Multidirectional instability of the shoulder: biomechanics, clinical presentation, and treatment strategies.

Multidirectional instability (MDI) of the shoulder is a condition where the dislocation occurs in more than one direction with minimal or no causative trauma. Its pathoanatomy is complex and characterized by a redundant capsule, resulting in increased glenohumeral joint volume. The fact that several further factors may contribute to symptom onset complicates the diagnosis and hampers the identification of a therapeutic approach suitable for all cases. There is general agreement that the initial treatment should be conservative and that surgery should be reserved for patients who have not responded to an ad hoc rehabilitation program. We review the biomechanics, clinical presentation, and treatment strategies of shoulder MDI.

Functional outcome and quality of life after rehabilitation for voluntary posterior shoulder dislocation: a prospective blinded cohort study.

BACKGROUND: Voluntary posterior instability of the shoulder is a rare condition in which the patient is able to cause a subluxation by voluntary muscle activation. A shoulder rehabilitation program aimed to correct abnormal muscle patterns and restore correct scapular motion may provide good results and improve the quality of life of these patients. METHODS: Fifteen subjects (six males, nine females; mean age 19 years) underwent physical examination and clinical tests [Disability of the Arm, Shoulder and Hand (DASH) score, Shoulder Pain and Disability Index (SPADI), and modified Rowe score] and compiled the patient global assessment (PGA). Articular or rotator cuff lesions were excluded by X-rays and MRI. The rehabilitation program included three phases: (1) assessment and correction of abnormal muscle patterns, (2) restoration of correct scapular motion, and (3) strengthening of scapular and posterior glenohumeral muscles. Follow-up was at 3, 6, 12, and 24 months. RESULTS: DASH and SPADI scores improved significantly at 3 (p < 0.01), 6 (p < 0.009), 12 (p < 0.001), and 24 months (p < 0.001). The Rowe score was fair at 3 months and good at 6, 12, and 24 months. Active flexion, abduction, and external rotation increased at all follow-up points (p < 0.01), whereas internal rotation remained unchanged (p > 0.05). PGA values were high. Compliance was good without serious adverse events reported during the treatment. A correlation was found between age and DASH changes (Spearman's ρ -0.56; p = 0.0455). CONCLUSIONS: Our findings stress the value of a rehabilitation program that teaches subjects with voluntary instability how to correct abnormal muscle patterns to restore scapular motion, and the importance of adopting home rehabilitation exercises as a part of the normal lifestyle.

Midterm Clinical Outcomes After Arthroscopic Rotator Cuff Repair in Olympic Volleyball Players: Return to Sports and Return to Performance.

Background: The decision-making process and predicting the time to return to sport (RTS) and return to performance (RTP) after arthroscopic rotator cuff repair (ARCR) in elite volleyball players are difficult issues to address, even among experienced shoulder surgeons. Purpose/Hypothesis: The purpose of the study was to evaluate the results in Olympic-level volleyball players treated with arthroscopic supraspinatus repair and to report the RTS and the RTP. It was hypothesized that these athletes had higher RTS and faster RTP. Study Design: Case series; Level of evidence, 4. Methods: This study included 17 elite volleyball athletes (11 male, 6 female; mean age, 26.2 years) who underwent ARCR for partial- and full-thickness supraspinatus tears that did not improve despite nonoperative treatment. The clinical results were evaluated at 12 months postoperatively. The authors compared the athletes' preoperative, 6-month, and 12-month Kerlan-Jobe Orthopaedic Clinic (KJOC) scores and the visual analog scale (VAS) for pain after competition and conducted 6- and 12-month isometric strength analyses. The athletes' RTS and RTP times were recorded. Results: All tears were on the dominant side (15 right, 2 left), and 82% were partial tears (14 partial thickness, 3 full thickness). The mean time from the onset of symptoms to surgery was 11.3 ± 6.7 months. While the mean Kerlan-Jobe Orthopaedic Clinic score was 31 preoperatively, it was 89 after 6 months (P < .001 vs preoperative) and 96 after 12 months (P = .003 vs 6 months). The mean VAS for pain was 7.9 preoperatively, 0.4 at 6 months (P < .001 vs preoperative), and 0.1 at 12 months (P = .02 vs 6 months). All athletes were able to reach their preinjury level, with RTS at a mean of 6.9 months and RTP at a mean of 12.4 months. Conclusion: ARCR appears to be an effective option for Olympic-level volleyball players who do not benefit from nonoperative treatment. All athletes returned to their preinjury level of sports. The surgeon and athlete can plan surgical decision-making and timing based on the mean RTS time of 6.9 months and mean RTP time of 12.4 months.

Molecular changes underlying decay of sensory responses and enhanced seizure propensity in peritumoral neurons.

BACKGROUND: Glioblastoma growth impacts on the structure and physiology of peritumoral neuronal networks, altering the activity of pyramidal neurons which drives further tumor progression. It is therefore of paramount importance to identify glioma-induced changes in pyramidal neurons, since they represent a key therapeutic target. METHODS: We longitudinal monitored visual evoked potentials after the orthotopic implant of murine glioma cells into the mouse occipital cortex. With laser microdissection, we analyzed layer II-III pyramidal neurons molecular profile and with local field potentials recordings we evaluated the propensity to seizures in glioma-bearing animals with respect to control mice. RESULTS: We determine the time course of neuronal dysfunction of glioma-bearing mice and we identify a symptomatic stage, based on the decay of visual response. At that time point, we microdissect layer II-III pyramidal neurons and evaluate the expression of a panel of genes involved in synaptic transmission and neuronal excitability. Compared to the control group, peritumoral neurons show a decrease in the expression of the SNARE complex gene SNAP25 and the alpha1 subunit of the GABA-A receptor. No significant changes are detected in glutamatergic (ie, AMPA or NMDA receptor subunit) markers. Further reduction of GABA-A signaling by delivery of a benzodiazepine inverse agonist, DMCM (methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate) precipitates seizures in 2 mouse models of tumor-bearing mice. CONCLUSIONS: These studies reveal novel molecular changes that occur in the principal cells of the tumor-adjacent zone. These modifications may be therapeutically targeted to ameliorate patients' quality of life.

Long-term subscapularis strength assessment after Bristow-Latarjet procedure: isometric study.

BACKGROUND: The subscapularis is the strongest rotator cuff muscle. Bristow-Latarjet procedure may impair subscapularis function. The aim of the study is to describe the difference in isometric subscapularis (SSC) strength after L-shape tenotomy versus muscle split in patients who underwent to Bristow-Latarjet procedure. MATERIALS AND METHODS: From 2000 to 2006, we enrolled 376 patients for Bristow-Latarjet procedures. We identified 2 groups according to the subscapularis approach. Group A included 264 subjects with subscapularis L shape tenotomy; group B included 112 subjects with subscapularis muscle split. The subscapularis function was assessed with lift-off and belly-press tests. Isometric strength of rotator cuff muscle was assessed at an average follow-up of 45 months in group A and 42 months in group B, recording the maximum isometric peak torque (PT) (N), maximum isometric couple (Nm), relative strength index (N/Kg), strength, couple and external/internal rotator ratio. Constant and Rowe were used as scores. RESULTS: Subscapularis assessment in the overall population showed 33 cases (8.8%) with a positive Lift-off test and 30 cases (8%) with a positive belly-press test. Rowe and Constant scores increased in both groups (P < .01). The mean PT in group A was lower of 24,8 Nw than group B (P < .01); similarly, the max PT values of group A were lower of 26.1 Nw than group B (P < .01). CONCLUSION: L-shaped tenotomy in Bristow-Latarjet procedure has a weakening effect on the subscapularis and for these reasons we strongly recommend the muscle split approach for an optimal subscapularis function recovery.

Infraspinatus strength assessment before and after scapular muscles rehabilitation in professional volleyball players with scapular dyskinesis.

HYPOTHESIS: This study tested the hypothesis that infraspinatus strength in professional volleyball players can be assessed with the scapula free (infraspinatus strength test, IST) and with the scapula retracted (infraspinatus scapula retraction test, ISRT) before and after scapular musculature training. MATERIALS AND METHODS: A prospective study was performed in 31 professional volleyball players. Isometric strength (kg) of the infraspinatus with IST and with ISRT was recorded by a handheld dynamometer and compared with the values found after 3 and 6 months of rehabilitation. Magnetic resonance imaging was performed to exclude articular and cuff pathology. Pain scores were assessed using a visual analog scale. RESULTS: The mean increase in the force values of IST was statistically significant after 3 months (P < .01) and 6 months (P < .001) of rehabilitation. The mean difference between IST and ISRT decreased from 4.72 ± 0.007 before rehabilitation to 1.2 ± 0.26 at 3 months and to 0.4 ± 0.006 at 6 months. The mean score for pain was 2.4 ± 1.8 at 3 months and 2.6 ± 1.4 at 6 months. DISCUSSION: Acquired scapular dyskinesis in overhead athletes can lead to the rotator cuff weakness. Inhibition due to pain and the negative biomechanic effect of scapular dyskinesis results in specific infraspinatus dysfunction that arise with the ISRT. CONCLUSIONS: ISRT is practical and consistent to assess the infraspinatus strength in overhead athletes with scapular dyskinesis. A functional rehabilitation protocol, designed to restore scapular muscles balance and shoulder mobility, is essential in the training program to prevent shoulder dysfunction and improve sports performance.

Infraspinatus scapular retraction test: a reliable and practical method to assess infraspinatus strength in overhead athletes with scapular dyskinesis.

BACKGROUND: Alteration of normal scapulohumeral rhythm due to the fatigue of scapular-stabilizing muscles induces decrease of rotator cuff strength. In this study we analyzed the interobserver and intraobserver realibility of the infraspinatus strength test (IST) and infraspinatus scapular retraction test (ISRT) in 29 overhead athletes with scapular dyskinesis, before and after 6 months of scapular musculature rehabilitation. MATERIALS AND METHODS: Subjects with magnetic resonance imaging (MRI) findings of labral injuries (2 cases, 5%) and cuff tears (4 cases, 11%) were excluded. Scapular dyskinesis patterns were evaluated according to Kibler et al. (J Shoulder Elbow Surg 11:550-556, 2002). We found a type I dyskinesis in 24 cases (83%) and a type II in 5 cases (17%). Patients were tested by using IST and ISRT and the maximum infraspinatus strength (kg) was registered by a handheld dynamometer. Changes in shoulder IR were measured by using a standard goniometry. Rehabilitation continued for 6 months and was focused on the restoration of scapular muscular control and balance. We used a paired Student t test for the significance of the force values (alpha = 0.01). Intraclass correlation coefficient (ICC) and standard error (SE) were applied to determine the realibility of repeated values collected within testers and between testers. RESULTS: Values of ICC close to 1 at baseline and at 6 months indicated a higher interexaminer and intraexaminer realibility. IST force values registered a significant increase at 6 months for both examiners (P < 0.01). The mean difference between IST and ISRT values were not significant at 6 months (P > 0.01). The increase of glenohumeral internal rotation was significant at 6 months (P < 0.01). CONCLUSION: The good realibility and the easy reproducibility make the ISRT an excellent test to assess patients with infraspinatus weakness due to scapular dyskinesis and address them toward an appropriate program of rehabilitation aimed to restore scapular musculature balance and control.

Assessment of the ability of wheelchair subjects with spinal cord injury to perform a specific protocol of shoulder training: a pilot study.

BACKGROUND: a regular program of exercises in subjects with spinal cord injury (SCI) can contribute to reduce the risk of upper extremities injuries. METHODS: in this prospective laboratory study we tested the hypothesis that a training machine developed for able-body users is suitable for a shoulder training protocol in 11 paraplegic subjects with SCI. Overall subjects were assessed with the SCIM III, CS, DASH and standard shoulder examination. We set a protocol of shoulder exercises performed with a training machine. Overall subjects were able to perform the protocol but 2 did not complete the exercises n° 6 and 7. The position of the wheelchair during each exercise was recorded. Wheelchair position/loading level were significantly correlated with the protocol n° 2, 3 and 5 as well as BMI/loading level for the exercises n° 5 and 9 and age/loading level for the exercise n° 7. Clinical scores were neither correlated with loading nor with anthropometric data. RESULTS/CONCLUSIONS: FROM THE ANALYSIS OF DATA COLLECTED IN THIS STUDY ARISED THAT: 1) the training machine needs some adjustments for paraplegic subjects, 2) the training protocol was appropriate except for the exercises needing a torso-rotation and 3) the template for wheelchair position may be a valid guide for an optimal paraplegic shoulder training.

Supraspinatus and infraspinatus weakness in overhead athletes with scapular dyskinesis: strength assessment before and after restoration of scapular musculature balance.

A disturbance in scapulohumeral rhythm may cause negative biomechanic effects on rotator cuff (RC). Alteration in scapular motion and shoulder pain can influence RC strength. Purpose of this study was to assess supraspinatus and infraspinatus strength in 29 overhead athletes with scapular dyskinesis, before and after 3 and 6 months of rehabilitation aimed to restore scapular musculature balance. A passive posterior soft tissues stretching was prescribed to balance shoulder mobility. Scapular dyskinesis patterns were evaluated according to Kibler et al. Clinical assessment was performed with the empty can (EC) test and infraspinatus strength test (IST). Strength values were recorded by a dynamometer; scores for pain were assessed with VAS scale. Changes of shoulder IR were measured. The force values increased at 3 months (P < 0.01) and at 6 months (P < 0.01). Changes of glenohumeral IR and decrease in pain scores were found at both follow-up. Outcomes registered on pain and strength confirm the role of a proper scapular position for an optimal length-tension relationship of the RC muscles. These data should encourage those caring for athletes to consider restoring of scapular musculature balance as essential part of the athletic training.