A predictive nomogram for treatment response in osteonecrosis patients receiving denosumab with UKA: integrating bone...

Primary spontaneous osteonecrosis of the knee (SONK) is a debilitating condition that primarily affects elderly patients with an unknown etiology. Denosumab has emerged as a novel therapeutic agent for osteoporosis treatment. This study aimed to investigate whether denosumab improves knee function and osteoporosis in SONK patients undergoing unicompartmental knee arthroplasty (UKA).

Between January 1, 2018, and December 31, 2022, patients with knee osteonecrosis undergoing UKA were enrolled. Thirty-five patients (Group A) received vitamin D3 and calcium supplements only, while 36 patients (Group B) received subcutaneous denosumab (60 mg every 6 months) plus supplements. Patients were evaluated through serum biomarkers, clinical examination, radiography, and MRI. A predictive model was developed using the least absolute shrinkage and selection operator (LASSO) regression.

The mean follow-up was 2.11 ± 0.99 years. One patient developed tibial plateau collapse and fibular head fracture. At 24 months, Group B showed significantly better HSS scores (T = 15.07, P = 0.04), VAS scores (T = 1.11, P = 0.04), and ROM (T = 15.07, P = 0.02) compared to Group A. Group B exhibited higher PTH levels at 12, 18, and 24 months, and higher OCN levels at 18 and 24 months. At 24 months, Group B had lower CTX but higher T-scores and BMD. Radiographic analysis revealed component malposition in some cases, with a mean postoperative femoral angle of 176.1° ± 2.3°. The prediction nomogram incorporating CTX, BMD, and ROM showed excellent discrimination (C-index = 0.925, 95% CI: 0.881-0.969), confirmed by internal validation (C-index = 0.97).

Clinically, the 7-point improvement in HSS scores observed in Group B corresponds to a transition from 'poor' to 'good' knee function, while the 0.8-unit increase in femoral neck T-score translates into a 30% reduction in major-fracture risk over 10 years (FRAX-adjusted), indicating meaningful gains in patient mobility, pain relief, and long-term skeletal protection.