Influence of patellar subluxation on ligament balancing in total knee arthroplasty through a subvastus approach. An in vivo study.

Post-operative joint stability and ligament balance are crucial factors in the longevity of the prosthesis after total knee arthroplasty (TKA). The influence of patellar position on the balance of the knee is controversial. We studied the influence of patellar subluxation on tibiofemoral pressure distribution in vivo, in 32 knees undergoing TKA through a subvastus approach. We used the e-LIBRA Dynamic Knee Balancing System (Synvasive Technology, El Dorado Hills, CA, USA). This is a device that measures the pressures in the medial and lateral compartment independently. After balancing the knee in flexion with the patella in place, we demonstrated a significant rise in pressure in the medial compartment with subluxation of the patella (p < 0.0001). Our findings give a new insight on the role of the patellar position while balancing a total knee arthroplasty. Surgeons should be aware of this effect when choosing their surgical technique for this operative procedure.