Compressive forces.
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Biomechanical Phenomena↗
Biomedical subjects
S W Wolfe
Publications and source records attributed to S W Wolfe.
Unilateral blindness as a complication of patient positioning for spinal surgery. A case report.
Extreme care must be used in positioning patients for surgery in a prone position. A padded Mayfield headrest may not be appropriate for all patients undergoing spinal surgery, as exophthalmus or a flattened nasal bridge may allow transmission of pressure to the globe. Our current approach is to use supplementary foam rubber support, with repeated, meticulous attention to keeping the eyes free from all pressure. Finally, unexplained intraoperative occurrence of a bradyarrhythmia or conduction disturbance may signal increased intraorbital pressure during general anesthesia.
Adult↗
Articular fractures of the hand. Part I: Guidelines for assessment.
Articular fractures of the hand represent a particularly challenging group of injuries owing to the frequent comminution of the fractured bone, disruption of a finely balanced soft-tissue sleeve, and a propensity for scarring and contractures. Assessment of these fractures must include accurate delineation of the injury, using roentgenographic and computed tomographic imaging to define articular congruency, and a precise examination to determine stability.
Finger Injuries↗
Articular fractures of the hand. Part II: Guidelines for management.
Articular fractures of the hand represent a particularly challenging group of injuries owing to the frequent comminution of the fractured bone, disruption of a finely balanced soft-tissue sleeve, and a propensity for scarring and contractures. Treatment must restore anatomic joint alignment and stability and should incorporate a carefully guided early rehabilitation program. Part I of this article, which appeared in the January issue, covered techniques for the evaluation of these complex injuries.
Finger Injuries↗
Management of infection about total elbow prostheses.
Deep infection was a complication after twelve (7.3 per cent) of 164 primary total elbow replacements. Two additional patients who had an infection about an elbow prosthesis were referred for treatment after total elbow replacement elsewhere. A statistical analysis of all of these primary total elbow arthroplasties, including the two in patients who were referred from outside institutions, identified preoperative factors that placed a patient at significant risk for subsequent infection. The risk factors included a previous operation on the elbow, a previous infection in the region of the elbow, psychiatric illness, class-IV rheumatoid arthritis, drainage from the wound after operation, spontaneous drainage after ten days, and reoperation for any reason. Three modes of treatment were used for patients who had an established infection: débridement and salvage of the implant, resection arthroplasty, and arthrodesis. After early operative débridement and suppression of the infection with long-term antibiotic therapy, three patients were able to retain the prosthesis, with restoration of range of motion and function of the upper extremity. One prosthesis was reimplanted after a six-week course of intravenous administration of antibiotics.
Adolescent↗
Results of reconstruction for failed total elbow arthroplasty.
Failure of total elbow arthroplasty leads to difficult and complicated surgical reconstruction. This study evaluates the results of reconstruction after implant removal with respect to pain, motion, and functional ability. Between 1978 and 1985, 11 patients required implant removal. Indications for removal were infection for seven, implant fracture for three, and recurrent dislocation for one. The original diagnosis was rheumatoid arthritis in six elbows and traumatic arthritis in five. The average length of the follow-up period was 5.5 years after implant removal (minimum, two years). Treatment consisted of implant removal and soft-tissue arthroplasty combined with external fixation in ten patients, and attempted arthrodesis with external fixation in one. There were four good, one fair, two poor, and four failed results. Satisfactory results were obtained in seven of the eight elbows in which an anatomic arthroplasty was achieved. This consisted of containment of the ulna by the humeral epicondylar remnants. All eight elbows were pain-free with an average arc of motion of 85 degrees (range, 55 degrees to 120 degrees). They had excellent elbow flexion power; however, triceps strength was often compromised. In the three elbows in which anatomic arthroplasty could not be achieved, one was flail, one was later converted to an arthrodesis with a customized plate, and the third required an immediate arthrodesis. All three were rated as failures. Fractures occurred in five of the 11 elbows. One occurred preoperatively, three occurred intraoperatively, and one occurred postoperatively. All healed satisfactorily during the course of immobilization. The importance of an anatomic arthroplasty when removing a total arthroplasty cannot be overemphasized. Retaining the epicondylar segments is important because satisfactory results were obtained in patients in whom entrapment of the olecranon within the epicondylar ridges was obtained. Such patients can achieve a satisfactory soft-tissue arthroplasty without the use of an interpositional material. When the epicondylar ridges were not retained and there was marked instability, the patients did not achieve satisfactory results.
Adult↗
The osteo-anconeus flap. An approach for total elbow arthroplasty.
Twenty-seven consecutive primary total elbow arthroplasties were done with a technique that preserved the continuity of the attachment of the triceps brachii muscle with a wafer of bone from the reflected extra-articular portion of the olecranon and with the lateral fascia of muscles of the forearm. During closure, the wafer was reattached to the broad cancellous surface of the olecranon with sutures through the bone. The elbows were immobilized for an average of sixteen days postoperatively. The patients who were available for follow-up were re-examined at an average of 3.9 years, and the strength of the triceps muscle was checked. No extensor lag or avulsion of the triceps occurred, and mild extensor weakness was seen in only two elbows. No patient had early or late drainage of the wound or infection. The average range of motion compared favorably with that in other reported series. This osteo-anconeus posterior approach is advocated for total elbow arthroplasty because it provides rapid and wide exposure, it is associated with a low rate of complications related to the wound, and it preserves the strength of the triceps.
Elbow Joint↗
Computed tomographic evaluation of fatty neoplasms of the extremities. A clinical, radiographic, and histologic review of cases.
Eleven lipomatous tumors of the extremities (7 liposarcomas, 4 lipomas) were evaluated radiographically by several modalities, including computed tomography (CT) in all lesions. Lipomas were seen on CT scan as well delineated, homogeneous masses with negative attenuation coefficients ranging from -95 to -160. Liposarcomas were inhomogeneous, multilobulated, poorly delineated lesions located exclusively in the subfascial or intramuscular planes, with an intermediate range of attenuation coefficients between those of fat and those of muscle. In six of seven liposarcomas, definite low density areas were identified by attenuation coefficient as fatty tissue. Magnetic resonance imaging (MRI) was obtained in two patients and was helpful in defining the extent of the tumors and their relationship to vital structures, but MRI could not differentiate benign from malignant tissue. Computed tomography is recommended as the cornerstone in the initial radiographic evaluation of growing or painful lipomatous soft tissue masses of the extremities.
Adult↗
Ruptures of the pectoralis major muscle. An anatomic and clinical analysis.
We evaluated 12 patients with 14 ruptures of the pectoralis major muscle to compare surgical and conservative management of this injury. Because 9 of the injuries occurred while weight lifting, we performed an anatomic study on human hemithorax specimens during a simulated bench press to determine the mechanism of this rare occurrence. Excursion of individual pectoralis muscle fibers was measured at seven points along the broad muscle origin by the use of fine wires connected to the humeral insertion and to dial gauges on the study apparatus. Excursions in the concentric and eccentric phases of the lift were expressed as a percentage of resting fiber length. The short, inferior fibers of the muscle lengthened disproportionately during the final 30 degrees of humeral extension. We concluded that the inferior fibers have a mechanical disadvantage in the final portion of the eccentric phase of the lift, and application of high loads to these maximally stretched fibers produces rupture. We repaired five acute and two chronic ruptures, and measured peak torque and work production against the contralateral side using Cybex isokinetic testing. Surgically treated patients showed comparable torque and work measurements, while conservatively treated individuals demonstrated and marked deficit in both peak torque and work/repetition. We recommend repair of complete pectoralis muscle ruptures in active patients who require maximum strength in vocational or avocational activities.
Adolescent↗