Influence of Lateral Retinacular Release in Realigning the Patella Between Varus and Valgus Knees in Primary Total Knee Arthroplasty.

Abstract

Our study aims to find the role of lateral retinacular release (LRR) on realigning the patella in knees with maltracking during primary total knee arthroplasty. We also compared the patellar morphological factors between the varus and valgus knees on predicting the need for LRR. We have retrospectively analyzed the incidence of LRR in consecutive 152 primary TKA (124 patients) from May 2018 to December 2018. We have evaluated the preoperative radiological parameters like Wiberg's patellar morphological type, patellar angle, sulcus angle, patellar width and thickness, preoperative patellar tilt and patellar shift, lateral patellofemoral angle and congruent angle. Post-operatively, patellar shift and patellar tilt were measured. Multivariate regression analysis was used to find the association of LRR with the individual radiological parameters. There was no statistical difference in the postoperative patellar shift and tilt between lateral released and non-released groups, suggesting realignment of the patella after LRR (p > 0.05). The morphological parameters like patellar shift, lateral patellofemoral angle and congruent angle were significantly increased in valgus knees compared to varus knees (p < 0.05). The preoperative patellar shift of > 3.5mm have a specificity of 93.7% and a negative predictive value (NPV) of 92.7%, congruent angle > 16° have a specificity of 85.3% and NPV of 4.2% in varus knees in predicting LRR. Radiological parameters of patellar maltracking like increased patellar tilt and lateral patellar shift get corrected postoperatively after performing the lateral release. Patella with Wiberg type 3 morphology, patellar shift > 3.5mm and congruent angle > 16° in axial view tend to have an increased chance of lateral retinacular release.