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Phillip N. Williams, MD

AAOS Now

Published 8/1/2017
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Mark Crawford

Understanding Shoulder Kinematics in Patients with Asymptomatic RCTs

OREF grant recipient aims to improve early detection and rehabilitation

Rotator cuff tears (RCTs) occur in more than 50 percent of people older than 60 years of age. Symptomatic RCTs typically often require surgery; however, associated risks include infection, foreign body reaction, and neurologic injury.

"Symptomatic RCTs can be a disabling condition with few treatment options other than surgery, said Phillip N. Williams, MD, assistant professor in the department of orthopaedics at University of Texas Health Science Center at Houston. "Rehabilitation of these pathologic shoulders can also be challenging."

Recent studies have shown that abnormal scapular motion develops in people with asymptomatic pathologic shoulders, compared to people with healthy shoulders, but these differences are not well understood.

"We'd like to learn if patients with asymptomatic RCTs have different scapular motions than individuals with healthy shoulders," said Dr. Williams. "Understanding these differences could lead to improved rehabilitation protocols that use scapular adaptation. We want to limit the necessity of surgical repair yet still provide individuals with a well-functioning shoulder."

As an orthopaedic surgery resident at Hospital for Special Surgery in New York City, Dr. Williams received an Orthopaedic Research and Education Foundation (OREF) Resident Clinician Scientist Training Grant to investigate the role of scapular motion in asymptomatic RCTs. He hoped to determine how individuals with asymptomatic RCTs cope with their pathologic shoulders by changing their scapular kinematics.

Shoulders in motion
Using opto-electric 3-D motion analysis, Dr. Williams and his research team compared scapular kinematics—scaption (or scapular plane elevation), forward flexion, and abduction—between individuals with asymptomatic RCTs and age-matched healthy controls.

Forty asymptomatic, pain-free adults aged 63 years or older with no history of shoulder pathology participated in the study. Dr. Williams and his research team recorded 3-D kinematic data—glenohumeral, scapulothoracic, and humerothoracic—for the following standard shoulder movements performed by the participants with their dominant shoulder: full humeral elevation (0 degrees to 180 degrees) in frontal (abduction), scapular (scaption), and sagittal (forward flexion) planes.

The researchers calculated the scapular slope (humeral motion vs. scapular motion) for ascending and descending directions for shoulder abduction, forward flexion, and scaption. They confirmed rotator cuff (RC) integrity or the presence of any pathology with ultrasound.

Phillip N. Williams, MD
Andreas Kontaxis, PhD, (right), a shoulder biomechanist who worked with Dr. Williams on this research, leads a subject through shoulder range of motion as cameras record her movements via surface markers attached to her upper body.
Courtesy of Phillip N. Williams, MD

"Our working hypothesis was that humerus-to-scapula and scapula-to-trunk kinematics would be different between individuals with asymptomatic rotator cuff tears and healthy controls for scaption, forward flexion, and abduction," said Dr. Williams. "Our hope is that if there is a difference in scapular kinematics between individuals with asymptomatic RCTs and healthy controls, then we can develop a tool for early diagnosis based upon function. Subtle differences between individuals with asymptomatic RCTs and healthy controls could also be used to develop rehabilitation protocols, and possibly surgical solutions, to prevent progression to symptomatic and arthritic shoulder states."

Better shoulder therapies
The researchers found rotator cuff pathology in 31 of the 40 study participants; 7 had RCTs and 24 showed varying degrees of tendinosis. Scapular range of motion was similar between participants without RC pathology and those with asymptomatic RC pathology in shoulder abduction, forward flexion, and scaption. The researchers also found no significant differences in ascending or descending scapular slope for shoulder abduction and scaption, regardless of RC condition.

However, the researchers did find a statistically significant difference between ascending and descending scapular slope in forward flexion (P = 0.021) in participants without RC pathology, compared to those with shoulder pathology. According to Dr. Williams, the difference may be the result of a mechanism that the participants with pathologic shoulder conditions developed to cope with the pain and warrants further study.

He hopes that future comparisons to symptomatic RCT patients will reveal key differences in shoulder kinematics, which can then be used to develop new rehabilitation approaches.

"We are interested in the kinematics of the asymptomatic group because they are copers who have been able to tolerate an RCT," Dr. Williams said.  "Learning these differences in kinematics could help us develop therapy that mimics the scapular kinematics of someone with an asymptomatic RCT. The idea is for the new therapy to help the symptomatic patient cope with a tear."

New tools for success
Ultimately, Dr. Williams hopes the results from this project will lead to noninvasive treatments to lessen the burden of RCTs. In addition, this work will give sports medicine physicians and physical therapists new tools for treating patients with RCTs both nonsurgically and postoperatively.

"OREF funding was instrumental in getting my research off the ground, and I think the grant gave me an audience of orthopaedic surgeons who were interested in my analysis and input," said Dr. Williams. "The grant gave me networking opportunities I didn't know were possible. It was a stepping stone, and I can already see my career progressing in a way that was unimaginable before I received the grant."

Mark Crawford is a contributing writer for OREF. He can be reached at communications@oref.org

© Orthopaedic Research and Education Foundation (OREF)