Case Report Conversion of Fused Hip to Total Hip Arthroplasty With Presurgical and Postsurgical Gait Studies Stephanie J. Bonin, MS,* Moataz A. Eltoukhy, PhD,* W. Andrew Hodge, MD, yz and Shihab S. Asfour, PhD* Abstract: This case study presents a subject with a fused hip converted to total hip arthroplasty. Kinematic gait analysis was conducted on 3 occasions, presurgery, 4 months postsurgery, and 2.5 years postsurgery. Presurgery data showed decreased cadence and shorter step length; sound limb possessed increased hip, knee range of motion (ROM), and increased knee flexion during stance; the affected limb had minimal hip motion and normal knee ROM with abnormal pattern. At 4 months postsurgery, the sound limb showed decreased step length, whereas the affected limb showed increased knee extension during stance and increased hip ROM. Data obtained at 2.5 years postsurgery indicated decreased cadence and speed and increased ROM in both limbs. The total hip arthroplasty had provided relief of chronic back and affected hip pain and improved mobility. Gait-specific training is recommended. Keywords: gait analysis, fusion, hip conversion, range of motion, THA. © 2012 Elsevier Inc. All rights reserved. In young patients with unilateral hip disease, surgical hip fusion is often the preferred treatment; however, the lack of motion at the hip results in compensatory movement at the uninvolved joints to produce a useful gait [1]. In addition, back and ipsilateral knee pain are the most common complaints leading to conversion of a fused hip to a total hip arthroplasty (THA) [2]. The hip fusion is being replaced by THA to restore hip range of motion (ROM) and reduce abnormal stresses on other joints and the spine [3]. Conversion of an ankylosed hip to a THA is technically demanding due to the initial disease, the effect of any previous operations on both bone and soft tissues, and the atrophy of the periarticular muscles [2]. A case study was conducted to evaluate changes in gait parameters and sagittal ROM of a female subject who had sepsis and bone destruction of her right hip as an infant. She underwent multiple procedures as a child and spontaneous right hip fusion at 10 years old. By age 30 years, she developed increased back pain and right hip pain, spine and knee arthritis, and difficulty walking and underwent a conversion of the fused hip to a THA. The subject's gait was evaluated on 3 occasions: presurgery, 4 months postsurgery, and 2.5 years post- surgery. It is hypothesized that the subject's gait parameters and lower limb sagittal plane ROM will significantly differ across the testing occasions. Materials and Methods The surgical procedure in 2007 included a complete takedown of fused right hip and conversion to a THA with a Depuy Orthopedic, Inc (Warsaw, Ind), Triatholon Multi-holed Revision Cup with Locking Liner and a Stryker Orthopedic, Inc (Mahwah, NJ), Restoration Modular Stem. The patient had a solidly fused right hip with approximately 20° of abduction, 20°of flexion, and 15° of external rotation. Postsurgery, the affected limb had 100° of flexion with full extension, 50° of abduction, 30° of adduction, 45°of external rotation, and 20° of internal rotation as passive ROM in the operating From the *Department of Industrial Engineering, College of Engineering, University of Miami, Florida; yInstitute for Mobility and Longevity, Jupiter, Florida; and zThe Scripps Research Institute, Jupiter, Florida. Submitted February 18, 2011; accepted July 29, 2011. The Conflict of Interest statement associated with this article can be found at doi:10.1016/j.arth.2011.07.013. Reprint requests: Shihab Asfour, PhD, Professor and Chairman, Department of Industrial Engineering, College of Engineering, University of Miami, 1251 Memorial Drive, Coral Gables, FL 33146. © 2012 Elsevier Inc. All rights reserved. 0883-5403/2703-0028$36.00/0 doi:10.1016/j.arth.2011.07.013 493.e9 The Journal of Arthroplasty Vol. 27 No. 3 2012