Local antimicrobial therapy is an integral aspect of treating orthopaedic device related infection (ODRI), which is conventionally administered via polymethylmethacrylate (PMMA) bone cement. PMMA, however, is limited by a suboptimal antibiotic release profile and a lack of biodegradability.

In this study, we compare the efficacy of PMMA versus an antibioticloaded hydrogel in a single- stage revision for chronic methicillin-resistant Staphylococcus aureus (MRSA) ODRI in

sheep. Antibiofilm activity of the antibiotic combination (gentamicin and vancomycin) was determined in vitro. Swiss alpine sheep underwent a single-stage revision of a tibial intramedullary nail with MRSA infection. Local gentamicin and vancomycin therapy was delivered via hydrogel or PMMA (n = 5 per group), in conjunction with systemic antibiotic therapy. In vivo observations included: local antibiotic tissue concentration, renal and liver function tests, and quantitative microbiology on tissues and hardware post-mortem.

There was a nonsignificant reduction in biofilm with an increasing antibiotic concentration in vitro (p = 0.12), confirming the antibiotic tolerance of the MRSA biofilm. In the in vivo study, four out of five sheep from each treatment group were culture negative. Antibiotic delivery via hydrogel resulted in 10–100 times greater local concentrations for the first 2–3 days compared with PMMA and were comparable thereafter. Systemic concentrations of gentamicin were minimal or undetectable in both groups, while renal and liver function tests were within normal limits.

This study shows that a single-stage revision with hydrogel or PMMA is equally effective, although the hydrogel offers certain practical benefits over PMMA, which make it an attractive proposition for clinical use.

Introduction:

The risk for late periprosthetic fractures is higher in patients treated for a neck of femur fracture compared to those treated for osteoarthritis. It has been hypothesised that osteopenia and consequent decreased stiffness of the proximal femur are responsible for this. We investigated if a femoral component with a bigger body would increase the torque to failure in a biaxially loaded composite sawbone model.

Introduction:

In an attempt to reduce stress shielding in the proximal femur multiple new shorter stem design have become available. We investigated the load to fracture of a new polished tapered cemented short stem in comparison to the conventional polished tapered Exeter stem.

Introduction

The Exeter cemented polished tapered stem design was introduced into clinical practice in the early 1970's. [i] Design and cement visco-elastic properties define clinical results [ii]; a recent study by Carrington et al. reported the Exeter stem has 100% survivorship at 7 years. [iii] Exeter stems with offsets 37.5–56 mm have length 150 mm (shoulder to tip). Shorter stems, lengths 95–125 mm, exist in offsets 30–35.5 mm. The Australian National Joint Replacement Registry recently published that at 7 years the shorter stems are performing as well as longer stems on the registry [iv]. Clinical observation indicates in some cases of shorter, narrower femora that fully seating a 150 mm stem's rasp in the canal can be difficult, which may affect procedural efficiency. This study investigates the comparative risk of rasp distal contact for the Exeter 150 mm stem or a 125 mm stem.

Aim:

This prospective cohort study investigated whether the use of preoperative anticoagulants is an independent risk factor for the outcomes of surgical treatment of patients with a neck of femur fracture.

There has been much discussion and controversy in the media recently regarding metal toxicity following large head metal on metal (MoM) total hip replacement (THR). Patients have been reported as having hugely elevated levels of metal ions with, at times, devastating systemic, neurolgical and/or orthopaedic sequelae.

However, no direct correlation between metal ion level and severity of metallosis has yet been defined. Normative levels of metal ions in well functioning, non Cobalt-Chrome hips have also not been defined to date.

The Exeter total hip replacement contains no Cobalt-Chrome (Co-Cr) as it is made entirely from stainless steel. However, small levels of these metals may be present in the modular head of the prosthesis, and their effect on metal ion levels in the well functioning patient has not been investigated.

We proposed to define the “normal” levels of metal ions detected by blood test in 20 well functioning patients at a minimum 1 year post primary Exeter total hip replacement, where the patient had had only one joint replaced.

Presently, accepted normal levels of blood Chromium are 10–100 nmol/L and plasma Cobalt are 0–20 nmol/L. The UK Modern Humanities Research Association (MHRA) has suggested that levels of either Cobalt or Chromium above 7 ppb (equivalent to 135 nmol/L for Chromium and 120 nmol/L for Cobalt) may be significant. Below this level it is indicated that significant soft tissue reaction and tissue damage is less likely and the risk of implant failure is reduced.

Hips were a mixture of cemented and hybrid procedures performed by two experienced orthopaedic consultants. Seventy percent were female, with a mixture of head sizes used.

In our cohort, there were no cases where the blood Chromium levels were above the normal range, and in more than 70% of cases, levels were below recordable levels. There were also no cases of elevated plasma Cobalt levels, and in 35% of cases, levels were negligible.

We conclude that the implantation with an Exeter total hip replacement does not lead to elevation of blood metal ion levels.

Bleeding related wound complications including deep infection, superficial infection and haematoma cause significant morbidity in lower limb joint arthroplasty surgery. It has been observed anecdotally that patients requiring therapeutic anti-coagulation within the peri-operative period have higher rates of bleeding related complications and those requiring intravenous heparin particularly appear to do poorly.

The aim of this study is to investigate the relationship between post-operative bleeding and wound complications in the patient requiring therapeutic warfarin, plus or minus heparin, in total hip arthroplasty surgery.

This is a retrospective cohort study reviewing 1047 primary total hip replacements performed in a single centre over a five year period and comparing outcomes of the patients on warfarin (89) with a double-matched control group of patients not on warfarin (179). Outcomes included rates of deep infection, excessive wound ooze or haematoma, superficial infection, return to OT for washout and need for revision operation. The study group was then sub analysed comparing those on IV heparin plus oral warfarin, to those on warfarin alone.

The warfarin group had significantly higher risk of deep joint infection (9% vs 2.2% p= 0.023), haematoma/wound ooze (28% vs 4% p < 0.001) and superficial infection (13.5% vs 2.2% p < 0.001) compared to the control group. In the sub analysis of the study group, those on IV heparin had significantly higher risk of haematoma/wound ooze (44% vs 28% p= 0.023) than those on warfarin alone.

The requirement of therapeutic anti-coagulation in the peri-operative period is a tenuous balance between the complications of thrombo-embolic disease and bleeding-related morbidity. In the past, perhaps the full burden of bleeding related complications has not been appreciated, but now improved understanding will enable the both the surgeon and the patient to make more informed decisions regarding therapeutic anticoagulation in elective arthroplasty surgery.

Favourable long-term results have been reported with the standard Exeter cemented stem. We report our experience with a version for use in smaller femora, the Exeter 35.5 mm stem. Although, also a collarless polished taper, the stem is slimmer and 25 mm shorter than a standard stem.

Between August 1988 and August 2003, 192 primary hip arthroplasties were performed in 165 patients using the Exeter 35.5 mm stem. Clinical and operative data were collected prospectively. Clinical evaluation was by the Charnley, Harris and Oxford hip scores and radiographs were analysed post-operatively and at latest follow up.

The mean age at time of operation was 53 years (18 to 86), with 73 patients under the age of 50 years. The diagnosis was osteoarthritis in 91, hip dysplasia in 77, inflammatory arthritis in 18, septic arthritis of the hip in three, secondary to Perthes disease in two and avascular necrosis of the hip in one patient. The fate of every implant is known.

At a median follow-up of 8 years (5 to 19), survivorship with revision of the femoral stem for aseptic loosening as the endpoint was 100%. Fifteen cases (7.8%) underwent further surgery 11 for acetabular revision, one for stem fracture and three others.

Although, smaller than a standard Exeter Universal polished tapered cemented stem—with a shorter, slimmer taper—the performance of the Exeter 35.5 mm stem was equally good even in this young, diverse group of patients.

Impaction bone grafting (IBG) of the acetabulum in cemented primary total hip replacement is a useful technique in the management of acetabular deficiencies. It has the capacity to restore anatomy and bone stock with good long-term outcome. We present 125 consecutive cases of IBG with a cemented polyethylene component. All patients who received full IBG of the acetabulum in primary cemented Exeter total hip replacements and who underwent surgery between August 1995 and August 2003 were identified. All operative and follow-up data was collected prospectively and no patients were lost to follow-up. All patients underwent pre-operative and regular post-operative hip scores with the Harris, Oxford and the modified Charnley scoring systems. Data on indication, surgical technique, socket position and migration and revision was reviewed at a mean follow-up of 7.6 (range 5 to13.4) years.

Between August 1995 and August 2003, 113 patients (85 females) with an average age of 67.8 (range 22.9–99.2) years underwent 125 primary Exeter cemented total hip replacements with IBG of acetabular defects. Acetabular defects were classified according to the AAOS classification as cavitatory in 62 hips and as segmental, requiring application of a rim mesh prior to IBG, in 63 hips. Life tables were constructed demonstrating 86.4% survival of the acetabular component at 13.4 years with revision for any reason as the endpoint and 89.3% survival with revision for aseptic loosening as the endpoint. Of the seven patients who underwent revision for aseptic loosening, all had pre-operative segmental acetabular defects requiring application of a rim mesh. No patient who underwent IBG for a cavitatory defect required revision surgery for aseptic loosening. Survival of the Exeter cemented femoral component was 100% at 13.4 years with revision for aseptic loosening as the endpoint. There were 11 radiographic failures of the acetabular component, which have not been revised at latest review. One of these is symptomatic but not fit for revision surgery, two were asymptomatic at time of death and eight are asymptomatic but under review.

This is the largest series of IBG in the acetabulum in cemented primary THR. Our results suggest that the medium term survival of this technique is good, particularly when used for cavitatory defects. Although there were radiographic failures, these are largely asymptomatic and may not require revision.

The cement in cement technique for revision total hip arthroplasty (THA) has shown good results in selected cases. However, results of its use in the revision of hemiarthroplasty to THA has not been previously reported.

Between May 1994 and May 2007 28 (20 Thompson's and 8 Exeter bipolar) hip hemiarthroplasties were revised to THA in 28 patients using the cement in cement technique. All had an Exeter stem inserted at the time of revision. Clinical and operative data were collected prospectively. Clinical evaluation was by the Charnley, Harris and Oxford. Hip scores and radiographs were analysed post-operatively and at latest follow up.

The mean age at time of hemiarthroplasty revision was 80 (35 to 93) years. The reason for revision was acetabular erosion in 12 (43%), recurrent dislocation in eight (29%), aseptic stem loosening in four (14%), periprosthetic fracture in two (7%) and infection in a further two (7%) patients. No patient has been lost to follow up. Three patients died within three months of surgery. The mean follow up of the remainder was 50 (16 to 119) months. Survivorship with revision of the femoral stem for aseptic loosening as the endpoint was 100%. Three cases (11%) have since undergone further revision, one for recurrent dislocation, one for infection, and one for periprosthetic fracture.

The cement in cement technique can be successfully applied to revision of hip hemiarthroplasty to THA. It has a number of advantages in this elderly population including minimising bone loss, blood loss and operative time.

Removal of well-fixed cement at the time of revision THA for sepsis is time consuming and risks bone stock loss, femoral perforation or fracture. We report our experience of two-stage revision for infection in a series of cases in which we have retained well-fixed femoral cement.

All patients underwent two-stage revision for infection. At the first stage the prostheses and acetabular cement were removed but when the femoral cement mantle demonstrated good osseo-integration it was left in-situ. Following Girdlestone excision arthroplasty (GEA), patients received local antibiotics delivered by cement spacers, as well as systemic antibiotics. At the second stage the existing cement mantle was reamed, washed and dried and then a femoral component was cemented into the old mantle.

Sixteen patients (M:F 5:11) had at least three years follow-up (mean 80 months – range 43 to 91). One patient died of an unrelated cause at 53 months. Recurrence of infection was not suspected in this case. The mean time to first stage revision was 57 months (3 to 155). The mean time between first and second stages was nine months (1 to 35). Organisms were identified in 14 (87.5%) cases (5 Staphylococcus Aureas, 4 Group B Streptococcus, 2 Coagulase negative Staphylococcus, 2 Enterococcus Faecalis, 1 Escheria Coli). At second stage, five (31.2%) acetabulae were uncemented and 11 (68.8%) were cemented. There were two complications; one patient dislocated 41 days post-operatively and a second patient required an acetabular revision at 44 days for failure of fixation. No evidence of infection was found at re-revision. One patient (1/16, 7%) has been re-revised for recurrent infection. Currently no other patients are suspected of having a recurrence of infection (93%).

Retention of a well-fixed femoral cement mantle during two-stage revision for infection and subsequent cement-in-cement reconstruction appears safe with a success rate of 93%. Advantages include a shorter operating time, reduced loss of bone stock, improved component fixation and a technically easier second stage procedure.

Surgery for degenerative lumbar spondylolisthesis may entail both decompression and fusion. The knee-chest position facilitates the decompression, but fixation in this position risks fusion in kyphosis. This can be avoided by intra-operative re-positioning to the prone position. The aim of this study was to quantify the restoration of lordosis achieved by intra-operative repositioning and to assess the clinical and radiological outcome.

A total of forty consecutive patients with degenerative lumbar spondylolisthesis and stenosis were treated by posterior decompression and interbody fusion with pedicle screw fixation. The screw insertion, decompression and interbody grafting were performed with the patient in the knee-chest position. The patient was then re-positioned to the fully prone position for fusion. Sagittal plane angles were measured pre-, intra- and post-operatively. Clinical assessment was performed using SF-36 scores and visual analogue scores for back and leg pain.

The sagittal plane angle increased from median 16.0 degrees pre-operatively to 23.1 degrees post-operatively (p<0.01) and this was maintained at the last follow-up (mean 21 months). The SF-36 scores improved for 7 out of 8 domains and the physical score improved from 29% to 40% (p<0.05). The mean pain scores improved significantly from 7.5 to 3.8 for back pain and from 7.6 to 3.7 for leg pain (p<0.001).

Lumbar spondylolisthesis was found to be associated with a reduction of normal lumbar lordosis and the knee-chest position exacerbates this loss of lordosis. Intra-operative repositioning restored lordosis to greater than the pre-operative angle and was associated with a good clinical outcome.