The Kouvalchouk Procedure versus Distal Tibial Allograft for Treatment of Posterior Shoulder Instability: The Deltoid "Hammock" Effect Exists.

BACKGROUND: In 1993, Kouvalchouk described an acromial bone block with a pedicled deltoid flap for the treatment of posterior shoulder instability. This procedure provides a "double blocking" effect in that the acromial autograft restores posterior glenoid bone loss and the deltoid flap functions as a muscular "hammock" resembling the sling effect of the conjoint in the Latarjet procedure. The primary aim of this study was to compare the Kouvalchouk procedure to distal tibial allograft (DTA) reconstruction for the management of posterior shoulder instability with associated bone loss, while the secondary aim was to evaluate the deltoid hammock effect. s METHODS: Ten upper extremity cadavers were evaluated using a validated shoulder testing apparatus in 0° and 60° of glenohumeral abduction in the scapular plane. Testing was first performed on the normal shoulder state and was followed by the creation of a 20% posterior glenoid defect. Subsequently, the Kouvalchouk and DTA procedures were conducted. Forces of 0N, 5N, 10N and 15N were applied to the posterior deltoid tendinous insertion on the Kouvalchouk graft along the physiological muscle line-of-action to evaluate the 'hammock" effect of this procedure. Testing was additionally performed on the Kouvalchouk bone graft with the deltoid muscle sectioned from its bony attachment. For all test states, a posteriorly directed force was applied to the humeral head perpendicular to the direction of the glenoid bone defect, with the associated translation quantified using an optical tracking system. The outcome variable was posterior translation of the humeral head at an applied force magnitude of 30N. RESULTS: The Kouvalchouk procedure with the loaded deltoid flap (10N: P=0.039 and 15N: P<0.001) was significantly better at reducing posterior humeral head translation than the DTA. Overall, increased glenohumeral stability was observed with increased force applied to the posterior deltoid flap in the Kouvalchouk procedure. The 15N Kouvalchouk was most effective at preventing posterior humeral translation, and the difference was statistically significant compared with the 20% glenoid defect (P=0.003), detached Kouvalchouk (P<0.001), and 0N Kouvalchouk (P<0.001). The 15N Kouvalchouk procedure restored posterior shoulder joint stability to near normal levels, such that it was not significantly different from the intact state (P=0.203). CONCLUSIONS: The Kouvalchouk procedure with load applied to the deltoid was found to be biomechanically superior to the DTA for the management of posterior shoulder instability with associated bone loss. Additionally, the results confirmed the presence and effectiveness of the deltoid "hammock" effect.

A Retrospective Study of Risk Factors and Outcomes in the Surgical Management of Slipped Capital Femoral Epiphysis.

PURPOSE: Slipped capital femoral epiphysis is commonly treated with in situ pinning (ISP) and more recently the modified Dunn procedure (MDP). This study retrospectively examines the preoperative risk factors and postoperative complications of patients treated with either ISP or MDP over a 12-year period. METHODS: A single-center, retrospective review was conducted on patients diagnosed and surgically treated with slipped capital femoral epiphysis from 2004 to 2016. Patients must have had preoperative imaging and a minimum of 6 months of clinical follow-up. Six preoperative demographic data (age, sex, intensity of symptoms, stability, trauma, and severity of slip), surgical details, and treatment outcomes were collected. Descriptive statistics were used to identify pertinent preoperative risk factors and postoperative complications in each treatment group. RESULTS: A total of 129 hips in 98 patients were treated (118 with ISP and 11 with MDP). Complications developed in 12 hips. Six hips developed osteonecrosis, two hips developed osteonecrosis and chondrolysis, two hips developed osteonecrosis and slip progression, and two hips developed slip progression only. Four of the 11 hips (36.4%) treated with MDP developed complications; 8 of the 118 hips (6.8%) treated with ISP developed complications. DISCUSSION: Complications developed in 9.3% of hips treated with ISP or MDP, with a higher rate of complications observed in the MDP group compared with the ISP group. This study is limited by the small sample size of the cohort and the disproportion in the number of cases in each treatment group. A multicenter study with larger sample sizes will be required to confirm these findings.

Biomechanical comparison of 3 types of transdiscal fixation implants for fixing high-grade L5/S1 spine spondylolisthesis.

BACKGROUND CONTEXT: There are several options for the stabilization of high-grade lumbosacral spondylolisthesis including transdiscal screws, the Bohlman technique (transdiscal fibular strut) and the modified Bohlman technique (transdiscal titanium mesh cage). The choice of an optimum construct remains controversial; therefore, we endeavoured to study and compare the biomechanical performance of these 3 techniques. PURPOSE: The aim of this study was to compare 3 types of transdiscal fixation biomechanically in an in vitro porcine lumbar-sacral spine model. STUDY DESIGN/SETTING: Porcine cadaveric biomechanical study. METHODS: 18 complete lumbar-sacral porcine spines were split into 3 repair groups, transdiscal screws (TS), Bohlman technique, and a modified Bohlman technique (MBT). Range of motion (L3 - S1) was measured in an intact and repaired state for flexion, extension, left/right lateral bending, and left/right torsion. To recreate a high-grade lumbosacral spondylolisthesis a bilateral L5/S1 facetectomy, removing the intervertebral disc completely, and the L5 body was displaced 50%-60% over the sacral promontory. Results were analyzed and compared to intact baseline measurements. Standard quasi-static moments (5 Nm) were applied in all modes. RESULTS: All range of motion (ROM) were in reference to intact baseline values. TS had the lowest ROM in all modes (p=.006-.495). Statistical difference was found only in extension for TS vs. BT (p=.011) and TS vs. MBT (p=.014). No bone or implant failures occurred. CONCLUSION: TS provided the lowest ROM in all modes of loading compared to Bohlman technique and MBT. Our study indicates that TS results in the most biomechanically stable construct. CLINICAL SIGNIFICANCE: Knowledge of the biomechanical attributes of various constructs could aid physicians in choosing a surgical construct for their patients.

Characterization of Aß aggregation mechanism probed by congo red.

ß-Amyloid peptide (1) (Aß) aggregates are toxic to neuron and the main cause of Alzheimer's disease (AD). The role of congo red (CR) on Aß aggregation is controversial in aqueous solution. Both prevention and promotion of Aß aggregation have been proposed, suggesting that CR may interact with Aß of different structural conformations resulting in different effects on Aß aggregation behavior. CR with these characteristics can be applied to probe the molecular mechanism of Aß aggregation. Therefore, in the present study, we used CR as a probe to study the Aß aggregation behavior in sodium dodecyl sulfate (SDS) condition. Our results show that Aß(40) adopts two short helices at Q15-S26 and K28-L34 in the SDS environment. CR can interact with the helical form of Aß(40), and the main interaction site is located at the first helical and hydrophobic core region, residues 17-25, which is assigned as a discordant helix region. Furthermore, CR may prevent Aß(40) undergoing α-helix to ß-strand conversion, and therefore aggregation through stabilizing the helical conformation of discordant helix in SDS environment, suggesting that the discordant helix plays a key role on the conformational stabilization of Aß. Our present study implies that any factors or molecules that can stabilize the discordant helical conformation may also prevent the Aß aggregation in membrane associated state. This leads to a new therapeutic strategy for the development of lead compounds to AD.