Stem size and stem alignment affects periprosthetic fracture risk and primary stability in cementless total hip arthroplasty

• Published in: Journal of orthopaedic research 2024-04, Vol.42 (4), p.829-836
• Main Authors: Konow, Tobias, Glismann, Katja, Lampe, Frank, Ondruschka, Benjamin, Morlock, Michael M., Huber, Gerd
• Format: Article
• Language: English
• Subjects: Arthroplasty, Replacement, Hip - adverse effects; Femur - surgery; Hip Prosthesis; Humans; periprosthetic fracture; Periprosthetic Fractures - etiology; preoperative planning; primary stability; Prosthesis Design; Retrospective Studies; stem alignment; stem size
• ISSN: 0736-0266; 1554-527X; 1554-527X
• DOI: 10.1002/jor.25729

The ideal stem size and stem position is important for the success of total hip arthroplasty, since it can affect early implant loosening and periprosthetic fractures (PPF). This study aimed to investigate how small deviations from the ideal stem size and position influences the PPF risk and primary stability. Six experienced surgeons performed preoperative templating based on which the benchmark size for each femur was determined. Consecutive implantations were performed in six cadaveric femur pairs—one side was implanted with an undersized stem followed by the benchmark size and the contralateral side with a benchmark size followed by an oversized stem (Corail, Depuy Synthes). Moreover, three different alignments (six varus, six neutral, six valgus‐undersized) were compared using 18 femurs. Cortical strains during broaching and implantation were measured, and laser scans were used to determine final stem position. All specimens underwent dynamic loading. Primary stability was estimated from stem subsidence and pull‐out forces. Templated stem size varied between surgeons (±1 size; p = 0.005). Undersizing increased stem subsidence by 320% (p