The complex relationship between acetabular component position and spinopelvic mobility in patients following total hip arthroplasty (THA) renders it difficult to optimize acetabular component positioning. Mobility of the normal lumbar spine during postural changes results in alterations in pelvic tilt (PT) to maintain the sagittal balance in each posture and, as a consequence, markedly changes the functional component anteversion (FCA). This study aimed to investigate the in vivo association of lumbar degenerative disc disease (DDD) with the PT angle and with FCA during postural changes in THA patients. A total of 50 patients with unilateral THA underwent CT imaging for radiological evaluation of presence and severity of lumbar DDD. In all, 18 patients with lumbar DDD were compared to 32 patients without lumbar DDD. In vivo PT and FCA, and the magnitudes of changes (ΔPT; ΔFCA) during supine, standing, swing-phase, and stance-phase positions were measured using a validated dual fluoroscopic imaging system.Aims
Methods
Eighteen hip fusions were converted to total
hip replacements. A constrained acetabular liner was used in three hips.
Mean follow up was five years (two to 15). Two (11%) hips failed,
requiring revision surgery and two patients (11%) had injury to
the peroneal nerve. Heterotopic ossification developed in seven
(39%) hips, in one case resulting in joint ankylosis. No hips dislocated. Conversion of hip fusion to hip replacement carries an increased
risk of heterotopic ossification and neurological injury. We advise
prophylaxis against heterotropic ossification. When there is concern
about hip stability we suggest that the use of a constrained acetabular
liner is considered. Despite the potential for complications, this procedure
had a high success rate and was effective in restoring hip function.
