Introduction Lateral retinacular release (LRR) is a common procedure during total knee arthroplasty (TKA), especially if patellar maltracking is observed intraoperatively. The impact of LRR on patellofemoral kinematics is well-examined, but the influence on femorotibial kinematics requires more elucidation. Therefore, the aim of this study was to evaluate the effects of LRR on femorotibial kinematics in vitro. Materials and methods A fixed bearing TKA was implanted in six human knee specimens. Femorotibial kinematics were measured dynamically through the use of a custom-constructed knee rig which flexes the knee from 20° to 120° under weight bearing conditions. Measurements were performed before and after LRR. LRR was performed completely including transection of synovium, retinaculum and tractus fibers. For the registration of tibiofemoral kinematics a 3-dimensional- ultrasound-based motion analysis system was used. Results LRR revealed a significant reduction of femoral rollback at the lateral compartment (9.4 ± 5.0 vs 7.8 ± 9.4 mm; p<0.01), whereas the present decrease of femoral rollback at the medial compartment was not significant (3.4±4.7 vs 2.3 ±5.9 mm; p = 0.34). Accordingly, LRR significantly reduced internal rotation of the tibia (0.8°; p < 0.01). Conclusion The results suggest that LRR significantly decreases lateral femoral rollback as well as internal rotation of the tibia, probably by changing the tension of the iliotibial band. When performing a LRR in clinical routine, surgeons should be aware of altering not only patellofemoral kinematics but also the femorotibial kinematics.
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