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Biomedical subjects

F H Sim

Publications and source records attributed to F H Sim.

At least 55 records · Page 3Linked to original sources

Dedifferentiated chondrosarcoma of bone.

Dedifferentiated chondrosarcoma is a highly malignant variant of chondrosarcoma. Approximately 11% of chondrosarcomas can be expected to dedifferentiate into more anaplastic lesions. Radiographic evidence of a benign-appearing cartilage lesion adjacent to a lytic, highly aggressive lesion suggests dedifferentiation. Despite radical surgical treatment, the prognosis is unfavorable, with a 5 year survival rate of 10%.

Aged

Salvage of the limb in the treatment of malignant pelvic tumors.

From 1970 through 1985, at the Mayo Clinic, sixty patients had operative treatment, with salvage of the limb, for a primary malignant tumor of the pelvis. Chondrosarcoma, osteosarcoma, and fibrosarcoma were common diagnoses. There were twenty-three iliosacral, twenty-five acetabular, and twelve ischiopubic lesions. Most of the resections were done with a wide margin and disruption of femorosacral continuity. Reconstruction included ten iliosacral, fourteen iliofemoral, and three ischiofemoral arthrodeses, and approximately 50 per cent of the procedures resulted in fusion. The average length of follow-up exceeded five years. Seventeen per cent of the patients, primarily those in whom an iliosacral lesion extended into the sacrum or along the spinal column, had a local recurrence. Twenty-one patients (37 per cent) had metastasis. The best functional results were seen after resections in which femorosacral continuity was maintained or reconstructed. If satisfactory margins can be achieved by the excision of a pelvic tumor, salvage of the limb is justified from both an oncological and a functional standpoint.

Adolescent

Metastatic diaphyseal fractures of the shaft of the humerus. The structural strength evaluation of a new method of treatment with a segmental defect prosthesis.

The surgical treatment of extensive metastatic diaphyseal lesions of the humerus with pathologic fractures is difficult. Patients with failed internal fixation often have large segments of bone loss. Rigid fixation often is not possible in these cases. Four patients were treated with a titanium segmental defect (SD) prosthesis with good clinical results. A comparative in vitro analysis of fixation with the SD prosthesis, a Rush rod, and a dynamic compression plate (DCP) augmented with methylmethacrylate was performed. The SD prosthesis performed better than the Rush rod and DCP in both the nondestructive four-point bending test and the destructive torsional test. The reconstructed humeri using the SD prosthesis had a torsional strength approaching that of an intact specimen. Hence, the SD prosthesis is a useful adjunct device in treating patients with extensive destructive lesions of the humerus secondary to metastatic disease and hematologic malignancies and in patients with malignant diseases who have had failed attempts at internal fixation.

Adult

Wedge resection of the symphysis pubis for the treatment of osteitis pubis.

Ten patients had a wedge resection of the symphysis pubis for the treatment of symptoms of osteitis pubis that had been recalcitrant to non-operative treatment for at least six months. Preoperatively, the average duration of symptoms was thirty-two months. The symptoms included a waddling gait and crepitus, pain, and tenderness over the symphysis pubis. The early radiographic signs of the disease were rarefaction of the adjacent pubic bones and widening of the symphysis pubis. Later signs included sclerosis and narrowing of the symphyseal joint space. Pathological examination of the resected joint revealed chronic inflammatory reaction in all patients. At an average of fourteen months postoperatively, all of the patients had marked improvement and were fully active. However, at an average of ninety-two months postoperatively, three of the ten patients were not satisfied with the result. One patient needed bilateral sacro-iliac arthrodesis for pain that was caused by instability.

Adult

Soft-tissue sarcoma: Mayo Clinic experience.

Soft-tissue tumors encompass a wide variety of lesions and continue to pose a difficult treatment problem. The outlook, however, is improving, and there have been recent advances in pretreatment assessment, clinicopathologic correlation, and adjuvant treatment programs. We retrospectively reviewed our experience in a large series of soft-tissue tumors treated at the Mayo Clinic as well as recent experience using chemotherapy and radiation treatment.

Adult

Anterior knee pain.

Anterior knee pain is a common symptom, especially in adolescence, and often no specific cause is sought or identified. Physicians who treat patients with knee pain should understand the normal anatomic features and the biomechanics of the patellofemoral joint. We review this information and discuss important aspects of the physical examination and roentgenographic evaluation in patients with anterior knee pain. Once the clinical cause of anterior knee pain has been established, directed nonoperative treatment including physical therapy should be initiated. Surgical intervention is generally reserved for patients in whom nonoperative management is unsuccessful and identifiable abnormalities exist.

Adolescent

Xanthoma of bone.

The authors report on 21 cases of "primary" xanthoma of bone. Twenty of the patients were older than 20 years old. The male-female ratio was 2:1. The presenting symptom was pain in 13 patients and neurologic symptoms in 2; in 6 patients, the lesion was an incidental finding. All but one of the lesions in this series were solitary, and the flat bones (pelvis, rib, skull) were the most frequently involved sites. Radiographically, a well-defined, sometimes expansile lytic lesion, with either a small area of surrounding reactive bone or a distinct sclerotic margin, was seen. Microscopically, foam cells, giant cells, cholesterol clefts, and fibrosis were present in varying degrees. In none of these cases was there an identifiable underlying lesion. The differential diagnosis includes Erdheim-Chester disease (a multisystemic granulomatosis) and bone involvement in sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman disease). More important is the differential diagnosis with metastatic clear cell carcinoma. Xanthoma of bone is a benign lesion, and complete or even partial removal is effective. Xanthomas may represent a "burnt-out" benign condition such as fibrous dysplasia or histiocytosis X.

Adolescent

Ice hockey injuries.

Ice hockey is a team sport that has recently grown in popularity not only in the United States but also in Canada and Europe. With this increase in popularity has come a growing concern about the number and severity of injuries. The world literature on the biomechanics and physiology of ice hockey was reviewed in an attempt to evaluate the forces and mechanisms involved in the game. The influence of rule and equipment changes on injury patterns was particularly studied. Several studies on the epidemiology of injuries, providing data on the types of injuries and the mechanisms of those injuries, were analyzed to determine the conclusions that could be supported and those that require further study. Possible changes in the patterns and types of injury are outlined.

Adolescent

Metastatic tumors of the foot and ankle.

In a review of the Mayo Clinic files, 17 biopsy-proven cases of metastatic tumors of the foot and ankle were found; 4 additional cases were considered to have metastatic disease on the basis of clinical and radiographic evidence but no histological confirmation was available. Lung, kidney, and colon were the most common sites of the primary tumors. The patients survived as long as 28 months after discovery of the metastasis. Treatment consisted of individualized combinations of orthotics, surgery, and radiotherapy to maintain mobility. In 9 of these 17 cases, no primary lesion was identified at the time the metastasis was diagnosed. Metastatic tumors of the foot present special problems in diagnosis and management.

Adult

Primary leiomyosarcoma of bone.

Adequate treatment of primary leiomyosarcoma of bone requires surgical ablation with the goals being those for any malignant tumor of bone--eradication of the lesion and preservation of as much function as possible. Careful preoperative staging will determine whether amputation is necessary or whether successful limb-saving resection is possible.

Aged

Intraosseous ganglion cysts.

An illustrative case report of intraosseous ganglion cyst is presented. Intraosseous ganglion cysts are uncommon, juxta-articular, and benign. They are thought to arise from an intramedullary metaplastic event. Intraosseous ganglia are most common in middle-aged patients. They usually involve the tibia but also are located in other skeletal sites. The lesion is typically epiphyseal and appears benign. It is successfully treated with curettage and bone graft if it is symptomatic or progressively increasing in size. It is important to avoid extensive surgical procedures. Recurrence is unlikely.

Bone Cysts

Bone banks and allografts in community practice.

The increasing volume of orthopaedic reconstructive procedures requiring replacement of bone stock justifies the initiation of programs of bone banking in community hospitals. Provided that strict criteria are followed to assure rigorous screening of donor bone and the reliable preservation of bone graft material, community banking is safe and cost-effective. Banked allograft bone can be used successfully in a wide variety of orthopaedic procedures performed in community hospitals. In general, the best uses are filling bone cavities, buttressing, and augmenting the quantity of autograft bone. In revision reconstructive surgery of the hip, bank bone is used to replace bone stock in protrusio, acetabular dysplasia, and proximal femoral deficiency. The best and most common indication for the use of bank bone in tumor surgery is after curettage or excision of benign lesions. Allografts may be used to reconstruct bony defects after excision of malignant tumors and in the surgical treatment of metastatic disease. These instances require larger bone bank facilities than those commonly available in a community hospital setting. Medicolegal considerations related to bone banking and the use of allografts in community practice include the regulatory requirements outlined in the UAGA, questions concerning negligence liability, and theories of strict product liability. Overall, good medical practice and obtaining informed consents will minimize legal risks related to bone banking and transplantation in a community setting.

Bone Transplantation

Comparison of replacement prostheses for segmental defects of bone. Different porous coatings for extracortical fixation.

The extent of extracortical bone-bridging and ingrowth into porous-coated prostheses for the stabilization of segmental defects was studied in a canine model. Initial fixation of the implant was achieved using bone cement. Autogenous bone grafts were applied over the porous-coated segmental portion of the prosthesis to stimulate the ingrowth and formation of bone. At twelve weeks, bone-bridging and ingrowth occurred uniformly in both the titanium fibermesh and the cobalt-chromium-molybdenum beaded prostheses. Maximum formation of osseous tissue over the implants occurred at two to four weeks. More bone formed in the posterior aspect of the prosthesis. At twelve weeks, 26 per cent of the porous space of the titanium fibermesh prosthesis and 47 per cent of the porous space of the cobalt-chromium-molybdenum beaded prosthesis were filled with bone. The torsional strength and stiffness of the prosthetic midsection that contained a conical coupling joint were increased significantly due to bone-bridging and ingrowth. The cortical bone that was apposed to the segmental prosthesis showed an increase in porosity. The use of bone cement did not appear to impede new-bone formation extracortically. The initial stability of the implant and the application of sufficient autogenous bone grafts are two important factors that contribute to the ultimate stable fixation of an implant by extracortical bone formation.

Animals

Prosthetic replacement of the femoral head for fracture of the femoral neck in patients who have Parkinson disease.

A retrospective study was performed of forty-nine patients (fifty fractures of the femoral neck) who had Parkinson disease and who had had an endoprosthetic replacement of the femoral head. The average age of the patients was seventy-four years (range, forty-seven to ninety-two years). All of the fractures were Garden Stage III or IV. An anterolateral surgical approach was used in twenty-five hips; a posterior approach, in twenty hips; and a transtrochanteric approach, in five hips. An adductor tenotomy was required in five patients to release an adduction contracture. Ten patients died by the sixth postoperative month. The remaining thirty-nine patients were followed for a minimum of two years (average, 7.3 years). Common postoperative complications were infection of the urinary tract (20 per cent) and pneumonia (10 per cent). There was only one dislocation. At the time of writing, nineteen (80 per cent) of the surviving patients could walk.

Aged