Changes in spinopelvic indices after hip arthroplasty and its influence on acetabular component orientation.

OBJECTIVE: To evaluate spinopelvic changes after hip arthroplasty in standing and ready-to-rise positions. METHODS: We compared pelvic tilt, sacral slope, cobb's angle, and hip flexion on pre and postoperative spinopelvic radiographs. RESULTS: Standing: All postoperative indices were similar to preoperative ones except sacral slope (mean difference:1.6°, p = 0.046). Ready-to-rise: All postoperative indices were similar to preoperative ones except pelvic tilt which was significantly greater postoperatively (mean difference: 5.1°, p = 0.017). Fifteen patients showed >10° increase in pelvic tilt postoperatively. CONCLUSION: Changes in pelvic tilt in ready-to-rise position can predispose to posterior edge loading, edge wear, and dislocation; especially with inadequate cup anteversion.

Review on squeaking hips.

Squeaking is a well-recognized complication for hard-on-hard bearings. The nature of squeaking is not yet completely understood however it is considered a multifactorial phenomenon. Patient, implant, and surgical factors play a role in squeaking. It is believed that mechanisms damaging the fluid film lubrication in which these bearings function optimally have a critical role. Such mechanisms include edge loading, stripe wear, impingement, third body particles and ceramic fracture. The resonance of metallic parts can produce noise in the human audible range hence the implant metallurgic composition and design may play a role. Implant positioning can facilitate impingement and edge loading enhancing the occurrence of squeaking. The recent introduction of large heads (> 36 mm) 4(th) generation ceramic-on-ceramic bearing may accentuate the conditions facilitating noise formation; however the current literature is insufficient. Clinically, squeaking may manifest in extreme hip positions or during normal gait cycle however it is rarely associated with pain. Evaluations of patients with squeaking include clinical and radiographic assessments. Computer tomography is recommended as it can better reveal ceramic breakage and implant malposition. The treatments for most squeaking patients include reassurance and activity modification. However for some, noise can be a problem, requiring further surgical intervention. In the occurrence of ceramic fracture, implant failure, extreme components malposition, instability and impingement, surgery should be advised. This review will aim to discuss the current literature regarding squeaking.

The kinematic relationship between sitting and standing posture and pelvic inclination and its significance to cup positioning in total hip arthroplasty.

PURPOSE: The aim of this study is to describe the influence of sitting and standing posture on sagittal pelvic inclination in total hip replacement patients to assist with correct acetabular component positioning. METHODS: Lateral radiographs of the pelvis and lumbar spine in sitting and standing positions were extracted. Pelvic tilt was measured using the vertical inclination of a line from the anterior superior iliac spine (ASIS) to pubic tubercle. Sacral inclination, Cobb angle of the lumbar spine and hip flexion were recorded. RESULTS: Sixty patients were identified with a mean age of 63. Men were more likely to flex the lumbar spine in sitting (p = 0.004); 80° of hip flexion is required for seated posture. Stiff hips required compensatory pelvic flexion and lumbar flexion in sitting. There is a linear relationship between hip flexion and pelvic tilt, hip flexion and lumbar lordosis. CONCLUSIONS: Pelvic orientation is determined by lumbar and hip stiffness. This impacts on acetabular version.