Floor plan - 2013 Annual Meeting - American Association for Hand ...

ASPN SCIENTIFIC PAPER SESSION C
Grip Strength and CMAP Amplitude in Median Nerve Injury of the Rats
Institution where the work was prepared: Mayo Clinic, Rochester, MN, USA
Huan Wang, MD, PhD; Eric J. Sorenson; Robert J. Spinner; Anthony J. Windebank; Mayo Clinic
INTRODUCTION:
Grip strength is a measurement of finger flexor power and therefore reflects motor function of the median nerve which innervates finger
flexors in rats. The aim of the study is to develop atraumatic recording of compound muscle action potential (CMAP) of median
nerve and validate its reliability by correlating CMAP amplitude with grip strength.
METHODS:
12 Sprague Dawley rats were used. In one group median nerve transection and repair was done. Transection and direct coaptation of
both median and ulnar nerves was done in the other group. CMAP was recorded by placing a subcutaneous needle electrode at the
thenar muscle while the median nerve was percutaneously stimulated at the cubital fossa. A grasping task was carried out to measure
grip strength. These measurements were conducted preoperatively and postoperatively after 1, 3, 4, 6, 8, 10, 12, and 16 weeks.
Relationship between recovery of CMAP amplitude and recovery of grip strength was assessed by plotting grip strength against CMAP
amplitude. To further determine if there is any correlation between this pair of variables, correlation coefficient was examined by nonlinear
regression curve fit of these two sets of data.
RESULTS:
Reproducible median nerve CMAP was recorded in both groups. Following nerve transection CMAP disappeared and did not return
until 4 weeks after nerve repair. CMAP dispersion, amplitude deterioration, area deterioration and prolonged onset latency were seen
during early regeneration period. The amplitude gradually increased as post-operative time passed and did not reach pre-operative
level until 16 weeks. Following median nerve transection, flexion of forepaw digits was lost and grip strength was not measurable. Digit
flexion was observed 3 weeks postoperatively and grip strength gradually recovered and returned to pre-operative level 12 weeks postoperatively.
Visual correlation between grip strength and median nerve CMAP amplitude in both groups showed similar pattern of
recovery with time. Recovery of CMAP amplitude lagged behind recovery of grip strength. Nonlinear regression of CMAP amplitudegrip
strength curve followed a hyperbolic shape. R squared of the curve fit in median nerve injury group was 0.91 while r squared of the
curve fit in combined median and ulnar nerve injury group was 0.93. This demonstrated a strong correlation between grip strength and
median nerve CMAP amplitude.
CONCLUSION:
CMAP is a valid parameter that shows typical time course of nerve regeneration and motor function recovery. To our knowledge it is
the first report of conducting CMAP measurement in rat forelimb.
Nerve Transfers For Paralysis Of The Tibialis Anterior Muscle (Foot-Drop)óA Cadaveric
Feasibility Study
Institution where the work was prepared: Teaxs Tech University Health Science Center, El Paso, TX, USA
Miguel Pirela-Cruz, MD; D.A. Terreros; U.D. Hansen, MD; P. West, MD; A.D. Rossum, MD; Texas Tech University HSC, El Paso
INTRODUCTION:
Nerve transfers for upper extremity neurological problems is now an accepted treatment option for addressing some motor and sensory
deficits. However this treatment option for reconstructing peripheral lesions of the lower extremity is limited. This study is an
attempt to explore the possibility of restoring motor function of the tibialis anterior (TA) muscle following an irreparable traumatic injury
to the common peroneal nerve that results in a foot-drop.
MATERIALS/METHODS:
Eight caderveric legs, disarticulated at the hip, were studied. Specimens included 4 male and 4 female with an average age 51 and 47
years respectively. Three nerves were evaluated as possible donors; the branch to the soleus muscle, branch to the medial and to the
lateral gastrocnemius muscle.
RESULTS:
Nerve transfer using the interosseous route could be accomplished for each of the donor nerves. The average working length of the
branch to the tibialis anterior (BTA) was 96 mm +/- 8.9. All nerve transfers with the exception of one could be performed without an
interpositional nerve graft. The average repair site to TA was 73.5 mm, 66.6 mm, 46.6 mm for the medial gastrocnemius, lateral gastrcnemius
and soleus respectively.
CONCLUSION:
Successful mobilization of the BTA can be accomplished through a fibula and interosseus windows to reach to potential donor nerves.
These finding may have significant clinical benefits pertaining treatment for traumatic foot drop.
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