Review Question - QID 219513

This patient has sustained an ACL re-rupture after undergoing ACL reconstruction (ACL-R) with allograft tissue, which is made evident by his physical exam. In athletic patients aged 10-19 years old, the odds of graft re-rupture are 4.3 times higher when allograft is utilized (Answer 4).

The optimal graft for adolescent ACL-R is a highly debated and controversial topic. However, a multitude of factors have been implicated in the increased failure rates of allograft ACL-R in adolescent athletes. For instance, adolescents have higher activity levels in comparison to older adults which leads to increased strain and stress across the graft material. Also, previous histopathologic analysis completed by Malinin et al. of allograft tissue noted that the attachment of the graft to the bone tunnel wall may take 2 years while complete remodeling may take up to 3 years.

In a cohort study by Maletis et al., the risk of aseptic revision ACL-R was compared between bone-patellar tendon-bone (BPTB) autografts and BPTB allografts. The study included 5586 patients, and the estimated cumulative revision rate at 2 years was 4.1% for allografts and 1.7% for autografts. BPTB allografts showed a significantly higher adjusted risk of revision compared to autografts (Hazard ratio, 4.54). This risk persisted across all allograft processing methods and age groups.

In a randomized controlled trial by Bottoni et al., the long-term outcomes of ACL-R using either hamstring autografts or tibialis posterior allografts were evaluated. At a minimum follow-up of 10 years, 96 patients (97 knees) were evaluated, revealing a higher rate of failure requiring revision reconstruction in the allograft group (26.5%) compared to the autograft group (8.3%). However, among patients with intact grafts, there was no significant difference in functional scores between the two groups. The study concludes that while over 80% of grafts maintained stability after 10 years in young athletes, those who received allografts experienced a revision rate over three times higher than those with autografts.

A case-control study conducted by Engelman et al. identified graft type and postoperative knee laxity in adolescent patients' status post ACL-R. They found these variables to be significant predictors of graft survival, with the allograft group exhibiting a higher hazard of failure compared to the autograft group (4.4 times greater). Autograft failure risk remained relatively constant over time, while allograft failure risk continued to increase beyond 24 months post-surgery.

Incorrect Answers:
Answer 1: Failure to adhere to postoperative protocols can increase an individual's risk of ACL-R failure. However, this patient is presenting 2 years after his index procedure indicating that he successfully rehabilitated his reconstruction and was subsequently cleared to return to activities.
Answer 2: Anterior femoral tunnel placement can predispose a patient to graft impingement and subsequent failure, but in an adolescent population, allograft utilization is a more likely cause of failure.
Answer 3: Quadriceps tendon autograft is associated with lower rates of failure in comparison to allograft tissue in adolescent patients undergoing ACL-R. Also, on physical exam there is no evidence of surgical incisions indicating that autograft tissue was harvested.
Answer 5: Posterior wall blowout is an intra-operative complication that results from failure to leave greater than 2mm of the posterior wall while drilling the femoral tunnel. This usually necessitates utilizing suspensory fixation to secure the graft. However, this is less likely to lead to graft re-rupture in comparison to allograft utilization in an adolescent.