Ulnar nerve excursion and strain at the elbow and wrist associated with upper extremity motion.

Significant excursion of the ulnar nerve is required for unimpeded upper extremity motion. This study evaluated the excursion necessary to accommodate common motions of daily living and associated strain on the ulnar nerve. The 2 most common sites of nerve entrapment, the cubital tunnel and the entrance of Guyon's canal, were studied. Five fresh-frozen, thawed transthoracic cadaver specimens (10 arms) were dissected and the nerve was exposed at the elbow and wrist only enough to be marked with a microsuture. Excursion was measured with a laser mounted on a Vernier caliper fixed to the bone and aligned in the direction of nerve motion. A Microstrain (Burlington, VT) DVRT strain device was applied to the nerve at both the elbow and wrist. Nerve excursion associated with motion of the shoulder, elbow, wrist, and fingers (measured by goniometer) was measured at the wrist and elbow. An average of 4.9 mm ulnar nerve excursion was required at the elbow to accommodate shoulder motion from 30 degrees to 110 degrees of abduction, and 5.1 mm was needed for elbow motion from 10 degrees to 90 degrees. When the wrist was moved from 60 degrees of extension to 65 degrees of flexion, 13.6 mm excursion of the ulnar nerve was required at the wrist. When all the motions of the wrist, fingers, elbow, and shoulder were combined, 21.9 mm of ulnar nerve excursion was required at the elbow and 23.2 mm at the wrist. Ulnar nerve strain of 15% or greater was experienced at the elbow with elbow flexion and at the wrist with wrist extension and radial deviation. Any factor that limits excursion at these sites could result in repetitive traction of the nerve and possibly play a role in the pathophysiology of cubital tunnel syndrome or ulnar neuropathy at Guyon's canal.

Long-term complications of snake bites to the upper extremity.

The purpose of this study was to determine long-term complications of upper-extremity snake envenomations. The records of 73 patients, who were seen for snake bites were obtained; 46 of these patients had bites to the upper extremity, and 27 had bites to the lower extremity. These patients were graded according to the severity of the bite. The snakes involved were eastern diamondback rattlesnake, coral snake, pigmy rattlesnake, water moccasin, and unknown. Fourteen of the 46 patients receiving upper extremity bites were examined by a hand surgeon and an occupational hand therapist 1 to 3.2 years after their bite. Subjective pain data, range-of-motion, intrinsic, extrinsic, finger-flexion tightness, grip strength, pinch strength and objective sensory data were collected. Four patients had continued pain and tissue atrophy at the bite site. There were no long-term sequelae from a missed compartment syndrome.

Excursion and strain of the median nerve.

Five fresh-frozen transthoracic cadaver specimens (ten upper extremities) were dissected in order to measure excursion and strain of the median nerve at the wrist and the elbow in association with different positions of the shoulder, elbow, wrist, and fingers. The relationships between motions of the joints and excursion and strain at the wrist and the elbow as well as between excursion and strain were also determined. When the wrist was moved from 60 degrees of extension to 65 degrees of flexion, the median nerve at the wrist underwent a mean total excursion of 19.6 millimeters (9.2 +/- 1.38 millimeters [mean and standard deviation] in extension and 10.4 +/- 1.50 millimeters in flexion). The change in strain was not measurable secondary to nerve-wrinkling. Motion of the fingers from hyperextension to full flexion caused a mean total excursion of 9.7 millimeters (6.3 +/- 1.31 millimeters in hyperextension and 3.4 +/- 1.04 millimeters in flexion) and a change in strain of 19.0 per cent. This change in strain became more pronounced when the wrist and the fingers moved in synergy. Such strain, if constant, has been shown to decrease microvascular perfusion and nerve conduction in rabbits. With motion of the shoulder, the mean total excursion of the median nerve at the elbow was 9.1 millimeters (4.4 +/- 1.64 millimeters in abduction and 4.7 +/- 1.81 millimeters in adduction) and the change in strain was 13.3 per cent. With motion of the elbow, the mean total excursion was 12.3 millimeters (12.3 +/- 4.20 millimeters in flexion and zero millimeters in the resting position) and the change in strain was not measurable because of the wrinkle effect in flexion. With motion of the wrist, the mean total excursion was 5.6 millimeters (4.3 +/- 1.95 millimeters in extension and 1.25 +/- 0.81 millimeters in flexion) and the change in strain was 14.8 per cent. With motion of the fingers, the mean total, excursion was 3.4 millimeters (2.6 +/- 1.13 millimeters in hyperextension and 0.80 +/- 0.92 millimeter in flexion) and the change in strain was 10.3 per cent. Motion of the wrist and the fingers induced profound excursion of the median nerve at the wrist, whereas motion of the shoulder and the elbow induced marked excursion of the median nerve at the elbow. These excursions were much more pronounced when a number of joints were moved in a composite manner. Any factor that might limit normal excursion, such as scarring, could induce strains that could adversely affect the function of the median nerve. The finding that the position and movement of the limb had a profound effect on excursion and strain of the median nerve at the wrist and the elbow may aid in the understanding of the pathophysiology of median-nerve neuropathy.

A biomechanical comparison of four fixation methods of first metatarsophalangeal joint arthrodesis.

A simulated metatarsophalangeal joint arthrodesis was performed on 18 pairs of cadaveric great toes. One toe of each pair was fixed with a 4.0-mm oblique AO cancellous screw. The contralateral toe was fixed with one of three techniques: (1) a miniplate placed dorsally; (2) a 4.5-mm Herbert cannulated screw placed from the metatarsal neck into the medullary canal of the proximal phalanx; or (3) a 3/32-inch Steinmann pin placed longitudinally. An oblique 0.045 Kirschner wire was added with each method. The specimens were tested to failure in dorsiflexion. The miniplate was significantly stronger than the AO screw in force to failure and initial stiffness. The Herbert cannulated screw was also significantly stronger in force to failure than the AO screw. There was no significant strength difference between the Steinmann pin and the AO screw.

Condylar cartilage in the muscular dystrophic mouse.

The adaptability of condylar cartilage has been demonstrated previously after experimentally created functional alteration. This study was undertaken to examine the morphology of condylar cartilage in animals affected with a progressive muscular disease. Muscular dystrophic male mice (genotype: dy/dy, dy/+ x dy/+, Jackson Laboratory, Maine) and corresponding unaffected control mice were decapitated at ages 3, 6, 9, and 12 weeks, and their heads processed for histology. The cellular morphology of the condylar cartilage in the youngest age group was similar in dystrophic and control mice: the cartilage was a hypertrophic type. At ages 6 and 9 weeks, the maturational progression toward the nonhypertrophic form was observed in the dystrophic and control groups, the latter having flatter condylar heads. Differences were still evident at age 12 weeks. These observations were supported by measurements of the ratios of the mean cartilage thickness to condylar width (c/w), mean condylar height to width (h/w), and mean cartilage thickness to condylar height (c/h). This study supports the hypothesis that the adaptive nature of condylar cartilage may be regulated by the force levels to which the condyle is subjected.