Synthetic versus autologous reconstruction (Syn-VAR) of the medial patellofemoral ligament: a study protocol for a randomised controlled trial

No Difference in Pullout Strength Between a Bio-inductive Implant and a Semitendinosus Tendon Graft in a Biomechanical Study of Medial Patellofemoral Ligament Repair Augmentation

Purpose

To compare the pullout strength of a bio-inductive implant (BI) used to augment a medial patellofemoral ligament (MPFL) repair with the pullout strength of semitendinosus graft in a biomechanical cadaveric model.

Methods

Six matched pairs of cadavers (12 knees) were used in the biomechanical testing comparing semitendinosus tendon (Semi-T) versus a BI. The Semi-T was harvested from 1 of the matched pairs. A standard double-bundle technique using 2 sockets in the upper two-thirds of the patella 15 mm apart was performed. After docking of the graft into the patella, the patella was dissected free of soft tissues and potted into a fixture to allow mechanical pull parallel to the transverse axis of the patella. The construct was pulled to failure.

Results

There was no statistically significant difference in pullout strength (P = .77) between the BI group (249.3 ± 36.3 N) and Semi-T group (235.0 ± 113.6 N) double-bundle constructs. In the Semi-T group, 50% of the specimens (3 of 6 knees) failed via anchor pullout and a fourth specimen failed at the suture-anchor interface (16.7%), whereas in the BI group, 16.7% of the specimens (1 of 6 knees) failed by anchor pullout. Although the Semi-T group (49.5 ± 14.1 N/mm) showed significantly greater stiffness than the BI group (13.8 ± 0.6 N/mm, P < .01), pullout strength in the Semi-T group was highly variable: 50% of the specimens (3 of 6 knees) with semitendinosus constructs failed at 5 mm of displacement or less via graft or anchor pullout. Maximum load, displacement at failure, stiffness, and load at 5 mm were compared between the augmented and non-augmented control specimens using a 2-tailed non-equal variance Student t test. For all comparisons, P < .05 was considered to indicate a statistically significant difference.

Conclusions

In this biomechanical study, augmentation of an MPFL reconstruction using a common double-bundle technique with a BI had the same pullout strength as a semitendinosus graft using the same technique in cadaveric knees.

Clinical Relevance

MPFL repair after a patellar dislocation may be inadequate to restore the strength of the native MPFL and prevent recurrent patellar instability. Recurrent instability of the patella can result in progressive injury to the soft tissue and articular cartilage of the patella and femur. It is important to study the techniques used for MPFL repair to continually improve patient outcomes. Further testing of these additional techniques and clinical studies are needed to evaluate the implants used to augment MPFL repairs.

Synthetic graft for medial patellofemoral ligament reconstruction: a systematic review

Background

This systematic review investigates the role of synthetic graft for primary medial patellofemoral ligament (MPFL) reconstruction in patients with recurrent patellofemoral instability, focusing on clinical scores and the rate of complications.

Methods

This systematic review was conducted according to the PRISMA statement. The main online databases were accessed in January 2022 without time constraints. All clinical studies investigating the use of synthetic grafts for MPFL reconstruction were accessed. Revision settings were not considered. Only articles reporting data on patients with recurrent patellofemoral instability were eligible. Studies regarding congenital or acute patellofemoral dislocation were excluded. Only studies performing a follow-up longer than 24 months were considered.

Results

Data on 199 patients [mean age 22.3 (range 19.0–28.0) years] were collected. The mean follow-up was 60.5 (39.0–142.8) months. All the scores of interest improved at last follow-up: Kujala (+ 24.8; P = 0.0002), Lysholm (+ 42.0; P = 0.02), Tegner (+ 1.2; P = 0.03), IKDC (+ 20.9; P = 0.02). Post-operatively, a positive apprehension test was detected in 6.1% (7/115) of patients, and a sensation of instability was reported by 1.5% (3/199) of patients. The rate of re-dislocations was 2.5% (5 of 199 patients), and revision procedures were performed in less than 1% (1 of 199) of patients.

Conclusion

Synthetic graft may be reliable and feasible for primary MPFL reconstruction in patients with recurrent patellofemoral instability.

The Effect of Patellar Tendon Release on the Characteristics of Patellofemoral Joint Squat Movement: A Simulation Analysis

Objectives: This paper studies the patellar tendon release’s effect on the movement characteristics of the artificial patellofemoral joint squat to provide reference data for knee joint surgery. Methods: Firstly, the dynamic finite element model of the human knee joint under squatting was established. Secondly, in the above no-release models, the release of 30% of the attachment area at the upper end, the lower end, or both ends of the patellar tendon were conducted, respectively. Then the simulations of all above four models were conducted. Finally, the results of the simulation were compared and analyzed. Results: The simulation results show that, after releasing the patellar tendon (compared with the no-release simulation’s results), the relative flexion, medial-lateral rotation, medial-lateral tilt, and superior-inferior shift of the patella relative to the femur increased; the medial-lateral shift and anterior-posterior shift of the patella relative to the femur decreased. Conclusion: In this paper, the maximum flexion angle of the patella increased after the patellar tendon being released (compared with the no-release model), which indicated that the mobility of knee joint was improved after the patellar tendon release. The simulation data in this paper can provide technical reference for total knee arthroplasty.