How Does Contact Length Impact Titanium Tapered Splined Stem Stability: A Biomechanical Matched Pair Cadaveric Study

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Biomechanics

Background:

• Titanium tapered stems (TTS) are crucial for femoral diaphysis fixation in revision total hip arthroplasty.
• Initial stability of TTS is critical for surgical success.
• Optimal implant design and surgical technique require understanding minimum contact length and taper angle effects on axial stability.

Purpose of the Study:

• To determine the minimum cortical contact length required for initial axial stability of TTS.
• To investigate the impact of varying taper angles on the axial stability of TTS.
• To provide data-driven guidance for operative decision-making in revision hip arthroplasty.

Main Methods:

• Two TTS designs with different taper angles (2° vs 3.5°) were implanted in human femora.
• Cortical contact lengths of 2 cm, 3 cm, and 4 cm were tested.
• Axial load was applied until failure (subsidence >5 mm or fracture), with failure defined as loss of initial stability.

Main Results:

• A 2 cm contact length resulted in failure in all tested femora (P < .02).
• Femora with 3 cm and 4 cm contact lengths demonstrated successful initial stability, with no significant difference between them (P = .12).
• The taper angle of the TTS did not significantly affect success rates at any tested contact length.

Conclusions:

• A 4 cm cortical contact length ensures reliable initial axial stability for TTS.
• A 2 cm contact length is insufficient for initial TTS fixation, regardless of taper angle.
• 3 cm of cortical contact provides successful initial fixation in the majority of cases for both taper designs.