Bone Tunnel Microarchitecture and Early Functional Recovery After Anterior Cruciate Ligament Reconstruction: A Prospective HR-pQCT Cohort Study.

BACKGROUND

The biological healing of the bone tunnel is crucial for success in anterior cruciate ligament reconstruction (ACLR). Nonetheless, conventional imaging cannot assess the key microarchitectural properties of the healing bone, resulting in a gap in our understanding of early recovery.

PURPOSE/HYPOTHESIS: This study aimed to identify the specific bone structure and density measurements most closely associated with successful recovery during the first 6 months. It was hypothesized that the microarchitectural properties of the bone tunnel, quantified by high-resolution peripheral quantitative computed tomography (HR-pQCT), would be directly correlated with functional and patient-reported outcomes in the early postoperative phase.

STUDY

DESIGN

Cohort study; Level of evidence, 2.

METHODS

In a prospective cohort study, 50 patients undergoing primary hamstring ACLR were assessed at 4 and 6 months postoperatively. HR-pQCT was used to quantify bone tunnel parameters-including bone volume/total volume (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular separation (Tb.Sp), and tunnel enlargement ratio. The isokinetic muscle strength test, single-leg hop test, ultrasound muscle thickness assessment, and patient-reported outcomes were assessed for clinical performance. The Spearman correlation was used to examine the relationship between knee joint clinical performance and bone tunnel conditions. Receiver operating characteristic (ROC) analysis was performed to identify predictive thresholds for good functional recovery.

RESULTS

HR-pQCT data revealed that at 4 months, femoral BV/TV (r = 0.361) and Tb.Th (r = 0.333) were positively correlated with knee extension strength, while the tibial tunnel enlargement ratio was negatively correlated (r = -0.380). Tibial Tb.N (r = 0.339) correlated positively with the International Knee Documentation Committee score, while tibial Tb.Sp (r = -0.367) correlated negatively. Femoral BV/TV at 4 months emerged as a significant predictor of early functional recovery (area under the ROC curve = 0.680; P = .027), with an optimal cutoff value of 0.2607.

CONCLUSION

The microarchitectural quality of the bone tunnel, as assessed by HR-pQCT, is modestly correlated with the early functional recovery after ACLR, particularly at the 4-month postoperative time period.