T he dislocation rate in the conventional posterior approach in bipolar hemiarthroplasty (BHA) is double that in the anterior approach [1 , 2]. However, immobilization to reduce the risk of postoperative dis- location aſter a BHA can delay the patient’s rehabilita- tion [3]. Preserving soſt tissue in a BHA is important for reducing the risk of postoperative dislocation, and a variety of surgical approaches have been reported recently considering this complication [4]. e piri- formis tendon preservation technique during the pos- terolateral approach in total hip arthroplasty (THA) is reportedly superior to the reattachment technique in terms of contiguity, muscle atrophy, and dislocation [5]. Kim et al. reported a THA method that preserves muscles from the piriformis muscle to the internal obturator muscle (i.e., an external rotator preservation procedure [ERP]) and had good outcomes with no cases of postoperative dislocation [6]. We have performed BHAs using a conjoined tendon-preserving posterior (CPP) approach, which dissects only the external obturator muscle and pre- serves the gemellus inferior muscle. However, extra care is needed with muscle- and tendon-preserving approaches in geriatric patients. We conducted the present study to evaluate the intraoperative findings and Acta Med. Okayama, 2021 Vol. 75, No. 1, pp. 25-30 CopyrightⒸ 2021 by Okayama University Medical School. http://escholarship.lib.okayama-u.ac.jp/amo/ Original Article Bipolar Hip Arthroplasty Using a Conjoined Tendon-preserving Posterior Approach in Geriatric Patients Tomonori Tetsunaga a＊ , Tomoko Tetsunaga a , Kazuki Yamada b , Tomoaki Sanki a , Yoshi Kawamura a , and Toshifumi Ozaki a a Department of Orthopaedic Surgery, Okayama University Hospital, b Department of Medical Materials for Musculoskeletal Reconstruction, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8558, Japan In bipolar hemiarthroplasty (BHA), it is important to preserve soſt tissue to reduce the risk of postoperative dislocation. A variety of surgical approaches for BHA are available, but extra care is needed with muscle- and tendon-preserving approaches in geriatric patients. We investigated the usefulness of BHA using a conjoined tendon-preserving posterior (CPP) approach, in which only the external obturator muscle is dissected, in geri- atric patients. We retrospectively analyzed the cases of 40 femoral neck fracture patients (10 men, 30 women) aged ≥ 80 years who underwent BHA using the CPP approach. e patients’ average age was 85.8 years (80-94 years). We examined the operation time, bleeding, preservation of short external rotator muscles, complica- tions, and stem alignment and subsidence from postoperative radiographs. Although gemellus inferior muscle injury was detected in 4 patients (10%), the hip joint stability was very excellent in all cases. ere was no intraoperative fracture or postoperative dislocation. On postoperative radiographs, all femoral stems were in a neutral position. ere was no stem subsidence in all 40 patients. BHA using the CPP approach appeared to be useful even in geriatric patients. Key words: bipolar hip arthroplasty, geriatric patient, conjoined tendon-preserving posterior approach Received May 26, 2020 ; accepted September 25, 2020. ＊ Corresponding author. Phone : +81-86-235-7273; Fax : +81-86-223-9727 E-mail : tomonori_t31@yahoo.co.jp (T. Tetsunaga) Conflict of Interest Disclosures: No potential conflict of interest relevant to this article was reported.