Unilateral Anterior Shoulder Instability Research Articles

Minimal but potentially clinically relevant anteroinferior position of the humeral head following traumatic anterior shoulder dislocations: A 3D-CT analysis.

In unstable shoulders, excessive anteroinferior position of the humeral head relative to the glenoid can lead to a dislocation. Measuring humeral head position could therefore be valuable in quantifying shoulder laxity. The aim of this study was to measure (1) position of the humeral head relative to the glenoid and (2) joint space thickness during passive motion in unstable shoulders caused by traumatic anterior dislocations and in contralateral uninjured shoulders. A prospective cross-sectional CT-study was performed in patients with unilateral anterior shoulder instability. Patients underwent CT scanning of both injured and uninjured side in supine position (0° abduction and 0° external rotation) and in 60°, 90°, and 120° of abduction with 90° of external rotation without an external load. Subsequently, 3D virtual models were created of the humerus and the scapula to create a glenoid coordinate system to identify poster-anterior, inferior-superior, and lateral-medial position of the humeral head relative to the glenoid. Joint space thickness was defined as the average distance between the subchondral bone surfaces of the humeral head and glenoid. Fifteen consecutive patients were included. In supine position, the humeral head was positioned more anteriorly (p = 0.004), inferiorly (p = 0.019), and laterally (p = 0.021) in the injured compared to the uninjured shoulder. No differences were observed in any of the other positions. A joint-space thickness map, showing the bone-to-bone distances, identified the Hill-Sachs lesion footprint on the glenoid surface in external rotation and abduction, but no differences on average joint space thickness were observed in any position.

Native Glenoid Depth and Hill-Sachs Lesion Morphology in Traumatic Anterior Shoulder Instability

Background: Although Hill-Sachs lesions (HSLs) are assumed to be influenced by glenoid characteristics in the context of bipolar bone loss, little is known about how glenoid concavity influences HSL morphology. Purpose: To investigate the relationship between the native glenoid depth and HSL morphological characteristics. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Computed tomography images of bilateral shoulders from 151 consecutive patients with traumatic unilateral anterior shoulder instability were retrospectively reviewed. Patients were categorized into flat (<1 mm), moderate (1-2 mm), and deep (>2 mm) groups based on the native glenoid depth measured from the contralateral unaffected shoulder. The HSL morphological characteristics included size (depth, width, length, and volume), location (medial, superior, and inferior extent), and orientation (rim and center angle). The glenoid characteristics included diameter, depth, version, and bone loss. The patient, glenoid, and HSL morphological characteristics were compared among the 3 depth groups. Subsequently, the independent predictors of some critical HSL morphological characteristics were determined using multivariate stepwise regression. Results: After exclusion of 55 patients, a total of 96 patients were enrolled and classified into the flat group (n = 31), moderate group (n = 35), and deep group (n = 30). Compared with those in the flat group, patients in the deep group were more likely to have dislocation (38.7% vs 93.3%; P = .009) at the primary instability and had a significantly larger number of dislocations (1.1 ± 1.0 vs 2.2 ± 1.8; P = .010); moreover, patients in the deep group had significantly deeper, wider, larger volume, more medialized HSLs and higher incidences of off-track HSLs (all P≤ .025). No significant differences were detected among the 3 groups in HSL length, vertical position, and orientation (all P≥ .064). After adjustment for various radiological and patient factors in the multivariate regression model, native glenoid depth remained the strongest independent predictor for HSL depth (β = 0.346; P < .001), width (β = 0.262; P = .009), volume (β = 0.331; P = .001), and medialization (β = −0.297; P = .003). Conclusion: The current study sheds light on the association between native glenoid depth and the morphology of HSLs in traumatic anterior shoulder instability. Native glenoid depth was independently and positively associated with HSL depth, width, volume, and medialization. Patients with deeper native glenoids were more likely to have off-track HSLs and thus require more attention in the process of diagnosis and treatment.

Intra-articular biomechanical environment following modified Bristow and Latarjet procedures in shoulders with large glenoid defects: relationship with postoperative complications.

Although coracoid transfers including the modified Bristow and Latarjet procedures are widely used to treat anterior shoulder instability, the influence of the choice of procedure on the biomechanical outcomes is not well characterized. We aimed to clarify the intra-articular stress distribution following these 2 procedures using 3-dimensional finite-element analysis and to investigate the role of stress distribution in the pathophysiology of postoperative complications. Overall, 6 male patients aged 17-47 years with unilateral anterior shoulder instability were recruited. Computed tomographic digital imaging and communications in medicine (CT-DICOM) data of the contralateral (healthy) shoulder of each patient was obtained and used for developing the 3-dimensional normal glenohumeral joint model. A 25% bony defect was created in the anterior glenoid rim where the coracoid process was transferred in the standing and lying-down positions to create the Bristow and Latarjet models, respectively. The arm position was set as 0° or 90° abduction. The Young moduli of the humerus and scapula were calculated using CT data, and set as 35.0 MPa and 113.8 GPa for the articular cartilage and inserted screw, respectively. A compressive load (50 N) was applied to the greater tuberosity toward the center of the glenoid, and a tensile load (20 N) was applied to the tip of the coracoid in the direction of conjoint tendon. Elastic analysis was used to determine the equivalent stress distribution. A significant reduction in mean equivalent stress was observed within the glenoid cartilage for both models (P = .031); however, a new stress concentration appeared within the grafted coracoid-facing region of the humeral-head cartilage in both models. The proximal half of the coracoid graft exhibited lower equivalent stress than the distal half in 5 of the 6 Latarjet models, whereas the proximal half showed higher equivalent stress than the distal half in all 6 Bristow models. High stress concentration was identified at the midpoint of the inserted screw in Bristow models. Intra-articular stress distribution may explain the different rates of postoperative complications associated with the modified Bristow and Latarjet procedures. New stress concentration within the humeral-head cartilage might contribute to the development of glenohumeral osteoarthritis following both procedures. Stress shielding in the proximal part of the coracoid graft might contribute to osteolysis following the Latarjet procedure. Surgeons should be aware of the risk of breakage of the inserted screw following the modified Bristow procedure.

Comparison of best-fit circle versus contralateral comparison methods to quantify glenoid bone defect

Several measurement techniques have been reported to quantify glenoid bone defect in patients with anterior shoulder instability. Among them, the method that uses a best-fit circle and another that uses the contralateral glenoid as a control are most commonly used. However, to our knowledge, no study has been reported that compared the reliability of these methods. The purpose of this study, therefore, was to determine which of these methods has higher reproducibility. In this study, 3-dimensional computed tomography data from 94 patients (mean age 29 years) with unilateral anterior shoulder instability were used. Three examiners measured the glenoid bone defect of each patient 3 times using 2 techniques: the best-fit circle method and the contralateral comparisonmethod. Intra- and interobserver reliabilities were measured using intraclass correlation coefficient(ICC). The intraobserver reliability was found to be 0.91 for the best-fit circle methodand 0.98 for the contralateral comparison method. The interobserver reliability was 0.77 for the best-fit circle methodand 0.88 for the contralateral method. The percentage of glenoid defect was 11.5% when using the best-fit circle and 10.7% with the contralateral method. The contralateral comparison method was more reliable than the best-fit circle method for quantifying the amount of glenoid bone loss.

Challenging the Current Concept of Critical Glenoid Bone Loss in Shoulder Instability: Does the Size Measurement Really Tell It All?

Background: Bone loss at the anterior glenoid rim is a main reason for failure of soft-tissue based surgical stabilization procedures in patients with anterior shoulder instability. Purpose: To evaluate the capability of conventional glenoid bone loss measurement techniques to provide an adequate estimation of the actual biomechanical effect of glenoid defects. Study Design: Descriptive laboratory study. Methods: Thirty consecutive patients with unilateral anterior shoulder instability and varying degrees of glenoid defect were included. Patient-specific computer tomography–based 3-dimensional shoulder models of the affected and unaffected sides were created. The bony shoulder stability ratio (SR) was determined in various potential dislocation directions with finite element analysis. Values obtained from conventional glenoid defect size measurement techniques (Pico and Sugaya) were correlated with the finite element analysis results. Additionally, a mathematical model was developed to theoretically analyze the correlation between glenoid defect size measurements and the SR. Results: The authors found substantial interindividual differences of the SR of the unaffected shoulders in all directions of measurement. Bone loss at the anterior glenoid rim significantly reduced the SR in the 2-o’clock (P = .011), 3-o’clock (P < .001), and 4-o’clock (P < .001) directions referring to a right shoulder. The correlation between the defect size measurements and the SR for the 2-o’clock (rho = −0.522 and −0.580), 3-o’clock (rho = −0.597 and −0.580), and 4-o’clock (rho = −0.527 and −0.522) directions was statistically significant. However, it showed only moderate strength and was nonlinear as well as dependent on the inherent shape of the concavity. As shown by the mathematical model, bone loss has the most considerable effect at the edge of the glenoid rim, and an increasingly concave-shaped glenoid leads to an increase in loss of SR provoked by the same extent of bone loss. Conclusion: Current glenoid bone loss measurements are unable to provide an adequate estimation on the actual biomechanical effect of glenoid defects because (1) the relation between the glenoid defect size and its biomechanical effect is nonlinear and (2) patients with shoulder instability have constitutional biomechanically relevant glenoid concavity shape differences. Clinical Relevance: These findings challenge the current concept of setting a general threshold for critical glenoid bone loss, which requires bony reconstruction surgery.

Glenoid morphology is associated with the development of instability arthropathy

Instability arthropathy (IA) is a major long-term concern in patients with anterior shoulder instability. This study investigated the association of glenoid morphology with the development of IA. The study included 118 patients with unilateral anterior shoulder instability and available bilateral computed tomography scans. Instability-specific information was obtained from all patients. The glenoid morphology of the affected shoulder was compared with the nonaffected contralateral side resembling the constitutional preinjury glenoid shape. Both shoulders were evaluated independently by 3 observers to assess the grade of IA according to a Comprehensive Arthropathy Rating (CAR) system. Associations between IA and the glenoid morphology parameters were investigated. The average glenoid retroversion (P < .001), glenoid depth (P < .001), glenoid diameter (P < .001), and the bony shoulder stability ratio (P < .001) of the affected shoulder were significantly reduced compared with the contralateral side due to bony defects in 79.6% of the patients. The CAR of the affected side was significantly higher (P < .001), with more osteophytes (P = .001) and more sclerosis and cysts (P < .001). Differences in CAR (Δ-CAR) correlated positively with the age at the time of the computed tomography scan (P < .001), age at the initial dislocation (P = .001), size of the glenoid defect (P = .005), and the contralateral glenoid depth (P = .011), glenoid diameter (P = .016), and bony shoulder stability (P = .029), and negatively with glenoid retroversion of the affected side (P = .027). Development of IA arthropathy is associated not only with the age of the patients but also with morphologic parameters of the glenoid, including glenoid defect size and the constitutional glenoid concavity shape.

Bilateral shoulder proprioception deficit in unilateral anterior shoulder instability

Proprioception is an important element of shoulder dynamic stability. It has been shown to be affected in cases of capsular or labral injuries of the glenohumeral joint. Therefore, this study was conducted to investigate bilateral shoulder proprioception by active reproduction of joint position both in patients with post-traumatic recurrent unilateral shoulder instability and in normal healthy volunteers. We compared 41 patients, comprising 11 female and 30 male patients with an average age of 25.6 years (range, 18-39 years), with post-traumatic unilateral anterior shoulder instability with a control group of 27 healthy volunteers with no history of shoulder problems and with normal shoulder function during examination. All patients were examined using a high-accuracy computer-controlled electronic goniometer (Propriometer). The error of active reproduction of joint position (EARJP) was measured in abduction, flexion, external rotation, and internal rotation in both shoulders. We observed a significant deficit in the EARJP in the unstable shoulders within the instability group. Surprisingly, similar results were recorded for the contralateral, unaffected shoulders within this group of patients compared with the control group. Joint acuity increased with higher elevation of the arm position. Unilateral shoulder injuries, resulting in instability, affect proprioception in both shoulders, as demonstrated by an increased EARJP. This is the first report of unilateral shoulder instability coexisting with inferior proprioception in both shoulders.

Bilateral Coracoid Avulsion Fractures with Unilateral Anterior Instability with Glenoid Bone Loss: Use of Avulsed Fragment for Reconstruction of Glenoid.

Introduction:Coracoid fractures are often missed since the fracture is not visualized in a routine anteroposterior view of the shoulder and special views are not ordered. Shoulder dislocation is common but it is rare to have a dislocation with a coracoid fracture. The purpose of this paper is to present the rare occurrence of bilateral coracoid fractures in a patient with unilateral anterior shoulder instability managed using the same fractured coracoid fragment by the latarjet procedure.Case Report:We report a case of 48 -year -old male who presented to us with a history of recurrent dislocations of the left shoulder. He had frequent episodes of tonic–clonic seizures 5 years back. He was diagnosed to be suffering from neurocysticercosis of the brain for which he was successfully treated. He did not have any episode of seizure later, but he continued to have repeated episodes of dislocation on his left side only. On examination of his left shoulder, he had normal range of motion. He was found to be very apprehensive, even in the midrange. This made us to suspect glenoid bone loss and hence both magnetic resonance imaging and three -dimensional computed tomography (CT) scan of the left shoulder were ordered. The CT scan revealed bilateral coracoid fractures along with glenoid bone loss. An open bony procedure including iliac crest bone graft was planned after a diagnostic arthroscopy keeping in mind that the latarjet procedure may not be possible due to the coracoid fracture. During the operation, we found that the coracoid fragment was large enough to perform a latarjet procedure rather than doing an iliac crest bone graft. This itself provided stability of the shoulder on abduction and external rotation by providing a bony block not requiring any further procedure for the Hill -Sachs lesion.Conclusion:Epileptic patients should undergo CT scan evaluation for glenoid bone loss, large Hill -Sachs lesion and to rule out coracoid fractures to plan for bony stabilization procedure and since we have used the same fractured coracoids fragment for latarjet procedure and found to be successful, this add on the knowledge to the orthopedic community.

Analysis of Agreement Between Computed Tomography Measurements of Glenoid Bone Defects in Anterior Shoulder Instability With and Without Comparison With the Contralateral Shoulder

Background: Computed tomography (CT) is frequently used to diagnose glenoid bone defects in anterior shoulder instability. The assessment of glenoid defects on 2-dimensional (2D) and 3-dimensional (3D) CT scans has been reported with and without a comparative study of the contralateral shoulder; however, no previous studies have analyzed if these 4 methods agree. Purpose: To estimate agreement between CT assessments of glenoid defects by examination of the affected shoulder alone and by comparison with the contralateral side on both 2D and 3D CT scans. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: A total of 200 prospectively enlisted patients affected by unilateral anterior shoulder instability underwent CT of both shoulders. The area of the missing glenoid was calculated on 4 sets of CT scans (2D and 3D CT images with and without comparison with the contralateral shoulder) by using the circle method. Agreement between the 4 measurements in quantifying the bone defect was estimated according to the Bland-Altman method. Agreement between the 4 measurements in assessing the presence and type of defect (fracture or erosion) was analyzed with κ statistics. Results: Analysis of agreement between CT measurements in quantifying glenoid bone defects showed that the mean difference between the 4 measures was less than 1% of the area of the inferior glenoid in each pairwise comparison. Limits of agreement were always below the established acceptable limit of 5%. The assessment of the presence and type of bone defect showed strong to near-complete agreement between the 4 measurement methods. Conclusion: CT assessments of glenoid bone defects with and without comparison with the contralateral shoulder showed very good agreement in identifying the size, presence, and type of defect in patients with anterior shoulder instability on both 2D and 3D CT scans.

Active Stiffness and Strength in People With Unilateral Anterior Shoulder Instability: A Bilateral Comparison

Active muscle stiffness might protect the unstable shoulder from recurrent dislocation. To compare strength and active stiffness in participants with unilateral anterior shoulder instability and to examine the relationship between active stiffness and functional ability. Cross-sectional study. University research laboratory. Participants included 16 males (age range, 16-40 years; height = 179.4 ± 6.1 cm; mass = 79.1 ± 6.8 kg) with 2 or more episodes of unilateral traumatic anterior shoulder instability. Active stiffness and maximal voluntary strength were measured bilaterally in participants. In addition, quality of life, function, and perceived instability were measured using the Western Ontario Stability Index, American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form, and Single Alpha Numeric Evaluation, respectively. We found less horizontal adduction strength (t(15) = -4.092, P = .001) and less stiffness at 30% (t(14) = -3.796, P = .002) and 50% (t(12) = -2.341, P = .04) maximal voluntary strength in the unstable than stable shoulder. Active stiffness was not correlated with quality of life, function, or perceived instability (r range, 0.0-0.25; P > .05). The observed reduction in stiffness in the unstable shoulder warrants inclusion of exercises in the rehabilitation program to protect the joint from perturbations that might lead to dislocation. The lack of association between active stiffness and quality of life, function, or perceived instability might indicate that stiffness plays a less direct role in shoulder stability.

Long-term outcomes after repair of recurrent post-traumatic anterior shoulder instability: comparison of arthroscopic transglenoid suture and open Bankart reconstruction

The purpose of this study is to report long-term outcomes of the arthroscopic modified Caspari technique compared to an open capsular shift surgery to treat post-traumatic anterior shoulder recurrent instability. The hypothesis was that the open surgery group would show higher degenerative changes than to the modified Caspari technique group after a follow-up from 10 to 17 years. One hundred and ten nonrandomized consecutive patients who underwent a surgical repair of recurrent unilateral anterior shoulder instability between 1990 and 1999 were retrospectively analyzed. Eighty-two patients were available for long-term follow-up. In particular, 49 patients (59.8%) (group A) were treated with arthroscopic transglenoid modified Caspari suturing technique (mean follow-up 13.7 ± 2.2 years), whereas 33 patients (40.2%) (group B) were treated with combined open capsular shift and Bankart repair (mean follow-up 15.7 ± 2.2 years). Patients were evaluated according to the failure rate (re-dislocation), Rowe, UCLA, and Constant scores. Radiological osteoarthritis changes were ranked according to Samilson score. There were no statistically significant differences between the two groups concerning the failure rate (n.s.), Rowe (n.s.), UCLA (n.s.), and Constant (n.s.) scores. Group A: re-dislocation rate 12.5% (6 re-dislocations), Rowe 85.0 ± 22.6, UCLA 26.4 ± 4.8, and Constant 86.3 ± 16.7. Group B: re-dislocation rate 9% (3 re-dislocations), Rowe 83.2 ± 24.4, UCLA 26.9 ± 4.2, and Constant 87.4 ± 14.1. Radiographic findings of osteoarthritis: 2 severe (4%), 4 moderate (8%), and 12 mild (25%) in group A; 2 severe (6%), 4 moderate (12%), and 9 mild (27%) in group B; differences between groups were not statistically significant (n.s). The results after both techniques were good in majority of patients, with no significant differences in terms of re-dislocation and osteoarthritis development. Compared to the current literature, the recurrence rate was high in both groups. The modified Caspari technique could be an arthroscopic alternative for older, non-athletic shoulders. Therapeutic Study-Retrospective Comparative Study, Level III.

Intra-observer and interobserver reliability of the ‘Pico’ computed tomography method for quantification of glenoid bone defect in anterior shoulder instability

To evaluate the intra-observer and interobserver reliability of the 'Pico' computed tomography (CT) method of quantifying glenoid bone defects in anterior glenohumeral instability. Forty patients with unilateral anterior shoulder instability underwent CT scanning of both shoulders. Images were processed in multiplanar reconstruction (MPR) to provide an en face view of the glenoid. In accordance with the Pico method, a circle was drawn on the inferior part of the healthy glenoid and transferred to the injured glenoid. The surface of the missing part of the circle was measured, and the size of the glenoid bone defect was expressed as a percentage of the entire circle. Each measurement was performed three times by one observer and once by a second observer. Intra-observer and interobserver reliability were analyzed using intraclass correlation coefficients (ICCs), 95% confidence intervals (CIs), and standard errors of measurement (SEMs). Analysis of intra-observer reliability showed ICC values of 0.94 (95% CI = 0.89-0.96; SEM = 1.1%) for single measurement, and 0.98 (95% CI = 0.96-0.99; SEM = 1.0%) for average measurement. Analysis of interobserver reliability showed ICC values of 0.90 (95% CI = 0.82-0.95; SEM = 1.0%) for single measurement, and 0.95 (95% CI = 0.90-0.97; SEM = 1.0%) for average measurement. Measurement of glenoid bone defect in anterior shoulder instability can be assessed with the Pico method, based on en face images of the glenoid processed in MPR, with a very good intra-observer and interobserver reliability.

Bankart repair in traumatic anterior shoulder instability: Open versus arthroscopic technique

Purpose: The purpose of this study was to compare the results of open and arthroscopic Bankart repair using suture anchors in traumatic anterior glenohumeral instability. Variables measured were recurrence rate, range of motion, and return to preinjury activity. Type of Study: Case control study. Methods: Eighty-nine shoulders in 88 patients with traumatic unilateral anterior shoulder instability were evaluated using Rowe and University of California Los Angeles scores, recurrence, return to activity, and range of motion by an independent examiner at an average of 39 months after either an arthroscopic or open Bankart repair using suture anchors. The arthroscopic technique included a minimum of 3 anchors in most patients and a routine incorporation of capsular plication and proximal shift. Of the 89 shoulders, 30 shoulders (30 patients) underwent open Bankart repair and 59 shoulders (58 patients) underwent arthroscopic Bankart repair. Results: Twenty-six shoulders (86.6%) in the open repair group showed excellent or good results, and 54 (91.5%) shoulders in the arthroscopic repair group showed excellent or good results. The arthroscopic group revealed slightly higher scores in the Rowe (P = .041) and UCLA scores (P = .026). Two patients (6.7%) in the open repair group and 2 (3.4%) in the arthroscopic repair group had experienced at least 1 episode of redislocation after the surgery. One patient (3.3%) in the open repair group and 4 (6.8%) in the arthroscopic repair group demonstrated mild apprehension. The overall residual instability was 10% in the open repair group and 10.2% in the arthroscopic repair group. There were no significant differences in the loss of external rotation and return to prior activity between the 2 groups (P > .05). Residual instability occurred more frequently in patients with fewer anchors. Conclusions: Arthroscopic suture anchor capsulorraphy showed similar results to the open Bankart procedure.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 18, No 7 (September), 2002: pp 755–763