Introduction

A metal ion study was undertaken in patients who had received an articular surface replacement. The design of these components is optimised in line with lubrication theory and produces low levels of wear in hip joint simulators.

Introduction: The DePuy ASRTM hip resurfacing system has been in clinical use since 2003. Its design features include a diametral clearance of 100–150 microns for optimal wear, and thinner components for improved bone preservation. Three of the six designer surgeons have pooled their clinical experience from three countries.

Methods: 1030 consecutive cases have been studied prospectively at annual intervals,. There were 379 females (average age 56.8 years, 16–71 years) and 579 males (average age 56.9 years, 21–75 years). 86% of patients had a primary diagnosis of Osteoarthritis. Follow up data has been collected by patient questionnaire, radiographs and clinical review. All retrieved specimens have been analysed

Results: The size of implants used varied from 46mm outside diameter acetabular component to 70mm

The Harris Hip Score improved from a pre-operative mean of 56.99 to 97.12 at the latest follow up, and 60% of patients were scored at 100. At the latest follow up, 91% of patients scored 6 or above on the UCLA activity score; indicating at least regular participation in moderate exercise.

There were no dislocations and no clinically evident DVT’s or PE’s

There have been 11 revisions for fracture (1.06%). Five of these were intra-operative fractures, and six of these took place in patients aged over 50years. Fractures occurred in 3.1% of patients 65 years or more and in 0.5% of patients under 65 years(P< 0.05). In addition there were three revisions for cup loosening (0.29%) all in women over 60 years, three for unexplained pain (0.29%), one for impingement and subluxation, and one for infection(0.1%) Five patients have died with the resurfacing in situ (0.51%), for unrelated causes.

The 3-year cumulative survival rate for all patients and all components was 97.4%. For 425 patients under 55 years the cumulative survival rate was 99.4%, aged under 65 years was 98.3%, and aged over 65 yrs was 94.8 %.

Discussion: Clinical results of this all-inclusive cohort of patients using a new resurfacing implant have been typical of other resurfacing systems and confirm excellent relief of pain and rapid return to an active lifestyle. The failures were evident within the first year after implantation, with no revisions occurring after 2 years. Cup loosening has been a rare complication associated with older females and only 0.29% of patients have undergone revision surgery for pain which could not be attributed to implant loosening or infection.

Introduction: Over 20,000 DePuy ASRTM hip resurfacing procedures have been performed since 2003, the implant design applying modern engineering and tribological principles to minimise metal-on-metal bearing wear. Enhanced fixation of both components, high-carbon cobalt-chromium alloy, reduced material thickness and small diametral clearance 100–150 microns are all supported by non-clinical testing. There are published reports of very low wear on hip joint simulators (Dowson D, et al. 2004 Dec;19(8 Suppl 3):124–30.), low wear on retrieval analysis (Morlock MM et al 1: Proc Inst Mech Eng [H]. 2006 Feb;220(2):333–44.) and excellent clinical results (Siebel T et al, Proc Inst Mech Eng [H]. 2006 Feb;220(2):345–53. We recently reported median whole blood chromium and cobalt ion levels of 1.56 ppb and 1.65 ppb at 24 months (Cobb AG et al, British Orthopaedic Association Congress 2007)

Methods: 1030 consecutive cases carried out by 3 of the surgeon-designers between July 2003 and May 2007 have been studied prospectively at annual intervals. 2 to 4 years follow-up data is available on 293 hips.

Results: There have been 11 revisions for fracture (1.06%), 6 in patients aged over 65 years(3.4%), 5 in patients aged up to 65 years (0.6%) (P< 0.001).

There have been 3 revisions for cup loosening (0.29%) and 3 for pain (0.29%). 5 patients have died (0.51%). There was one revision for infection and one for impingement.

Average Harris Hip Score rose from 57.0 to 97.1, and 60% of patients scored 100.

UCLA activity score was 6 or over in 91%, and the median score was 7.5.

All failures were evident by 12 months

The Cumulative Survival Rate at 3 years was 97.4%,, 99.5% for 55 years and under, 98.3% for under 65 years, and 94.2 % 65 years and over.

Discussion: The 2 to 4 year clinical follow-up of the latest generation of surface hip implants is satisfactory. Technical errors during implantation or patient selection accounted for most of the failures. The risk of failure between 12 months and 4 years is low.

Introduction: Analysis of the ages at the time of surgery of all patients undergoing primary hip and knee replacement in a UK District General Hospital setting over a period of 13 years

Method: Retrospective study of all cases of primary hip and knee replacements performed at our institution between 1993 and 2005.

Results: A total of 4703 patients had primary total joint replacement in this period. This includes 2591 hip replacements and 2112 knee replacements. The ratio of females to males was 2:1

The average age of primary hip replacement patient was 70 years. (male patients 68 years and 71 years in females.) Over the 13 year period, the average age of male patients was noted to decline steadily from 71 in 1993 to 66 in 2003. But the average age of female patients remained constant at around 71 years.

The number of patients below age 60 years undergoing hip replacement procedures was analysed. Only 8% of patients were under 60 years of age in 1993 rising to 23% in 2005. Between 2000 and 2005 this figure was at or above 20%.

Surface hip replacement was started at our hospital in 1999. The number of patients treated with surface hip replacement as a proportion of all primary hip procedures has increased to 32% in 2005. The average age of these patients was 57 years. The sex difference was approximately 1:1 as compared to 1:2 in total hip replacement.

The average age of primary knee replacement patients was 73 years, 72 yrs for males and 73 yrs for females. No change in average age was noted over the period. The proportion of patients under age of 60 years varied between 4 and 9%

Conclusion: The average age of male patients having primary hip replacement in the UK is declining and the proportion of young males undergoing hip replacement is increasing. Unless there has been a change in the incidence of osteoarthritis, these observations may reflect either a change in surgical selection criteria possibly associated with the success of surface replacement or else patients’ demand for early intervention. No changes have been observed in the age of patients undergoing knee replacement.

The purpose of the study was to investigate the outcome of re-operations performed at this district general hospital on total knee replacements over a period of nine and a half years: we also compare the reasons for re-operation as well as their timing.

Total knee replacements performed at this hospital and other centres requiring re-operation involving an open procedure were included in this study (total number =58). Patients were assessed both before and after re-operation using the knee society score. Data was recorded with respect to the type of original pros-thesis, reason for and time to re-operation as well as the nature of the re-operation procedure itself.

Pre- and post-operative knee society scores showed a mean improvement of 20 with respect to the function scores and 65 with respect to knee scores. 50% of re-operations were for aseptic loosening with a further 25% each for infection and instability.

In conclusion, re-operation for total knee replacement is shown to have had a satisfactory outcome in most cases. The results for revision surgery using a two stage procedure, in the treatment of infected total knee replacements, showed this to be very effective.

Aims: Firm bandaging of the knee following knee replacement may prevent bleeding into the joint by a tamponade effect, but the presence of a tight bandage around the knee may obstruct venous return and lead to thromboembolic complications. We have studied the pressure required, and then compared clinically the use of a compression bandaging with the use of either a drain, or a standard crepe bandage. Method: Transducers were used to measure the pressure achieved on the surface of the knee under different bandages, and within the knee following release of tourniquet. Three series of 50 patients have been compared: with compression bandaging from toes to mid-thigh, with crepe alone, or with suction drain and crepe. Results: The pressure within the joint at which tamponade occurs is 52–57 mm Hg. The pressure on the skin under a properly applied compression bandage is between 28 and 32 mmHg and this controls bleeding within the joint. Patients treated with compression bandaging recovered quicker from the operation had a shorter hospital stay and a greater range of ßexion on discharge. They had no swelling of the limb, rarely suffered a tense haemarthrosis and had fewer complications. Conclusions: The use of compression bandage incorporating the foot and calf following knee replacement surgery confers speciþc advantages over the use of crepe bandage alone.

Aims: A prospective study of the long term fixation of an all- polyethylene acetabular component with a 2mm rim for cement pressurisation, and methylmethac-rylate spacer beads for optimal cement mantle thickness. Methods: A consecutive series of 1348 hip arthroplasty patients aged between 23 and 94 (average 68 years) has been prospectively studied between 1993 and 2002. The cemented Ultima (De Puy) stem and cup were used via an anterolateral approach by 6 surgeons in a District General Hospital. Clinical and radiological assessment was at 0, 2, 5, 6, 7 and 8 years. Detailed assessment of the cup has been carried out to determine cases of clinical or radiological failure, quality of cement fixation to bone, and the profile of the cement mantle. Results: 875 patients have been followed up for a minimum of 2 years, 52 for a minimum of 8 years. The cumulative survival rate of the cup using revision for aseptic loosening as an endpoint at 8 years was 98% and using radiological evidence of loosening as an endpoint was 96%. There were no cases with less than 2 mm of cement mantle thickness and good quality bone cement interface was seen in all on the initial postoperative films indicating adequate pressurisation. Conclusions: The design of the Ultima polyethylene cup has been successful in achieving good cement pressurisation during implantation, an even cement mantle thickness, and clinical success rates which compare favourably with other cemented acetabular components.

Between 1989 and 1993 we implanted a matrix support prosthesis made of carbon fibre for the treatment of chronic painful articular defects of the patella in 27 patients. The mean period of follow-up was 33 months (11 to 54) with clinical and arthroscopic evaluation of the implant.

Overall, there were four excellent, three good, seven fair and 13 poor results. Nine patients subsequently had a patellectomy for persistent pain at a mean of 27 months after surgery (14 to 47). The mean visual analogue pain scores in those who retained their patella were 7.6 before operation and 5.5 at the time of the latest follow-up. Patient satisfaction for the entire group was 41%.

There appeared to be good incorporation of the prosthesis and a satisfactory ingrowth of fibrocartilage, but the poor results in 48% and low patient satisfaction discourage us from recommending the procedure for lesions of the articular cartilage of the patella. The consistent seeding of the joint with carbon-fibre debris and a histiocytic giant-cell reaction in the synovium are also a cause for concern.

We report the theoretical basis of a method to measure axial migration of femoral components of total hip replacements (THR). The use of the top of the greater trochanter and a lateral point on the collar of the stem, allowing for variations of up to 10 degrees rotation of the femur in any direction between successive radiographs, gave a maximum error of 0.37 mm. At a more realistic 5 degrees rotational variation, the error was only 0.13 mm. These data were confirmed in an experimental study using digitisation of points and special software. We also showed that the centre of the femoral head, the stem tip, and the lesser trochanter provided less accurate landmarks. In a second study we digitised a series of radiographs of 51 Charnley and 57 Stanmore THRs; the mean migration rates were found to be identical. We then studied 46 successful stems with a minimum follow-up of eight years and 46 stems which had failed by aseptic loosening at different times. At two years, the successful stems had migrated by a mean of 1.45 +/- 0.68 mm, but the failed cases had a mean migration of 4.32 +/- 2.58 mm (p < 0.0001). Of the successful cases 76% had migrated less than 2 mm, while in the failed group 84% had migrated more than 2 mm. For any particular case migration of more than 2.6 mm at two years had only a 5% chance of continuing success and would therefore merit special follow-up. Only 24% of the eventually successful stems showed migration at the stem-cement interface, but this had happened in every failed stem. We conclude that it would be possible to evaluate a new cemented design of femoral stem over a two-year period by the use of our method and to compare its performance against the reported known standard of the Charnley and Stanmore designs.

We report a high rate of failure of the Ring polyethylene cementless cup caused largely by granulomatous osteolysis. We have reviewed 126 prostheses inserted from 1986 to 1992 at from 11 to 90 months after surgery. There was radiological evidence of osteolytic granulomas adjacent to the external surface of the cup in 32%, appearing on average at three years from operation. In a subgroup of 59 prostheses followed for at least four years the incidence of such changes was 54%. A total of 27 cups (22%) have required revision, 21 for granulomatous loosening at an average follow-up of five years. In the retrieved prostheses there was obvious polyethylene abrasion and histological examination confirmed the presence of polyethylene wear debris. We found no significant correlation of osteolysis with cup size, although smaller cups were predominant among those having revision.

We report a case in which the popliteal artery was divided during upper tibial osteotomy performed with the knee in 90 degrees of flexion. This position is believed to allow it to fall safely back from the tibia, but we could find no published confirmation. We used duplex ultrasonography in ten healthy volunteers to measure the distance from the popliteal artery to the posterior surface of the tibia at various degrees of flexion of the knee. Our results showed that in 12 of 20 knees the popliteal artery was closer to the tibia in 90 degrees of knee flexion than in full extension. Surgeons performing upper tibial osteotomy should be aware that flexing the knee does not protect the popliteal artery from injury.

We describe 83 knees (69 patients) which had had patellectomy for anterior knee pain (52), patellofemoral osteoarthritis (25) or comminuted fractures (6) between 1942 and 1978. The patients were questioned about their symptoms and the function of the operated knee 14 to 50 years after operation. In the group with anterior knee pain, 76% achieved good results and were satisfied with the operation. Only 54% of the osteoarthritis group had satisfactory relief of pain and most had progressive deterioration of function. Sixteen patients who had had unilateral patellectomy were assessed by dynamometry, ultrasound and radiography. The average quadriceps muscle power was 60% of that on the normal side although two patients had stronger muscles in their operated than in their unoperated legs.

We measured joint position sense in the knee by a new method which tests the proprioceptive contribution of the joint capsule and ligaments. The leg was supported on a splint, and held in several positions of flexion. The subjects' perception of the position was recorded on a visual analogue model and compared with the actual angle of flexion. Eighty-one normal and 45 osteoarthritic knees were examined, as were 10 knees with semi-constrained and 11 with hinged joint replacements. All were assessed with and without an elastic bandage around the knee. There was a steady decline in joint position sense with age in subjects with normal knees. Those with osteoarthritic knees had impaired joint position sense at all ages (p less than 0.001). Knee replacement improved the joint position sense slightly (p less than 0.02); semi-constrained replacement had a greater effect than hinged replacement. The effect of an elastic bandage in subjects with poor position sense was dramatic, improving accuracy by 40% (p less than 0.001). It is proposed that reduced proprioception in elderly and osteoarthritic subjects may be responsible for initiation or advancement of degeneration of the knee.