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    Dealing with the Ulnar Nerve in Surgical Repair of Distal Humerus Fracture

    A prospective randomized controlled trial from Canada provides insight into postoperative ulnar nerve function when the ulnar nerve is returned to its in situ position in the cubital tunnel after fixation of a distal humerus fracture versus anterior transposition of the ulnar nerve after fracture fixation.

    Authors

    Nina Fisher, MD, and Philipp Leucht, MD, PhD

    Article

    Dehghan N, Nauth A, Hall J, Vicente M, et al. In site placement vs. anterior transposition of the ulnar nerve for distal humerus fractures treated with plate fixation: a multi centre randomized controlled trial. J Orthop Trauma. 2021 Mar 25.

    Summary

    Ulnar nerve injury is a known complication following distal humerus fractures, especially in patients undergoing operative repair. Although the fracture pattern alone can cause injury, the nerve may also be damaged during internal fixation.

    The standard operative treatment for distal humerus fractures involves open reduction and internal fixation using a posterior approach, with the ulnar nerve isolated and mobilized to protect it during fracture reduction and fixation. This may lead to ulnar neuropathy or neuritis due to nerve handling and position after fixation. However, there is no consensus in the literature on whether transposition or in situ placement is more protective against ulnar nerve symptoms. [1]

    In a prospective randomized controlled trial performed at 8 tertiary care centers in Canada, patients presenting with a distal humerus fractures were enrolled and randomized to 1 of 2 groups:

    • Ulnar nerve returned to its in situ position in the cubital tunnel after fracture fixation
    • Anterior transposition of the ulnar nerve after fracture fixation

    Patients ages 16 to 80 were included if they had a displaced intra-articular distal humerus fracture (OTA/AO 13A or 13C) that required bicolumnar plate fixation and were undergoing operative repair within 28 days of injury. Both closed and type I and type II open fractures were included. Patents were excluded if they had a prior history of ulnar neuropathy, elbow pathology, or previous distal humerus fracture or if they had a limited life expectancy. Preoperative ulnar nerve symptoms were not part of the inclusion criteria.

    The researchers hypothesized that there would be no difference in ulnar nerve function between the treatment groups at 1 year postoperatively. The primary outcome measure was the Gabel and Amadio ulnar nerve entrapment scale, which assesses the patient’s pain, sensory, and motor symptoms to determine a qualitative result, with a higher score indicating a better outcome.

    Power analysis determined that having 25 patients in each group would achieve a 91% power to detect a difference of 1 point in the Gabel and Amadio scale. Of the 225 patients identified as potential subjects for the study, a total of 58 were randomized and included in the final analysis, 31 in the in situ group and 27 in the transposition group.

    The researchers found that:

    • Both groups had a similar rate of preoperative numbness, with 1 patient experiencing ulnar nerve motor deficits in the transposition group. This was not statistically significant.
    • There was no significant difference in operative time.
    • Two-point discrimination and functional outcomes scores significantly improved from time of injury to 1 year postoperatively, with no difference between the groups.
    • There was no difference at any time point in the Gabel and Amadio scale, with scores significantly improving in all patients from time of injury to 1 year postoperatively.
    • No significant difference was observed between the groups in nerve conduction studies performed as a secondary outcome measure at 6 weeks, although the transposition group had higher rate of abnormal results, minor and severe abnormalities, and sensory and motor/sensory neuropathies.
    • The overall complication rate was not significantly different between the groups.

    Clinical Relevance

    This study represents the first randomized controlled trial to address whether anterior transposition is useful in operative repair of distal humerus fractures. No significant differences were observed in ulnar nerve symptoms or functional outcomes between patients treated with mobilization and in situ placement of the ulnar nerve and those treated with mobilization and anterior transposition. In addition, although there was a high rate of preoperative and postoperative ulnar nerve symptoms, patients in both treatment groups experienced significant symptom improvement by 1 year postoperatively.

    In patients with distal humerus fracture, preoperative symptoms are likely due to initial trauma and subsequent fracture displacement, leading to swelling near and compression of the ulnar nerve. Performing a thorough preoperative exam is crucial in determining if any deficits are present prior to operative repair. However, based on this study, even patients who have pre- or postoperative deficits should expect significant recovery by 1 year postoperatively.

    There is no consensus in the literature on whether anterior transposition of the ulnar nerve is beneficial in operative fixation of distal humerus fractures. Several small studies showed no postoperative complications following anterior transposition and recommended routine use of transposition. [2,3] Subsequent studies demonstrated that transposition is not protective and can, in fact, result in up to 4 times increased incidence of ulnar neuritis. [4,5] These studies were all retrospective in nature, however. Thus, the study from Canada provides excellent prospective data that can be used in the management of patients with a distal humerus fracture.

    The extent of ulnar nerve release at the time of decompression and mobilization was not standardized or measured, and that is the main limitation to this study. Furthermore, there were multiple treating surgeons, which increased the variability in intraoperative technique but also improved the applicability of the study findings. Although this is a relatively small study, it was appropriately powered, with 90% or higher follow-up at all time points.

    This study suggests that there is no significant difference between in situ placement and transposition of the ulnar nerve in the management of distal humerus fractures. The decision of where to leave the nerve at the end of surgery can remain at the discretion of the treating surgeon, based on their level of comfort and experience, and patients can expect similar functional outcomes with either technique.

    Author Information

    Nina Fisher, MD, is a resident in orthopaedic surgery at NYU Langone Health, New York, New York. Philipp Leucht, MD, PhD, is the Director of Orthopedic Research and an Associate Professor in the Departments of Orthopedic Surgery and Cell Biology at NYU Langone Health, New York, New York.

    Disclosures: The authors have no disclosures relevant to this article.

    References

    1. Stevens NM. Distal humerus fractures: evolution of management. Bull Hosp Joint Dis. 2021;79(1):43-50.
    2. Wang KC, Shih HN, Hsu KY, Shih CH. Intercondylar fractures of the distal humerus: routine anterior subcutaneous transposition of the ulnar nerve in a posterior operative approach. J Trauma. 1994 Jun;36(6):770-3.
    3. Ruan HJ, Liu JJ, Fan CY, Jiang J, Zeng BF. Incidence, management, and prognosis of early ulnar nerve dysfunction in type C fractures of distal humerus. J Trauma – Inj Infect Crit Care. 2009;67(6):1397-1401. doi:10.1097/TA.0b013e3181968176
    4. Vazquez O, Rutgers M, Ring DC, Walsh M, Egol KA. Fate of the ulnar nerve after operative fixation of distal humerus fractures. J Orthop Trauma. 2010;24(7):395-399. doi:10.1097/BOT.0b013e3181e3e273
    5. Chen RC, Harris DJ, Leduc S, Borrelli JJ, Tornetta P, Ricci WM. Is ulnar nerve transposition beneficial during open reduction internal fixation of distal humerus fractures? J Orthop Trauma. 2010;24(7):391-394. doi:10.1097/BOT.0b013e3181c99246