Functional outcomes of patient-specific instrumentation versus conventional instrumentation for unicompartmental knee replacement: A systematic review and meta-analysis
The Knee · 25 Aug 2026
† Impact is the editorial-priority score. All scores are out of 100. Clinical is a stored clinical-importance score from the earlier method; it has not been recalculated.
Why it matters
PSI is being marketed as a way to improve component positioning and outcomes in UKA, so trainees should know the current pooled functional evidence does not support any advantage over standard instrumentation.
The evidence
This systematic review and meta-analysis compared patient-specific instrumentation (PSI) with conventional instrumentation (cUKA) in unicompartmental knee replacement, pooling 14 studies (1,680 knees, 1,670 patients: 5 RCTs and 9 retrospective comparisons). At 1-year follow-up, Oxford Knee Score was essentially the same between groups (mean difference 0.9, 95% CI -2.65 to 4.45, I2=0%), and secondary scores (KSS, KOOS) also showed no significant differences at 3 months or 1 year; revision rates were numerically higher with PSI (6% vs 2.3%) but too heterogeneous to pool statistically.
Oxford Knee Score at 1 year: Mean difference 0.9 (95% CI -2.65 to 4.45; OKS). The interval includes no difference. This does not establish equivalence or rule out an important effect.
Why this rigour score?
Meta-analysis (mixed designs)Design starting point: 42.6
Raised the score
- Prospectively registered+5.1
- Compared against current standard of care+3.4
Lowered the score
- No assessment of publication bias across 14 studies−6.8
- Pools mixed study designs−3.4
Score capped at 42. Two or more critical methodological failures for a review.
Methods at a glance
Recorded assessment- Comprehensive literature searchMet
- Risk of bias assessedMet
- Bias considered in synthesisMet
- Publication bias assessedNot met
- Study exclusions justifiedNot met
- Prospective registrationMet
Not reported does not mean not done. Checks have different weights; this is not a count of boxes ticked.
See the full score breakdown
- Study design starting point
- 42.6
- Compared against current standard of care
- +3.4
- Prospectively registered
- +5.1
- Pools mixed study designs
- −3.4
- Comprehensive literature search
- +3.4
- Risk of bias assessed in the included studies
- +3.4
- Risk of bias carried into the synthesis
- +2.5
- No assessment of publication bias across 14 studies
- −6.8
- Author royalties on the device under study
- −3.4
- Methodological cap
- −4.9
- Final rigour score rounded
- 42 / 100
Study design sets the starting point and a ceiling of 82. Recorded methods then adjust the score. Points are shown to one decimal place; the final score uses unrounded values.
Checklist from the stored appraisal. “Not met” describes the recorded criterion; it does not always produce a deduction. This overview supports reading the full study.
For journal club
1.If PSI does not improve patient-reported function at 1 year, should its added cost and preoperative imaging burden change how surgeons select instrumentation for UKA candidates?
2.Given the higher (though unpooled) revision rate with PSI, particularly aseptic loosening, how should this influence counselling of patients considering UKA with custom guides versus conventional technique?
Original publication title
Functional outcomes of patient-specific instrumentation versus conventional instrumentation for unicompartmental knee replacement: A systematic review and meta-analysis