Stability Of Set Research Articles

Bone Loss of The Glenoid and Humerus: A concern for Failure in the Setting of Glenohumeral Instability

Glenohumeral instability is often characterized by progressive bipolar bone loss, a clinical phenomenon that not only complicates the management of recurrent shoulder dislocations but portends an increased risk for failure following soft-tissue stabilization procedures. This review synthesizes the history and pathophysiology of humeral and glenoid bone loss, delineates critical and subcritical thresholds, and emphasizes the necessity of a comprehensive diagnostic and surgical approach in the evaluation and treatment of patients with glenoid and/or humeral bone loss. The dynamic nature of bony injury in shoulder instability highlights the importance of tailored interventions to address bipolar bone loss and restore shoulder stability and function. Through an in-depth examination of contemporary strategies for managing glenohumeral instability, including the employment of advanced imaging techniques and refined surgical methods, this chapter offers guidance on an optimal clinical approach. By focusing on improving surgical outcomes and patient function, this review aims to navigate the complexities of shoulder instability, underscoring the importance of an integrated approach to patient care.

Humeral Head Bone Grafting of a Large Off-Track Hill-Sachs Lesion Using Femoral Condyle Osteochondral Allograft Through a Percutaneous Posterior Approach

Hill-Sachs lesions (HSLs) are commonly associated with anterior shoulder instability with or without glenoid bone defects. Treatment decision mainly depends on the size and location of the defect on the humeral head. Osteochondral allograft transplantation has been described for the treatment of large off-track HSLs. However, concerns have been raised due to concerns accessing the HSL and associated complications, predominantly due to the anterior aspect of the deltopectoral approach and subscapularis tenotomy used to gain access to these lesions. In addition, most of the studies used a lemon-wedge-shaped allograft to restore the defect, which can be technically demanding and time-consuming. This Technical Note aims to describe a posterior approach to the humeral head through an infraspinatus split that allows for accurate humeral head reconstruction with cylindrical osteochondral allografts in the setting of primary or recurrent anterior shoulder instability with large, off-track HSLs.

Posterior Glenoid Bone Grafting in the Setting of Excessive Glenoid Retroversion Does Not Provide Adequate Stability in a Cadaveric Posterior Instability Model

Background: Excessive glenoid retroversion is a known risk factor for posterior shoulder instability and failure after soft tissue stabilization procedures. Whether excessive glenoid retroversion is a risk factor for failure after posterior glenoid bone grafting is unknown. Purpose: To evaluate the biomechanical effectiveness of posterior iliac crest bone grafting (ICBG) for posterior shoulder instability with increasing glenoid retroversion. Study Design: Controlled laboratory study. Methods: Six fresh-frozen cadaveric shoulders had a posterior glenoid osteotomy allowing the glenoid retroversion to be set at 0°, 10°, and 20°. At these 3 preset angles, 4 conditions were simulated consecutively on the same specimen: (1) intact glenohumeral joint, (2) posterior Bankart lesion, (3) 20% posterior glenoid bone defect, and (4) posterior ICBG. Stability was evaluated in the jerk position (60° of glenohumeral anteflexion, 60° of internal rotation) by measuring (A) posterior humeral head (HH) translation (in mm) and (B) peak translational force (in N) necessary for translation of the HH over 25% of glenoid width. Results: At 0° of retroversion, the ICBG restored posterior HH translation and peak translational force to values comparable with those of the intact condition (P = .649 and P = .979, respectively). At 10° of retroversion, the ICBG restored the peak translational force to a value comparable with that of the intact condition (22.3 vs 24.7 N, respectively; P = .418) but showed a significant difference in posterior HH translation in comparison to the intact condition (4.5 vs 2.0 mm, respectively; P = .026). There was a significant increase in posterior HH translation and significant decrease in peak translational force with the ICBG at 20° of glenoid retroversion compared with the intact condition (posterior HH translation: 7.9 vs 2.0 mm, respectively; P < .006; peak translational force: 15.3 vs 24.7 N, respectively; P = .014). Conclusion: In this cadaveric study, posterior ICBG was able to restore stability to a level comparable to that of the native condition at 0° and to some extent at 10° of retroversion. However, posterior ICBG was not able to provide adequate stability at 20° of glenoid retroversion. Clinical Relevance: Posterior glenoid bone grafting with ICBG should be used with caution when performed in isolation in the setting of posterior instability associated with glenoid bone loss and combined glenoid retroversion of >10°.

Comparing Access to Engaging Hill-Sachs Lesions Between the Modified Posterior Deltoid Split Approach and Standard Deltopectoral Approach for Bone Grafting.

Hill-Sachs lesions are common after shoulder instability, and treatment options vary but include remplissage or implantation of structural bone graft. Large Hill-Sachs lesions not addressed by remplissage are challenging to manage and may frequently require an open surgical approach for bone filling treatment options. The optimal approach to maximize visualization of the humeral head during these procedures remains unclear. The purpose of this study was to compare the area of the humeral head accessed using a modified posterior deltoid split approach versus a standard deltopectoral approach without surgical dislocation, with particular attention to access of engaging Hill-Sachs lesions for the purpose of bone grafting in the setting of anterior shoulder instability. It was hypothesized that both approaches would provide equal access to a simulated Hill-Sachs lesion. Controlled laboratory study. Four human cadaveric shoulders were mounted in the beach-chair position. The modified posterior deltoid split approach and nonextensile deltopectoral approaches were performed. A typical Hill-Sachs lesion was simulated on the humeri. The percentage of the total surface area of the humeral head that was accessed, including access to the simulated Hill-Sachs lesion, was mapped using 3-dimensional digitizing software. The deltopectoral approach provided 45% ± 15.2% access (range, 24% to 58%) to the humeral head versus 22.2% ± 6.1% (range, 17% to 30%) for the modified posterior deltoid split approach (P = .057). The modified posterior deltoid split approach enabled 100% access of the simulated Hill-Sachs lesion compared with 0% for the nonextensile deltopectoral approach. The angle of access to the articular surface was direct and perpendicular with the modified posterior deltoid split approach. The overall surface area of the humeral head accessed via the modified posterior deltoid split approach was less compared with the deltopectoral approach; however, the entire area of a typical Hill-Sachs lesion was able to be accessed from the modified posterior deltoid split approach, whereas this area was not well visualized from the standard deltopectoral approach. The modified posterior deltoid split approach provided sufficient access to the humeral head for the purposes of grafting an engaging Hill-Sachs lesion in the setting of anterior shoulder instability.

Results of medial patellofemoral ligament reconstruction with and without tibial tubercle osteotomy in patellar instability: a systematic review and single-arm meta-analysis

PurposeTo confirm which method provides lower rate of recurrent instability and superior clinical outcomes.MethodWe searched PubMed, Embase and Web of Science for the trials involving one intervention or both for patellar instability: medial patellofemoral ligament reconstruction (MPFLR) with and without tibial tubercle osteotomy (TTO). The postoperative Kujala score, Lysholm score, Tegner scores and the rate of recurrent instability (dislocation or subluxation) were analyzed as the primary clinical outcome parameters in a random or fixed effects meta-analysis.ResultsIn total, 43 articles met inclusion criteria after full-text review. A total of 2046 patients were analyzed. The overall mean age was 20.3 years (range, 9.5–60.0 years), with a mean follow-up time of 3.2 years (range, 1–8 years). The mean Kujala scores in MPFLR and MPFLR + TTO were 89.04 and 84.44, respectively. There was significant difference in Kujala scores between MPFLR and MPFLR + TTO (MD = 4.60, 95%CI: 1.07–8.13; P = 0.01). The mean Lysholm scores in MPFLR and MPFLR + TTO were 90.59 and 88.14, respectively. There was no significant difference in Lysholm scores between MPFLR and MPFLR + TTO (MD = 2.45, 95%CI: -3.20-8.10; P = 0.40). The mean Tegner scores in MPFLR and MPFLR + TTO were 5.30 and 4.88, respectively. There was no significant difference in Tegner scores between MPFLR and MPFLR + TTO (MD = 0.42, 95%CI: -0.39-1.23; P = 0.31). At final follow-up, the rates of recurrent instability in MPFLR and MPFLR + TTO were 3% and 4%, respectively. There was no significant difference in the rates between MPFLR and MPFLR + TTO (OR = 0.99, 95%CI: 0.96–1.02; P = 0.4848).ConclusionMPFLR and MPFLR + TTO are effective and reliable treatments in the setting of patellofemoral instability. MPFLR seems to show a better performance in functional outcomes than MPFLR + TTO. Moreover, their rates of recurrent instability are very low, and no significant difference exists.

High long-term failure rates after arthroscopic Bankart repair in younger patients with recurrent shoulder dislocations: A plea for early treatment.

To determine arthroscopic Bankart repair outcomes and recurrence risk factors at a minimum 5-year follow-up. Retrospective assessment of prospectively collected data, single-cohort study of patients who underwent arthroscopic Bankart repair with a minimum 5-year follow-up. Demographical and preoperative instability features were collected. Primary outcome was recurrent instability set as dislocation or subluxation. Secondary outcomes were revision surgery, postoperative instability degree according to Manta criteria, objective and subjective clinical and functional status, assessed by the Rowe, Western Ontario Shoulder Index (WOSI) and Subjective Shoulder Value (SSV) scores. Return to sport and postoperative sports activity at the final follow-up were also recorded. One-hundred and seventy-two patients, 82% men, average age at surgery 29.5 ± 9.2 years, were included. At a mean follow-up of 8.3 ± 2.6 years, recurrent instability occurred in 53 of 172 patients (30.8%). Revision surgery was required in 23/53 (43.4%) of shoulder with recurrent instability. Recurrence occurred within the first 2 years postoperative in 49% of the shoulders, whereas 51% of recurrences occurred after this period. Recurrence took place after a traumatic event in 25% and 56%, respectively. Recurrence rates were higher in patients who underwent surgery after two or more dislocations (p = 0.029). Patients younger at the time of first dislocation, younger at surgery and those with a higher preoperative degree of instability also showed significantly higher rates of recurrence (p = 0.04, p = 0.02, p = 0.03). Postoperative ROWE, WOSI and SSV scores were significantly worse in patients with recurrent instability (p < 0.001). Return-to-sports rate was also lower in patients with postoperative recurrence (p < 0.001). The arthroscopic Bankart repair was associated with a high long-term recurrence rate, and its effectiveness decreased over time. The lowest recurrence rates in arthroscopic Bankart repair were achieved in older patients with only one prior instability episode and a lower instability degree. Level IV.

Arthroscopic Remplissage Before Bankart Repair With All-Suture Anchor Mattress Fixation in the Beach-Chair Position

A common procedure for treatment of Hill-Sachs lesions in the setting of anterior shoulder instability is arthroscopic remplissage. Remplissage consists of using the posterior capsule and infraspinatus tendon to fill the Hill-Sachs lesion and convert it into an extra-articular defect. Previous versions of this technique have not specified the timing in which remplissage and Bankart repair occur and have been performed with the patient in the lateral decubitus position. In this Technical Note, we describe our technique where we perform the remplissage before Bankart repair using all-suture anchor mattress fixation with the patient in the beach-chair position. By performing the remplissage before Bankart repair, the shoulder is reduced to allow for easier execution of the remplissage and reduce difficulties that might prevent its completion if done after Bankart repair. Further, by completing remplissage before Bankart repair in the beach-chair position, the humeral head is moved posteriorly with the cuff to allow for better access for the following labral repair and allows for the standardization between arthroscopic and open shoulder instability management.

Thermal instability in an inclined fluid layer subjected to Couette–Poiseuille flow

The present work deals with the onset of thermal instability in an inclined fluid layer subjected to Couette–Poiseuille flow. We consider the configuration in which one boundary is maintained at a constant temperature and the other boundary is imposed with a constant heat flux. The collocation method, based on Chebyshev polynomials, is used to discuss the instability of the flow with respect to the thermal Rayleigh number. It is found that there exists a value of the angle of inclination below which the instability sets in as longitudinal rolls, and the critical value of the Rayleigh number remains unaffected by superimposed Couette–Poiseuille flow. However, for angles of inclination greater than this threshold value, the critical mode of instability is transverse mode, and the critical value of the Rayleigh number is significantly affected by the superposition of Couette–Poiseuille flow. Further, the onset of instability also depends upon the Prandtl number of the fluid.

Poster 244: Magnetic Resonance Imaging versus Diagnostic Arthroscopy to Identify Intraarticular Pathology Associated with Patellar Instability: A High Rate of Discordant Findings Altering Surgical Treatment

Objectives: While uncommon, acute traumatic patellar dislocations can lead to recurrent symptoms of patellar instability in 15% to 45% of patients. Patellar stability is an interplay of bony and soft tissue restraints as well as anatomic factors, however, a mainstay of treatment remains reconstruction of the medial patellofemoral ligament (MPFL). Instability events can lead to intra-articular derangements of the knee, both in the acute and chronic patellar instability setting. These findings may not always be appropriately identified on magnetic resonance imaging (MRI). The incidence of these “surprise” injuries have not been previously reported. The purpose of this study is to determine the rates of coexisting intra-articular pathology in patients with patellar instability requiring MPFL reconstruction and elucidate any discordance between preoperative MRI findings and diagnostic arthroscopy findings. Methods: All patients undergoing MPFL reconstruction at a single institution between 2010 and 2023 were identified and preoperative MRI reports, defined as the most recent MRI report to the date of surgery with no interval traumatic events, were queried. Records without full MRI reports as read by a radiologist or cases in which a diagnostic arthroscopy was not conducted were excluded. MRI findings were discordant from arthroscopic findings if a lesion identified on diagnostic arthroscopy was not present in the full MRI report. Procedures that were undertaken because of these missed pathologies on MRI were recorded. Results: A total of 640 patients were identified during the study period, and 507 complete records were ultimately included. Preoperative MRI identified patellar osteochondral lesions or cartilage fissures in 333 patients (66%), loose bodies in 119 patients (24%), lateral femoral condyle osteochondral lesions or fissures in 97 patients (19%) and meniscus tears in 47 patients (9%). Among these patients, 172 (34%) had a diagnosis at the time of arthroscopy which was not identified on the preoperative MRI. These arthroscopic findings resulted in 75 loose body removals, 74 patellar shaving chondroplasties, 16 partial meniscectomies, 3 microfractures, 3 osteochondral lesion open reduction internal fixation, and 2 meniscal repairs which would have been missed without diagnostic arthroscopy due to discordant MRI findings. Conclusions: Over one-third of patients at a single institution who underwent diagnostic arthroscopy in the setting of patellar instability surgery had pathology identified which required surgical intervention that was not reported on a preoperative MRI. A comparison of MRI and diagnostic arthroscopy has been extensively reported on for other knee pathologies including ACL tear and lateral meniscal tear; however, there has been no similar investigation of the reliability of MRI for identification of concomitant pathology in the setting of patellar instability to date. The findings of this study highlight the importance of diagnostic arthroscopy in the treatment of patellar instability, the frequency with which this altered treatment, and the high preponderance of discordant MRI findings.

Poster 160: Preoperative MRI Underestimates Shoulder Labral Injuries Compared with Diagnostic Arthroscopy

Objectives: To compare the overall agreement in the magnitude of shoulder labral injuries between preoperative MRI and assessment at the time of diagnostic arthroscopy. Methods: A retrospective chart review was performed of patients undergoing primary arthroscopic labral repair procedures between February 2018 and February 2023. Exclusion criteria included prior ipsilateral shoulder surgery, MRI study performed at outside health system, and incomplete documentation of labral tear location. Age, gender, and dates of injury, imaging, and surgery were recorded. Radiology and operative reports were reviewed to record the location and extent of the labral tear using conventional clock-face coordinates. Tear locations were further classified as either anterior (2-6 o’clock), posterior (6-10 o’clock), or superior (10-2 o’clock). MRI studies were performed by 1.5-Tesla scanner and all radiology reports were performed by fellowship-trained musculoskeletal radiologists at a single health system. Subgroup analysis of labral tear size on radiology interpretation was performed between MRI arthrogram (MRA) and conventional MRI studies. Results: A total of 138 subjects (mean age 25.8 years, 73% male) met criteria for inclusion in this study. Of the included subjects, 105 underwent MRI arthrogram and 33 underwent conventional MRI studies. The average time from initial injury to MRI was 153.4 days and the average time from MRI to surgical intervention was 66.8 days. The average total recorded labral tear size in clock-face coordinates was significantly greater on diagnostic arthroscopy compared with the radiologist MRI interpretation (4.4 vs 3.6, p&lt;0.01). The average labral tear size in the posterior region was also significantly greater on diagnostic arthroscopy (2.4 vs 1.6, p&lt;0.01). The average labral tear size in the anterior (2.5 vs 2.2, p=0.08) and superior (1.6 vs 1.5, p=0.29) regions was greater on diagnostic arthroscopy but did not reach statistical significance. The difference in total and posterior tear size remained significant in both the arthrogram and conventional MRI subgroups. Subjects undergoing MRI arthrogram had a significantly greater reported size of anterior labral tears in clock-face coordinates compared with conventional MRI (2.7 vs 2.0, p=0.03), but did not reach significance for the posterior (p=0.40), superior (p=0.31), and the overall global labrum (p=0.29). Conclusions: MRI significantly underestimate the overall size of labral tears in setting of shoulder instability, particularly in the posterior labrum. Surgeons should account for potential underestimation of true labral injury during preoperative planning for surgical management of shoulder instability.

Effects of gravity and anisotropy on the convective instability in a nanofluid porous medium

Controlling thermal loads in heat transfer systems that produce high heat flux is a real mechanical challenge. Various cooling/heating techniques are available to achieve the reliability requirements of electronic devices. Among them, the use of nanofluids is one of the important techniques that provide long term stability, higher cooling rates, decreased pumping power needs, and cost-effectiveness. Instability in fluids typically occurs when a disturbance affects the equilibrium of forces of external, inertial, or viscous origin acting on a system. The disturbances may arise from the surroundings due to small changes in the boundary conditions, surface roughness, free stream turbulence, noise, etc. In several circumstances, these disturbances are very small and hence cannot be measured with the available instruments but can be observed after the instability sets in. In this study, we focus on examining the effect of time-periodic vertical gravity modulation on the initiation of natural convection in a porous medium saturated with a nanofluid. The porous medium is characterized by being heated at the bottom and possessing anisotropic properties in terms of permeability and thermal diffusivity. Specifically, we investigate the onset of convection in water-based nanofluids that contain metallic (Cu) and metal oxide ( A l 2 O 3 ) particles. The Khanafer-Vafai-Lightstone (KVL) nanofluid model is employed to describe the behavior of the nanofluids, and the thresholds for convective instability are determined using the Mathieu functions. In addition, we study the instabilities of synchronous and subharmonic modes and explore their transitions along with practical applications.

Risk Factors for Atraumatic Medial Patellar Facet Lesions.

Medial patellar facet lesions have been well-described in the setting of patellar instability. However, relatively little is known about risk factors for atraumatic medial patellar facet lesions. To identify clinical and radiographic risk factors for medial patellar facet lesions in patients without a history of trauma or patellar instability. It was hypothesized that a posterior tibial tubercle relative to the trochlear groove would be a risk factor for atraumatic medial patellar facet lesions. Case-control study; Level of evidence, 3. A total of 37 patients with atraumatic medial patellar facet lesions were matched by age, sex, and body mass index with 37 control patients without a history of patellofemoral dysplasia. Demographic and imaging characteristics were compared between groups. Plain radiography was used to evaluate Wiberg type, and magnetic resonance imaging was used to calculate Caton-Deschamps index, tibial tubercle-trochlear groove distance, trochlear facet asymmetry ratio, patellotrochlear index, sulcus depth, patellar bisect ratio, and tibial tubercle height. Statistically significant variables from univariate analysis were used as inputs to the multivariate regression model to assess independent risk factors. There were no differences between groups with respect to Wiberg type, Caton-Deschamps index, tibial tubercle-trochlear groove distance, sulcus depth, or patellotrochlear index (P > .05 for all). The medial facet lesion group had a larger medial trochlear facet (trochlear facet asymmetry ratio, 0.72 ± 0.11 vs 0.60 ± 0.09; P < .001), a more medial-lying patella in the trochlear groove (patellar bisect ratio, 0.57 ± 0.06 vs 0.55 ± 0.07; P = .035), and a more posterior tibial tubercle relative to the trochlear groove (tibial tubercle height, -3.13 ± 5.21 vs -0.23 ± 5.93 mm; P = .030) compared with the control group. Multivariate regression analysis identified trochlear facet asymmetry and tibial tubercle height as independent risk factors for medial patellar facet lesions (relative risk = 97.3 [95% CI, 14.9-635.1], P < .001 and relative risk = 0.95 [95% CI, 0.92-0.98], P = .004, respectively). A relatively larger medial trochlear facet and a more posterior tibial tubercle relative to the trochlear groove were found to be risk factors for medial patellar facet lesions in patients without a history of trauma or patellar instability.

Necessary and Sufficient Conditions for Event-Triggered Set Stabilizability of Markovian Jump Logical Networks.

This technical paper utilizes the Lyapunov theory to characterize the event-triggered set stabilizability of Markovian jump logical control networks (MJLCNs). Whereas the existing result for checking the set stabilizability of MJLCNs is only sufficient, this technical paper further establishes its necessary and sufficient condition. First, the Lyapunov function is established to describe the set stabilizability of MJLCNs necessarily and sufficiently by combining recurrent switching modes and desired state set. Then, the triggering condition and the input updating mechanism are designed regarding the value change of the Lyapunov function. Finally, the effectiveness of theoretical results is demonstrated by a biological example concerning the lac operon in Escherichia coli.

Stability of plane Couette flow with constant wall transpiration

Plane Couette flow with constant wall transpiration, i.e., constant blowing from below and constant suction from above, is a solution of the Navier-Stokes equations in terms of exponentials. It is characterized by two Reynolds numbers Re and ReV, where Re parametrizes the moving wall and ReV describes the influence of the transpiration. For this flow the modified Orr-Sommerfeld equation admits one of the very few exact solutions in terms of hypergeometric functions. Based on this, we solve the stability problem, though for the main part focus on temporal stability. For small wall-transpiration rates up to ReV≃6.71, the flow remains unconditionally stable, analogous to the classical Couette flow for arbitrary Reynolds numbers Re. By further increasing ReV an instability sets in and a minimum critical Reynolds number of Re=668350.491 is reached at ReV=9.799. Hence, around this point, the destabilizing effect of blowing outweighs the stabilizing effect of suction. By further increasing the transpiration rate beyond this point, the corresponding critical Reynolds number Re increases again and continues to grow. This limiting case is accompanied by the development of a strong boundary-layer-like velocity profile near the upper wall and the flow transitions to the asymptotic suction boundary layer (ASBL). Thus, the present analysis comprises the whole range from classical Couette flows extended by transpiration to the ASBL, which is known to have a strongly stabilizing effect. Published by the American Physical Society 2024

State-Feedback Set Stabilization of Boolean Networks With State-Dependent Random Impulses.

In this article, we are devoted to addressing the state-feedback set stabilization of Boolean control networks with state-dependent random impulses by utilizing a hybrid index model. By comparison with the previous impulsive Boolean networks, this model can be used to describe the instantaneousness of various impulsive behaviors more clearly. In order to avoid the occurrence of Zeno phenomenon, we first introduce the basic concept of forward completeness and further establish the judging criterion. After that, an algorithm is presented to derive the largest control invariant subset of a given subset. Based on this, we derive a necessary and sufficient criterion for finite-time feedback set stabilizability. Similarly, the result is also obtained for the asymptotic case, and the asymptotic set stabilizers are designed by dividing the whole state space into several layers. Moreover, we also investigate the relationships between different stabilizabilities. Last, two illustrative examples are presented to demonstrate the efficiency of the theoretical results.

Posterior Shoulder Instability and Glenoid Bone Loss: A Review and a Free Bone Graft Technique.

Posterior glenoid bone loss (pGBL) is frequently associated with posterior shoulder instability. Posterior glenohumeral instability accounts for a small percentage of shoulder pathologies, and critical bone loss in posterior instability has not been well defined in the literature. Younger patient populations who participate in activities that repetitively stress the posterior stabilizing structures of the shoulder are more prone to developing posterior shoulder instability. A variety of surgical options have been described, ranging from isolated capsulolabral repair to glenoid osteotomy. Soft-tissue repair alone may be an inadequate treatment in cases of pGBL and places patients at a high risk of recurrence. Our preferred technique for posterior glenoid reconstruction in cases of pGBL involves the transfer of a free iliac crest bone graft onto the native glenoid. The graft is contoured to fit the osseous defect and secured to provide an extension of the glenoid track. In this study, we review pGBL in the setting of posterior instability and describe our technique in detail. Further long-term studies are needed to refine the indications for glenoid bone graft procedures and quantify what constitutes a critical pGBL.

Arthroscopic Subdeltoid Humeroplasty in the Beach-Chair Position for Reverse Hill-Sachs Lesions

Reverse Hill-Sachs lesions (HSLs) often involve a greater percentage of the humeral head articular surface than posterior HSLs and frequently require surgical treatment in the setting of posterior shoulder instability. Multiple techniques have been described to treat these lesions depending on their size, acuity, and location. The (modified) McLaughlin procedure is widely used to treat smaller engaging lesions, whereas larger lesions involving a greater percentage of the humeral head articular surface require anatomic disimpaction, termed “humeroplasty.” Humeroplasty is traditionally performed via an open approach. This technical note describes an arthroscopic subdeltoid humeroplasty technique for the reduction and fixation of reverse HSLs in the beach-chair position.

On matched asymptotic expansion solutions of a bucklewave propagation problem

AbstractIn the present paper, the method of matched asymptotic expansions is used to derive approximate analytical solutions to a model problem related to bucklewave propagation in undersea pipelines. The model problem, introduced by Chater, Hutchinson and Neale (in: Collapse – The Buckling of Structures in Theory and Practice (Thompson, J.M.T., Hunt, G.W., eds.) Cambridge Univ. Press, Cambridge, 1983), consists of a linear elastic beam resting on a nonlinear elastic foundation, with inclusion of axial tension and inertia, related to a propagating buckle. When tension dominates over inertia, it is found that the asymptotic solution describing a propagating buckle has the character of nonoscillatory motion. When tension and inertia forces are of equal magnitude, or when inertia forces dominate over tension, the solutions are found to be oscillatory, but still localized around the bucklewave front. Finally, it is shown that when the propagation speed of the buckle exceeds a critical value, a spatial instability sets in, with exponentially growing amplitude of the beam deflection.

Current Evidence Regarding Shoulder Instability in the Paediatric and Adolescent Population

Paediatric and adolescent shoulder instability is caused by a unique combination of traumatic factors, ligamentous laxity, and pattern of muscle contractility. The multifactorial nature of its aetiology makes interpretation of the literature difficult as nomenclature is also highly variable. The purpose of this review is to summarize the existing literature and shed light on the nuances of paediatric and adolescent shoulder instability. The epidemiology, clinical features, imaging, and management of all forms of paediatric shoulder instability are presented. The main findings of this review are that structural abnormalities following a dislocation are uncommon in pre-pubertal paediatric patients. Young post-pubertal adolescents are at the highest risk of failure of non-operative management in the setting of traumatic instability with structural abnormality, and early stabilisation should be considered for these patients. Remplissage and the Latarjet procedure are safe treatment options for adolescents at high risk of recurrence, but the side-effect profile should be carefully considered. Patients who suffer from instability due to generalized ligamentous laxity benefit from a structured, long-term physiotherapy regimen, with surgery in the form of arthroscopic plication as a viable last resort. Those who suffer from a predominantly muscle patterning pathology do not benefit from surgery and require focus on regaining neuromuscular control.

Podium Presentation Title: Grooveplasty vs. Trochleoplasty for Trochlear Dysplasia in the Setting of Patellar Instability

Podium Presentation Title: Grooveplasty vs. Trochleoplasty for Trochlear Dysplasia in the Setting of Patellar Instability