Summary

In a cadaveric biomechanics study, we found that a `modified LaPrade` posterolateral corner reconstruction technique using a single semitendinosus autograft restored varus and external rotation laxity similarly to the `original LaPrade` anatomic technique.

Abstract

Background

A number of different techniques to restore knee stability after posterolateral corner (PLC) injury have been described. The anatomic PLC reconstruction originally described by LaPrade used two separate allografts, focusing on the reconstruction of the fibular collateral ligament (FCL), popliteofibular ligament (PFL), and the popliteus tendon (PT), to adequately control coronal and rotational laxity. Access to allograft tissue continues to be a significant limitation of this technique which lead to the development of a modified anatomic approach by Wood et al. utilizing a single autologous semitendinosus graft fixed on the tibia with an adjustable loop to enable differential tensioning of the FCL and PFL/Pt components.

Purpose

The objective of this study was to compare the ‘modified LaPrade’ technique to the ‘original LaPrade’ anatomic reconstruction in terms of varus and external rotation laxity.

Hypothesis

Both techniques will restore varus and external rotation laxity following a simulated complete PLC injury.

Study Design: Controlled laboratory study

Methods

Eight matched-paired fresh-frozen cadaveric mid-femur to mid-tibia specimens (n=16, 8 in either surgical reconstruction group) were tested using an AMTI`s VIVO™ 6 degrees of freedom joint motion simulator. The maximum achievable varus and external tibial rotation laxity of the knee were measured while applying 10Nm varus and 5Nm external rotatory torques, at 0°, 30°, 60°, and 90° of flexion. These measurements were tested under three conditions: (1) intact FCL, PT, and PFL, (2) complete transection of the FCL, PT, and PFL, (3) performed after PLC reconstruction. Reconstruction was performed using either the ‘original LaPrade’ or the ‘modified LaPrade’ anatomic reconstruction technique.

Results

Following PLC reconstruction, varus laxity was restored with no statistically significant differences from the intact condition following both reconstruction techniques. While yielding similar outcomes for external rotation in extension, were observed a statistically significant reduction in the external rotation limit (with respect to the intact joint) 4.1°±6.3° (p = 0.036) and 5.1°±6.6° (p = 0.016) at 60° and 90° of flexion, respectively. Statistically, there was no difference between the outcomes of the two procedures (p = 0.112). No significant impact on the kinematics during neutral to flexion was observed and no statistically significant differences were observed between reconstructions (p = 0.112).

Conclusion

Both PLC reconstructions restored the native varus and external tibial rotation laxity to the knee. Care should be taken when tensioning in the ‘modified’ technique that the tibia is in a neutral position to avoid over constraining the knee. The `modified` technique is useful in situations where allografts are not available, restricted because of cost, and patients who decline the use of allograft tissue.