Anterior Glenoid Reconstruction With Distal Tibial Allograft: Biomechanical Impact of Fixation and Presence of a Retained Lateral Cortex

Background: Glenoid reconstruction with distal tibial allograft (DTA) is a known surgical option for treating recurrent glenohumeral instability with anterior glenoid bone loss; however, biomechanical analysis has yet to determine how graft variability and fixation options alter the torque of screw insertion and load to failure. Hypothesis: It was hypothesized that retention of the lateral cortex of the DTA graft and the presence of a washer with the screw will significantly increase the maximum screw placement torque as well as the load to failure. Study Design: Controlled laboratory study. Methods: Whole, fresh distal tibias were used to harvest 28 DTA grafts, half of which had the lateral cortex removed and half of which had the lateral cortex intact. The grafts were secured to polyurethane solid foam blocks with a 2-mm epoxy laminate to simulate a glenoid with an intact posterior glenoid cortex. Grafts underwent fixation with 4.0-mm cannulated drills, and screws and washers were used for half of each group of grafts while screws alone were used for the other half, creating 4 equal groups of 7 samples each. A digital torque-measuring screwdriver recorded peak torque for screw insertion. Constructs were then tested in compression with a uniaxial materials testing system and loaded in displacement control at 100 mm/min until at least 3 mm of displacement occurred. Ultimate load was defined as the load sustained at clinical failure. Results: The use of a washer significantly improved the ultimate torque that could be applied to the screws (+cortex and +washer = 12.42 N·m [SE, 0.82]; –cortex and +washer = 10.54 N·m [SE, 0.59]) ( P < .0001), whereas the presence of the native bone cortex did not have a significant effect (+cortex and –washer = 7.83 N·m [SE, 0.40]; –cortex and –washer = 8.03 N·m [SE, 0.56]) ( P = .181). Conclusion: In a hybrid construct of fresh cadaveric DTA grafts secured to a foam block glenoid model, the addition of washers was more effective than the retention of the lateral distal tibial cortex for both load to failure and peak torque during screw insertion. Clinical Relevance: This biomechanical study is relevant to the surgeon when choosing a graft and selecting fixation options during glenoid reconstruction with a DTA graft.

Open Posterior Glenoid Reconstruction Using a Distal Tibial Allograft

Background: Posterior instability is less common than anterior instability but can be seen in contact athletes and posttraumatically. Distal tibial allograft reconstruction for glenoid bone loss was first described by Provencher and colleagues in 2009 and an arthroscopic technique for posterior glenoid reconstruction using a distal tibial allograft was later described by Gupta et al in 2013. Indications: The primary indications for posterior distal tibial allograft include the failure of conservative management, recurrent instability after an arthroscopic stabilization, or glenoid bone loss > 20% to 25%. Technique Description: The patient is positioned in lateral decubitus, and examination under anesthesia is performed. Following arthroscopic evaluation, an incision is made medial to the posterolateral aspect of the acromion at the glenohumeral joint level. Electrocautery is carried to the deltoid, which is split in line with its fibers. A split between the infraspinatus and teres minor is performed. Vertical capsulotomy is performed, and deep retractors are placed. Attention is turned to the back table for graft preparation. The graft is measured, marked on the lateral aspect of the articular surface, and cut accordingly. Two 3.5-mm holes are drilled 1 cm apart, and the graft is thoroughly irrigated before being placed into the wound. A 2.5-mm drill is used in the 3.5-mm holes, and two 3.5-mm solid fully threaded screws are placed under power and tightened by hand. The wound is closed in the traditional fashion. Results: Graft nonunion and/or resorption are the primary concerns following posterior distal tibial allograft. Amar et al found no cases of nonunion or partial unions on 6-month computerized tomography (CT) scan, most patients having no or <50% resorption. Millet et al also found bony union by CT scan and improved patient-reported outcome measures. A case series by Gilat et al found 90% of patients reported restoration of stability. Discussion/Conclusion: Posterior distal tibial allograft is a successful surgical intervention for patients with recurrent posterior shoulder instability with glenoid bone loss.

Clinical Outcomes of Primary versus Revision Surgery using Arthroscopic Anatomic Glenoid Reconstruction for Anterior Shoulder Instability. (244)

Objectives: Revision surgeries after prior shoulder stabilization are known to have worse outcomes as compared to their primary counterparts. To date, no studies have looked at the utility of arthroscopic anatomic glenoid reconstruction (AAGR) as a revision surgery. The purpose of this study was to assess the clinical outcomes of primary versus revision AAGR for anterior shoulder instability with bone loss. Methods: We performed a retrospective review on consecutive patients with prospectively collected data who underwent AAGR from 2012 to 2018. Patients who received AAGR for anterior shoulder instability with bone loss and had a minimum follow-up of two years were included. Exclusion criteria included patients with rotator cuff pathology, multidirectional instability and glenoid fractures. There were 68 patients (48 primary and 20 revision) who met inclusion/exclusion criteria. Our primary outcome was measured using the Western Ontario Shoulder Instability Index (WOSI) and Disabilities of Arm, Shoulder, Hand (DASH) scores. Secondary outcomes included post-operative complications and post-operative recurrent instability. Results: The primary group showed a significant improvement in most-recent post-operative WOSI from 62.7 to 20.7 (P<0.001, α=0.05) and in DASH from 26.89 to 6.7 (p<0.001, α=0.05). The revision group also showed a significant improvement in WOSI from 71.5 to 34.6 (p<0.001, α=0.05) and in DASH from 39.5 to 17.0 (p<0.05, α=0.05). When comparing between groups, the revision group had worse WOSI scores (34.6) at most recent follow-up compared to the primary group (20.7); p<0.05. The most-recent DASH scores also showed the revision group (17.0) having worse outcomes than the primary group (6.7); p<0.05. Important to note that the minimal clinically important difference (MCID) was met for WOSI (MCID=10.4) but not DASH (MCID=10.83). There were no post-operative reports of instability in either group. For complications, one hardware failure (suture anchor) was seen in the primary group, and two hardware removals were seen in the revision group. Conclusions: While patient reported scores indicated worse outcomes in the revision group, the significant clinical improvement in DASH and WOSI, along with the lack of recurrent instability provides evidence that AAGR is a suitable option for revision patients.

Arthroscopic Distal Tibial Allograft for Posterior Glenoid Reconstruction

Background: Posterior glenoid bone loss occurs in more than two-thirds of patients with posterior glenohumeral instability, with 14% to 22% having greater than subcritical bone loss (13.5%), a marker for potential need for bony augmentation versus soft tissue-only procedures. Several techniques are described to augment either the version or volume of the glenoid surface including osteotomies, autograft transfers, and allograft tibia transfers. Indications: Arthroscopic-assisted allograft distal tibia bone block augmentation to the posterior glenoid is indicated for revision posterior instability procedures with posterior bone loss and in primary cases of posterior instability with critical bone loss. Technique Description: Arthroscopic posterior glenoid reconstruction with allograft distal tibia and posterior labral repair in the lateral position is presented. This technique uses standard instrument sets and requires no patient repositioning. The preplanned tibial bone block is prepared on a back table either prior to, or concurrently with, arthroscopic procedure. After creation of high posterior portal and standard anterior portal, a sucker-shaver and burr are used to create a perpendicular edge for apposition of the allograft tibia. The bone block is introduced through a longitudinal incision and underdelivered to the prepared surface under the liberated labrum. The articular surface of the graft and glenoid are aligned and cannulated screws are used to compress the bone block against the native glenoid. The posterior labral tissue is then mobilized over the graft and repaired to the native glenoid. Results: Arthroscopic distal tibial allograft augmentation for posterior bone loss restored stability and function in a small cohort of patients. Patients reported improved stability in the immediate postoperative course, with restoration of motion by 2 months. Push-ups, pull-ups, and return to full active duty without restrictions is allowed at 6 months postoperatively. Imaging at 3 months postoperatively has shown excellent graft healing. Discussion: The benefits of allograft tibia augmentation for posterior instability with glenoid bone loss include an anatomic joint surface restoration including articular cartilage, lack of donor site morbidity, and a minimally invasive approach. When performed arthroscopically, this technique permits concurrent posterior labral repair and anatomic reconstruction.