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Biomedical subjects

F H Sim

Publications and source records attributed to F H Sim.

At least 91 records · Page 5Linked to original sources
PubMed1994

Tendons attached to prostheses by tendon-bone block fixation: an experimental study in dogs.

To develop a method of tendon attachment to a metallic endoprosthesis, we evaluated fixation strength, clinical function of the tendon, and morphological changes in an experimental model. The canine supraspinatus tendon was removed from the greater tubercle of the humerus and attached to a titanium prosthesis. In 12 animals, the bone block underlying the tendon insertion was preserved and attached in one limb; the soft part of the tendon was attached directly to the prosthesis in the contralateral limb. Fixation strength was evaluated after 16 weeks of in vivo implantation (12 specimens) and compared with the in vitro fixation strength (12 specimens) and with intact normal controls (six specimens from cadavera). Function of the tendon in vivo was evaluated by force-plate analysis (at 3-week intervals). All specimens were evaluated histologically. Sixteen weeks after surgery, the tendon-bone block attachment was significantly stronger (mean, 16%) than the direct tendon attachment and not significantly different from the normal control, and the direct tendon attachment was significantly weaker (mean, 68%) than the normal control. There was significantly more weight-bearing on the limbs with a tendon-bone block attachment than on the limbs with a direct tendon attachment at both 3 and 6 weeks postoperatively. Both front legs showed increased weight-bearing with time, but the differences were not statistically significant. Anchorage by tissue ingrowth to the titanium prosthesis was found consistently--there was bone ingrowth in the tendon-bone block attachments and fibrous tissue ingrowth in the direct tendon attachments. When a bone block was preserved, the strength and stiffness were comparable with those of a normal tendon insertion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Osteoblastoma: clinicopathologic study of 306 cases.

The clinical, radiologic, and pathologic features of 306 osteoblastomas were analyzed. Seventy-five were Mayo Clinic cases and 231 were from consultation files. Males outnumbered females two to one. The age range was 6 months to 75 years (mean age, 20.4 years). The vertebral column including the sacrum was the most frequent site (32%). Pain was the usual complaint and neurologic findings were associated with vertebral tumors. Although most tumors were well circumscribed, cortical expansion and destruction were common radiographic findings (39%), and 12% had features suggestive of malignancy. Large, epithelioid osteoblasts were seen in 24% and were the predominant cellular element in 10%. A distinctive epithelioid multifocal pattern was recognized. Recurrence rates were 16% (Mayo Clinic cases) and 21% (consultation cases). Tumors involving the central neuraxis were associated with greater morbidity and mortality. Aggressive behavior is within the biologic spectrum of osteoblastomas, and histopathology alone does not appear to be a reliable predictor of aggressiveness. The most important differential diagnosis is osteosarcoma.

Adolescent↗
PubMed1994

A review of corrective osteotomies for deformity in Paget's disease.

Corrective diaphyseal osteotomies for pagetic deformities may require a long time for union. However, metaphyseal osteotomies healed uneventfully. The use of plate fixation was associated with a lower rate of complications in diaphyseal osteotomies in Paget's disease. External fixation was associated with the highest rate of complications. Medical treatment did not seem to minimize blood loss or expedite union rate or time to union.

Humans↗
PubMed1994

Parosteal osteosarcoma. A clinicopathological study.

The records of 226 patients (sixty-seven who were managed at our institution and 159 who were identified from the consultation files) who had had a parosteal osteosarcoma were reviewed. The criteria for diagnosis were that, roentgenographically, the lesion had arisen from the surface of the bone and that, histologically, the tumor was well differentiated (Grade 1 or 2); it was characterized by well formed osteoid within a spindle-cell stroma; and, when there was medullary involvement, less than 25 per cent of the medullary cavity was affected. Dedifferentiation was more common (16 per cent of the patients) than previously reported and was associated with a poor prognosis. Cross-sectional imaging studies demonstrated medullary involvement in 22 per cent of the patients, an unmineralized soft-tissue mass peripheral to the mineral component in 51 per cent, and adjacent soft-tissue invasion in 46 per cent. In contrast to the findings in our previous studies, medullary involvement was not a poor prognostic factor. At an average of thirteen years (range, two to forty-one years), eleven of the sixty-seven patients who were managed at our institution died of the tumor; ten of these patients had a dedifferentiated tumor. Statistical analysis of the thirty-nine patients who had had the primary treatment at our institution revealed that incomplete resection was associated with an increased risk of local recurrence and that dedifferentiation markedly increased the risk of metastasis.

Adolescent↗
PubMed1993

Prognostic significance of spontaneous tumour necrosis in osteosarcoma.

Preoperative chemotherapy is an integral part of the management of osteosarcoma, and the extent of tumour necrosis found at operation is an important prognostic variable. Knowledge about spontaneous, pretherapy necrosis is difficult to obtain but provides important quantitative information about the necrotic effect of chemotherapy. Using three different methods, we studied spontaneous tumour necrosis in 20 localized intramedullary osteosarcomas of the distal femur diagnosed between 1963 and 1972. All patients received surgical treatment only. All six patients with spontaneous necrosis involving more than 20% of tumour died. Five of 14 patients with necrosis amounting to less than 20% were long-term, disease-free survivors. The extent of necrosis was independent of tumour size. Two semiquantitative methods of evaluation were easily applied and reproducible. Spontaneous necrosis in untreated osteosarcomas occurs frequently; extensive necrosis may indicate a rapid clinical course. Tumour necrosis can be quantified reliably in clinical work.

Adolescent↗
PubMed1993

Chondroblastoma.

Chondroblastoma of the bone is a benign tumor that has well-characterized radiographic and histologic features. It tends to affect the epiphyseal ends of long bones in men during the second and third decades of life. The tumor is located more frequently at other sites in older patients. The treatment of choice is complete curettage with bone grafting, which in our series provided local control in 82% of patients at 2 years' follow-up. Recurrent tumors usually can be treated in the same manner.

Adolescent↗
PubMed1993

Giant-cell tumours of the spine.

Between 1955 and 1989 we treated 24 patients (17 women and seven men) with giant-cell tumours of the spine at the Mayo Clinic. Their mean age was 30 years and the mean follow-up time was 12.4 years. Pain was the presenting symptom in all and half had a neurological deficit. The cervical, thoracic, and lumbar spines were equally involved. The tumours recurred in five of the 14 patients treated by one-stage surgery and in five of the ten treated by two-stage surgery. Seven patients received adjuvant radiotherapy, one for the primary lesion and six for recurrent lesions. Surgical management was by curettage or en bloc excision depending on the location and the extent of the tumour. Because of the risk of sarcomatous transformation, radiation therapy should be reserved for patients with incomplete excision or for those with local recurrence.

Adolescent↗
PubMed1993

Ewing sarcoma of the pelvis. Clinicopathological features and treatment.

The results of treatment in twenty-seven patients who had a Ewing sarcoma of the pelvis were reviewed. Six patients had had metastatic disease at the time of the diagnosis. The three-year actuarial survival of these patients was 17 per cent (95 per cent confidence interval, 8 to 52 per cent). Of the twenty-one remaining patients, thirteen had received chemotherapy and radiation therapy to the primary lesion and eight had had chemotherapy and operative resection, with or without radiation therapy. The actuarial five-year over-all survival was 25 per cent (95 per cent confidence interval, 6 to 51 per cent) in the group that had had radiation without a resection and 75 per cent (95 per cent confidence interval, 31 to 93 per cent) in the group that had had a resection (p < 0.005, log-rank method). The actuarial over-all five-year survival was 45 per cent (23 to 65 per cent) for all patients who had had localized disease when first seen. Actuarial local failure analysis (the censoring of patients who died without evidence of local failure before the two-year follow-up examination) revealed a rate of local failure of 44 per cent (14 to 79 per cent) in the group that had been treated with chemotherapy and radiation alone compared with 13 per cent (0 to 53 per cent) in the patients who had had a resection, but this difference was not significant (p > 0.25, log-rank method).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Treatment of giant-cell tumor of the pelvis.

Nineteen patients who had a giant-cell tumor of the pelvis were managed from 1944 through 1989. Thirteen of the patients were in the third or fourth decade of life. The ileum was involved in thirteen patients; the pubis, in two; the ischium, in three; and the pubis and ischium, in one. Five patients who had an initial Stage-II (active) lesion were managed with curettage; in one of the five, a local recurrence developed at twelve months, and the other four had no evidence of disease from nine to forty-six years after the curettage. Eight patients who had a Stage-III (aggressive) lesion were managed with resection of most of the lesion followed by curettage of any remaining positive margins; four of the eight also received adjuvant irradiation. None of the eight had a local recurrence; six had no evidence of disease from eight to twenty-seven years after the operation, one died because of a metastatic post-radiation sarcoma thirteen years after the operation, and one was asymptomatic but had pulmonary metastases three years after the operation. Four patients who had a Stage-III recurrent local tumor when they were first seen were managed with hemipelvectomy, wide resection, resection and curettage, and curettage and arthroplasty (one procedure each). Three had no evidence of disease seven to twenty years after the operation and one had died because of a post-radiation metastatic osteosarcoma eight years after the operation. Two patients who had Stage-III disease were managed with external beam radiation alone. One had no evidence of disease twenty-six years later. The other had a recurrence one year later, which was treated with additional irradiation; a second recurrence was treated with curettage and bone-grafting. Twenty-eight years after the initial radiation treatment, this patient had no evidence of disease. External beam irradiation was used for a total of eight patients; a post-radiation sarcoma developed in two.

Adolescent↗
PubMed1993

A comparative analysis of subchondral replacement with polymethylmethacrylate or autogenous bone grafts in dogs.

A comparative analysis was made of subchondral replacement with polymethylmethacrylate and autogeneic bone grafts in defects in the medial femoral condyles of dogs. The defect produced a 50% reduction in subchondral stiffness. An in vitro preparation helped establish that subchondral stiffness returned to normal after reconstruction with polymethylmethacrylate. The in vivo model demonstrated a reduction in subchondral stiffness in both groups at three weeks, but the bone grafted side returned to normal and the methylmethacrylate side recovered to 79% of the control at 12 weeks. There were no deleterious effects on the articular cartilage in either group when analyzed histologically and biochemically. A marked increase in new bone formation and subchondral porosity was found in the polymethylmethacrylate groups. This study supports the clinical use of subchondral polymethylmethacrylate after the exteriorization and curettage of benign bone tumors such as giant cell tumors.

Animals↗
PubMed1993

[Resection of pelvic sarcomas. Reconstruction techniques without use of endoprostheses].

Advances in preoperative imaging techniques and surgical expertise now permit limb sparing resections of pelvic sarcomas to be performed in appropriate patients with an acceptable risk of local recurrence. Reconstruction of the skeletal defect remains, however, problematic. Many techniques have been employed, all with advantages and disadvantages. Arthrodesis for the unstable pelvis has been our preferred reconstructive procedure. When successful, we find this a durable and pain-free reconstruction for the young, active patient.

Adolescent↗
PubMed1993

Custom-made segmental femoral replacement prosthesis in revision total hip arthroplasty.

Patients who present with failed total hip arthroplasty and significant proximal femoral bone loss pose a challenging reconstructive problem. When the integrity of the host proximal femur can be salvaged with cortical strut grafts, conventional long-stem femoral components can be used. If there is massive proximal femoral bone loss, hip salvage can be accomplished with a proximal femoral replacement prosthesis or an allograft-prosthesis composite. Although our early results with a proximal femoral replacement prosthesis were good, long-term results reveal a high rate of dislocation and acetabular component loosening, with an overall survivorship of 73% at 11 years. We have, therefore, limited the use of a proximal femoral replacement prosthesis to the elderly and inactive patient. We are encouraged by the preliminary results of total hip arthroplasty with a second-generation, modular, porous-coated, proximal femoral replacement prosthesis. Longer follow-up is required to determine whether these design modifications improve the results of this type of reconstructive procedure in revision total hip arthroplasty.

Adult↗
PubMed1993

Use of allografts following resection of tumors of the musculoskeletal system.

Allografts are an effective method of reconstructing defects following the resection of benign or malignant tumors. The surgeon must carefully plan the procedure in two stages. Stage I involves resection of the tumor with an adequate margin to prevent local recurrence, and stage II involves reconstruction of the limb with a durable and functional technique that has a low risk of morbidity. Allograft reconstructions are technically demanding. The prerequisites to a successful reconstruction include rigid internal fixation of the allograft, competent soft tissues to cover the graft, preoperative and postoperative antibiotic coverage, meticulous hemostasis and postoperative wound drainage to prevent hematoma formation, and protection of the allograft to allow union. Whenever soft-tissue coverage of the graft is in question, local rotational flaps or free microvascular transfers should be used to cover the allograft with healthy muscle. Second surgical procedures, such as revision of necrotic soft-tissue flaps, drainage of hematomas, bone grafting of nonunions, and revision of internal fixation, should be avoided by careful technique at the index operation because additional procedures place the allograft at risk for infection. Further basic science investigations and clinical studies should expand the applications of allograft reconstructions and lower the incidence of complications.

Bone Neoplasms↗
PubMed1993

Soft-tissue sarcomas. Future perspectives.

Although the previous outlook for patients with soft-tissue tumors was poor, in recent years advances have been made in earlier recognition and management of soft-tissue sarcomas. Advances include improved clinical pathologic correlation and clinical staging, as well as improved concept of what constitutes adequate surgical management. In addition, recent advances in surgical adjuvant treatment programs promise better results. Moreover, a better understanding of the biology of cancer and the development of sophisticated techniques of molecular biology should lead to more effective treatment.

Adjuvants, Immunologic↗
PubMed1993

The effects of therapeutic doses of irradiation on experimental bone graft incorporation over a porous-coated segmental defect endoprosthesis.

The incorporation of autogeneic bone graft into a porous coated segmental endoprosthesis after high-dose irradiation was studied in dogs. A mid-diaphyseal defect was surgically created and then reconstructed with a porous-coated segmental endoprosthesis in 16 dogs. Autogeneic bone grafts were placed over the porous-coated regions of the endoprosthesis and at the endoprosthesis-bone junctions to achieve extracortical fixation. In eight dogs, the reconstructed femora were treated with a time-equivalent dose of 5500 cGy, delivered over a five-week period, beginning three weeks after surgery. In eight dogs, which served as the control group, the reconstructed femora were not irradiated. Dogs were killed 12 weeks after surgery, and the reconstructed femora were evaluated clinically, roentgenographically, mechanically, and histologically. Extracortical bone formation and bone ingrowth into the porous-coated segmental endoprosthesis were significantly inhibited by high-dose irradiation. Nonirradiated reconstructed femora had higher maximum torque at the implant-bone junction than irradiated femora. Nonirradiated femora had significantly greater bone ingrowth within the porous space than irradiated femora. Intracortically, irradiated femora had greater unlabeled bone and less porosity as well as more new bone than nonirradiated femora at 12 weeks postsurgery. Extracortically, irradiated femora had greater original cortical bone and less porosity as well as more new bone than nonirradiated femora at 12 weeks postsurgery. Mineral apposition was less in the irradiated femora from the initiation of radiotherapy to the time of killing five weeks after cessation of irradiation.

Analysis of Variance↗
PubMed1993

Giant cell tumor of the sacrum.

Twenty-six patients (18 women and eight men) with giant cell tumors of the sacrum were treated from 1960 through 1986. The mean age of the patients was 29 years. The follow-up duration averaged 7.8 years. A neurologic deficit was present in 88%. Sixteen patients had not had a previous operation. Ten patients were referred for local recurrence. Twenty-one patients had radiation therapy; malignant transformation later occurred in three. Three benign giant cell tumors metastasized to the lungs. The local recurrence rate for patients treated by curettage was 33%. Three patients died of tumor-related complications. At the completion of this study, two patients were alive with disease. The suggested initial treatment is complete curettage. Radiation therapy should be reserved for incomplete resection and local recurrence. Occasionally, patients may require wide resection, which may cause a severe neurologic deficit and compromise spinal stability.

Adolescent↗