The pelvis is not a static structure. It rotates in the sagittal plane depending upon the activity being performed. These dynamic changes in pelvic tilt have a substantial effect on the functional orientation of the acetabulum. The aim of this study was to quantify the changes in sagittal pelvic position between three functional postures. Pre-operatively, 90 total hip replacement patients had their pelvic tilt measured in 3 functional positions – standing, supine and flexed seated (posture at “seat-off” from a standard chair), Fig 1. Lateral radiographs were used to define the pelvic tilt in the standing and flexed seated positions. Pelvic tilt was defined as the angle between a vertical reference line and the anterior pelvic plane (defined by the line joining both anterior superior iliac spines and the pubic symphysis). In the supine position pelvic tilt was defined as the angle between a horizontal reference line and the anterior pelvic plane. Supine pelvic tilt was measured from computed tomography, Fig 2.Introduction
Methodology
The purpose of the study was to assess the safety of Intra-articular steroid hip injections (IASHI), prior to ipsilateral total hip arthroplasty (THA). We investigated whether there was an excess of infection in such a group 7–10 years after total hip arthroplasty. A database of 49 patients who had undergone IASHI followed by ipsilateral THA was reviewed.Aim
Method
Thermal damage to bone related to the exothermic polymerisation of bone cement (PMMA) remains a concern. A series of studies were conducted to examine PMMA bone interface during cemented arthroplasty. In vitro and in vivo temperature distributions were performed in the laboratory and human and animal surgery. In vivo (10 patients) measurements of cement temperature during cementing of BHR femoral prosthesis using thermocouples. Intra-operative measurement of cement temperature in BHR in the presence of femoral head cysts was examined in patients. The BHR femoral heads were sectioned to assess cement mantle as well as position of thermocouples. An additional study was performed in sheep with PMMA implanted into cancellous defects. Thermocouples were used to monitor temperature in the cement as well as adjacent bone. Histology and CT was used to assess any thermal damage. The exothermic reaction of PMMA during polymerization does indeed result in an increase in temperature at the interface with bone. The in vivo study recorded a maximum temperature of 49.12C for approximately three minutes in the cancellous bone underneath the BHR prosthesis. This exposure is probably not sufficient to cause significant injury to the femoral head. The maximum temperature of the cement on the surface of the bone was 54.12C, whereas the maximum recorded in the cement in the mixing bowl was 110.2C. In the presence of artificial cysts within the bone, however, temperatures generated within the larger cysts, and even at the bone-cement interface of these cysts, reached levels greater than those previously shown to be harmful to bone. This occurred in one case even in the 1 cc cyst. Routine histology revealed a fibrous layer at the cement bone interface in the sheep study. Fluorescent microscopy demonstrated bone label uptake adjacent to the defect site. Histology did not reveal thermal necrosis in the defects in terms of bony necrosis. CT data was used to measure the amount of PMMA placed into each defect. This analysis revealed a range of volumes that did not seem to influence the histology. The heat of cement polymerisation in resurfacing as performed in our study is not sufficient to cause necrosis. This may reflect the ability of the body to rapidly conduct heat away by acting as a heat sink. The temperature-conducting properties of the metal prosthesis are also likely to be important.
