Subsidence Following Revision Total Hip Arthroplasty Using Modular and Monolithic Components

Area of Science:

• Orthopedic Surgery
• Biomaterials Engineering
• Radiology

Background:

• The optimal femoral component for revision total hip arthroplasty (rTHA) is debated.
• Tapered, fluted, titanium (TFT) stems are frequently used in rTHA, with both modular and monoblock designs available.
• Femoral stem subsidence is a concern, potentially leading to aseptic loosening, instability, and leg length discrepancy.

Purpose of the Study:

• To compare the stem subsidence between modular and monoblock TFT stems in rTHA.
• To evaluate the incidence of significant subsidence (>5 mm) in both stem types.

Main Methods:

• Retrospective review of electronic medical records for rTHAs using modular or monoblock TFT stems from January 2013 to March 2018.
• Data collection included patient demographics, surgical indications, Paprosky classification, and stem subsidence at follow-up (3 months to 3 years).
• Statistical analysis employed two-sample t-tests and chi-squared tests.

Main Results:

• A total of 186 patients (106 modular, 80 monoblock) were analyzed.
• Modular stems exhibited significantly greater subsidence (3.9 ± 2.6 mm) than monoblock stems (2.3 ± 2.5 mm) (P < .001).
• A higher proportion of modular stems showed >5 mm subsidence (29.2%) compared to monoblock stems (11.3%) (P < .001).

Conclusions:

• Monoblock TFT stems demonstrated a lower incidence of postoperative subsidence compared to modular TFT stems.
• The findings suggest that monoblock TFT stems may offer an advantage in reducing subsidence-related complications in rTHA.
• Surgeons should consider the risk of subsidence when choosing between modular and monoblock TFT stems for rTHA.