High accuracy of the osteotomy angle can be achieved without the use of calibrated guides when performing anteromedialisation tibial tubercle osteotomy

Objectives Tibial tubercle osteotomy (TTO) is a frequently performed procedure for the treatment of patellar instability and allows for chondral defect unloading when performed in conjunction with cartilage repair. Accurate intraoperative execution of the osteotomy is of utmost importance to achieve the desired outcome. The purpose of this study is to validate the intraoperative accuracy of the osteotomy angle of TTO. Methods Between January 2007 and May 2017, a total of 212 patients underwent TTO; however, only patients with postoperative axial (magnetic resonance) imaging were eligible for inclusion. Thus, 124 patients (126 knees) (58.5%) were evaluated in this study. The osteotomy angle was assessed by two independent reviewers (fellowship trained radiologist and orthopaedic surgeon) using MRI and compared with preoperative planning. Results Patients were on average 32.89 years (range 15–56, SD 9.7) of age at the time of surgery with an equal gender contribution (50% women vs 50% men). Postoperative MRI was conducted at 12.53 months (range 2–91 months, SD 12.2) follow-up. Postoperative MRI-measured osteotomy angles averaged 104.1% of planned angles and showed a high intraclass correlation coefficient of 0.87. The accuracy of the osteotomy cut did not vary with the planned steepness of the cut (p=0.984). Conclusion This study demonstrates that the high accuracy of the osteotomy angle can be achieved without the use of calibrated guides. Good exposure and visualisation of the TT intraoperatively are paramount for the precision of anteromedialisation TT osteotomy using the Fulkerson’s technique. Level of evidence Level IV, retrospective case series IRB protocol number 2017P001677