Biomedical subjects

Robert A Kaufmann

Publications and source records attributed to Robert A Kaufmann.

8 recordsLinked to original sources

PubMed2006

Lower median nerve block impairs precision grip.

The purpose of this study was to investigate precision grip impairment caused by a lower median nerve block at the wrist. The median nerve block was achieved by injecting bupivacaine hydrochloride into the carpal tunnel, which acutely simulated a median neuropathy. Seven healthy male subjects were instructed to grip, lift, and hold an instrumented handle within 60s using precision grip. The same tasks were performed before and after the nerve block. Force and torque data were recorded using two miniature 6-component force/torque transducers. The precision grip was quantified by the safety margin (i.e. the difference between the actual grip force and the minimal grip force to keep the object from dropping), the variation of grip force, and the migration area of center of pressure (i.e. the area defined by the center of pressure at a digit-transducer surface while holding the handle). Two subjects were unable to complete the precision grip tasks after the nerve block, and their data were excluded from the analyses. The median nerve block caused significant increases (P<0.05) in the safety margin of the grip force (>50%), the grip force variation (>80%), and the area of center of pressure migration (>250%). Median nerve block at the wrist impairs the fine motor control during precision grip. Our results corroborate the important role played by sensory function in hand fine motor control. Clinically, the measures related to precision grip have the potential to quantify impairment of hand function caused by neuromuscular disorders, to monitor the progress of a hand disorder, and to evaluate the efficacy of a treatment or rehabilitation procedure.

Adult↗

PubMed2006

Arthroscopic debridement and closed pinning for chronic dynamic scapholunate instability.

PURPOSE: For chronic dynamic scapholunate (SL) instability (>3 months after injury) open procedures (capsulodesis, limited intercarpal fusions, tenodesis, SL ligament reconstruction) have become popular in recent years but their long-term results have been suboptimal. We evaluated retrospectively the results of aggressive arthroscopic debridement of the SL ligament to bleeding bone in an effort to induce scar formation and closed pinning of the SL joint in patients unwilling to have an open procedure. METHODS: Eleven patients (mean age, 37 y) presenting with persistent posttraumatic pain and weakness to the wrist were diagnosed with dynamic SL instability (positive Watson scaphoid shift test result, SL gapping on grip-view radiographs, arthroscopic findings of a Geissler grade III or IV SL tear) and treated. Range of motion, grip strength, radiographic measurements, and the Mayo wrist score were used to evaluate the results. RESULTS: The mean follow-up period was 33 months (range, 12-76 mo). Three patients had subsequent surgery 9 to 11 months after the procedure. Subsequent surgeries included a dorsal capsulodesis, a four-corner fusion, and a wrist arthrodesis. Of the 8 remaining patients there were 2 excellent, 4 good, 1 fair, and 1 poor result based on the Mayo wrist score. In these patients the mean range of motion was 65 degrees of extension to 59 degrees of flexion and the mean grip strength was 82% of the uninjured contralateral extremity. Although persistent radiographic SL gapping in grip views was noted in all 8 patients none progressed to static instability or dorsal intercalated segment instability. CONCLUSIONS: The results of this technique are suboptimal; however, it may be an option for patients unwilling to have more than an arthroscopic procedure or those requiring maintenance of wrist motion, provided they understand the risks and benefits of this approach. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic, Level IV.

Adult↗

PubMed2006

Kinematics of the midcarpal and radiocarpal joint in flexion and extension: an in vitro study.

PURPOSE: To apply carpal kinematic analysis using noninvasive medical imaging to investigate the midcarpal and radiocarpal contributions to wrist flexion and extension in a quasidynamic in vitro model. METHODS: Eight fresh-frozen cadaver wrists were scanned with computed tomography in neutral, full flexion, and full extension. Body-mass-based local coordinate systems were used to track motion of the capitate, lunate, and scaphoid with the radius as a fixed reference. Helical axis motion parameters and Euler angles were calculated for flexion and extension. RESULTS: Minimal out-of-plane carpal motion was noted with the exception of small amounts of ulnar deviation and supination in flexion. Overall wrist flexion was 68 degrees +/- 12 degrees and extension was 50 degrees +/- 12 degrees. In flexion, 75% of wrist motion occurred at the radioscaphoid joint, and 50% occurred at the radiolunate joint. In extension, 92% of wrist motion occurred at the radioscaphoid joint, and 52% occurred at the radiolunate joint. Midcarpal flexion/extension between the capitate and scaphoid was 0 degrees +/- 5 degrees in extension and 10 degrees +/- 13 degrees in flexion. Midcarpal flexion/extension between the capitate and lunate was larger, with 15 degrees +/- 11 degrees in extension and 22 degrees +/- 19 degrees in flexion. CONCLUSIONS: The capitate and scaphoid tend to move together. This results in greater flexion/extension for the scaphoid than the lunate at the radiocarpal joint. The lunate has greater midcarpal motion between it and the capitate than the scaphoid does with the capitate. The engagement between the scaphoid and capitate is particularly evident during wrist extension. Out-of-plane motion was primarily ulnar deviation at the radiocarpal joint during flexion. These results are clinically useful in understanding the consequences of isolated fusions in the treatment of wrist instability.

Adolescent↗

PubMed2005

Scapulothoracic dissociation: evaluation and management.

Scapulothoracic dissociation is an infrequent injury with potentially devastating outcomes. Knowledge of this injury is based on small patient series and case reports. The aim of this article is to review the evaluation, management and functional outcomes following scapulothoracic dissociation. Often caused by high traction forces applied to the shoulder girdle, there is a complete loss of the scapulothoracic articulation with lateral scapular displacement and intact skin. This is frequently associated with muscular, ligamentous and osseous injuries to the shoulder girdle, vascular injuries to the subclavian, or axillary, vessels and brachial plexus lesions. In the acute setting, the timely diagnosis of the associated neurovascular injuries is crucial. Severe neurovascular and soft tissue compromise often requires an early above-elbow amputation. Further, complete brachial plexus avulsions are associated with a limited potential for functional recovery.

Acromioclavicular Joint↗

PubMed2005

Quantifying the effect of the distal intrinsic release procedure on proximal interphalangeal joint flexion: a cadaveric study.

PURPOSE: The distal intrinsic release procedure is a popular treatment for intrinsic hand tightness. The literature remains ambiguous regarding the optimal amount of extensor hood to excise. Our goals were to quantify the mathematic relationship between the amount of extensor hood excised and proximal interphalangeal (PIP) joint flexion and to determine the minimum amount of extensor hood excision required to significantly change PIP joint flexion capability (the ability to achieve a change from the initial PIP joint angle). METHODS: We simulated the distal intrinsic release procedure by sequentially excising 5-mm strips (perpendicular to the long axis of the finger) of the extensor hood of cadaveric fingers beginning 5 mm proximal to the PIP joint center. We tensioned the intrinsic muscles to each digit to produce an intrinsically tight state and tensioned the flexor digitorum superficialis to produce an antagonist force and simulate the intrinsic tightness test. We measured PIP joint angle (the angle of the long axis of the middle phalanx relative to the proximal phalanx) in response to greater portions of excised extensor hood to quantify its contribution to intrinsic tightness. RESULTS: The relationship between the amount of extensor hood excised and the PIP joint flexion capability appeared quadratic, not linear. For the index, ring, and small fingers significant changes in PIP joint flexion were detected after resection of 59%, 26%, and 33%, respectively, of the extensor hood length. Although our results did not show statistical significance for the middle finger we project the critical amount to be at least 65%. CONCLUSIONS: We show PIP joint flexion changes after the distal intrinsic release procedure. We recommend excising a finger-dependent minimum amount of tissue before expecting a significant increase in PIP joint flexion capability.

Cadaver↗

PubMed2002

Changes in strain distribution along the radius and ulna with loading and interosseous membrane section.

The changes in strain distribution along the radius and ulna with loading and interosseous membrane (IOM) section were analyzed in this biomechanical study. Four cadaveric upper extremities were dissected and strain gauges applied. The forearm was loaded at the distal radius with a carpal implant after being positioned upright in neutral forearm rotation. Strain measurements were recorded before and after transection of the IOM. Before IOM transection, increased compressive strain was measured on the ulnar border of the ulna, while increased tensile strain was recorded on the dorsal aspect of the ulna, the dorsal aspect of the radius, and the lateral border of the radius when compared with the unloaded forearm. This suggests bowing of the radius and ulna with the convex side dorsally and bowing of the radius with the convex side radially. After IOM transection, increased tensile strain on the lateral border of the radius and the ulnar border of the ulna was measured when compared with the loaded forearm with an intact IOM. No change in strain patterns was measured by the strain gauges located on the dorsal aspect of the radius or ulna after IOM transection. The increased tensile strain during constant load application suggests increased bending moments acting on the radius and ulna after IOM transection.

Compressive Strength↗

PubMed2002

Bilateral congenital subtalar dislocation: a case report.

Fixed bilateral congenital subtalar dislocations were identified in a 2.5-year-old boy. The patient had been treated previously with a short-leg cast on each foot for 2 months. On presentation the patient ambulated on the medial malleoli and medial aspects of his feet. The patient's activity was limited by pain. At 2.5 years of age, open reduction and pinning of bilateral subtalar joints with soft tissue release and lengthening of the achilles, peroneal, and extensor tendons was done. A thick fibrous band connected the talus and calcaneus laterally. Postoperative treatment included casting for 12 weeks and wearing rigid ankle-foot orthoses which he used for 8 years. There was no recurrence at 10-year followup. The patient has been brace-free for 2 years and is able to ambulate and play school sports without pain. The patient's subtalar range of motion is normal. Radiographic alignment is near normal without degenerative changes. To the authors' knowledge, there has been no previous report of this condition in the literature.

Child, Preschool↗

PubMedDate not supplied

Development and use of a wrist fusion plate for children and adolescents.

Arthrodesis is a widely accepted treatment for several destructive disorders of the wrist joint. Previous literature has shown that compression plating is a reliable technique for achieving rigid fixation and fusion in adults. The goal of this study was to apply similar principles of adult wrist fusion to children, using a custom-designed fusion plate sized for children. Five children underwent wrist fusion using rigid fixation and dorsal plate application. Mean age at time of surgery was 16.4 years. The indication for surgery was paralysis (spinal cord injury) in three and spasticity (cerebral palsy and traumatic brain injury) in two. Surgery was performed through a dorsal approach and combined with carpectomy in the two patients with spasticity. Follow-up averaged 2.2 years and radiographs showed solid fusion and proper alignment of plate and screws. Improved stability and limb function were noted by patients and family. There were no instances of hardware failure, and plate removal has not been required.

Adolescent↗