Abstract
Background
Osteophytes in the posterior compartment of the knee pose a challenge in achieving soft tissue balance during total knee arthroplasty (TKA). Previous investigations have demonstrated the importance of various factors involved in obtaining flexion and extension gap balance, including the precision of femoral and tibial bone cuts as well as tensioning of the supporting pericapsular soft tissue structures (ligaments, capsule, etc.). However, the role of posterior compartment osteophytes has not been well studied. We hypothesize that space-occupying posterior structures affect soft tissue balance, especially in lesser degrees of flexion, in a cadaveric TKA model.
Methods
Five cadaveric limbs were acquired. CT scans were obtained of each specimen to define the osseous contours. 3D printed specimen-specific synthetic osteophytes were fabricated in two sizes (10mm and 15mm). Posterior-stabilized TKAs were performed. Medial and lateral contact forces were measured during a passive range of motion using OrthoSensor ® (Dania Beach, FL) technology. For each specimen, trials were completed without osteophytes, and with 10mm and 15mm osteophytes applied to the posterior medial femur, with iterations at 0°, 10°, 30°, 45°, 60°, and 90° of flexion. These were recorded across each specimen in each condition for three trials. Tukey post hoc tests were used with a repeated measures ANOVA for statistical data analysis.
Results
The presence of posterior medial osteophytes increased asymmetric loading from 0°– 45° of flexion. The 25–75% bounds of variability in the contact force was less than 3.5lbs.
Conclusions
In this cadaveric TKA model, posterior femoral osteophytes caused an asymmetric increase in contact forces from full extension continuing into mid-flexion. To avoid unnecessary soft tissue releases, we recommend early removal of posterior femoral osteophytes prior to performing ligament releases to obtain desired soft tissue balance during TKA.
