Characteristics of functional shoulder instability Moroder, Philipp; Danzinger, Victor; Maziak, Nina ...
Journal of shoulder and elbow surgery,
January 2020, 2020-Jan, 2020-01-00, 20200101, Volume:
29, Issue:
1
Journal Article
Peer reviewed
Open access
Pathologic activation pattern of muscles can cause shoulder instability. We propose to call this pathology functional shoulder instability (FSI). The purpose of this prospective study was to provide ...an in-detail description of the characteristics of FSI.
In the year 2017, a total of 36 consecutive cases of FSI presenting to our outpatient clinic were prospectively collected. Diagnostic investigation included a pathology-specific questionnaire, standardized clinical scores, clinical examination, psychological evaluation, video and dynamic fluoroscopy documentation of the instability mechanism, as well as magnetic resonance imaging (MRI). In a final reviewing process, the material from all collected cases was evaluated and, according to the observed pattern, different subtypes of FSI were determined and compared.
Based on the pathomechanism, positional FSI (78%) was distinguished from nonpositional FSI (22%). Controllable positional FSI was observed in 6% of all cases and noncontrollable positional FSI in 72%, whereas controllable and noncontrollable nonpositional FSI were each detected in 11% of the cases. The different subtypes of FSI showed significant differences in all clinical scores (Western Ontario Shoulder Instability Index: P = .002, Rowe Score: P = .001, Subjective Shoulder Value: P = .001) and regarding functional impairment (shoulder stability: P < .001, daily activities: P = .001, sports activities: P < .001). Seventy-eight percent had posterior, 17% anterior, and 6% multidirectional instability. Although several patients showed constitutional glenoid shape alterations or soft tissue hyperlaxity, only few patients with acquired minor structural defects were observed.
FSI can be classified into 4 subtypes based on pathomechanism and volitional control. Depending on the subtype, patients show different degrees of functional impairment. The majority of patients suffer from unidirectional posterior FSI.
Thermal effects in the ionospheric plasma instabilities including the Farley‐Buneman instability (FBI), the gradient‐drift instability (GDI), and the ion‐thermal instability (ITI) are analyzed, ...focusing on analytic analysis of the previously obtained general expression of the combined instability growth rate. It is shown that thermal effects lead to generally nonmonotonic behavior of the growth rate with the background electric field E0 or, equivalently with the plasma drift speed VE=E0/B, in contrast with the conventional quadratic (FBI) or linear (GDI) dependence. The threshold electric field for FBI is demonstrated to exist at all altitudes, although at higher altitudes and/or at longer wavelength the threshold fields become too high to be observed in the ionosphere. The GDI growth rate is shown to be significantly modified by the thermal effects at long wavelengths. In the absence of thermal effects, the growth rate is proportional to a cosine of the flow angle, the angle between the differential plasma drift and the wavevector. Thermal effects result in an additional phase shift that maximizes at an altitude around 120 km, using representative high‐latitude ionospheric parameters, and in an increase in the proportionality coefficient by up to a factor of 2. The study highlights the usefulness of an analytic treatment for revealing additional insights into the instability behavior in the broad range of ionospheric parameters that may remain hidden using only numerical treatment.
Key Points
Thermal effects lead to generally nonmonotonic behavior of the plasma instability growth rate with the background electric field
Weaker gradients are required to destabilize plasma through the gradient‐drift instability (GDI) as compared with the isothermal case
The GDI growth rate at long wavelengths is up to 2 times larger and has different directional dependencies than in the isothermal case
A ring‐like proton velocity distribution with ∂fp(v⊥)/∂v⊥>0 and which is sufficiently anisotropic can excite two distinct types of growing modes in the inner magnetosphere: ion Bernstein ...instabilities with multiple ion cyclotron harmonics and quasi‐perpendicular propagation and an Alfvén‐cyclotron instability at frequencies below the proton cyclotron frequency and quasi‐parallel propagation. Recent particle‐in‐cell simulations have demonstrated that even if the maximum linear growth rate of the latter instability is smaller than the corresponding growth of the former instability, the saturation levels of the fluctuating magnetic fields can be greater for the Alfvén‐cyclotron instability than for the ion Bernstein instabilities. In this study, linear dispersion theory and two‐dimensional particle‐in‐cell simulations are used to examine scalings of the linear growth rate and saturation level of the two types of growing modes as functions of the temperature anisotropy T⊥/T|| for a general ring‐like proton distribution with a fixed ring speed of 2vA, where vA is the Alfvén speed. For the proton distribution parameters chosen, the maximum linear theory growth rate of the Alfvén‐cyclotron waves is smaller than that of the fastest‐growing Bernstein mode for the wide range of anisotropies (1≤T⊥/T||≤7) considered here. Yet the corresponding particle‐in‐cell simulations yield a higher saturation level of the fluctuating magnetic fields for the Alfvén‐cyclotron instability than for the Bernstein modes as long as
T⊥/T||≳3. Since fast magnetosonic waves with ion Bernstein instability properties observed in the magnetosphere are often not accompanied by electromagnetic ion cyclotron waves, the results of the present study indicate that the ring‐like proton distributions responsible for the excitation of these fast magnetosonic waves should not be very anisotropic.
Key Points
Alfven‐cyclotron and ion Bernstein instabilities driven by a proton shell velocity distribution
The maximum linear growth of Alfven‐cyclotron waves is smaller than that of Bernstein modes
Yet the Alfven‐cyclotron waves can saturate at a larger level even with a moderate anisotropy
Posterior Instability of the Shoulder DeLong, Jeffrey M.; Jiang, Kevin; Bradley, James P.
The American journal of sports medicine,
07/2015, Volume:
43, Issue:
7
Journal Article
Peer reviewed
Background:
To date, there are no reports in the literature of a systematic review and meta-analysis for posterior instability of the shoulder.
Purpose:
The primary objective was to systematically ...capture, critically evaluate, and perform a meta-analysis of all available literature on arthroscopic clinical outcomes to provide insight and clinical recommendations for unilateral posterior shoulder instability. The secondary objective was to use the same means to assess clinical outcome literature for open treatment, of which a subset of highly reported outcome measures were used to determine superiority of arthroscopic versus open procedures for unilateral posterior shoulder.
Study Design:
Systematic review, meta-analysis.
Methods:
A systematic search to obtain every available, published, level of evidence study reporting patient data for unidirectional posterior shoulder instability was performed by use of the Cochrane Database of Systematic Reviews, PubMed/Medline database, manual searches of high impact factor journals and conference proceedings, and secondary references appraised for studies meeting inclusion criteria.
Results:
The systematic search captured a total of 1035 publications. After initial exclusion criteria were applied, 607 abstracts were assessed for eligibility. Full-text articles were obtained for 324 articles, and a total of 53 unique publications (27 arthroscopic studies, 26 open studies) reporting clinical outcomes for unidirectional posterior shoulder instability met inclusion criteria and were included in the systematic review and meta-analysis.
Conclusion:
Well-defined and uniform shoulder outcome measures to assess posterior shoulder instability are lacking throughout the literature. However, arthroscopic procedures are shown to be an effective and reliable treatment for unidirectional posterior glenohumeral instability with respect to outcome scores, patient satisfaction, and return to play. Despite similar results of outcome measures to the overall athletic population, throwing athletes are less likely to return to their preinjury levels of sport compared with contact athletes or the overall athletic population. Evidence also indicates that arthroscopic stabilization procedures using suture anchors result in fewer recurrences and revisions than anchorless repairs in young adults engaging in highly demanding physical activity. Furthermore, the literature suggests that patients treated arthroscopically have superior outcomes compared with patients who undergo open procedures with respect to stability, recurrence of instability, patient satisfaction, return to sport, and return to previous level of play.
Purpose
The purpose of this study was to clinically validate the Hill–Sachs interval to glenoid track width ratio (H/G ratio) compared with the instability severity index (ISI) score for predicting ...an increased risk of recurrent instability after arthroscopic Bankart repair.
Methods
A retrospective evaluation was performed using data from patients with anteroinferior shoulder instability who underwent arthroscopic Bankart repair with a follow-up period of at least 24 months. A receiver operating characteristic (ROC) curve was used to determine the optimal cut-off values for the H/G ratio and the ISI score to predict an increased risk of recurrent instability. The area under the ROC curve (AUC) of the two methods and the sensitivity and specificity of their optimal cut-off values were compared.
Results
A total of 222 patients were included, among whom 31 (14.0%) experienced recurrent instability during the follow-up period. The optimal cut-off values for predicting an increased risk of recurrent instability were an H/G ratio of ≥ 0.7 and ISI score of ≥ 4. There were no significant differences between the AUC of the two methods (H/G ratio AUC = 0.821, standard error = 0.035 and ISI score AUC = 0.792, standard error = 0.04; n.s.) nor between the sensitivity and specificity of the optimal cut-off values (n.s. and n.s., respectively).
Conclusions
The H/G ratio is comparable to the ISI score for predicting an increased risk of recurrent instability after arthroscopic Bankart repair. Surgeons are recommended to consider other strategies to treat anterior shoulder instability if H/G ratio is ≥ 0.7.
Level of evidence
III.
A general dispersion relation is derived that integrates the Farley‐Buneman, gradient‐drift, and current‐convective plasma instabilities (FBI, GDI, and CCI) within the same formalism for an arbitrary ...altitude, wave propagation vector, and background density gradient. The limiting cases of the FBI/GDI in the E region for nearly field‐aligned irregularities, GDI/CCI in the main F region at long wavelengths, and GDI at high altitudes are successfully recovered using analytic analysis. Numerical solutions are found for more general representative cases spanning the entire ionosphere. It is demonstrated that the results are consistent with those obtained using a general FBI/GDI/CCI theory developed previously at and near E region altitudes under most conditions. The most significant differences are obtained for strong gradients (scale lengths of 100 m) at high altitudes such as those that may occur during highly structured soft particle precipitation events. It is shown that the strong gradient case is dominated by inertial effects and, for some scales, surprisingly strong additional damping due to higher‐order gradient terms. The growth rate behavior is examined with a particular focus on the range of wave propagations with positive growth (instability cone) and its transitions between altitudinal regions. It is shown that these transitions are largely controlled by the plasma density gradients even when FBI is operational.
Key Points
General dispersion relation is derived that integrates fundamental electrostatic instability modes
Critical role of sharp gradients and inertial effects at high altitudes is demonstrated
Plasma gradient vector controls altitudinal transitions even when convection electric fields are strong
DNA is strictly compartmentalized within the nucleus to prevent autoimmunity; despite this, cyclic GMP-AMP synthase (cGAS), a cytosolic sensor of double-stranded DNA, is activated in autoinflammatory ...disorders and by DNA damage. Precisely how cellular DNA gains access to the cytoplasm remains to be determined. Here, we report that cGAS localizes to micronuclei arising from genome instability in a mouse model of monogenic autoinflammation, after exogenous DNA damage and spontaneously in human cancer cells. Such micronuclei occur after mis-segregation of DNA during cell division and consist of chromatin surrounded by its own nuclear membrane. Breakdown of the micronuclear envelope, a process associated with chromothripsis, leads to rapid accumulation of cGAS, providing a mechanism by which self-DNA becomes exposed to the cytosol. cGAS is activated by chromatin, and consistent with a mitotic origin, micronuclei formation and the proinflammatory response following DNA damage are cell-cycle dependent. By combining live-cell laser microdissection with single cell transcriptomics, we establish that interferon-stimulated gene expression is induced in micronucleated cells. We therefore conclude that micronuclei represent an important source of immunostimulatory DNA. As micronuclei formed from lagging chromosomes also activate this pathway, recognition of micronuclei by cGAS may act as a cell-intrinsic immune surveillance mechanism that detects a range of neoplasia-inducing processes.
Purpose
The purpose of this study is to propose recommendations for the treatment of patients with chronic lateral ankle instability (CAI) based on expert opinions.
Methods
A questionnaire was sent ...to 32 orthopaedic surgeons with clinical and scientific experience in the treatment of CAI. The questions were related to preoperative imaging, indications and timing of surgery, technical choices, and the influence of patient-related aspects.
Results
Thirty of the 32 invited surgeons (94%) responded. Consensus was found on several aspects of treatment. Preoperative MRI was routinely recommended. Surgery was considered in patients with functional ankle instability after 3–6 months of non-surgical treatment. Ligament repair is still the treatment of choice in patients with mechanical instability; however, in patients with generalized laxity or poor ligament quality, lateral ligament reconstruction (with grafting) of both the ATFL and CFL should be considered.
Conclusions
Most surgeons request an MRI during the preoperative planning. There is a trend towards earlier surgical treatment (after failure of non-surgical treatment) in patients with mechanical ligament laxity (compared with functional instability) and in high-level athletes. This study proposes an assessment and a treatment algorithm that may be used as a recommendation in the treatment of patients with CAI.
Level of evidence
V.
Background:
Anterior and posterior shoulder instabilities are entirely different entities. The presenting complaints and symptoms vastly differ between patients with these 2 conditions, and a clear ...understanding of these differences can help guide effective treatment.
Purpose:
To compare a matched cohort of patients with anterior and posterior instability to clearly outline the differences in the initial presenting history and overall outcomes after arthroscopic stabilization.
Study Design:
Cohort study; Level of evidence, 2.
Methods:
Consecutive patients with either anterior or posterior glenohumeral instability were prospectively enrolled; patients were excluded if they had more than 10% anterior or posterior glenoid bone loss, multidirectional instability, neurologic injury, or prior surgery. Patients were assigned to anterior or posterior shoulder instability groups based on the history and clinical examination documenting the primary direction of instability, with imaging findings to confirm a labral tear associated with the specific direction of instability. Preoperative demographic data, injury history, and overall clinical outcome scores (American Shoulder and Elbow Surgeons ASES, Single Assessment Numeric Evaluation SANE, and Western Ontario Shoulder Index WOSI) were assessed and compared statistically between the 2 cohorts. Patients were indicated for surgery if they elected to proceed with surgical management or did not respond to a course of nonoperative management.
Results:
The study included 103 patients who underwent anterior stabilization (mean age, 23.5 years; range, 18-36 years) and 97 patients who underwent posterior stabilization (mean age, 24.5 years; range, 18-36 years). The mean follow-up was 39.7 months (range, 24-65 months), and there were no age or sex differences between the groups. No patients were lost to follow-up. The primary mechanism of injury in the anterior cohort was a formal dislocation event (82.5% 85/103, of which 46% 39/85 required reduction by a medical provider), followed by shoulder subluxation (12%, 12/103), and “other” (6%, 6/103; no forceful injury). No primary identifiable mechanism of injury was found in the posterior cohort for 78% (75/97) of patients; lifting and pressing (11%, 11/97) and contact injuries (10% all football blocking, 10/97) were the common mechanisms that initiated symptoms. Only 10 patients (10.3%) in the posterior cohort sustained a dislocation. The most common complaints for patients with anterior instability were joint instability (80%) and pain with activities (32%). In the posterior cohort, the most common complaint was pain (90.7%); only 13.4% in this cohort reported instability as the primary complaint. Clinical outcomes after arthroscopic stabilization were significantly improved in both groups, but the anterior cohort had significantly better outcomes in all scores measured: ASES (preoperative: anterior 58.0, posterior 60.0; postoperative: anterior 94.2 vs posterior 87.7, P < .005), SANE (preoperative: anterior 50.0, posterior 60.0; postoperative: anterior 92.9 vs posterior 84.9, P < .005), and WOSI (preoperative: anterior 55.95, posterior 60.95; postoperative: anterior 92% of normal vs posterior 84%, P < .005).
Conclusion:
This study outlines clear distinctions between anterior and posterior shoulder instability in terms of presentation and clinical findings. Patients with anterior instability present primarily with an identifiable mechanism of injury and complaints of instability, whereas most patients with classic posterior instability have no identifiable mechanism of injury and their primary symptom is pain. Anterior instability outcomes in this matched cohort were superior in all domains versus posterior instability after arthroscopic stabilization, which further highlights the differences between anterior and posterior instability.
Background:
Trochlear dysplasia is a well-described risk factor for patellofemoral instability. Despite its clear association with the incidence of patellar instability, it is unclear whether the ...presence of high-grade trochlear dysplasia influences clinical outcome after patellofemoral stabilization.
Purpose:
To determine whether isolated proximal soft tissue stabilization for patellofemoral instability is as successful in patients with high-grade dysplasia compared with low-grade or no dysplasia, as measured by disease-specific quality-of-life and pain scores.
Study Design:
Case series; Level of evidence, 4.
Methods:
A total of 277 patellofemoral stabilization procedures were performed during the study period. An isolated stabilization was performed in 233 patients, and 203 of these patients (87%) had adequate lateral radiographs and complete Banff Patella Instability Instrument (BPII) scores available for assessment. Of these, 152 patients underwent a medial patellofemoral ligament reconstruction (MPFL-R) and 51 patients received a medial patellofemoral ligament imbrication (MPFL-I). There were 21 patients with no trochlear dysplasia, 89 patients with low-grade dysplasia (Dejour type A), and 93 patients with high-grade dysplasia (Dejour types B-D). An independent-samples t test was used to determine the difference between the pre- and postoperative BPII scores. A Spearman rho correlation was calculated between 3 trochlear dysplasia groups and the BPII scores at a mean 24 months after patellofemoral stabilization. An independent-samples t test was used to assess the influence of trochlear bump size on outcomes by stratifying data and assessing for a relationship to BPII scores.
Results:
The independent-samples t test demonstrated statistically significant improvements in pre- to postoperative BPII scores for both groups. The MPFL-R group improved from a mean BPII score of 24.36 to 65.16 (P < .001), and the MPFL-I group improved from a mean of 28.92 to 73.45 (P < .01). For the MPFL-R patient cohort, the Spearman rho correlation demonstrated a significant relationship between postoperative BPII scores and presence of a trochlear bump and degree of dysplasia (P ≤ .05). Overall, a trochlear bump of ≥5 mm was associated with lower postoperative BPII scores (t(193) = 2.65, η2 = 0.04).
Conclusion:
This research has established a statistically significant correlation between trochlear dysplasia and disease-specific outcomes after MPFL-R surgery. Overall, there was evidence of significant improvement in disease-specific quality-of-life scores after patellofemoral stabilization surgery. This study is the largest cohort reported to date and therefore adds substantially to the evidence that trochlear dysplasia is a significant risk factor for and predictor of outcome among patients with patellofemoral instability.
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