Femoral Tunnel Drilling Method: Revision Risk After Anterior Cruciate Ligament Reconstruction

OBJECTIVES: The femoral tunnel in anterior cruciate ligament reconstruction (ACLR) can be created by the transtibial (TT) or tibial-independent (TI) methods. An anatomically located femoral tunnel can be more consistently achieved by TI methods, which include the medial portal (MP) and lateral (outside-in, retrodrill) techniques. Non-anatomic graft placement in ACLR may result in postoperative instability and meniscal or chondral pathology. An anatomically located graft may be subjected to higher postoperative physiologic forces than one placed non-anatomically. The purpose of this study was to examine isolated primary ACLR and determine the risk of aseptic revision based on femoral tunnel drilling method. METHODS: A retrospective cohort study was conducted using an integrated U.S. healthcare system’s ACLR Registry to identify primary isolated unilateral cases from 2009 to 2014. Bilateral, double-bundle and multi-ligament reconstructions were excluded. Patients were divided into two groups based on femoral tunnel drilling method, TT or TI. Drilling method was evaluated as a risk factor for aseptic revision, with adjustment for age, sex, body mass index (BMI), race, and graft type using multivariable Cox proportional-hazards regression models. RESULTS: 19,022 primary ACLR patients were included, of whom 6,991 (36.8%) were younger than 22 years old, 11,772 (61.9%) were male, 7,632 (40.1%) had a BMI < 25 kg/m(2), 8,894 (46.8%) were White, and 7,403 (38.9%) received an allograft. There were 12,336 (64.9%) ACLRs performed using TI techniques (MP n=10,149, lateral n=2,187) and 6,686 (35.1%) using the TT method. Usage of TI approaches increased from 34% of all ACLR in 2009 to 84% in 2014. The cumulative reoperation probability at 5-year follow-up was lower in the TI group, 7.5% (95% CI 6.6-8.4), compared to the TT group, 8.2% (95% CI 7.4-9.1). After adjusting for the covariates, the cumulative failure probability at 5-year follow-up was higher in the TI group, 6.3% (95% CI 5.6-7.2), compared to the TT group, 5.0% (95% CI 4.3-5.7). [Figure 1] After adjusting for the covariates, the TI group had a higher risk for aseptic revision than the TT group (HR=1.4. 95% CI=1.1-1.7). CONCLUSION: In the largest known study of its type examining femoral tunnel drilling method for primary ACLR, after adjusting for age, sex, BMI, race and graft type, TI techniques were found to have a 1.4 times higher risk of revision than the TT method. Surgeons should be aware that ACLR grafts placed more anatomically by TI methods have a higher risk of revision, possibly due to higher postoperative physiologic graft forces experienced.