Summary

This study is reports on the biomechanical effect of varus and valgus alignments in medial meniscus deficient knees. A novel biomechanical setup was developed to mechanically simulate the valgus and varus conditions without the need of a tibial osteotomy. This study shows that already 1° and 2° of malalignment has a high impact on peak pressure in meniscus deficient knees.

Abstract

Background

Degenerative medial meniscus tears and subsequent partial meniscus resection compromise meniscus function and lead to an overload of the medial compartment. In addition, lower limb alignment plays a key role in load distribution between the medial and lateral knee compartment and varus alignment is a potential risk factor for medial osteoarthritis. The purpose of this biomechanical study was to investigate the effect of valgus and varus alignment on peak pressure and contact area in knees with concomitant horizontal medial meniscus tears and subsequent leaflet resection. It was hypothesized that varus alignment in combination with meniscus loss leads to the highest peak pressure within the medial compartment.

Material And Methods

Six fresh-frozen human cadaveric knees were axially loaded with a 1000 N compressive load in full extension and at 0°, 1° and 2° varus and valgus alignment, respectively. Tibiofemoral peak contact pressure and contact area of the medial and lateral compartment were determined using pressure sensitive foils (K-Scan 4000, Tekscan) in each of four different meniscal conditions: intact, 15mm horizontal tear of the posterior horn, inferior leaflet resection, and resection of both leaflets. The statistical analysis was based upon a two-factor analysis of variance (ANOVA) with repeated measures. Statistical significance was set at a value of p<0.05.

Results

The effect of alignment on peak pressure (normalized to the neutral axis) within the medial compartment in case of intact meniscus was measured as follows: mean increase was 18.5% in 1° and 37.4% in 2° varus, whereas 1° and 2° valgus lead to peak pressure decrease of 8.7% and 23.1%. Peak pressure change between intact meniscus and resection status within the medial compartment were higher in varus aligned knees (0.21 MPa in 2° valgus, 0.59 MPa in 0°, 0.74 MPa in 2° varus). Contact area was significantly reduced after partial meniscus resection in neutral axis (intact 553.5 ± 87.6 mm2 vs. both leaflet resection 323.3 ± 84.2 mm2, p<0.001). This finding was consistent in any alignment.

Conclusion

Both, partial medial meniscus resection and varus alignment lead to an increase in medial compartment peak pressure. Valgus alignment prevents medial overload by decreasing contact pressure even after partial meniscus resection. A present meniscus tear does not influence peak pressure and contact area even in varus alignment.