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Biomedical subjects

M G Rock

Publications and source records attributed to M G Rock.

At least 55 records · Page 3Linked to original sources
PubMed1993

Mechanical characteristics of proximal femoral reconstruction after 50% resection.

Six techniques of proximal femoral replacement were compared in vitro with the use of compression, bending, and torsional testing in a canine model. One femur of each pair was osteotomized in the midshaft region, and the proximal portion was replaced with one of six techniques. These techniques included (a) a segmental proximal femoral endoprosthesis cemented into the distal femur with no allograft (technique ES); (b) a long-stem endoprosthesis press-fit into an allograft and cemented into the distal femur with a transverse osteotomy (technique AT); (c) the same construct as technique AT, but with a step-cut at the osteotomy (technique AS); (d) a long-stem endoprosthesis interlocked into an allograft and cemented into the distal femur with a transverse osteotomy (technique AI); (e) a short-stem endoprosthesis cemented into an allograft combined with one plate laterally stabilizing the allograft to the distal femur with a transverse osteotomy (technique AP1); and (f) the same construct as technique AP1, but with an additional plate cranially (technique AP2). A long-stem endoprosthesis cemented into the contralateral intact femur served as the control. Techniques that involved a long-stem endoprosthesis and cementing distally (AT, AS, and AI) were more resistant in torsion than the plated replacement techniques (AP1 and AP2). The segmental replacement construct (ES) was equal to or stronger than all other techniques under each testing condition. In torsion, the addition of a step-cut (AS) significantly lowered angular displacement of the reconstruction when compared with the reconstruction with a transverse osteotomy (AT) (p < 0.05). Bones with one-plate fixation (AP1) were significantly weaker in torsional stiffness and maximum torque and in mediolateral bending (p < 0.05) than all other techniques. The addition of a second plate (AP2) increased the mechanical properties of the construct so that it was greater than the one-plate method and was equal to (bending and compression) or still weaker (torsion) than the other techniques. The results indicate that segmental replacement methods and allograft/endoprosthetic composites that involve long-stem endoprostheses fixed with cement are mechanically superior to methods that involve short-stem endoprostheses with single or double plating at the osteotomy sites.

Analysis of Variance↗
PubMed1993

A mechanical comparison of gluteus medius attachment methods in a canine model.

Seven techniques of gluteus medius attachment were compared in vitro in a canine model. Four methods were used for tendon to tendon attachment: (a) two modified Bunnell-Mayer sutures, (b) two Kessler locking loop sutures, (c) two horizontal mattress sutures, and (d) two sutures with a looped suture technique. The two methods of tendon to bone attachment were repair with a 1 cm spiked staple and repair with a spiked washer and screw, and the method of bone to bone attachment involved two figure-eight cerclage wires. The contralateral limb served as a control. Compared with the bone to bone attachment, the four tendon to tendon attachments and the two tendon to bone attachments had significantly less strength (31 and 30% of the ultimate load for bone to bone repair, respectively) and tensile stiffness (24 and 39% of the tensile stiffness for bone to bone attachment, respectively) (p < 0.0001). The control specimens were significantly stronger and stiffer than all specimens (p < 0.05) except those that had bone to bone fixation. There were no significant differences among the four tendon to tendon suture repairs with regard to either strength or stiffness; the values ranged from 28-45% of those of the controls. Among the tendon to bone repairs, fixation with a spiked washer and screw was significantly stronger than that with a spiked staple (p = 0.032), but there was no difference between these two techniques with regard to stiffness.

Analysis of Variance↗
PubMed1993

Thigh injuries in athletes.

The thigh, which consists of the heavily muscled region around the femur, is vulnerable to many types of athletic injury. This review addresses the assessment, prevention, and rehabilitation of both the common thigh injuries associated with participation in sports, such as contusions and myositis ossificans traumatica, and a few relatively uncommon but diagnostically important entities that sports physicians must recognize when an athlete has pain or dysfunction attributable to the thigh. Dividing the thigh into anatomic compartments aids in both differential diagnosis and understanding of the pathomechanics that lead to injury. Rehabilitation is especially emphasized because improper selection of modalities or misuse of exercise can seriously impede or worsen recovery. Conversely, the use of appropriate rehabilitation principles and new concepts in exercise prescription can decrease morbidity and lead to rapid resumption of sports.

Athletic Injuries↗
PubMed1993

Fate of ultrahigh molecular weight polyethylene (UHMW-PE) wear debris in patients with hip implants.

The process of ultrahigh molecular weight polyethylene (UHMW-PE) breakdown, started at the articular surface of the cup, continues in small fragments after generation. An assiduous interaction between the UHMW-PE particles and the host cells leads to oxidative changes of the UHMW-PE and to size reduction of the particles simultaneous with transporting them toward, and finally by, lymphatic or blood vessels. The particles are mobilized by means of enzymatic, extracellular matrix-degrading activity of cells that have phagocytosed them or adhered to them. Together, these characteristics indicate an attempt by the natural cellular immunity system to eliminate the implant wear debris. Macrophages are the main effector cells acting as scavengers; however, excessive amount of the wear debris evokes phagocytic activity of cells other than macrophages as well.

Alloys↗
PubMed1993

Segmental total knee arthroplasty after distal femoral resection for tumor.

Sixty-one patients treated with custom-made segmental total knee reconstruction after resection of a primary tumor of the distal femur were reviewed retrospectively. Two types of implants were used: the Walldius hinge prosthesis (Walldius Group, n = 45) and the Kinematic rotating hinge prosthesis (Kinematic Group, n = 16). The mean periods of follow-up observation were 6.4 years for the Walldius Group and 2.3 years for the Kinematic Group. The overall functional results in the Walldius Group were excellent in 7%, good in 26%, fair in 25%, and poor in 42% of the patients. Roentgenographic analyses showed that 50% of the patients had bony resorption, 33% had interface loosening, and 10% had prosthetic stems that were broken at the time of last follow-up evaluation. Forty-two complications occurred in 34 patients who needed additional surgical treatment. Nine of the prostheses in the Walldius Group failed (20%), and 27 of the complications (64%) associated with the use of the Walldius prosthesis occurred in the first three years after implantation. Nineteen Walldius prostheses (42%) were revised or removed for reasons other than local recurrence. The overall functional results of the Kinematic Group were as follows: excellent in 25%, good in 44%, fair in 25%, and poor in 6% of the patients. Roentgenographic analysis showed that there was no change in bone on 81% of the discharge roentgenograms, that there were no radiolucent lines in 87% of the prosthetic replacements, and that there were no radiolucent lines less than 2 mm thick on the roentgenograms. None of the Kinematic rotating hinge prostheses required revision, except one with a patellar button fracture, which was revised without compromising the functional results. Four complications occurred in three patients in the Kinematic Group, and two of them required surgical treatment. The patients with the Kinematic rotating hinge prosthesis had better early functional and roentgenographic results and fewer complications.

Adolescent↗
PubMed1992

Benign giant-cell tumor of bone with pulmonary metastases: clinical findings and radiologic appearance of metastases in 13 cases.

Tumors that metastasize are considered "malignant" by definition. However, benign giant-cell tumor of bone is an exception because of the potential for histologically benign pulmonary metastases, a fact seldom emphasized in the radiologic literature. We therefore report our experience with 13 cases of pulmonary metastasis among 475 patients (prevalence, 3%) in whom benign giant-cell tumor of bone was diagnosed before 1990 at our institution. Five (38%) of the 13 primary bone tumors were located in the distal radius. Local recurrence at the site of the primary bone tumor tumor occurred in seven patients (54%) before pulmonary metastases developed. The mean interval from the diagnosis of the primary bone tumor to the onset of pulmonary metastasis was 3.8 years, with a maximum of 10.7 years. Fifty-four percent of the patients (7/13) had pulmonary metastases 3 years after diagnosis of the primary bone lesion, and 92% (12/13) had pulmonary metastases 7.5 years after diagnosis. Overall mortality rate directly due to giant-cell tumor and its metastases was 23%. On chest radiographs and CT scans, pulmonary metastases appeared as rounded, nodular opacities of homogeneous density, ranging from 0.5 cm to 8.0 cm in diameter. Peripheral regions of the lungs were involved in 85% of the cases and basilar regions in 62%. Our study shows that benign giant-cell tumor of bone can produce pulmonary metastases, that metastases most often occurred with recurrent local disease and distal radial lesions, that the prognosis was relatively favorable, and that such metastases had no distinguishing radiologic features.

Adult↗
PubMed1992

Pathologic fractures of the acetabulum and the pelvis.

Metastatic involvement of the pelvis, and in particular the acetabulum, is a common finding among patients with metastatic osseous disease. With involvement of the joint surfaces, specifically the hip and sacroiliac joints, marked compromise of function can occur. With advances in imaging and the evolution of surgical reconstructive alternatives, most of these patients can be rendered pain-free and functional by transferring weight distribution onto more stable elements of the hemipelvis. Reconstruction must be feasible and in the best interests of the patient. The decision to proceed represents a collective opinion of the patient, oncologist, and surgeon.

Acetabulum↗
PubMed1991

Radial shortening osteotomy for treatment of Kienböck's disease.

Sixteen patients who had radial shortening osteotomy for treatment of Kienböck's disease were reviewed. Ulnar minus variance averaged 3.3 mm. All patients had conservative management that failed. Six were stage II, six were stage III, and four were stage IV. Average follow-up was 4.5 years. In all patients osteotomies united within 3 months. Thirteen patients were totally relieved of pain, and three had mild pain. Motion in the dorsal palmar plane improved, on average, 15 degrees. Grip strength increased 20% to 30% after the operation. Follow-up radiographs did not show continued collapse of carpal height or disease progression except in one patient. No radiographic evidence of degenerative changes at the distal radioulnar joint materialized. As a safe, reliable, and consistently successful method of managing Kienböck's disease, we strongly recommend radial shortening. Excluding the rare extended stage IV disease in which midcarpal arthritis with or without intercarpal instability is present, we have successfully applied this technique to all stages of Kienböck's disease. We recognize that further collapse and progression of disease may occur in stage III and IV disease, as was evident in one patient 5 years after osteotomy.

Adult↗
PubMed1991

Arthroscopic débridement of the knee for osteoarthrosis.

To evaluate outcome after arthroscopic débridement, the records of 171 patients with osteoarthrosis of the knee were reviewed. All patients were unresponsive to conservative management and were treated arthroscopically. Procedures included lavage, meniscectomy, chondrectomy, removal of free bodies and removal of limited osteophytes. Outcome assessment was retrospective, evaluating the need for further surgery, control of pain, improved function and patient satisfaction. Sixty-five percent of patients felt their symptoms were improved. There was excellent control of pain in 38% and improved function in 22%. Subsequent surgical procedures were required in 12% at an average follow-up of 25 months. No factors were identified that correlated with the outcome, including the extent of degenerative changes and of débridement and patient profile. Arthroscopic débridement is a temporizing procedure with good patient satisfaction. Marked, but unpredictable, improvement in symptoms is seen in one patient out of three.

Adult↗
PubMed1988

Incidence, investigations and staging of soft-tissue sarcoma.

Soft-tissue sarcomas account for only 1% of all malignant lesions. The Canadian Sarcoma Group encourages the investigation and management of these tumours at tertiary institutions, where a multidisciplinary team can handle the complex problems. Staging of these tumours implies accurate anatomic determination of the extent of disease, the histogenesis and grade of the tumours and the presence of regional or distant metastases. Arteriography, computed tomography and magnetic resonance imaging can accurately define the tumour before biopsy. The biopsy should be muscle-splitting to minimize contamination of additional compartments and should allow inclusion of the biopsy site at definitive surgical resection. It should be done at the institution where definitive management will be performed. Regional lymph-node involvement can be detected using magnetic resonance imaging or gallium scanning, whereas for distant metastases, specifically of lung, computed tomography is the method of choice. To date no one staging system for soft-tissue sarcomas has been universally accepted. A hybrid, encompassing the advantages of each system, is being formulated.

Biopsy↗
PubMed1988

Giant-cell tumour of the sacrum in a child.

Giant-cell tumours rarely are seen in children before epiphyseal fusion occurs and such tumours in the spine are uncommon. The authors report the case of a giant-cell tumour of the sacrum that developed in a 12-year-old girl before epiphyseal fusion. Embolization with activated microfibrillar collagen relieved her symptoms and was carried out twice before progression of the tumour necessitated radiotherapy. Giant-cell tumours of the spine are particularly difficult to manage since the accepted treatment for such tumours at other sites is wide resection, excisional curettage or surgical curettage with chemical cautery. However, embolization alone or combined with other methods of treatment is valuable, particularly in non-resectable giant-cell tumours of the spine.

Child↗
PubMed1987

Condensing osteitis of the clavicle. A review of the literature and report of three cases.

Condensing osteitis of the clavicle is a rare and benign idiopathic entity that is probably degenerative or mechanical in etiology. It is usually seen in women of late child-bearing age as a variably painful and tender swelling over the medial end of the clavicle. Radiographs show sclerosis and slight expansion of the medial one-third of the clavicle. Although malignant tumor of bone must be considered in the differential diagnosis of a disease that has such radiographic findings, numerous and expensive screening tests for a presumed primary malignant lesion are not recommended for most patients. It is recommended, however, that an excisional or (preferably) incisional biopsy be performed in all patients unless pain is insignificant and the clinical presentation strongly supports the diagnosis of condensing osteitis. Many patients who have slight pain do not need treatment. Anti-inflammatory medications are variably effective. Patients in whom the lesion is refractory respond well to excision of the medial one-third of the clavicle.

Adult↗
PubMed1987

Osteoid osteoma of the distal femoral epiphysis. A case report.

The intraepiphyseal location of an osteoid osteoma in a skeletally immature individual is an extremely rare occurrence. Because of the joint-related symptoms and the wide range of possibilities in the differential diagnosis, en bloc excision is the treatment of choice. In the few cases that have been reported, the objectives have been to establish the diagnosis and simultaneously secure treatment. Image intensification accurately localizes the lesion and physeal plate in multiple planes, as well as aids in selecting a trephine diameter to accommodate tumor size. The objective is accurate excision with minimal involvement of the physeal plate or articular surfaces.

Adolescent↗
PubMed1986

Secondary malignant giant-cell tumor of bone. Clinicopathological assessment of nineteen patients.

Twenty-six patients who had a malignant giant-cell tumor of bone--a sarcoma either juxtaposed to a zone of typical benign giant-cell tumor or occurring at the site of a previously documented benign giant-cell tumor--have been seen at the Mayo Clinic. Of the twenty-six tumors, nineteen were secondary to a previous attempt at local control of a benign giant-cell tumor. All but one of these nineteen patients with a secondary tumor had received therapeutic irradiation four to thirty-nine years earlier. The nature and duration of the symptoms and the sites of predilection of the malignant giant-cell tumors were the same as for benign giant-cell tumor. Fibrosarcoma occurred three times as frequently as osteosarcoma. The best results of treatment of the secondary sarcoma were obtained with early ablation.

Adult↗