Arthroscopic Treatment of Massive Rotator Cuff Tears

Abstract

In the past 10 years, arthroscopic surgeons have gone from being unable to repair any rotator cuff tears arthroscopically to being able to repair virtually all rotator cuff tears, even complex massive tears, arthroscopically. The factors responsible for this rapid evolution have been: (1) recognition of the mechanical principles responsible for a secure repair (margin convergence, knot security, loop security); (2) recognition of major tear patterns that require different techniques of repair; and (3) development of instrumentation and arthroscopic portals that predictably accomplish secure repair of the rotator cuff and direct access to the pathologic areas. In the current study, the author analyzes each factor, anatomic and mechanical, that influences the quality of the repair, and explains how to optimize the overall repair by optimizing each step in the repair. In the author’s series of arthroscopic repair of rotator cuff tears, the results have been gratifying, with massive tears achieving final results equivalent to those of smaller tears.

During the past decade, there has been a dramatic evolution in the arthroscopic treatment of massive rotator cuff tears. The arthroscopic cuff debridements of the early 1990s have yielded to the sophisticated arthroscopic cuff repairs and reconstructions of today. How have we been able to come so far so fast? After all, in only 10 years we have gone from the stage of being unable to repair any rotator cuff tears arthroscopically to the current status of being able to repair virtually all rotator cuff tears, even massive tears, arthroscopically. As with any breakthrough technology, this rapid progress was made possible by the marriage of insight to technology. The great misconception of our era is that technology alone will advance a discipline; the irony is that technology in a vacuum produces no advancement. Technology without understanding produces mere gadgets; technology guided by insight produces tools.

Historic Perspective

It is instructive to review briefly the past 10 years of arthroscopic treatment of rotator cuff tears to see how certain concepts developed and enhanced arthroscopic techniques. Much of the early arthroscopic rotator cuff literature reported on arthroscopic debridement of massive rotator cuff tears. ^5,6,26–28 In general, a massive rotator cuff tear was defined as one in which the major tear diameter was greater than 5 cm. This definition is the one that the author will use in referring to massive cuff tears. ^23,45

The tears that did well with debridement were those that had balanced force couples in the transverse and coronal planes (Fig 1). Shoulders that had balanced force couples despite large rotator cuff tears generally had good function, although they were painful; therefore, they were called functional rotator cuff tears. ⁷ Early reports of debridement generally were good. ^{6,22,24–26,53} For example, in younger, more active patients, the results of rotator cuff debridement deteriorated with time. ^41,55 As repair techniques developed, cuff debridement gradually fell out of favor for all tears except the small partial-thickness tears.

Fig 1A–B.: (A) Transverse (axial) plane force couple in which the anterior rotator cuff force is balanced against the posterior rotator cuff force. (B) Coronal plane force couple in which the force from the inferior portion of the rotator cuff (posterior and anterior) is balanced against the deltoid force. (Reprinted with permission from the University of Texas Health Science Center at San Antonio.)

The refinement of suture anchor techniques has brought us into the current era of arthroscopic repair of virtually all rotator cuff tears.

Arthroscopic Repair of Massive Rotator Cuff Tears

One of the great advantages of the arthroscope is that it frees the surgeon from spatial constraints. He or she can approach a pathologic area from anterior, posterior, medial, or lateral positions with equal facility. Unlike the arthroscopic surgery open surgery is restricted in its approach by the position of the incision. Therefore, if the surgeon makes an anterolateral incision for cuff repair, he or she must bring the torn edge of the cuff to the incision so that he or she can see to repair it. This medial-to-lateral mindset has dominated open rotator cuff surgery in which the conventional wisdom has been that the cuff always must be mobilized sufficiently medially so that it can be pulled laterally to the humeral neck and greater tuberosity for repair. ^{3,21,22,25,31,33,37,43,44,47} Unfortunately, in the author’s opinion, this medial-to-lateral mindset retarded the progress of rotator cuff repair by delaying the recognition of one of the most useful concepts in the repair of massive rotator cuff tears, margin convergence. ¹²

Margin Convergence for Closure of the U-shaped Tear: The So-Called Retracted Tear

It is critical to recognize that most so-called retracted massive cuff tears are not retracted at all. These large U-shaped tears actually are L-shaped tears with a vertical split from medial to lateral; they have assumed a U-shape by virtue of the elasticity of the involved muscle-tendon units. McLaughlin ⁴⁰ recognized this tear pattern more than 50 years ago and advocated L-shaped repair using a combination of side-to-side tendon-to-tendon sutures and end-on tendon-to-bone sutures. Unfortunately, McLaughlin’s advice was not heeded, and mainstream orthopaedic teaching went the way of medial-to-lateral mobilization regardless of the shape of the tear. The large U-shaped tears that extended medially to the glenoid were incorrectly designated as retracted tears, and ill-advised massive mobilization of these tears guaranteed failure of repair because of tension overload at the apex of the tear.

Although McLaughlin recommended side-to-side repair of the vertical component of the large U-shaped tears as the anatomically correct technique of repair, he did not recognize the incredible mechanical advantage that accrued from side-to-side closure as a direct result of a biomechanical principle that is called margin convergence. ¹² This term refers to the phenomenon that occurs with side-to-side closure of large cuff tears, in which the free margin of the tear converges toward the greater tuberosity as side-to-side repair progresses (Fig 2). As this margin converges, the strain at the free edge of the cuff is reduced dramatically, leaving a virtually tension-free converged cuff margin overlying the humeral bone bed for repair. For example, side-to-side closure of ⅔ of a U-shaped tear will reduce the strain at the cuff margin to ⅙ the strain that existed at the preconverged cuff margin. This mechanical strain reduction creates an added safety factor for the repair to bone because decreased strain means that there will be a lower likelihood of failure of fixation to bone (for either suture anchors or bone tunnels).

Fig 2A–B.: (A) U-shaped rotator cuff tear is shown. (B) Partial side-to-side repair causes a margin convergence of the tear toward the greater tuberosity which increases the cross-sectional area and decreases the length of the tear, thereby decreasing strain. (Reprinted with permission from the University of Texas Health Science Center at San Antonio.)

The First Step: Tear Pattern Recognition

The critical first step in doing an arthroscopic repair of a massive tear is tear pattern recognition. Most rotator cuff tears can be broadly classified into two patterns: crescent-shaped tears and U-shaped tears. In the author’s practice, U-shaped tears comprise approximately 40% of all tears and 85% of the large and massive tears. ^11,18 Crescent-shaped tears, even large and massive tears, typically pull away from bone but do not retract far. Therefore, they can be repaired directly to bone with minimal tension (Fig 3). U-shaped tears generally extend much farther medially than crescent-shaped tears, with the apex of the tear located above the glenoid or even medial to the glenoid (Fig 4). It is important to realize that this medial extension of the tear does not represent retraction, but rather represents the shape that an L-shaped tear assumes under physiologic load from its muscle-tendon components. Closing such a tear is similar to closing a tent flap; one must reconstitute the two limbs of the L (Figs 5, 6). One must not make the mistake of trying to mobilize the medial margin of the U-shaped tear from the glenoid and scapular neck enough to pull it over to the humeral bone bed. The large tensile stresses in the middle of such a repaired cuff margin would doom it to failure.

Fig 3.: Crescent-shaped rotator cuff tear without much retraction can be repaired directly to bone with minimal tension. (Reprinted with permission from the University of Texas Health Science Center at San Antonio.)

Fig 4.: A large U-shaped rotator cuff tear whose apex extends to the glenoid is shown. (Reprinted with permission from the University of Texas Health Science Center at San Antonio.)

Fig 5.: Closing a tent flap provides an accurate analogy to closing a U-shaped rotator cuff tear. (Reprinted with permission from the University of Texas Health Science Center at San Antonio.)

Fig 6A–D.: The repair of an L-shaped tear is shown. (A) L-shaped tear. (B) Elasticity of the musculotendinous units causes deformation of the L-shaped tear to a U-shaped tear. (C) Closure of the vertical limb of the tear by side-to-side sutures. (D) Closure of the horizontal limb of the tear by tendon-to-bone sutures. (Reprinted with permission from the University of Texas Health Science Center at San Antonio.)

Repairing the Crescent-Shaped Tear

Crescent-shaped tears can be easily repaired to bone (Fig 7). It was shown previously that, under conditions of physiologic cyclic loading, bone fixation by suture anchors is stronger than bone fixation by transosseous bone tunnels; therefore suture anchors are the author’s preferred method of fixation. ¹³ The author prepares a bone bed on the humeral neck, just off the articular margin, by means of a power shaver so as not to decorticate the bone. Decortication of bone would weaken anchor fixation, so it should be avoided. A bleeding bone surface rather than a bone trough is all that is necessary for satisfactory healing of tendon to bone. ⁴⁸

Fig 7.: Repair of crescent-shaped rotator cuff tear directly to bone is shown. (Reprinted with permission from the University of Texas Health Science Center at San Antonio.)

The suture anchors should be inserted at an angle of approximately 45° to the bone surface (the Deadman Angle) to increase the anchor’s resistance to pullout. ⁸ The author prefers to use the Corkscrew or Biocorkscrew suture anchor (Arthrex, Naples, FL) but all of today’s permanent and biodegradable suture anchors have adequate pullout strengths to resist physiologic loads. ^1,2

The crescent-shaped margin of the tear must be respected in the repair and therefore the suture anchors should be placed in a crescent array just 4 or 5 mm off the articular surface to avoid tension overload at any of the fixation points (Fig 8). Tension overload has been shown experimentally to cause failure of cuff repairs subjected to physiologic cyclic loads. ^13,15

Fig 8.: The surgeon must respect the crescent-shaped margin of the tear to avoid tension overload. Anchors are placed 4 or 5 mm off the articular surface in a crescent array. (Reprinted with permission from the University of Texas Health Science Center at San Antonio.)

Suture capture of the tendon can be done arthroscopically by either simple sutures or mattress sutures. The strength of simple sutures of Number 2 Ethibond (Ethicon, Somerville, NJ) has been shown in the laboratory to be adequate for maximal physiologic loading conditions of the rotator cuff. ^14,16

Loop security is defined as the ability to maintain a tight suture loop as a knot is tied. Knot security is defined as the effectiveness of a given knot to resist slippage or breakage when load is applied. Little has been written about loop security, but it is at least as important as knot security because a loose loop will allow loss of soft tissue fixation even though its associated knot may be very strong ¹⁷ (Fig 9). It is preferable to tie knots with an arthroscopic double-diameter knot pusher (Surgeon’s Sixth Finger; Arthrex) because of the exceptional loop security, as shown experimentally, that can be achieved with this device. Some complex sliding knots may potentially maintain adequate loop security if they are locked once they are in a set position. However, the loop security of complex sliding knots has not been investigated.

Fig 9A–B.: (A) A tight suture loop keeps the tendon apposed to the prepared bone bed. (B) A loose suture loop allows the tendon to pull away from the bone bed, even though the knot may be tight. (Reprinted with permission from the University of Texas Health Science Center at San Antonio.)

The literature pertaining to knot security is vast and confusing. ^{4,29,30,35,36,38,39,42,46,50,51,52,54} An attempt was made to simplify the issue of knot security by investigating its two extremes ^16,20 : (1) The minimal strength that a knot must possess to avoid failure under maximal physiologic load. That is, what is the weakest knot that will still be strong enough to hold a repair under all conditions?; (2) The maximum strength that can be imparted to a knot, which for any given knot would necessitate converting its failure mode from failure by slippage to failure by breakage.

One must keep in mind that knot security is dependent on three factors: friction, internal interference, and slack between throws. ¹⁶ Friction obviously will be greater for braided multifilament suture than for slick monofilament suture. Internal interference refers to the weave of the two suture limbs relative to each other, and it can be increased by changing posts between throws of the knot or reversing the direction of consecutive half-hitches, or both. Slack between throws is removed effectively by two maneuvers: (1) removing any twists between the two suture limbs before each half-hitch is tightened; and (2) past-pointing (running the knot pusher past the knot while tensioning the two suture limbs) to tighten each half-hitch. Therefore, one can increase knot security by using a braided suture, reversing post suture limbs or loop direction, or both, removing all twists (slack) between suture limbs, and past-pointing to tighten each half-hitch.

To look at the issue of suture failure, it is useful to calculate the maximal theoretical load that might be produced by a sudden forceful contraction of the rotator cuff. It was shown previously that if a 4 cm rotator cuff tear is fixed with three suture anchors loaded with two sutures each and located 1 cm apart, the load per suture during a maximal contraction would be 37.75 N. ¹⁵ The ultimate strength of all combinations of knots formed by four half-hitches was investigated previously ^10,16 (Fig 10) S=S=S=S means that the post is the same for each throw and that each half-hitch is thrown in the same direction (either underhand or overhand). SxSxSxS means that the post is the same for each throw, but each consecutive half-hitch reverses direction (overhand to underhand to overhand to underhand). S//S//S//S means that the post is reversed with each half-hitch, but each consecutive half-hitch is thrown the same way (overhand or underhand). S//xS//xS//xS means that with each half-hitch, the post is reversed and the direction of the throw (overhand or underhand) is reversed. In a biomechanical study, Burkhart et al ¹⁶ examined the ability of these four knot configurations to withstand the above-noted load of 37.75 N that would be generated by a maximal contraction of the rotator cuff. It was found that all except the same-post, same direction configuration (S=S=S=S) will withstand these forces. The other three configurations of stacked half-hitches (SxSxSxS, S//S//S//S, S//xS//xS//xS) failed in the 38 to 50 N range, enough to withstand a maximal contraction but not by a very large margin. ¹⁶ Therefore, these three stacked half-hitch knots can be considered to possess the minimal acceptable strength to failure.

Fig 10A–D.: Half-hitch knot configurations are shown. (A) Same post, same loop knot configuration (S=S=S=S). (B) Same post, reverse loop knot configuration (SxSxSxS). (C) Reverse post, same loop knot configuration (S//S//S//S). (D) Reverse post, reverse loop knot configuration (S//xS//xS//xS). (Reprinted with permission from the University of Texas Health Science Center at San Antonio.)

All the above-mentioned stacked half-hitch configurations failed by slippage. However, failure by breakage rather than slippage would be preferable, because breakage always occurs at higher loads than slippage. Failure by breakage indicates that knot security has been maximized. Therefore, the author wanted to determine what it could take to maximize knot security of standard knots so that they would break rather than slip. In examining this issue, one must first understand that virtually all complex sliding knots (stacked half-hitches, Duncan loop, buntline hitch) fail by slippage. The conventional wisdom is that these base knots can be locked, so that they will not slip, by adding one or two half-hitches on top of the base knot. Chan et al ²⁰ investigated the concept experimentally, and found that the conventional wisdom is wrong. One or two half-hitches will not lock the base knot in most cases. It was found that the minimal configuration that will lock a base knot is three reversed-post half-hitches; that is three half-hitches applied on top of the base knot so that the post is switched on three consecutive throws. The three reversed-post half-hitches always will lock the base knot and convert its mode of failure from slippage to breakage, thereby reliably maximizing knot security; therefore this is the author’s recommended locking configuration, regardless of which base knot is used. ²⁰

Repairing the U-Shaped Tear

Repair of massive U-shaped tears can be gratifying, because many of these tears appear irreparable on first view. However, one or two side-to-side sutures often will achieve such dramatic margin convergence that repair to bone can be simple (Fig 11).

Fig 11.: Repair of U-shaped cuff tears begins with side-to-side sutures that converge the free margin toward the bone bed (margin convergence). After placing side-to-side sutures, the free margin of the cuff is repaired to bone with suture anchors. (Reprinted with permission from the University of Texas Health Science Center at San Antonio.)

In repairing large U-shaped tears, there are two biomechanical principles that must be followed sequentially to produce a functional rotator cuff. These principles are: margin convergence ¹² and balance of force couples. ⁷

The author typically begins side-to-side closure with a combination of Penetrator™ and BirdBeak™ suture passers (Arthrex) that are used to pass permanent braided sutures through the posterior and anterior leaves of the cuff tear, while he views with the scope in a lateral subacromial position. Most of the large and massive tears require three to four side-to-side sutures. These sutures are tied sequentially, the most medial suture first, to achieve margin convergence of the cuff margin over the prepared bone bed. Two Corkscrew (Arthrex) suture anchors then are placed, one for each leaf of the cuff tear. The anchor for the posterior leaf is placed approximately 1 cm anterolateral to the edge of the posterior leaf of the cuff so that the posterior leaf can be shifted proximally and anteriorly. This maneuver maximizes the moment produced by the posterior cuff in the transverse and coronal planes, thereby creating balanced force couples in both planes. The achievement of balanced force couples allows the shoulder to establish a stable fulcrum of glenohumeral motion. Loop security and knot security are vital to maintaining the shift of the posterior rotator cuff to the suture anchors. The anterior leaf typically is not as mobile as the posterior leaf, and a significant shift of the anterior leaf usually is not possible or necessary, so the anterior anchor is placed adjacent to the edge of the anterior leaf. The sutures from the anchor then are passed through the anterior leaf by means of a suture passer through an anterior portal, and the sutures are tied. External rotation of the shoulder often will optimize the angle of approach of the suture passer through the anterior leaf.

Partial Repair

If complete closure of cuff to bone cannot be accomplished even after margin convergence, the force couple still can be effective even though a hole is left in the superior portion of the cuff. Such partial cuff repairs have been shown to be effective if at least ½ of the infraspinatus can be repaired to bone. ⁹ Partial repairs are recommended whenever complete closure of the defect is not possible. The author advises against transfer of rotator cuff tendons (subscapularis transfer), because they change the mechanics of the shoulder and can weaken the transferred muscle-tendon units significantly.

In general, for rotator cuff tears that are not fully repairable, the surgeon should consider subacromial smoothing as recommended by Harryman ³² rather than standard acromioplasty to preserve the coracoacromial arch as a constraint to proximal migration.

Nonmobile Tears

In less than 5% of the large and massive tears in the author’s practice, the tear is contracted and nonmobile. Tauro ⁴⁹ advocated an arthroscopic interval slide for these patients, doing an arthroscopic release of the coracohumeral ligament. This release sometimes will achieve an additional 1 to 2 cm of lateral excursion of the supraspinatus tendon, thereby permitting a greater degree of partial repair than would have been possible without the release. The author’s experience in doing 12 arthroscopic interval sides is that six patients improved their strength and motion by varying amounts and the other six did not improve. It is obvious that the results are variable, but the author uses this technique only as a last resort.

Contracted nonmobile rotator cuff tears are chronic, long-standing tears with an unpredictable potential for improvement. Arthroscopic interval slide, although it may improve function, must be considered a heroic intervention for a desperate problem.

Arthroscopic Subscapularis Repair

Arthroscopic subscapularis repair was done in 32 patients between August 1996 and May 2000. ¹⁹ Within that group, 17 patients had massive rotator cuff tears that included the subscapularis, supraspinatus, and infraspinatus, with an average tear size of 5 cm × 8 cm. Ten of these patients had proximal humeral migration as shown on anteroposterior radiographs obtained preoperatively. Eight of these 10 patients (with preliminary followup of at least 3 months) have had radiographically-proven reversal of their proximal humeral migration. In addition, these eight patients improved their overhead function from a preoperative shoulder shrug with attempted elevation of the arm to functional overhead use of the arm postoperatively.

Results of Arthroscopic Subscapularis Repair

Twenty-five patients with arthroscopic subscapularis repair were followed up for at least 3 months, with an average followup of 10.7 months (range, 3 months–48 months). The average time from onset of symptoms to surgery was 18.9 months (range, 1–72 months), indicating a significant delay before surgical repair. University of California Los Angeles scores ²⁵ increased from a preoperative average of 10.7 to a postoperative average of 30.5 (p < 0.0001). Forward flexion increased from an average 96.3° preoperatively to an average 146.1° postoperatively (p = 0.0016). By University of California Los Angeles criteria, excellent and good results were obtained in 92% of patients, with one fair and one poor result.

Results of Arthroscopic Repair of Massive Rotator Cuff Tears

The results of arthroscopic repair of 59 rotator cuff tears done between September 1993 and August 1997 recently were reviewed. The average followup was 3.5 years (range, 2–5 years). These tears were subdivided into groups according to tear diameter, using the classification system of DeOrio and Cofield ²³ as follows: small (< 1 cm); medium (1–3 cm); large (3–5 cm); and massive (> 5 cm). Preoperative and postoperative University of California Los Angeles scores were determined for each group, and intergroup comparisons also were done. Thirteen tears comprised the massive category. Two of these were crescent-type tears that were repaired directly to bone, and 11 were U-shaped tears that were repaired by a margin convergence technique. None of these massive tears involved the subscapularis. The average University of California Los Angeles scores improved from 14.0 before surgery (poor) to 29.9 (good) after surgery. Forward flexion improved from 90° to 132°. Improvement in flexion and University of California Los Angeles score were highly significant (p < 0.0001). By University of California Los Angeles criteria, good and excellent results were achieved in 92% of these patients.

Between-group comparisons for the four groups of tear sizes were made by analysis of variance (ANOVA) and confirmed by a power analysis that compared University of California Los Angeles score improvements between groups to the standard deviations within groups. This analysis showed no between-group differences. That is, the patients with massive tears did as well as the patients with small, medium, and large tears, with results independent of tear size.

Another interesting analysis was done comparing results of all tears repaired directly to bone (crescent-shaped; 34 patients) versus tears repaired by margin convergence (U-shaped; 25 patients). Comparison of results showed no difference between these two groups (p > 0.05), validating selection criteria for repair of U-shaped tears by margin convergence. Despite the fact that the crescent-shaped tears were predominantly in the smaller categories and the U-shaped tears were mostly in the massive category, the end results for these two groups were not statistically significant. This result is different from the reported results of open cuff repair, where larger tear sizes have been shown to have poorer results than smaller tear sizes, and it confirms the validity of repair by margin convergence. ^3,23,34,37

There are a few rotator cuff tears (those associated with cuff-tear arthropathy) that defy repair by any means, open or arthroscopic. For all other tears, arthroscopic repair is possible. The author’s results of arthroscopic cuff repair are as good as, or better than, reported results of open repair. The most striking revelation of the followup study is that patients with arthroscopic repairs of massive tears did as well as patients with arthroscopic repairs of smaller tears. Recognition of tear patterns and appropriate application of margin convergence along with other biomechanical principles (loop security, knot security) have enabled us to arthroscopically produce biomechanically secure repairs.

Arthroscopic subscapularis repair represents an exciting new frontier. There have been no previous reports of arthroscopic subscapularis repair. The preliminary results indicate the potential for dramatic functional improvement, particularly in patients with proximal migration of the humerus.

It is interesting to reflect that, in just 10 short years, the arthroscopic management of massive rotator cuff tears has shifted from debridement to repair of virtually all tears. All that remains to be done is to streamline and simplify the techniques so that most orthopaedic surgeons can perform them. Despite this progress, massive tears by their very nature will never be amenable to a simple-minded approach. Every massive tear requires a thoughtful analysis centered on basic anatomic and biomechanical principles. Hopefully the principles outlined in this review will serve as a nucleus for creative solutions by orthopaedic surgeons involved in this exciting and challenging arena.