Optimizing instrument selection during core decompression for osteonecrosis of the femoral head: a 3D analysis

Core decompression is the leading surgical treatment for pre-collapse osteonecrosis of the femoral head (ONFH). There are many different instruments that are used during core decompression, ranging from drill bits to expandable reamers, yet there is limited guidance regarding how to select the appropriate instrument for an individual patient's unique anatomy. We sought to examine how lesion characteristics affect instrument performance. To quantitatively compare instruments' efficacy at removing necrotic bone while preserving healthy bone, we developed an in-silico metric called the resection fraction, defined as the volume of necrotic bone resected divided by the total volume of bone (healthy and necrotic) resected. We hypothesize the optimal instrument will vary with lesion size and type (ARCO 2021).

CT-based 3D models of 100 femurs with ONFH were created from a retrospective database of patients who underwent 3D guided computer navigated core decompression at our institution. Using these models, core decompression procedures were simulated with six different instruments. 3D volumetric analysis was used to determine the volumes of necrotic and healthy bone resected, and the resection fraction was calculated. Statistical analysis was performed to compare instrument performance across all lesions, as well as by lesion size and type.

A total of 100 hips from 75 unique patients with ONFH were modeled and each hip's core decompression procedure was simulated with six different instruments. All three expandable reamers had higher resection fractions compared to straight instruments (drill bits). For small volume lesions, the small expandable reamer had the highest resection fractions. The medium expandable reamer had the highest resection fractions for larger lesions. The large expandable reamer had lower resection fractions across all sizes.

Compared to straight instruments, expandable reamers had the highest resection fractions. To maximize resection fraction, surgeons should personalize instrument choice to patient anatomy; small expandable reamers should be used for smaller lesions, while medium-sized reamers should be used for larger lesions. The largest expandable reamer performed worse than either the small or medium reamer for almost all lesions. Further work is needed to validate the in-silico resection fraction metric with clinical outcomes.