• Chih-Kai Hong, Ming-Long Yeh, I-Ming Jou, Cheng-Li Lin, Chih-Hsun Chang, Chih-Hung Chang, and Wei-Ren Su.
• Department of Orthopaedic Surgery, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, No.138, Sheng-Li Road, Tainan, 70428, Taiwan.
• Arch Orthop Trauma Surg. 2018 May 1; 138 (5): 623-628.

IntroductionOuterbridge-Kashiwagi ulnohumeral arthroplasty is an effective method in treating elbow osteoarthritis; however, distal humerus fracture after surgery can become a critical issue. A previous biomechanical study has shown that the failure load of the distal humerus decreases after a fenestration, but the size of the fenestration hole has not yet been discussed.Materials And Methods32 fresh-frozen cadaveric distal humeri were obtained. Two drill sizes were chosen for fenestration: 12 and 15 mm in diameter. Two directions of force were applied with a materials testing machine for biomechanical testing: 5° flexion for axial loading and 75° flexion for anterior-posterior (AP) loading. Each specimen randomly received one of the two fenestration sizes, and force directions. All specimens were loaded to failure at a rate of 2 mm/min.ResultsThe failure loads of the 12 and 15 mm groups were not significantly different in either axial loading(3886 ± 1271 N vs 4286 ± 901 N) or AP loading(2303 ± 803 N vs 1897 ± 357 N). All specimens loaded with axial force failed via the fenestration holes; however, during AP loading, some specimens failed through the fenestration holes, while others at diaphysis (p = 0.28).ConclusionsThe failure load of distal humeri did not differ significantly after fenestration of 12 or 15 mm. The clinical relevance is that as the risk of distal humerus fracture is not exacerbated, a larger-size fenestration hole could be of help to improve the effectiveness of this surgical procedure.

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