using ORIF as treatment. However, the unknown fracture severity precludes definitive attribution of reoperation to the treatments.Level of Evidence:Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.