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The Efficacy Of Quadrangular Space Decompression For Incomplete Isolated And Brachial Plexus-associated Axillary Nerve Palsy
Austin Y. Ha, MD1, Warangkana Fongsri, MD1, Brendan M. Patterson, MD2, Susan E. Mackinnon, MD1.
1Washington University, St. Louis, MO, USA, 2University of Iowa, Iowa City, IA, USA.

Purpose: Axillary nerve palsy is a debilitating condition that results in the loss of deltoid function and shoulder instability. Direct repair, nerve grafting, and, more recently, nerve transfers have been shown to be effective in restoring shoulder function. In patients with incomplete nerve injuries, decompression of known areas of compression can enhance regeneration. We hypothesized that axillary nerve decompression in the quadrangular space would lead to significant improvement in deltoid function in patients with incomplete isolated and brachial plexus-associated axillary nerve palsy.
Methods: This study was a single-surgeon, retrospective analysis of consecutive patients with incomplete isolated and brachial plexus-associated axillary nerve palsy who underwent quadrangular space decompression by the senior author (SEM) between 2013 and 2018. Incomplete injury was defined as weakness in deltoid function on exam and presence of fibrillations and positive sharp waves on electromyography with active voluntary motor unit potentials in at least one of the three heads of the deltoid. Patients who had complete axillary nerve injuries or who underwent axillary nerve transfers were excluded. The primary outcome variable was the proportion of patients achieving Medical Research Council (MRC) grade 3 shoulder abduction or greater. Secondary outcome variables included shoulder pain, Disabilities of the Arm, Shoulder, and Hand (DASH) scores, presence of deltoid muscle atrophy, and range of shoulder abduction. Baseline and injury-related variables were also collected.
Results: A total of twenty-three patients met the inclusion criteria. Seventeen (73.9%) patients achieved MRC grade 3 shoulder abduction or greater after quadrangular space decompression, compared to only 7 (30.4%) patients preoperatively (p = 0.01) (Table 2). There was a significant decrease in shoulder pain (6, interquartile range [4-8] preoperatively vs. 0.5 [0-2] postoperatively, p = 0.01). The average postoperative DASH scores were 33.9 24.0, compared to 57.4 18.4 preoperatively (p = 0.03). Thirteen (56.5%) patients had evidence of deltoid atrophy preoperatively, compared to 6 (26.1%) postoperatively (p = 0.26). Average preoperative shoulder abduction was 78 [56-135] degrees, compared to 99 [83-128] degrees postoperatively (p = 0.09). Baseline and injury-related variables are summarized in Table 1.
Conclusions: In this retrospective analysis of patients with incomplete isolated and brachial plexus-associated axillary nerve palsy, quadrangular space decompression is associated with improvements in shoulder abduction MRC grade, shoulder pain, and DASH scores.

Table 1: Baseline and Injury-related Variables (n = 23)
Age (years, mean SD)50.2 15.5
Male Sex (n (%))15 (65.2%)
Body Mass Index (mean SD)28.7 6.0
Affected Side Right (n (%))13 (56.5%)
Hand Dominance Right (n (%))22 (95.7%)
Chief Complaint (n (%))
Shoulder Pain
3 (13.0%)
7 (30.4%)
13 (56.5%)
Mechanism of Injury (n (%))
Motor vehicle accident
Parsonage-Turner Syndrome
9 (39.1%)
6 (26.1%)
5 (21.7%)
3 (13.0%)
Diagnosis (n (%))
Isolated Axillary
Brachial Plexus
12 (52.2%)
11 (47.8%)
Injury to Referral (months, mean SD)8.8 7.0
Injury to Surgery (months, mean SD)10.1 7.2
Length of Follow-up (months, mean SD)5.5 2.0
Abbreviations: SD (standard deviation).

Table 2: Outcomes
Shoulder Abduction MRC Grade (n (%))
8 (34.8%)
8 (34.8%)
4 (17.4%)
3 (13.0%)
2 (8.7%)
4 (17.4%)
9 (39.1%)
6 (26.1%)
2 (8.7%)
Shoulder Pain (median [IQR])6 [4-8]0.5 [0-2]0.01
DASH (mean SD)57.4 18.433.9 24.00.03
Deltoid Atrophy Present (n (%))13 (56.5%)6 (26.1%)0.26
Shoulder Abduction (degrees, median [IQR])78 [56-135]99 [83-128]0.09
Abbreviations: MRC (Medical Research Council), IQR (interquartile range), DASH (Disabilities of the arm, shoulder, and hand), SD (standard deviation).

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