A systematic review and meta-analysis of clinical studies assessing alignment outcomes in patient-specific instrumented (PSI) knee arthroplasty was conducted.

PRISMA compliant data was extracted from literature databases up to January 2014.

Twenty-six studies met the inclusion criteria, reporting a total of 1792 knees. Twenty-three studies reported alignment outcomes in the coronal plane, 11 in the sagittal plane. In all but three series, MRI was the preoperative imaging modality. Range of mean postoperative alignment (hip–knee–ankle [HKA] angle) was 176.5 to 181.70. The proportion of three degrees of outliers showed an overall mean of 18.6%. In total, fifteen studies compared alignment outcomes between standard and PSI. From these, four studies showed significantly higher accuracy of coronal plane alignment with PSI (HKA angle). Meta-analysis of seven high-quality comparative studies demonstrated no significant increased accuracy in postoperative mechanical axis (HKA angle) with PSI. Subgroup meta-analysis of both femoral and tibial rotation was not feasible due to a low number of inclusive high-quality series.

PSI knee arthroplasty is shown not to confer increased accuracy in reconstituting the postoperative mechanical axis. Further studies are required to demonstrate both clinical and radiological alignment outcomes in PSI knee arthroplasty with focus upon tibial and femoral rotation.

Level 2 – meta-analysis.