Breakage of Cementless Press-Fit Femoral Stems for Total Hip Arthroplasty: Seven Dogs

Case Report: Femoral stem breakage of press-fit cementless implants following total hip arthroplasty (THA) is a rare complication. The objective of this study is to report breakage of eight press-fit stems with and without adjunctive bolt fixation. Records of client owned dogs that underwent THA from 2012 to 2022 were searched, and descriptive data and radiographs were reviewed. Median age and body weight were 18 months (range: 13–48) and 24 kg (range: 20–34). Median varus deviation was 3.9° (range: 0–7).

Seven of 8, and 6/8 stems were relatively undersized based on radiographic review and compared to recently published manufacturer's weight limit guidelines, respectively. No history of trauma was reported. Median percentage of bodyweight exceeding recommended stem weight limit at time of surgery was 3% (range: −13–22). A 17 mm +9 head was used in 4/8 cases. Median increase in neck length based on head choice was 28% (8–43). Median time to breakage and time to revision/explant were 585 days (range = 243–2,638) and 21 days (range = 2–32), respectively. No distal stem instability was encountered during surgery.

Electron microscopy analysis revealed striations and inclusions, suggesting fatigue lines and focal incomplete fusion. Stems here were relatively undersized based on both radiographic review and recent weight limit guidelines. The use of a 17 mm +9 head on relatively small stems may predispose to breakage. Stem breakage of stable BFX stems may be an avoidable complication.

Acknowledgments: DJ Marcellin-Little and MP Kowaleski are consultants for Biomedtrix.

Publication History

Article published online:
11 September 2023