Quadriceps And Hamstring Muscle Volume Following Anterior Cruciate Ligament Reconstruction Using An Allograft

Impaired muscle function of the quadriceps and hamstring muscles is commonly observed following anterior cruciate ligament reconstruction (ACLR), which makes these muscles primary targets during post-ACLR rehabilitation. The changes in quadriceps and hamstrings muscle morphology, however, have not been investigated following ACLR using an allograft in which the donor site morbidity accompanied with autografts is avoided. PURPOSE: To examine muscle volume of the quadriceps and hamstring muscles in females following ACLR using an allograft. METHODS: Seven females (mean age: 25.1 ± 2.6 years) with unilateral ACLR using an allograft participated. The average time from surgery was 30.3 ± 18.7 months. All subjects had completed rehabilitation and had been cleared to return to full activity by their orthopaedic surgeons. Magnetic resonance images were used to quantify volumes of the quadriceps, hamstrings, and subcutaneous fat for the distal two-thirds of both thighs, starting from the base of the patella. Differences between the injured and uninjured limbs were examined using Wilcoxon signed-rank tests. RESULTS: The overall quadriceps muscle volume of the reconstructed limb was 7.3 ± 6.4 % (p = 0.043) smaller when compared to the uninjured limb. The lower quadriceps volume of the reconstructed limb was a result of a smaller volume of the vastus lateralis (smaller by 7.9 ± 8.2 %, p = 0.043) and vastus medialis (smaller by 10.3 ± 9.1 %, p = 0.043) when compared to the uninjured limb. No differences between the two limbs were observed for the entire or individual hamstring muscles. While subcutaneous fat volume of the reconstructed limb was 2.7 ± 3.6 % greater compared to the uninjured limb, this difference was not statically significant (p = 0.063). CONCLUSION: Females who have undergone ACLR using an allograft do not demonstrate a change in the hamstring muscle volume as previously reported in individuals with ACLR using a semitendinosus-gracilis autograft. However, our findings of selective atrophy in the vastus lateralis and vastus medialis suggest that factors other than donor tissue integrity (e.g., unloading, muscle inhibition, etc.) may be responsible for the impaired quadriceps muscle function following ACLR using an allograft.