Long-Term Examination of Bone Mineral Density in the Calcanei After Anterior Cruciate Ligament Reconstruction in Adolescents and Matched Adult Controls

Abstract

The aims were to evaluate the results 10 to 20 years after anterior cruciate ligament (ACL) reconstruction performed in adolescents in terms of bone mineral density (BMD) in the calcanei using the dual-energy x-ray absorptiometry (DXA) technique, activity level, and quality of life. A case-control study of adolescents who underwent ACL reconstruction between 1992 and 2002 was performed. The inclusion criterion was a unilateral ACL injury. The exclusion criteria were bilateral ACL injury, contralateral ACL reconstruction, posterior cruciate ligament injury, and previous or present fractures of either lower extremity. The BMD was measured in both calcanei using the DXA technique and compared with a control group of adult ACL-reconstructed patients and with a DXA reference database. The age of the control group was similar to that of the patient group at the time of BMD assessment, performed 60 months after reconstruction. Activity was measured with the Tegner activity scale. The EQ-5D was used to evaluate quality of life. Thirty-two adolescents (11 boys and 21 girls), aged 12 to 16 years, with a symptomatic unilateral ACL rupture, underwent reconstruction at near skeletally mature age. Of these patients, 29 (91%) took part in the follow-up examination. The BMD values for the male patients were lower on the injured and non-injured sides (-15.2% [P = .02] and -11.8% [P = .05], respectively) compared with the control group. The values for the female patients were -0.8% (P = .84) and -2.2% (P = .69), respectively. Correspondingly, the BMD values for the male patients were lower on the injured and non-injured sides (-8.2% and -4.9%, respectively) compared with the male reference database. The BMD values for the female patients were higher on the injured and non-injured sides (4.1% and 4.3%, respectively) compared with the female reference database. In the control group, female patients had a significantly lower value for the Tegner activity scale preoperatively (median, 2.0; range, 0 to 5) than the female patients in the study group (median, 3.0; range, 2 to 8) (P = .006). In the study group, the Tegner activity scale at follow-up showed a significant correlation with the BMD on the injured side for male patients (ρ = 0.67, P = .03) but not on the non-injured side (ρ = 0.50, P = .14). In the control group, the Tegner activity scale at follow-up showed a significant correlation with the BMD on the non-injured side for female patients (ρ = 0.61, P = .03) but not on the injured side (ρ = 0.34, P = .25). The Tegner activity scale and EQ-5D showed no significant differences between the study groups. In the long-term, the BMD in the calcanei of patients who were adolescents at the time of ACL reconstruction differed from that of a control group and a reference database. This study indicates that boys with an ACL injury and subsequent ACL reconstruction run a subsequent risk of a significantly lower BMD in their calcanei as adults and, consequently, an increased future fracture risk. Level III, case-control study.