Comprehensive Literature Review: Clinical Evidence, Outcomes, and Best Practices for Lateral Unicompartmental Knee Arthroplasty
Lateral unicompartmental knee arthroplasty (UKA) is underutilized despite strong contemporary evidence showing high survivorship (~95% at ~10 years), excellent patient-reported outcomes, and low serious complication rates. Fixed-bearing designs demonstrate superior long-term performance compared to mobile-bearing systems, which have higher rates of bearing dislocation. When properly indicated and performed with appropriate alignment targets, lateral UKA offers excellent functional outcomes and high return-to-activity rates.
Evidence for long-term implant performance across different designs and techniques
Failure modes, revision patterns, and risk mitigation strategies
Evidence comparing lateral UKA to total knee arthroplasty and other treatment options
Comparative analysis of robotic-assisted and conventional surgical techniques
Scope and study-design landscape: The evidence spans registry analyses, large single- and multicenter series, robotic and conventional cohorts, matched-pairs comparisons of implant design, and systematic reviews/meta-analyses. Fixed-bearing (FB) and mobile-bearing (MB) lateral UKA are both represented, with growing evidence for FB designs and robotic-arm assistance, and clearer characterization of MB-specific failure (bearing dislocation).
| Study | Design/Setting | n (knees) | Implant/Technique | Mean/Median Follow-up | Notes |
|---|---|---|---|---|---|
| Danish Registry (valgus knees): Lateral UKA vs TKA [1] | National registry, propensity-matched to TKA | 538 L-UKA | Mixed (registry) | Up to 25 years of data (1997—2022) | 5-yr cumulative revision risk 10.1% LUKA vs 5.0% TKA; LUKA improved by era to 7.3% in recent decade |
| FLO (Fixed Lateral Oxford), consecutive [2] | Single-designer center | 305 | Fixed-bearing, cemented | 4.3 years (1—8) | 93% within indications; isolated lateral OA 98% |
| Oxford Domed Lateral MB, consecutive [6] | Designer center | 325 | Mobile-bearing, domed | Median 7 years (3—14) | 10-yr survival 85%; 4% bearing dislocation revisions; 4% medial OA revisions |
| ODL MB, non-designer [4] | Single-center | 115 | Mobile-bearing (ODL) | Up to 10 years | 10-yr survival 74.8% (95% CI ~65—unknown); OKS, FJS, TAS reported |
| FB cemented, min 10 years [5] | Single center | 96 | Fixed-bearing, cemented | Mean 14.5 years | Survivorship 94.7%; OA progression main reason for revision |
| Long-term single-surgeon (22.5 y) [11] | Single center | — | Mixed (likely FB focus) | Mean 22.5 years | "Robust survival" and functional success; details in full text |
| FB vs MB matched pairs [12] | Single center | 60 + 60 | MB vs FB | ~3 years | FB superior survivorship/clinical outcomes vs MB |
| Non-designer FB cohort [19] | Single center | 133 | FB (Oxford Fixed Lateral) | 3.3 years | Survival 98.5%; significant PROMs gains |
| Robotic fixed-bearing, 10-year [10] | Single surgeon | 77 | Robotic, cemented FB | 10.2 years | 10-yr survivorship 96.1%; pain/progression main failures |
| Robotic vs conventional 5-year [22] | Two cohorts | 95 | Cemented; Robotic vs Conventional | ~7.5—8 years | Similar survivorship and KOOS at 5 years |
| RA-PKA mixed (medial/lateral) [47] | Multi-indication | 171 lateral | Robotic, fixed-bearing | 4.7 years | 5-yr survivorship of lateral UKA 97.7% |
| Systematic reviews/meta-analyses [24,33,35,39,53] | Meta-analyses | 20+ studies | Mixed | — | Pooled survivorship by timebands; failure modes; MB dislocation risk (domed vs flat tibia) |
| Meniscectomy OA vs primary OA [20,25] | Matched case—control | 42 and 38 | Mixed | ~7—unknown years | Meniscectomy OA outcomes comparable to primary lateral OA |
| Alignment effects [30,40] | Single centers | — | Mixed | ~2—8 years | Malalignment (postop mild valgus/varus) associated with worse outcomes; target mild valgus |
Pooled and study-level survivorship data comparing different implant designs and surgical approaches across multiple time intervals
| Timepoint | Fixed-bearing (FB) | Mobile-bearing (MB) | Robotic-assisted (mostly FB) | Meta-analytic pooled estimates |
|---|---|---|---|---|
| 3-5 years | 98.5% at 3.3 y (FB non-designer) [19]; 5-yr RA lateral 97.7% [47] | Mid-term MB multicenter (363 cases) supports good mid-term, details in full text [9] | 5-10 y: RA vs conventional similar 5-y survivorship [22] | 3-y 96%, 5-y 95% [24]; corroborated by [33,39] |
| 8-10 years | 96.1% at 10.2 y (robotic FB) [10] | 10-y ODL MB 85% (designer) [6]; 10-y ODL MB 74.8% (non-designer) [4] | 10-y 96.1% (single-surgeon RA FB) [10] | 10-y 89% pooled [24]; systematic review supports high mid-term survivorship [39] |
| ≥14-15 years | 94.7% at mean 14.5 y (FB cemented) [5] | — | — | 15-y 85.5% pooled [24] |
| Registry comparators | — | ODL mid—long term in NJR [3] | — | Mid-term equivalence medial vs lateral UKA in NJR [31] |
| Registry vs TKA | — | — | — | Danish: 5-y cumulative revision risk 10.1% LUKA vs 5.0% TKA; improved to 7.3% for LUKA in modern era [1] |
Detailed analysis of patient-reported outcomes, functional improvements, return to activity, and factors associated with success
Significant, clinically meaningful improvements in OKS, KOOS, KSS, pain VAS, and ROM are consistently reported after lateral UKA (FB and MB), with high satisfaction [5,6,10,12,19,22,29,36,46].
Median OKS 43; 80% good/excellent [6]
Improved ROM, VAS, KSS; excellent survivorship [5]
OKS, AKSS-O, ROM, VAS improved significantly [19]
High satisfaction with durable survivorship [10]
Good/excellent WOMAC and OKS in majority; no revisions in cohort at ~6.5 years [29]
Mild—moderate PF degeneration does not impair short-term PROMs (Kujala, KOOS JR) after lateral UKA [36,46]
| Study | Cohort | Metric | Result |
|---|---|---|---|
| Young patients ≤60 y, FB [48] | 37 patients | Return-to-activity; UCLA; TAS; OKS | Return-to-activity 87.5%; 49% UCLA ≥7; all clinical parameters improved at ~3 years |
| Athletes, lateral parapatellar approach [34] | 50 LUKA | Return to moderate/vigorous sports | High rates of return at 2—11 years (details in full text) |
| Robotic FB, 10-year [10] | 77 knees | Satisfaction, pain | High satisfaction; durable pain relief |
Overall: Lateral FB-UKA supports high rates of return to moderate activity in appropriately selected patients; evidence in younger patients indicates robust return-to-activity with careful expectations on high-impact sports [34,48].
Postoperative mild valgus appears optimal; varus or overcorrection associated with worse function and survivorship [30,40]. One cohort found postoperative valgus ≤3° associated with best WOMAC/KSS, while varus ≥3° worst; excessive undercorrection also detrimental [40].
Acceptable survivorship even in younger cohorts when well indicated; MB failures in younger active patients often dislocation-driven [26,48].
BMI >30 not a contraindication for FB lateral UKA; satisfactory outcomes with low revision rates reported [29].
Mild—moderate PF joint changes not associated with inferior short-term PROMs after lateral UKA [36,46].
Post-meniscectomy OA and post-traumatic OA can achieve outcomes and survivorship comparable to primary idiopathic lateral OA when appropriately selected [20,25,37].
Comprehensive comparison of lateral UKA versus total knee arthroplasty for isolated lateral osteoarthritis
| Comparator | Key Findings | Evidence Level |
|---|---|---|
| Registry (valgus knees): LUKA vs TKA | 5-year cumulative revision risk lower for TKA overall (5.0%) than LUKA (10.1%); LUKA improved in modern era (~7.3%), narrowing gap | High - Registry data |
| Institutional matched cohorts | Lateral UKA shows advantages in perioperative metrics (blood loss, LOS) and early pain/function vs TKA in isolated lateral OA | Moderate - Matched studies |
| Meta-analysis (LUKA vs TKA in isolated lateral OA) | LUKA reduces blood loss and length of stay; better VAS pain and knee function metrics; operative time similar | Moderate - Meta-analysis |
The optimal comparator for valgus/lateral disease realignment is distal femoral osteotomy (DFO); however, DFO-specific comparative cohorts were not identified in the included literature. HTO is not the appropriate comparator for valgus/lateral OA and is not discussed here.
Outcomes for lateral UKA in secondary osteoarthritis conditions
Comprehensive comparison of bearing design philosophies and clinical outcomes
Critical assessment of current research limitations and future research needs
Few datasets quantify national incidence by laterality; Danish registry provides one estimate (n=538 over 25 years), underscoring the low uptake relative to candidacy. More comprehensive utilization data needed.
Long-term registry-grade survivorship stratified by bearing design and robotic assistance remains limited; NJR reports specifically on ODL MB but more lateral-specific registry stratification is needed.
Direct comparative effectiveness vs distal femoral osteotomy (for valgus/lateral disease) is lacking in the included set; future studies should prioritize this comparison.
Heterogeneity in failure definitions and survivorship methods (e.g., all-cause revision vs component revision) complicates cross-study pooling; meta-analyses mitigate but cannot fully harmonize differences.
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