Factors affecting bony impingement in hip arthroplasty

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Medical imaging analysis

Background:

• Hip arthroplasty aims to restore joint function and range of motion.
• Bony impingement can limit range of motion after hip replacement.
• Understanding factors influencing range of motion before bony impingement (ROMBI) is critical for surgical success.

Purpose of the Study:

• To investigate the impact of various anatomical and surgical parameters on ROMBI in hip arthroplasty.
• To compare ROMBI with range of motion before component impingement and native hip range of motion.
• To determine the relative importance of acetabular versus femoral parameters on ROMBI.

Main Methods:

• Utilized computer modeling of computed tomographic scans from 10 patients.
• Analyzed variables including acetabular offset/height, femoral offset/height/anteversion, and osteophyte removal.
• Compared ROMBI with pre-component impingement ROM and native hip ROM.

Main Results:

• Decreased total offset and limb shortening led to reduced ROMBI.
• Acetabular offset and height demonstrated a more significant impact on ROMBI than femoral parameters.
• ROMBI loss due to decreased acetabular offset was not fully compensated by increased femoral offset or osteophyte removal.
• Reduced acetabular offset and increased head diameter increased bony impingement while decreasing component impingement.

Conclusions:

• Acetabular morphology, specifically offset and height, plays a dominant role in determining ROMBI after hip arthroplasty.
• Surgical planning should prioritize optimizing acetabular parameters to maximize ROMBI.
• Osteophyte removal and femoral component adjustments have limited capacity to restore ROMBI lost due to significant acetabular under-coverage.