9.1 Introduction

Burkhart coined the phrase “margin convergence” and described the biomechanical rationale for this surgical technique ¹ ; however, the concept of using side-to-side sutures in rotator cuff repair dates back to Codman ² and McLaughlin. ³ Knowledge of the principles, indications, techniques, and limitations of margin convergence techniques for arthroscopic rotator cuff repair will greatly aid shoulder surgeons in the care of their patients.

9.2 Goals of Procedure

Margin convergence techniques in arthroscopic rotator cuff repair serve the ultimate purpose of obtaining anatomic tendon-to-bone healing to restore pain-free and functional use of the shoulder.

9.3 Advantages

When used for appropriate rotator cuff tear patterns, margin convergence repair techniques achieve two goals: decreased strain along the free margin of the rotator cuff and increased likelihood of an anatomic repair construct. These advantages have led to excellent clinical results. ^{4 – 6} When significant anteroposterior mobility of the cuff tear exists, use of side-to-side suturing will counteract the deforming forces and make the reduction and repair construct more anatomic.

Biomechanical principles concerning the impact of strain and strain reduction on the rotator cuff have been laid out in detail by Burkhart previously ^{1 , 7} and have also been confirmed with biomechanical testing. ^{8 – 10} In short, margin convergence by side-to-side suturing creates a modified tear margin that has reduced strain for a given force from the cuff musculature. The reduced strain results from a smaller tear length at the apex and an increased cross-sectional area at the apex of the tear ( Fig. 9.1 ). Decreased strain is hypothesized to decrease pain, protect a tendon-to-bone repair construct, and prevent tear propagation. ⁸

9.4 Indications

In the authors’ opinion, repair of large to massive rotator cuff tears should be attempted for nearly all patients who do not have significant glenohumeral arthrosis (Hamada ¹¹ stages 4 to 5). Margin convergence techniques are then utilized as determined by the tear pattern as assessed intraoperatively. In Davidson and Burkhart’s geometric classification of rotator cuff tears, ¹² longitudinal (L-, reverse L-, or U-shaped) tears require some degree of anterior-to-posterior reduction and often require side-to-side suturing for reduction and/or repair. In particular, U-shaped tears, which have roughly equal anterior-to-posterior mobility of the tear leaves ( Fig. 9.2 ), often evolve from seemingly irreparable to easily reparable after side-to-side suturing ( Fig. 9.3 ). Finally, massive, contracted (immobile) tears repaired using interval slides or superior capsular reconstruction (SCR) often require reinforcement using side-to-side suturing after fixation of the tissue to the bone bed. ¹³

9.5 Contraindications

Margin convergence techniques should not be used for rotator cuff tear patterns for which they are not suited. For example, in a massive, contracted (immobile) tear, the surgeon might be able to “force” a few side-to-side sutures and be quickly done with the case when the best repair construct might instead be a well-done partial repair or SCR after mobilizing the tear fully with interval slides. Margin convergence should not be thought of as a panacea for all large to massive rotator cuff tears.

9.6 Preoperative Preparation/Positioning

Although intraoperative assessment should be the gold standard for assessing tear and repair patterns, preoperative MRI can be helpful for predicting these. ¹⁴ When planning for repair of large to massive cuff tears or in the revision setting, we prepare for the possibility of addressing an irreparable tear with arthroscopic dermal allograft SCR. ¹³

We perform all arthroscopic rotator cuff surgery in the lateral decubitus position with a standard operating room setup that includes a second assistant standing opposite the surgeon to provide adjustments to the arm, such as the posterior lever push. ¹⁵ We have found the lateral decubitus position to provide the best arthroscopic visualization, a critical factor for performing complex arthroscopic rotator cuff surgery.