The influence of patello-femoral overstuffing after modular unlinked bicompartmental knee arthroplasty (BiKA) for medial tibio-femoral and patello-femoral osteoarthritis of the knee.

BACKGROUND: The factors affecting results after bicompartmental knee arthroplasty (BiKA) have not been fully elucidated. This major ligament-preserving procedure may be more susceptible to overstuffing of the patello-femoral (PF) joint than the major ligament-sacrificing total knee arthroplasty. Currently, we investigated the effect of PF overstuffing after BiKA on its clinical outcome.

METHODS: There were 71 patients (74 knees) who underwent modular unlinked BiKA at our clinic who had a follow-up of 5 to 9 years. Final follow-up results were assessed by evaluating knee range of motion (ROM), the 2011 Knee Society Score (2011KSS), Japanese Knee Osteoarthritis Measure, and radiological findings. The degree of postoperative PF overstuffing was evaluated by computed tomography (CT) and magnetic resonance images (MRI) for 55 knees, and the correlation between the degree of overstuffing and postoperative clinical results were examined.

RESULTS: Overall clinical results improved significantly after surgery without any revision cases. The X-ray measurements showed the improved coronal alignments and the appropriate implant installation angles. The CT and MRI measurements revealed that higher degree of postoperative PF overstuffing caused by insufficient amount of osteotomy on the anterior surface of the femur correlated with worse postoperative total 2011KSS at 2 years after surgery (rs = -0.387, P = 0.004), as opposed to no correlation at the time of the final follow-up (rs = 0.068, P = 0.623).

CONCLUSION: Modular unlinked BiKA provided patients with a high level of satisfaction and functional improvement over 5 to 9 years postoperatively. However, because PF overstuffing affects initial patient satisfaction, the amount of osteotomy should be determined carefully during the surgery.