Carlos A. Guanche
The natural history of partial-thickness rotator cuff tears is poorly understood. To begin with, two types of tears need to be considered. Specifically, there are bursal surface tears, whose history and treatment is relatively well-known and straightforward. The second type is an articular side tear, whose history, diagnosis, and treatment are not as clear-cut. It has only been since the advent of shoulder arthroscopy and increasing diagnostic abilities with MRI that we have been able to make the diagnosis. The few series available with respect to the treatment of this problem are sometimes contradictory. The largest issue is that the natural history of partial cuff tears is relatively unknown. Furthermore, as with many shoulder injuries, the patient becomes more symptomatic with increasing activity levels or demands placed on the injured shoulder. The treatment of this problem is certainly different in a professional baseball pitcher as compared with a middle-aged weekend athlete.
Pathogenesis
Pathophysiology
Human cadaveric studies have found that most partial-thickness tears are on the articular side. When partial-thickness tears are openly explored, significant delamination can be encountered, with the articular surface fibers demonstrating the greatest degree of damage. Most degenerative tears originate on the articular side of the supraspinatus tendon, near the insertion, and appear to be primarily from intrinsic tendinopathy and not secondary to anatomic variations or wear from contiguous structures. This finding may be owing to the poor blood supply of the articular side of the supraspinatus insertion. Codman first observed a hypovascular critical zone just proximal to the insertion of the supraspinatus tendon in 1934. It has subsequently been corroborated that the articular side of the supraspinatus insertion has only sparse vascularity, with almost no vessels; the bursal side, however, was well vascularized. This critical zone of ischemia on the articular side seems to correspond well with the common site of rupture of the tendon. The relative ischemia of this area may be one reason why the cuff is unable to repair itself.
The area of degenerative tendinosis occurs most often in this hypovascular zone. This area corresponds well with the crescent described by Burkhart. Immediately medial to this well-defined area of degeneration one can often see the rotator cable, a consistent thickening in the tendon. Typically, the tissue that makes up the cable and all tissue medial to that point is intrinsically healthy. The loss of this crescentic area is perhaps a normal part of aging, and its presence does not necessarily indicate a repairable lesion. Most patients can still elevate their arm with this defect since stress transmission occurs through the cable. This may explain why a significant percent of all tears of the rotator cuff are asymptomatic.
The supraspinatus, a small and relatively weak muscle, is in a key position and is therefore susceptible to overuse and injury. Given the hypovascularity of the tissues, it is not surprising that most tears originate in this tendon. When eccentric tensile overload occurs at a rate that is greater than the ability of the rotator cuff to repair itself, injury occurs. At some point weakness of the musculotendinous unit results in damage to the tendon and ultimately failure. Direct trauma to the shoulder may initiate the same process. A weak, fatigued, or injured rotator cuff is unable to oppose the superior pull of the deltoid effectively and keep the humeral head centered on the glenoid during elevation
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of the arm. This leads to inappropriate superior migration of the humeral head with active elevation of the arm, functionally narrowing the subacromial space. Continued dysfunction of the rotator cuff and further superior migration of the humeral head cause abutment against the undersurface of the acromion and the coracoacromial ligament, leading to signs of secondary impingement.
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TABLE 38-1 Classification of Partial Rotator Cuff Tears |
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The secondary impingement may lead to reactive and degenerative osseous changes. This process of secondary impingement further damages the already injured and weakened cuff. Subacromial impingement does occur, but in most circumstances it is a secondary phenomenon.
Classification
Several classification schemes are available describing full-thickness rotator tears. Most focus on the size of the tear and offer some prognostic criteria following repair. The classification scheme used for partial-thickness tears is somewhat different in that it takes into account the status of both the articular and bursal sides of the tendon.
The scheme most commonly used is the Southern California Orthopedic Institute (SCOI) classification. The scheme separates tears into articular (A), bursal (B), and complete (C) types. The degree of tendon damage is further separated into degree of tearing on a numerical scale of 0 to 4. The grading begins with 0, which is a normal cuff, and culminates with grade 4 (Table 38-1). When recording a tear, all three areas are represented even if they are normal. For example, an A1/B2/C0 tear would be understood as a partial articular-sided tear with minimal fraying in a localized area with the bursal side having cuff fiber failure and bursal injury, extending <2 cm. Finally, despite the degree of injury on both sides, there is no complete tearing, hence the C0 designation.
In addition to the above classification, the more commonly seen entity has recently been termed a PASTA lesion, which is an acronym for a partial articular supraspinatus tendon avulsion. These are the injuries that will be discussed more thoroughly in this chapter as they are typically more symptomatic than the bursal-side tears, which are more common in sedentary and typically older individuals.
Diagnosis
History
The typical patient with a partial inner-surface tear is one who is relatively active in an overhead sport or a manual laborer. In most cases, the onset is insidious and does not present with much acute symptomatology. In many, the symptoms are initially vague and are more often stamina issues rather than inability to perform at a high level.
It is important to obtain an exhaustive history. Patients are often vague about the time of onset of symptoms and the inciting event. Pain needs to be evaluated for quality, location, and duration of symptoms. Actions that worsen symptoms and interventions that improve them are important variables. The timing of onset of pain (how many tosses and at what velocity before symptoms occur), the point in the throwing cycle at which symptoms are greatest, and past history of treatment and prior shoulder problems should be elicited.
The age of presentation in these patients is typically <45 years of age. In many overhead athletes, the history includes a lack of ability to participate at high levels for prolonged periods of time. A baseball pitcher, for example, would typically state that he is able to throw effectively for a few innings, but then his speed and control will start to decrease considerably more quickly than in the past.
Unlike many patients with classic rotator cuff pathology and subacromial impingement, these patients are unlikely to complain of significant night pain. They typically have no resting pain and are unlikely to need treatment if they do not participate in the offending activity.
Physical Examination
One of the most important aspects of the examination in any patient with shoulder pain is to evaluate both sides for symmetry (or lack thereof) and for scapulothoracic dyskinesia, which can be a subtle finding. Males should be examined with their entire upper body exposed, whereas women should be examined with either a tube top or a gown that allows visualization of both shoulders and scapulae. It is important to examine all of the anatomic areas of the shoulder when diagnosing a partial rotator cuff tear, especially as it relates to the possibility of subtle instability or labral tears. There is a high rate of concomitant labral injuries (especially Superior Labrum, Anterior to Posterior Tear [SLAP]) in patients with partial tears.
The physical examination of a patient with a partial cuff tear can be unimpressive, despite later finding a very significant tear on diagnostic imaging. Typically, the patient has a full passive and active range of motion with the exception perhaps of a limitation in internal rotation in high-level throwers. It is important to assess both shoulders for range of motion, especially at the extremes of internal and external rotation. Most patients do not have any significant scapulothoracic asymmetry.
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Specific tests that may be positive in patients with significant partial tears are weakness with forward flexion, adduction, and internal rotation. This tends to put the leading edge of the supraspinatus on tension and is a sensitive indicator of continuity of this portion. Another test that may be positive is pain with 90 degrees of abduction with resistance. This test may actually reproduce the pain that many throwers experience in their motion. Since the typical complaints are of pain in the posterior aspect of the shoulder in the late cocking and early acceleration phases of throwing, placing the shoulder into 90 degrees of abduction, 15 to 20 degrees of forward flexion, and maximum external rotation will recreate the symptoms. A test is considered positive when it recreates complaints of pain that are well localized in the posterior aspect of the shoulder. This test has high sensitivity for diagnosis of partial-thickness undersurface tears of the rotator cuff or posterior labrum. The traditional supraspinatus examination with the arm forward flexed about 30 degrees and the hand in a neutral position is typically nondiagnostic in these patients.
With respect to areas of tenderness, the classic impingement signs are usually negative. There may be some focal tenderness over the greater tuberosity at the leading edge of the supraspinatus, but that is difficult to elicit in a well-muscled athlete.
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Figure 38-1 Radiograph depicting greater tuberosity sclerosis in a patient with a 75% full-thickness supraspinatus tear. |
Imaging
The standard radiographs that are obtained include a scapular anteroposterior (AP), an outlet view, and an axillary projection. Occasionally, a specific acromioclavicular joint view is also warranted. In most cases, the radiographs are normal. The most frequent positive findings are an area of greater tuberosity sclerosis or perhaps cysts over the area of the tear (Fig. 38-1). These areas usually correspond to the areas of tendon avulsion and indicate the chronicity and repetitive nature of the injury.
An arthrogram of the joint may be considered; however, it is typically not helpful in these partial tears. As with most arthrograms (and ultrasound), the technique is definitely operator dependent and the sensitivity varies depending on the experience of the technician.
The most sensitive and specific examination is an MRI with a gadolinium arthrogram. These lesions are typically not seen on traditional MRI studies performed and as such should be highly suspected in a patient with the proper history and examination findings. Not only does the arthrogram portion improve the visualization of the rotator cuff pathology, but it also helps the evaluation of the labral structures that are frequently injured in these patients.
In addition to the standard MRI views, it is important to consider the inclusion of a series that positions the arm in an abducted and externally rotated position. It is not rare to see what appears to be a small and insignificant tear become a rather large tear with this maneuver (Fig. 38-2).
When a partial articular-sided tear is noted on an MRI, there is usually no significant retraction and, more important, no significant muscle atrophy or fatty infiltration. This is an important consideration, as either of these findings will significantly impact the patient's recovery following a surgical repair.
Treatment
Surgical Indications
Classically, the indications for repair of a partial-thickness tear have included one that is >50% of the full thickness of the involved tendon, with lesser tears requiring only debridement of the frayed tissue. Most studies have indicated that the supraspinatus footprint is between 12 and 16 mm long such that a tear >6 to 8 mm thick is an indication for surgery. The determination of the size of the tendon is difficult to make preoperatively based on MRI findings alone. It is therefore important to discuss this with each patient and make sure that the treatment alternatives are understood. Namely, that in tears that involve <25% of the footprint, a simple debridement and correction of any associated lesions may be all that is required. In addition, the determination of the degree of weakness preoperatively is important. In those patients in whom the clinical examination showed significant weakness and <25% of the tendon appears to be involved at the time of arthroscopy, the decision may be to repair the tear. The concept of individualizing the treatment based on the patient's age, activity level, and desire to return to the prior level is extremely important.
The most difficult part of the surgical decision in these patients is that the natural history of the problem is poorly understood. The typical young, active patient who is a repetitive thrower and is unable to participate at the desired activity level makes the problem easy to manage because any partial tear that makes throwing ineffective following a concerted conservative course of rotator cuff strengthening and pain control should undergo surgical repair. Patients who are more sedentary, or whose activity level is minimally affected, present a diagnostic dilemma, since the natural history of the progression of these partial tears into full-thickness tears
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is not completely known. However, cadaveric studies have shown that most partial-thickness tears are articular sided, and mechanical testing on these partial tears has led to complete disruption in a great percentage of samples. Although the correlation between cadaveric studies and in vivo pathophysiology is not always direct, it is important to consider this point in significant partial tears or in those unresponsive to conservative measures.
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Figure 38-2 A: Coronal MRI (T2) view of a patient with clinical signs consistent with a partial rotator cuff tear. B: MRI (T2) view in abduction and external rotation depicting a near full-thickness tear of the supraspinatus. |
Surgical Contraindications
There are few true contraindications to surgical intervention in a patient who meets the criteria described above. One important consideration is that the patient must have full passive range of motion. There may be some minor limitations in active motion especially at the extremes of internal and external rotation. Any significant limitation, however, should be dealt with preoperatively with passive stretching. A significant limitation that is not resolved with aggressive conservative modalities preoperatively may require a capsular release. This is especially common in throwing athletes in whom the particular motion that is restricted is internal rotation.
Surgical Intervention
Options
The treatment of partial-thickness cuff tears has recently expanded as a result of the use of the arthroscope. With that in mind, most algorithms include the use of the arthroscope to make the diagnosis, especially those tears that are on the articular side. The treatment of outer surface tears can certainly be undertaken without the arthroscope with a traditional open technique, although as previously mentioned, there is a significant likelihood that a concomitant intra-articular surgical lesion exists, most commonly a labral tear. If the surgery is performed in an open fashion, the intra-articular visualization is at the very least compromised.
The recent literature supports the use of arthroscopic techniques that use suture anchors for solid cuff fixation. Two techniques are commonly used. One is the transtendon technique in which the remaining rotator cuff material is left intact and the tear is fixed with suture anchors placed through small incisions in the cuff. The other technique involves completion of the tear followed by arthroscopic repair (identical to what is performed in full thickness tears). The general guidelines for one technique over the other include the use of the transtendon technique in those tears where >75% of the tendon is intact. In tears where a larger portion of the tendon is involved, the tear is completed and a standard arthroscopic repair is performed. These are guidelines only, and the treatment should be based on the individual physician's experience with each technique.
Surgical Technique
The author's preferred technique involves the use of the lateral decubitus position for shoulder arthroscopy with hypotensive anesthesia. The transtendon repair technique is used in most cases, as this preserves a more significant portion of the normal rotator cuff and recreates the original footprint more effectively.
The procedure uses standard viewing portals, and the tear is delineated arthroscopically. The entire visualized cuff should be palpated and delineated for any significant intrasubstance delamination (Fig. 38-3).
This includes debridement of the frayed edges and bony preparation of the footprint (Fig. 38-4). A spinal needle is now inserted from the lateral aspect of the joint into the area of the tear. The needle is then threaded with a large suture that can easily be found in the subacromial space. The subacromial space is then entered and the suture tag is found. A determination of the degree of bursal-sided tearing, if any, is made. If significant bursal tearing is noted, then a decision should be made to complete the tear and treat it in the standard fashion for a full-thickness tear.
If no significant bursal pathology is noted, a complete bursectomy is performed in anticipation of a transtendon repair and consequent suture tying in the subacromial space. If a complete bursectomy is not performed, significant difficulty will be encountered in the final stages of the repair as suture tying becomes very difficult without complete visualization. Once the subacromial space is cleared and any
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osteophytes or coracoacromial pathology is addressed, the glenohumeral joint is then re-entered.
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Figure 38-3 Intrasubstance delamination of a rotator cuff. A: MRI (T1) view of an inner surface delamination. B: Intra-articular visualization of this significant lesion. |
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Figure 38-4 Preparation of the cuff tissue and the footprint of a partial-thickness tear. Right shoulder, posterior portal view. Note the anchor already in place at the anterior edge. |
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Figure 38-5 Suture penetrator being used for grasping a suture directly from the anchor after piercing the rotator cuff tissue. |
The joint is visualized from the posterior portal, and needle localization of the appropriate spot for suture anchor placement is now performed. In general, the traditional rule of thumb of one anchor per centimeter of tearing in the anterior to posterior dimension is followed. The appropriate number of anchors is then placed by making one longitudinal incision in the remaining cuff (parallel to the fibers of the tendon) just large enough to accommodate the suture anchor. In most cases, only one cuff incision is necessary, since the humerus can be rotated to position the anchors appropriately in the tuberosity. As the anchors are placed in the tuberosity, the sutures are pulled out of the anterior portal. All of the sutures are pulled out through this portal prior to beginning suture passing through the cuff.
Following completion of anchor insertion, the sutures are now passed through the tissue. Various suture-passing devices are available for this process, and they include needle-type devices with various curvatures and cannulated centers that allow suture shuttling through the appropriate point in the cuff. In addition, other penetrating devices allow for piercing the cuff tissue directly and grasping the suture (Fig. 38-5).
Anatomic cuff reattachment is the goal. The tendency with the technique is to advance a larger amount of cuff than is necessary, thus effectively overtensioning the cuff and leading to later excessive limitation of motion. It is important to gauge the amount of tissue that is taken with each suture and allow for a comfortable recreation of the footprint without undue tension following knot tying.
Once all of the sutures are passed, the subacromial space is again visualized from posterior and the knots are tied in a methodical fashion from anterior to posterior (Fig. 38-6). The basic principles of knot tying should be followed, namely a sliding locking knot that is backed up with reverse
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half hitches. In addition, only one pair of sutures should be in the portal while tying is taking place at any one time to avoid tangling of sutures.
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Figure 38-6 Sutures passed following anchor insertion (Right shoulder, posterior portal view). A: Intraarticular visualization of the final suture position. B: Subacromial visualization of the final sutures. C: Final intraarticular visualization of the cuff repair. |
Postoperative Rehabilitation
Following the surgical procedure, the patient is immobilized in a sling for 4 weeks with the institution of early elbow and hand range of motion exercises. During the second week, pendulum exercises are begun and gradually increased in range and frequency with a minimum of pain. The maximum forward flexion at this point (until 6 weeks postoperative) is kept to <90 degrees. At 6 weeks, the patient is allowed to begin active elevation and strengthening as tolerated. Typically a throwing program is instituted at 4 months. This is predicated on a complete range of motion and at near-complete (grade 4+/5) strength in all of the rotator cuff muscles and deltoid. Full, unrestricted activities including throwing are allowed at 6 months postoperatively.
Results of Surgical Intervention
In general, the literature indicates that a partial articular-sided tear in an active individual is likely to progress. Furthermore, simple acromioplasty does not predictably return the athlete to any semblance of his or her prior activity. The best results attained with partial-thickness tears have been in those cases where a repair has been performed. Several series delineate the arthroscopic evaluation and debridement of these tears with an acromioplasty. These have uniformly shown a lower rate of return to high-level activities as compared with series of repairs, regardless of the technique chosen. Up to 94% satisfactory results have been reported with arthroscopic decompression and mini-open rotator cuff repair.
In bursal-sided tears, however, the scenario is different in that many of these cases have a mechanical cause such as a prominent anterior acromion. In those cases, a debridement of the tear and subsequent acromioplasty may be of benefit in many patients. In general, the patients with this injury tend to be older and less active. Although degenerative labral tears are often encountered, these typically do not need any surgical fixation, unlike the patients with articular-side tears.
Suggested Readings
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