AAHS ASPN ASRM - 2013 Annual Meeting - American Association ...

TEM Chracteristic of Vibration Injury in Peripheral Nerves
Institution where the work was prepared: Medical College of Wisconsin, Milwaukee, WI, USA
ji-Geng Yan, MD; Hani S. Matloub; Lin-Ling Zhang; James R. Sanger; Danny A. Riley, PhD; Medical College of Wisconsin
INTRODUCTION:
This study was to determine pathological feature of vibration injury to the peripheral nerves.
MATERIALS AND METHODS
24 male Sprague-Dawley rats were randomly divided into two groups: sham control and vibrated. Customized Vibrating Platform: A smaller vibrating
platform(frequency 43.5 Hz, amplitude 1.5mm); A larger no-vibrating platform. Methods: Rats were anesthetized and their hind limbs fixed to the vibrating
platform by Velcro loops. The remainder of the body rests on the no-vibrating platform. The rats were vibrated 4 hours/day, for 7 days. At the end day sciatic
nerves from both groups were harvested after perfusion using glutaraldehyde. Neural Fixation: The aorta was cannulated and perfused. The tissue was subjected
to post fixation by placing it in a buffered solution of osmium tetroxide with a 1.5% concentration of potassium ferricyanide added to the buffered
osmic acid mixture. Then the neural tissue was submitted for light and electron microscopy.
RESULTS:
While light microscopy showed minimal histologic differences between vibrated and control nerves, the changes revealed by electron microscopy were dramatic.
After 2 days-vibration these included thickening of the epineurium, thickening of the myelin sheath ruptured gap between the mylins, and many vacuoles
were seen in the plasma. These changes were found in all vibrated animals. After 7 days-vibration myelin balls, consisting of destroyed myelin rolled into woollike
threads, were located inside the myelin layers. Axonal damage was seen in both myelinated and nonmyelinated axons.In addition, nonmyelinated axons
were edematous. An interesting finding was the circumferential disruption of several myelin layers, leaving a large circular space around the impacted myelin
with central axonal constriction. This chracteristic finding, giving the appearance of a finger ring, was found in every vibrated nerve. Many microtubes and
microfilaments were ruptured or had disappeared.
DISCUSSION
Compared to control nerves, the vibrated nerves show definite pathologic changes in the form of axonal damage and myelin fragmentation Furthermore, axonal
damage is seen in both myelinated and nonmyelinated axons. We therefore conclude: 1) Myelin disruption, myelin balls, myelin “finger ring” changes, and
axonal vacuoles are identifiable characteristics of the neuropathological changes due to vibration injury. 2) The neuropathological changes probably occur in
the following sequence. First the myelin sustains impacting force by vibration and becomes thick; next, there is partial rupture of the myelin; third, myelin balls
or “finger rings” form; finally, constriction impedes, then destroys axoplasma. Further research to identify the hazardous components of vibration (amplitude,
frequency, etc.)
Peripheral Nerve Injury after Hallux Abducto Valgus Surgery
Institution where the work was prepared: Ankle and Foot Institute of Arizona, Tucson, AZ, USA
Jerome K. Steck, DPM; Ankle and Foot Institute of Arizona
Hallux valgus (bunion) surgery is very common, According to the National Health Interview survey conducted by the National Center for Health Statistics; this
condition affects 1% of adults in the United States. Gould et al found that the incidence increased with age, with rates of 3% in persons aged 15-30 years,
9% in persons aged 31-60 years, and 16% in those older than 60 years.
Gould et al also reported a higher incidence in females versus males, with ratio of 4:1. Approximately 10%-20% of patients with bunions eventually have them
surgically treated. Of these, 10% have a complication almost half of which are related to peripheral nerve damage.
From November 2003 through May 2006 twenty-four patients with peripheral nerve damage after bunion surgery were treated surgically for severe pain after
failure of conservative care. There were twenty females and four males. All patients had exploration of the peripheral nerve most likely producing their symptoms
and in our series included the deep peroneal, superficial peroneal, medial plantar, and their branches.
Nineteen patients (79%) had a peripheral nerve entrapped in scar tissue. The etiology of the remaining 6 (21%) included irritation of hardware 2 (8%), stump
neuroma from transected nerve at initial procedure 2 (8%), and undetermined 2 (8%).
Fifteen patients (63%) had a successful outcome with exploration and decompression of the affected nerve, the remaining 9 patients (37%) required a denervation
due to irreparable damage to the nerve. Twenty one patients (88%) rated their results as excellent and the remaining 3 patients (12%) were fair. Five
patients had a second surgery (denervation) after an attempt at decompression.
Complications after hallux valgus surgery are common. Many foot and ankle surgeons overlook peripheral nerve damage as a possible etiology of these complications.
This paper looks at the surgical treatment of twenty-four of these complex patients with promising results.
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