Last month we discussed the empty can test versus the full can test, posterior labrum tears, and infraspinatus atrophy. This month, we will address the following questions:
• What is known about the relatively new radio frequency technique of capsular shrinkage for shoulder instability? • Are acromial spurs sufficiently evaluated on plain film radiography, and are they all in the sagittal plane? • What changes occur in the acromium as a person ages? • Are there any new tests for the glenoid labrum?
Joint Capsule Tightening Using Lasers
A relatively new, experimental, yet ubiquitous procedure used to stabilize loose shoulders is radio frequency capsular shrinkage. A holmium:yttrium-aluminum-garnet (Ho:YAG) laser is used to generate heat energy in the capsule, causing morphologic changes in collagen resulting in shrinkage. This shrinkage, in essence, tightens the joint capsule and theoretically provides more stability. This procedure is used mainly for those patients with loose capsules without significant damage, such as labral detachment or tendon rupture. Although this is a surgical topic, sports chiropractors are often asked about the procedure: what is known about it; safety; and alternatives. Not surprisingly, this new technique has caught on as the newest approach, far ahead of any literature to support its safety and long-term effectiveness. Recently, numerous studies have appeared to attempt to fill the gap. Following are three recent publications.
Hecht P, Hayashi K, Cooley J, et al. The thermal effect of monopolar radio frequency energy on the properties of joint capsule. Am J Sports Med 1998;26(6):808-814.
Although the temperature of the tip of the probe of the laser is usually set at or above 65 degrees C, the tip itself does not touch the tissue directly (that would be electrocautery). Questions have arisen regarding the effect of power settings, the cooling effect of the lavage that occurs during this arthroscopic procedure, and the depth of tissue affected by the procedure. This study evaluated the effects at five different power settings. The cross-sectional area, depth, vascularity and inflammation were all increased with increased power settings. Fusion and hyalinization of collagen are the main effects that account for the shrinkage. Seven days post-laser treatment, a regenerative process is evident. Another important finding was that the probe tip temperature is not the same as the tissue temperature. Irrigation has a significant cooling effect on the probe tip, which then remains cooler than the tissue being heated.
Hayashi K, Massa K, Thabit G III, et al. Histologic evaluation of the glenohumeral joint capsule after the laser-assisted capsular shift procedure for glenohumeral instability. Am J Sports Med 1999;27(2):162-167.
This study evaluated the histologic status of the joint capsule before, immediately after and 7-38 months after the procedure. There were no significant histologic lesions prior to surgery in any of the patients. At the time of the laser procedure, there was significant hyalinization of collagen or necrosis of cells. Three to six months after, there was fibrous connective tissue with reactive cells and vasculature increase. The collagen and cell morphology returned to normal 5-38 months after the procedure. Several patients had stiffness following the procedure. They were found to have a persistent synovial, cellular and vascular reaction even one year following the procedure. Interestingly, these patients seemed to respond to "therapeutic manipulation" (not described).
Selecky M, Bangsness T, Liao WL, et al. The effects of laser-induced collagen shortening on the biomechanical properties of the inferior glenohumeral ligament complex. Am J Sports Med 1999;27(2):168-172.
One of the concerns with this new procedure is the long-term effects on the tissue that is treated. Is the tissue as strong, or will it fail earlier than untreated capsule? This cadaveric study attempts to answer that question. There are obvious limitations to extrapolating to live patients. All tissue was pre-tensed, then half of the specimens were shortened by 10% using a laser. Both groups were again tensioned to 10% strain and subsequently loaded to failure.
Interestingly, the laser-treated tissue did not fail earlier. The areas that were laser treated did not fail earlier than surrounding tissue that was not treated. More importantly, the lased specimens seemed to be able to sustain a greater amount of stretch before failure. This may have implications for how early someone may begin a postoperative treatment program. In other words, this tissue was strained immediately after laser treatment and still maintained integrity equal to that of normal tissue; therefore, it would appear that rehabilitation could begin almost immediately keeping in mind that healing is taking place for months after the procedure.
Acromial Shape
Neer1 had proposed that impingement of the rotator cuff was due to a mechanical effect of rubbing at the anterior third of the acromion, coracoacromial ligament and acromioclavicular (AC) joint osteophytes. Bigliani et al.2 described three types of acromions: type I (flat), type II (curved) and type III (hooked). These were viewed off of an outlet view radiograph. It was proposed that rotator cuff tears were more common with the curved and particularly the hooked types.
MacGillivray J, Fealy S, Potter HG, O'Brien SJ. Multiplanar analysis of acromion morphology. Am J Sports Med 1998;26(6):836-840.
This study evaluated acromions using three-dimensional MRI images. They were attempting to see if there was a relationship to shape and age; whether there was sloping in the coronal as well as sagittal plane; and whether there was medial/inferior encroachment at the AC joint not visible on the standard outlet view. The age range was 14-86. They found that most younger patients had a flat acromion. There was a clear increase to a more hooked acromion with age. In addition, the hooking was more downward (as opposed to straight or neutral osteophyte formation). There was a significant percentage of patients with lateral downward angulation (remember the Bigliani curved/hooked acromions were anterior) and medial (inferior) osteophyte formation at the AC joint area who also had signs of impingement. These patients would likely be missed on routine radiography.
Glenoid Labrum Tests
There are numerous new tests for the glenoid labrum. The prototype test was the clunk test, followed by the crank test, the anterior slide test and the O'Brien sign. These have all been discussed in earlier columns.
The principle of each tests varies. Strategies include applying direct compression through the humerus to elicit pain or clunking, or to position for pain or relief. Also, some tests are more specific and sensitive for superior labrum tears, often referred to as SLAP lesions.
Mimori K, Menta T, Nakagawa T, Shinomiya K. A new pain provocation test for superior labral tears of the shoulder. Am J Sports Med 1999;27(2):137-142.
Using a sample of patients with and without superior labrum tears (confirmed with MRI, arthroscopy or arthrograms), the authors studied the response of patients to a provocation and relief position. The examiner lifted the shoulder to between 90 to 100 degrees of abduction and externally rotated the shoulder (similar to the apprehension position). This position would be acquired with the forearm pronated and then repeated with the forearm supinated. Patients were asked which position produced the most pain. The authors considered a positive response when pain was provoked only when the arm was in the pronated position or when pain was more severe in the pronated position compared to the supinated position. The results indicated 100% sensitivity, specificity of 90% and accuracy of 97%. They also tested the crank test and found it to be 83% sensitive; specificity was 100% and accuracy was 87%. Combining the tests would likely reveal most significant superior labral tears. The authors caution that the test probably is not sensitive for fraying of the labrum or for type I SLAP lesions.
References
- Neer CS II. Anterior acromioplasty for the chronic impingement syndrome in the shoulder: a preliminary report. J Bone J Surg 1972;54A:41-50.
- Bigliani LU, Morrison DS, April EW. The morphology of the acromion and its relationship to rotator cuff tears. Orthop Trans 1986;10:228.
Thomas Souza
