In vitro and in vivo study on the effect of autogenous cancellous bone and intramedullary polymethylmethacrylate on allograft construct strength

An in vitro study was performed to compare the effects of augmenting interlocking nails of one of two diameters (5 or 6 mm) with intramedullary polymethylmethacrylate. Subsequently, an in vivo study was performed to compare the effects of augmenting the interlocking nail with five combinations of intramedullary polymethylmethacrylate and autogenous cancellous bone applied to the periosteal surface or within the medullary canal. Dogs were killed 6 months after the procedure for biomechanical evaluation of the femora in axial compression, mediolateral and craniocaudal bending, and torsion. Results from the in vitro study at the proximal osteotomy indicated the 6-mm interlocking nail with intramedullary polymethylmethacrylate had greater stiffness than the 5-mm interlocking nail without it (p < 0.05). At the distal osteotomy, regardless of the diameter of the interlocking nail, the addition of intramedullary polymethylmethacrylate increased stiffness (p < 0.05). Results from the in vivo study indicated greater global construct stiffness with an interlocking nail alone, an interlocking nail augmented with intramedullary polymethylmethacrylate and cancellous bone at the periosteal surface, and an interlocking nail augmented with cancellous bone within the medullary canal and at the periosteal surface (p < 0.05). At the osteotomy level, the interlocking nail augmented with intramedullary polymethylmethacrylate and cancellous bone at the periosteal surface had greater stiffness than did an interlocking nail alone or an interlocking nail augmented with either intramedullary polymethylmethacrylate, cancellous bone within the medullary canal, or cancellous bone at the periosteal surface (p < 0.05) but produced the same results as an interlocking nail augmented with cancellous bone within the medullary canal and at the periosteal surface. The results suggest that augmenting interlocking nail fixation with intramedullary polymethylmethacrylate by itself offers no advantage but that a combination of intramedullary polymethylmethacrylate and cancellous bone at the periosteal surface improves structural properties at 6 months.

CT and MRI evaluation of musculoskeletal infection

While the plain film and nuclear medicine bone scan are still the traditional imaging modalities used in the evaluation of musculoskeletal infection, the cross-sectional imaging modalities, computed tomography (CT) and magnetic resonance imaging (MRI), have become critical in the delineation of many types of musculoskeletal infection. In particular, the evaluation of soft tissue infections, including cellulitus, myositis, fasciitis, abscess, and septic arthritis are often best evaluated by MRI or CT due to their excellent anatomic resolution and soft tissue contrast. Even in osseous infection, CT and MRI can give better anatomic delineation of the extent of infection. In cases where the plain film and nuclear medicine bone scan findings are complicated due to previous surgery, trauma, or underlying illness, the anatomic resolution and soft tissue contrast provided by MRI and CT are often necessary to determine if underlying infection exists. MRI's visualization of the bone marrow allows for the sensitive detection of osteomyelitis, although specificity for the diagnosis of osteomyelitis is aided by other findings, including cortical destruction. The CT and MRI findings in the spectrum of musculoskeletal infections are discussed and contrasted, and pitfalls in their evaluation of musculoskeletal infection are described.

The short-term effects of cisplatin chemotherapy on bone turnover

Cisplatin is an effective agent in the treatment of osteosarcoma of bone but little is known of its effects on normal bone turnover. Twenty-four dogs divided into three study groups were used to study the effect of cisplatin on normal bone turnover at the distant site of surgery. Group 1 served as the control group, group 2 received four cycles of cisplatin every 3 weeks before the surgery, and group 3 received four cycles postoperatively. The bone turnover rate was evaluated by measuring levels of systemic bone markers, osteocalcin, alkaline phospohatase, urine pyridinoline cross-links, and by determination histomorphometric indices. Histomorphological analysis showed poor correlation on bone formation with systemic bone markers at distant sites of surgery. Histomorphometrically normal bone turnover was affected by administration of cisplatin, but the effect was temporary, late, and less significant than what occurred at the surgical site. Our data showed that significant effects of cisplatin are observed at the site of active cellular induction and proliferation, such as implant-host interface, and less effects are seen at the sites of normal bone turnover.

Skeletal system: biomechanical concepts and relationships to normal and abnormal conditions

The human skeleton is a remarkable organ that is uniquely designed to provide structural support and to house the body's hematopoietic system and mineral reservoirs. Seven concepts that will assist the clinician in understanding skeletal function are (1) material properties of bone, (2) stress and strain, (3) bending moments and torsional loads, (4) area moments of inertia, (5) fatigue and catastrophic failure, (6) Wolff's law, and (7) stress risers and open section effect. For example, as the modulus of a bone, a measure of stiffness decreases as in Padget's disease or fibrous dysplasia and the same levels of stress will cause greater deformations. The sum of these principles also explains the torus fracture (ductility), fracture of the olecranon by contracting tricep muscle (tensile loading), osteoporotic compression fracture of the spine, and the other biomechanical lesions that are encountered. Understanding these basic biomechanical principles can help physicians comprehend neoplastic processes and fractures that are the metabolic responses of the skeleton to stress and that appear on the radionuclide bone scan.

Effect of cisplatin chemotherapy on extracortical tissue formation in canine diaphyseal segmental replacement

The reconstruction of large bone and joint defects after the resection of malignant tumors remains a major challenge. Chemotherapy has significantly lowered the risk of metastasic disease, but complications associated with reconstructive techniques continue to result in late morbidity. In the present study, biomechanical torsion testing, gait analysis, and histomorphometric and scanning electron microscopic evaluations of 24 dogs were used to examine the effects of preoperative and postoperative administration of cisplatin on the biologic fixation of a porous-coated segmental replacement prosthesis. The chemotherapy consisted of four cycles of cisplatin administered at a dosage of 75 mg/m2 preoperatively or postoperatively. The healing was enhanced by use of an autogenous corticocancellous bone graft. The graft was placed evenly around the prosthesis and the adjacent femoral cortex. Mechanical analyses of torsional stiffness, yield strength, and maximum strength revealed no statistically significant differences between the groups at 12 weeks. Such lack of difference was mainly due to the penetration of highly organized fibrous tissue into the porous surface; this provided strong fixation of the implant to bone even in the absence of bone ingrowth. Although bone ingrowth into the prostheses was not affected, electron microscopic, histomorphometric, and radiologic analyses showed a clear difference in the formation of new bone around the prosthesis. Preoperative chemotherapy did not alter the formation of new bone, but specimens from animals treated postoperatively with cisplatin showed significantly less bone graft resorption and less new bone formation. Hence, the effect of cisplatin administration caused only a temporary delay, not a permanent effect, on extracortical capsule formation. The formation of extracortical bone and soft tissue might prevent debris-incised osteolysis and, therefore, prevent late complications by forming a tight capsule around the bone-prosthetic interface.

Benign and malignant musculoskeletal masses: MR imaging differentiation with rim-to-center differential enhancement ratios

PURPOSE

To assess the diagnostic potential of the rim-to-center differential enhancement ratio in the magnetic resonance (MR) imaging differentiation of benign from malignant musculoskeletal masses.

MATERIALS AND METHODS

Dynamic gadolinium-enhanced fast multiplanar spoiled gradient-recalled acquisition in the steady state imaging was performed to evaluate 17 one and soft-tissue masses (10 malignant, seven benign) in 14 patients. The rim-to-center differential enhancement ratio was determined from images at the maximal enhancement rate. The difference in differential enhancement ratios between benign and malignant masses was evaluated and compared with the maximum rate of enhancement for each mass.

RESULTS

Nine of 10 malignant masses showed rapid rim enhancement with delayed central fill-in. This enhancement pattern was absent in benign masses. The average rim-to-center differential enhancement ratio was 0.64 +/- 0.26 for malignant masses and -0.16 +/- 0.33 for benign masses (P < .001). This difference was statistically significant. The average maximum rate of enhancement was 3.41%/sec +/- 2.20 for malignant masses and 2.74%/sec +/- 2.46 for benign masses (P > .05).

CONCLUSION

Intratumoral enhancement patterns of malignant and benign masses differ because of differences in vascular architecture. These preliminary results suggest that the rim-to-center differential enhancement ratio has potential as an additional parameter for the MR imaging differentiation of indeterminate musculoskeletal masses.

Special problems in limb-salvage surgery

Limb-salvage surgery is a safe and effective treatment for malignancies of the musculoskeletal system. Careful evaluation and planning are necessary to avoid both early and late complications. Biopsy must be carefully performed to avoid unnecessary contamination and to obtain adequate tissue for an accurate diagnosis. Pathologic fractures present both a diagnostic and a therapeutic challenge, and evaluation strategies depend on the age of the patient. Treatment of a pathologic fracture depends on the location and the histology of the lesion and many host factors. Limb salvage may or may not be indicated. Instability is another problem with certain limb-salvage situations, e.g., when it is necessary to resect the scapula. Various approaches may obviate the problem. The salvage of failed limb-salvage procedures requires careful evaluation and planning. Patients with infections and local recurrences often require amputation surgery. Correctable problems following failed allograft reconstructions include collapse of the articular cartilage, joint instability, nonunion, and fracture of the allograft. Correctable problems following prosthetic arthroplasty include aseptic loosening, prosthetic fracture, and polyethylene wear. Approximately two thirds of patients with failed limb-salvage procedures will obtain a functional limb following revision surgery. Attention to these special problems may allow for greater success with limb-salvage surgery.

Development of a canine chemotherapeutic model with ifosfamide

The purpose of this study was to develop a canine experimental model for neoadjuvant chemotherapy of primary bone tumors with ifosfamide, which is safe and clinically relevant for use in human beings with bone tumors. Our study was divided into two steps, each with four dogs. In the first step ifosfamide was administered for 4 consecutive days in three cycles with 3-week intervals between each cycle. For this first step a daily dosage of 300 mg/m2 of body surface resulted in only moderate leukopenia, whereas a daily dosage of 450 mg/m2 caused severe leukopenia. Therefore, to determine the maximal dose tolerable and to verify the results from step 1, we administered the higher daily dosage of 450 mg/m2 in step 2 for four successive cycles with 3-week intervals. In each step one dog died acutely after the first cycle of chemotherapy. In addition during step 2 one dog died of overwhelming sepsis after the second cycle of ifosfamide. The remaining five dogs survived without other appreciable laboratory abnormalities. Neither hematuria nor proteinuria was observed throughout the course of study, and relevant findings were not observed at autopsy. We determined that 450 mg/m2 was the maximal tolerated dosage of ifosfamide for our regimen, with the dose-limiting factor being myelosuppression, specifically leukopenia. Using this canine model, we can estimate the effect of ifosfamide on bone graft incorporations and the fixation of biologic prostheses that is clinically the most important aspect of limb salvage surgery.

Clinicopathologic features and treatment of osteoid osteoma and osteoblastoma in children and adolescents

Benign bone-forming tumors are common in children. Careful radiographic imaging is necessary to plan surgical treatment. Careful histologic study is necessary to distinguish osteoblastoma from more aggressive tumors. Osteoid osteoma should be considered when the child or adolescent presents with pain in an extremity or along the spine.

Survival after pulmonary metastasectomy in soft tissue sarcoma. Prognostic factors in 214 patients

This retrospective study examines prognostic factors for post-metastasectomy survival in soft tissue sarcoma patients. Between 1976 and 1992, 274 consecutive patients (median age 49 [7-96] years) with pulmonary metastatic soft tissue sarcoma of the extremity or trunk wall (31 at presentation) were managed at the Mayo Clinic. 214 underwent pulmonary metastasectomy and 163 of these also received adjuvant chemotherapy. There were 195 local excisions, 14 lobectomies, and 5 pneumonectomies. 90 patients had solitary metastases, 184 patients had 2 or more metastases. 31% of patients had MFH tumors and 88% of all tumors were high grade. Median follow-up for survivors was 8 (2-21) years. 5-year overall survival after metastasectomy was approximately 40% (cf. 20% for non-metastasectomy). Age > 50, MFH tumors, > or = 2 metastases, metastasis size > 2 cm, metastasis-free period < or = 18 months, and the use of adjuvant chemotherapy were univariately unfavorable factors. Size of metastasis > 2 cm, number of metastases > or = 2, and metastasis-free interval < or = 18 months were independently unfavorable for survival. In a prognostic system, patients with 0 risk factors had a 60% 5-year survival, those with 1, 2, or 3 of these factors had 30%, 20% and 0% survival, respectively.

Differentiation of benign and malignant musculoskeletal tumors: potential pitfalls with MR imaging

Magnetic resonance (MR) imaging is the most sensitive and accurate imaging technique for evaluation of musculoskeletal tumors. With increasing clinical experience, however, an overlap between the classic characteristics of benign and malignant tumors is frequently observed. In a prospective analysis of 87 consecutive cases of musculoskeletal tumors, the malignancy of skeletal lesions was correctly assessed with MR imaging in 55% of the cases. In 39% of the cases, the malignancy of skeletal lesions was overestimated with MR imaging. Correlation with plain radiography is extremely important in such cases and would have resulted in correct assessment of 73% of the skeletal lesions. For soft-tissue lesions, a large variability is found in the benign versus malignant appearances of lesions on MR images, with poor correlation between classic benign characteristics and the benignity of the lesion (17% of cases). The exceptions are hemangiomas and lipomas, which have characteristic appearances on MR images. Knowledge of potentially misleading appearances of musculoskeletal tumors on MR images allows more accurate diagnosis of such tumors.

Orthopaedic management using new devices and prostheses

The goals of treatment for patients with metastatic disease are control of pain and maintenance of function. Prosthetic arthroplasty is a useful technique for selected indications. Specific indications include (1) reconstruction of large destructive areas that are not amenable to internal fixation, (2) salvage of failed internal fixation devices, and (3) salvage of lesions in which there are no radiotherapy options to prevent disease progression. Custom modular devices allow resection of varying segments of the skeleton. Immediate rigid fixation is achieved with cemented intramedullary stems. Patients are allowed to bear full weight as tolerated immediately postoperatively. A custom modular diaphyseal segmental replacement system allows resection of large diaphyseal lesions and immediate fixation. The complication rate is low after arthroplasty.

Osteosarcoma of the diaphysis of long bones: clinicopathologic features and treatment of 51 cases

Of 1000 osteosarcoma cases recorded in the Mayo Clinic records, approximately 7% of the lesions occurred in the diaphysis of long bones, mostly in the femur, tibia, and humerus. The average age of the patients with these lesions was 28 years (range: 8 to 67). The duration of their symptoms before diagnosis was greater than that for patients with conventional osteosarcoma in the metaphysis. In approximately 20% of the cases, the radiographic appearance mimicked that of Ewing's sarcoma. Amputation surgery was the major form of treatment. The 2-, 5- and 15-year survival was 42%, 29%, and 20%, respectively.

Protected early motion versus cast immobilization in postoperative management of ankle fractures

Sixty-one active-duty military personnel with operatively treated ankle fractures were randomized into two postoperative immobilization regimens: Group I--six weeks short-leg cast, nonweight-bearing; Group II--six weeks removable orthosis, nonweightbearing. Group I began physical therapy at six weeks postoperatively, and Group II began physical therapy within the first postoperative week. Objective measurements of swelling, strength, range of motion, and functional tests were examined. Subjective scores of pain, function, cosmesis, and motion were recorded. Patients in Group II (early mobilization) had significantly better subjective scores at three and six months postoperatively; however, time to return to duty was not significantly different. Objective tests of swelling, strength, range of motion, and functional tests were not significantly different at three months postoperatively for either group. Early mobilization in a removable orthosis, while not objectively altering the postoperative course, provides a safe, preferable method of treatment in the reliable and cooperative patient.

Medial meniscal cyst of the knee simulating a solitary bone lesion. A case report and review of the literature

Meniscal cysts are common lesions, but extensive bony changes arising from these cysts are exceedingly rare. These changes are usually erosive defects about the tibia. Dull pain with an associated mass are classic findings. Magnetic resonance imaging is useful in making the diagnosis and arthroscopic management yields excellent results. A 47-year-old man developed a symptomatic medial meniscal cyst that invaded the medial femoral condyle simulating a solitary bone lesion. Magnetic resonance imaging revealed the contiguous nature of the cyst with the meniscus. Arthrotomy with cyst excision was required in this case and led to the amelioration of symptoms.

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.

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.

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)