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Clive P Duncan

Publications and source records attributed to Clive P Duncan.

At least 19 recordsLinked to original sources
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↗
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↗
PubMed2004

Minimally invasive versus standard incision anterolateral hip replacement: a comparative study.

The results of the authors' study show that total hip arthroplasty can be performed safely through a minimal incision anterolateral approach. The authors' early results with this technique have demonstrated an increase in the length of operation compared with a standard approach, despite selection of smaller patients, but the authors expect this result will change with further experience. No benefit has been found with respect to perioperative blood loss, but the authors' results do suggest that for patients without additional medical problems, this technique may lead to a reduction in the length of hospital stay. Further study is required to clarify the benefits conferred by a minimal incision anterolateral approach.

Arthroplasty, Replacement, Hip↗
PubMed2004

Periprosthetic fractures evaluation and treatment.

Periprosthetic fracture is a serious complication of total hip arthroplasty (THA) that can be difficult to treat, and can be potentially fraught with complications. The incidence of such fractures is increasing, especially after the use of cementless revision arthroplasty. The prevention of these fractures is achieved by understanding the risk factors involved. If the risks are not understood, the best outcome is achieved when the surgeon has a thorough understanding of the principles of treatment of these fractures and has access to various fixation and prosthetic devices, and allograft bone when necessary. Acetabular fractures are rare and relatively little has been reported on their treatment. Periprosthetic femoral fracture treatment is based on the site of fracture, implant stability, and bone stock. The Vancouver classification offers a reproducible description of these factors with the subsequently easy formation of a treatment plan.

Acetabulum↗
PubMed2004

Intraoperative fracture of the femur in revision total hip arthroplasty with a diaphyseal fitting stem.

BACKGROUND: In revision total hip arthroplasty, intraoperative split fractures and cortical perforation fractures are becoming a more common concern with the increasing use of diaphyseal fitting cementless stems. The purpose of this study was to evaluate the risk factors and frequency of intraoperative fractures with the use of these stems and their effect on radiographic and functional outcomes. METHODS: We performed a retrospective case-control study of 211 consecutive patients who had undergone revision hip arthroplasty with a diaphyseal fitting cementless stem between December 1998 and March 2002. Sixty-four patients sustained an intraoperative fracture of the femur. One hundred and fifteen patients were followed for a minimum of two years; function was analyzed with self-administered outcome questionnaires, and radiographs were evaluated for evidence of bone ingrowth into the femoral stem. RESULTS: Risk factors associated with an intraoperative fracture were a substantial degree of preoperative bone loss, a low femoral cortex-to-canal ratio, underreaming of the cortex, and the use of a large-diameter stem. The majority of the diaphyseal undisplaced linear fractures occurred at the distal end of an extended trochanteric osteotomy during stem insertion. Fracture due to cortical perforation occurred most often during cement removal. These intraoperative fractures had no significant effect on the functional outcome or radiographic evidence of bone ingrowth. CONCLUSIONS: There was a surprisingly high rate of intraoperative femoral fractures associated with the use of a diaphyseal fitting stem in revision total hip arthroplasty. Identification of risk factors such as preoperative bone loss and a low cortex-to-canal ratio may permit planning to avoid such fractures. However, the final functional and radiographic outcomes appear to have been unaffected by the fracture when it had been managed appropriately. LEVEL OF EVIDENCE: Prognostic study, Level II-1 (retrospective cohort study). See Instructions to Authors for a complete description of levels of evidence.

Activities of Daily Living↗
PubMed2004

Cable plates and onlay allografts in periprosthetic femoral fractures after hip replacement: laboratory and clinical observations.

Fractures of the femur after total hip replacement are an increasingly common and technically challenging problem. The results of nonsurgical treatment are poor. When the general condition of the patient allows, these injuries should be treated surgically. Several surgical treatments can be used to treat these fractures, and classification of the fracture assists the surgeon in the choice of procedure. Over the past decade, cable plate fixation systems and onlay strut allografts have become two of the most commonly used methods of fixation for fractures associated with hip prostheses. The ideal method of fixation is yet to be determined. However, laboratory studies have shown that dual fixation using either a lateral plate and anterior strut graft or two strut grafts produces the strongest construct. Cables rather than smooth wires should be used for fixation, and fixation strength increases with the number of cables used. The use of screws proximally produces a strong fixation but there are theoretical disadvantages to using screws around a femoral implant. Clinical data show high rates of fracture union using cable plate fixation, cortical onlay allograft fixation, and combined fixation methods for fractures that occur around well-fixed implants. Results have been less encouraging when these techniques have been used to fix fractures around prostheses that are either loose or malaligned; such fractures are better managed by revision of the femoral component to a long-stemmed device. Care should also be taken when there has been previous periosteal stripping of the femur because this may predispose to fracture nonunion. Periprosthetic fractures of the femur are a complex surgical problem and require specialized training in a range of surgical techniques.

Arthroplasty, Replacement, Hip↗
PubMed2004

Extended trochanteric osteotomy: planning, surgical technique, and pitfalls.

The extended trochanteric osteotomy is appropriate for a number of surgical indications. It facilitates removal of well-fixed cement mantles with a loose or well-fixed stem and of extensively porous-coated or tapered cementless stems. This exposure is particularly valuable in the presence of varus remodeling of the proximal femur, permitting correction of proximal femoral deformity and reducing the risk of fracture of the greater trochanter. It is also indicated in the removal of a well-fixed cemented stem that is complicated by infection, where it is vital to extract all foreign material for successful eradication of the infection. In addition, when the osteotomy is required for femoral exposure, it enhances acetabular exposure to allow even the most complex reconstruction. Also, as the soft-tissue attachments to the bone fragment are preserved in this approach, abductor muscle tension can be adjusted.

Arthroplasty, Replacement, Hip↗
PubMed2004

Cementing constrained acetabular liners in revision hip replacement: clinical and laboratory observations.

During revision hip arthroplasty, removal of a well-fixed, ingrown metal acetabular component may not be possible. Therefore, a new polyethylene liner can be cemented into the existing shell via the cement locking mechanism. This technique is well recognized, and the cement locking mechanism has proved to be sufficiently strong and durable for clinical use. A constrained polyethylene liner is designed to reduce the risk of hip dislocation by capturing the femoral head. However, there are increased shear forces created at the liner interface as the dislocation is resisted. If a constrained liner is cemented into an ingrown acetabular component, then there is the theoretical risk that these increased shear forces will damage the cement locking mechanism, thus leading to failure of the construct. There are a few clinical series in which a constrained liner has been used with the cement locking mechanism. Overall, the failure rate of the cement locking mechanism is no greater if a constrained liner instead of a standard liner is used. The cement locking mechanism can be strengthened by roughening the backside of a smooth polyethylene liner to improve the cement-polyethylene interface, or by using an all-polyethylene acetabular component that is designed to be used with cement. Whether a smooth metal shell needs to be roughened as well is a matter of debate.

Arthroplasty, Replacement, Hip↗
PubMed2004

Can a new design of pneumatic compression device reduce variations in delivered therapy for the mechanical prophylaxis of thromboembolic disease after total hip arthroplasty?

BACKGROUND: Compression devices have been shown to prevent thromboembolic disease. However, the pressures generated may not be the same as the ones recommended by the manufacturer. The purpose of this study is to investigate a new sequential compression device with feedback to maintain optimal therapy, and to determine whether therapy is improved with this new device. PATIENTS AND METHOD: A series of 50 patients undergoing elective total hip arthroplasty at a major tertiary-care hospital with a special interest in joint replacement were enrolled prospectively. In addition to pharmacological prophylaxis for thromboembolic disease, all patients received compression from a modified device. Maximum pressures generated and the rate of pressure rise in each of the 3 compartments within the device sleeves were measured and the results compared with data from historical controls. RESULTS: We considered therapy to be ideal when in a particular compression cycle all chambers of both right and left sleeves reach within 10% of their target pressures at within 10% of their target pressure rise rates. The average patient received this ideal therapy 88% of the time that the new trial sequential compression device was operating. This represents a dramatic improvement over previous devices. CONCLUSIONS: The new device allows dramatically improved pressures within the device because of a feedback loop that allows dynamic control of each chamber's pressure. Improved consistency of delivery should make it easier to accurately assess the true benefits of mechanical prophylaxis with a sequential compression device.

Adult↗