Abstract: Investigation into the Optimal Number of Intercostal Nerve Transfers for Musculocutaneous Nerve Re-Innervation
Bibliographic record
Abstract
INTRODUCTION: Intercostal nerve transfer is one approach to neurotize the musculocutaneous nerve in brachial plexus injury. This study investigates outcomes following intercostal nerve transfer with a primary focus on the number of nerve transfers required to achieve optimal return of elbow flexion. MATERIALS AND METHODS: A systematic review of the literature was performed in accordance with PRISMA guidelines searching the MEDLINE/Pubmed and Google Scholar databases. Studies investigating intercostal nerve transfer for musculocutaneous innervation following brachial plexus injury in adults were included.1–5 Citations were cross-referenced and relevant studies included for analysis. All studies evaluated return of motor function based on the British Medical Research Council scale for muscle strength. Statistics were calculated using weighted means and the student’s t test with α ≤ 0.05. With β = 20%, power calculations demonstrated a minimum of 25 patients per study arm. RESULTS: Nine studies were included for analysis. A total of 641 patients were analyzed with average age 24.9 ± 5.4 years and 93% male population. The average time to surgery was 4.0 ± 1.5 months with average follow up of 41.3 ± 3.7 months. One study reported a single intercostal transfer resulting in restoration of M3 strength elbow flexion. Eight studies reported transfer of 2 intercostals in 414 patients with 76.6% of patients achieving ≥M3 flexion. Six studies reported transfer of 3 intercostals in 218 patients with 62.4% of patients achieving ≥M3 flexion. Finally, 6 (87.5%) of the 8 patients who underwent 4 intercostal nerve transfers achieved ≥M3 flexion. There was no statistically significant difference in return of ≥M3 function between 2 vs. 3 transfers (p = 0.4), 2 vs. 4 transfers (p = 0.4), and 3 vs. 4 transfers (p = 0.07). When comparing return of M4 vs. M3 function, more patients developed M4 function when transferring 2 intercostal nerves (p = 0.05), but there was no difference when transferring 3 intercostals (p = 0.2). CONCLUSION: Intercostal nerve transfer to the musculocutaneous nerve is an operation largely performed in 25-year-old males around 4 months after brachial plexus injury. No significant difference in return of ≥M3 elbow flexion was demonstrated with increased transfer of intercostal nerves. Based on equivalent outcomes, transfer of 2 intercostal nerves is recommended. DISCLOSURE/FINANCIAL SUPPORT:None of the authors has a financial interest in any of the products, devices, or drugs mentioned in this manuscript. REFERENCES: 1. Merrell GA, Barrie KA, Katz DL, Wolfe SW. Results of nerve transfer techniques for restoration of shoulder and elbow function in the context of a meta-analysis of the English literature. J Hand Surg Am. 2001;26(2):303–14. 2. Nagano A. Intercostal nerve transfer for elbow flexion. Tech Hand Up Extrem Surg. 2001;5(3):136–40. 3. Xiao C, Lao J, Wang T, Zhao X, Liu J, Gu Y. Intercostal nerve transfer to neurotize the musculocutaneous nerve after traumatic brachial plexus avulsion: a comparison of two, three, and four nerve transfers. J Reconstr Microsurg. 2014;30(5):297–304. 4. Coulet B, Boretto JG, Lazerges C, Chammas M. A comparison of intercostal and partial ulnar nerve transfers in restoring elbow flexion following upper brachial plexus injury (C5-C6+/-C7). J Hand Surg Am. 2010;35(8):1297–303. 5. Songcharoen P. Brachial plexus injury in Thailand: a report of 520 cases. Microsurgery. 1995;16(1):35–9
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".