Current concepts in osteolysis.

The most frequent cause of failure after total hip replacement in all reported arthroplasty registries is peri-prosthetic osteolysis. Osteolysis is an active biological process initiated in response to wear debris. The eventual response to this process is the activation of macrophages and loss of bone. Activation of macrophages initiates a complex biological cascade resulting in the final common pathway of an increase in osteolytic activity. The biological initiators, mechanisms for and regulation of this process are beginning to be understood. This article explores current concepts in the causes of, and underlying biological mechanism resulting in peri-prosthetic osteolysis, reviewing the current basic science and clinical literature surrounding the topic.

The clinical and radiological outcomes of the LISS plate for distal femoral fractures: a systematic review.

PURPOSE: The purpose of this systematic review was to assess the literature evaluating the clinical and radiological outcomes following less invasive surgical stabilisation system (LISS) fixation of distal femoral fractures (AO 32/33). METHODS: A review of EMBASE, Medline, CINAHL and AMED from their inception to November 2008, sources of grey literature and a pertinent hand search of specialist orthopaedic journals was undertaken. RESULTS: Twenty-one studies assessing 663 patients with 694 fractures were reviewed. The findings suggest that the LISS system may be an appropriate fixation method for the management of distal femoral fractures. However, there remains a high incidence of loss of reduction (n=134; 19%), delayed or non-union (n=40; 6%) and implant failure (n=38; 5%). On analysis, such complications were largely confined to articles published before 2005, therefore during the infancy of the widespread clinical application of this trauma system. On critical appraisal, the evidence-base remains limited by recruiting small, under-powered sample sizes and poorly accounting for confounding variables such as osteoporosis, diabetes, multi-trauma and fracture classification. CONCLUSION: Further study is required to assess the outcomes of LISS fixation in specific patient populations, and to compare the outcome of this fixation method to condylar plates and intrameduallary devices, to determine the optimal management strategy for this complex patient group.

Revision total hip replacement using cemented collarless double-taper femoral components.

We investigated 219 revisions of total hip replacement (THR) in 211 patients using a collarless double-taper cemented femoral component. The mean age of the patients was 72 years (30 to 90). The 137 long and 82 standard length stems were analysed separately. The mean follow-up was six years (2 to 18), and no patient was lost to follow-up. Survival of the long stems to re-revision for aseptic loosening at nine years was 98% (95% confidence interval (CI) 94 to 100), and for the standard stems was 93% (95% CI 85 to 100). At five years, one long stem was definitely loose radiologically and one standard stem was probably loose. Pre-operative femoral bone deficiency did not influence the results for the long stems, and corrective femoral osteotomy was avoided, as were significant subsidence, major stress shielding and persistent thigh pain. Because of these reliable results, cemented long collarless double-taper femoral components are recommended for routine revision THR in older patients.

Assessment of reproducibility and accuracy in templating hybrid total hip arthroplasty using digital radiographs.

In 20 patients undergoing hybrid total hip arthroplasty, the reproducibility and accuracy of templating using digital radiographs were assessed. Digital images were manipulated using either a ten-pence coin as a marker to scale for magnification, or two digital-line methods using computer software. On-screen images were templated with standard acetate templates and compared with templating performed on hard-copy digital prints. The digital-line methods were the least reliable and accuracy of sizing compared with the inserted prostheses varied between -1.6% and +10.2%. The hard-copy radiographs showed better reproducibility than the ten-pence coin method, but were less accurate with 3.7% undersizing. The ten-pence coin method was the most accurate, with no significant differences for offset or acetabulum, and undersizing of only 0.9%. On-screen templating of digital radiographs with standard acetate templates is accurate and reproducible if a radiopaque marker such as a ten-pence coin is included when the original radiograph is taken.

Femoral neck-shaft angle in extra-capsular proximal femoral fracture fixation; does it make a TAD of difference?

The effect of femoral neck-shaft angle and implant type on the accuracy of lag screw placement in extra-capsular proximal femoral fracture fixation was investigated. Radiographs of all extra-capsular proximal femoral fractures seen in one unit over 18 months were reviewed. Of 399 cases, 307 (237 female, 70 male) were included in the study as they had no contra-lateral proximal femoral metal work. Femoral neck-shaft angle (NSA) of the uninjured hip and magnification adjusted tip-apex distance (TAD) of femoral head lag screw were measured. Type of fixation implant was 135 degrees classic hip screw (CHS) (n=144) or 130 degrees intra-medullary hip screw (IMHS) (n=163). Mean contra-lateral NSA was 130.2 degrees (112.9--148 degrees ) and 64 patients (58 female, 6 male) had a NSA <125 degrees . Mean adjusted TAD was 18.7 mm (5.8--43.8mm) and 88.9% of cases had a TAD of less than 25 mm. TAD values were significantly greater using an IMHS if NSA was <125 degrees than if NSA was >125 degrees (p=0.028). This was not the case with the CHS. The use of the 130 degrees -IMHS in patients with a NSA <125 degrees leads to poorer lag screw placement than if NSA >125 degrees and caution is advocated when using this device in such cases.

A new approach for plate fixation of midshaft clavicular fractures.

The majority of midshaft clavicle fractures unite uneventfully. Although the indications for operative intervention are limited and reported complication rates high, there are circumstances in which surgery is required. We describe a new, infraclavicular surgical approach to the clavicle used in a series of 89 patients over 9 years. Average time to union was 13.5 weeks. There was one case of deep infection and one of non-union, both of which resolved with further treatment. These results compare very favourably with previously published series and we submit that this operative approach allows safe management of an otherwise potentially hazardous procedure.

Bone loss at hip resurfacing: A comparison with total hip arthroplasty.

Resurfacing arthroplasty of the hip has been advocated as a bone-conserving procedure although concerns have been raised as to whether this is truly the case. We therefore compared bone loss during hip resurfacing with bone loss at total hip arthroplasty under controlled conditions using dry pelvic and femoral Sawbones (DePuy, Leeds, UK). Ten sets of femoral and pelvic Sawbones were included in the study. Five sets were prepared for implantation of a hybrid total hip arthroplasty and five sets were prepared for insertion of hip resurfacing components. The Sawbones were weighed before and after preparation and the amount of dry bone loss was determined. During preparation of the femur for a resurfacing arthroplasty we resected 51.4% less Sawbone than for a total hip arthroplasty (mean 12.3g vs 25.3g, p<0.001). More bone (311.1%) was removed, however, during acetabular preparation for a resurfacing arthroplasty than for a total hip arthroplasty (mean 5.6g vs 1.8g, p<0.001). The total amount of Sawbone removed was 33.9% less for a resurfacing arthroplasty compared with a total hip arthroplasty (mean 17.9g vs 27.1g, p=0.001). We conclude that although reduced resection of femoral bone may be an advantage of hip resurfacing arthroplasty, the increased amount of bone that is removed from the acetabulum may prove problematic should patients require future revision surgery. (Hip International 2005; 15: 195-8).

Endometrial cancer metastasis presenting as a grossly swollen toe.

Metastasis to the peripheral skeleton, especially in the face of low stage disease, is rare. This report describes the case of a 77-year-old lady with stage IC disease who underwent curative total abdominal hysterectomy and bilateral salpingo-oopherectomy 2 years prior to presenting with a painless gigantism of her fourth toe. A histologic diagnosis of dedifferentiated endometrial metastasis with sarcomatous differentiation was made following amputation of the toe. Osseous metastasis to bone is discussed in the context of endometrial carcinoma and the literature reviewed. This paper reports the first case of endometrial carcinoma metastasis presenting as gross swelling of a toe.

Endotoxin contamination of particles produces misleading inflammatory cytokine responses from macrophages in vitro.

Particulate prosthetic materials are often studied by adding them to monocytic cells in vitro and measuring the release of cytokines as an indicator of their inflammatory potential. Endotoxin is known to be a contaminant of particle preparations and also stimulates the release of cytokines. It is usual to use a proprietary endotoxin test to avoid erroneous results. Four different formulations of cement were found to be free from endotoxin using standard, gel-clot tests but stimulated different levels of release of cytokines from macrophages. These differences were explained when a more sensitive, kinetic endotoxin assay showed that release correlated with minor contamination with endotoxin. In a repeat experiment using cement particles with low or undetectable levels of endotoxin by kinetic assay, differences in the ability of the formulations to stimulate the release of cytokines were not seen. Endotoxin is adsorbed on to the surface of particles and it is this combination which stimulates increased release of cytokines. In both the above methods for determination of endotoxin, the water in which the particles had been soaked was examined rather than the particles directly. Further investigations showed that a kinetic assay directly on a particle suspension is the most sensitive method to measure contamination with endotoxin.

Long-term survival of Stanmore total hip replacements inserted with radiolucent bone cement.

Radio-opacifiers in bone cements are an accepted part of every-day practice. They have, however, been shown to be a potential cause of an increase in third body wear and to excite bone resorption in in vitro and in vivo studies. We reviewed the results of 228 consecutive Stanmore total hip replacements performed between 1981 and 1985 in 211 patients. All were inserted with radiolucent bone cement. Information regarding whether the prosthesis had been revised was available for all patients. Seventy-three patients (83 hips) were still alive and 41 patients (44 hips) were sufficiently healthy to attend clinic. Information regarding pain level was obtained from the remaining 32 patients. When revision of the implant was taken as the end-point, there was 95% ten-year survival, 91% fifteen-year survival and 75% eighteen-year survival. These long-term results of Stanmore THRs, performed in a district general hospital, with radiolucent bone cement, compare favourably with the other published series for this implant. We did not find the inability to see the bone cement a particular disadvantage when reviewing radiographs for signs of loosening. (Hip International 2002; 12: 274-80).

Correlation of synovial fluid cytokine levels with histological and clinical parameters of primary and revision total hip and total knee replacements.

We retrieved synovial tissue and fluid samples from patients undergoing primary total hip replacement (THR) (n 15), revision of aseptically loose THR (n 12), primary total knee replacement (TKR) (n 13) and revision of aseptically loose TKR (n 6). Several histological parameters were assessed on a relative scale of 14. Primary TJRs were clinically evaluated for degree of osteoarthrosis. Revision TJRs were assessed for migration of the implant, gross loosening and the degree of radiolucency. Cytokine levels in synovial fluid were determined with ELISA. All cytokines were significantly higher in revision TJRs than in primary replacements, as were the degree of macrophage and giant cell infiltration. We found no relationship between any clinical variable and the levels of any cytokine, but migration of the implant was related to the presence of PE debris. A significant correlation was seen between the presence of macrophages and the levels of IL-1beta, IL-8 and IL-10, but not IL-6. No differences were noted between hips and knees for any of the variables, except in the levels of IL-6, where higher levels were found in THRs. These results suggest a unique role for IL-6 that requires further investigation.

The effects of particulate bone cements at the bone-implant interface.

We used a rat model in vivo to study the effects of particulate bone cements at the bone-implant interface. A ceramic pin was implanted into the tibiae of 48 rats. Three types of particle of clinically relevant size were produced from one bone-cement base without radio-opacifier, with zirconium dioxide (ZrO2) and with barium sulphate (BaSO4). The rats were randomly assigned to four groups to receive one of the three bone cements or normal saline with 2% v/v Sprague-Dawley serum as the control. A total of 10(9) particles was injected into the knee at 8, 10 and 12 weeks after the original surgery. The animals were killed at 14 weeks and the tibiae processed for histomorphometry. The area of fibrous tissue and the gap between the implant and bone were measured using image analysis. All three types of particle were associated with a larger area of bone resorption than the control. Only in the case of the BaSO4-containing cement did this reach statistical significance (p = 0.01). Particles of bone cement appear to promote osteolysis at the bone-implant interface and this effect is most marked when BaSO4 is used as the radiopaque agent.

Inflammatory responses of human primary macrophages to particulate bone cements in vitro.

We have investigated whether the particle-stimulated release of inflammatory cytokines from human primary macrophages in vitro was dependent upon the type of bone cement used. Particles of clinically relevant size were produced from Palacos R without radio-opacifier, Palacos R with BaSO4, Palacos R with ZrO2 and from CMW3 which contains BaSO4. All four preparations produced significantly greater release of tumour necrosis factor alpha, interleukin-6 and interleukin-1 beta than a negative control but there were no significant differences between them. The differences in the ability to stimulate bone resorption and in clinical performance between proprietary bone cements previously recorded are not explained by the release of the cytokines most commonly implicated in osteolysis.

The effects of the concentration of high-density polyethylene particles on the bone-implant interface.

We used a rat model in vivo to study the effects of the concentration of polyethylene particles on the bone-implant interface around stable implants in the proximal tibia. Intra-articular injections of 10(4), 10(6) or 10(8) high-density polyethylene (HDPE) particles per joint were given 8, 10 and 12 weeks after surgery. The animals were killed after 14 and 26 weeks and the response at the interface determined. Fibrous tissue was seen at the bone-implant interface when the head of the implant was flush with the top of the tibia but not when it was sunk below the tibial plateau. In the latter case the implant was completely surrounded by a shell of bone. The area of fibrous tissue and that of the gap between the implant and bone was related to the concentration of particles in the 14-week group (p < 0.05). Foreign-body granulomas containing HDPE particles were seen at the bone-implant interface in animals given 10(8) particles. The pathology resembles that seen around prostheses with aseptic loosening and we suggest that this is a useful model by which to study this process.