Controversies in Soft-tissue Anterior Cruciate Ligament

Increased stability has been reported with both autografts and allografts for anterior cruciate ligament (ACL) reconstruction. However, meta-analysis has shown significantly lower overall knee stability rates and more than double the abnormal stability rate with allografts. Some issues surrounding allograft sterilization (ie, risk of disease transmission) are unresolved, and cost is also a concern. Single-bundle ACL reconstruction can produce high stability rates when tunnels are properly placed, but there is evidence that double-bundle repair may offer greater rotatory stability. Cortical fixation has been associated with increased stability owing to the high stiffness of cortical bone. Anterior and posterior approaches are both recommended. The controversy related to single-bundle versus double-bundle ACL reconstruction remains unresolved. Allograft Versus Autograft An ideal graft for anterior cruciate ligament (ACL) reconstruction would reproduce the histologic and biomechanical characteristics of the native ligament, would incorporate fully and quickly within bone tunnels, would have no risk of immunerejection or of disease transmission, would minimize donor-site morbidity, would be of sufficient length and diameter, and would be inexpensive and readily available. Unfortunately, the ideal graft does not yet exist. The two primary options, autograft and allograft, each have advantages and shortcomings (Table 1). Several types of autograft are commonly used for ACL reconstruction, including four-strand hamstring (4HS),6,7 bone–patellar tendon–bone (BPTB),6,8 and quadriceps tendon.9 Common types of allografts used include BPTB,10 Achilles tendon,11 and tibialis anterior or posterior tendon.12 There are advantages and disadvantages for each type of autograft and allograft, and these must be considered during graft selection. Donor Site Morbidity Donor site morbidity is not a factor with allograft, and it has been minimal with autograft hamstring. The only reported morbidities with the latter are mild knee flexion weakness and mild internal rotation weakness, both of which are seen only at relatively high knee flexion angles.13-18 No clinical performance deficit associated with these findings has been reported. The now wellChadwick C. Prodromos, MD