Gait adaptations in patients with longstanding hip fusion

Journal of Orthopaedic Surgery, Dec 2003 by Thambyah, A, Hee, H T, De, S Das, Lee, S M

ABSTRACT

Purpose. To examine the long-term effects of hip arthrodesis in terms of gait adaptations.

Methods. Motion analysis was performed on 9 patients who underwent unilateral hip arthrodesis between 1979 and 1991. A standard clinical gait analysis 3-dimensional model for the lower limb was used to calculate the effect of the fused hip on walking, compared with the contralateral normal hip.

Results. Significant (p

Conclusion. It appears that the excess pelvic tilt observed was to achieve relative hip extension via increased relative lumbar lordosis, while the decreased coronal plane moments of the hip and knee observed were to reduce joint loading on the affected side.

Key words: arthrodesis; gait; hip joint

INTRODUCTION

Hip arthrodesis surgery is designed to cause a bridge of bone to develop across the hip socket, joining the ball and the socket of the hip joint. The aim is to remove the hip joint and replace it with a bony bridge. Indications for hip fusion include situations where a joint has been severely damaged and movement must be eliminated. Hip fusion is particularly relevant in infections of the hip joint and arthritis of the hip joint in very young individuals, for whom hip replacement would not be the most appropriate procedure. The surgical procedure involves making an incision in the hip joint, following which cartilage from the hip is removed. The bone surfaces are then positioned and held in place by pins or plates until new bone can grow across the remaining gap, fusing the hip joint. When the hip has been repaired with plates or screws, a physiotherapist often assists rehabilitation, specifically with respect to ambulation and muscle strengthening. Weightbearing on the hip is not permitted until the hip has completely fused. Ultimately, the result is a painless or nearly painless hip joint, which is capable of full weightbearing, and of withstanding very vigorous activity. Problems associated with hip fusion include possible pain, functional impairment, and degeneration in the neighbouring joints, such as the contralateral hip, both knees, and the lumbar spine. These developments tend to occur over a long period, however.

If the motion or load-bearing capacity of the hip joint is reduced, alterations in the motion and load at other joints of the lower extremities and back may occur.1 Loading at the hip joint, as well as the demands placed on the surrounding musculature and soft tissues, is largely influenced by the kinetics and kinematics of gait, as measured externally via motion analysis techniques.1 For instance, reduced moments reflect decreased muscle force and decreased load on the hip joint in the absence of increased antagonistic muscle activity, and may represent a type of painavoidance mechanism.1

Few studies on gait analysis of patients with hip problems have attempted to relate gait adaptations to the patients' clinical characteristics.2-3 To date, there has been little quantifiable data available defining the characteristics of walking in patients with long-term hip fusion. A better understanding of various gait adaptations in patients with fused hips may provide insight to address clinical concerns on the potential long-term effects of hip arthrodesis. The objective of this study was to examine the effects of a long-term fused hip on walking, comparing the fused hip with the contralateral unfused hip in individual patients who had previously undergone hip arthrodesis.

PATIENTS AND METHODS

11 patients underwent arthrodesis of the hip at the National University Hospital, Singapore, between 1979 and 1991. In 1999, attempts were made to recall these patients for gait and clinical evaluation, with the help of the Immigration Department in Singapore. Two patients could not be located. Nine patients agreed to take part in the study, including 7 men and 2 women. The average age of the patients at the time of surgery was 37.6 years (range, 28-54 years). The average follow-up period was 14.8 years (range, 8-20 years). Arthrodesis of the hip was performed for primary osteoarthritis in 3 patients, post-traumatic arthritis in 3 patients, tuberculous arthritis in 2 patients, and septic arthritis in one patient. The position of the fused hip was 30� flexion, neutral (abduction/adduction), 10" to 15� external rotation. Clinical outcome was graded using the Harris hip score.4

Gait analysis was performed using reflective markers placed on key anatomical landmarks. These were then tracked in space and time via retro-reflective infra-red light-detecting cameras (TM86; Vicon Motion Systems Ltd, Oxford, UK), as the patient walked over a force platform. Each patient was fitted with 17 skin markers, following a typical gait analysis protocol as outlined by the manufacturers of the gait analysis system and described previously.5 Briefly, the markers were placed on selected anatomic features on the left and right sides, that is, on the anterior superior iliac spine, the greater trochanter, tibial tuberosity, fibula head, lateral malleolus, 5th metatarsal base, mid-heel, the calcaneum, and the posterior pelvis. A Kistler force platform (Kistler Instrumente AG, Winterthur, Switzerland) was used to obtain ground reaction forces at foot to ground contact. An Adtech Motion Analysis System (AMASS; Adtech, Adelphi, US) and a Vicon Clinical Manager (Vicon Motion Systems Ltd, Oxford, UK) were used in the analysis of the gait data. The mathematical model used to calculate joint motion and moments was based on the standard clinical model used in the video motion analysis system.6 The objective was to assess the deviation caused by the fused hip to the kinematics and kinetics of a normal gait pattern. The hip joint on the fused side was thus assumed to exist, and motion and kinetics were calculated for that side as calculated for the normal, unaffected contralateral hip. The null hypothesis was that the calculated kinematics and kinetics of the fused hip would be no different from those of the contralateral side. The paired gait analysis data of the contralateral and fused limbs were compared for the 9 patients, and peak values observed were tested for significant differences using the paired f test, with p