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Biomedical subjects

A K Hedley

Publications and source records attributed to A K Hedley.

18 recordsLinked to original sources
PubMed1997

Extended proximal femoral osteotomy for severe acetabular protrusion following total hip arthroplasty. A technical note.

Exposing and removing the femoral and acetabular components after severe intrapelvic protrusion has occurred can be difficult and dangerous. An extended proximal femoral osteotomy carried distally to the level of the stem tip allows for atraumatic removal of the femoral stem without the need for preliminary dislocation. The exposure afforded by the osteotomy also facilitates acetabular component removal.

Bone Wires↗
PubMed1990

A posterior approach to the hip joint with complete posterior capsular and muscular repair.

A posterior approach to the hip is described, which preserves the posterior hip capsule and short external rotators. These structures are reflected during exposure and are securely repaired to bone as a single capsulomuscular flap during wound closure. This approach has been used exclusively since December 1986 for uncomplicated primary hip arthroplasty. In 259 consecutive cases, there have been only two dislocations, both associated with significant trauma.

Adult↗
PubMed1989

The prevention of heterotopic bone formation following total hip arthroplasty using 600 rad in a single dose.

While postoperative irradiation has been shown to lower the incidence of heterotopic ossification effectively in high-risk patients following total hip arthroplasty, patients in multiple-dose protocols continue to develop some heterotopic ossification despite therapy. Sixteen patients (17 hips) received single-dose exposure to 600 rad delivered within 3 days of total hip arthroplasty. The patients were considered at high risk for development of heterotopic ossification because of hypertrophic osteoarthritis, posttraumatic arthritis, or the presence of previously formed ectopic bone. Thirty-five percent of the patients underwent excision of preexisting ectopic bone at the time of arthroplasty. The average follow-up period was 11.8 months (range, 6-24 months). At follow-up study, all hips were classified as Brooker class O or I, compared to a 17% incidence of Brooker class II and III for previously reported multiple-dose protocols. All patients were asymptomatic at last follow-up study, and no component demonstrated subsidence or radiolucent lines indicative of loosening. The authors conclude that low-dose, single-fraction radiotherapy is more cost-effective and convenient and as efficacious as current multiple-dose regimens.

Adult↗
PubMed1988

Revision of failed total hip arthroplasties with uncemented porous-coated anatomic components.

This series represents a relatively short follow-up study of patients who were treated with cementless revisions for failed previous arthroplasties. Many of these cases required extensive bone grafting to the acetabulum and often to the femur. Despite extensive bone grafting, there were no infections. There has been but a single graft resorption after a hemiarthroplasty conversion for recurrent dislocations. To date, all other grafts have remained intact and have shown signs of union. Even though the acetabular components were not anchored in place by adjuvant fixation devices such as screws, migration of the acetabular component has not been a problem. All other components have remained stable, and the supporting grafts appear to have united successfully. Femoral revision has been more technically demanding because the largest stem possible should be placed within the femur to prevent subsidence and provide good stabilization in the proximal metaphyseal area. These short-term results compared favorably with similar series of cemented revisions. Patient selection is important and there are definite candidates for cemented femoral components, particularly with first-time revisions in elderly patients. If there is massive osteolysis in the femur, cemented revision is probably not indicated. Long stems should not be used unless necessary. Cortical defects at the tip of the standard stem obviously would require bypassing the stress riser with a longer stem. If, however, the cortex is intact in this region and stability can be achieved, revision should be carried out with a relatively short stem. Techniques for cementless revision are demanding, but with meticulous attention to detail and technical perfection, the method has a most encouraging prognosis. Longer follow-up evaluations will be necessary to make an accurate evaluation of graft incorporation, but short-term results are encouraging to both surgeons and patients.

Acetabulum↗
PubMed1987

Two-year follow-up of the PCA noncemented total hip replacement.

The early results with the PCA total hip replacement have been most gratifying, especially the absence of complications related to the acetabular component. The radiographic evaluation was done critically, and the finding of no progressive acetabular radiolucencies was unexpected. Longer-term evaluation of these interfaces is necessary, but the short-term results have been encouraging. No components have migrated despite the absence of adjunct fixation mechanisms such as screws and flanges. The pressfit achieved with the roughened hemispherical surface has been adequate, and the fixation with the two outrigger pegs appears to have been sufficiently stable to preserve the prosthetic stability and has resulted in successful anchorage of all the components. The results with femoral components are obviously related to technique. In a few early cases when undersized prostheses were used, loosening occurred, and four of these components advanced to detectable loosening. One of these components was revised since this analysis. Attention to detail with maximal filling of the proximal femur apparently led to improved results, with successful anchorage in all subsequent implantations. The application of the dimensional analysis before surgery may indicate those cases in which a tight fitting metaphysis cannot be achieved. In elderly patients who have osteoporotic bone, a substantial mismatch exists between the size of the metaphysis and the diaphysis, and it may be advisable to continue with cement in these cases. By applying the dimensional analysis to preoperative templating, the surgeon may be sufficiently informed to know that a tight fit can be achieved at surgery. No catastrophic failures have occurred. If loosening does occur because of undersizing of the prosthesis, the process appears to be gradual and, although associated with pain, does not result in sudden failure. Despite the prosthesis not being anchored by cement or collar, no sudden subsidence of the components has resulted. Patients' clinical performance has been somewhat slower when compared to cemented series. Performance seems to accelerate once weight bearing occurs, however, and after 2 years no difference exists between this series and a corresponding cemented series. Noncemented total hip arthroplasty appears to offer as good if not better results than cemented total hip arthroplasty, if performed correctly and in the appropriate patient. Successful outcome depends greatly on technique, but when technically adequate implantation has been performed, the results have been gratifying.(ABSTRACT TRUNCATED AT 400 WORDS)

Activities of Daily Living↗
PubMed1987

Results of transtrochanteric rotational osteotomy for femoral head osteonecrosis.

Eighteen transtrochanteric rotational osteotomies have been performed in 17 patients for femoral head osteonecrosis (15 patients, Ficat Stage III disease; three patients, Ficat Stage IV disease) during a 51-month period and have 18 to 63 months of follow-up study. The best results were in the posttraumatic and nonsteroid-associated idiopathic cases in patients with small necrotic segments in the weight-bearing region, with no degenerative changes. Failures occurred in patients with large necrotic fragments, preexisting degenerative changes, and steroid- and alcohol-associated etiologies. Although joint arthroplasty was eventually required in ten hips, a period of temporization was achieved sufficient to bring them into the era of cementless hip arthroplasties. Indications for this operation should be restricted to those patients under 40 years of age with late Ficat Stage II or Stage III disease, in which the articular involvement in the lateral roentgenogram is 50% or less.

Adult↗
PubMed1984

Anterior fracture-dislocations of the shoulder: pitfalls in treatment.

Fracture-dislocations of the shoulder can present difficulties in treatment. Two cases are described to illustrate the complications that can occur when an inexperienced examiner attempts a closed reduction of a two-part anterior fracture-dislocation of the shoulder. Careful clinical and radiologic evaluation (A-P and transcapular or axillary lateral X-rays) followed by appropriate management can help to prevent these problems from occurring. If there is evidence that the fracture is displaced by manipulation, immediate open reduction and internal fixation are recommended.

Female↗
PubMed1983

Prosthetic replacement in osteonecrosis of the hip.

The young patient with avascular necrosis of the hip presents one of the unsolved problems in orthopaedics today. Many of these patients are active and have expectations of continuing activities that may be far in excess of reality, considering the results achieved in these patients with replacement arthroplasty. In contrast to this group of patients, the patient with systemic disease has a built-in "brake" and appears to do well with conventional arthroplasty. New fixation techniques are yielding more promising results, and continued research into new modes of fixation such as porous ingrowth may well cast a new light on the problem. At this time, however, the clinician is called on to evaluate not only the disease process but the anticipated continuing activity of the patient. Thus there is no one procedure appropriate for this disease but rather several alternatives, each having its own indication at a specific stage in the disease process.

Adolescent↗
PubMed1983

External fixation as a secondary procedure.

Twenty-two patients were treated by external skeletal fixation as a secondary procedure after failure of primary management with other modes of treatment. Fourteen of these cases were infected at presentation. The average duration from the time of injury to the application of external fixation was 17 months. Ninety-five per cent of fractures united with this treatment, and there have been no recurrent infections, with a minimum follow-up evaluation of one year. Pin tract problems were frequent and consisted of drainage, with or without pin loosening. All patients allowed unrestricted weight-bearing experienced some form of pin problem, whereas only 12% of patients restricted to touch-down weight-bearing with crutches developed pin tract problems; none has had residual pin tract infections. External fixation is an effective secondary measure for injuries that have failed to unite by primary treatment. Use of external fixation requires close supervision of postoperative treatment and, especially, close attention to pin insertion and management.

Adult↗
PubMed1983

Bony ingrowth fixation of newly designed acetabular components in a canine model.

Implantation of a newly designed acetabular component with a porous coating has resulted in superior fixation when compared with acrylic cementation in the short term. Experiments in dogs demonstrate rapid ingrowth within the porous layers, resulting in rigid fixation of the acetabular components despite defects in the prepared bony bed. Acute infection prevents bony ingrowth and causes loosening. The absence of any foreign-body response to the titanium fiber mesh components suggests that this is a biocompatible metal. The fixation has been excellent; progressive or delayed loosening is not encountered once successful ingrowth is achieved. Progressive radiolucent zones generally do not appear in the short term but when visible soon after surgery, may consolidate and disappear. Ingrowth fixation of acetabular components appears to offer an attractive alternative to the use of acrylic cement and may even be feasible in patients with periarticular bony abnormalities.

Acetabulum↗
PubMed1982

Radiology of failed surface-replacement total-hip arthroplasty.

The radiographs, arthrograms, and bone scans in 23 patients with surgically confirmed failed total-surface hip replacement were reviewed. Guidelines for evaluation of the acetabular component are identical to those for conventional total arthroplasty. The femoral component of a surface-replacement total hip arthroplasty consists of a metallic cup affixed to a resurfaced femoral head with interposed methyl methacrylate. Because of bone-acrylic interface is obscured by the metallic cup, the radiographic features of loosening are limited to an abnormal alignment of the metallic cup in relation to the femoral neck or a change in the position of the cup in serial radiographs. These signs may be subtle. While the metallic cup may often prevent visualization of underlying isotope activity at the bone-acrylic interface, increased activity at the base of the cup when identified suggests loosening or infection.

Acetabulum↗
PubMed1982

Porous ingrowth fixation of the femoral component in a canine surface replacement of the hip.

Prosthetic fixation by growth of bone into porous implants coated with a sintered layer of cobalt chrome beads offers an attractive alternative to acrylic cementation. Experiments on dogs demonstrate that bone ingrowth occurred into the femoral component of a hip surface replacement. Methods of stabilizing prostheses in order to promote bone ingrowth must not interfere with the uniformity of stress transfer at the bone - implant interface. Ingrowth occurred as early as the second week postimplantation. The absence of any fibrous membrane formation in the interface between bone and metal suggests that sintered chrome cobalt is a highly compatible biological system, and that fixation by bone ingrowth is stable and does not promote osteoclasis and progression to a fibrous membrane at the interface.

Animals↗
PubMedDate not supplied

Strain redistribution in the canine femur resulting from hip implants of different stiffnesses.

Bone remodeling adjacent to orthopedic implants has been attributed to bone strain changes. Although many animal studies have assessed bone remodeling near implants, the altered bone strains and even the strains in the intact bone prior to implantation have not been mapped extensively. Instead, bone changes are often correlated with implant stiffnesses. In this study, a benchtop loading system was developed using measurements from in vivo strain analysis to simulate physiologic loading of a canine femur. The effect on bone strains of three different stiffness canine hip implants with the same anatomic shape were compared by taking measurements from the proximal greyhound femur during loading. Peak compressive and tensile strains of the order of 200 to 400 microstrain were measured in the intact and implanted femora. The measurements indicate that during simulated in vivo loading, none of the implants substantially alter the normal strain state of the bone. If initial axial strains significantly affect the remodeling response of bone, the similarity of measurements with the different implants in place suggests that the same remodeling response would be expected to both the stiffest and least stiff implant, as has been noted in animal studies adjacent to the intermediate stiffness implant. It also suggests that this implant shape and initial bone implant interface condition can compensate for strain reductions expected near stiff straight-stemmed implants.

Animals↗
PubMedDate not supplied

The acetabular cement-bone interface in experimental arthroplasties in dogs.

Increased clinical loosening of total hip arthroplasty acetabular components has been noted in patients with long follow-up and in young active individuals. Evaluation of the acetabular cement-bone interface has been limited to a few human cadaveric specimens and to canine studies in which the data are difficult to interpret. The effects of cement fixation of the acetabular component were investigated in serial observations in 21 dogs with hip surface replacements. The postoperative survival time before evaluation was from two to 46 weeks. Twenty animals were clinically normal before autopsy. Analytic techniques used to examine acetabular fixation included the use of epoxy-embedded specimens to preserve the cement-bone interface and conventional histologic sections. After two weeks, no direct contact between the cement and bone was seen. A correlation between the adequacy of cement fixation and interface membrane thickness was found. Poor acrylic fixation resulted in thick membranes up to 2 mm thick and horizontal trabeculation of the interface woven bone. Good cement intrusion led to a thinner, almost minimal membrane two to three cells in thickness.

Acetabulum↗