Abstract
Background:
Posterior glenohumeral instability is much less common than anterior instability, and there is a paucity of studies looking at glenoid bone loss as it relates to posterior instability. However, while the data are not as robust, posterior glenoid bone loss can lead to recurrent instability and failed soft tissue procedures. Arthroscopic posterior glenoid augmentation with distal tibial allograft (DTA) is a minimally invasive option to restore stability and preserve function.
Indications:
The primary indication for posterior glenoid augmentation is posterior instability with >20% to 25% posterior glenoid bone loss or recurrent posterior instability after prior stabilization procedure. In this case, the patient is a 21-year-old man with recurrent instability after 2 prior soft tissue stabilization procedures.
Technique Description:
The patient was positioned in lateral decubitus, and portals were established. Arthroscopic evaluation was performed to assess the labrum, biceps, rotator cuff, glenoid, and humeral head. Glenoid mobilization was performed, and an incision was made for introduction of the bone block. The glenoid was prepared, and a trial was used to guide preparation of the graft, which was harvested from the articular cartilage of the distal tibia. The graft was irrigated and bathed in platelet-rich plasma (PRP) and then introduced and positioned for maximal coverage of the defect. Screw fixation was performed with two 3.75-mm screws. The posterior capsule was reapproximated, and a layered closure was performed.
Results:
Previous studies have reported significant improvements in patient-reported outcomes, high rates of healing, and no cases of recurrent instability after DTA for anterior glenoid bone loss. Additional studies have reported few patients with recurrent instability and no instances of partial or non-union. Significant loss of range of motion has not been reported in the most recent case series. One previous study reported significantly improved patient-reported outcomes and near-complete osseous reabsorption with DTA after failed Latarjet procedure.
Discussion/Conclusion:
Arthroscopic posterior glenoid augmentation with DTA is a viable treatment option for patients with shoulder pain and instability with >20% to 25% posterior glenoid bone loss and/or following prior stabilization procedures.
This is a visual representation of the abstract.
Video Transcript
This video describes our team’s technique for an arthroscopic posterior glenoid augmentation using a distal tibial allograft (DTA).
The author disclosures are as follows.
This video will describe the treatment indications, preoperative planning, surgical technique, potential complications, and rehabilitation protocol for posterior glenoid augmentation with DTA.
Our patient was a 21-year-old collegiate football player with left shoulder pain and recurrent posterior instability. He underwent 2 prior soft tissue shoulder stabilization procedures with poor functional outcomes. In clinic, his physical examination was significant for tenderness to palpation at the lateral outlet, positive apprehension test, and positive Kim and jerk tests.
Preoperative computed tomography (CT) scan shows that there was approximately 20% posterior glenoid bone loss. There were also multiple anchor sites present from his prior surgeries. We used a best fit circle method to evaluate the degree of bone loss. In this method, a circle is applied to the inferior aspect of the glenoid on an en face CT view. A line of bone loss is established by connecting the most posterior aspect of the glenoid to the closest edge of the circle. We then divide this distance by the diameter of the circle.
A magnetic resonance imaging (MRI) was also obtained, which showed attenuated tissue and medial scarring with redemonstration of the posterior chondral wear and subchondral erosive changes seen on CT scan.
Treatment indications include posterior instability with >20% to 25% posterior glenoid bone loss and recurrent posterior instability after prior stability procedure. DTA offers articular cartilage and a customizable well-contoured solution for patients with complex revision cases.
Contraindications are poorly defined but, for now, include irreparable rotator cuff tear in an older patient, uncontrolled epilepsy, and severe glenohumeral osteoarthritis.
The patient is placed in lateral decubitus with a beanbag and axillary roll. A dual suspension arm positioner was used with 10 lbs of traction applied. The degree of abduction and flexion is modified as needed for access.
Posterior superior, posterior inferior, mid glenoid, and anterior superior portals were used in this case.
An initial diagnostic arthroscopy was performed. Suture material from the patient’s previous soft tissue surgery was debrided. A glenoid rim fracture was identified and excised. Glenoid mobilization was then performed, and while there was a small amount of capsular deficiency, sufficient labral tissue was identified at the inferior most margin.
A capsulotomy was performed, and an incision was made to allow for eventual introduction of the bone block. The posterior rim of the glenoid was burred to a flat base with a bone cutter and shaver to facilitate graft placement, and the glenoid was marked to properly position the center of the graft. Abrasion chondroplasty was performed on the exposed area of glenoid rim to stimulate a healing response.
A template is inserted for assessment of sizing, congruity, and apposition to the glenoid rim.
The graft was then prepped at the back table. The bone block was harvested from the lateral aspect of the distal articular cartilage as shown in the image here. For this case, our graft was approximately 9 mm in width, 23 mm in length, and 9 mm of depth. This graft was drilled using a 6-mm offset guide. The graft was then affixed to a neutral graft insertion guide to help with introduction into the shoulder in later steps.
We then used pulsatile lavage to remove donor marrow elements, and platelet-rich plasma (PRP) or bone marrow aspirate concentrate (BMAC) selectively to encourage healing with biologic graft incorporation.
Here is our final graft.
The portal incision was then widened and a Kocher was used to dilate the soft tissue, expanding the capsule and infraspinatus muscle fibers in a proximal to distal direction. Blunt finger dissection is performed to ensure adequate room for graft passage. After the portal is expanded, 2 skids are used to transfer the bone block into position on the insertion handle.
The graft was then introduced and positioned to allow for maximal coverage of the defect. A polydioxanone (PDS) suture is used to maintain control of the graft on the insertion handle and the paddle is placed on the articular surface to ensure appropriate congruity with the intact chondral surface. Screw fixation was performed with two 3.75 titanium screws and washers from the Latarjet set.
Sutures were then passed in mattress fashion through the existing washer and tied down. Once the sutures were tied down over the graft, a side-to-side repair using sutures was performed to the posterior capsule to best reapproximate the capsule.
All potential donors permitted harvest of a standard-sized DTA, irrespective of sex or common anthropometric measures, and 85.8% showed distal tibial morphology acceptable for glenoid augmentation.
The washers are loaded with a slot for the #2 Fiberwire (Arthrex; Naples, FL) and this is then passed in a mattress fashion through the labrum and capsule. If using a rim plate, the sutures are placed under the plate. A PDS suture was then used to reinforce the capsular closure.
The graft was then visualized through glenohumeral range of motion. A secure glenoid augmentation was achieved.
Potential complications include hardware failure or screw pull-out, graft lysis, infection, disease transmission, and stiffness.
The patient should remain in an abduction sling in neutral rotation for 3 weeks postoperatively with an early focus on wrist and grip strengthening. At 4 weeks, patients can begin forward flexion to 90° and light internal and external rotation as tolerated. At 6 weeks, a light strengthening program can begin with increasing range of motion. Sports-specific rehabilitation can begin at approximately 12 weeks. Generally, patients should reach maximal benefit by 12 months postoperatively.
Surgical pearls are as follows:
It is paramount to liberate the posterior capsulolabral complex medially and inferiorly to ensure adequate mobility for bone block placement.
Adjunctive posterosuperior portals can be used to obtain a flush vertical surface at the posterior glenoid with healthy bleeding bone.
Pulsatile lavage should be used to remove all donor marrow elements that will encourage healing and limit the risk of complications.
Use the metal template to ensure appropriate preparation, congruity, and soft tissue releases.
Consider temporarily removing the bone block from the insertion handle to pass it down along its vertical access. Once into the joint, the paddle can be reconnected through the PDS suture. As needed, the incision may be extended vertically, while the muscle layers are divided horizontally to avoid iatrogenic injury to the infraspinatus.
Viewing through the anterosuperior portal, a switching stick may be placed through the anterior portal to rotate the graft or maintain “articular reduction” during graft fixation, particularly after the first screw is engaged.
Surgical pitfalls are as follows:
Inappropriate posterior portal placement (too lateral or too proximal) and inadequate capsular mobilization can limit appropriate graft placement.
Uneven, concave, or convex surfaces on the prepared glenoid may contribute to inadequate compression and potential micromotion at the graft-glenoid interface.
Overly oblique screw placement may compromise stability and is ideally suited for collinear screw position parallel with the articular surface.
To prevent graft fracture, torque failure of the screw heads, and overcompression of the graft upon final fixation, advance the screw while periodically backing it up to clear the threads with hard bone. Sequentially tighten each screw to a “two finger” tightness, which is ideal when using a rim plate to more uniformly dissipate compressive forces.
Wong et al studied 27 patients with minimum 15% anterior glenoid bone loss who underwent stabilization with DTA allograft. They found significant improvement in patient-reported outcomes, high healing rates, and no cases of recurrent instability.
Similarly, Ebnezar and Wong examined 2-year outcomes of patients undergoing DTA allograft augmentation for glenoid bone loss. They also reported improved patient-reported outcomes and no occurrences of partial or non-union.
Finally, Nacca et al created a 12-mm posterior defect in 10 cadaveric shoulders and compared the biomechanics of DTA with scapular spinal autograft. There was no significant difference in peak force between the 2 grafts.
In conclusion, arthroscopic posterior glenoid augmentation with DTA is a viable treatment option for patients with shoulder pain and instability with >20% to 25% posterior glenoid bone loss and/or following failed prior stabilization procedures.
Footnotes
Submitted July 7, 2021; accepted February 18, 2022.
One or more of the authors has declared the following potential conflict of interest or source of funding: B.R.W. received research support from Arthrex; received publishing royalties and financial support from Elsevier; is a paid consultant for FH Ortho; received stock options from Kaliber AI; is a paid presenter for Vericel; and received stock options from Vivorte. N.A.T. is a paid presenter or speaker for DJ Orthopedics. M.G. received stock or stock options from Medtronic and Stryker. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.
Funding
No external funding or support was received for this study.
