This document summarizes a journal club discussion on outcomes of using anterior interosseous nerve transfers to restore intrinsic hand function after high ulnar nerve injuries. The summary includes: - A study of 17 patients who underwent AIN to MUN nerve transfers for high ulnar nerve injuries found 81% achieved MRC grade 3 or higher recovery of intrinsic function. Three techniques were used for the nerve coaptation. - A literature review identified 12 similar studies with 102 total patients, finding 86% had good outcomes (MRC grade 3 or higher) and 64% had good sensory outcomes. - Distal nerve transfers provide a more functional reconstruction than tendon transfers for restoring intrinsic hand function after high ulnar

1. JOURNAL CLUB
on
Outcomes of anterior interosseous
nerve transfer to restore intrinsic
muscle function after high ulnar
nerve injury

3. Introduction
• Ulnar nerve injuries have a 71% lower chance of motor recovery
when compared to the median nerve for similar injuries.
• Repair of a high ulnar nerve injury would not result in useful recovery
of intrinsic musculature in an adult.
• The likely reason for this is that the long re-innervation distance in a
mixed nerve would result in an irreversible collapse of the
intramuscular neural plexus, end plate degeneration, and muscle fibre
atrophy and fibrosis.
• This leaves the patient with a loss of dexterity, weakness of grip,
sensory loss, and a noticeable functional and aesthetic
“claw”deformity

4. • The “claw”posture becomes more obvious as the more proximal FDP re-
innervates and the unopposed action of the extrinsic flexors and
extensors causes hyperextension of the MCP joint with interphalangeal
joint flexion.

5. • Tendon transfers were historically used to rebalance the hand, but
they are physically limited by the principles of singular, linear
function, and struggle to emulate the natural, intricate multi-faceted
functionality of the intrinsics.

6. • Nerve transfers have been gaining popularity over the last 2 decades
for the treatment of high ulnar nerve injuries, repopulating the distal
endoneurial tubes with expendable donor axons, providing some
early muscle reinnervation.
• The most popular and practical of these is the anterior in- terosseus
nerve (AIN) to motor branch of the ulnar nerve (MUN) transfer.

7. Methods
• During the period of 2011–2018, 17 consecutive patients, who underwent
AIN to MUN nerve transfers for high ulnar nerve injuries, were evaluated.
• Inclusion criteria
All traumatic aetiology for ulnar nerve injury at the proximal forearm,
elbow, and above elbow levels
non-in-continuity lesions from oncological resection.
Traction injuries with at least a Sunderland grade IV with no intraoperative
stimulation across the ulnar nerve
• All patients that underwent distal AIN to MUN transfer for compression
and other in-continuity lesions were excluded.

8. ANALYSIS WAS DONE FOR:
• patient demographics
• Mechanism and level of injury
• Interval between injury and nerve transfer
• Nerve transfer techniques
• Time to recovery
• Follow up period
• Objective outcomes using the British Medical Research Council (BMRC)
motor strength grading for intrinsic musculature.

9. SURGICAL TECHNIQUE

12. Results
• In the 7-year study period, 16 patients (15 males and 1 female) met
the inclusion criteria as one patient was lost at follow-up
• Mean follow-up period : 17 months (range 12–18)
• Average age patients: 39.4 (range 19–77, SD = 19.7)
• The median delay between injury and the nerve transfer procedure
was 0.8 months

13. • Site of injuries were above the elbow in 5 cases (31.3%), at the level
of the elbow in 8 cases (50%) and at the proximal forearm level in 3
cases.
• Mechanism of injury included sharp transection of the nerve in 63.5%
of cases (10/16), blast injuries in 18.75% (3/16), 2 cases of traumatic
traction, and one case of a post traumatic neuroma resection which
was included as a full-thickness segment of the nerve was removed.

14. • There were three main techniques of nerve coaptation:
Conventional end-to-end (ETE) neurorrhaphy (7/16, 43.8%)
Hemi ETE where a few fascicles in the MUN were coapted to the terminal
AIN ETE (7/16, 13.8%)
Supercharged end-to-side (SETS) which is a true reverse end-to-side
(RETS) through an epineural window in the ulnar nerve motor branch.

15. • Five out of sixteen patients achieved MRC 4 and above (31%)
• 13/16 achieved MRC grade 3 or above (81%) recovery for intrinsic.
• One patient had residual clawing at 12 months follow-up, but was not
seen at 18 months.
• 3 patients (18.8%) had mild clawing at 18 months
• Of the twelve patients with no clawing, two had a positive Froment’s
test and two had a residual Wartenberg’s sign at 18 months.

16. • When looking at age in relation to outcomes very weak positive
correlation which was statistically insignificant (p-value = 0.64) was
noticed.
• There was a stronger positive correlation between the interval
between injury and nerve transfer , but this again was not significant (
p -value = 0.09).

17. • 12 studies were identified from similar published literature resulting in a
total of 102 patients including our series.
• All the studies employed the use of the AIN transfer to the MUN, either
alone or combined with a sensory transfer.

18. • Thirteen patients had injuries to the UN at the proximal forearm level,
37 were at the elbow, and 52 were in the arm or higher.
• The mean time to surgery for all patients was 5.17 months
• The average follow-up time was 20.72 months.

19. • Good outcomes (M3 or above) were obtained in 86% of patients and
of the 55 patients that had sensory transfers, and good outcomes (S3
+ or above) were obtained in 64% of patients.
• Although some of our patients had concurrent sensory nerve
transfers, the numbers were small and we did not include this as part
of our review.

20. Post-operative regimes
• The coaptation is completed without tension and adjacent joints are
put through a full ROM on the table.
• We usually use bulky dressings for the first 5–7 days with the addition
of a neutral wrist splint.
• After debulking of the dressing, a gentle range of movement exercises
is encouraged to facilitate nerve excursion and prevents subsequent
scarring.

21. Discussion
• In 1997 Wang and Zhu first described using the PQ branch of the AIN
to the MUN to restore intrinsic hand function for amputation injuries
at the wrist.
• Battiston used this technique specifically for high ulnar nerve injuries
and combining it with a distal sensory nerve transfer.

22. • The lack of correlation between delay to surgery and outcomes is not
all together unexpected as most of our nerve transfers were
performed acutely within a few days to months.

23. • A majority of our patients would receive FDP buddying along with the
nerve transfer which is a reliable method to improve grip strength.
• Other adjunctive procedures include correction of the Wartenberg’s
deformity and MCP joint capsulodesis with volar plate advancement

24. Study limitations
• Numbers of suitable cases are small and a large multicentre study
would be required.
• We did not review the sensory nerve transfers or look at sensory
outcomes in our patients
• Lack of patient reported outcome data being retrospective in nature.

25. CONCLUSION
• Distal nerve transfers provide a more functional and anatomical
reconstruction than tendon transfers.
• a recent survey of 62 surgeons from around the world showed 88%
used nerve transfers more frequently in the last 3 years.
• The AIN to motor branch nerve transfer proves to be a reliable
method of regaining intrinsic function in high ulnar nerve
• injuries with good motor recovery in 81.3% of our patients that
underwent the procedure, echoing other studies.
• research is needed to prove the efficacy of ETS neurorrhaphies and
the most effective technique for this.

26. • THANK YOU