Paradoxical cerebral embolism is seen in 50–60% of patients following hip and knee arthroplasty surgery. It is responsible for post-operative symptoms like confusion and cerebral ischemic episodes. Embolism is less common with the use of uncemented implants. No study has looked into incidence of cerebral emboli in hip resurfacing.

We undertook a prospective randomised study to look at the incidence of cranial emboli in hip resurfacing. Patients were randomized to receive either uncemented or cemented femoral component. An arm of the study included evaluation of the effects of femoral venting by randomising patients to ‘venting’ or ‘no venting’ of proximal femur intra-operatively. The operations were performed by a single surgeon using a uniform surgical technique. Transcranial Doppler device was used to quantify the occurrence and distribution of cerebral microemboli. Emboli counts were recorded continuously and were correlated any major procedural event.

Eight patients (5 vented, 3 unvented) underwent cemented resurfacing and 7 patients (4 vented, 3 unvented) had cementless resurfacing. There was no difference between the two groups for age, gender, weight, or ASA status. Peri-operatively both groups were similar for vital observations (heart rate, temperature, blood pressure), haemoglobin change, mini – mental score at day 1 and 2, and oxygen saturation at day 1 and 3.

The mean number of significant emboli in the cemented group was 8.1 and in the cementless group was 1.7 (significant, p=0.009). Venting did not influence rate of emboli however, venting was independently associated with significantly higher drainage (mean 604mls compared to 335mls without venting, p=0.018). There was no significant difference in post-operative haemoglobin or number of units transfused.

Cranial emboli occur commonly after hip resurfacing. Their incidence is significantly reduced by the use of uncemented femoral component, however venting of proximal femur doesnot appear to make any difference.

Introduction: Recurrent dislocation is a significant problem after total hip replacement. Aetiology is multifactorial and treatment should address the reason for dislocation. The use of a constrained tripolar liner is an option in the surgical treatment of dislocation.

Methods: A retrospective review was carried out of patients who have undergone revision hip surgery and had a constrained liner cemented into the acetabulum. Patients were identified from a computer database. All patients had a constrained liner cemented onto a satisfactory pre-existing cement mantle, cemented into a reconstruction ring, or cemented into a well fixed cementless shell. The Osteonics Tripolar Liner was used in all cases and the outer aspect of the tripolar liner was prepared with a burr to create grooves and thus improve cement interlock. Data collected included demographics, reason for revision, components used, re-revision rate, outcome and survival.

Results: There were 58 cases identified where a cemented constrained liner was inserted at revision hip surgery. Average age at time of surgery was 77years (range 40–94). Reason for use of a constrained liner was recurrent dislocation in over 95% of cases. There were 9 patients who died with less than 2 years follow-up; they were excluded, leaving a study group of 49 cases. Average duration of follow-up was 46months (range 24–76).

There have been 4 infections, one of which required removal of prostheses and 2 stage revision. There was one case of fall post-operatively and fracture of the contra-lateral femoral neck. There have been 3 implant failures requiring re-revision. All failures were due to disarticulation of the liner, 2 of which occurred in the same patient on separate occasions. There have been no revisions for loosening, and there have been no cases of failure at the bone-cement interface or at the cement-cement interface with the cement-in-cement technique. Overall survival of the cemented constrained liner was 91.8% at average 3.8years.

Conclusion: This study demonstrates that a cemented constrained tripolar liner is a viable option in revision hip surgery, particularly in the treatment of recurrent dislocation.

Work carried out by Bennett [1], identified a link between patient gait pattern and total hip prothesis wear rate. This study found that the shape of the patient gait pattern (as quantified by aspect ratio) and sliding distance of the movement loci were found to have an improved positive correlation with wear rate compared to the factors of activity and patient weight. The distribution of theoretical shear stresses at selected points on the acetabular cup suggests that orientation of the polymer chains may occur. Wang et al, 1997 [2] has shown that failure of the UHMWPE wear surfaces occurs in the form of transverse rupture between oriented molecules.

This work investigates the hypothesis that the gait pattern of pre-revision THR patients has an effect on the wear, surface characteristics and material properties of the artificial hip joint, in particular the degradation of chemical and mechanical properties of the UHMWPE acetabular socket. Gait analysis is performed on patients prior to revision of a primary THR, with the retrieved socket used for subsequent analysis.

Chemical and mechanical analysis of a large number of retrieved UHMWPE acetabular sockets has shown clear structural changes, which are dependent on the length on time in-vivo. Increasing the length of time in-vivo between 2 and 20 years results in an increase in the percentage crystallinity of the UHMWPE of 12.7 %. A positive linear correlation (R2 = 0.765) between percentage crystallinity and number of years in-vivo is shown. This suggests recrystallisation of the polymer at a constant rate over time. This partial recrystallisation of the amorphous region correlates with degradation in the mechanical properties of the material. This pilot study aims to assess the effect of patient gait pattern on the chemical and mechanical degradation of UHMWPE, which will ultimately affect the clinical performance of the prothesis.

Introduction: The Spotorno cementless femoral stem relies on proximal press-fit at time of surgery and subsequent osseointegration for long-term fixation. The aim of the study is to assess the long-term survivorship and clinical outcome of the Spotorno stem used in primary hip replacement surgery in younger patients.

Materials and Methods: 74 patients were identified who had undergone 90 THRs using the Spotorno CLS stem between January 1987 and May 1992. There was variation in the acetabular components used. 5 patients (6 hips) were lost to follow-up, leaving a study group of 84 hips. The patients were assessed using the Harris Hip Score and the Oxford Hip Score.

Results: Mean age at operation was 40.1years (range 23–65years). Commonest diagnoses were primary osteoarthritis, developmental dysplasia of the hip and rheumatoid arthritis. Mean duration of follow-up was 12.25 years (range 8½ – 15yrs 3months). At most recent follow-up, the mean Oxford Hip Score was 23.8 and mean Harris Hip Score was 81. Taking revision for any cause as an end point, 19 hips from the initial group of 84 had undergone some form of revision surgery at most recent review. 15 of the 19 hips that failed had aseptic loosening of the acetabular component, which was the Mecring component, and underwent revision of acetabulum only. Four stems were revised, 2 for loosening and 2 for infection. 80 out of 84 of stems originally implanted remained intact at most recent review, which represents a stem survivorship of 95.2% at mean 12.25yrs follow-up when used in young patients.

Conclusion: Our findings indicate excellent long-term survival of this titanium alloy stem when used in patients under 65years. We attribute this to stem design and the principle of proximal press-fit fixation. Careful consideration must be given to acetabular component selection in cementless total hip arthroplasty.