Introduction: Osteolysis is a recognised complication in both cemented and cementless arthroplasty. This may be caused by macrophage mediated reaction to small particulate polyethylene debris. The effective joint space describes the area where polyethylene particles may travel, such as through holes in the cup, to cause a local osteolytic process.

Methods: Twenty four cases of osteolysis (in twenty three patients) requiring revision were identified from patients on whom we had performed the primary arthroplasty. These cases were compared to an overall group of 560 primary hip arthroplasty cases performed during the same time and with the same implants.

Results: The 24 index cases were revised for osteolysis. This represents 4.3% of the total group in this series of implants. Secondary loosening of the acetabular component was present in 7/24 with 13/24 cups being well fixed at the time of revision. All the cups with secondary loosening had evidence of bone ingrowth & had been undermined by the osteolytic process. In 4 cases, either a pelvic fracture or pelvic dissociation had occurred through an osteolytic lesion. In 21 cases femoral stems were revised, but none of these were loose, and none had significant osteolysis around the stems.

The average time from primary procedure to revision was 72 months. The osteolytic group was younger than the overall group at the time of index surgery (53 years vs 63 years, p< 0.0001). There were 16 females and 7 males (p = 0.06). The osteolytic group were also less likely to have an initial diagnosis of primary osteoarthritis than the control group (p=0.05). Other diagnoses in the osteolytic group included dysplasia, previous trauma and inflammatory arthropathy.

Acetabular liner thickness was assessed for all patients. The osteolytic group had a significantly higher proportion of cases with polyethylene thickness of less than 7mm (p < 0.005), and less than 6mm (p < 0.0001). There was no difference in the mean height and weight of the two groups.

Conclusion: Osteolysis is multifactorial and facilitated by screw holes in the acetabular shell that increase the “effective joint space.” Younger females with small ace-tabular components and thin polyethylene are most at risk. Alternate bearing surfaces or acetabular components without holes may alleviate this problem. These cases represent our experience with osteolytic lesions within the acetabulum requiring revision. There were no cases of cup loosening in our overall group other than the 7/24 that had been undermined by the osteolytic process. Revision to ceramic on ceramic bearing implants is our preferred method of treating this problem.

Aim: To calculate the incidence and timing of metal failure in endoprostheses used for bone tumour reconstructions and to analyse the mode of failure.

Methods: A retrospective analysis was performed on 468 endoprostheses with an average follow-up of 50 months. The explanted prostheses were studied to determine the mode of failure and the design and material features that might have contributed to the failure.

Results: There were 18 mechanical failures of metal. A total of 19 cases were revised for loosening one of which was noted to have a metal fracture pending at the time of the revision. There were three cases of failure of the coupling between components of modular systems. All of the remaining cases (16) were in the lower limb and these failed by fracture of the metal. The fractures occurred at an average of 92 months. The majority of the fractures that were seen were simple fatigue fractures but in three cases other types of failure were also involved. There were no fatigue fractures in forged cobalt chrome components. Fatigue fracture of the cast cobalt chrome implants could always be attributed to a local stress riser or a local area of high stress due to features of the design. Fatigue fractures of titanium implants were often related to notching.

Discussion: The large skeletal defects left by resection of bone tumours can often be reconstructed with endo-prostheses. The mechanical demands on these implants are great resulting in a relatively high incidence of metal failure. Improvements in design and materials can minimise these failures.

Introduction: Hip arthroplasty for dysplasia of the hip provides a challenge to all hip surgeons. The choice of prosthesis used depends on the severity of the deformity, and the challenge of acetabular reconstruction. We report a review of 105 of our cases operated since 1992 with a minimum two-year follow-up.

Methods: The data in this study has been collected and entered prospectively since 1992 on an arthroplasty database. A total of 105 cases were identified and reviewed. The indication for surgery was painful hip osteoarthritis secondary to dysplasia. All patients were reconstructed with some attempt at restoration of the hip centre, and without femoral osteotomy.

Results: There were 96 patients (10 bilateral), 66 females and 29 males whose mean age at surgery was 53 years (23 to 97 years). The mean follow-up period was 59 months (27 to 107 months). The hip was exposed via a posterior approach in 98% of cases. The majority (94%) of cases had no previous surgery. Depending on the degree of dysplasia either an ABG or S-ROM prosthesis was used.

There were 78 Crowe I & II, and 18 Crowe III & IV hips. The more dysplastic hips required the versatility of the SROM stems to avoid excessive lengthening or femoral osteotomy. These cases also had significantly more inferior reconstruction of the hip centre, and medialisation of the hip centre.

Complications occurred in 8/106 (8%) of cases, the mean time to occurrence being 25 months. The majority were dislocations 7 (7%). There were no sciatic nerve palsies. Revision was required for 5 cups and 1 stem. Clinical evaluation showed all patients were living at home and 85% had no activity restrictions. Mean Harris Hip Score was 92/100. None or mild thigh pain only was reported in 90% of cases. In 98% of cases patients were satisfied with their outcome. Radiographic evaluation showed stem ingrowth occurred in all cases. Minor osteolysis was apparent in 6% of cases. Spot welds were identified in 76% of cases. One case demonstrated pedestal formation.

Conclusion: Reconstructing hip joint mechanics is a challenge in the dysplastic hip. The use of different prostheses for the varying severity in dysplasia has been an effective approach to optimise hip mechanics. Our results using this approach with cementless implants has given excellent short term clinical and radiographic results.

Aim: To review our experience and results of the use of the ABG cementless femoral stem in younger patients; less than 50 years at the time of surgery.

Methods: A series of 82 primary hip arthroplasty cases in patients under the age of 50 years were reviewed. All cases were assessed using standard clinical and radiographic scoring systems.

Results: There were 82 arthroplasties performed in 72 patients. The mean age at surgery was 41 years (22 to 49 years). Diagnoses included primary osteoarthritis (44%), secondary osteoarthritis (42%), and inflammatory arthropathy (13%). There was one femoral peri-prosthetic fracture occurring at 69 months after surgery, associated with a large trochanteric granuloma and ace-tabular wear. There were four dislocations (4.9%). One stem has been revised, for dislocation two weeks after surgery. One other ingrown stem was removed at the time of acetabular revision for osteolysis. A total of 10 patients (14%) has required revision for osteolysis and wear in this group. At mean follow up of 72 months (37 to 109 months), average Harris Hip Score was 91/100, with 90% of patients having a good or excellent result. No stems were found to be loose on radiographic evaluation.

Conclusions: This anatomic, hydroxyapatite coated femoral stem provided excellent initial stability and reliable bone in-growth. The fixation appeared to be durable over this follow-up period. This group of young patients had a high polyethylene wear rate, as expected in high demand individuals, and higher dislocation rate than our overall experience with this implant and surgical approach.