• I-Ning Lo, Yun-Hsuan Tzeng, Chien-Shun Wang, Tzu-Cheng Yang, Chun-Cheng Lin, and Chao-Ching Chiang.
• Division of Orthopaedic Trauma, Department of Orthopaedics and Traumatology; Taipei Veterans General Hospital, Department of Orthopaedics; School of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan, Department of Orthopaedics; School of Medicine; National Yang-Ming University, Taipei, Taiwan. Electronic address: Elaine.lo.198881@gmail.com.
• Injury. 2021 Jul 1; 52 (7): 1801-1806.

BackgroundBipolar hemiarthroplasty is a well-established treatment for displaced femoral neck fracture in elderly patients. Implant subsidence is a potential complication with cementless femoral stems, and smaller canal fill ratio has been reported as a radiographic risk factor. We aimed to determine the risk factors for subsidence, particularly the initial implant position relative to the resected medial calcar of proximal femur.MethodsWe retrospectively reviewed all cementless bipolar hemiarthroplasties performed using a single proximally hydroxyapatite-coated femoral stem in patients with a minimum radiographic follow-up of 12 weeks between January 2017 and December 2018. The amount of subsidence (significant subsidence defined as ≥ 5 mm), canal fill ratio, and implant position relative to the point of resected medial calcar (position A: medial and superior to calcar; position B: lateral and superior to calcar; position C: lateral and inferior to calcar) were measured and analyzed.ResultsOne-hundred eighty patients were identified (mean age: 80.9 years). Significant subsidence was observed in 52 patients (28.9%). On multivariate analysis, older age, lower canal fill ratio, implant position B, C, and less medial overhang of stem were independent risk factors for early implant subsidence. The risk ratio of position B and C to position A was 5.13 (95% confidence interval, 2.23-11.80).ConclusionIn our analysis, older age and lower canal fill ratio were associated with increased risk of subsidence, whereas implant with position A and more medial overhang were less prone to subsidence with the tapered proximally hydroxyapatite-coated implant.Copyright © 2021 Elsevier Ltd. All rights reserved.

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