Aims

This study reports the ten-year wear rates, incidence of osteolysis, clinical outcomes, and complications of a multicentre randomized controlled trial comparing oxidized zirconium (OxZr) versus cobalt-chrome (CoCr) femoral heads with ultra-high molecular weight polyethylene (UHMWPE) and highly cross-linked polyethylene (XLPE) liners in total hip arthroplasty (THA).

This study reports the ten-year polyethylene liner wear rates, incidence of osteolysis, clinical outcomes and complications of a three-arm, multicentre randomised controlled trial comparing Cobalt-Chrome (CoCr) and Oxidised Zirconium (OxZr) femoral heads with ultra-high molecular weight polyethylene (UHMWPE) versus highly cross-linked polyethylene (XLPE) liners in total hip arthroplasty (THA).

Patients undergoing THA from four institutions were prospectively randomised into three groups. Group A received a CoCr femoral head and XLPE liner; Group B received an OxZr femoral head and XLPE liner; and Group C received an OxZr femoral head and UHMWPE liner. Blinded observers recorded predefined outcomes in 262 study patients at regular intervals for ten years following THA.

At ten years follow-up, increased linear wear rates were recorded in group C compared to group A (0.133 ± 0.21 mm/yr vs 0.031 ± 0.07 mm/yr respectively, p<0.001) and group B (0.133 ± 0.21 mm/yr vs 0.022 ± 0.05 mm/yr respectively, p<0.001). Patients in group C were associated with increased risk of osteolysis and aseptic loosening requiring revision surgery compared with group A (7/133 vs 0/133 respectively, p=0.007) and group B (7/133 vs 0/135 respectively, p=0.007). There was a non-significant trend towards increased liner wear rates in group A compared to group B (0.031 ± 0.07 mm/yr vs 0.022 ± 0.05 mm/yr respectively, p=0.128). All three groups were statistically comparable preoperatively and at ten years follow-up when measuring normalised Western Ontario and McMaster Universities Osteoarthritis Index(p=0.410), short-form-36 (p = 0.465 mental, p = 0.713 physical), and pain scale scores (p=0.451).

The use of UHMWPE was associated with progressively increased annual liner wear rates after THA. At ten years follow-up, this translated to UHMWPE leading to an increased incidence of osteolysis and aseptic loosening requiring revision THA, compared with XLPE. Femoral heads composed of OxZr were associated with a non-significant trend towards reduced wear rates compared to CoCr, but this did not translate to any differences in osteolysis, functional outcomes, or revision surgery between the two treatments groups.

This study reports the ten-year outcomes of a three-arm, multicentre randomised controlled trial comparing Cobalt-Chrome (CoCr) and Oxidised Zirconium (OxZr) femoral heads with ultra-high molecular weight polyethylene (UHMWPE) versus highly cross-linked polyethylene (XLPE) liners in total hip arthroplasty (THA).

Patients undergoing THA from four institutions were prospectively randomised into three groups. Group A received a CoCr femoral head and XLPE liner; Group B received an OxZr femoral head and XLPE liner; and Group C received an OxZr femoral head and UHMWPE liner. The outcomes of 262 study patients were analysed at ten years follow-up.

At ten years, increased linear wear rates were recorded in group C compared to group A (0.133 ± 0.21 mm/yr vs 0.031 ± 0.07 mm/yr respectively, p<0.001) and group B (0.133 ± 0.21 mm/yr vs 0.022 ± 0.05 mm/yr respectively, p<0.001). Patients in group C had increased risk of osteolysis and aseptic loosening requiring revision surgery compared with group A (7/133 vs 0/133 respectively, p=0.007) and group B (7/133 vs 0/135 respectively, p=0.007). There was a non- significant trend towards increased liner wear rates in group A compared to group B (0.031 ± 0.07 mm/yr vs 0.022 ± 0.05 mm/yr respectively, p=0.128). All three groups were statistically comparable preoperatively and at ten years follow-up from a clinical score perspective.

The use of UHMWPE was associated with progressively increased annual liner wear rates. At ten years follow-up, this translated to an increased incidence of osteolysis and aseptic loosening requiring revision, compared with XLPE. Femoral heads composed of OxZr were associated with a non-significant trend towards reduced wear rates compared to CoCr, but this did not translate to any differences in osteolysis, functional outcomes, or revision surgery between the two treatments groups.

Oxidised zirconium (OxZi) has been developed as an alternative bearing surface for femoral heads in total hip arthroplasty (THA). This study has investigated polyethylene wear, functional outcomes and complications, comparing OxZi and cobalt–chrome (CoCr) as part of a three-arm, multicentre randomised controlled trial. Patients undergoing THA from four institutions were prospectively randomised into three groups. Group A received a CoCr femoral head and highly cross-linked polyethylene (XLPE) liner; Group B received an OxZi femoral head and XLPE liner; Group C received an OxZi femoral head and ultra-high molecular weight polyethylene (UHMWPE) liner. At five years, 368 patients had no statistically significant differences in short-form-36 (p = 0.176 mental, p = 0.756 physical), Western Ontario and McMaster Universities Osteoarthritis Index (p = 0.847), pain scores (p = 0.458) or complications. The mean rate of linear wear was 0.028 mm/year (standard deviation (sd) 0.010) for Group A, 0.023 mm/year (sd 0.010) for Group B, and 0.09 mm/year (sd 0.045) for Group C. Penetration was significantly higher in the UHMWPE liner group compared with both XLPE liner groups (p < 0.001) but no significant difference was noted between CoCr and OxZi when articulating with XLPE (p = 0.153). In this, the largest randomised study of this bearing surface, it appears that using a XLPE acetabular liner is more important in reducing THA component wear than the choice of femoral head bearing, at mid-term follow-up. There is a non-significant trend towards lower wear, coupling OxZi rather than CoCr with XLPE but long-term analysis is required to see if this observation changes with time and becomes significant.

Cite this article: Bone Joint J 2015;97-B:883–9.

Introduction

In Total Hip Arthroplasty (THA), polyethylene wear reduction is key to implant longevity. Oxidized Zirconium (OxZi) unites properties of a ceramic bearing surface and metal head, producing less wear in comparison to standard Cobalt-Chromium (CoCr) when articulating with Cross-linked polyethylene (XLPE) in vitro. This study investigates in vivo polyethylene (PE) wear, outcomes and complications for these two bearing couples in patients at 5 year follow-up

Introduction: The bearing surface of total hip arthroplasty (THA) is a key factor in implant survivorship. Ceramic bearings have enhanced wear properties though are prone to fracture and thus Oxinium has been developed as an alternative. The aim of our study was to compare the its wear properties against cobalt-chrome which is currently the most widely used femoral head bearing surface in THA.

Methods: We prospectively randomized 270 consecutive patients undergoing THA at one institution into three groups: Groups I, II and III. Group I received a cobalt-chrome femoral head and cross-linked poly-ethylene (XLPE) liner; Group II received an oxinium femoral head and ultrahigh molecular weight polyeth-ylene (UHMWPE) liner; Group III received an oxinium femoral head and cross-linked polyethylene liner. 32 mm heads were used in all the cases. Patients were longitidunally followed up with clinical evaluation and standardised radiographs of the pelvis and hip. Using DICOMeasure software, we calculated the linear and volumetric wear rate for each group to determine if a difference existed.

Results: The demographics and comorbid conditions were similar between the groups. The survivorship of all components was 100% in all groups at 2 years. No patients were lost to follow-up. After the first 6 months of creep, the rate of linear wear over 2 years was 0.16mm for Group I, 0.10mm for Group II, and 0.06mm for Group III. ANOVA testing demonstrates statistical significance between the groups (P < 0.05).

Discussion and Conclusion: Our results demonstrate that the wear rate using 32mm Oxinium heads is significantly lower than that for cobalt-chrome heads and this effect is dramatically enhanced when used in combination with highly cross linked polyethylene.

Symptomatic isolated scaphotrapeziotrapezoid joint arthritis affects approximately 10% of the population. Involvement of the scaphotrapeziotrapezoid (STT) joint occurs in 15–30% of all degenerate wrists. Investigation of the technique of arthroscopic debridement of this joint was undertaken to assess the symptom relief achieved and record any resulting postoperative morbidity which limits the success of other techniques used for this condition.

Ten consecutive patients with persistent symptoms were assessed prospectively by a research nurse. Measurements of range of motion and grip strength were obtained before and after surgery. Visual analogue scores for pain and satisfaction levels were also recorded and any limitation to activities of daily living was noted. Assessment included clinical examination for local tenderness over the STT joint.

Good or excellent subjective results were achieved in nine patients at final review at an average of 36 (12–65) months after arthroscopic debridement. One patient graded the result as fair due to failure to achieve normal range of motion. All patients described significant reduction in visual analogue pain scores from an average of 86.5 to 14.1 points. The Green and O’Brien wrist scores improved from a mean of 63.2 to 91.2 during the same time frame. Eight of the patients were in employment and returned to work at 3 months post-surgery without the use of any external splints. The wrist scores were maintained in the five patients reviewed at least three years post-operation.

Conclusion: Arthroscopic debridement is simple, safe and effective when compared with other treatment modalities, achieving excellent pain relief and restoration in function in the short term in patients with isolated idiopathic STT arthritis. Longer term follow-up is no doubt required.

To investigate whether radioscapholunate arthrodesis [RSLA] can provide functional wrist movement with satisfactory pain relief. 19 patients with radio-carpal arthritis underwent RSLA. There were 3 diagnostic groups [post-traumatic osteoarthritis, rheumatoid arthritis and Kienbock’s disease].

The total flexion-extension range decreased. There was a decrease in pain post-operatively. Grip strength increased in Kienbock’s but fell-in patients with osteoarthritis. 95% of patients were satisfied with their result.

The normal ‘functional’ arc is 35 degrees. Pain was reduced in all of our patients, whilst maintaining the functional arc. With only one failure and no complications, we feel the procedure is safe and reliable.

Treatment Centres (TCs) specialise in common elective operations with long waiting lists. One of the concerns that has arisen with this enforced new healthcare model is the potential for suboptimal outcomes after joint arthroplasty. In order to decrease this risk we set in place a number of measures and have evaluated the outcome of the fist 100 total hip and total knee replacements undertaken at our TC and compared these to 100 consecutive controls undertaken concurrently by out hip and knee service. •Cases were only to be performed by consultant orthopaedic surgeons appointed to our trust – to the exclusion of visiting / sessional arrangements. •Same implants and care pathways as used within the rest of our department. •Weekly team arthroplasty rounds and planning sessions.

There was no significant difference in baseline demographics with both groups showing a slight female preponderance, and similar age ranges (35–88 av. 62; 42–86 av. 64). The treatment centres patients were heavier (78Kg range 48–111Kg; 72Kg range 43–101Kg). The TC group averaged 2.9 comorbidities per patient compared to 2.2. The average time to discharge was similar at 7.6 days . There was no significant difference in the improvement in Harris Hip or Knee Society Scores at a minimum 6 months follow-up. There were 2 infections in the TC group and one in the control group. There were 3 thromboembolic complications in each group and there was one unrelated death in each group. There was one dislocation and one fracture in the TC group and two fractures in the control group. Radiographic criteria including implant size, position, slope, offset, cementing and alignment were comparable in the two groups.

TC patients are not “fitter more predictable” patients and may have greater comorbidity. Our insistence on a local consultant led service and on identical standards to those of our non TC department have generated similar short term outcomes to those of non TC patients.

Introduction: Long term performance of total knee replacements is governed by wear of ultra-high molecular weight polyethylene (UHMWPE) which leads to aseptic loosening of the implant. Little has been done to reduce wear due to the femoral component properties in knee joint replacement. Scratching of the femoral component has been identified in retrieved knee replacements. Using a material that has a higher scratch resistance than current metals may reduce the rate of UHMWPE wear in knee replacements. In this study we investigated the effects of using an oxidized Zirconium femoral component has on wear in knee replacements.

Methods: Total knee replacements made of CoCr and oxidised zirconium were tested in a four station, six degrees of motion knee simulator for 4 million cycles. The surface roughness values (Ra, Rz and Sm) for the metal counterfaces was measured through the test. In addition gravimetric wear of the UHMWPE inserts was recorded. Scanning electron microscopy of the two counterface surfaces was performed to provide information on possible mechanisms involved in the wear process.

Results: The starting surface roughness for both CoCr and oxidised zirconium were similar (Ra=0.03m). Oxidised zirconium was significantly more scratch resistant than CoCr; Ra (mean average roughness) of 0.7m compared to 0.43m (p< < 0.01) at end of test, with similar differences in the other surface roughness parameters. This was accompanied by a 4 fold reduction in wear of UHMWPE 49.60mg to 12.48mg (p=0.02).

SEM analysis of the surfaces of the metals revealed large deep scratches of the CoCr implants which were aligned in the A-P sliding direction. Barium sulphate particles were seen embedded in the surface of the femoral component. Voids were seen in the surface of the cobalt chrome and particles of silicate polishing powder were seen in these voids. There was also evidence of scratches originating at these voids. By contrast oxidised zirconium, showed small amounts of superficial scratching with an intact surface and no evidence of third body particles.

Summary and conclusions: Oxidised zirconium leads to a reduction in wear of UHMWPE due to its increased resistance to third body wear. It has the potential to increase the longevity of total knee replacements by reducing wear of UHMWPE. Additionally, polishing powder used in the manufacture of cobalt chrome femoral components of knee joint replacements is a potential source of third body particles.