Aims

Total hip arthroplasty (THA) patients undergoing or having a prior lumbar spine fusion (LSF) have an increased risk of mechanical complications. The aim of this registry-based, retrospective comparative cohort study is to assess the longer term survival of THA in patients who have undergone a LSF during a 17-year period (2000 to 2017).

Aims. Long-term clinical outcomes for ceramic-on-ceramic (CoC) bearings are encouraging. However, there is a risk of squeaking. Guidelines for the orientation of the acetabular component are defined from static imaging, but the position of the pelvis and thus the acetabular component during activities associated with edge-loading are likely to be very different from those measured when the patient is supine. We assessed the functional orientation of the acetabular component. Patients and Methods. A total of 18 patients with reproducible squeaking in their CoC hips during deep flexion were investigated with a control group of 36 non-squeaking CoC hips. The two groups were matched for the type of implant, the orientation of the acetabular component when supine, the size of the femoral head, ligament laxity, maximum hip flexion and body mass index. . Results. The mean functional anteversion of the acetabular component at the point when patients initiated rising from a seated position was significantly less in the squeaking group than in the control group, 8.1° (-10.5° to 36.0°) and 21.1° (-1.9° to 38.4°) respectively (p = 0.002). . Conclusion. The functional orientation of the acetabular component during activities associated with posterior edge-loading are different from those measured when supine due to patient-specific pelvic kinematics. Individuals with a large anterior pelvic tilt during deep flexion might be more susceptible to posterior edge-loading and squeaking as a consequence of a significant decrease in the functional anteversion of the acetabular component. . Cite this article: Bone Joint J 2016;98-B:910–16

Aims. The pelvis rotates in the sagittal plane during daily activities. These rotations have a direct effect on the functional orientation of the acetabulum. The aim of this study was to quantify changes in pelvic tilt between different functional positions. Patients and Methods. Pre-operatively, pelvic tilt was measured in 1517 patients undergoing total hip arthroplasty (THA) in three functional positions – supine, standing and flexed seated (the moment when patients initiate rising from a seated position). Supine pelvic tilt was measured from CT scans, standing and flexed seated pelvic tilts were measured from standardised lateral radiographs. Anterior pelvic tilt was assigned a positive value. Results. The mean pelvic tilt was 4.2° (-20.5° to 24.5°), -1.3° (-30.2° to 27.9°) and 0.6° (-42.0° to 41.3°) in the three positions, respectively. The mean sagittal pelvic rotation from supine to standing was -5.5° (-21.8° to 8.4°), from supine to flexed seated was -3.7° (-48.3° to 38.6°) and from standing to flexed seated was 1.8° (-51.8° to 39.5°). In 259 patients (17%), the extent of sagittal pelvic rotation could lead to functional malorientation of the acetabular component. Factoring in an intra-operative delivery error of ± 5° extends this risk to 51% of patients. Conclusion. Planning and measurement of the intended position of the acetabular component in the supine position may fail to predict clinically significant changes in its orientation during functional activities, as a consequence of individual pelvic kinematics. Optimal orientation is patient-specific and requires an evaluation of functional pelvic tilt pre-operatively. Cite this article: Bone Joint J 2017;99-B:184–91

Pelvic obliquity is a common finding in adolescents with cerebral palsy, however, there is little agreement on its measurement or relationship with hip development at different gross motor function classification system (GMFCS) levels.

The purpose of this investigation was to study these issues in a large, population-based cohort of adolescents with cerebral palsy at transition into adult services.

The cohort were a subset of a three year birth cohort (n = 98, 65M: 33F, with a mean age of 18.8 years (14.8 to 23.63) at their last radiological review) with the common features of a migration percentage greater than 30% and a history of adductor release surgery.

Different radiological methods of measuring pelvic obliquity were investigated in 40 patients and the angle between the acetabular tear drops (ITDL) and the horizontal reference frame of the radiograph was found to be reliable, with good face validity. This was selected for further study in all 98 patients.

The median pelvic obliquity was 4° (interquartile range 2° to 8°). There was a strong correlation between hip morphology and the presence of pelvic obliquity (effect of ITDL on Sharpe’s angle in the higher hip; rho 7.20 (5% confidence interval 5.59 to 8.81, p < 0.001). This was particularly true in non-ambulant adolescents (GMFCS IV and V) with severe pelvic obliquity, but was also easily detectable and clinically relevant in ambulant adolescents with mild pelvic obliquity.

The identification of pelvic obliquity and its management deserves closer scrutiny in children and adolescents with cerebral palsy.

Cite this article: Bone Joint J 2015;97-B:1435–40.