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Nerve Transfers

Recently, the literature is publishing information regarding the surgical procedure of nerve transfers which is evolving as an alternative procedure compared to tendon transfers for improving the functional ability of the hand and upper limb post SCI (Keith & Peljovich 2012). A nerve transfer involves the repair of distal denervated nerve element by using a proximal foreign nerve as the donor of neurons and their axons to re-innervate the distal targets (Addas & Midha 2009; Brown et al. 2012; Midha 2004). The transfer involves sacrificing the function of a lesser valued donor nerve to revive function in the recipient nerve and muscles, which is considered functionally more critical than the donor nerve (Senjaya & Midha 2013).

Senjaya and Midha (2013) and Midha (2004) described and listed the fundamental principles, advantages and potential drawbacks of nerve transfers when compared to tendon transfers in a review article and they are summarized in the following;

Table 24 Advantages and Disadvantages of Nerve Transfers

Advantages of  Nerve TransfersDrawbacks of Nerve Transfers
·       Less surgical dissection, recovery time and scarring (Brown 2012; Keith & Peljovich 2012).·       When an improperly selected donor nerve with suboptimal function is transplanted it may significantly downgrade function (Senjaya & Midha 2013).

 

·       Only one surgical procedure to reconstruct finger flexion and extension (Revol et al., 2002; Brown 2012).

 

·       The donating muscle may be entirely denervated and lose its function (Senjaya & Midha 2013).
·       Decreased dependence on care for ADL after surgery (Bertelli et al., 2011; Brown 2012; Hentz 2002).

 

·       Central motor re-education is challenging, especially for nerve transfers from non-synergistic nerves (Senjaya & Midha 2013).
·       Less restrictive immobilization after surgery, with less pain and minimal loss of muscle function (Brown 2011; Brown 2012).

 

 
·       Greater functional gains (Brown 2011; Brown 2012; Brown et al., 2012).

 

 
·       Multiple functions may be activated by a single nerve (Brown 2011; Brown 2012; Midha 2004). 

Table 25 Nerve Transfer Interventions

Author Year

Country
Research Design

Score
Total Sample Size

MethodsOutcome
Fox et al., 2015b

USA

Cohort

N=7

Population: Mean Age: 28 yr; Gender: males=6, females=1; Level of Injury: C4=2, C5=2, C6=3; Severity of Injury: AIS A=4, AIS B=2, AIS C=1.

Intervention: Patients receiving nerve transfer surgery completed assessments and self-reports, and were prospectively followed-up over a minimum of 12 mo. Nerve tissue was also collected during surgery. Surgeries included Brachialis (BR) to the anterior interosseous nerve (AIN; n=7), BR to the flexor carpi radialis (FCR; n=5), BR to the flexor digitorum superficialis (FDS; n=3), supinator to extensor carpi ulnaris (ECU; n=1), supinator to posterior interosseous nerve (PIN; n=1), deltoid-to-triceps (n=1), and exploratory surgery (n=1). Assessments were conducted at baseline and at 2,4 and 12 wk post-surgery.

Outcome Measures: Medical Research Council elbow flexion grade (MRC), Histomorphometric analysis, Complications post-surgery, Functional gains reported by patients.

1.      Histomorphometric analysis revealed excellent functioning of the transferred nerves.

2.      One patient experienced a reduced fiber density, heterogeneity of fibers, and imperfect architecture of the nerve cell after histomorphometric analysis, however, this patient was found to have low motor neuron involvement at the time of surgery.

3.      No patients experienced a decline in postoperative functioning compared to baseline functioning according to MRC scores.

4.      One patient who underwent deltoid-to-triceps transfer experienced postoperative weakness of the deltoid (MRC grade 4) but eventually subsided and strength returned to baseline levels (MRC grade 5).

5.      Functional gains as according to patient self-reports included an improvement in grasp strength (n=2), greater wrist stability (n=1), an improvement in pinch activity (n=1), and greater use of their hand for activities such as feeding and using a cell phone (n=1).

6.      Two patients did not report any changes in functioning from pre-surgery to post-surgery.

7.      Four patients experienced minor complications including paresthesia of the thumb (n=2), hypesthesia of the thumb (n=1), and a seroma which required drainage (n=1).

8.      Two patients experienced major complications including urosepsis (n=1) and a urinary tract infection (n=1).

Bertelli et al., 2017

Brazil

Pre-Post

N=9

Population: Mean age=28±15 yr; Gender: males=8, females=1; Time since injury: 7.6±4 mo; Level of injury: C5 – C7; Severity of injury: AISA A=9.

Intervention: Participants received nerve transfer surgery for restoration of finger flexion in 17 upper limbs of nine patients. In three upper limbs, the nerve to the brachialis was transferred to the anterior interosseous nerve (AIN). In five upper limbs, the nerve to the brachialis was transferred to median nerve motor fascicles innervating finger flexion muscles in the mid arm. In four upper limbs, the nerve to the brachioradialis was transferred to the AIN. In the remaining five upper limbs, the nerve to the extensor carpi radialis brevis (ECRB) was transferred to the AIN. Outcome measures were assessed at baseline and 16±6 mo.

 

Outcome Measures: Manual muscle test (range of finger flexion and strength).

1.     A recovery of M3 or better in finger flexion strength was observed in 10 out of 17 surgically treated limbs.

2.     Restoration of finger flexion was observed in four out of eight upper limbs in which the nerve to the brachialis was used; Range of motion was incomplete in all five of these limbs and strength was greater than M3 in all limbs.

3.     Full finger flexion with M4 strength was observed in all five upper limbs, where the ECRB was transferred to the AIN.

Bertelli et al., 2015

Brazil

Post-Test

N=7

Population: Mean age: 26 yr; Gender: males=6, females=1; Level of injury: complete C-6=7; Mean ASIA motor score: 15.8±3.9; Mean time since injury: 7 yr.

Intervention: 27 recipient nerves. Elbow, thumb and finger extension reconstruction via nerve transfer was performed on patients with midcervical spinal cord injuries on average 7 mo post injury and outcomes were reported.

Outcome Measures: British Medical Research Council scale (BMRC).

1.     At time of final postoperative assessment, elbow extension scored BMRC Grade M4 and under full voluntary control in 11 upper limbs (UL) and in 2 UL within same patient, elbow extension scored Grade M3.

2.     A BMRC Grade M4 for full thumb extension with wrist in neutral was observed in 8 UL and 4 hands had thumb extension that scored M3.

3.     Full metacarpal extension scoring M4 was demonstrated in 12 hands.

4.     Finger extension scoring M3 with only partial range of motion at the metacarpal phalangeal joint was observed in the remaining 1 limb.

5.     All patients improved at self-transferring and controlling their wheelchairs.

6.     After surgery, all patients extended their thumb and fingers without restriction, no decreased function at donor sites and no patient lost abduction strength or shoulder range.

Fox et al., 2018

USA

Case Series

N=36

Population: <1 yr post SCI: Mean age=36.1±16 yr; Gender: males=7, females=2; Time since injury: <1 yr; Level of injury: not reported; Severity of injury: not reported.

>1 yr post SCI: Mean age=38.8±17 yr; Gender: males=22, females=5; Time since injury: >1 yr; Level of injury: not reported; Severity of injury: not reported.

Intervention: No intervention. Medical records of patients were reviewed to develop a diagnostic algorithm, focusing on electro diagnostic studies (EDX), to determine eligibility for nerve transfer surgery based on time of injury.

Outcome Measures: EDX data.

1.      Although no statistics were reported, a substantial number of patients presenting years after SCI are candidates for nerve transfers based on EDX data.
Simcock et al., 2017

New Zealend

Case Series

N=53

Population: Age range=15 to 80 yr; Gender: males=50, females=3; Time since injury: <1 yr; Level of injury: C2 – C8; Severity of injury: AISA A=21, B=19, C=8, D=5.

Intervention: No intervention. Case note review of medical records from 2007 to 2012 to identify patients that may benefit from nerve transfer surgery. Outcome measures were assessed at six wk, 12 wk and one yr following injury.

Outcome Measures: Neurological assessment.

1.     Nerve transfer within 3 to 12 mo of injury provides active hand opening for patients following cervical SCI.

2.      Neurological assessment identifies patients who may benefit from nerve transfer surgery to improve hand opening.

Fox et al., 2015c

USA

Case Series

N=9

Population: Mean Age: 32.9 yr; Gender: males=7, females=1.

Intervention: Data was collected on patients who had received nerve transfer surgery and had been followed-up over a period of 12 mo. 20 surgeries were performed which included Brachialis (BR) to the anterior interosseous nerve (AIN; n=7), BR to the flexor carpi radialis (FCR; n=3), deltoid-to-triceps (n=3, 15%), BR to the AIN/flexor digitorum superficialis (FDS; n=1), BR to the FDS/FCR (n=1), BR to the AIN/FCR (n=1, BR to extensor carpi radialis (n=1), supinator to extensor carpi ulnaris (n=1), supinator to posterior interosseous nerve (n=1), and exploratory surgery (n=1). Assessments were conducted every 3 mos until 12 mos post-surgery.

Outcome Measures: Functional gain self-reports by patients, Medical Research Council elbow flexion grade (MRC), Complications post-surgery.

1.     Functional gains were reported from 6mos onwards according to patient self-reports which included increased grasp strength (n=2), an increased use of their hand for feeding (n=2), an increase in wrist stability (n=1), and improvement in pinch activities (n=1).

2.      Three patients reported no changes or improvements since surgery.

3.      All patients achieved grades of 1-3 on the MRC indicating a trace of contraction, active movement with gravity eliminated, and active movement against gravity respectively.

4.      Complications post-surgery included paresthesias of the thumb (n=3), urinary tract infection with sepsis (n=1), and seroma (n=1).