Posterior instability—operative technique and surgical outcomes

Preferred technique

Initial setup

Arthroscopic shoulder stabilization is performed with the use of general anesthesia. After induction, both the operative and contralateral shoulder are examined in the supine position to allow for side-to-side comparison. Specific attention is paid to anterior, posterior, and inferior glenohumeral translation, evaluated with the load and shift and inferior sulcus tests, respectively. An exam under anesthesia is preferred, as it allows for confirmation of prior clinical exam findings, while eliminating potential confounders such as patient guarding or apprehension.

We perform all labral repairs with the patient in the lateral decubitus position and secured on a bean bag. An axillary roll is placed along with a pillow between the knees, and cushioned pads are positioned under the down leg at the level of the fibular head. The operative extremity is placed in a distractor at the foot of the bed with all but the most distal aspect of the arm incorporated into the sterile field to allow for dynamic intraoperative assessment with the help of an assistant. At a position of 45 degrees of abduction and 20 degrees of flexion, 10 lb of traction is applied, displacing the humeral head anteriorly and inferiorly and facilitating an unobstructed view of the posterior labrum.

Portal placement and diagnostic arthroscopy

The glenohumeral joint is first insufflated with 50 mL of saline from the position of the posterior portal, insufflating the joint and allowing for safe insertion of a trochar within the glenohumeral joint. If appropriately performed, the arm is seen to internally rotate as fluid is inserted. In planning for posterior labral repair, the posterior portal is modified and placed 1 cm distal and 1 cm lateral from a standard posterior entry point. This position facilitates access and drilling trajectory toward the posterior labrum. Difficulty in posterior access can often be encountered with posterior portals placed further superior or medial from this position. Correct portal placement should correlate with the mid-glenoid position, localized to the mid-point of the anterior to posterior width, with entry directed toward the 2 o’clock position of a right shoulder.

As with any shoulder arthroscopy, treatment of a posterior labral injury begins with a thorough evaluation of the entire glenohumeral joint. Diagnostic arthroscopy is performed with a 30-degree arthroscopy lens to evaluate the entirety of the glenoid-labrum complex while ensuring that other concomitant injury, such as articular-sided rotator cuff lesions, biceps pathology, and cartilaginous defects, are not overlooked. An anterior working portal is created under direct visualization through either an outside-in or inside-out technique, which is our preference. The anterior portal is created just superior to the superior glenohumeral ligament within the rotator cuff interval. With regard to labral injury, the entirety of the labrum must be carefully evaluated, as an overlooked posterior injury may propagate anteriorly, resulting in a second area in need of repair. In particular, the superior labrum must be evaluated for a type VIII superior labrum anterior posterior (SLAP) lesion with posterior extension. In evaluating the superior labrum for such injuries, we perform a “biceps invagination test” to assess for superior labral stability. The biceps tendon is visualized and the arm is disconnected from traction and brought into an overhead abducted and externally rotated position. A positive test is confirmed when the portion of the biceps tendon just distal to its anchor at the 12 o’clock position on the labrum is found to fold in or invaginate while in the abducted and externally rotated position. Such dynamic testing also allows for evaluation of posterior-superior peel-back, an additional indicator of a compromised bicipital anchor.

Once diagnostic arthroscopy is completed with all pathology identified, working cannulas are introduced to address areas of need. In the setting of concomitant superior and posterior lesions, a minimally invasive, low-profile, 5 mm cannula is introduced at the 11 o’clock position (right shoulder) just posterior to the biceps tendon through a small incision made at the midpoint between the anterolateral and posterolateral extent of the acromion. For strictly posterior lesions, a two-cannula approach is preferred, with two 8.25 mm threaded clear plastic cannulas placed at the anterior and posterior portal positions previously described. For posterior work, viewing is performed through the anterior cannula, with a 70-degree arthroscopy lens preferred to facilitate peripheral labral viewing. Posterior labral pathology typically encountered in the setting of instability includes (1) discrete tearing or fraying, (2) detachment from the glenoid rim, (3) a patulous posterior capsule, (4) tears within the posterior capsule, (5) undersurface tearing of the articular side of the rotator cuff, or (6) an enlarged rotator interval. One should also be mindful of a Kim lesion or subtle detachment of the posterior labrum, which is often difficult to visualize.

For injury patterns requiring a more inferior anchor at the 6 o’clock position, a stab incision is made 2 to 3 fingerbreadths directly distal to the initial posterior portal to allow for percutaneous placement of a knotless type 3 mm anchor. Finally, in the setting of concomitant anterior-inferior injury, such as with a Bankart lesion, a second distal-anterior cannula can be employed to facilitate more inferior access. Prior cadaveric work has demonstrated this 7 o’clock position (right shoulder) to be safe for portal placement, lying 29 mm away from the suprascapular nerve, and 39 mm from axillary nerve and posterior humeral circumflex artery.

Labral preparation

Now viewing anterior to posterior, an elevator or arthroscopic chisel is introduced through the posterior portal and the labrum is freed from the medial glenoid rim. Specific attention is required to ensure proper elevation of any scarred, and often medialized, labral tissue, allowing for adequate mobility to ensure successful reduction after suture passage. A ball-typed meniscal rasp is then employed in combination with a shaver or bone cutter to achieve a bleeding glenoid rim prior to anchor placement. Of note, debridement of actual labral tissue should be limited to only frayed or otherwise compromised tissue, being mindful to preserve as much labral tissue as possible for subsequent repair ( Fig. 35.1 ).

Suture passage and anchored labral repair

The labrum is repaired with suture anchors placed within the glenoid rim. Our preference is to use a 2.9 mm Biocomposite PushLock Anchor (Arthrex Inc.) in most individuals, downsizing to a 2.4 mm anchor in individuals with a smaller glenoid volume. The position and number of sutures used should be tailored to fit the extent of the labral injury encountered. As an example, using the clock face nomenclature with 3 o’clock anteriorly and 9 o’clock posteriorly, we examine a posterior tear extending from the 6 to 9 o’clock positions. Our planned repair would incorporate anchors at the 6:30, 7:30, 8:30, and 9:30 positions. The most inferior anchor is placed slightly more superior than the inferior-most aspect of the tear (6:30 anchor for a tear ending at 6) to allow for a concomitant superior capsulolabral shift. This technique increases the tension on the inferior band of the inferior glenohumeral ligament, providing additional posterior stability.

Once anchor positions are determined, a PDS suture shuttling stitch is passed through the periphery and into the center of the labrum with a curved lasso device (Reelpass, Arthrex Inc.), targeting an exit point at the exact level where the corresponding anchor will be placed. An excess amount of the PDS stitch is passed through the labrum and the stitch is continually deployed as the passer is withdrawn. The passed end is then secured for suture management, while a grasper is used to retrieve the stitch end that was passed through the labrum. This tail is then used to shuttle suture tape back through the labrum in the desired location. The PDS is fashioned into a single loop and cinched tight while a small amount of the tape stitch is pulled in the opposite direction to provide a counterforce to secure the knot. The more posterior tail of the PDS is then pulled to deliver the secured tape through the labrum. We prefer a bouncing type maneuver with short quick tugs of the lead limb employed to help deliver the tape and PDS stitch through more robust labral tissue ( Figs. 35.2 and 35.3 ).

Anchors should be placed on the glenoid chondral rim, rather than the glenoid neck, to best reproduce native labral anatomy. An offset drill with matching guide is used to ensure anatomic positioning while steadying the drill trajectory to avoid damage to the glenoid chondral surface. Of note, the labrum attaches in a more en face position below a dividing line running horizontally across the glenoid from the 3 to 9 o’clock position. Thus, to best recreate the labrum’s natural attachment point, inferiorly placed anchors should be positioned just lateral to the glenoid neck, at a position approximately 3 mm on the glenoid face.

Once a drill hole has been created, the previously passed labral tape is loaded into the anchor, which is then inserted while keeping tension on the tails to allow the anchor to slide down to the position of insertion on the labrum. We use a technique of delivering the anchor past the actual location of the hole, allowing a small amount of slack equivalent to the depth of the anchor to be passed medial to the drill hole, before inserting the anchor into the glenoid bone. In this way, correct tensioning can be ensured prior to anchor placement. Once placed, the inserter is removed and the suture tails cut flush with the adjacent labral tissue.

Injury specifics

Based on history and physical exam, certain patterns of posterior labral injury also can be expected, facilitating an appropriate approach to repair. In particular, posterior labral injuries in a thrower’s shoulder will often begin superiorly, extending posteroinferiorly with a longitudinal split in the labrum noted. It is imperative to recognize such longitudinal tears to ensure that an anatomic repair is performed in a patient population that is already at higher risk for failure. Additionally, in the overhead athlete, one must be mindful of the importance of maintaining mobility in the posterosuperior quadrant by incorporating only labral tissue, and not capsule, into anchored repairs. Preservation of such mobility is crucial to allowing the overhead athlete to achieve the maximal external rotation necessary to achieve the slot position and maximal ball velocity. ^,

Repair with capsular plication

It is essential to recognize and diagnose a patulous posterior capsule based on preoperative exam and imaging, as both treatment and outcomes vary significantly for multidirectional instability (MDI) when compared to unidirectional, posterior laxity (see outcomes section below). Accordingly, those with an acute injury and minimal capsular stretching require much less of a capsular repair and advancement than those with MDI or chronic posterior instability.

When a patulous capsule is identified that warrants a repair, the tissue must first be abraded using a technique similar to that used in preparing the medial glenoid neck. Extreme care must be taken to not puncture through the often-flimsy capsular tissue to ensure adequate tissue remains for repair. Our preference is to use a meniscal rasp over a motorized shaver to allow for better control. Next, capsular plication is performed using the same sutures/tapes that are passed through anchors for labral repairs. This method is preferred over nonanchored fixation, as the use of anchors has been demonstrated to result in superior clinical outcomes. ^, In this technique suture passage with the lasso device is enlarged to grab the capsule approximately 1 cm lateral to the edge of the labral tear in conjunction with capturing of the labral tissue from periphery to center as described above. Following the shuttling of a tape, this allows for incorporation of the capsule when the anchor is placed and tensioned.

Closure of the posterior portal

It is our practice to always close the posterior portal site to avoid any iatrogenic instability resulting from compromise of the posterior capsule secondary to cannula placement. While viewing from anterior, the posterior cannula is pulled back to the point where the capsule directly drapes over its tip with the split in the capsule directly over the cannula’s exit. A PDS suture is then passed through the cannula and just inferior to the inferior aspect of the split and deployed into the shoulder. A Labral Penetrator (Arthrex Inc.) is then employed to puncture through the capsule just superior to the superior most aspect of the capsular tear. We prefer a penetrator to a bird beak, as its use results in a smaller puncture hole in the superior aspect of the capsular rent. The two limbs are then pulled tight to ensure proper capture and tied to repair the previously created capsular defect ( Fig. 35.4 ).