Background: Glenoid bone loss (GBL) has been implicated as a risk factor for failure of arthroscopic anterior glenohumeral instability repair. Although certain amounts of GBL are associated with higher recurrence rates, there are limited studies on successes versus failures in these cohorts. Purpose: To compare the outcomes of arthroscopic Bankart repair in patients with and without GBL to determine a threshold percentage of GBL that predicts success. Study Design: Cohort study; Level of evidence, 2. Methods: All consecutive patients who underwent arthroscopic Bankart repair for anterior shoulder instability between 2004 and 2013 were prospectively enrolled. Patients with ≤25% GBL were included. Patients with no GBL were grouped and compared with those having 5% to 25% GBL. Outcomes included Single Assessment Numerical Evaluation, Western Ontario Shoulder Index, and American Shoulder and Elbow Surgeons scores, with evidence of recurrent instability. Patients with and without GBL were statistically compared with respect to outcomes and recurrence rates. Results: Of 434 eligible patients, the cases of 405 (45 female, 360 male; mean age, 27.5 years [range, 18-47 years]) were followed for a mean 61 months (range, 48-96 months). There were 189 (46.6%) with no GBL and 216 (53.3%) with GBL; the mean GBL of the latter cohort was 15% (range, 5%-25%). The mean duration of instability symptoms was 7.9 months (range, 1-21 months) and was significantly longer in the GBL group ( P < .05). The mean recurrence rate was 14.8%, which was significantly greater in patients presenting with GBL versus those with none (48/216 [22.2%] vs 12/189 [6.3%]; P < .01). Within the GBL group, GBL ≥15%, duration of symptoms >5 months, and younger age (<20 years) were independent risk factors for failure ( P < .01). Patients with any GBL had >4-times greater odds of recurrence after arthroscopic stabilization (odds ratio, 4.21; 95% CI, 2.16-8.21). Moreover, patients presenting for arthroscopic Bankart repair with GBL ≥15% had nearly 3-times greater odds of recurrent instability. Conclusion: GBL ≥15% in an active patient population portends to increased odds of recurrent instability events and inferior clinical outcomes after arthroscopic Bankart repair. Furthermore, nonmodifiable risk factors, such as age (<20 years) and duration of symptoms before presentation (>5 months), significantly affect risk of recurrence and should be key factors when counseling patients on risk of failure and determining the ideal procedure for the individual patient.

The vinyl hydroperoxide (VHP), the major isomerization product of the syn-alkyl Criegee intermediate (CI) formed in alkene ozonolysis, is a direct precursor of hydroxyl radical (OH), the most important oxidant in the troposphere. While simulations of CI reactivity have usually assumed the VHP to be a prompt and quantitative source of OH, recent quantum chemical studies have revealed subtleties in VHP reactivity such as a barrier to peroxy bond homolysis and a possible rearrangement to a hydroxycarbonyl. In this work, we use M06-L, Weizmann-1 Brueckner Doubles, and equation-of-motion spin-flip coupled-cluster theories to calculate a comprehensive reaction mechanism for the syn and anti conformers of the parent VHP formed in trans-2-butene ozonolysis and the 1-methyl VHP formed in 2,3-dimethyl-2-butene ozonolysis. We predict that for the parent VHP the anti homolysis transition structure (TS) is 3 kcal mol lower in energy than the syn TS, but for the 1-methyl system, the syn TS is 2 kcal mol lower in energy. Statistical rate theory simulations based on the quantum chemical data predict that the parent VHP preferentially decomposes to vinoxy and OH radicals under all tropospheric conditions, while the 1-methyl VHP preferentially decomposes to 1-methylvinoxy and OH radicals only close to 298 K; at 200 K, the 1-methyl VHP preferentially rearranges to hydroxyacetone. Lower temperatures and higher pressures favor the temporary accumulation of both the parent and the 1-methyl VHP.

Background: Patients with recurrent anterior glenohumeral instability after a failed Latarjet procedure remain a challenge to address. Complications related to this procedure include large amounts of bone loss, bone resorption, and issues with retained hardware that necessitate the need for revision surgery. Purpose: To determine the outcomes of patients who underwent revision surgery for a recurrent shoulder instability after a failed Latarjet procedure with fresh distal tibial allograft. Study Design: Case series; Level of evidence, 4. Methods: All consecutive patients who underwent revision of a failed Latarjet procedure with distal tibial allograft were prospectively enrolled. Patients were included if they had physical examination findings consistent with recurrent anterior shoulder instability. Patients were excluded if they had prior neurologic injury, a seizure disorder, bone graft requirements to the humeral head, or findings of multidirectional or posterior instability. History of shoulder instability was documented, including initial dislocation history, duration of instability, number of prior surgeries, examination findings, plain radiographic and computed tomography (CT) data, and arthritis graded with Samilson and Prieto (SP) classification. All patients were treated with hardware removal, capsular release with subsequent repair, and fresh distal tibial allograft to the glenoid. Outcomes before and after revision were assessed according to the American Shoulder and Elbow Score (ASES), Single Assessment Numerical Evaluation (SANE), and Western Ontario Shoulder Index (WOSI) and statistically compared. All patients underwent a CT scan of the distal tibial allograft at a minimum 4 months after surgery. Results: There were 31 patients enrolled (all males), with a mean age of 25.5 years (range, 19-38 years) and a mean follow-up time of 47 months (range, 36-60 months) after revision with distal tibial allograft. Before distal tibial allograft augmentation, the mean percentage glenoid bone loss was 30.3% (range, 25%-49%). All patients after their Latarjet stabilization had recurrent shoulder dislocation (11/31, 35.5%) or subluxation (20/31, 64.5%), and all patients had symptoms consistent with recurrent shoulder instability upon physical examination. Radiographs demonstrated 2 fixation screws in all cases, mean SP grade was 0.5 (range, 0-3), and CT scans revealed that a mean 78% of the Latarjet coracoid graft had resorbed (range, 37%-100%). Patient-reported outcome scores improved significantly pre- to postoperatively for ASES (40 to 92, P = .001), SANE (44 to 91, P = .001), and WOSI (1300 to 310, P = .001). There were no cases of recurrence, and a final CT scan of the distal tibial revision demonstrated a complete union at the glenoid–distal tibial allograft interface in 92% of patients. Conclusion: The majority of the failed Latarjet procedures included in this study had near-complete resorption of the coracoid graft and hardware complications. At a minimum follow-up time of 36 months, patients who underwent revision treatment for a failed Latarjet procedure with a fresh distal tibial allograft demonstrated excellent clinical outcomes and near-complete osseous union at the glenoid-allograft interface. Although patients evaluated with recurrent anterior shoulder instability after a failed Latarjet procedure remain a challenge to address, fresh distal tibial allograft augmentation is a viable and highly effective revision procedure to treat this patient population.

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