The Influence Of Postoperative Tibial Inclination On The Clinical Results Of Unicompartmental Knee Replacement

Purpose: To evaluate the influence of postoperative tibial inclination on coronal plane on the clinical results assessed by the Hospital for Special Surgery Knee Score and range of knee motion in patients who were diagnosed with anteromedial osteoarthrtis.Methods: We performed a retrospective clinical and radiographic evaluation of 129 patients(172 knees)in the second hospital of Dalian medical university between July 2013 and June 2016 to assess the clinical outcome of unicompartmental knee repalcement performed with minimally invasive surgery using Oxford phase 3 system.Patients were assessed with the the Hospital for Special Surgery Knee Score and range of knee motion preoperatively.Two raters who were orthopaedic doctors measured each digital image according to Oxford? Partial Knee Manual of the Surgical Technique.We recorded the following radiographic parameters:femoral varus/valgus,femoral flexion/extension,tibial varus/valgus and posterior tibial slope on the coronal and sagittal plane respectively using Radi Ant DICOM Viewer.For each patient,the HSS score and ROM were recorded at the time of follow-up.All patients were available for evaluation at final follow-up.Short-film anterior-posterior radiographs and latero-lateral radiographs were performed to determine these positions.For tibial implant alignment paremeter measured,mean measurements of tibial varus/valgus were grouped at consecutive 2°intervals,when lefted other three angles were within accepted limits.Interval groups of tibial varus/valgus used the analysis of variance to analyse post-operative HSS and range of motion.Each group for tibial component alignment compared preoperative HSS and ROM with post-operative HSS and ROM using paried t test.Also,the independent t test was required between postoperative HSS and group varus and valgus,used for comparing postoperative HSS and within /without the target range.Results: 129 patients(172 knees,male: female,22:107)of medial UKA were enrolled during the follow-up,which averaged 15.7 months(range,1~34 months).There were 81 right knees and 91 left knees in this study.All patients were available at final follow-up.The average preoperative range of motion was 109.23°(90°~135°).The average postoperative range of motion was 122.61°(90°~144°).Significant differences were observed between pre-and post-operative ROM.The mean HSS score increased from 61.17 points(39 points to 84 points)preoperatively to 89.62 points(range,67.3 points to 100 points)at the last follow-up(P?0.05).There were no significant differences between range of motion postoperatively with tibal component alignment on coronal plane.Significances were found compared group-5°~5° with group 5°~7°.Within the range there were no significant differeces in post-HSS between groups.Parameter associated with better outcomes was tibial varus/valgus-5°~5° in our series.Furthermore,.there was no significant differences of ROM both between group varus and valgus and between within /without the target range.Conclusion:(1)Patients underwent UKA have been achieved better clinical outcomes when tibail varus/valgus were within ±5°.(2)Clinical outcomes would reduce sharply if tibial varus/valgus beyond 5°.