Macroscopic cartilage degeneration despite partially preserved imaging appearance in chronic neurological hip dislocation: findings from surgically resected femoral head specimens.

BACKGROUND

Chronic neurological hip dislocation is a severe musculoskeletal complication in non-ambulatory patients with cerebral palsy. Surgical decision-making is largely based on standard radiographs, although radiography provides only indirect information on articular cartilage status. Whether preoperative radiographic findings accurately reflect macroscopic cartilage degeneration remains unclear. This study evaluated the association between standard radiographic appearance and intraoperative anatomical evidence of cartilage destruction in chronic neurological hip dislocation.

METHODS

This retrospective observational study included non-ambulatory patients with cerebral palsy, all classified as GMFCS level V, who underwent unilateral metaphyseal femoral resection with structured myoplasty for chronic neurological hip dislocation. Each patient contributed one surgically resected femoral head. Preoperative pelvic radiographs were assessed for femoral head morphology, residual acetabular coverage, degenerative changes, and osteophytosis. Intraoperative macroscopic cartilage degeneration was evaluated immediately after resection by two senior neuro-orthopaedic surgeons using predefined anatomical regions and a standardized data collection form. Severe cartilage degeneration was defined as complete cartilage loss in at least one femoral head region. Diagnostic performance of radiographic criteria was assessed using intraoperative macroscopic degeneration as the reference standard.

RESULTS

A total of 29 patients and 29 femoral heads were included. Cartilage abnormalities were identified in 28 femoral heads, and complete cartilage loss in at least one anatomical region was observed in 16 cases. Complete cartilage loss was most frequently observed in the superolateral and anterosuperior regions of the femoral head. Complete radiographic loss of femoral head morphology showed a sensitivity of 43.8% and diagnostic accuracy of 51.7% for severe cartilage degeneration. Severe radiographic deformity showed a sensitivity of 56.3% and diagnostic accuracy of 55.2%, whereas marked radiographic osteophytosis showed a sensitivity of 31.3% and diagnostic accuracy of 48.3%. A composite radiographic criterion increased sensitivity to 68.8%, but diagnostic accuracy remained limited at 58.6%. Radiographic underestimation of severe cartilage damage occurred across all criteria.

CONCLUSIONS

Standard radiographs only partially reflect the extent of macroscopic cartilage degeneration in chronic neurological hip dislocation. Complete cartilage loss was most frequently observed in the superolateral and anterosuperior regions and could be present despite partially preserved radiographic morphology. Radiographic findings should therefore be interpreted together with clinical findings rather than as direct measures of cartilage integrity.