Fracture Risk in Ulnohumeral Arthroplasty-A Biomechanical Study

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Surgical outcomes

Background:

• Ulnohumeral arthroplasty, or the Outerbridge-Kashiwagi procedure, is a treatment for ulnohumeral arthritis.
• Concerns exist regarding the potential loss of distal humerus integrity due to fenestration in this procedure.

Purpose of the Study:

• To investigate the relationship between distal humeral fenestration size and fracture risk.
• To determine the threshold at which fenestration compromises structural integrity.

Main Methods:

• A fourth-generation sawbones model was used to simulate distal humeral fenestration.
• Samples underwent load-to-failure testing with incrementally increasing fenestration sizes (10 mm to 31 mm).
• Load at failure and fracture site were recorded for each sample.

Main Results:

• No significant decrease in load-to-failure was observed for fenestrations up to 25 mm.
• A statistically significant decrease in load-to-failure and increased fracture through the fenestration occurred at 28 mm and 31 mm.
• Fracture through the fenestration became statistically significant between 25 mm and 28 mm.

Conclusions:

• Distal humeral fenestration compromises structural integrity.
• Fenestrations up to 25 mm do not increase fracture risk.
• Fenestrations larger than 25 mm should be avoided to prevent compromising structural integrity.