Arthroscopic Technique for Bone Augmentation With Suture Button Fixation for Anterior Shoulder Instability.

Glenoid bone loss remains a significant risk factor for recurrent instability after shoulder dislocation. Several options exist for glenoid bone graft augmentation, including autograft and allograft options. Strengths and weaknesses exist for each. Graft fixation with screws remains a key concern for technical viability requiring a medial portal as well as the risk of graft osteolysis. Suture button suspensory fixation is a new technique recently described for arthroscopic iliac crest bone graft; however, no description exists concerning osteochondral graft fixation. We describe an arthroscopic technique for distal tibial allograft glenoid augmentation with suspensory suture button fixation. The rationale and technical aspects of this procedure are discussed.

Glenoid bone loss remains a key risk factor for recurrent shoulder instability after dislocation.1, 2, 3, 4, 5 Previous literature has examined critically the amount of bone loss required to increase risk of instability; however, it is widely accepted that bone loss exceeding 15% to 20% increases risk for recurrence significantly.,,6, 7, 8 Because of the increased risk for recurrent instability, many techniques have been described to augment bone loss and thus decrease recurrent instability risk including the Latarjet, coracoid transfers, iliac crest bone graft, distal clavicle osteochondral autograft, and the Bristow.,9, 10, 11, 12, 13, 14, 15 Most of these have been described being fixed with screws, which presents a unique set of challenges. Technically, because screws require perpendicular placement, they are difficult to place arthroscopically, and, when done, must be placed far medially in proximity to the brachial plexus. In addition, because bone osteolysis has been described, especially around the superior screw, painful hardware can result.17, 18, 19, 20, 21, 22, 23 These open techniques are not without complication, and more recent arthroscopic techniques to augment bone loss have been described.,24, 25, 26, 27, 28, 29, 30 Despite the advent of these techniques, difficulty with fixation arthroscopically remains a concern.,, Fixation using suspensory cortical buttons has recently been described for the Bristow procedure and may be an attractive alternative to eliminate the complications associated with screw fixation.,,

Recently, the literature has reported suspensory fixation using iliac crest autograft; however, we discuss a technique for arthroscopic distal tibia allograft osteochondral fixation using suture button device. The purpose of this technique is to describe the rationale and technical considerations behind the technique of osteochondral bone grafting of glenoid bone defects using a simple arthroscopic technique with suspensory fixation. The advantage of this technique is that it delivers an osteochondral source arthroscopically using similar techniques and instrumentation that the arthroscopic surgeon is already familiar with. In addition, because the graft can be delivered through standard anterior portals, the risk and technical difficulty with working medial to the coracoid or splitting the subscapularis are completely avoided.

Surgical Technique

Step 1: Preoperative Workup

Patients who present with glenohumeral instability undergo a standardized workup including a detailed history and physical as well as advanced imaging to critically assess soft tissues and glenoid bone loss. The exact degree of glenoid bone loss is calculated in each patient and, in conjunction with history and physical examination, used to determine eligibility for the outlined procedure. Bone loss of 20% is a relative indication for a bone augmentation procedure.

Step 2: Positioning

After examination under general anesthesia in the operating theater, the patient is positioned in the lateral decubitus position using a bean bag. The arm is held in position as is standard at our institution, with a padded arm sleeve and traction device with a lateral distractor (STAR sleeve; Arthrex, Naples, FL). Standard portals are established including the posterior portal (1-cm medial and 2-cm distal to the posterolateral acromial border) and the anterosuperior and mid-glenoid portals. The arthroscope is inserted posteriorly after creation of the posterior portal and the remaining portals are established under direct visualization using an outside-in technique.

Step 3: Diagnostic Arthroscopy, Biologic/Fixation Preparation

In sequential order, a diagnostic arthroscopy is performed to confirm previously diagnosed pathology. Attention is then turned to the area of bone loss visualized on imaging preoperatively. The arthroscope is removed from the posterior portal and inserted anteriorly while a probe is placed under visualization through the posterior portal and intraarticular measurements are taken to confirm bone loss exceeding 20% (Fig 1). After confirmation of bone loss and documentation, aggressive labral and capsular liberation is undertaken (Fig 2). The anterior glenoid surface is prepared down to viable bone with the goal of creating a flush surface for graft placement. Particular care is taken to ensure sufficient room for graft fixation within the raised labrum.

Fig 1

Intraarticular measurement and confirmation of glenoid bone loss through the posterior portal as viewed from the anterosuperior portal.

Fig 2

Aggressive labral elevation from anterior glenoid through the mid-glenoid portal as viewed from the anterosuperior portal.

Next, a spinal needle is used to localize posteriorly so that, when placed, the drill guide will come perpendicular to the desired position of the graft. An Arthrex Latarjet guide (4- to 6-mm offset) is placed through an enlarged skin incision posteriorly at the level of the equator. This should fit flush on the anterior glenoid prepared surface and perpendicular to desired graft position. Next, with the arthroscope in the anterosuperior portal, 2 k-wires are drilled through the guide in the back and visualized emerging through the front of the glenoid (Fig 3). These k-wires may remain in place while attention is turned to graft preparation.

Fig 3

Visualization of the glenohumeral joint through the anterosuperior portal of 2 k-wires drilled from posterior to anterior.

Step 4: Graft Preparation

The distal tibial allograft is a versatile graft and carries with it the significant advantage of a chondral component. The osteochondral allograft is cut to the appropriate size based off of preoperative imaging calculations as well as intraoperative confirmation (in most cases, 7- to 8 mm is sufficient to restore approximately 30% of bone loss)., The same arthroscopic drill guide is used to create 2 identical tunnels through the allograft to ensure exactly analogous holes to the graft’s glenoid counterpart both in terms of depth from the articular surface and distance apart. Next, using the lead suture, the buttons are passed through the bone graft outside of the shoulder and deployed (Fig 4) so that they are in the fixed or “flipped position.”

Fig 4

Deployment of suture buttons external to mid-glenoid portal in preparation of graft passage.

Step 5: Graft Delivery and Fixation

A cannulated drill is passed over the k-wires remaining in the glenoid form step 3 to create tunnels for the suspensory fixation. The cannulated drill can then be removed and FiberStick red tubes are inserted over the k-wires to ensure proper positioning. The wires are then removed, leaving the tubes behind and the FiberStick sutures are used to go through these drill holes in the glenoid. The sutures can be retrieved through the mid-glenoid portal for management. Next, the posterior suture is attached to the Arthrex mini-tightrope. Pulling from the front delivers the button through the glenoid and out the midglenoid portal. This process is repeated for the superior tunnel. Next, the graft is delivered through the rotator interval. This is achieved by use of a large clamp to assist the graft passage through rotator interval (Fig 5). While the graft is being passed, slack is removed by pulling the construct posteriorly to deliver the graft into the joint free of suture tangles. Using a combination of arthroscopic grasper through the mid-glenoid portal as well as variable tension on superior and inferior sutures posteriorly allows for gross alignment of the graft to the prepared anterior glenoid surface (Fig 6). Fine-tuned placement of the graft can be accomplished while holding manual tension on the sutures posteriorly. Once the graft is in position, the mini-tightropes are tensioned sequentially to eliminate any gaps between the graft and the native glenoid (Fig 7). Five half hitches under tension are tied posteriorly to ensure no slippage of the graft once tightened.

Fig 5

Delivery of graft through mid-glenoid portal using a clamp anteriorly and gradual tension removing slack on the suture construct posteriorly.

Fig 6

Visualization of intraarticular graft delivery as viewed from posterior portal. Gross tension on suture construct posteriorly roughly aligns graft to anterior glenoid surface.

Fig 7

Visualization intraarticularly of the final positioning of graft with appropriate tensioning creating a congruent osteochondral construct with overlying labrum before labral reapproximation.

Step 6: Labral Restoration

Now that the graft is firmly fixed in place, attention is turned to restoration of the labrum over the osteochondral allograft surface. Suture anchors can be added to restore the normal labral junction above and below the graft. Additionally, extra sutures may be left in the buttons themselves to allow incorporation of the labrum against the graft. After restoration, all arthroscopic instruments are removed and the skin is closed and dressed sterilely.

Step 7: Rehabilitation Protocol

Patients are placed in standard Latarjet protocol for our institution, which includes a neutral rotation sling for 6 weeks. Patients may come out of the sling to begin pendulum movements immediately with graduation to passive motion at 3 weeks. At 8 weeks, follow-up imaging is obtained, and our goal is for complete range of motion to be restored at this time. If graft incorporation on imaging is observed, active range of motion is begun. Strengthening is added at 16 weeks postoperatively and full activity return is 6 months postoperatively after final radiographs are obtained.

Discussion

Glenoid bone loss remains a key factor in determining the overall risk of shoulder instability recurrence after dislocation.2, 3, 4, 5 Bone loss exceeding 15% to 20% has been shown to significantly increase risk of recurrent shoulder instability after surgical fixation if not addressed.,, Several open and arthroscopic options for glenoid bone graft augmentation exist, each with certain benefits and disadvantages.,,, However, the ideal graft for the treatment of shoulder instability secondary to bone loss would be osteochondral, autograft, amenable to arthroscopic placement, affordable, minimally morbid, and technically feasible/reproducible.

Of the most commonly described arthroscopic techniques in the literature (Latarjet, iliac crest autograft, distal tibial allograft, and distal clavicular autograft), each has significant benefits and drawbacks to consider (Table 1).,,, Specifically, prior work has demonstrated the neurologic involvement of the Latarjet procedure, and arthroscopic screw fixation of bone graft often requires a far medial portal theoretically placing neurovascular structures at increased risk.34, 35, 36 Although clinical risk of true neurologic injury remains low, screw fixation of bone graft also carries the risk of graft osteolysis, cut out, and symptomatic harware.,,,,

Table 1

Advantages and Disadvantages of Common Glenoid Bone Grafts

	Advantages	Disadvantages
Iliac crest autograft	Anatomic restoration of contouring, incorporation, availability, cost	No chondral surface, donor site morbidity risk
Distal clavicle autograft	Osteochondral, availability, incorporation, cost	Donor site morbidity, prior acromioclavicular arthritis is a limiting factor
Latarjet/Bristow coracoid transfers	Availability, cost, sling effect	Nonanatomic solution, technically challenging, no chondral surface
Distal tibial allograft	Osteochondral, restoration of contouring, no donor site morbidity	Incorporation, cost, availability

Suspensory fixation has been described previously in the literature through an open technique as an alternative to screw fixation of with a similar biomechanical strength., Recently, Kalogrianitis et al. described an arthroscopic technique of iliac crest autograft bone augmentation with suspensory suture button fixation. However, the limitations of this graft include the lack of a chondral surface and significant donor site morbidity.,, We consider the proposed technique to have several advantages when compared with other common bone-restoring procedures (Table 1).

The goal of this paper was to describe a reproducible technique for the arthroscopic placement and suture button fixation of an osteochondral graft while also outlining the its limitations (Table 2). The technique details distal tibial allograft fixation (Fig 8). However, the technique of suture button fixation may be applicable for other types of graft fixation per the surgeon’s preference such as distal clavicular osteochondral fixation as well (Video 1). The benefits of this technique are stable fixation without risk of graft osteolysis from screws and avoidance of a far medial portal placement. The limitations include its technical difficulty, as well as the limitations of the graft choice (incorporation of allograft and cost). Future studies will need to look at clinical outcomes of suspensory fixation to validate initial promising biomechanical reports. The authors would consider an open Latarjet procedure as a salvage options in the case of a failed bone block.

Table 2

Pearls and Pitfalls of Arthroscopic Suture Button Fixation of Distal Tibial Allograft for Shoulder Instability

Pearls	Pitfalls
- Obtain a sufficiently wide exposure.	- Avoid inadequate exposure of the glenoid and labrum. Failure to expose or properly prepare the native bone will result in difficult graft placement and inadequate conformity.
- Use a spinal needle to localize where to place the graft (standard portal may be too low).	- Avoid inadequate opening of the rotator interval otherwise the graft will be difficult to pass.
- View from the anterosuperior portal when drilling from the back; may use a curette to protect the wires from inadvertently advancing during drilling.	- Make sure to properly localize the position of the posterior drill guide, it should be perpendicular to the defect and placed at the center of the defect (superior/inferior).
- Use the same drill guide for the glenoid and for the graft to ensure proper matching and alignment.	- Failure to manage sutures may result in a tangle and prevent graft passage.
- Use handheld tensioners to apply generous pressure to ensure graft conformity.	- Failure to appropriately tension the graft may result in poor congruity of the construct.

Fig 8

Cadaveric dissection after arthroscopic procedure demonstrating solid fixation of osteochondral allograft with suture button fixation.