Introduction: Total hip replacements (THR) with the first generation metal-on-metal articulation were abandoned in 1970s in favour of metal-on-polyethylene articulation. Osteolysis due to polyethylene wear particles renewed the interest in metal-on-metal articulations. The second generation had improved clearance, metal hardness and reproducible surfaces. We describe the 10-year outcome of 63 THR with Metasul metal-on-metal articulation.

Methods: From 1995 to 1996, 86 patients (90 hips) underwent THR with Metasul articulation and cemented CF-30 femoral stem. Of these, 55 hips had a cemented Stuhmer-Weber-Allopro cup and 35 hips had an uncemented Allofit cup. Eleven patients (12 hips) died and five patients (6 hips) were not available for clinical evaluation. However all had been contacted and it was known that the hip was not painful and had not been revised. Nine patients were lost to follow up. Thirty nine hips in cemented group and 24 hips in uncemented group had clinical, radiological and Oxford hip score (OHS) at minimum of 10-years follow-up after the operation.

Results: The minimum length of follow up was 10-years with an average of 10.8 years. The average OHS at 10 years for the cemented group was 23 (range 12 – 42) and for the hybrid group was 20.3 (range 12 – 37). Five out of 63 (8%) hips had revision surgery. Two revisions (3%) were performed because of infection, 1 was revised (1.5%) because of unexplained pain and suspected metallosis and 2 were revised (3%) for suspected aseptic acetabular cup loosening.

Conclusion: In comparison with the outcome of first generation metal-on-metal bearing, the hips in our study had lower rate of revision due to acetabular wear and loosening. This is the first study to show that the Metasul articulation has good outcome over a 10-year period. The survivorship is 97% with aseptic loosening as the endpoint for revision surgery.

Obesity [Body Mass Index (BMI) > 30kg/m2] is seen in a growing percentage of patients seeking joint replacement surgery. Operations in obese patients take longer and present certain technical difficulties. Computer navigation improves consistency of prosthetic component alignment but increases operation time.

Our aims were

to compare tourniquet times of non-obese with obese patients having knee replacement using standard instruments or computer navigation and

A retrospective analysis of 232 total knee replacement (TKR) operations performed by a single knee surgeon over a three year period was carried out. Similar knee prostheses (Plus Orthopedics, UK) were used in all cases. Variables to be assessed were the operative technique (computer navigation assisted or standard instruments) and BMI of patients.

Of the 232 knees, 117 were performed using computer navigation and 115 with standard instruments. Each of the groups was subdivided as per BMI to differentiate obese patients (BMI > 30) from the non-obese. Tourniquet times of surgery were used for comparison amongst the subgroups.

There were 56 and 59 patients in the non-obese and obese subgroups respectively within the standard TKR group. The average tourniquet times for these were 79.3 and 86.3 minutes respectively. This was a significant difference (p=0.037). Correspondingly in the computer navigated group, there were 60 non-obese and 57 obese patients. Their tourniquet times were 105.4 and 100.5 minutes respectively. This difference was not significant (p=0.15)

The obese patients in each group were then studied separately and divided into three equally sized subgroups in chronological order. Each sub-group comprised 19 standard TKRs and 19 computer navigated TKRs. Tourniquet times of operations were compared within each sub-group. P values within the first subgroup showed a significant difference. There was no significant difference within the second and third subgroups.

We concluded that obesity significantly increased the operative time in the standard TKR group. However in computer navigated TKR there was no significant difference in operative time between non-obese and obese patients. As the surgeon acquired experience of computer navigation there was no difference in time taken for conventional and computer navigated TKR in obese patients. We hypothesize that in obese patients, computer assisted navigation helps the surgeon to overcome jig alignment uncertainty without any time penalty.

Hip resurfacing is a bone-conserving procedure with respect to proximal femoral resection, but there is debate in the literature as to whether the same holds true for the acetabulum. We have investigated whether the Birmingham hip resurfacing conserves acetabular bone.

Between 1998 and 2005, 500 Birmingham hip resurfacings were performed by two surgeons. Between 1996 and 2005 they undertook 700 primary hip replacements, with an uncemented acetabular component. These patients formed the clinical material to compare acetabular component sizing. The Birmingham hip resurfacing group comprised 350 hips in men and 150 hips in women. The uncemented total hip replacement group comprised 236 hips in men and 464 hips in women. Age- and gender-matched analysis of a cohort of patients for the sizes of the acetabular components required for the two types of replacement was also undertaken. Additionally, an analysis of the sizes of the components used by each surgeon was performed.

For age-matched women, the mean outside diameter of the Birmingham hip resurfacing acetabular components was 2.03 mm less than that of the acetabular components in the uncemented total hip replacements (p < 0.0001). In similarly matched men there was no significant difference (p = 0.77). A significant difference was also found between the size of acetabular components used by the two surgeons for Birmingham hip resurfacing for both men (p = 0.0015) and women (p = 0.001). In contrast, no significant difference was found between the size of acetabular components used by the two surgeons for uncemented total hip replacement in either men or women (p = 0.06 and p = 0.14, respectively). This suggests that variations in acetabular preparation also influence acetabular component size in hip resurfacing.

We audited the relationship between obesity and the age at which hip and knee replacement was undertaken at our centre. The database was analysed for age, the Oxford hip or knee score and the body mass index (BMI) at the time of surgery. In total, 1369 patients were studied, 1025 treated by hip replacement and 344 by knee replacement. The patients were divided into five groups based on their BMI (normal, overweight, moderately obese, severely obese and morbidly obese).

The difference in the mean Oxford score at surgery was not statistically significant between the groups (p > 0.05). For those undergoing hip replacement, the mean age of the morbidly obese patients was ten years less than that of those with a normal BMI. For those treated by knee replacement, the difference was 13 years. The age at surgery fell significantly for those with a BMI > 35 kg/m² for both hip and knee replacement (p > 0.05). This association was stronger for patients treated by knee than by hip replacement.

The effects of the method of fixation and interface conditions on the biomechanics of the femoral component of the Birmingham hip resurfacing arthroplasty were examined using a highly detailed three-dimensional computer model of the hip. Stresses and strains in the proximal femur were compared for the natural femur and for the femur resurfaced with the Birmingham hip resurfacing. A comparison of cemented versus uncemented fixation showed no advantage of either with regard to bone loading. When the Birmingham hip resurfacing femoral component was fixed to bone, proximal femoral stresses and strains were non-physiological. Bone resorption was predicted in the inferomedial and superolateral bone within the Birmingham hip resurfacing shell. Resorption was limited to the superolateral region when the stem was not fixed. The increased bone strain observed adjacent to the distal stem should stimulate an increase in bone density at that location. The remodelling of bone seen during revision of failed Birmingham hip resurfacing implants appears to be consistent with the predictions of our finite element analysis.

We describe the results at five years of a prospective study of a new tri-tapered polished, cannulated, cemented femoral stem implanted in 51 patients (54 hips) with osteoarthritis. The mean age and body mass index of the patients was 74 years and 27.9, respectively. Using the anterolateral approach, half of the stems were implanted by a consultant orthopaedic surgeon and half by six different registrars. There were three withdrawals from the study because of psychiatric illness, a deep infection and a recurrent dislocation. Five deaths occurred prior to five-year follow-up and one patient withdrew from clinical review.

In the remaining 51 hips the mean pre-operative Oxford hip score was 47 points which decreased to 19 points at five years (45 hips). Of the stems 49 (98%) were implanted within 1° of neutral in the femoral canal. The mean migration of the stem at five years was 1.9 mm and the survivorship for aseptic loosening was 100%. There was no significant difference in outcome between the consultant and registrar groups. At five years, the results were comparable with those of other polished, tapered, cemented stems. Long-term surveillance continues.

The Cambridge Cup has been designed to replace the horseshoe-shaped articular cartilage of the acetabulum and the underlying subchondral bone. It is intended to provide physiological loading with minimal resection of healthy bone.

The cup has been used in 50 women with displaced, subcapital fractures of the neck of the femur. In 24 cases, the cup was coated with hydroxyapatite. In 26, the coating was removed before implantation in order to simulate the effect of long-term resorption.

The mean Barthel index and the Charnley-modified Merle d’Aubigné scores recovered to their levels before fracture. We reviewed 30 women at two years, 21 were asymptomatic and nine reported minimal pain. The mean scores deteriorated slightly after five years reflecting the comorbidity of advancing age. Patients with the hydroxyapatite-coated components remained asymptomatic, with no wear or loosening. The uncoated components migrated after four years and three required revision. This trial shows good early results using a novel, hydroxyapatite-coated, physiological acetabular component.

We have used the Oxford hip score to monitor the progress of 1908 primary and 279 revision hip replacements undertaken since the start of 1995. Our review programme began in early 1999 and has generated 3900 assessments.

The mean pre-operative scores for primary and revision cases were 40.95 and 40.11, respectively. The mean annual score for primary replacement at between 12 and 84 months ranged between 20.60 and 22.57. A comparison of cross-sectional and longitudinal data showed no significant differences. All post-operative reviews showed a significant improvement (p ≤ 0.0001). The 50- to 60-year-old group scored significantly better than the patients over 80 years of age up to 48 months (p < 0.01). A subgroup of 826 National Health Service (NHS) and 397 private patients, treated by the senior author (2292 Oxford assessments), had a higher (i.e. worse) mean pre-operative score for the NHS patients (p ≤ 0.001). The private patients scored better than the NHS group up to 84 months (p < 0.05). Patients treated by a surgeon performing more than 100 replacements each year had a significantly better outcome up to five years than those operated on by surgeons performing fewer than 20 replacements each year. The age of the patients at the time of operation, and their pre-operative level of disability, have both been identified as affecting the long-term outcome. Awareness of the influence of these factors should assist surgeons to provide balanced advice.

Aim: Analyse the outcome of primary and revision total hip replacement using the Oxford hip score. To determine any variation in outcome when analysing for age of patient. In addition, to compare the outcome in the National Health Service compared to the Private hospital. Method: We have used the Oxford Hip score to monitor the progress of 1441 primary and 173 revision hip replacements (THR) undertaken since the start of 1995 whose hips have been replaced, at St Helier Hospital, Carshalton and St Anthony’s Hospital, Cheam, over the last seven years. Our review programme was started in early 1999 and has generated 2286 Oxford assessments.). A subgroup of 634 National Health Service (NHS) and 322 private patients (PP), treated by the senior author, has provided 1277 Oxford assessments. Results: Mean preoperative scores were 39.06 and 39.48 for primary and revision THR respectively. The mean annual scores, for primary THR, from 12 to 84 months declined to 21 points at 1 year, 21 at 2 years, 21 at 3 years, 20 at 4 years, 22 at 6 years and 21 at 7 years. Conclusion: All postoperative reviews show a significant improvement (p ≤0.0001). The 50–60 year old group scored significantly better than the over 80 year patients up to 48 months, (p< 0.01) The mean preoperative score for the NHS patients was significantly higher than the PPs (p< 0.001). The PPs scored significantly better than the NHS group up to 36 months (p< 0.01).

Aim: To develop an accurate and reproducible validated digital technique for the two-dimensional measurement of longitudinal femoral stem migration on AP radiographs.

Method: Eight patients who underwent total hip replacement, under the care of the senior author, were randomly selected. In each case, three radio-opaque marker beads had been implanted into the greater trochanteric region at surgery. Using a standardised x-ray protocol, three consecutive AP standing hip x-rays were taken of each patient on the same day. The plain radiographs were digitised, and the vertical bead to stem tip distance measured by two orthopaedic trainees using Scion Image ‘freeware’ software package and standard computer equipment. Every patient had three different measurements on each of their three consecutive x-rays. The vertical bead to stem tip distance was averaged over the three beads.

Results: Statistical analysis was performed and the repeatability coefficient between x-rays was 0.61 (confidence interval 0.46 to 0.78). The limits of agreement for inter observer error for average bead to stem distance were −0.15 to 0.39.

Conclusion: Our results demonstrate the efficacy of our system for analysis of femoral stem migration in everyday clinical practice. This technique does require implantation of marker beads and a standardised protocol for patient positioning for radiographs.

Aim: Hip resurfacing is a bone conserving procedure with respect to proximal femoral resection. For previous generations of conservative hip replacement, preservation of the natural femoral head diameter necessitated additional sacrifice of acetabular bone in order to accommodate a sufficiently thick polyethylene acetabular component. We have investigated whether the BHR offers a bone conserving procedure with respect to the acetabular bone stock.

Method: We reviewed 284 Birmingham resurfacing hip replacements (BHR), and 479, primary hip replacements, in which an uncemented acetabular component (THUA) was used. The BHR and THUA group had mean age at surgery of 55 and 65 years respectively. In 32 BHR’s and 21 THUA, pre-operative templating measurements were available for subsequent comparison with size of component implanted.

Results: Comparison of component sizes, for both implant types, confirmed bi-modal distribution according to patient gender. BHR cups, implanted by the first author, in females, were significantly smaller than those implanted, by the same author, in THUA,(p< 0.0001). Pre-operative templating overestimated component size for all groups but the difference was only significant in male BHR cases;(p=0.03). BHR cups implanted by the first author were significantly smaller than the second author, for both male (p= 0.0001) and female patients;(p< 0.001).

Conclusion: In females, BHR is bone a conserving procedure for femoral and acetabular components. In males, the procedure is not bone sacrificing when compared to THUA. Pre-operative templating can overestimate size of acetabular component that will be used for men. A significant difference was found between size of acetabular components used by two surgeons for BHR.

Introduction: The acetabular cup comprises a 3mm thick bearing surface of UHMPE, a 1.5mm backing of 30% carbon fibre reinforced polybutyleneterephthalate (CFRPBT). Young’s modulus, of CFRPBT layer is similar to natural subchondral bony plate. The cup deforms, when loaded, with the surrounding acetabular bone so that micro-motion at the bone-prosthesis interface is reduced. We measured BMD in the periacetabulum

Method: BMD was analysed for 2 years (n=11 females) with Mean Barthel Index at 2 years 19. Regions of interest were defined according to De-Lee and Charnley (ROI I-III) for the acetabulum. BMD during follow-up was compared with immediate post-operative values. Mean precision error (CV%) was 1.8±0.87%.

Results: By 2 years the mean BMD in HA cup was 0.73gms/cm2 representing a decrease of 7% and 0.78gms/cm2, which representing a 4% decrease with the non-HA cup. With the HA cup at 2 years we measured an increase in ROI I of 3% and a reduction in ROI II and III of 3% and 20% respectively. With the non-HA cup at 2 years we measured an increase in ROI II of 7% and a reduction in ROI I and III of 3% and 16%. There was a significant difference (p< 0.05) in the BMD changes measured in non-weight bearing zone III and one of the weight bearing zones (zone II).

Conclusion: Changes in BMD measured reflect a pattern of maximally reduced stress in zone III followed by zone II and least in the load bearing axis of the acetabulum zone I.

Aim: A prospective study was undertaken to define the pattern of bone remodelling using DXA following implantation of our polished, tri-tapered, collarless, cannulated cemented femoral component.

Method: Our stem was implanted in 20 primary THRs. Our subjects comprised 7 male and 13 female patients. At the time of surgery the mean age was 73 (range 65 to 131). The mean weight at surgery was 75.4kg (range 47kg to 131.8kg) with a mean BMI of 28(range 22 to 40). All patients had a pre operative diagnosis of osteoarthritis. All the hips were implanted via the anterolateral approach. Pre-operative and sequential post-operative DXA evaluations were undertaken at 3 weeks, 6 and 12 months.

Results: The mean precision error was 0.78%(range 0.8–3.4% depending on region of interest). Statistical analysis revealed a significant increase in BMD measured in zones 1,2,4,5,6 (p< 0.05). In zones 3 and 7, the increase in BMD was not significant (p> 0.05). The real percentage increase in BMD at 12 months was 43% in zone 1, 20% in zone 2, 8% in zone 3, 31% in zone 4, 12% in zone 5, 24% in zone 6 and 7% in zone 7.

Conclusion: Peri-prosthetic bone remodelling has been observed within one year following total hip replacement (THR), which has been demonstrated by an increase in BMD in all zones. The implantation of our tri-tapered cannulated cemented femoral component, thus provides favourable proximal femoral loading at 12 months. Additional studies will determine whether stabilization of this bone turnover continues in the long term.

Aim: Analyse the outcome of primary and revision total hip replacement using the Oxford hip score. To determine any variation in outcome when analysing for age of patient. In addition, to compare the outcome in the National Health Service compared to the Private hospital.

Method: We have used the Oxford Hip score to monitor the progress of 1441 primary and 173 revision hip replacements (THR) undertaken since the start of 1995 whose hips have been replaced, at St Helier Hospital, Carshalton and St Anthony’s Hospital, Cheam, over the last seven years. Our review programme was started in early 1999 and has generated 2286 Oxford assessments. ). A subgroup of 634 National Health Service (NHS) and 322 private patients (PP), treated by the senior author, has provided 1277 Oxford assessments.

Results: Mean pre-operative scores were 39.06 and 39.48 for primary and revision THR respectively. The mean annual scores, for primary THR, from 12 to 84 months declined to 21 points at 1 year, 21 at 2 years, 21 at 3 years, 20 at 4 years, 22 at 6 years and 21 at 7 years.

Conclusion: All postoperative reviews show a significant improvement (p≤0.0001). The 50–60 year old group scored significantly better than the over 80 year patients up to 48 months, (p< 0.01) The mean pre-operative score for the NHS patients was significantly higher than the PPs (p< 0.001). The PPs scored significantly better than the NHS group up to 36 months (p< 0.01).