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Published on: December 19, 2019
"Popeye muscle" morphology in OBPI elbow flexion contracture
Christopher J Coroneos1, Zeev V Maizlin2, Carol DeMatteo3
1a 1 Division of Plastic Surgery, Department of Surgery.
Insights
Elbow flexion contracture in obstetrical brachial plexus injury causes distinct biceps morphology. The injured arm shows a shorter muscle belly and overall length, but a longer tendon, consistent with impaired limb growth.
Area of Science:
- Pediatric Orthopedics
- Neuroscience
- Developmental Biology
Background:
- Elbow flexion contracture (EFC) pathophysiology in obstetrical brachial plexus injury (OBPI) is unclear.
- Neonatal denervation models show impaired muscle growth, clinically correlated with denervation extent.
- EFC presents with a clinically short, round biceps, termed the "Popeye muscle".
Purpose of the Study:
- To investigate differences in biceps morphology (muscle belly and tendon length) in arms with EFC secondary to OBPI compared to the contralateral arm.
Main Methods:
- Retrospective matched-cohort study of patients with unilateral EFC (>20°) secondary to OBPI.
- Computed tomography (CT) used by a blinded radiologist to measure biceps short head muscle belly and tendon length bilaterally.
- Standardized anatomical landmarks used for measurements.
Main Results:
- Twelve patients analyzed; all showed shorter biceps muscle bellies in the injured arm (mean difference = 3.6 cm, 80% shorter, p < 0.001).
- Biceps tendons were longer in the injured arm (mean difference = 1.13 cm, 127% longer, p < 0.001).
- Total biceps length was shorter in the injured arm (mean difference = 2.5 cm, 89% shorter, p < 0.001).
Conclusions:
- First human study confirming growth discrepancy in an elbow flexor in EFC secondary to OBPI.
- Demonstrates distinct biceps morphology: significantly shorter muscle belly and overall length, with a longer tendon.
- Findings support impaired limb growth in denervation, explaining the "Popeye muscle" appearance.
Background:
The pathophysiology of elbow flexion contracture (EFC) in obstetrical brachial plexus injury (OBPI) is not established. In basic science models, neonatal denervation leads to impaired muscle growth. In clinical studies, diminished growth is correlated with extent of denervation, and improved with surgical repair. In EFC, the biceps are clinically short and round vs the contralateral size, termed the "Popeye muscle". The objective of this study was to determine if the biceps morphology (muscle belly and tendon length) in arms with EFC secondary to OBPI is different vs the contralateral.
Methods:
This is a retrospective matched-cohort study. Patients with unilateral EFC (>20°) secondary to OBPI were identified (median = 6.6 years, range = 4.7-16.8). A blinded radiologist used computed tomography to measure length of the biceps short head muscle belly, and tendon bilaterally using standardised anatomical landmarks.
Results:
Twelve patients were analyzed. The biceps muscle belly in the injured arm was shorter in all patients vs contralateral, mean difference = 3.6 cm (80%), p < 0.001. The biceps tendon in the injured arm was longer in all patients vs contralateral, mean difference = 1.13 cm (127%), p < 0.001. The total biceps length in the injured arm was shorter in all patients vs contralateral, mean difference = 2.5 cm (89%), p < 0.001.
Conclusions:
This is the first human study confirming growth discrepancy of an elbow flexor in EFC. Distinct biceps morphology is demonstrated, with a significantly shorter muscle belly and overall length, but longer tendon vs normal. This is termed the "Popeye muscle" for its irregular morphology. Findings are consistent with impaired limb growth in denervation.
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