Repeatable procedure for evaluating taper damage on femoral stems with modular necks

Area of Science:

• Biomaterials Engineering
• Orthopedic Surgery
• Tribology

Background:

• Dual-taper modularity in femoral stems is common in hip arthroplasty.
• Assessing the performance and longevity of these modular junctions is critical.
• Understanding taper surface damage is key to predicting implant survival.

Purpose of the Study:

• To develop a repeatable method for quantifying damage on dual-taper modular femoral stem surfaces.
• To determine if damage area is a reliable indicator of stem performance under simulated physiological conditions.
• To correlate damage area with material degradation during in vitro testing.

Main Methods:

• Photogrammetry was employed for objective identification and measurement of surface features.
• Defined criteria were used to categorize six surface features, including four distinct damage modes.
• Twenty-four dual-taper modular necks (15 in vitro, 9 explanted) were analyzed.

Main Results:

• A standardized photogrammetric method enabled accurate and repeatable damage area measurement.
• Damage area proved useful in distinguishing performance across different in vitro tests.
• Combined burnished smooth and textured damage areas linearly correlated with weight loss (material removed).

Conclusions:

• Quantifying taper surface damage area is a valuable metric for assessing modular femoral stem performance.
• Higher in vitro test loads and stiffer femoral stems resulted in significantly larger damage areas.
• This methodology aids in understanding failure modes and improving implant design.