The effect of tibio‐femoral over‐distraction in primary knee arthroplasty

Purpose Overstuffing the patellofemoral joint has been associated with poor post‐operative outcomes. No study has assessed the effect of over‐distracting the tibio‐femoral joint in the vertical plane and its effects on function and quality of life. The purpose of this study is to assess the effect of tibio‐femoral joint distraction on function and quality of life after total knee arthroplasty. Methods Measurements of knee joint distraction were devised using long‐leg alignment radiographs. Seventy‐three patients were prospectively recruited and their joint distraction measured post‐operatively. A comparison was made between the level of joint distraction and functional outcomes as measured by the International Knee Society score and its components, such as pain and flexion, and the Knee injury and Osteoarthritis Outcome Score and quality of life as measured by the Short‐Form 12 score. Twelve‐month follow‐up was achieved. Results Knee joint over‐distraction post‐arthroplasty correlated significantly with Knee Society score ( p = 0.041), flexion ( p = 0.005) and pain ( p = 0.002). Those knees that were over‐distracted post‐operatively suffered more pain, less flexion and a lower International Knee Society score compared with their counterparts. No correlation was found between over‐distracting the knee joint and quality of life. Conclusion Over‐distracting the tibio‐femoral joint during arthroplasty is a significant predictor of reduction in function and increase in pain in the short to medium term. When between sizes of tibial inserts, the surgeon should consider using the thinner option. Level of evidence Prospective cohort study, Level II.