|
Back to 2017 Scientific Program ePosters
Fracture Risk in Ulnohumeral Arthroplasty - How Does Fenestration Size Influence Structural Integrity?
Leo T. Kroonen, MD1; Patrick B Morrissey, MD2; Ryan Myers, MD2; Daniel Houskamp, DO2
1Southern California Permanente Medical Group, San Diego, CA, 2Naval Medical Center San Diego, San Diego, CA
Introduction: Ulnohumeral arthroplasty (UHA) is a common surgery for moderate elbow arthritis. Despite results suggesting over 85% of patients reporting good/excellent results with validated outcomes measures, there are concerns over the integrity of the distal humerus after fenestration. One complication that is often cited is postoperative fracture. The purpose of this study is to examine the relationship between the size of fenestration and fracture risk. By defining this risk, providers can appropriately counsel patients as well as institute appropriate post procedure activity restrictions. Surgeons can also understand the maximum amount of bone that can be resected while minimizing postoperative fracture risk.
Methods: Using a fourth generation sawbones model, load to failure and site of fracture were investigated for incremental fenestration sizes. 5 samples in each group were subjected to a uniform extension stress on a biomechanical testing machine. The control group was comprised of unfenestrated humerus samples. Fenestration size began at 10mm and increased by 3mm increments to 31mm. The diaphysis of each sample was secured to the custom testing apparatus 95mm from the distal aspect of the humerus and loaded at a rate of 0.2mm/sec until sample failure. Load at failure and site of fracture were recorded for each sample. Analysis of variance (ANOVA), with post hoc multiple comparisons and a correction for accumulating p–values (Scheffé’s method), was performed for both endpoints.
Results: 45 sawbones were tested. Average load at sample failure was equivalent for each fenestration group up to 25mm. At 28mm, average load to failure began to decrease, becoming statistically significant between 28mm and 31mm (p < 0.001). For the first 35 samples, only three (9%) failed through the fenestration site, one each at 10mm, 16mm, and 25mm. The other samples fractured through the diaphysis at their attachment to the custom mount. At 28mm, four out of five (80%) samples fractured through the fenestration, and at 31mm all five (100%) samples fractured through the fenestration. This change in fracture site became statistically significant between 25mm and 28mm (p = 0.012).
Discussion: Distal humeral fenestration compromises structural integrity, but within typical resection ranges of 10-15mm there is no increased risk of fracture. Fracture risk does not significantly increase until greater than 25mm of bone is resected. Based on this study, we do not recommend any activity limitations following initial surgical recovery, but do recommend against aggressive distal humeral fenestrations (larger than 25mm) when performing UHA.
Back to 2017 Scientific Program ePosters
|
