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Biomedical subjects

S W Wolfe

Publications and source records attributed to S W Wolfe.

At least 19 recordsLinked to original sources
PubMed1997

The effects of exercise on ligamentous stiffness in the wrist.

The purpose of this study was to determine if exercise alters wrist joint laxity, as measured by the mechanical behavior of the scaphoid bone. The load-displacement behavior of the scaphoid was studied in the palmar-dorsal direction in both wrists of 7 healthy volunteers (n = 14) before and after 2 exercise protocols (grip and push-up). When compared to the rested values, both exercise protocols significantly increased the displacement at 40 N by 47% (grip) and by 34% (push-up). Accordingly, the stiffness decreased significantly by 36% (grip) and by 32% (push-up). Partial recovery was documented after 1 hour of rest and there were no differences between any of the groups after 24 hours of rest. The increase in laxity documented during these exercise protocols reduces the ligament loads at comparable wrist positions and may thereby reduce the likelihood of traumatic ligamentous injury during participation in strenuous activity or sports.

Adult↗
PubMed1996

Detection of nerve rootlet avulsion on CT myelography in patients with birth palsy and brachial plexus injury after trauma.

OBJECTIVE: Recent advances in neurosurgical treatment of traumatic and birth-related brachial plexus injuries require differentiation of preganglionic nerve rootlet avulsion from postganglionic lesions. The purpose of this study was to evaluate the efficacy of thin-section high-resolution CT myelography for revealing cervicothoracic nerve rootlet avulsion in patients with brachial plexus injuries before surgery. MATERIALS AND METHODS: We evaluated eight patients with posttraumatic or birth-related brachial plexus injury on cervical plain film myelography and high-resolution CT myelography before surgical exploration and repair. CT myelograms were retrospectively evaluated for nerve rootlet avulsion, traumatic pseudomeningocele, and deformity of the subarachnoid space. Results were correlated with surgical exploration and intraoperative somatosensory evoked potentials. RESULTS: Seventy-two (95%) of 76 imaged cervicothoracic levels were adequately shown on CT myelography. Nerve rootlet avulsion, or preganglionic disruption, was shown at 21 levels. Associated pseudomeningocele, or deformity of the subarachnoid space, was seen at 12 (57%) of the 21 avulsion levels. Surgical exploration and intraoperative somatosensory evoked potentials showed complete preganglionic nerve rootlet avulsion at 22 levels. One of the complete avulsions revealed by surgery was not included on the patient's CT myelogram. Of the 21 imaged levels, 20 were correctly revealed on CT myelography (95% sensitivity, 98% specificity). At surgery, partial nerve rootlet avulsion was found at three other levels. None of the partial avulsions was correctly identified on the CT myelograms. CONCLUSIONS: High-resolution CT myelography with thin contiguous axial section is sensitive for revealing complete nerve rootlet avulsion in patients with brachial plexus birth palsies and brachial plexus injuries after trauma. Preoperative CT myelography in these patients allows a more complete injury evaluation for accurate prognosis and surgical planning.

Adolescent↗
PubMed1996

Radiographic progression to dorsal intercalated segment instability.

We present a case of an acute hyper-extension wrist injury that progressed from normal carpal alignment to dorsal intercalated segment instability over a short period of time. Disruption of the scapholunate interosseous and radioscapholunate ligaments was proven arthroscopically, while the intercapsular ligaments were demonstrated to be intact. We have shown that lunate malalignment can occur over time, as secondary lunate ligamentous supports attenuate under abnormal carpal kinetics.

Accidental Falls↗
PubMed1995

Two-dimensional rigid-body kinematics using image contour registration.

A method for calculating two-dimensional rigid-body kinematic parameters using shape features is presented. Proposed applications include the noninvasive quantification of planar joint motion in vivo. By using digitized images (computed tomographs, radiographs, etc.) of a bone contour at two positions, the contour curvatures can be 'best-fit' to obtain a one-to-one mapping or registration of the bone images. This produces a dense field of displacement vectors from which planar rigid-body kinematic parameters can be estimated. Accuracy was studied using radiographic images of cadaveric femoral bone. The two motions of pure rotation with a fixed center of rotation and of pure translation were simulated. For pure rotation, error in rotation was independent of the rotation magnitude, with an average (n = 10) error of 0.3 +/- 0.8 degrees. The translation error averaged 0.9 +/- 0.5 mm. For pure translation, the error in rotation was -0.01 +/- 0.69 degrees and the error in translation was -0.62 +/- 0.98 mm (n = 10). This novel method has broad applications in the field of planar kinematics, especially in cases for which marker fixation is neither possible nor practical.

Algorithms↗
PubMed1995

Arthroscopic-assisted reduction of distal radius fractures.

The outcomes of seven patients with severe comminuted intraarticular fractures of the distal radius treated by arthroscopic reduction and percutaneous external fixation (ARPEF) were retrospectively reviewed. All of the fractures were classified as C3 types using the AO classification scheme. Outcomes were evaluated using the Gartland and Werley functional criteria, an objective wrist examination, a radiographic analysis, and a self-assessment outcome form at an average follow-up of 27 months (range, 12 to 45 months). All patients were free of pain and had returned to their prior occupations. No patient had articular incongruency of greater than 1 mm, and there was no evidence of radiocarpal degenerative change. Active range of motion and maximal grip strength averaged 92% and 98%, respectively, of the uninjured wrist. The technique of arthroscope-assisted reduction and percutaneous external fixation yielded excellent results in a small group of patients, with minimal complications.

Adult↗
PubMed1995

Safety and efficacy of percutaneous trigger finger release.

Twenty-five A1 pulleys in 5 fresh cadaveric hands and 13 trigger fingers in 11 patients were released percutaneously with a 19 gauge needle, as described by Eastwood et al., to determine the efficacy and safety of the technique. Over 90% of the length of each individual finger and thumb A1 pulley were successfully released in the cadaveric digits with no injuries to the A2 pulley, nerves, or vessels. Superficial abrasions were noted in four superficialis tendons. In our surgical series, complete clinical release (eradication of triggering) was achieved in each digit. In 8 of 13 digits, the A1 pulley was found to be completely divided on open exploration. In five digits, while triggering was eliminated, some of the A1 pulley remained intact. There were no complications. Because of the proximity of digital nerves, we do not perform percutaneous release in the index finger or thumb.

Adult↗
PubMed1995

Intra-articular impaction fractures of the phalanges.

Six patients with acute impacted fractures of the base of the proximal or middle phalanges were treated with open reduction and internal fixation. Two of three patients who presented with chronic injuries also underwent surgical reconstruction. Contiguous 1.5-mm sagittal computed tomographic imaging was performed on each proximal interphalangeal joint fracture; the imaging documented an average impaction of 30% of the articular surface area. Metaphyseal bone grafting was necessary to support the articular surface in three acute and both late patients. Rigid internal fixation, most frequently employing a composite wire tension band technique, allowed immediate postoperative range of motion exercises. At an average follow-up period of 21 months, all six acute patients had restoration of an excellent painless range of motion. There was no loss of articular congruency on final x-ray films. Late or conservative treatment of these injuries was uniformly less successful.

Accidental Falls↗
PubMed1994

Optimal marker placement for calculating the instantaneous center of rotation.

A computer simulation with error propagation was performed to determine the optimal placement of marker points for calculating the instantaneous center of rotation (CRi). The authors assume that planar rigid body motion occurs between two positions, each defined by marker points. Noisy marker points were generated by perturbing their coordinates with random values from a normal population of errors. The effects of these errors on the range of errors in calculating CRi location were investigated. Parametric analysis determined that marker point placement had important effects on CRi error. Marker placement was optimal when the estimated CRi was located at the midpoint between the marker points. While increasing the distance between marker points increased accuracy, there is a critical distance above which no additional increase in accuracy was noted when using this placement. The farther the marker midpoint was from the CRi, the greater was the error. At these placements, increasing the distance between the marker points continually decreased CRi error. The methodologies presented here help to improve the accuracy with which the location of the CRi can be calculated. However, it is emphasized that the CRi remains sensitive to noise and investigations should apply this kinematic parameter knowingly.

Biomechanical Phenomena↗
PubMed1994

Mechanical evaluation of the scaphoid shift test.

Manipulative examination of the carpal bones is an important facet of the examination of the wrist. Abnormal translation of portions of the carpus in response to applied force is a commonly used clinical indicator of ligament injury. Unilateral scaphoid hypermobility during the so-called scaphoid shift test is felt to represent traumatic instability, especially in the context of wrist injury. The test, however, is subjective, and requires considerable experience to correlate the degree of scaphoid mobility with pathologic significance. We used an instrument that quantifies the load-displacement behavior of the scaphoid and its supporting ligaments during application of a dorsally directed load at the scaphoid tubercle. We evaluated 18 uninjured (normal) wrists with clinical ligament examination and with mechanical testing. Subjects who exhibited a positive scaphoid shift had significantly increased displacement and significantly decreased stiffness when compared with subjects who did not have a shift.

Adult↗
PubMed1994

Scaphoid shift in the uninjured wrist.

To determine the prevalence of a positive scaphoid shift in an uninjured population, 100 patients presenting with symptoms unrelated to trauma or wrist instability underwent physical and radiographic evaluation. On physical examination, the scaphoid shift maneuver was performed bilaterally, and generalized ligamentous laxity was assessed using standard criteria. Standard x-ray films were inspected for carpal abnormalities, and the radiolunate and scapholunate angles were measured. The prevalence of a positive scaphoid shift was 32%; the shift was painless in all patients. Fourteen patients had a unilateral scaphoid shift. Patients with a positive scaphoid shift had increased generalized ligamentous laxity manifested by a decreased average thumb-to-forearm distance and an increased mean flexion-extension arc. A positive shift was not correlated with radiographic carpal malalignment.

Carpal Bones↗
PubMed1994

Infection following total elbow arthroplasty.

Total elbow arthroplasty can be a safe, effective means of relieving the pain and loss of motion owing to arthritis of the elbow; however, infection is a frequent and devastating complication that occurs in 1 of every 20 total elbows. Through careful patient selection, meticulous operative technique, and vigilant postoperative care, this risk can be decreased. If infection does develop, early, aggressive operative management provides the best hope for salvage of the joint.

Elbow Joint↗
PubMed1994

Primary semiconstrained total elbow arthroplasty. Survival analysis of 113 consecutive cases.

We used survival analysis to evaluate 113 consecutive semiconstrained total elbow arthroplasties (TEAs) in 95 patients at a maximum follow-up of 99 months. Our criteria for failure were mechanical malfunction, revision for any reason, and deep infection. The primary diagnosis was inflammatory arthritis in 86 elbows, post-traumatic arthritis in 6, supracondylar nonunion or fracture in 12, osteoarthritis in 2 and other causes in 3. Seven failures were due to deep infection, and five of these had a primary diagnosis of inflammatory arthritis. Eight failures were revised or had revision recommended for aseptic loosening, and six of these were in patients with post-traumatic arthritis or supracondylar nonunion. The cumulative survival for TEAs performed for post-traumatic arthritis, fractures or supracondylar nonunion was 73% at three years and 53% at five years, significantly worse than the cumulative three- and five-year survivals of 92% and 90%, respectively, for patients with inflammatory arthritis. TEA with a semiconstrained prosthesis appears to have a satisfactory survival in selected patients with arthritic disorders. The incidence of deep infection was reduced by improvements in surgical technique and postoperative management, and the routine use of antibiotic-impregnated cement. The incidence of aseptic loosening was low, except in patients with supracondylar nonunion or post-traumatic arthritis.

Adult↗
PubMed1992

Compressive forces.

Explore the source record for details and available documents.

Biomechanical Phenomena↗
PubMed1992

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↗
PubMed1991

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↗
PubMed1991

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↗
PubMed1990

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↗