Background: Controlled joint extension followed by gradual
distraction with use of an external fixator may facilitate primary repair of
peripheral nerve defects by permitting end-to-end repair without tension. The
hypothesis of the present study was that gradual lengthening of nerve repairs
with use of incremental distraction would provide superior results compared
with grafting or repair under tension.
Methods: A median nerve segment measuring four times the diameter of
the nerve was resected in thirty-six rabbits to create a 7-mm gap in the
nerve. Neurorrhaphy was performed with use of one of three techniques. In
Group 1 (cable graft), a tension-free medial antebrachial cutaneous graft was
placed to allow full range of motion of the elbow postoperatively. In Group 2
(end-to-end repair without distraction), the elbow was externally fixed in
hyperflexion and the nerve was repaired end-to-end. At fourteen days, the
fixator was removed and unprotected elbow motion was permitted. In Group 3
(end-to-end repair with gradual distraction), the elbow was externally fixed
in hyperflexion and primary neurorrhaphy was performed. At fourteen days, the
elbow was extended 10° every other day with use of the articulated
external fixator until full extension was achieved. Median nerve amplitude,
latency, and nerve-conduction velocity; flexor digitorum superficialis
single-twitch force generation and maximum tetanic force generation; muscle
mass; and elbow range of motion were measured at three or six months. In
addition, histologic analysis of the median nerve distal to the repair site
and the morphometry of the neuromuscular junction in the flexor digitorum
superficialis were performed at six months.
Results: All rabbits regained full active and passive range of
motion. At three months, the nerve-conduction velocities in Groups 2 and 3
were significantly greater than that in Group 1. At six months, the
nerve-conduction velocities and amplitudes in Group 3 were significantly
greater than those in Groups 1 and 2. At six months, the tetanic force in
Group 3 was significantly greater than those in Groups 1 and 2. There were no
significant differences in muscle mass among the groups. There were no
significant differences in histological findings among the three groups,
although there was a trend toward larger fiber size in Group 3 as compared
with the other two groups. The neuromuscular junctions in Group 3 had a
significantly larger surface area than did those in Group 1 (p = 0.002) and
Group 2 (p = 0.034).
Conclusion: The use of an articulated external fixator and
controlled gradual distraction appears to facilitate the treatment of
peripheral nerve defects.
Clinical Relevance: This nerve repair technique may prove useful in
clinical situations involving peripheral nerve defects.