Vol.:(0123456789) 1 3 Archives of Orthopaedic and Trauma Surgery https://doi.org/10.1007/s00402-018-2876-2 ORTHOPAEDIC SURGERY The efect of humeral-fenestration diameter in Outerbridge–Kashiwagi arthroplasty on failure load of the distal humerus: a cadaveric biomechanical study Chih‑Kai Hong 1  · Ming‑Long Yeh 2,3  · I‑Ming Jou 4  · Cheng‑Li Lin 1,3  · Chih‑Hsun Chang 1  · Chih‑Hung Chang 5,6  · Wei‑Ren Su 1,3,7 Received: 6 November 2017 © Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Introduction Outerbridge–Kashiwagi ulnohumeral arthroplasty is an efective method in treating elbow osteoarthritis; how- ever, 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 methods 32 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° fexion for axial loading and 75° fexion 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. Results The failure loads of the 12 and 15 mm groups were not signifcantly diferent 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). Conclusions The failure load of distal humeri did not difer signifcantly 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 efectiveness of this surgical procedure. Keywords Outerbridge–Kashiwagi · Ulnohumeral arthroplasty · Fenestration · Distal humerus * Wei-Ren Su suwr@ms28.hinet.net Chih-Kai Hong yayahong@gmail.com Ming-Long Yeh mlyeh@mail.ncku.edu.tw I-Ming Jou ed109325@edah.org.tw Cheng-Li Lin jengli94@yahoo.com.tw Chih-Hsun Chang j90060713@gmail.com Chih-Hung Chang orthocch@mail.femh.org.tw 1 Department of Orthopaedic Surgery, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, No.138, Sheng-Li Road, Tainan 70428, Taiwan 2 Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan 3 Medical Device Innovation Center, National Cheng Kung University, Tainan, Taiwan 4 Department of Orthopedics, E-Da Hospital, I-Shou University, Kaohsiung, Taiwan 5 Department of Orthopaedic Surgery, Far Eastern Memorial Hospital, New Taipei City, Taiwan 6 Graduate School of Biotechnology and Bioengineering, Yuan Ze University, Taoyuan, Taiwan 7 Medical Device R&D Core Laboratory, National Cheng Kung University Hospital, Tainan, Taiwan