News

Research Zeroes in on Pathogenesis of Rotator Cuff Disease

By: Jennie McKee

Findings suggest benefits of early surgery in younger patients with painful tears

Jennie McKee

Understanding the natural history of rotator cuff disease is fundamental for developing appropriate surgical indications,” asserted Ken Yamaguchi, MD, MBA, recipient of the 2014 Ann Doner Vaughan Kappa Delta Award.

Ken Yamaguchi, MD, MBA

For more than 10 years, Dr. Yamaguchi, of Washington University School of Medicine, and his colleagues conducted a longitudinal, prospective follow-up study of a large cohort of patients with asymptomatic rotator cuff tears to learn about the natural history of the disease. Among their findings, noted Dr. Yamaguchi, is that early surgery may be a better option for younger patients with painful tears, but may not be as reliable for older patients due to healing concerns.

“Given the lessons learned from our studies on rotator cuff disease, we now have much clearer and more consistent surgical indications that have led to our institutional healing rates improving from 50 percent to 90 percent of patients,” noted Dr. Yamaguchi.

A dearth of data
Although significant data exist regarding surgical care of rotator cuff tears, much less is known about the natural history of the disease, given that its pathogenesis is often interrupted by surgical treatment. As a result, stated Dr. Yamaguchi, surgical indications for rotator cuff tears vary widely in the United States.

“In considering surgical indications, natural history information is particularly important because it will help determine the risk of degenerative changes occurring to the rotator cuff in the absence of treatment intervention,” said Dr. Yamaguchi. “In other words, this information is important to ascertain the risk of nonsurgical care.”

Dr. Yamaguchi outlined the following concerns related to the degenerative changes that may occur as rotator cuff disease progresses:

  • Tears in patients who are treated conservatively may deteriorate over time, as evidenced by fatty degeneration of the muscle, tear enlargement, superior migration of the humeral head, and/or accumulation of arthritic changes to cartilage.
  • When degenerative changes reach a certain stage, they are irreversible.
  • If not treated surgically in a timely fashion, many degenerative changes have been linked with poorer clinical outcomes and greater likelihood of incomplete healing.

To address these issues, Dr. Yamaguchi and his fellow researchers sought to assess the natural history of untreated rotator cuff disease to formulate more consistent treatment indications.

Identifying a clinical cohort
The large cohort Dr. Yamaguchi and his colleagues studied was identified inadvertently after his institution adopted ultrasound as a primary imaging modality for diagnosing rotator cuff disorders.

“Because ultrasound for the shoulder was initially a new imaging modality, bilateral exams were performed as a matter of protocol for all patients,” asserted Dr. Yamaguchi. “The reasoning at the time was to image the asymptomatic shoulder for comparison purposes to the symptomatic shoulder.” As a result, a large population of patients with asymptomatic, full-thickness rotator cuff tears was identified.

The researchers first conducted a retrospective pilot study with these asymptomatic patients, and then designed a protocol for a large prospective cohort to be studied going forward.

Over the course of the research, 312 patients—262 with either full or partial-thickness tears and 50 control patients without tears—were studied as part of prospective, longitudinal evaluation for between 3 years and 13 years.

At the time of enrollment, all of the patients were completely asymptomatic and had not received any treatment.

According to Dr. Yamaguchi, because these patients had a contralateral symptomatic rotator cuff tear, it was quite likely that the asymptomatic side would become symptomatic while under observation.

“Thus, longitudinal analysis of this population allowed real-time, prospective assessment of what factors may be associated with the development of pain,” he said. “Additionally, it allowed long-term evaluation of the risk for tear enlargement in the absence of treatment intervention.”

Assessing the study participants
The patient cohort underwent yearly, standardized physical examinations, completed outcome questionnaires, and also underwent radiographs and ultrasounds.

Because one possible factor in the development of symptoms could be an alteration in the normal glenohumeral kinematics following the loss of rotator cuff function, the researchers also measured scapular plane kinematics to observe for superior head migration.

Using this data, the investigators then performed studies that focused on the following areas:

  • Glenohumeral kinematics
  • Patient demographics
  • Factors important in the development of pain
  • Patterns of cuff tear enlargement and fatty degeneration
  • Risk of fatty degeneration
  • Risk of rotator cuff tear size progression
  • Risk of unhealed tear after repair

Drawing conclusions
Based on these studies, Dr. Yamaguchi and his colleagues arrived at many conclusions regarding the natural history of rotator cuff tears.

Firstly, they concluded that rotator cuff disease develops in an age-related, bilateral, degenerative way, noting that approximately 40 percent of rotator cuff tears increase in size over as few as three years (Figure 1). Thus, the studies suggested that the tendon undergoes an intrinsic, degenerative process, rather than the more traditionally accepted belief that tears develop due to mechanical impingement.

Fig. 1 Image A shows a 50-year-old patient with a small symptomatic tear that would be treatable with surgery. The tendon edge (wide arrow) is well-defined, and the muscle belly (narrow arrow) is healthy. Ten years later, the tear could deteriorate as shown in image B, which shows a large, massive tear in a 60-year-old patient. The tendon edge is no longer present (wide arrow). Because of issues such as severe muscle atrophy (narrow arrow), it would be difficult if not impossible to achieve a positive outcome with surgery.
Courtesy of Ken Yamaguchi, MD

Additionally, Dr. Yamaguchi’s research found that a proximal humeral migration was much more likely to occur once the tear reached a specific threshold. He and his colleagues came to this conclusion after completing a large, nested case-controlled study involving 89 asymptomatic shoulders and 62 symptomatic shoulders from the original prospective study.

“Those tears wider than 1.5 cm at the humeral insertion had superior migration,” said Dr. Yamaguchi. “From an anatomic standpoint, tears that extended to the bicipital groove and through the anterior supraspinatus tendon were more likely to have altered kinematics.

“As altered glenohumeral kinematics are considered irreversible, the findings suggest a role for early surgical intervention to prevent abnormal glenohumeral kinematics in some at-risk populations,” he continued.

Another important focus is the location of tears. This research suggests that tears initiate more posterior than is commonly thought—at about 1.5 cm posterior to the biceps tendon—and then propagate in both posterior and anterior directions.

“This is important because our findings show loss of the anterior supraspinatus is correlated with the development of fatty degeneration,” said Dr. Yamaguchi. “Coupled with healing concerns we have demonstrated for surgery in older patients, the natural history information suggests that early surgery should be considered more frequently in younger patients with painful tears.”

Additional conclusions drawn from these data regarding treatment indications are the following:

  • Significant risks are associated with nonsurgical treatment in specific patient populations, such as those younger than 60 years with small or medium-sized tears. According to Dr. Yamaguchi, these tears are likely to increase in size in the future. “Thus,” he says, “younger patients with small or medium-sized tears that are significantly painful should be given strong consideration for early surgical intervention prior to the development of chronic changes, such as tear enlargement and fatty degeneration.
  • Nonsurgical treatment may be a better option for older patients because rotator cuff repair is much less likely to lead to tendon healing in patients who are 63 years and older. Thus, early surgical intervention does not provide much clinical advantage in these patients.
  • Biologic factors such as age and size of tear play a bigger role in the pathogenesis of rotator cuff disease than do mechanical factors. A patient’s age should be strongly considered when making treatment decisions.

Dr. Yamaguchi credited the lessons learned from this series of studies with helping his institution to improve its healing rate of patients with rotator cuff tears from 50 percent to 90 percent. In a study conducted primarily by coauthor Jay Keener, MD, consisting of 70 patients age 63 years and younger who had a tear size of 25 mm or smaller, the healing rate exceeded 90 percent.

“It is anticipated that more uniform, accepted criteria for surgical indications will have a significant effect on improving the reliability of good patient outcomes from rotator cuff treatment,” he said.

Dr. Yamaguchi’s coauthors are Dr. Keener; Sharlene Teefey, MD; and Leesa Galatz, MD.

Details of the authors’ disclosure as submitted to the Orthopaedic Disclosure Program can be found in the Final Program; the most current disclosure information may be accessed electronically at www.aaos.org/disclosure

Advertisements


Advertisement