Patients had similar postoperative strength, endurance outcomes

Patients experienced no significant differences in postoperative strength and endurance, regardless of whether they had open or arthroscopic anter-ior shoulder stability surgery, according to the results of a study presented during the 2007 annual meeting of the American Orthopaedic Society for Sports Medicine. Researchers also discovered that arm dominance played a crucial role in strength recovery in the shoulder.

“The effectiveness of open versus arthroscopic surgical procedures to stabilize the shoulder for recurrent traumatic anterior instability has largely been measured by the rate of redislocations, with little attention paid to potential strength or endurance differences,” said coauthor Laurie A. Hiemstra, MD, PhD. “I was also surprised that the group that had undergone the open surgical procedure didn’t have an internal rotation strength deficit.”

Isokinetic exercises measured strength, endurance
The 48 individuals in the study were all participants in an existing randomized trial, which had randomized them to receive either open or arthroscopic anterior shoulder stabilization surgery. All patients were at least 12 months postoperative; 24 patients had an open procedure, and 24 patients had an arthroscopic procedure. All patients had followed a standardized rehabilitation protocol.

“Isokinetic concentric and eccentric peak tests were performed at angular velocities of 60 degrees per second and 180 degrees per second for both internal and external rotation of the shoulder. Testing was performed in the most functional position possible in the scapular plane and at 30 degrees of flexion,” explained Dr. Hiemstra. “Patients performed a maximum of three repetitions at each angular velocity with a one-minute rest between velocities. We calculated the average peak moment as the average of the three repetitions.”

When each rotational strength set was completed, patients rested for one minute and then completed an endurance test consisting of 20 repetitions at 180 degrees per second. “Endurance was measured as the relative fatigue ratio—work in first 10 repetitions divided by work in last 10 repetitions,” she continued.

Outcomes showed no differences
Researchers found no statistically significant strength or endurance deficits when they compared the results of the two groups. “The results are even more surprising when you consider the fact that the subscapularis tendon was split in patients who underwent the open procedure, compared to a much smaller cut in the subscapularis in patients who had the arthroscopic procedure,” said Dr. Hiemstra.

In the open group, strength deficits for internal rotation ranged from 2.9 percent to 10.4 percent; external rotation deficits ranged from 3 percent to 17 percent. Insufficient rehabilitation was identified as the primary reason for these deficits, rather than a violation of the subscapularis.

Internal and external rotation strength deficits ranged from 6.9 percent to 8.0 percent in the arthroscopic repair group. Here as well, the external rotation deficits were greater than the internal rotation deficits and attributed to insufficient rehabilitation.

Arm dominance crucial in strength recovery

“In this study, we found that arm dominance is important in strength recovery after the surgical stabilization,” stated Dr. Hiemstra. “In the regression analysis, we found that patients who had their nondominant arm operated on had bigger deficits. We have several theories about those results, but will need to explore this issue in greater depth in another study.”

The researchers believe that the strength deficit between the dominant and nondominant arms may be due to the initial strength difference between the two arms.

“If I had a strength deficit in my dominant arm after surgery, my dominant arm would be comparable in strength to my nondominant arm. Any strength deficits in my nondominant arm would, of course, be quite noticeable. Because people use their dominant arm more frequently, it would follow that they would rehabilitate their dominant arm more diligently than the arm that they don’t rely on as much,” theorized Dr. Hiemstra, who believes that arm dominance is an important issue that needs to be explored in future studies.

Other members of the research team were Treny Sasyniuk, MSc; Nicholas G.H. Mohtadi, MD, MSc; and Gordon H. Fick, PhD.

Annie Hayashi is the senior science writer for AAOS Now. She can be reached at hayashi@aaos.org.