The Impact of Trunk Deformity on Shoulder Mechanics and Implications for Upper Extremity Function after Corrective Spinal Surgery in Idiopathic Scoliosis
Date
2017
Authors
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Journal ISSN
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Publisher
University of Delaware
Abstract
Adolescent idiopathic scoliosis (AIS) is the most common orthopedic disorder
affecting individuals between the ages of 11 and 18. The disease produces a structural
deformity of the spine and patients often report difficulty performing some activities
of daily living along with pain in the upper back or scapular region. Despite evidence
that trunk deformity negatively affects shoulder complex mechanics in other
populations, upper extremity function is still poorly understood in the AIS population. ☐ Prior studies indicate diminished function and abnormal scapulothoracic (ST)
mechanics in AIS, however these investigations have been limited to the motion of
humerothoracic (HT) elevation. Scapular kinematics associated with activities of daily
living have not yet been investigated. Additionally, it is unknown whether existing
kinematic abnormalities are resolved once the scoliotic curvature is corrected.
Posterior spinal fusion surgery results in a dramatic improvement of the deformity, but
introduces instrumentation and substantial musculoskeletal trauma to the thoracic
region. Postoperative evaluations of shoulder function have previously been limited to
assessment of HT motion, and thus it is unknown whether the treatment has beneficial
or detrimental effects on ST kinematics. ☐ The purpose of this study was to expand current understanding of how the
scoliotic deformity impacts shoulder complex mechanics. This study analyzed ST
kinematics and patient-reported shoulder function in AIS and compared results to a
typically developing cohort. We also analyzed how surgical correction of the spinal
curvature impacts shoulder function, and how postoperative patients with AIS
compare to their typically developing peers. Finally, we investigated how curve
severity interacts with shoulder function and how the degree of curve correction
influences postoperative changes in ST kinematics. ☐ Our results confirmed previous findings of reduced patient-reported function
and lower resting upward rotation and posterior tilt of the scapula on the convex side
of the curvature. We also determined that these kinematic abnormalities persisted
across a range of positions encompassing motion involved in activities of daily living.
While the adolescents in our study did not exhibit any deficits in HT range of motion,
reduced upward rotation and posterior tilt are associated with shoulder pathology, and
patients with AIS may be at risk for future shoulder dysfunction. ☐ The comparison of ST mechanics before and after posterior spinal fusion
revealed that all patients experienced some significant change in kinematics.
Following surgery, scapular resting orientations normalized, but patients with AIS still
displayed abnormal ranges of motion when compared to their typically developing
peers. The scapulae on the concave shoulders demonstrated excessive range of motion,
while the convex scapulae demonstrated diminished range of motion, particularly in
positions involving humeral elevation. These results indicate that, while posterior
spinal fusion is associated with significant changes in shoulder mechanics, these
changes do not necessarily result in normal shoulder function. ☐ Finally, we determined that curve severity appeared to influence preoperative
ST mechanics, however postoperative ST kinematics were much more associated with
preoperative levels of function than with curve parameters. These findings have
substantial clinical impact for understanding of upper extremity function in AIS.
Curve progression may exacerbate existing shoulder complex abnormalities, and may
warrant an evaluation of ST mechanics along with the normal course of treatment in
AIS. For adolescents considering posterior spinal fusion surgery, a preoperative
shoulder complex rehab protocol may contribute to improved postoperative upper
extremity outcomes. Ultimately, the results of this study encourage consideration of
upper extremity factors in the treatment of AIS.
Description
Keywords
Biological sciences, Kinematics, Posterior spinal fusion, Scapula, Scoliosis, Shoulder