Purpose: Medial patellofemoral ligament (MPFL) reconstruction combined with lateral retinacular release (LRR) has become a common treatment for recurrent patellar dislocation, but it has not been feasible to find a reliable and definitive figure to compare the change in soft tissue tension on both sides of the patella before and after LRR. The aim of this study was to verify the change in graft tension by means of a digital tensiometer. Methods: Fifty patients, aged 18-40 years, were included in this study, treated with MPFL reconstruction simplely and no other osteopathic surgery. After the graft had passed through the femoral tunnel, graft tension was measured by connecting a digital tensiometer, and the change in graft tension was analysed before and after LRR, together with pre- and post-operative knee function scores ( Lysholm score and kujala score) and radiographic angle (patellar congruence angle,PCA;PTA patellar tilt angle,PTA). RESULTS: All 50 patients (52 knees) underwent MPFL reconstruction combined with LRR, with statistically significant differences in graft tension from 35.61±4.25N to 24.00±4.23N before and after LRR as measured by a digital tensiometer, and Kujala score and Lysholm score from 51.40±14.39 to 92.23± 4.74 and from 48.17±9.52 to 91.88±5.07, respectively, and PCA and PTA from 16.51±5.97° to 2.34±3.37° and from 25.43±4.53° to 11.62±2.54°, respectively, with statistically significant differences.There were no significant post-operative complications, with the exception of three patients who experienced slight discomfort at the patellar end when the weather became colder.At a mean follow-up of 53 months, there were 7 (14%) complications and no postoperative redislocations were observed.94% of the patients were satisfied with the results of the operation. CONCLUSION: LRR is meaningful for patients with recurrent patellar dislocation and is effective in reducing tension on reconstruction grafts.

Purpose The optimal method for achieving proper graft tension during patellofemoral ligament reconstruction is a topic of debate. In the past, a digital tensiometer was used to simulate the knee structure, and a tension of approximately 2N was identified as suitable for restoring the patellofemoral track. However, it is unclear whether this tension level is sufficient during the actual surgery. The objective of this study was to verify the efficacy of graft tension using a digital tensiometer for medial patellofemoral ligament (MPFL) reconstruction and to conduct a mid-term follow-up. Methods The study enrolled 39 patients who had experienced recurrent patellar dislocation. Preoperative computed tomography scans and X-rays confirmed patellar instability, patellar tilt angle patellar congruence angle and the history of dislocation and patellar apprehension test. Knee function was evaluated using preoperative and postoperative Lysholm and Kujala scores. Results The study included 39 knees, comprising 22 females and 17 males, with an average age of 21.10 ± 7.26. The patients were followed up for at least 24 months through telephone or face-to-face questionnaires. All patients had a preoperative history of ≥2 patellar dislocations, none of which were surgically treated. During surgery, all patients underwent isolated MPFL reconstruction and lateral retinacula release. The mean Kujala and Lysholm scores were 91.28 ± 4.90 and 90.67 ± 5.15, respectively. The mean PTA and PCA were 11.5 ± 2.63 and 2.38 ± 3.58, respectively. The study found that a tension of approximately 27.39 ± 5.57N (14.3–33.5N) was required to restore the patellofemoral track in patients with recurrent patellar dislocation. No patients required reoperation during the follow-up period. Overall, 36 out of 39 patients (92.31%) reported no pain when completing daily activities at the last follow-up. Conclusion In conclusion, a tension level of approximately 27.39 ± 5.57N is necessary to restore normal patellofemoral relationships during clinical practice, which indicates that using a tension of 2N is too low. The use of a tensiometer during patellofemoral ligament reconstruction is a more accurate and reliable surgical procedure for treating recurrent patellar dislocation.