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Biomedical subjects

M F Schafer

Publications and source records attributed to M F Schafer.

25 records · Page 2Linked to original sources

Mechanical evaluation of the Dwyer screw-cable attachment.

A critical portion of the Dwyer technique is the crimping of the screw head to prevent the cable from slipping. Initally, Dwyer designed a hydraulic mechanism to crimp the screw head. However, this instrument was cumbersome to use and presented potential sterility problems. Today the Simmons crimper is used by the majority of orthopaedic surgeons. It is the purpose of this paper to report the studies conducted on 1) different materials used for the fabrication of the screws, and 2) the significance of the variations in the jaw opening using the Simmons mechanical crimper.

Evaluation Studies as Topic↗

Arterial abnormalities of the shoulder in athletes.

Vascular lesions of the shoulder may be misinterpreted as one of the more familiar shoulder abnormalities by a treating physician. We are reporting on 13 athletes who were found to have symptoms related to compression of the subclavian or axillary artery or their tributaries. Nine were amateur or professional baseball pitchers. Severe arm fatigue or finger ischemia, secondary to embolization, were presenting symptoms. Arm fatigue was noted in all pitchers. After complete history and physical examination, including auscultation for bruits in functional positions, all athletes were evaluated by noninvasive tests (Doppler and Duplex scanning). Arteriography was performed with positional testing, recreating overhead activity, and complete radiographic visualization of the dye to the digital arteries. Two patients were found to have subclavian artery aneurysm. The remaining athletes were found to have compression of the subclavian artery beneath the anterior scalene muscle (five patients), the axillary artery beneath the pectoralis minor (two patients), both arterial segments (two patients), and one was found to have arterial compromise at the level of the humeral head. Branch artery compression was also noted. One pitcher occluded the posterior circumflex humeral artery with embolization to the digit. The two patients with subclavian aneurysms underwent saphenous vein bypass with cervical rib resection. All of the other athletes except one underwent resection of a 2 to 3 cm segment of the anterior scalene muscle or pectoralis minor muscles. All returned to their previous level of activity except one patient who developed impingement type symptoms and required acromioplasty. He is currently undergoing rehabilitation. Proper recognition of vascular compromise in the upper extremity of athletes is essential to avoid the catastropic complications of arterial thrombosis.

Athletic Injuries↗

Arterial abnormalities of the hand in athletes.

Vascular lesions of the hand may be seen in athletes exposed to repetitive blunt trauma. Thirteen athletes seen from 1983 to 1988 experienced symptoms related to hand ischemia. Nine were professional baseball catchers. The majority of patients complained of chronic symptoms, including cold hypersensitivity (four patients), finger numbness (one), finger coolness (three), and finger blanching (three). Two patients had acute symptoms with sudden posttraumatic hand ischemia with finger and palmar pain. Diagnosis was established by history and physical examination and confirmed by noninvasive testing. Testing included use of Doppler examination and cold tolerance examination with thermistors. Two athletes required angiographic evaluation because of severe ischemia and continuous pain. All patients in this group were managed nonoperatively. Those with chronic complaints were counseled regarding cold avoidance and instructed to increase their glove padding. The two patients with acute symptoms required vasodilator (papaverine chloride) infusion, followed by intravenous heparin and dextran. All baseball catchers returned to their sport with dissipation of symptoms.

Arteries↗

Quantitative assessment with SPECT imaging of stress injuries of the pars interarticularis and response to bracing.

The evaluation and management of acute spondylolysis remains unclear in part because of outcome data that are primarily subjective. The aim of this study was to evaluate and monitor these patients objectively using quantitative single-photon emission computed tomography (SPECT). Thirty-four patients were so observed clinically between 1987 and 1996 and were studied with an initial and at least one follow-up SPECT scintigram. Initial radiographs and planar bone scans failed to demonstrate the pars lesion in 53 and 19% of the patients, respectively. The average SPECT ratio before brace treatment was 1.45. After treatment, this ratio significantly decreased to 1.27 (p = 0.03). A subset of patients remained symptomatic at follow-up. Their reduction in SPECT ratio averaged only 2.8% as compared with 13% for the remainder of the patients (p = 0.01). Patients diagnosed and braced in the early, more active stage of the condition (with greater intensity on SPECT) had more predictable symptom relief. An initial SPECT ratio of >1.5 was associated with complete symptom resolution after brace treatment. Patients treated with activity restriction only (>3 months) before bracing were more likely to have persistent symptoms and more modest improvement on SPECT (p = 0.01). These data, which use SPECT scintigraphy, support prompt treatment with brace immobilization for acute spondylolysis in children and adolescents.

Adolescent↗

Standards in anterior spine surgery in pediatric patients with neuromuscular scoliosis.

The authors reviewed 111 patients with neuromuscular disease who underwent anterior spine surgery for correction of scoliosis. An overall complication rate of 44.1% was found, 21.6% major and 22.5% minor. Pulmonary complications were the most common major complications, urinary tract infections the most common minor complications. The rate of complications was greater in patients with cerebral palsy, thoracoabdominal and transthoracic approaches, staged procedures, operative blood loss >1,000 mL, or previous spine surgery. In addition, statistical analysis confirmed that curve magnitude >100 degrees degrees was a risk factor for complications.

Adolescent↗

Onlay fibular bone grafting in treatment of tibial fracture non-union.

Twenty-nine patients with tibial non-union or delayed union were treated by onlay grafting, using long struts from the ipsilateral fibula and without disturbing the non-union site. Internal fixation and excessive dissection can be avoided. Follow-up in 28 patients showed solid healing in all; 20/28 patients united the fracture within 7 months. Removal of the fibula as a distracting force, combined with the principles of onlay grafting advocated by Phemister, is effective surgical treatment.

Adolescent↗