Summary

Bone marrow aspiration concentrate did not improve graft maturation or clinical outcomes in ACL reconstruction over five years but resulted in longer operative times compared to controls.

Abstract

Introduction

Bone marrow aspiration concentrate (BMAC) has emerged as a biological adjuvant to accelerate graft-maturation and rehabilitation in anterior cruciate ligament reconstructions (ACL-R). Despite its potential, there is a scarcity of clinical trials assessing BMAC’s effectiveness in ACL-R. This study aims to assess the clinical impact of BMAC five years post-ACL-R. The hypothesis is that BMAC does not significantly enhance graft radiological maturation or clinical outcomes during short and mid-term follow-ups.

Methods

A cohort study was conducted including healthy patients aged 18-40 years undergoing primary ACL-R with an autologous five-strand hamstring graft. Exclusion criteria encompassed multiligamentary knee injuries, revision surgeries, corticosteroid use within 0.5 years prior to surgery, and other intraarticular injuries requiring surgical intervention that might alter rehabilitation protocols. Twenty-seven patients were included and divided into Intervention (BMAC, n=14) and Control (n=13) groups, which were comparable for demographic variables and graft diameter. BMAC was harvested from the intercondylar femoral notch during the same procedure. Comparative analysis focused on operative times, graft maturation (via magnetic resonance at 0.5 years), and clinical outcomes (isokinetic tests at 0.5 years from surgery; KOOS, Lysholm, Tegner, and IKDC at 0, 0.5, 1, 2, and 5 years of follow-up; and the incidence of graft and contralateral ACL ruptures at 5 years). Group size was determined through a priori power analysis (>80% power, p=0.005) considering an approximate difference of 10 points (±9) in the Lysholm score (minimal clinically important difference), resulting in a minimum of 13 patients per group. Statistical analysis included the Mann–Whitney U test for median comparisons, and Fisher’s exact test for categorical data.

Results

The intervention group showed significantly longer operative times (p<0.001). At 6 months, ligamentization assessed by SNQ showed median values of 12.9 (5.63-32.6) in the intervention group and 17.4 (4.84-29.0) in the control group (p=0.401). Femoral tunnel integration median values were 15.3 (9.56-40.4) and 17.6 (8.48-28.1) respectively (p=0.497), and tibial tunnel integration values were 9.7 (2.18-21.4) and 11.8 (3.43-29.5) respectively (p=0.120). Tunnel integration assessed by the Ge Score showed no significant differences in grades between groups, with 71.4% of the intervention group and 69.2% of the control group achieving Grade II femoral tunnel integration (p=0.638), and 78.6% of the intervention group and 76.9% of the control group achieving Grade II tibial tunnel integration (p=0.999). There were no significant differences in isokinetic strength between the intervention and the control group for both quadriceps (36% versus 32%, p=0.34, respectively) and hamstring (15% versus 14%, p=0.875, respectively) muscle groups. KOOS scores at 0, 0.5, 1, 2, and 5 years were 47.8, 82.2, 94.1, 83.6, and 83.8 for the intervention group and 48.0, 80.8, 92.6, 87.9, and 82.6 for the control group. IKDC scores were 50.7, 77.0, 92.8, 84.8, and 92.3 for the intervention group and 48.8, 75.9, 90.3, 90.3, and 86.5 for the control group. Lysholm scores were 60.6, 94.5, 99.8, 95.1, and 94.6 for the intervention group and 57.5, 92.3, 98.2, 96.8, and 87.3 for the control group. No significant differences were observed in patient-reported outcomes measures (PROMs) between groups at any assessed time point. No reconstruction re-tears were noted, and there were 2 contralateral ACL ruptures in each group (p=0.999).

Conclusion

In this study, BMAC augmentation in 5-strand hamstring autograft ACL-R did not demonstrate improvements in graft maturation, isokinetic test results, or PROMs up to 5-years after surgery. Moreover, there was no significant difference in the incidence of re-tears or contralateral ACL ruptures compared to a control group; however, BMAC application did lead to significantly longer operative time.