The role of posterior condylar offset ratio on clinical and functional outcome of posterior stabilized total knee arthroplasty: a retrospective cohort study

Background Postoperative Range of Motion (ROM) is an important measurement of the success of a Total Knee Arthroplasty (TKA). Much enthusiasm has been recently directed toward the posterior femoral condylar offset (PFCO), with some authors reporting increasing postoperative knee flexion when increasing PFCO. The aim of this study is to retrospectively determine the effect of the PFCO on the clinical and functional outcome of a cohort of patients who underwent a Posterior Stabilized (PS) TKA. Methods Clinical and radiological data of all patients who underwent TKA with PS implant for primary osteoarthritis were retrospectively reviewed. Knee Society Score (KSS), knee ROM, PFCO ratio (PFCOR), and tibial slope (TS) were measured pre and postoperatively. Results One hundred and twenty-one patients (141 knees) met the inclusion criteria. The mean knee flexion increased from 98 ± 20.2° (range 30–130) to 123 ± 12.1° (range 70–140) and the mean KSS increased from 74.0 ± 3.3 (range 27–130) to 203.9 ± 8.1 (range 26–249). Postoperative PFCOR and TS were 0.492 ± 0.005 (range 0.40–0.57) and 2.36 ± 0.56° (range − 10.9–12.15°), respectively. Neither maximal flexion angle nor KSS showed a significant correlation with postoperative PFCOR (Pearsons’r = − 0.057, p = 0.5 for flexion angle and Pearsons’r = − 0.073, p = 0.5 for KSS) or with postoperative TS (Pearsons’r = 0.042, p = 0.62 for flexion angle and Pearsons’r = 0.002, p = 0.98 for KSS). Conclusion Posterior femoral condylar offset remains an important parameter and, especially when using anterior femoral referencing TKA, care must be taken to prevent excessive resection of the posterior femoral condyles.