Summary

We performed a systematic review and meta-analysis to evaluate graft tensioning and knee flexion angles during MPFL reconstruction, finding that fixation at 30° knee flexion with pre-tensions up to 10N optimally restores patellofemoral mechanics

Abstract

Background

Patellofemoral instability is a common knee injury, accounting for approximately 3% of all knee injuries, with a high recurrence rate despite conservative and surgical treatments. The Medial Patellofemoral Ligament (MPFL) is a crucial stabilizer preventing lateral patellar displacement, often injured during dislocations. MPFL reconstruction is key to restoring patellar stability, yet there is no consensus on optimal graft tensioning and positioning, which are critical for achieving favorable outcomes.

Purpose

This study aims to systematically review the effect of graft pre-tensioning on patellofemoral pressure distribution and to identify the most effective knee flexion angle during graft fixation to restore patellofemoral kinematics and mechanics.

Methods

A systematic literature review was conducted on December 9, 2023, following PRISMA guidelines, with a search of PubMed, EMBASE, and Scopus databases for studies published from January 2000 onwards. The inclusion criteria were human cadaver studies analyzing patellofemoral pressure post-MPFL reconstruction. Data extraction focused on graft types, pre-tension levels, and patellofemoral pressure measurements at different knee flexion angles. The Quality Appraisal for Cadaveric Studies (QUACS) scale was used to assess methodological quality. Statistical analysis was performed using OpenMeta[Analyst], comparing medial and central patellofemoral pressures between native and reconstructed knees at various pre-tension levels and flexion angles.

Results

Thirteen studies met the inclusion criteria, with eight qualifying for quantitative analysis. A total of 75 cadaver knees were included. No significant differences in patellofemoral pressure were found between native and MPFL reconstructed knees at 30°, 60°, and 90° flexion across pre-tension levels of 2N, 10N, and above 10N. However, a trend towards higher medial patellofemoral pressure was observed with pre-tensions above 10N, particularly at 90° flexion. Most studies fixated the graft at 30° knee flexion, which reliably restored native patellofemoral pressure profiles.

Conclusion

This meta-analysis suggests that MPFL graft fixation at 30° knee flexion with pre-tensions up to 10N effectively restores native patellofemoral mechanics. However, higher pre-tensions tend to increase medial patellofemoral pressure, potentially leading to complications such as medial patellar subluxation and elevated risk of osteoarthritis. This underscores the importance of standardized graft tensioning and fixation techniques during MPFL reconstruction. Such standardization is not only essential for improving surgical outcomes but also for reducing the risk of postoperative complications, providing reassurance to the surgical community.
Implications: The findings underscore the importance of precise surgical techniques in MPFL reconstruction. Surgeons should aim for graft pre-tensions not exceeding 10N and fixate the graft at 30° of knee flexion to achieve optimal patellofemoral stability and function. This study also highlights the need for future research, which should focus on in vivo studies with larger sample sizes and standardized methodologies. Such research can further validate these recommendations and explore the biomechanical impacts of different surgical approaches, offering hope for continued improvement in MPFL reconstruction techniques.