All-inside ACL Reconstruction Offers No Advantage in Clinical Outcomes, Graft Healing, or Tunnel Widening Compared With the Complete Tibial Tunnel Technique: A Prospective Randomized Trial

BACKGROUND: The all-inside ACL reconstruction technique is seeing wider use and may offer some clinical advantages over the traditional complete tibial tunnel technique, but to date, no RCT of which we are aware has directly compared these techniques using identical adjustable suspensory fixation devices. QUESTIONS/PURPOSES: In this RCT, we compared the all-inside technique to the complete tibial tunnel technique, using the same adjustable suspensory fixation device in ACL reconstruction, and asked: (1) Is there a difference in functional outcome measures including instrumented knee laxity testing, International Knee Documentation Committee (IKDC) subjective knee score, and Marx activity scale? (2) Is there a difference in graft healing and integration as measured by graft signal-to-noise quotient (SNQ) on MRI at 1 year? (3) Is there a difference in tibial tunnel morphology and volume as measured by CT performed at 1 day and 1 year postoperatively? METHODS: Between November 2022 and August 2023, a total of 71 patients who met the inclusion criteria were prospectively allocated via computer-generated randomization to undergo ACL reconstruction via either the all-inside technique or complete tibial tunnel technique using the same adjustable suspensory fixation devices. The groups did not differ in terms of age, gender, or BMI (all-inside group: 35 patients with a mean ± SD age of 28 ± 6 years; complete tibial tunnel group: 36 patients with a mean ± SD age of 27 ± 7 years). Clinical outcome measures included knee laxity as measured by the KT-1000 arthrometer, the IKDC subjective knee score, and the Marx activity scale, all measured preoperatively and at 1 year. The follow-up proportion at 1 year was 87.5% (35 of 40) in the all-inside group and 90% (36 of 40) in the complete tibial tunnel group. At 1 year postoperatively, graft healing and integration were assessed on MRI using graft SNQ. To evaluate tibial tunnel morphology and time-related volume changes, CT was performed at 1 day and 1 year postoperatively. RESULTS: We found no differences in patient-reported or objective outcomes at 1 year between the all-inside and complete tibial tunnel groups. The mean ± SD IKDC score was 86 ± 11 versus 88 ± 14, respectively (mean difference -2 [95% confidence interval (CI) -7 to 4]; p = 0.46). Similarly, anterior tibial translation was 2 ± 1 mm in the all-inside group versus 1 ± 1 mm in the complete tibial tunnel group (mean difference 1 mm [95% CI -1 to 1]; p = 0.15). On MRI, the SNQ values were not different between groups in the intrafemoral tunnel graft (6 ± 4 versus 5 ± 4, mean difference 1 [95% CI -2 to 2]; p = 0.32), intraarticular graft (5 ± 4 versus 6 ± 3, mean difference -1 [95% CI -2 to 1]; p = 0.13), or intratibial tunnel graft (3 ± 3 versus 4 ± 3, mean difference -1 [95% CI -1 to 1]; p = 0.39). On CT, graft tunnel volume increased from postoperative Day 1 to 1 year in both groups (all-inside 1141 ± 173 mm 3 to 1338 ± 196 mm 3 ; complete tibial tunnel 1089 ± 141 mm 3 to 1291 ± 188 mm 3 ; p < 0.001 within groups), with no difference in the degree of increase between groups (mean difference -4 mm 3 [95% CI -122 to 113]; p = 0.14). The loop tunnel volume decreased in both groups over time, but initial loop tunnel volume was substantially higher in the complete tibial tunnel group (1953 ± 127 mm 3 ) compared with the all-inside group (353 ± 35 mm 3 ; p < 0.001). At 1 year, loop tunnel volumes were similar (102 ± 36 mm 3 versus 97 ± 25 mm 3 ; p = 0.41). The percentage of the loop tunnel filled with bone was higher in the complete tibial tunnel group (94% ± 5%) than in the all-inside group (68% ± 4%, mean difference -26% [95% CI -28% to 23%]; p < 0.001). Graft tunnel widening was no different between the groups (16% ± 3% versus 15% ± 3%, mean difference 1% [95% CI -1% to 3%]; p = 0.21). CONCLUSION: In this randomized trial, we found no advantages in clinical outcomes, graft healing, or tunnel widening associated with the use of the all-inside technique compared with the complete tibial tunnel technique in ACL reconstruction. Although the all-inside technique is often preferred for its perceived bone-preserving benefit, our findings showed that the loop tunnel in the complete tibial tunnel group was nearly fully filled with bone by the first postoperative year-suggesting that concerns about "dead space" in this technique may be unfounded. That being so, we do not recommend the routine use of the all-inside technique, especially considering its requirement for specialized instruments and potentially higher cost. LEVEL OF EVIDENCE: Level I, therapeutic study.