In recent years articulating cement spacers have been used to treat infected knee arthroplasty. The aim has been to better maintain tissue planes and joint mobility thereby improving second stage re-implantation surgery. Two groups of patients treated for infected knee arthroplasty were reviewed. Twenty-six patients with articulating and forty patients with static antibiotic-impregnated methyl-methacrylate spacers were compared. The articulating spacers demonstrated easier surgical exposure at second stage and improved range of knee motion after re-implantation. There was no compromise in the rate of infection eradication with articulating spacers. Bone loss at revision was independent of spacer type.

To compare the results of patients treated with articulating versus static antibiotic-impregnated spacers for infected knee arthroplasty.

Articulating cement spacers facilitate re-implantation surgery by maintaining tissue planes and joint mobility without compromising joint stability or eradication rate of infection. Patients demonstrate better range of motion and less complications related to the extensor mechanism with the articulated spacer.

Antibiotic impregnated methyl-methacrylate spacers have become a mainstay in two-stage revision arthroplasty for sepsis. It is thought that articulating cement spacers facilitate prosthesis re-insertion by better maintaining tissue planes and joint mobility between stages.

In the articulating group fewer extensile exposure methods were required at second stage prosthesis reimplantation (19% vs 36 %). No tibial tuberosity osteotomies have been required since using the articulating spacer. The articulating group demonstrated a significantly improved range of flexion compared to the static group(106 vs 97 degrees- p=0.045) and had fewer patients with significant loss of extension or quadriceps lag. Eradication of infection was improved in the articulating group (92% vs 82%) but at shorter average follow-up. The need for augments and stabilized prostheses at revision surgery as a measure of bone loss was no different between the groups but was related to the number of prior surgical procedures.

Twenty-six patients treated with articulating spacers were compared to a matched consecutive group of forty patients treated with static spacers. Minimum follow-up was twelve months from second stage re-implantation (average twenty-two months articulating, forty months static)

Funding: No direct funding from any commercial source has been received for this study. The primary author’s fellowship position is partially funded by Smith and Nephew Richards Inc.

In recent years articulating cement spacers have been used to treat infected knee arthroplasty. The aim has been to better maintain tissue planes and joint mobility thereby improving second stage re-implantation surgery. Two groups of patients treated for infected knee arthroplasty were reviewed. Twenty-six patients with articulating and forty patients with static antibiotic-impregnated methyl-methacrylate spacers were compared. The articulating spacers demonstrated easier surgical exposure at second stage and improved range of knee motion after re-implantation. There was no compromise in the rate of infection eradication with articulating spacers. Bone loss at revision was independent of spacer type.

To compare the results of patients treated with articulating versus static antibiotic-impregnated spacers for infected knee arthroplasty.

Articulating cement spacers facilitate re-implantation surgery by maintaining tissue planes and joint mobility without compromising joint stability or eradication rate of infection. Patients demonstrate better range of motion and less complications related to the extensor mechanism with the articulated spacer.

Antibiotic impregnated methyl-methacrylate spacers have become a mainstay in two-stage revision arthroplasty for sepsis. It is thought that articulating cement spacers facilitate prosthesis re-insertion by better maintaining tissue planes and joint mobility between stages.

In the articulating group fewer extensile exposure methods were required at second stage prosthesis reimplantation (19% vs 36 %). No tibial tuberosity osteotomies have been required since using the articulating spacer. The articulating group demonstrated a significantly improved range of flexion compared to the static group(106 vs 97 degrees- p=0.045) and had fewer patients with significant loss of extension or quadriceps lag. Eradication of infection was improved in the articulating group (92% vs 82%) but at shorter average follow-up. The need for augments and stabilized prostheses at revision surgery as a measure of bone loss was no different between the groups but was related to the number of prior surgical procedures.

Twenty-six patients treated with articulating spacers were compared to a matched consecutive group of forty patients treated with static spacers. Minimum follow-up was twelve months from second stage re-implantation (average twenty-two months articulating, forty months static)

Funding: No direct funding from any commercial source has been received for this study. The primary author’s fellowship position is partially funded by Smith and Nephew Richards Inc.

Background: Reduced implant survivorship due to aseptic loosening has prompted research into alternative bearing materials. Simulator testing is useful, but clinical studies are the gold standard to evaluate the wear characteristics of new bearing materials. Net compression molded polyethylene has clinically reported improved wear characteristics over traditionally used RAM extruded UHMWPE 1,4,17,22. Machining of the compression molded acetabular component however may be detrimental to its wear properties 29. We report a 23–29% increase in 2D and 3D linear and volumetric wear in a cohort of patients in which machined compression molded acetabular components were used.

Methods: Ninety-two patients matched for gender, body mass index, primary pathology, Charnley grade, and length of follow up underwent uncemented total hip replacement using an identical acetabular and femoral implant. Group 1 (52 patients) had a RAM extruded polyethylene liner (GUR 4150 HP) and Group 2 (40 patients) had a machined compression molded polyethylene liner (Montell H 1900). UHMWPE sterilisation regimes were identical. Antero-posterior and lateral radiographs were analysed for acetabular wear using the Martell technique at a minimum follow up of five years and a maximum mean follow up of 87.4 months for group 1 (SD=8.7) and 84.9 months for group 2 (SD 7.7).

Results: Both 2D and 3D linear and volumetric wear rates in patients with a RAM extruded polyethylene acetabular component were 23–29% less compared to patients that received a machined compression molded acetabular liner. There was a statistical difference in age between to the two groups (P=0.007). Looking at acetabular wear in patients over 55 years, machined compression poly was still 16–31 % worse then RAM extruded polyethylene although statistical difference could not be reached for 3D linear and volumetric wear. The incidence of acetabular osteolysis on review of radiographs at maximum follow up was similar in both groups (group 1 =16.3% versus group 2 =15%).

Conclusions: Despite favourable reports of improved wear characteristics of net compression molded UHMWPE, this study shows a 23– 29% increase in 2D and 3D linear and volumetric wear in machined compression molded acetabular components. It appears that machining of compression molded polyethylene bar stock, to obtain the final component, is detrimental to the wear properties of the acetabular liner.

We identified five (2.3%) fractures of the stem in a series of 219 revision procedures using a cementless, cylindrical, extensively porous-coated, distally-fixed femoral stem. Factors relating to the patients, the implant and the operations were compared with those with intact stems. Finite-element analysis was performed on two of the fractured implants.

Factors associated with fracture of the stem were poor proximal bone support (type III–type IV; p = 0.001), a body mass index > 30; (p = 0.014), a smaller diameter of stem (< 13.5 mm; p = 0.007) and the use of an extended trochanteric osteotomy (ETO 4/5: p = 0.028). Finite-element analysis showed that the highest stresses on the stem occurred adjacent to the site of the fracture. The use of a strut graft wired over an extended trochanteric osteotomy in patients lacking proximal femoral cortical support decreased the stresses on the stem by 48%.

We recommend the use of a strut allograft in conjunction with an extended trochanteric osteotomy in patients with poor proximal femoral bone stock.

We carried out the Bernese periacetabular osteotomy for the treatment of 13 dysplastic hips in 11 skeletally mature patients with an underlying neurological diagnosis. Seven hips had flaccid paralysis and six were spastic. The mean age at the time of surgery was 23 years and the mean length of follow-up was 6.4 years. Preoperatively, 11 hips had pain and two had progressive subluxation.

Before operation the mean Tönnis angle was 33°, the mean centre-edge angle was −10°, and the mean extrusion index was 53%. Postoperatively, they were 8°, 25° and 15%, respectively. Pain was eliminated in 7 patients and reduced in four in those who had preoperative pain. One patient developed pain secondary to anterior impingement from excessive retroversion of the acetabulum. Four required a varus proximal femoral osteotomy at the time of the pelvic procedure and one a late varus proximal femoral osteotomy for progressive subluxation.

Before operation no patient had arthritis. At the most recent follow-up one had early arthritis of the hip (Tönnis grade I) and one had advanced arthritis (Tönnis grade III).

Our results suggest that the Bernese periacetabular osteotomy can be used successfully to treat neurogenic acetabular dysplasia in skeletally mature patients.