The Journal of Arthroplasty Vol. 12 No. 4 1997 Functional Leg-length Inequality Following Total Hip Arthroplasty Chitranjan S. Ranawat, MD, and Jos~ A. Rodriguez, MD Abstract: A consecutive series of 100 patients undergoing primary total hip arthro- plasty were assessed for functional leg-length inequality (FLLI). In addition, the medical records of all patients treated for FLLI by the senior author (C.S.R.) in the past 15 years was reviewed. A questionnaire was distributed to the members of The Hip Society specifically to query the prevalence, etiology, and management of FLLI. Fourteen percent of patients were noted to have pelvic obliquity and FLLI 1 month after surgery. All had resolution of the symptoms by 6 months after surgery. Nine patients have been identified over the past 15 years with persistent FLLI. Among the causes suggested by respondents to the questionnaire are tightness of periarticular soft tissues with resultant pelvic obliquity and degenerative conditions of the spine with contracture. Methods of treatment and prevention are discussed. Key words: hip, prosthesis, leg length, pelvic obliquity. The sensation of limb-length inequality after total hip arthroplasty (THA) has been well de- scribed [1-4]. Most often this sensation relates to a change in the actual length of the reconstructed hip, sometimes requiring a contralateral shoe lift for correction. Techniques of accurate preoperative templating, anatomic component geometry, and intraoperative assessment have diminished the prevalence of inadvertent lengthening of the limb by reproducing the normal anatomic relation- ships {2,5-7]. A small number of patients, how- ever, may suffer from a sense of functional limb- length inequality despite attempts to accurately restore these anatomic relationships. When a sense of leg-length discrepancy occurs after THA, it can usually be broken down into two components [8]. The actual or true leg-length inequality is caused by lengthening of the pros- thetic head-neck distance. The apparent or func- tional leg-length inequality (FLLI) describes the From the Center for Total Joint Replacement, Lenox Hill Hospital, New York, New York. Reprint requests: Chitranjan S. Ranawat, MD, Center for Total Joint Replacement, Lenox HilI Hospital, 130 East 77th Street, 1 lth Floor, New York, NY 10021. © 1997 Churchill Livingstone Inc. amount that is attributable to other factors such as the tightness of the anterolateral soft tissues about the hip and degenerative disease with scoliosis of the lumbar spine, causing obliquity of the penis. The incidence and causes of functional leg- length inequality are not well described. Most sur- geons perform THA with the goal of reestablishing leg length, anatomic geometry equal to the normal opposite side, and optimal soft tissue tension around the hip to maximize stability. The soft tis- sue tension can be considered to have a horizontal component and a vertical component, both of which should be reestablished and balanced with hip arthroplasty. In cases where the horizontal component of the soft tissue tension is exceeded (offset increased), a painful stretching of the con- tracted anterior and lateral structures may result. Ireland and Kessel described the functional leg- length inequality in children with pelvic obliq- uity [9]. Functional leg-length inequality after THA may similarly be caused by degenerative dis- ease of the lumbar spine with structural scoliosis and pelvic tilt. In these cases, the limitation in the mobility of the spine makes patients more sensitive to alterations in the length and kinematics of the hip joint because of their inability to compensate for these changes. 359