Abstract
Background
To improve implant positioning in total knee arthroplasty (TKA) patient-specific instrumentation (PSI) has been introduced as alternative for conventional instrumentation (CI). Though the PSI technique offers interesting opportunities in TKA, there is no consensus about the effectiveness of PSI in comparison with CI and results concerning soft-tissue balancing remain unclear. Therefore, the primary aim of the present study was to investigate the varus-valgus laxity in extension and flexion in patients receiving a TKA using PSI compared with CI. Additionally, radiological, clinical and functional outcomes were assessed.
Methods
In this prospective randomization controlled trial, 42 patients with osteoarthritis received a Genesis II PS (Smith & Nephew, Memphis, Tennessee), with either PSI (Visionaire, Smith & Nephew) or CI (Smith & Nephew). Patients visited the hospital preoperative and postoperative after 6 weeks, 3 and 12 months. One-year postoperative varus-valgus laxity was measured in extension and flexion on stress radiographs. Additional assessments included: the hip-knee-ankle angle on long-leg radiographs, femoral and tibia component rotation on CT-scans, radiolucency, the Knee Society Score (KSS), VAS pain, VAS Satisfaction, Knee injury and Osteoarthritis Outcome score (KOOS), Patella score (Kujala), the University of California Los Angeles activity score (UCLA), the anterior-posterior laxity in 20° and 90° knee flexion, adverse events and complications. The outcome measures were compared using independent t-tests, non-parametric alternatives and repeated measurements, with a significance level of p<0.05.
Results
In four cases intra-operative modifications were needed, since the PSI did not fit correctly on the tibia and/or femur. No significant differences were found between the two groups for varus-valgus laxity in both extension and flexion (figure 1), as well as for the other radiological outcomes. Both groups improved significantly on clinical and functional outcomes over time. No significant differences were found between the groups one year postoperatively. Finally, the PSI group received a thinner insert than the CI group (p=0.04).
Conclusion
In conclusion, PSI in TKA does not result in better varus-valgus laxity, and clinical and functional outcomes compared with CI, one year postoperative. Since the PSI group received a thinner insert, the pre-operative surgery plan developed for he PSI probably provides more conservative bone cuts compared with CI. The thinner insert might be beneficial in the long-term; however, further research is needed to gain more insight in the long-term results of PSI.
