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Multiplanar humeral shape changes from infancy to adulthood in patients with birth-related brachial plexus palsy: a
Euan A Forrest1, Paige M Lind2, Michael L Pearl3
1The Department of Rehabilitation Medicine, NIH, Bethesda, MD, USA; Harvard Medical School, Boston, MA, USA.
Insights
Birth-related brachial plexus palsy (BRBPP) causes progressive humeral shape changes and growth inhibition from infancy to adulthood. Early intervention for BRBPP is recommended to limit long-term physical deficits.
Area of Science:
- Orthopedics
- Pediatric Medicine
- Medical Imaging
Background:
- Birth-related brachial plexus palsy (BRBPP) affects up to 1.7% of newborns, potentially impacting long-term quality of life.
- Humeral shape changes in children with BRBPP correlate with functional outcomes.
- Understanding the temporal progression of humeral morphology in BRBPP is crucial for clinical intervention.
Purpose of the Study:
- To evaluate the temporal patterns of humeral shape pathology in unilateral BRBPP.
- To analyze humeral shape changes from infancy through adulthood.
- To establish a basis for improved clinical interventions in BRBPP.
Main Methods:
- 3D MRI scans of both arms were acquired from individuals with unilateral BRBPP (n=32, age 0.6-18.8 years).
- Humeral head version, inclination, and size were quantified using 3D models segmented from MR images.
- The study design was a Level IV Prognosis Case Series.
Main Results:
- Significant bone growth inhibition was observed on the involved side (humeral length, epicondylar width, head diameter), worsening with age.
- The involved humeral head demonstrated anteversion, which increased with age.
- Humeral head declination appeared in older participants (9+ years), also correlating with age.
Conclusions:
- Humeral morphological pathology in BRBPP progresses throughout development.
- Weakened muscle forces and imbalanced movements likely drive these bone changes, creating a pathological feedback loop.
- Earlier intervention for BRBPP may limit physical deficits, while later intervention could prevent worsening pathology.
Background:
Birth-related brachial plexus palsy (BRBPP), occurring in up to 1.7% of live births, may have drastic effects on quality of life for those failing to recover shortly after birth. Because humeral shape changes correlate with function in older children with BRBPP, the purpose of this study is to evaluate the temporal patterns of humeral shape pathology resulting from unilateral BRBPP spanning the arc from infancy to adulthood, strengthening our knowledge as a basis for clinical intervention.
Methods:
Three-dimensional (3D) axial magnetic resonance (MR) images of both arms were acquired from individuals with unilateral BRBPP (20 females and 12 males, age 0.6-18.8 years, 11 left and 21 right involvement). Humeral head version and inclination along with humeral size were quantified from 3D models, manually segmented from the MR images.
Results:
Bone growth inhibition on the involved side was observed (Δ humeral length = -11.2 ± 9.2 mm, Δ epicondylar width = -3.8 ± 4.4 mm, Δ head diameter = -1.8 ± 1.0 mm, P < .001) and increased with age (ρ = -0.65 to -0.73, P < .001). The involved humeral head was anteverted (Δ = -11.1 ± 16.8°, P < .001), which correlated with age (r = -0.59, P < .001). The nerve injury fosters humeral growth inhibition within 6 months of birth. Version was variable across patients in the 6- to 24-month range and then anteversion was typically present in all patients older than 2 years. Humeral head declination was only present in the older participants (≥9 years) and correlated with age (r = -0.42, P = .002).
Conclusion:
This study confirms the presence of increasing humeral morphologic pathology throughout development in children with BRBPP. Morphologic changes are likely caused by weakened/imbalanced muscle forces, which decrease coordinated movements and forces on the bone. The latter leads to size and shape changes that further enhances joint torque weaknesses and imbalances, creating a pathologic feedback loop that eventually hinders functional movement. Increasing pathology with age suggests that earlier intervention is more likely to limit physical and functional deficits associated with BRBPP, but that later intervention may still prevent worsening pathology. In the future, considering humeral morphology as a clinical endpoint when evaluating BRBPP interventions may bring new insight to long-term therapeutic results.
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