Scott W. Wolfe

Perinatal brachial plexus palsy.

Perinatal brachial plexus palsy (PBPP) has been traditionally classified into three types: upper plexus palsy (Erbs) affecting the C5, C6, and +/- C7 nerve roots, lower plexus palsy (Klumpkes) affecting the C8 and T1 nerve roots, and total plexus palsy. Although most cases will resolve spontaneously, the natural history of the remaining cases is influenced by contractures of uninvolved muscle groups and subluxation or dislocation of the shoulder and elbow. Microsurgical nerve repair has demonstrated to provide improved outcomes compared to conservative treatment, while advancements in secondary reconstruction have offered significant improvements in the performance of activities of daily living for older children with unresolved plexus palsy.

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.

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.

A non-invasive method for studying in vivo carpal kinematics.

Seven uninjured and three injured patients were studied using midsagittal computed tomographic (CT) images at 10° increments from full extension to full flexion. Each injured patient had a confirmed scapholunate ligament tear and normal radiographs. CT bony contours were digitized, and incremental motion determined using a specifically designed automated contour-matching algorithm. We expressed wrist motion as a ratio of lunocapitate (midcarpal) motion, and radiolunate (radiocarpal) motion. In normal wrists, motion occurred equally at the midcarpal and radiocarpal joints. In wrists with scapholunate ligament disruption, lunocapitate motion increased significantly throughout the arc of motion.

MRI of multiple glomus tumors of the finger

Abstractu2002A case of multiple glomus tumors of the finger is presented, in which MRI was valuable in the diagnosis and preoperative tumor localization.

Segmentation of Carpal Bones from 3d CT Images Using Skeletally Coupled Deformable Models

The in vivo investigation of joint kinematics in normal and injured wrist requires the segmentation of carpal bones from 3D (CT) images and their registration over time. The non-uniformity of bone tissue, ranging from dense cortical bone to textured spongy bone, the irregular, small shape of closely packed carpal bones which move with respect to one another, and with respect to CT resolution, augmented with the presence of blood vessels, and the inherent blurring of CT imaging renders the segmentation of carpal bones a challenging task. Specifically, four characteristic difficulties are prominent: (i) gaps or weak edges in the carpal bone surfaces, (ii) diffused edges, (iii) textured regions, and, (iv) extremely narrow inter-bone regions. We review the performance of statistical classification, deformable models, region growing, and morphological operations for this application. We then propose a model which combines several of these approaches in a single framework. Specifically, initialized seeds grow in a curve evolution implementation of active contours, but where growth is modulated by a skeletally-mediated competition between neighboring regions, thus combining the advantages of local and global region growing methods, region competition and active contours. This approach effectively deals with many of the difficulties presented above as illustrated by numerous examples.

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.

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.

Wrist kinematic coupling and performance during functional tasks: effects of constrained motion.

PURPOSEnTo quantify the coupled motion of the wrist during selected functional tasks and to determine the effects of constraining this coupled motion using a radial-ulnar deviation blocking splint on performance of these tasks.nnnMETHODSnTen healthy, right-handed men performed 15 trials during selected functional tasks with and without a splint, blocking radial and ulnar deviation. The following tasks were performed: dart throwing, hammering, basketball free-throw, overhand baseball and football throwing, clubbing, and pouring. Kinematic coupling parameters (coupling, kinematic path length, flexion-extension range of motion, radial-ulnar deviation range of motion, flexion-extension offset, and radial-ulnar deviation offset) and performance were determined for each functional task. A generalized estimation equation model was used to determine whether each kinematic coupling parameter was significantly different across tasks. A repeated-measures generalized estimation equation model was used to test for differences in performance and kinematic coupling parameters between the free and splinted conditions.nnnRESULTSnWrist motion exhibited linear coupling between flexion-extension and radial-ulnar deviation, demonstrated by R(2) values from 0.70 to 0.99. Average wrist coupling and kinematic path lengths were significantly different among tasks. Coupling means and kinematic path lengths were different between free and splinted conditions across all tasks other than pouring. Performance was different between wrist conditions for dart throwing, hammering, basketball shooting, and pouring.nnnCONCLUSIONSnWrist kinematic coupling parameters are task specific in healthy individuals. Functional performance is decreased when wrist coupling is constrained by an external splint.nnnCLINICAL RELEVANCEnSurgical procedures that restrict wrist coupling may have a detrimental effect on functional performance as defined in the study. Patients may benefit from surgical reconstructive procedures and wrist rehabilitation protocols designed to restore kinematic coupling.

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.