Keywords
Upper Cervical Injury - nerve transfer - therapeutics
Introduction
The incidence of spinal cord injury is 40 new cases per million inhabitants, 50% of
which are due to traffic accidents and 25% to falls, and the most affected regions
are the cervical and lumbar spine. Injury at the C5-C8 level often presents strong
shoulder muscles, but it has no or weak control at the level of the elbow, wrist,
forearm, and hand, depending on the level of injury.[1] Cervical spinal cord injury produces severe disability, and although it represents
a small part of total patient care, it is very important.
The function of the hand is of utmost importance to obtain maximum independence in
daily life. Therefore, restoration of arm and hand function is the highest priority.[2] The surgical reconstruction of the upper limb began in the 1950s but was popularized
by Moberg in the 1970s through tendon transfers. To perform tendon transfers aimed
at restoring hand function, active wrist extension is required, which means that the
injury is below C5. This allows for the availability of several active muscles for
transposition.
Building on experience with nerve transfers in peripheral nerve and brachial plexus
surgery, the use of these techniques was proposed for the treatment of the tetraplegic
hand. One critical factor is the preservation of the second motor neuron below the
spinal cord injury. When the second motor neuron is preserved, nerve reconstruction
is not constrained by the time elapsed since the injury, as it is in peripheral nerve
injuries, where the second motor neuron segment is affected. In such cases, irreversible
muscle atrophy develops around 12 to 18 months after denervation, making nerve transfers
time sensitive. However, in spinal cord injuries, time may not be as critical for
the reasons mentioned above. In nerve transfers for spinal injuries, the upper motor
neuron connects to the intact lower motor neuron, meaning the procedure is not limited
by time. We present the clinical case of a male patient who underwent nerve transfers
to restore hand functionality.
Clinical Case
A 32-year-old man on June 26, 2021, presented trauma with an ASIA (American Spinal
Injury Association) spinal cord injury at level C4. From a motor point of view, there
is only the presence of brachioradialis with strength 5 on the right side and 4 on
the left side (Medical Research Council, MRC Scale).
Within the international classification for quadriplegic hand surgery (International
Classification for Surgery of the Hand in Tetraplegia, ICSHT), it would be type 1
([Fig. 1]). From a surgical perspective, tendon transposition options would not be viable,
except for a tendon transfer that provides elbow extension (posterior deltoid to triceps).
Fig. 1 International Classification for Surgery of the Quadriplegic Hand (ICSHT).
Performing nerve transfer surgery on the right upper limb is proposed together with
the patient.
Before surgery, an electromyogram was performed which indicated the presence of motor
units in the brachioradialis and the presence of mild denervation in the supinator,
but with motor units.
A triple nerve transfer is planned to provide elbow extension, wrist and finger extension,
and finger flexion dependent on the anterior interosseous nerve.
On March 2, 2022, this triple transfer was performed. A branch of the axillary nerve
to teres minor is transferred to the triceps; branches of the musculocutaneous nerve
to the brachialis are transferred to the fascicles of the anterior interosseous nerve
of the median; and branches of the supinator are transferred to the posterior interosseous
nerve. [Figs. 2] and [3]
Fig. 2 Location of the posterior interosseous nerve and branches of the supinator.
Fig. 3 Transfer of fascicles within the same radial nerve: branch of the supinator from
the radial nerve (C5-C6) to the posterior interosseous nerve (PIN) of the radial nerve
(C7-C8). Extension of the fingers and thumb.
After 15 days, the stitches and immobilizations are removed, and 4 weeks after the
intervention, weight-bearing and the start of the rehabilitation protocol are authorized.
Maintenance of articular arches and nervous stimulation of the muscles receiving nerve
transfers. Stimulation of the triceps muscles, finger and thumb extensors, and finger
flexors.
Results
3 months post-intervention, active wrist extension is evident, suggesting that the
transfer from the supinator to the posterior interosseous nerve is functioning. However,
no active function is observed in the triceps or hand flexors, likely due to the longer
distance to the target nerves.
At 7 months, follow-up with electromyography (EMG) shows spontaneous activity in the
triceps and extensor digitorum communis muscles. Motor unit potentials (MUPs) are
recorded with increased amplitude in the extensor digitorum communis, but no MUPs
are detected in the triceps.
At 9 months, wrist extensors score 4 on the MRC scale, and the extensor pollicis longus
score 2. However, no activity is observed in the wrist or hand flexors, and triceps
function remains questionable.
At 11 months, finger flexion begins to emerge, the thumb extension improves to 3,
and finger extension reaches a score of 2.
At 15 months post-intervention, the wrist and finger extensors are at 4, and the thumb
and finger flexor at 2. No motor activity is detected in the triceps.
The patient is very satisfied with the results and surgery on the contralateral limb
is proposed and accepted, in which the triple nerve transfer will be added to the
tendon transfer from the posterior deltoid to the triceps to achieve elbow extension.
Discussion
The recovery of arm and hand function in a quadriplegic patient is the highest priority
above the function of walking, sphincter control, or the sexual sphere.[3] For 49% of patients, recovery of the hand is essential compared to those who prefer
to recover another function, which stands at 13%.[3]
When cervical injuries are above C5, tendon options are practically non-existent and
therefore cannot be performed. Taking advantage of the experience accumulated in surgery
of the peripheral nerve and brachial plexus, nerve transfer surgery has been applied
in these patients to give function to the hand and arm. Although it seems like a promising
process, few quality studies support this treatment, although there is increasing
acceptance of this.
The problem of delimiting which nerves can be used for the transfer is something that
is being worked on, with the use of nerve conduction studies.[4]
Timing, patient selection, and long-term clinical outcomes remain unclear. There are
even indications that when there are difficulties in evaluating whether an injury
is of the upper or lower motor neuron, or there is a combination of both, the nerve
transfer should be performed within 12 months after the injury.[5]
The challenge lies in determining which nerves are viable for transfer. In our case,
surface electromyography was used to assess the presence of denervation, aiding in
preoperative planning. Intraoperative direct stimulation was then employed to evaluate
the response of the recipient muscle. In this patient, the transfer from the brachialis
to the anterior interosseous nerve was the first to show function, followed by the
transfer from the supinator to the posterior interosseous nerve. However, the transfer
from the teres minor branch to the triceps remains uncertain.
This makes us propose two things: try to refine preoperative planning further by applying
other electrodiagnostic studies, such as nerve conduction studies, looking at the
compound muscle action potential, since the electromyogram in long-standing spinal
cord injury can be distorted and the results not be completely reliable.[6] And on the other hand, associating tendon transfer with the nerve transfer, in cases
where it is possible, such as providing extensor function to the triceps, in which
apart from performing the nerve transfer of the axillary branch for the teres minor
to the triceps, associating the posterior deltoid tendon transfer to triceps, in the
attempt to ensure this function, there are already references of this possibility.[4]
The option of combining tendon and nerve transfers is a solution that is being increasingly
considered. Not only in “reinforcement” situations[4], as would be our case, but also in which a tendon transfer could be used to perform
a movement and add a nervous movement to achieve other movements and complement the
function of the hand, adapting the tendon transfer to the degree and distribution
of reinnervation achieved.[7]
Conclusion
Nerve transposition is a technique that can offer therapeutic options within surgical
treatment that tendon transposition cannot provide, and it may even enhance the effectiveness
of tendon transfers.
It is essential to continue with follow-up and the comprehensive treatment we are
providing.
