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.

Vascular anatomy of the ulna.

The vascular anatomy of the ulna was studied. Ten fresh-frozen upper extremity specimens were injected with India ink and latex solution. The extraosseous anatomy was dissected. The intraosseous anatomy was evaluated after treatment with the modified Spalteholtz technique. The proximal periarticular portion of the ulna was supplied by numerous, very small periarticular branches running in the capsule. A major intramedullary nutrient vessel arose from the ulnar artery or ulnar recurrent artery in all specimens and entered at the base of the coronoid. The ulnar artery gave off a common interosseous artery that branches into posterior and anterior interosseous vessels that course distally on the interosseous membrane. The interosseous vessels were critical for they supply the only observed vascular branches to the ulna diaphysis. The anterior interosseous vessel supplied on average 7 branches (range, 3-11 branches) to the ulna diaphysis spaced at generally regular 2-cm intervals, with the number of branches decreasing in the distal third. The posterior interosseous artery supplied an average of 11 branches (range, 9-14 branches) to the ulna diaphysis spaced at 1-cm intervals. The distal ulna metaphysis was supplied by terminal branches of the anterior interosseous artery. The ulnar head was supplied by small branches off the ulnar artery proper. In summary, the blood supply to the ulna diaphysis was dependent on segmental vessels provided by the anterior and posterior interosseous vessels. No dominant intramedullary vessel was observed in the diaphysis. The interosseous vessels should be protected when treating a ulna fracture or a nonunion, or when performing an osteotomy.

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.

Biomechanical analysis of a new anterior spine implant for post-corpectomy instability.

Corpectomies in the lumbar and thoracic spine are sometimes necessary in the treatment of vertebral tumor, trauma, and degeneration. The resultant defect creates marked instability. Present methods to correct this problem involve spanning the defect with structural bone graft and applying either anterior or posterior instrumentation. Some investigators have designed vertebral replacements that distract and wedge into the corpectomy site. This study investigates a proposed prosthesis with a unique method of fixation: a vertebral replacement is fixed to the bodies above and below by screws that are oriented rostrally and caudally. This fixation prevents cantelever bending of the screws, migration of the implant, and possibly visceral damage by the placement of the device. This study investigates the biomechanical performance of this device in flexion, extension, and axial loading in a calf spine model. In comparison with normal spines, this device restored the biomechanical strength of the spine to at least normal levels in all planes tested. It appears that a device of this design may be useful for the reconstruction of vertebral diseases and may reduce the need for more extensive surgeries.

Freeze-dried segmental fibular allografts in azathioprine-treated dogs.

The successful use of a bone allograft may be negated by the host's immune response. This investigation assessed the efficacy of combining freeze-dried cortical allografts in three to six weeks azathioprine-immunosuppressed dogs. Forty-eight of 94 adult mongrel dogs were initiated for this study, and 46 of 94 were previously published and recompiled. The dogs were divided into five groups and followed for six months: Group I consisted of bilateral fresh autografts as an external control; Group II assessed the effect of freeze-drying on autogenous bone; Group III compared fresh autografts with fresh allografts; Group IV assessed the effect of freeze-drying on allografts; and Group V assessed the combined effect of placing freeze-dried allografts in immunosuppressed hosts. Biweekly roentgenograms were made to evaluate the time to union and the incidence of graft fatigue failure. Mechanical graft strength was assessed by rapid torsional loading to failure at the time of sacrifice. Biologic repair was assessed with the use of tetracycline and microradiographic techniques. The incorporation and repair of a fresh cortical autograft is better than that of a freeze-dried autograft because of fractures, nonunion, or delayed union of graft-host junctions; freeze-dried autografts have increased peripheral and internal resorption, yet an increased peripheral bony callus maintains normal graft strength; freeze-dried and fresh allografts are similar in roentgenographic characteristics, mechanical strength, and in the mechanism of graft incorporation; the use of three or six weeks azathioprine therapy did not improve the fate of freeze-dried allografts.

A roentgenographic, biomechanical, and histological evaluation of vascularized and non-vascularized segmental fibular canine autografts.

Advocates of vascularized bone grafts believe that these grafts should have a decreased time to graft-host union, and that they should be mechanically stronger than conventional (non-vascularized) grafts. The objectives of the present study were to determine the rate and pattern of repair in vascularized autogenous cortical bone grafts, to determine the mechanical strength of the grafts, and to correlate the mechanical strength with the biological repair. Forty-nine adult male mongrel dogs were divided into six groups to evaluate conventional (non-vascularized), cuff (periosteal-encased, non-vascularized), and vascularized segmental grafts. The fibula was the site of experimentation and all grafts were four-centimeter cortical segments. The vascularized and conventional grafts were analyzed at two, six, twelve, and twenty-four weeks. The cuff grafts were analyzed at twenty-four weeks and were compared with conventional grafts to assess the effect of the periosteal soft tissue. Roentgenograms were made every two weeks to evaluate the time to union. The mechanical strength of each graft was assessed by determining rapid torsional load to failure. Biological repair was assessed by tetracycline labeling for new-bone formation and by microradiographic techniques for porosity and cross-sectional areas. The study showed that conventional and cuff grafts were similar in terms of mechanical and biological repair at six months. At all sampling intervals, the vascularized grafts exhibited histological findings that were consistent with viability. The conventional and vascularized grafts underwent different mechanisms of repair. The conventional, non-vascularized grafts healed by peripheral and internal resorption followed by callus encasement and osteonal remodeling.(ABSTRACT TRUNCATED AT 250 WORDS)

Intraosseous blood supply of the capitate and its correlation with aseptic necrosis.

Isolated capitate fractures that result in the development of aseptic necrosis of the proximal pole are uncommon. Five patients were treated who developed aseptic necrosis of the proximal pole. Four had a history of trauma with radiographic evidence of nonunion. In vitro arterial injection studies were done to correlate clinical problem with intraosseous capitate vascularity. Palmar vessels were found to contribute the majority of the blood supply to the capitate. Three patterns of intraosseous blood supply were seen. In each pattern, the proximal pole received its blood supply exclusively in a retrograde fashion across the capitate waist analogous to the proximal scaphoid. Aseptic necrosis without collapse of the proximal pole was successfully managed with curettage and bone grafting in three patients. The remaining two patients, with collapse and pericapitate degenerative changes, were managed with intercarpal fusion.

Freeze-dried allogeneic segmental cortical-bone grafts in dogs.

Forty-four adult male mongrel dogs were used to compare segmental cortical freeze-dried allogeneic bone grafts with fresh autogenous, freeze-dried autogenous, and fresh allogeneic segmental cortical grafts. Group I consisted of bilateral fresh autografts as external controls; Group II, a fresh autograft on one side for internal control and a freeze-dried autogenous graft on the other side to evaluate the effect of freeze-drying on repair; Group III, a fresh autograft on one side and a fresh allograft on the other side to measure the differences between autogenous and allogeneic grafts; and Group IV, a fresh autograft on one side and a freeze-dried allogeneic graft on the other to see if freeze-drying altered the repair of allogeneic grafts. The grafts were analyzed qualitatively over a six-month period by the use of interval roentgenograms to determine the times of graft-host union and the incidence of fatigue fractures. Six months after operation, the repair processes in the four groups were compared quantitatively with respect to biological repair and physical strength using torsional stress-testing, tetracycline labeling, and microradiography. The results indicate both qualitatively and quantitatively that: (1) fresh bilateral segmental cortical autografts show reproducible characteristics, so that the canine fibula furnishes a satisfactory model (Group I); (2) freeze-drying does not inhibit the repair process per se (Group II); (3) fresh allografts are rejected in varying degrees of intensity (Group III); and (4) freeze-drying does not protect cortical allogeneic grafts from such rejection (Group IV).