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Biomedical subjects

Clive P Duncan

Publications and source records attributed to Clive P Duncan.

At least 19 recordsLinked to original sources
PubMed2007

Cementless two-stage exchange arthroplasty for infection after total hip arthroplasty.

We retrospectively reviewed all patients at one center with an infected total hip arthroplasty treated with 2-stage revision using cementless components for the second stage and the PROSTALAC articulated spacer at the first stage. Twenty-nine patients were reviewed and followed for at least 2 years postoperatively. An isolated Staphylococcus species was cultured in 76% (22/29) of patients. Three (10.3%) of 29 patients had recurrent infection at the site of the prosthesis. One of the 3 patients ultimately underwent a Girdlestone arthroplasty. Another patient was managed with irrigation and debridement, whereas the final patient was treated with intravenous antibiotics alone. Treatment of infection at the site of a hip arthroplasty with 2-stage revision using cementless components and an articulated spacer yields recurrence rates similar to revisions where at least one of the components at the second stage is fixed with antibiotic-loaded cement.

Adult↗
PubMed2006

Cement flow during impaction allografting: a finite element analysis.

Cement intrusion into cancellous or impacted bone is not well understood. We adopted an engineering mechanics approach to predict the effect of surgical variables on the cement intrusion into impacted cancellous bone, used for the revision of failed total hip replacement with the impaction allografting technique. Specifically, a three-dimensional finite element model was used to determine the effects of cement viscosity, the magnitude and duration of pressurization, and the distribution of the porosity along the femur on cement intrusion. The overall averaged mean intrusion depth difference between the finite element model prediction and the cadaveric measurements was 1.1mm. The depth of penetration increased with higher pressurization pressure, duration of pressurization, and earlier stem insertion (lower viscosity), but maintained a similar profile. The distribution of the porosity along the femur determined the intrusion profile. Cement viscosity, the applied pressure or the duration of the pressurization can be adjusted to limit the cement volume injected into the medullary canal and therefore prevent the cement from reaching the endosteal surface.

Bone Cements↗
PubMed2006

Delays worsen quality of life outcome of primary total hip arthroplasty.

Although there are indications of health status deterioration for patients while waiting for elective total hip arthroplasties, controversy exists regarding the effect of waiting on postoperative outcomes. We hypothesized that longer waiting times are detrimental to achieving the full benefit of surgery. We prospectively examined 201 patients with osteoarthritis who were on the waiting list for primary total hip arthroplasties. The Western Ontario and McMaster Universities Osteoarthritis Index questionnaire was used to assess patients at surgical consultation (preoperative) and 1 year postoperative. The study included regression models to determine the expected outcome for an individual's preoperative score. Logistic regression models were used to assess the relationship between waiting time and the probability of a better than expected outcome. We found that the odds of achieving a better than expected postoperative functional outcome decreased by 8% for each month on the waiting list. Expedited access resulted in a larger proportion of patients with better than expected function 12 months after surgery.

Adult↗
PubMed2006

Accuracy of cut-off acetabular reamers for minimally invasive THA.

Cut-off reamers have been introduced for minimally invasive hip replacement to make reamer insertion through the small incision easier. However, the accuracy of cut-off reamers in comparison to traditional hemispherical reamers has not been documented. We reamed four human cadaveric hips using a cut-off reamer and three hips using a standard reamer. We started with smallest size reamer to remove subchondral bone, and the size was progressively increased until breaching the acetabular floor. We performed computed tomography scans for each reamer size to digitally determine the true dimensions and sphericity of the reamed acetabula. The cut-off reamers breached the acetabulum at a smaller size than with a standard reamer in two specimens, and at the same size as the standard reamer in one specimen. The accuracy of each reamer size was determined by quantifying the percentage of the reamed acetabular surface that was within 0.5 mm of the hemispherical reamer size. The average accuracy of the cut-off reamers was 70% compared with 81% for the standard reamers. The cut-off acetabular reamers showed a trend toward decreased accuracy that may be attributable to a tendency of the reamer to wobble in use.

Acetabulum↗
PubMed2006

Minimally invasive or limited incision hip replacement: clarification and classification.

The goal of total hip replacement is to provide a pain-free, well-fixed, stable, long-lasting arthoplasty. Length of hospital stay, recovery time, and incision length are important factors related to the success of the procedure. As the procedure has evolved, the use of limited incision surgery has grown. A uniform classification system for less invasive approaches to total hip replacement will allow similar approaches to be grouped together and help surgeons to select the best approach.

Arthroplasty, Replacement, Hip↗
PubMed2006

The limited incision, anterolateral, intermuscular technique for total hip arthroplasty.

Limited incision total hip arthroplasty has potential advantages over traditional techniques. Many new approaches have been advocated, however, each new approach has a number of drawbacks. A technique using a single incision with an anterolateral, intermuscular approach offers attractive advantages including the use of the more familiar lateral positioning for the patient and a short learning curve for the surgeon. Also, intraoperative fluoroscopy is not required and the surgeon can perform a trial reduction and can extend the approach if necessary.

Arthroplasty, Replacement, Hip↗
PubMed2006

Evaluation of patients with pain following total hip replacement.

Ongoing pain after total hip replacement is a source of frustration to both the patient and the surgeon. A structured approach to the evaluation of patients with postoperative pain is essential. The key to such an approach is a meticulous patient history and physical examination. The results of relevant investigations allow an effective treatment plan to be quickly implemented.

Arthrography↗
PubMed2006

Optimally invasive exposure in revision total hip arthroplasty: a guide to selection and technique.

Revision total hip arthroplasty requires a careful surgical plan. Selection of the appropriate exposure is an essential step for success. Exposure is important not only for the complete and safe visualization and extraction of components and cement, but also for the achievement of a stable construct at the end of the procedure. In addition, controlled exposure minimizes intraoperative complications and bone and soft-tissue damage, essential considerations for eradication of infection. Three questions need to be addressed at the preoperative stage: (1) Is this a straightforward revision that can be handled with a standard approach? (2) Is this a more complex revision requiring an extensile exposure? (3) Is this an unusual revision requiring special techniques to allow adequate access that cannot be obtained using standard extensile techniques? Each group of exposures presents three further possibilities, each of which has specific indications, advantages, and disadvantages. In conjunction with the preoperative analysis, this knowledge should enable the revision surgeon to select the most appropriate approach, resulting in optimal exposure for each individual revision scenario.

Arthroplasty, Replacement, Hip↗
PubMed2005

Biological and mechanical changes of the bone graft-cement interface after impaction allografting.

In impaction allografting, the host bone interface may consist of morsellized allograft alone or as a composite with bone cement. The objective of this study was to investigate the temporal changes in the interface for these two materials in a rat bone chamber model. To simulate the impaired endosteal circulation after impaction allografting, bone chambers were tightened bilaterally to the endosteal surfaces of proximal tibiae of mature rats and filled with pure allograft or cement/allograft composite. The cement/allograft composite-host bone interface strength was significantly higher at 3 weeks and was higher than the allograft construct failure strength. Limited allograft, but extensive periosteal remodeling, was observed at 3 weeks which resulted in a significantly increased cortical porosity and cortical thickness. The allograft porosity decreased significantly at 6 weeks indicating extensive remodeling of the allograft bone. Little or no remodeling of the allograft particles in the cement was found. At 6 weeks a new medullary canal was formed, and the endosteal cortex was partially absorbed. Endosteal absorption resulting in medullary canal widening in revision THR may be responsible for clinically unstable stems after impaction allografting.

Animals↗
PubMed2005

Calcium phosphate cement composites in revision hip arthroplasty.

Loosening of the femoral component in a total hip arthroplasty with concomitant bone loss can pose a problem for revision surgery due to inadequate structure in the remaining femur. While impaction allografting has shown promise, it has also shown serious complications, especially with moderate to severe bone loss. It may be possible to stabilize the graft layer with a bioresorbable cement to improve clinical results. This study examines the mechanical properties of a potential morsellized bone-bioresorbable composite. Morsellized bone was mixed with a commercially available bioresorbable cement (alpha-BSM, Etex Corp.) in compositions of 0%, 25%, 50% and 75% bone. Unconfined compression and diametral tensile and confined compression tests were performed to determine the composite mechanical properties. The composition containing 50% bone tended to exhibit the highest uniaxial strengths, as well as the highest confined compression modulus. The uniaxial compressive strength and stiffness of this composition was in the range of cancellous bone. Uniaxial compressive modulus decreased with increasing bone fraction whereas elongation exhibited the opposite trend. Bone fraction had a significant effect on compressive strength (p < 0.0001), compressive modulus (p < 0.0001), elongation (p < 0.01), tensile strength (p < 0.0001) and confined compressive modulus (p = 0.04). The addition of a bioresorbable cement to the allograft layer may improve the properties of the layer, preventing early subsidence seen in some clinical studies of impaction allografting, and therefore improving the clinical results. Further testing is required to evaluate the in vitro mechanical performance, as well as in vivo remodelling characteristics.

Aged↗
PubMed2005

A biomechanical study comparing cortical onlay allograft struts and plates in the treatment of periprosthetic femoral fractures.

BACKGROUND: Periprosthetic femoral fractures with well-fixed femoral components can be difficult to manage and internal fixation is usually necessary. This study was designed to determine the effect of cable plate, strut allograft and combined plate and strut allograft fixations of periprosthetic femoral fractures. METHODS: A transverse fracture at the level of the tip of the femoral stem was simulated in six cadaveric femurs. The fracture was fixed with a plate-strut graft construct with and without proximal screws, a plate only construct with and without proximal screws and with both anterior and lateral struts grafts of 12 cm or 20 cm in length. The intact femur and the six constructs were tested using anteroposterior and axial loads to simulate the forces at the hip during gait. The interfragmentary motions were measured with an optoelectronic camera system. FINDINGS: The highest median interfragmentary translations were observed with the plate only construct without proximal screws. No significant differences in median translations were found between the combined plate-strut and the strut-graft alone constructs. Median interfragmentary rotations were largest with the plate only construct and lowest with the plate-strut constructs. INTERPRETATION: The best fracture fixation was achieved with the combined plate and strut graft constructs particularly in combination with the two unicortical screws above the fracture. The plate only constructs may not provide sufficient fixation stability in rotation for the simulated transverse fracture. The within-construct interfragmentary motions were not significantly different except for the plate only constructs. This suggests that the fixation construct type is the determining factor of interfragmentary motion.

Arthroplasty, Replacement, Hip↗
PubMed2005

Structural characteristics of impaction allografting for revision total hip arthroplasty.

BACKGROUND: The impaction allografting procedure for treatment of failed hip reconstructions has shown promising but variable results. The objective of this study was to compare the structural characteristics of revision total hip arthroplasty constructs with impaction allografting (cement+morsellized bone) with all-cement and all-morsellized bone constructs. METHODS: Uniaxial cyclic compression was applied to a simplified uniaxial, parallel, aluminum tube model to simulate normal gait. Applied force and axial stem displacement were recorded to determine stem subsidence and construct stiffness. FINDINGS: Introduction of a small amount of cement into the bone graft, as suggested in an impaction allografting procedure previously reported, makes the construct behave structurally more similar to an all-cemented construct than to an all-bone graft construct. INTERPRETATION: The results suggest that the structural properties achieved in an impaction allografting construct are sensitive to the amount of cement in the graft and that care should be taken clinically to achieve consistent constructs.

Arthroplasty, Replacement, Hip↗
PubMed2005

Mechanical characteristics of the bone-graft-cement interface after impaction allografting.

Impaction allografting is an attractive procedure for the treatment of failed total hip replacements. The graft-cement-host bone interface after impaction allografting has not been characterized, although it is a potential site of subsidence for this type of revision total hip reconstruction. In six human cadaveric femurs, the cancellous bone was removed proximally and local diaphyseal lytic defects were simulated. After the impaction grafting procedure, the specimens were sectioned in 6 mm transverse sections and push-out tests were performed. From the adjacent sections the percentage cement contact of the PMMA cement with the endosteal bone surface was determined. The host bone interface mechanical properties varied significantly along the femur largely due to different interface morphologies. The apparent host bone interface shear strength was highest around the lesser trochanter and lowest around the tip of the stem. A significant positive correlation was found between the percentage cement contact and the apparent host bone interface shear strength (r2 = 0.52). The sections failed in 69% of the cases through a pure host bone interface failure without cement or allograft failure, 19% failed with local cement failure, and 12% with a local allograft failure. The apparent host bone interface strength was on average 89% lower than values reported for primary total hip replacements and were similar to cemented revisions proximally and lower distally. This study showed that cement penetration to the endosteal surface enhanced the host bone-graft interface.

Biomechanical Phenomena↗
PubMed2005

Trochanteric osteotomies in revision total hip arthroplasty: contemporary techniques and results.

Revision total hip arthroplasty (THA) presents several challenges to the orthopaedic surgeon and typically requires the use of a more extensile surgical approach. Osteotomy of the greater trochanter can be considered as the ultimate extensile exposure in revision THA. The methods of trochanteric osteotomy can be categorized into three types: the standard trochanteric osteotomy, the trochanteric slide, and the extended trochanteric osteotomy. Although the standard osteotomy and trochanteric slide osteotomy provide excellent acetabular exposure, in the revision setting they are frequently associated with an unacceptably high rate of nonunion and proximal migration of the trochanteric fragment. The extended trochanteric osteotomy (ETO) has increased in popularity as the number and complexity of revision THAs continue to increase. Two commonly used techniques are the ETO via a posterolateral approach or via a modified direct lateral approach. Both techniques provide wide exposure of the acetabulum, facilitate femoral component exposure and removal, aid in canal preparation and femoral reconstruction, and allow for correction of proximal femoral deformity. The osteotomy fragment is easily secured and may be advanced distally to achieve proper tensioning of the abductors. Recent literature demonstrates that the ETO has a relatively low rate of nonunion and is associated with fewer intraoperative femoral fractures or cortical perforations, as well as decreased surgical time.

Arthroplasty, Replacement, Hip↗
PubMed2004

Osteoblast-derived factors induce androgen-independent proliferation and expression of prostate-specific antigen in human prostate cancer cells.

PURPOSE: Prostate cancer metastasizes to the skeleton to form osteoblastic lesions. Androgen ablation is the current treatment for metastatic prostate cancer. This therapy is palliative, and the disease will return in an androgen-independent form that is preceded by a rising titer of prostate-specific antigen (PSA). Here, we investigated the possibility that human osteoblasts might secrete factors that contribute to the emergence of androgen-independent prostate cancer. EXPERIMENTAL DESIGN: Primary cultures of human osteoblasts were used as a source of conditioned medium (OCM). Proliferation, expression of androgen-regulated genes, and transactivation of the androgen receptor (AR) were monitored in LNCaP human prostate cancer cells in response to OCM using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, Northern blot analysis, and reporter gene constructs. Levels of interleukin-6 (IL-6) present in OCM were measured, and its contribution to proliferation and expression of PSA were investigated by neutralization studies with anti IL-6 antibodies. RESULTS: OCM increased the proliferation and expression of PSA at both the protein and RNA levels in LNCaP cells. Synergistic increases in the activities of PSA (6.1 kb)- and pARR(3)-tk-luciferase reporters were measured in cells cotreated with both OCM and androgen. OCM targeted the NH(2)-terminal domain of the AR. The effect of OCM on transcriptional activity of the AR was inhibited by an antiandrogen. Neutralizing antibodies to IL-6 blocked proliferation and expression of PSA by OCM. CONCLUSION: Osteoblasts secrete factors, such as IL-6, that cause androgen-independent induction of PSA gene expression and proliferation of prostate cancer cells by a mechanism that partially relies on the AR. Identifying such molecular mechanisms may lead to improved clinical management of metastatic prostate cancer.

Androgens↗
PubMed2004

Minimally invasive hip replacement: rationale, applied anatomy, and instrumentation.

The term minimally invasive hip replacement encompasses a diverse range of surgical approaches through which hip replacement may be performed. These surgical approaches are technically demanding and are best performed using specially designed instruments that help to compensate for the reduced surgical exposure. The early results using these techniques are encouraging, although the literature is lacking evidence from well designed prospective trials comparing MIS techniques with standard approaches. The studies that exist suggest that patient satisfaction is high, bleeding may be reduced, recovery of function may be faster, and there may be the potential to reduce lengths of hospital stay, and all this may be achieved without increasing complication rates. These results,however, have been achieved by a small number of high-volume surgeons, and the authors feel it is essential that as these techniques are introduced into widespread practice the results be studied carefully.

Arthroplasty, Replacement, Hip↗
PubMed2004

Minimally invasive unicompartmental knee replacement: rationale and correct indications.

In the early 1990s, unicompartmental knee replacements (UKRs) were almost forgotten as an option for the management of unicompartmental arthritis of the knee, and the two principal surgical options became proximal tibial osteotomy and total knee replacement. The recent introduction of minimally invasive techniques has renewed interest in uni-compartmental knee replacement. The proposed advantages of UKR over proximal tibial osteotomy include more predictable relief of pain, quicker recovery, and better long-term results. In appropriate cases, it has advantages over total arthroplasty in providing more physiologic function, better range of movement, easier salvage in case of failure, and quicker recovery because of minimally invasive techniques.

Arthroplasty, Replacement, Knee↗