Effect of Hamstring Harvest in the Setting of ACL and MCL Concurrent Injury
Authors: Nelson Trevor , Kremen Thomas J. , Polakof Landon S. , Rajaee Sean , Metzger Melodie 
Published: July 2017

Objectives:

Hamstrings autograft is commonly used to reconstruct an isolated ACL tear, however, there is evidence to suggest that the tendons harvested may contribute to medial knee stability. We tested the hypothesis that the gracilis (G) and semitendinosus (St) tendons significantly contribute to sagittal, coronal and/or rotational knee stability in the setting of an ACL reconstruction with concurrent partial MCL injury.

Methods:

Twelve human cadaveric knees were subject to a static anteriorly-directed force and moments in varus, valgus, internal and external rotation at the tibia while the femur was held stationary in order to quantify laxity at 0, 30, 60, and 90 degrees of flexion. Testing was performed on each leg in following ligament conditions: (1) ACL-intact/MCL-intact, (2) ACL-deficient/MCL-intact, (3) ACL-deficient/ MCL-partial injury, and (4) ACL-reconstruction, MCL-partial injury (chart 1). To quantify the effect of muscle loads the quadriceps, semimembranosus, biceps femoris, sartorius (Sr), St and G muscles were sutured and physiologically loaded. Quadriceps were loaded to 200 N and semimembranosus and biceps femoris were loaded to 40 N and held constant for all test conditions. The G and St were attached to a 40N load which was removed during test conditions in order to simulate hamstring graft harvest. Similarly, a Sr load of 20N was added and removed to determine its role in contributing to knee stability. For each ligament condition, the response to loading was determined with either (A) St/G muscles loaded and Sr unloaded; (B) St/G loaded, Sr loaded; (C) St/G unloaded, Sr unloaded; and (D) St/G unloaded, Sr loaded (chart 1). Three-dimensional positional data of the tibia relative to the femur was recorded to determine displacement and rotation across the knee.

Results:

ACL reconstruction restored anterior stability regardless of whether or not G/St and/or Sr loads were applied. A partial tear of the MCL significantly increased external rotation when the G/St were unloaded and approached significance (p<0.06) when the G/St load was applied. When an internal rotation load was applied all conditions tested were significantly less stable than intact. No differences were demonstrated during varus loading. When specimens were loaded with a valgus moment there was no significant increase in motion after ACL transection. However, when a partial MCL tear was added to the ACL injury there was a significant increase in valgus rotation regardless of whether or not the G/St and Sr muscles forces were applied. ACL reconstruction only restored valgus stability when the G/St muscles were loaded, Figure 1. However, there was no difference in valgus stability when comparing testing conditions 4A (G/St loaded) and 4D (G/St unloaded, Sr loaded, Figure 1).

Conclusion:

Absence of load on the G and St, as would be the case when harvested for hamstrings autograft, did not lead to increased anterior translation of the tibia in ACL reconstructed knees with partial MCL injury. Although the absence of an applied G and St muscle force did lead to increased valgus rotation after ACL reconstruction, there was no difference between the G/St loaded state compared to the G/St unloaded state once a Sr load was applied. This may have clinical implications for surgeons with regard to post-operative bracing and ACL reconstruction graft recommendations. [Figure: see text]