Clinical and surgical outcomes of medial patellofemoral ligament reconstruction in patients with lateral patellar instability

Objective: The primary aim of this study is to evaluate the mid-term clinical and radiological outcomes of patients who underwent isolated Medial Patellofemoral Ligament (MPFL) reconstruction using gracilis autograft for recurrent patellofemoral instability. The secondary aim of the study is to investigate the determinative effect of postoperative quadriceps muscle weakness and accompanying anatomical risk factors (specifically increased TT-TG distance and the degree of trochlear dysplasia) on patients' functional scores. Material and Methods: This retrospective observational study was conducted at Erzincan Binali Yıldırım University Faculty of Medicine Hospital between January 2021 and December 2024. The study included 15 patients (9 right, 6 left knees) who were operated on with a diagnosis of patellar dislocation and had regular follow-ups. As the surgical technique, a gracilis tendon autograft was used in all patients; the graft was fixed to the patella with two suture anchors and to the femur with a bioabsorbable interference screw after creating a tunnel at the Schöttle point identified under fluoroscopic guidance. For functional assessment, patients' preoperative and postoperative Lysholm Knee Score, Kujala Patellofemoral Score, and Tegner Activity Scale data were compared. Additionally, postoperative quadriceps muscle strength was evaluated via manual testing, and patients were grouped as having "weakness present" or "weakness absent." Radiological analyses included the measurement of the Insall-Salvati index and trochlear dysplasia according to the Dejour classification on direct radiographs, and the Tibial Tubercle-Trochlear Groove (TT-TG) distance on CT/MRI sections. Statistical analysis of the data was performed using SPSS software. Results: The mean age of the study group was 31.60 ± 8.53 years, and the mean follow-up period was 27.27 ± 16.24 months. Radiologically, 53.3% of the patients had Type A and 26.7% had Type B trochlear dysplasia. In the postoperative period, a statistically significant increase was recorded in the Lysholm score compared to the preoperative period (from 53.47 to 69.80; p=0.045). Although clinical improvement was observed in Kujala and Tegner scores, statistical significance was not reached. Postoperative quadriceps weakness was detected in 53.3% (n=8) of the patients. Comparative analysis revealed that the Lysholm and Kujala scores of patients without quadriceps weakness were statistically significantly higher (p<0.01) compared to the group with weakness. Regarding radiological parameters, no negative correlation was found between increased TT-TG distance and postoperative functional scores (Lysholm and Kujala). Conclusion: Isolated MPFL reconstruction is a reliable method for preventing patellar instability and providing knee stability. However, the data from our study indicate that "mechanical" stability provided by surgery does not guarantee high "functional" success on its own. The most critical determinant of clinical success and patient satisfaction is the recovery of postoperative quadriceps muscle strength through rehabilitation rather than anatomical factors. Therefore, surgical treatment must be supported by an effective physical therapy program.