Arthroscopic reconstruction of posterior glenoid bone loss with distal tibia allograft
Posterior glenohumeral instability is rare, accounting for approximately 5% of cases of shoulder instability. Although bone loss is implicated in most cases of recurrent anterior glenohumeral instability, the impact of glenoid bone loss on posterior instability is poorly understood. Specifically, the quantity of posterior glenoid bone loss that would prohibit the success of a posterior soft tissue stabilization procedure alone for recurrent posterior instability is unknown.
Reconstructive options for posterior glenoid bone loss are limited when compared with the options available for anterior glenoid bony reconstruction. The most often reported reconstruction technique for posterior glenoid reconstruction is the use of autologous iliac crest bone graft (ICBG) as a posterior bone block. This approach utilizes the ICBG as an extra-articular, nonanatomic, structural block to posterior humeral head translation. Long-term clinical outcomes following this procedure are somewhat concerning, with multiple authors reporting high rates of patient dissatisfaction, inability to return to desired level of activity, recurrence of instability and glenohumeral arthritis.
Alternatives to ICBG include augmentation with fresh osteochondral allograft, including glenoid allograft and fresh distal tibia allograft (DTA). In the anterior glenoid, reconstruction with DTA has been proposed as an effective surgical option for reducing the rate of dislocation clinically and restoring more normal contact pressures biomechanically. Recently, biomechanical work has demonstrated that in the setting of a 20% posterior glenoid bone defect, reconstruction with DTA is able to restore the articular conformity of the reconstructed glenoid to nearly the intact state. Clinical data is limited to short-term case reports, with encouraging early results. Here, we describe our preferred approach to arthroscopic reconstruction of posterior glenoid bone loss with DTA.
Images: Romeo AA
Patient positioning, portal placement
Our preference for arthroscopic reconstruction of posterior glenoid bone loss with DTA includes positioning the patient in the lateral decubitus position utilizing a traction set-up (Arthrex positioner; Arthrex Inc.), which allows for distraction and lateral translation of the humeral head. The patient is positioned in the lateral decubitus position to allow for distraction and lateral translation of the humeral head. Portals utilized for this approach include a standard posterior portal, a standard anterior rotator interval portal for both visualization and instrumentation and finally, a 7 o’clock posterolateral accessory portal to allow for direct access to the posterior-inferior aspect of the glenoid.The 7 o’clock posterolateral accessory portal is established approximately 4 cm off of the posterolateral border of the acromion, first percutaneously via spinal needle placement under direct visualization, followed by the insertion of serial dilators and ultimately, a cannula (6.5 mm or 8.25 mm).
Diagnostic arthroscopy, labrum preparation
During diagnostic arthroscopy, disruption of the posterior-inferior capsulolabral complex, as well as associated posterior-inferior capsular redundancy, is encountered. In addition, any associated concomitant pathology is visualized, including reverse Hill-Sachs lesions, reverse humeral avulsion of the glenohumeral ligament lesions, and/or large/circumferential labral lesions. The degree of posterior glenoid bone loss is quantified utilizing a calibrated arthroscopic probe (Figure 1); typically lesions of 25% to 30% the glenoid width equate to approximately 8 mm to 9 mm of bone loss, and thus following appropriate quantification of bone loss, the anticipated size of the allograft required can be estimated.
In the setting of posterior instability associated with posterior glenoid bone loss, the posterior band of the inferior glenohumeral ligament (PIGHL) and its associated capsular attachments are often scarred in, away from their anatomic origin on the posterior-inferior glenoid rim. To mobilize the scarred-in tissue, a 30° angled arthroscopic elevator is used to elevate the tissue through the 7 o’clock portal. An angled arthroscopic rasp also can be used. It is important to exert caution when releasing the adhesions medially and superiorly, as to avoid iatrogenic injury to the suprascapular nerve. In addition, one must perform this release gently as the mobilized capsulolabral tissue ultimately will be repaired down to the native glenoid and posterior aspect of the DTA at the conclusion of the case.
After adequate mobilization of the posterior labrum, the posterior-inferior glenoid rim must be prepared down to a bleeding surface of cancellous bone. To facilitate this, we use a high-speed cylindrical burr via the 7-o’clock portal while viewing from anterior. The glenoid is prepared with the burr (Figure 2) until a flat surface of cancellous bone is created, essentially perpendicular to the glenoid surface. A flat surface is necessary to allow the prepared allograft to sit flush on the glenoid.
Allograft preparation (back table)
At any point throughout the operative procedure, the fresh DTA can be prepared on the back table (Figure 3). The allograft is delivered as an entire distal tibial plafond, and for the purposes of this procedure and to provide a congruent arc (following reconstruction) with the humeral head, the lateral one-third of the plafond is harvested. A 0.5-inch sagittal saw is then used to shape the allograft to the previously measured size of the posterior glenoid defect (measured earlier with CT and/or via diagnostic arthroscopy). Of utmost importance is fashioning this allograft such that a 10° angled cut is made along the portion (more medial aspect of tibial plafond) that will ultimately be placed against the glenoid surface in order to match the radius of curvature of the glenoid and provide a congruent osteoarticular surface for articulation with the humeral head. Irrigation fluid should be continuously applied to the allograft during all cutting with the saw to minimize heat-induced necrosis. A rongeur, as well as the saw, are then used to fine-tune the allograft into an appropriate shape for reconstruction. As mentioned previously, the allograft will typically be 8 mm to 9 mm in width (for a 25% glenoid surface area defect) and approximately 22 mm to 25 mm in length. The allograft is then washed with pulsatile lavage (normal saline with bacitracin) to remove marrow elements. The superior- and inferior-most aspects of the allograft are rounded with the saw and/or a rongeur. Typical allograft dimensions for 25% glenoid bone loss are 7-mm to 8-mm wide and 25-mm long.
Once the allograft is shaped, it is then power-washed with pulse lavage (3 L of normal saline solution with bacitracin) to remove any residual marrow elements. Next, using a coracoid offset drill guide (comes in 4-mm, 6-mm and 8-mm offsets), a 4.0-mm drill is used to drill two holes in the allograft (approximately 1-cm apart), each of which will be used for screw fixation. Alternatively, two 1.6-mm K-wires can be drilled into the allograft, which can be used to help insert and control orientation of the allograft.
The allograft will be inserted onto the posterior glenoid face via a 3-cm accessory incision typically 2 cm medial to the 7 o’clock posterolateral portal incision. Following skin incision, blunt finger dissection is used through the deltoid until the infraspinatus muscle belly is visualized. Palpating the glenohumeral joint, Metzembaum scissors are next used to establish a 3-cm opening within the infraspinatus muscle belly in line with its muscle fibers (so as to not injure the lateral branch of the suprascapular nerve), effectively exposing the posterior joint capsule.
A 3-cm longitudinal capsulotomy is then sharply made, in line with the glenohumeral joint, taking care to avoid injury to the axillary nerve inferiorly; one must be cautious with retractor placement to avoid neuropraxia as well as with the capsulotomy incision itself to avoid direct injury to the nerve. The capsulotomy should be established approximately 1 cm off of the glenoid face. A straight hemostat is inserted into the capsulotomy to widen the working area (Figure 4), followed by widening of the capsulotomy bluntly. Next, the allograft is inserted longitudinally through the capsulotomy incision under direct visualization (Figure 5), with the arthroscope in the anterior portal. An arthroscopic sled can be used to help facilitate the passage of the allograft through the posterior incision. Once visualized within the joint, the allograft is rotated 90° such that the allograft then aligns with the glenoid defect, with the pre-drilled holes aligned perpendicular to the glenoid; a switching stick can be used to help reduce the allograft to the glenoid and correct any malrotation.
The offset drill guide used to drill the pilot holes into the allograft is then inserted against the allograft (Figure 6, page 14), and two 1.6-mm K-wires are placed through both cannulas of the guide into the allograft. The reduction of the allograft to the glenoid is confirmed, and the wires are drilled bicortical through the glenoid (Figure 7). The K-wires are then over-drilled with a 2.7-mm cannulated drill bit into the native glenoid, and the guide is subsequently removed after the allograft is confirmed to be flush to the glenoid (Figure 8). The screw depth is then measured off of each K-wire, and 3.75-mm titanium, fully threaded, cannulated screws with washers are placed (Arthrex Inc.). Screws are typically 32-mm to 36-mm in length.
Soft tissue repair and rehabilitation
After confirming appropriate allograft fixation into the native glenoid, the posterior capsulolabral repair is performed (Figure 9). With the arthroscope in the anterior portal, double-loaded biocomposite 3-mm suture anchors (SutureTak; Arthrex Inc.) are inserted, beginning with an anchor placed at the 7 o’clock position and next at the 8 o’clock position. The 7 o’clock posterolateral accessory portal is used to insert the anchors, while viewing from anterior; in addition, an arthroscopic grasper inserted through the posterior portal maintains the PIGHL tissue in an anatomically reduced position. A suture passing device (Spectrum; ConMed Linvatec) is then inserted through the anterior portal, penetrated through the posterior capsulolabral tissue and used to shuttle the suture from the anchor through the tissue. The sutures are tied arthroscopically using the knot-tying technique of choice; we prefer reverse posts with alternating half-hitches. All steps are repeated for the next (8 o’clock) anchor. The shoulder should be maintained in a neutral position to avoid stiffness following repair. After both sutures are tied, the allograft is now effectively “intra-articular.” The capsulotomy is closed side-to-side with an interrupted No. 0 polydioxanone suture (PDS; Ethicon), and the portals are closed in standard fashion.
A shoulder brace with a neutral rotation wedge is applied to the surgical side to hold the arm in the handshake position, which minimizes the tension on the posterior capsule. Pendulum exercises and unrestricted range of motion to the elbow, wrist and fingers are allowed within the first 3 days to 7 days as the early postoperative pain subsides. Shoulder range of motion to 90° of elevation and external rotation as tolerated is begun at 1 month. Full active motion is initiated at 6 weeks following imaging (radiograph or CT) that supports allograft-glenoid healing. Strengthening is not permitted until at least 3 months after surgery. Return to full activities, including athletic activities, is anticipated at approximately 6 months to 9 months, pending the desired activity level.
Fresh osteochondral DTA is a viable alternative to bone block reconstruction (i.e., with iliac crest) for the treatment of large posterior glenoid bone defects in the setting of glenohumeral instability. As shown in cadaveric studies, a nearly identical radius of curvature exists between the distal tibia and the glenoid, even among non-side matched cadaveric specimens. This anatomy allows the distal tibia articular surface to maintain excellent conformity to the humeral head throughout a full arc of motion.
DTA itself is comprised of dense, corticocancellous bone, making it ideal for screw fixation and furthermore, contains a robust cartilagenous surface that allows for an anatomic, osteoarticular glenoid surface reconstruction. Importantly, long-term clinical outcomes following posterior DTA reconstruction are not available, and currently, the literature is limited to biomechanical data and case reports. Certainly, concerns about allograft safety, expense and longevity exist, and caution must be employed when counseling patients who may be indicated for this procedure. Further clinical and laboratory work is needed to determine to determine the effectiveness of this allograft over time.
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- For more information:
- Rachel M. Frank, MD, and Anthony A. Romeo, MD, can be reached at 1611 W. Harrison St., Suite 300, Chicago, IL 60612. Frank’s email: email@example.com. Romeo’s email: firstname.lastname@example.org.
- Matthew T. Provencher, MD, can be reached at the Massachusetts General Sports Medicine Hospital, 175 Cambridge St., Suite 400, Boston, MA 02114.
Disclosures: Frank reports no relevant financial disclosures. Provencher reports he receives royalties from and is a consultant for Arthrex Inc.; is a consultant for Joint Restoration Foundation; and receives publishing royalties from SLACK Incorporated. Romeo reports he receives royalties from, is on the speakers bureau and a consultant for Arthrex Inc.; does contracted research for Arthrex Inc. and DJO Surgical; receives institutional grants from AANA and MLB; and receives institutional research support from Arthrex Inc., Ossur, Smith & Nephew, ConMed Linvatec, Athletico and Miomed.