Purpose: To monitor changes in bone mineral density (BMD) of the proximal tibia and the calcaneus in patients with anterior cruciate ligament (ACL) rupture before and after arthroscopic reconstruction of the ligament, related to clinical data.
Type of study: A 2-year prospective cohort study with assessment of patient evaluation of knee performance, clinical scoring of surgical results, and measurement of BMD in the tibia and calcaneus.
Methods: Eighteen patients with a unilateral ACL rupture underwent an autogenous bone-patellar tendon-bone graft ACL reconstruction. The patients were examined before surgery and after 4, 12, and 24 months. BMD was assessed bilaterally in the proximal tibia and calcaneus using dual-photon absorptiometry and converted to a Z-score by use of BMD values from a group of healthy controls. Clinical evaluation included determination of Lysholm score, quantitative Lachman test, pivot-shift test, and the patients' self-reported highest level of activity and knee performance in sports and daily activities.
Results: There were significant declines in Z-score of the proximal tibia of the operated leg during the first year after surgery, whereas there was no change in the calcaneus and contralateral leg. In the lateral tibia, the Z-score was significantly lower at 24 months follow-up, compared with both controls and the noninjured side, whereas BMD of the medial tibia had returned to near normal levels. There were significant improvements in Lysholm score, highest level of activity, and knee performance in daily activities and sports. The patients' evaluation of improvement in knee performance in sports activities at 24 months follow-up was associated with an increase in Z-score of the injured leg.
Conclusions: We found a partially reversible decline in BMD of the proximal tibia after arthroscopic ACL reconstruction. Improvement in knee performance in sports activities was associated with an increase in BMD of the injured leg. BMD of the calcaneus remained unaffected in both legs.
Level of evidence: Level III, therapeutic case control study.