The anterior band of the inferior glenohumeral ligament. Assessment of its permanent deformation and the anatomy of its glenoid attachment

Biomechanical study of 3D-printed titanium alloy pad for repairing glenoid bone defect

Background: The purpose of this study was to investigate the effect of 3D-printed technology to repair glenoid bone defect on shoulder joint stability. Methods: The shoulder joints of 25 male cadavers were tested. The 3D-printed glenoid pad was designed and fabricated. The specimens were divided into 5 groups. Group A: no bone defect and the structure of the glenoid labrum and joint capsule was intact; Group B: Anterior inferior bone defect of the shoulder glenoid; Group C: a pad with a width of 2 mm was installed; Group D: a pad with a width of 4 mm was installed; Group E: a pad with a width of 6 mm was installed. This study measured the distance the humeral head moved forward at the time of glenohumeral dislocation and the maximum load required to dislocate the shoulder. Results: The shoulder joint stability and humerus displacement was significantly lower in groups B and C compared with group A (p < .05). Compared with group A, the stability of the shoulder joint of group D was significantly improved (p < .05). However, there was no significant difference in humerus displacement between groups D and A (p > .05). In addition, compared with group A, shoulder joint stability was significantly increased and humerus displacement was significantly decreased in group E (p < .05). Conclusion: The 3D-printed technology can be used to make the shoulder glenoid pad to perfectly restore the geometric shape of the shoulder glenoid articular surface. Moreover, the 3D-printed pad is 2 mm larger than the normal glenoid width to restore the initial stability of the shoulder joint.

Serial Magnetic Resonance Arthrography for a Midsubstance Capsular Tear in a Patient With Traumatic Anterior Shoulder Instability

The natural history of midsubstance capsular tears (MCTs) is unclear. We herein describe a case of MCT observed using serial magnetic resonance (MR) arthrography. A 46-year-old woman presented with excessive external rotation of the left glenohumeral joint, resulting in an initial anterior dislocation of the left shoulder. She subsequently developed recurrent shoulder joint dislocations. MR arthrography revealed an MCT without a Bankart lesion three months after the initial dislocation. She opted for nonoperative treatment, but the shoulder instability did not improve. The second MR arthrography, nine months after the initial dislocation, showed no natural healing of the MCT. The third MR arthrography, 12 months after the initial dislocation, also showed no natural healing. Her shoulder instability remained persistent. The patient then decided to have surgery. Arthroscopy revealed a large capsular defect extending from the glenoid to the humeral head in the anterior inferior glenohumeral ligamentous complex. The MCT was repaired with the placement of nonabsorbable sutures in a side-to-side fashion. At the final follow-up, three years postoperatively, the patient had no anterior shoulder instability. The Rowe score was 100 points. MR arthrography showed good repair integrity of the MCT at one year postoperatively. Serial MR arthrography was useful for both the patient and the shoulder surgeon in considering the treatment of the MCT, facilitating an accurate and qualitative assessment of whether natural healing of the MCT had been achieved.

Load-to-failure characteristics of patellar tendon allograft superior capsule reconstruction compared with the native superior capsule

Background

The potential use of a patellar tendon allograft for superior capsular reconstruction has been demonstrated biomechanically; however, there are concerns regarding compromised fixation strength owing to the longitudinal orientation of the fibers in the patellar tendon. Therefore, the purpose of this study was to compare the fixation strength of superior capsule reconstruction using a patellar tendon allograft to the intact superior capsule.

Methods

The structural properties of the intact native superior capsule (NSC) followed by superior capsular reconstruction using a patellar tendon allograft (PT-SCR) were tested in eight cadaveric specimens. The scapula and humerus were potted and mounted onto an Instron testing machine in 20 degrees of glenohumeral abduction. Humeral rotation was set to achieve uniform loading across the reconstruction. Specimens were preloaded to 10 N followed by cyclic loading from 10 N to 50 N for 30 cycles, then load to failure at a rate of 60 mm/min. Video digitizing software was used to quantify the regional deformation characteristics.

Results

During cyclic loading, there was no difference found in stiffness between PT-SCR and NSC (cycle 1 - PT-SCR: 12.9 ± 3.6 N/mm vs. NSC: 22.5 ± 1.6 N/mm; P = .055 and cycle 30 - PT-SCR: 27.3 ± 1.4 N/mm vs. NSC: 25.4 ± 1.7 N/mm; P = .510). Displacement at the yield load was not significantly different between the two groups (PT-SCR: 7.0 ± 1.0 mm vs. NSC: 6.5 ± 0.3 mm; P = .636); however, at the ultimate load, there was a difference in displacement (PT-SCR: 20.7 ± 1.1 mm vs. NSC: 8.1 ± 0.5 mm; P < .001). There was a significant difference at both the yield load (PT-SCR: 71.4 ± 2.2 N vs. NSC: 331.6 ± 56.6 N; P = .004) and the ultimate load (PT-SCR: 217.1 ± 26.9 N vs. NSC: 397.7 ± 62.4 N; P = .019). At the yield load, there was a difference found in the energy absorbed (PT-SCR: 84.4 ± 8.9 N-mm vs. NSC: 722.6 ± 156.8 N-mm; P = .005), but no difference in energy absorbed was found at the ultimate load.

Conclusions

PT-SCR resulted in similar stiffness to NSC at lower loads, yield displacement, and energy absorbed to ultimate load. The ultimate load of the PT-SCR was approximately 54% of the NSC, which is comparable with the percent of the ultimate load in rotator cuff repair and the intact supraspinatus at time zero.

Mapping of the Inferior Glenohumeral Ligament for Suture Pullout Strength: A Biomechanical Analysis

Background

Suture pullout during rehabilitation may result in loss of tension in the inferior glenohumeral ligament (IGHL) and contribute to recurrent instability after capsular plication, performed with or without labral repair. To date, the suture pullout strength in the IGHL is not well-documented. This may contribute to recurrent instability.

Purpose/Hypothesis

A cadaveric biomechanical study was designed to investigate the suture pullout strength of sutures in the IGHL. We hypothesized that there would be no significant variability of suture pullout strength between specimens and zones. Additionally, we sought to determine the impact of early mobilization on sutures in the IGHL at time zero. We hypothesized that capsular plication sutures would fail under low load.

Study Design

Descriptive laboratory study.

Methods

Seven fresh-frozen cadaveric shoulders were dissected to isolate the IGHL complex, which was then divided into 18 zones. Sutures in these zones were attached to a linear actuator, and the resistance to suture pullout was recorded. A suture pullout strength map of the IGHL was constructed. These loads were used to calculate the load applied at the hand that would initiate suture pullout in the IGHL.

Results

Mean suture pullout strength for all specimens was 61.6 ± 26.1 N. The maximum load found to cause suture pullout through tissue was found to be low, regardless of zone of the IGHL. Calculations suggest that an external rotation force applied to the hand of only 9.6 N may be sufficient to tear capsular sutures at time zero.

Conclusion

This study did not provide clear evidence of desirable locations for fixation in the IGHL. However, given the low magnitude of failure loads, the results suggest the timetable for initiation of range-of-motion exercises should be reconsidered to prevent suture pullout through the IGHL.

Clinical Relevance

From this biomechanical study, the magnitude of force required to cause suture pullout through the IGHL is met or surpassed by normal postoperative early range-of-motion protocols.

Revisiting the Anterior Glenoid: An Analysis of the Calcified Cartilage Layer, Capsulolabral Complex, and Glenoid Bone Density

PURPOSE

In this cadaveric study, we aim to define the basic anatomy of the anterior glenoid with attention to the relationships of calcified cartilage, capsulolabral complex, and osseous morphology of the anterior glenoid.

METHODS

Seventeen cadaveric glenoid specimens (14 male, 3 female, mean age 53.9 ± 10) were imaged with micro-computed tomography (CT) and embedded in poly-methyl-methacrylate. Specimens were included for final analysis only if the entire glenoid articular cartilage, labrum, capsule, and biceps insertion were pristine and without evidence of injury, degeneration, or damage during the preparation process. Group 1 members (n = 9) were axially sectioned through 3 to 9 o'clock and 4 to 8 o'clock; group 2 members (n = 8) were radially sectioned through 3, 4, 5, and 9 o'clock. A scanning electron microscope (SEM) analysis quantified the percentage of bone within a 5 × 2.5 mm region at the glenoid rim. Micro-CT, SEM, and light microscopy evaluated the capsulolabral complex and calcified fibrocartilage.

RESULTS

A 7 ± 2.1 mm region of calcified fibrocartilage at 4 o'clock was identified from the articular face to the medial glenoid neck supporting the overlying capsulolabral footprint and was >3× thicker at the articular attachment (316 ± 153 μm) versus the glenoid neck (92 ± 66 μm). At 3 to 9 o'clock and 4 to 8 o'clock 79.2% ± 5.4% and 75.2% ± 7.8% of the glenoid osseous width was covered with articular cartilage. The labrum accounted for 13.1% ± 3.4% of the glenoid width at 4 o'clock. SEM analysis demonstrated decreased glenoid bone density at 3, 4, and 5 o'clock (P ≤ .015) and no difference (P = .448) at 9 o'clock versus central subchondral bone.

CONCLUSIONS

The capsulolabral footprint contributes significantly to the glenoid face, inserts directly adjacent to the articular cartilage, and extends medially along the glenoid neck. A layer of calcified fibrocartilage lies immediately beneath the capsulolabral footprint and is 3× thicker at the articular insertion compared with the glenoid neck. Lastly, there is a bone density gradient at the anterior-inferior rim versus the central subchondral bone.

CLINICAL RELEVANCE

Arthroscopic Bankart repair has been reported to have a significant failure rate in many settings. It is felt that reproducing anatomy with the repair could help improve outcomes. Based on this study's findings, an arthroscopic Bankart technique that most closely reproduces native anatomy and potentially optimizes soft-tissue healing could be performed. This includes removal of 1 to 2 mm of articular cartilage from the glenoid face with anchor placement at this location to appropriately reposition the capsulolabral complex.

Lower shoulder abduction during throwing motion may cause forceful internal impingement and decreased anterior stability

BACKGROUND

Internal impingement and decreased anterior stability, which result from shoulder capsular loosening, are common shoulder pathologies in throwing athletes. The purpose of this study was to assess the effect of shoulder abduction angle on shoulder internal impingement and anterior shoulder stability during the simulated throwing motion.

METHODS

Eight cadaveric shoulders were tested by simulating the late-cocking and acceleration phases of the throwing motion for intact and thrower's shoulder conditions. The maximal glenohumeral external rotation, anterior translation, location of the rotator cuff insertion with respect to the glenoid, length and site of internal impingement, and glenohumeral contact pressure were measured. All data were compared between shoulder abduction angles of 80°, 90°, and 100°.

RESULTS

Decreasing shoulder abduction in the simulated late-cocking phase shifted the humeral head posteriorly (P < .03) and superiorly (P < .001), decreasing the total internal impingement area between the greater tuberosity and glenoid (P = .04) and increasing the glenohumeral contact pressure during internal impingement (P = .02). In the simulated acceleration phase, anterior glenohumeral translation significantly increased as the shoulder abduction angle decreased (P < .001).

CONCLUSION

Decreasing shoulder abduction significantly increased the contact pressure during internal impingement in the simulated late-cocking phase of the throwing motion. During the simulated acceleration phase of the throwing motion, anterior glenohumeral translation significantly increased as shoulder abduction decreased.

Humeral Avulsion of the Glenohumeral Ligament: Indications for Surgical Treatment and Outcomes-A Systematic Review

Background:

The inferior glenohumeral ligament, the most important static anterior stabilizer of the shoulder, becomes disrupted in humeral avulsion of the glenohumeral ligament (HAGL) lesions. Unfortunately, HAGL lesions commonly go unrecognized. A missed HAGL during an index operation to treat anterior shoulder instability may lead to persistent instability. Currently, there are no large studies describing the indications for surgical repair or the outcomes of patients with HAGL lesions.

Purpose:

To search the literature to identify surgical indications for the treatment of HAGL lesions and discuss reported outcomes.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

Two reviewers completed a comprehensive literature search of 3 online databases (MEDLINE, EMBASE, and Cochrane Library) from inception until May 25, 2016, using the keywords “humeral avulsion of the glenohumeral ligament” or “HAGL” to generate a broad search. Systematic screening of eligible studies was undertaken in duplicate. Abstracted data were organized in table format, with descriptive statistics presented.

Results:

After screening, 18 studies comprising 118 patients were found that described surgical intervention and outcomes for HAGL lesions. The mean patient was 22 years (range, 12-50 years), and 82% were male. Sports injuries represented 72% of all HAGL injuries. The main surgical indication was primary anterior instability, followed by pain and failed nonoperative management. Commonly associated injuries in patients with identified HAGL lesions included a Bankart lesion (15%), Hill-Sachs lesions (13%), and glenoid bone loss (7%). Reporting of outcome scores varied among the included studies. Meta-analysis was not possible, but all included studies reported significantly improved postoperative stability and function. There were no demonstrated differences in outcomes for patients treated with open versus arthroscopic surgical techniques. All but 2 patients undergoing operative management for HAGL lesions were able to return to sport at their previous levels; these included Olympians and professional athletes.

Conclusion:

HAGL lesions typically occur in younger male patients and are often associated with Bankart lesions and bone loss. Open and arthroscopic management techniques are both effective in preventing recurrent instability.

Isolated HAGL lesion after arthroscopic Bankart repair in a professional soccer player

Post-traumatic anterior shoulder instability commonly occurs following an avulsion of capsulolabral complex from glenoid (Bankart lesion) or rarely after humeral avulsion of the glenohumeral ligaments (HAGL lesion). Arthroscopic Bankart repair offers high success rates of healing. However, trauma following the treatment may cause implant failure or re-avulsion of the treated tissue. We aim to present the diagnosis and treatment of an isolated HAGL lesion in a professional soccer player who had previously undergone arthroscopic Bankart repair.

Anatomy of the capsulolabral complex and rotator interval related to glenohumeral instability

The glenohumeral joint with instability is a common diagnosis that often requires surgery. The aim of this review was to present an overview of the anatomy of the glenohumeral joint with emphasis on instability based on the current literature and to describe the detailed anatomy and anatomical variants of the glenohumeral joint associated with anterior and posterior shoulder instability. A review was performed using PubMed/MEDLINE using key words: Search terms were "glenohumeral", "shoulder instability", "cadaver", "rotator interval", "anatomy", and "anatomical study". During the last decade, the interest in both arthroscopic repair techniques and surgical anatomy of the glenohumeral ligament (superior, middle, and inferior), labrum, and rotator interval has increased. Understanding of the rotator interval and attachment of the inferior glenohumeral ligament on the glenoid or humeral head have evolved significantly. The knowledge of the detailed anatomy and anatomical variations is essential for the surgeon in order to understand the pathology, make a correct diagnosis of instability, and select proper treatment options. Proper understanding of anatomical variants can help us avoid misdiagnosis. Level of evidence V.

A large humeral avulsion of the glenohumeral ligaments decreases stability that can be restored with repair

BACKGROUND

Humeral avulsion of the glenohumeral ligaments (HAGL) has become a recognized cause of recurrent shoulder instability; however, it is unknown whether small and large HAGL lesions have similarly destabilizing effects and if large lesion repair results in restoration of stability.

QUESTIONS/PURPOSES

In a cadaver model, we evaluated the effect of small and large HAGL lesions and large HAGL lesion repair on glenohumeral ROM, translation, and kinematics.

METHODS

We measured rotational ROM, humeral head translation under load, and humeral head apex position in eight cadaveric shoulders. Each specimen was tested in 60° glenohumeral abduction in the scapular and coronal planes under four conditions: intact, small HAGL lesion (mean ± SD length, 18 ± 1.8 mm), large HAGL lesion (36.8 ± 3.6 mm), and after large HAGL lesion repair. For each condition, we measured maximum internal and external rotation with 1.5 Nm of torque; glenohumeral translation in 90° external rotation with 15- and 20-N force applied in the anterior, posterior, superior, and inferior directions; and humeral head apex position throughout ROM. Repeated-measures ANOVA was used for statistical analysis.

RESULTS

Small HAGL lesions did not change ROM, translation, or kinematics from the normal shoulder; however, these parameters changed with large HAGL lesions. Maximum external rotation and total ROM increased in the scapular (13.8° ± 9.4°, p < 0.001; 19.0° ± 16.5°, p < 0.001) and coronal (21.4° ± 10.6°, p < 0.001; 29.1° ± 22.1°, p < 0.001) planes. With anterior force, anterior-inferior translation increased in both planes (mean increase for both loads and planes: anterior: 9.1 ± 9.5 mm, p < 0.01; inferior, 5.7 ± 6.6 mm, p < 0.03). In the coronal plane, posterior and inferior translation also increased (4.9 ± 5.4 mm, p < 0.01; 7.1 ± 9.9 mm, p < 0.03; averaged for both loads). The humeral head apex shifted 3.7 ± 4.9 mm anterior (p = 0.04) and 2.8 ± 2.6 mm lateral (p = 0.004) in the scapular plane and 3.7 ± 3.4 mm superior (p = 0.006) and 4.1 ± 2.6 mm lateral (p < 0.001) in the coronal plane. HAGL lesion repair decreased ROM and translation in both planes and restored humeral head position in maximum external rotation.

CONCLUSIONS

Anterior large HAGL lesions increase ROM and glenohumeral translation. After large HAGL lesion repair, stability of the shoulder can be restored.

CLINICAL RELEVANCE

Surgeons should be aware of the possibility of HAGL lesions in patients with shoulder instability, and if large HAGL lesions are diagnosed, surgeons should consider repairing the lesions.

Effect of Bankart repair on the loss of range of motion and the instability of the shoulder joint for recurrent anterior shoulder dislocation

BACKGROUND

Bankart repair postoperative complications include loss of shoulder motion and shoulder instability. The primary reason that postoperative complications develop may be excessive imbrication of the anterior band of the inferior glenohumeral ligament (AIGHL) or inadequate repair position. The purpose of this study was to quantitatively evaluate the influence of inadequate repair by computer simulation for a normal shoulder joint.

METHODS

Magnetic resonance images of 10 normal shoulder joints were acquired for 7 positions every 30° from the maximum internal rotation to the maximum external rotation with the arm abducted at 90°. The shortest 3-dimensional path of the AIGHL in each rotational orientation was calculated. We used computer simulations to anticipate the loss of motion and instability by changing the AIGHL length and insertion sites on the glenoid.

RESULTS

The AIGHL length measured 50 ± 5 mm at the maximum external shoulder rotation. AIGHL shortening by 3, 6, and 9 mm made the angle of maximum external rotation 80°, 68°, and 54°, respectively. A superior deviation of 3, 6, and 9 mm on the glenoid insertion resulted in a maximum external rotation angle of 85°, 79°, and 77°. An inferior deviation of 3, 6, and 9 mm produced humeral head translation of 1.7, 2.9, and 3.6 mm.

CONCLUSION

Simulation of both excessive imbrication and deviation of the insertion position led to quantitative prediction of the resulting loss of motion and instability. These findings will be useful for anticipating complications after Bankart repair.

LEVEL OF EVIDENCE

Basic science study, computer modeling, imaging.

Anterior shoulder dislocation increases the propensity for recurrence: a cadaveric study of the number of dislocations and type of capsulolabral lesion

BACKGROUND

The number of anterior shoulder dislocations that predispose to recurrence is unknown; some clinicians recommend surgical repair after the initial episode and others after multiple recurrences. The purpose of this study was to quantify the forces during successive anterior dislocations of cadaveric shoulders and to inspect the capsule and labrum afterwards, in order to assess the propensity for recurrence.

MATERIALS AND METHODS

Twenty-two human cadaveric shoulders were tested using a custom cadaveric shoulder dislocation device with simulated muscle loading. Each was positioned in the apprehension position and the humerus was moved in horizontal abduction until the shoulder dislocated. The joint reaction force was measured, as was the force that developed passively in the pectoralis major muscle. Following 3 successive dislocations, each was inspected for anterior capsulolabral lesions.

RESULTS

There was a significant decrease in force after the second dislocation. In 11, there was no labral avulsion and a significant decrease in force after the first dislocation. In the other 11, there was a labral avulsion and a significant decrease in force after the second dislocation.

CONCLUSION

Two successive anterior shoulder dislocations may increase propensity for recurrence; but this is influenced by the type of capsulolabral lesion that occurs. No labral avulsion, likely a result of capsular stretching, may be a worse prognostic finding than labral avulsion after the initial episode.

Attachment of the anteroinferior glenohumeral ligament-labrum complex to the glenoid: an anatomic study

PURPOSE

To determine the morphology of the attachment of the anteroinferior glenohumeral ligament-labrum complex (AIGHL-LC) to the anterior rim of the glenoid.

METHODS

Sixty-six cadaveric shoulders with a mean age of 81 years were studied. The length of the AIGHL-LC attachment in the superoinferior direction and its depth in the mediolateral direction at the 2-, 3-, 4-, and 5-o'clock positions were measured. The radial histologic sections from the center of the glenoid at the 2- and 4-o'clock positions were used for histologic examinations.

RESULTS

The mean length of the AIGHL-LC attachment was 11.7 mm. The mean depth was 4.7 mm (1.6 mm on the articular cartilage and 3.0 mm on the glenoid neck) at the 2-o'clock position, 6.7 mm (2.4 mm and 4.3 mm, respectively) at the 3-o'clock position, 8.4 mm (3.0 mm and 5.4 mm, respectively) at the 4-o'clock position, and 6.8 mm (2.5 mm and 4.3 mm, respectively) at the 5-o'clock position. The depth of the AIGHL-LC attachment was the greatest at the 4-o'clock position (P < .01) and the smallest at the 2-o'clock position (P < .05). Histologically, the AIGHL-LC attached to both the cartilage and bone in 52 shoulders (86.7%) at the 2-o'clock position and in 53 shoulders (88.3%) at the 4-o'clock position.

CONCLUSIONS

The depth of the AIGHL-LC attachment was the greatest at the 4-o'clock position and the smallest at the 2-o'clock position. At the 4-o'clock position, the AIGHL-LC attaches to both the articular cartilage and bone in 88% of shoulders whereas it attaches only to bone in 12%.

CLINICAL RELEVANCE

This study provides fundamental information on the AIGHL-LC attachment. Because healing of the AIGHL-LC to the articular cartilage cannot be expected, the same attachment area as to the bone and cartilage observed in normal shoulders needs to be created on the glenoid neck during Bankart repair to obtain the physiological strength of the AIGHL-LC.

Soft tissue structures resisting anterior instability in a computational glenohumeral joint model

The glenohumeral joint is the most dislocated joint in the body due to the lack of bony constraints and the dependence on soft tissue for stability. The roles that various structures provide to joint function are important for understanding injury treatment and orthopaedic device design purposes. The goal of this study was to develop a computational model of the glenohumeral joint whereby joint behaviour was dictated by articular contact, ligamentous constraints, muscle loading and external perturbations. The bone structure of the computational model consisted of assembled computer tomographic images of the scapula, humerus and clavicle. The soft tissue elements were composed of forces and tension-only springs that represented muscles and ligaments. Validation of this model was achieved by comparing computational predictions to the results of a cadaveric experiment in which the relative contribution of muscles and ligaments to anterior joint stability was examined. The computational model predicted an anterior subluxation force that was similar to the cadaveric experimental results in humeral external rotation. The individual structure results showed the subscapularis to be critical to stabilisation in both neutral and external rotations, the biceps stabilised the joint in neutral but not in external rotation, and the inferior glenohumeral ligament resisted anterior displacement only in external rotation. The model's predictions were similar to the conclusions of the cadaveric experiment and the literature. Knowledge gained from this type of model could assist in further understanding the contribution of soft tissue stabilisers to joint function, pre-operative planning or the design of orthopaedic implants.

Finding consistent strain distributions in the glenohumeral capsule between two subjects: implications for development of physical examinations

The anterior-inferior glenohumeral capsule is the primary passive stabilizer to the glenohumeral joint during anterior dislocation. Physical examinations following dislocation are crucial for proper diagnosis of capsule pathology; however, they are not standardized for joint position which may lead to misdiagnoses and poor outcomes. To suggest joint positions for physical examinations where the stability provided by the capsule may be consistent among patients, the objective of this study was to evaluate the distribution of maximum principal strain on the anterior-inferior capsule using two validated subject-specific finite element models of the glenohumeral joint at clinically relevant joint positions. The joint positions with 25 N anterior load applied at 60° of glenohumeral abduction and 10°, 20°, 30° and 40° of external rotation resulted in distributions of strain that were similar between shoulders (r² ≥ 0.7). Furthermore, those positions with 20-40° of external rotation resulted in capsule strains on the glenoid side of the anterior band of the inferior glenohumeral ligament that were significantly greater than in all other capsule regions. These findings suggest that anterior stability provided by the anterior-inferior capsule may be consistent among subjects at joint positions with 60° of glenohumeral abduction and a mid-range (20-40°) of external rotation, and that the glenoid side has the greatest contribution to stability at these joint positions. Therefore, it may be possible to establish standard joint positions for physical examinations that clinicians can use to effectively diagnose pathology in the anterior-inferior capsule following dislocation and lead to improved outcomes.

The Impact of Glenoid Labrum Thickness and Modulus on Labrum and Glenohumeral Capsule Function

The glenoid labrum is an integral component of the glenohumeral capsule’s insertion into the glenoid, and changes in labrum geometry and mechanical properties may lead to the development of glenohumeral joint pathology. The objective of this research was to determine the effect that changes in labrum thickness and modulus have on strains in the labrum and glenohumeral capsule during a simulated physical examination for anterior instability. A labrum was incorporated into a validated, subject-specific finite element model of the glenohumeral joint, and experimental kinematics were applied simulating application of an anterior load at 0 deg, 30 deg, and 60 deg of external rotation and 60 deg of glenohumeral abduction. The radial thickness of the labrum was varied to simulate thinning tissue, and the tensile modulus of the labrum was varied to simulate degenerating tissue. At 60 deg of external rotation, a thinning labrum increased the average and peak strains in the labrum, particularly in the labrum regions of the axillary pouch (increased 10.5% average strain) and anterior band (increased 7.5% average strain). These results suggest a cause-and-effect relationship between age-related decreases in labrum thickness and increases in labrum pathology. A degenerating labrum also increased the average and peak strains in the labrum, particularly in the labrum regions of the axillary pouch (increased 15.5% strain) and anterior band (increased 10.4% strain). This supports the concept that age-related labrum pathology may result from tissue degeneration. This work suggests that a shift in capsule reparative techniques may be needed in order to include the labrum, especially as activity levels in the aging population continue to increase. In the future validated, finite element models of the glenohumeral joint can be used to explore the efficacy of new repair techniques for glenoid labrum pathology.

The Bankart repair versus the Putti-Platt procedure: a randomized study with WOSI score at 10-year follow-up in 62 patients

BACKGROUND AND PURPOSE

This randomized study compared clinical results after surgery for posttraumatic shoulder instability with either an anatomical repair or an older, less anatomical but commonly used method. The less anatomical procedure has been considered quicker and less demanding, but it has been questioned regarding the clinical result. We therefore wanted to compare the clinical outcome of the two different procedures. Our hypothesis was that the anatomical repair would give less residual impairment postoperatively.

METHODS

Patients with anterior posttraumatic shoulder instability were consecutively randomized on the day before surgery to either a Bankart repair using Mitek GI/GII anchors combined with capsular imbrication (B) (n = 33) or a Putti-Platt procedure (P) (n = 33). Follow-up was performed by examination at 2 years and using a self-evaluation score at 10 years.

RESULTS

At the 2-year follow-up, we found no difference in muscle strength between patients treated with the two surgical methods and there were no statistically significant differences in the Rowe scores (mean 90 units for both groups). Compared to preoperatively, the decrease in external rotation 2 years after surgery was 10 degrees in the P group and 3 degrees in the B group (p = 0.03). 10 years after surgery, 62 of 66 patients replied to a questionnaire sent by mail. It included a self-evaluating quality of life score for shoulder instability (WOSI) for evaluation of their shoulder function. In the P group 15 patients and in the B group 19 patients reported they had experienced either a redislocation or a subluxation with a new feeling of shoulder instability. Mean WOSI score was similar in the P and B groups: 80% and 83%, respectively. The WOSI score was 87% for patients with stable shoulders (n = 28) and 77% for those with unstable shoulders (n= 34) (p = 0.005).

INTERPRETATION

With assessment of pain and general shoulder function, only a small difference was found between the two methods. The WOSI scores for stable shoulders indicated that some shoulders still had impaired function even though the shoulders had become stable.

Treating the athlete with anterior shoulder instability

Acute traumatic anterior shoulder dislocation is a relatively common occurrence in the athletic population. Although the overall incidence of traumatic shoulder instability in the general population is only 1.7%, the incidence in a high physical-demand population is two-fold greater. Instability often becomes a recurrent pattern and jeopardizes athletic performance and participation. A thorough assessment and discussion with the patient with respect to treatment decision-making are critical in the management of anterior shoulder instability.

Determination of anterior labral repair stress during passive arm motion in a cadaveric model

PURPOSE

The actual forces encountered at the labrum after anterior labral repair have yet to be quantified. The purpose of this study was to determine the amount of force experienced at the glenoid-labrum interface with passive range of motion after an isolated Bankart repair and Bankart repair with capsular shift.

METHODS

In 12 fresh-frozen cadaveric shoulders, anterior-inferior labral tears were created and then instrumented with a modified load cell. The labral lesions were repaired with either an anatomic "labral only" technique or a labral repair along with a capsular shift by use of a transglenoid technique. Shoulders were then taken through a series of movements (forward flexion, abduction, external rotation, and abduction and then external rotation) simulating passive range-of-motion rehabilitation while force measurements were taken. Maximum force (in Newtons) on the simulated repairs was recorded.

RESULTS

The forces experienced at the labrum showed a statistically significant difference between the group that underwent anatomic "labral only" repair and the group that underwent labral repair with capsular shift. The greatest mean force experienced (17.7 N) was in shoulders undergoing the labral repair with capsular shift with the arm in abduction and external rotation.

CONCLUSIONS

In a transglenoid suture repair technique, the forces experienced at the repair site were significantly less than those determined by previous authors to be necessary to result in failure of the Bankart repair. The results of this study show that the forces experienced at the glenoid-labrum interface are higher when a capsular shift is included with a labral repair as opposed to labral repair alone. This difference was statistically significant.

CLINICAL RELEVANCE

These data suggest that early postoperative rehabilitation may safely allow greater passive range of motion than is presently accepted.

Anterior shoulder instability with humeral avulsion of the glenohumeral ligament lesion

Humeral avulsion of the glenohumeral ligament (HAGL) is a rare lesion. The purpose of this study was to analyze the clinical manifestations of HAGL lesions in patients who underwent operative treatment for anterior shoulder instability. Six patients with HAGL lesions were studied. Four patients had an HAGL lesion associated with a Bankart lesion, and two had an isolated HAGL lesion. The range of motion at final follow-up showed a loss of 1 degree in forward flexion and of 15 degrees in external rotation. During an operation to treat anterior shoulder instability, a thorough examination for not only Bankart lesions but also other associated lesions, including an HAGL lesion, should be considered to lower the risk of redislocation. In repairing an HAGL lesion, the surgeon should keep in mind the possibility of a postoperative loss of external rotation and follow an active rehabilitation protocol to obtain successful results.

Cervical facet capsular ligament yield defines the threshold for injury and persistent joint-mediated neck pain

The cervical facet joint has been identified as a source of neck pain, and its capsular ligament is a likely candidate for injury during whiplash. Many studies have shown that the mechanical properties of ligaments can be altered by subfailure injury. However, the subfailure mechanical response of the facet capsular ligament has not been well defined, particularly in the context of physiology and pain. Therefore, the goal of this study was to quantify the structural mechanics of the cervical facet capsule and define the threshold for altered structural responses in this ligament during distraction. Tensile failure tests were preformed using isolated C6/C7 rat facet capsular ligaments (n=8); gross ligament failure, the occurrence of minor ruptures and ligament yield were measured. Gross failure occurred at 2.45+/-0.60 N and 0.92+/-0.17 mm. However, the yield point occurred at 1.68+/-0.56 N and 0.57+/-0.08 mm, which was significantly less than gross failure (p<0.001 for both measurements). Maximum principal strain in the capsule at yield was 80+/-24%. Energy to yield was 14.3+/-3.4% of the total energy for a complete tear of the ligament. Ligament yield point occurred at a distraction magnitude in which pain symptoms begin to appear in vivo in the rat. These mechanical findings provide insight into the relationship between gross structural failure and painful loading for the facet capsular ligament, which has not been previously defined for such neck injuries. Findings also present a framework for more in-depth methods to define the threshold for persistent pain and could enable extrapolation to the human response.

The inferior glenohumeral ligament: a correlative investigation

The inferior glenohumeral ligament (IGHL) was investigated by correlating the biomechanical properties, biochemical composition, and histologic morphology of its 3 anatomic regions (superior band, anterior axillary pouch, and posterior axillary pouch) in 8 human cadaveric shoulders. The overall biochemical composition of the IGHL appeared similar to other ligaments, with average water content of 80.9 +/- 2.5%, collagen content of 80.0 +/- 9.2%, and crosslinks of 0.715 +/- 0.13 mol/mol collagen. The proteoglycan content was highest in the superior band (2.73 +/- 0.7 mg/g dry weight) and may, in part, explain its viscoelastic behavior. Histologic analysis demonstrated longitudinally organized fiber bundles that were more uniform in the mid-substance but more interwoven and less uniformly oriented near the insertion sites. The superior band had the most pronounced fiber bundle interweaving, while crimping was more evident in the anterior axillary pouch. Elastin was identified in each of the regions. Tensile testing demonstrated a trend toward higher ultimate tensile stress (16.9 +/- 7.9 MPa) and tensile modulus (130.3 +/- 47.9 MPa) in the superior band compared to the axillary pouch. The mean ultimate tensile strain of the IGHL was 16.8 +/- 4.6%. These complex IGHL properties may help to explain its unique functions in stabilizing the shoulder in different arm positions and at different rates of loading, including the failure patterns seen clinically, as in Bankart lesions (insertion site) versus capsular stretching (ligament substance).

Clinical outcome of anterior shoulder instability with capsular midsubstance tear: a comparison of isolated midsubstance tear and midsubstance tear with Bankart lesion

To analyze the clinical outcomes of patients with a midsubstance capsular tear for anterior shoulder instability, 21 shoulders with a midsubstance tear were reviewed. There were 7 isolated midsubstance tears (group I) and 14 combined midsubstance tears with Bankart lesions (group II). The Rowe score averaged 92.3 points with 6 excellent and 1 good one in group I. Group II scored 86.3 points with 8 excellent, 3 good, 2 fair, and 1 poor (P = .184). The Rowe score averaged 89.8 points for the cases with an arthroscopic procedure and 86.9 points with an open repair (P = .542). At the last follow-up, forward elevation increased by 6 degrees in group I and 8 degrees in group II (P = .432). External rotation decreased by 8 degrees and 16 degrees , respectively (P = .150). The clinical outcomes of anterior instability with a midsubstance tear were good in both groups. The loss of external rotation was greater in the cases with combined midsubstance tears and Bankart lesions than in those with an isolated midsubstance tear.

Risk factors for recurrence of shoulder instability after arthroscopic Bankart repair

BACKGROUND

The higher failure rates reported with arthroscopic stabilization of traumatic, recurrent anterior shoulder instability compared with open stabilization remain a concern. The purpose of this study was to evaluate the outcomes of arthroscopic Bankart repairs with the use of suture anchors and to identify risk factors related to postoperative recurrence of shoulder instability.

METHODS

Ninety-one consecutive patients underwent arthroscopic stabilization for recurrent anterior traumatic shoulder instability. The mean age (and standard deviation) at the time of surgery was 26.4 +/- 5.4 years. Seventy-one patients were male. Seventy-nine patients were involved in sports (forty, in high-risk sports). Capsulolabral reattachment and capsule retensioning was performed with use of absorbable suture anchors (mean, 4.3 anchors; range, two to seven anchors). All patients were prospectively followed, and, at the time of the last review, the patients were examined and assessed functionally by independent observers.

RESULTS

At a mean follow-up of thirty-six months, fourteen patients (15.3%) experienced recurrent instability: six sustained a frank dislocation and eight reported a subluxation. The mean delay to recurrence was 17.6 months. The risk of postoperative recurrence was significantly related to the presence of a bone defect, either on the glenoid side (a glenoid compression-fracture; p = 0.01) or on the humeral side (a large Hill-Sachs lesion; p = 0.05). By contrast, a glenoid separation-fracture was not associated with postoperative recurrent dislocation or subluxation. Recurrence of instability was significantly higher in patients with inferior shoulder hyperlaxity (p = 0.03) and/or anterior shoulder hyperlaxity (p = 0.01). On multivariate analysis, the presence of glenoid bone loss and inferior hyperlaxity led to a 75% recurrence rate (p < 0.001). Lastly, the number of suture-anchors was critical: patients who had three anchors or fewer were at higher risk for recurrent instability (p = 0.03).

CONCLUSIONS

In the treatment of traumatic recurrent anterior shoulder instability, patients with bone loss or with shoulder hyperlaxity are at risk for recurrent instability after arthroscopic Bankart repair. At least four anchor points should be used to obtain secure shoulder stabilization.

Simulated capsulolabral lesion in cadavers: dislocation does not result from a bankart lesion only

PURPOSE

Although an anteroinferior capsulolabral detachment (typical Bankart lesion) has been evaluated in other experimental studies, it has not yet been tested with an apprehension test in an intact shoulder model.

METHODS

Adjacent combinations of 4 zones of the capsuloligamentous complex were sequentially detached from the glenoid neck in 50 cadaveric shoulders. Stability was tested before and after each resection step: inferior stability with a sulcus test and anterior stability with an anterior drawer test and with a load-and-shift test in the apprehension position.

RESULTS

A metastable anteroinferior dislocation occurred in 18 specimens after section of 3 zones and in 14 only after section of 4 zones. A locked dislocation occurred after section of all 4 zones in 33 specimens and in the other 17 shoulders only after the posterior capsule was also cut.

CONCLUSIONS

The humeral head cannot dislocate anteroinferiorly when there only is a Bankart lesion. In our study superior and posterior extension was necessary before the tensioning mechanism in external rotation and abduction failed enough for dislocation to occur.

CLINICAL RELEVANCE

Because the Bankart lesion is most likely not the only lesion present in patients with recurrent dislocation, a careful search for other lesions needs to be done when one is attempting surgical treatment. These lesions would need to be treated as well if one wants to avoid the risk of residual instability.

Arthroscopic anterior stabilization and posterior capsular plication for anterior glenohumeral instability: a report of 71 cases

PURPOSE

Results after arthroscopic treatment of anterior glenohumeral instability continue to improve as advancements are made in instrumentation and techniques. We present 71 cases of anterior glenohumeral instability treated with arthroscopic anterior stabilization and posterior capsular plication.

TYPE OF STUDY

Case series.

METHODS

Arthroscopic anterior reconstruction and posterior inferior "pinch-tuck" capsular plication was performed in 71 shoulders (67 patients) with anterior glenohumeral instability. The average follow-up was 33.3 months (range, 20 to 24 months). Outcomes were assessed by completion of the Simple Shoulder Test (SST), Western Ontario Shoulder Instability (WOSI) Index, a Rowe score, and a subjective self-assessment shoulder instability form.

RESULTS

Postoperative dislocation occurred in 5 patients (7%). The average SST score was 11.2 (12 maximum) and the average WOSI Index was 85.6% (range, 30.6% to 100%). The average Rowe score was 85. Ninety-seven percent of patients reported they were able to return to their normal activity level, and 90% of patients reported that they were able to return to their previous level of athletics; 100% of patients reported that they were doing better than before surgery and were satisfied with their result; 100% of patients reported that they would undergo the procedure again.

CONCLUSIONS

Arthroscopic anterior stabilization using suture anchors, combined with posterior capsular suture plication, is a reliable treatment option for anterior glenohumeral instability.

LEVEL OF EVIDENCE

Level IV.

Biomechanical comparison of a single-row versus double-row suture anchor technique for rotator cuff repair

BACKGROUND

Reestablishment of the native footprint during rotator cuff repair has been suggested as an important criterion for optimizing healing potential and fixation strength.

HYPOTHESIS

A double-row rotator cuff footprint repair will demonstrate superior biomechanical properties compared with a single-row repair.

STUDY DESIGN

Controlled laboratory study.

METHODS

In 9 matched pairs of fresh-frozen cadaveric shoulders, the supraspinatus tendon from 1 shoulder was repaired with a double-row suture anchor technique: 2 medial anchors with horizontal mattress sutures and 2 lateral anchors with simple sutures. The tendon from the contralateral shoulder was repaired using a single lateral row of 2 anchors with simple sutures. Each specimen underwent cyclic loading from 10 to 180 N for 200 cycles, followed by tensile testing to failure. Gap formation and strain over the footprint area were measured using a video digitizing system; stiffness and failure load were determined from testing machine data.

RESULTS

Gap formation for the double-row repair was significantly smaller (P < .05) when compared with the single-row repair for the first cycle (1.67 +/- 0.75 mm vs 3.10 +/- 1.67 mm, respectively) and the last cycle (3.58 +/- 2.59 mm vs 7.64 +/- 3.74 mm, respectively). The initial strain over the footprint area for the double-row repair was nearly one third (P < .05) the strain of the single-row repair. Adding a medial row of anchors increased the stiffness of the repair by 46% and the ultimate failure load by 48% (P < .05).

CONCLUSION

Footprint reconstruction of the rotator cuff using a double-row repair improved initial strength and stiffness and decreased gap formation and strain over the footprint when compared with a single-row repair.

CLINICAL RELEVANCE

To achieve maximal initial fixation strength and minimal gap formation for rotator cuff repair, reconstructing the footprint attachment with 2 rows of suture anchors should be considered.

Innervation patterns of the inferior glenohumeral ligament: Anatomical and biomechanical relevance

Although the Inferior Glenohumeral Ligament (IGHL) has a well known mechanical and proprioceptive relevance in shoulder stability, the interrelation of the ligament's anatomical disposition/innervation has not actually been described previously. The purpose of the study was to determine the IGHL innervation patterns and relate them to dislocation. Forty-five embalmed and 16 fresh-frozen human cadaveric shoulders were studied. Masson's Trichrome staining detailed the intraligamentous nerve fiber arrangements. The effect on the articular nerves of an anteroinferior dislocation of the shoulder joint and the position of 60 degrees abduction and 45 degrees external rotation was studied dynamically. The axillary nerve provided IGHL innervation in 95.08% of the cases. We saw two distinct innervation patterns originating from the axillary nerve. In Type 1, one or two collaterals diverged later from the main trunk to enter the ligament. Type 2 showed innervation to the ligament provided by the posterior branch for three to four neural branches. In both cases, these branches enter the ligament near the glenoid rim and at the 7 o'clock position (right shoulder). The radial nerve (Type 3 innervation pattern) provided IGHL innervation in 3.28% of the cases. Microscopic analysis revealed wavy intraligamentous neural branches. The articular branches relaxed and separated from the capsule at the apprehension position and stayed intact after dislocation. These results showed a special predisposition to avoid possible denervation and suggested that the neural arch probably remains unaffected after most dislocations. Knowledge of the neural anatomy of the shoulder will clearly help in avoiding its injury in surgical procedures.

Bi-directional mechanical properties of the posterior region of the glenohumeral capsule

The objective of this study was to determine the mechanical properties of the posterior region of the glenohumeral capsule in the directions perpendicular (transverse) and parallel (longitudinal) to the longitudinal axis of the posterior band of the inferior glenohumeral ligament. A punch was used to excise one transverse and one longitudinal tissue sample from the posterior capsule of 11 cadaveric shoulders. All tissue samples exhibited the typical nonlinear behavior reported for ligaments and tendons. Significant differences (p < 0.05) were detected between the transverse and longitudinal tissue samples for ultimate stress (1.5+/-1.4 and 4.9+/-2.9 MPa, respectively) and tangent modulus (10.3+/-6.6 and 31.5+/-12.7 MPa, respectively). No significant differences (p > 0.05) were observed between the ultimate strain (transverse: 22.3+/-12.5%, longitudinal: 22.8+/-11.1%) and strain energy density (transverse: 27.2+/-52.8 MPa, longitudinal: 67.5+/-88.2 MPa) of the transverse and longitudinal tissue samples. The ratio of the longitudinal to transverse moduli (4.8+/-4.2) was similar to that found for the axillary pouch (3.3+/-2.8) in a previous study. Thus, both the axillary pouch and the posterior capsule function to stabilize the joint multi-axially. Future analytical models of the glenohumeral joint should consider the properties of the posterior capsule in its transverse and longitudinal directions to fully describe the behavior of the glenohumeral capsule. These models will be clinically important by providing a more accurate representation of the intact capsule as well as simulated capsular injuries and surgical repair procedures.

Pathomechanics of acquired shoulder instability: a basic science perspective

Normal asymptomatic glenohumeral motion is dependent on the coordinated function of dynamic and static stabilizers. Data from both selective sectioning studies of the capsuloligamentous components and tensile testing of the inferior glenohumeral ligament have provided important insights into the in situ function of these structures. However, little is known regarding the mechanism of microdamage accumulation in acquired shoulder instability. Recent findings suggest that cyclic subfailure loading of the inferior glenohumeral ligament may induce gradual stretching of the anteroinferior capsule, compromising its capacity to restrain excessive humeral translations. Further studies elucidating the mechanism of load transmission in the capsule during physiologic arm motion, as well as data on the intrinsic healing response of the capsular ligaments, are required to more fully characterize the pathoetiology of acquired shoulder instability.

Active stability of the glenohumeral joint decreases in the apprehension position

BACKGROUND

Muscle forces that compress the glenohumeral joint during mid-ranges of motion may lead to increased translational forces in end-range positions, such as the apprehension position, where symptoms of anterior instability occur.

OBJECTIVE

The objective of this study was to quantify active stability provided by eight shoulder muscles in mid-range and end-range positions through muscle force vector analysis.

METHODS

Lines of action were derived from a geometric model and muscle force magnitudes were estimated with electromyography-based techniques. Resultant muscle force vectors were calculated by summing individual muscle force vectors.

RESULTS

Compared to mid-range positions, lines of action of resultant force vectors were more anteriorly directed in end-range positions compared to 15 degrees of abduction, up to 26 degrees. Consequently, anterior stability was lowest in the apprehension position. The magnitudes of the resultant force vectors were comparable to other studies. Based on a sensitivity analysis, lines of action of resultant force vectors vary up to 6 degrees within the population.

CONCLUSIONS

Data obtained from this model will improve conservative management, post-surgical rehabilitation, and strength training protocols.

Excessive humeral external rotation results in increased shoulder laxity

BACKGROUND

The quantitative relationship between increased anterior shoulder laxity and increased humeral external rotation observed in throwers remains unclear.

HYPOTHESIS

An elongated anterior capsule, especially the anterior band of the inferior glenohumeral ligament, produced by excessive humeral external rotation will result in increased anterior shoulder laxity and increased humeral external rotation.

STUDY DESIGN

Controlled laboratory study.

METHODS

Seven cadaveric shoulders were tested to measure the humeral rotational range of motion, glenohumeral translations, and length of the anterior band of the inferior glenohumeral ligament. Data were collected for the intact shoulders and after nondestructive stretching of 10%, 20%, and 30% beyond maximum humeral external rotation.

RESULTS

Nondestructive excessive external rotational stretching resulted in a significant increase in superior (30%, 3.3 mm) and inferior (30%, 2.3 mm) length of the anterior band of the inferior glenohumeral ligament, external rotation (30%, 35 degrees), and anterior (30%, 2.4 mm), inferior (30%, 2.2 mm), and anterior-posterior (30%, 5.1 mm) translations. There were significant positive linear correlations between the length of the anterior band of the inferior glenohumeral ligament, external rotation, and anterior translation.

CONCLUSIONS

Excessive humeral external rotation results in an elongation of the anterior band of the inferior glenohumeral ligament and an increase in anterior and inferior glenohumeral translations and humeral external rotation.

CLINICAL RELEVANCE

Repetitive excessive humeral external rotation observed in throwers may be one of the biomechanical causes for increased shoulder laxity and increased humeral external rotation.

Diagnosis and Management of the Painful Shoulder. Part 2: Examination, Interpretation, and Management

Diagnosis, interpretation and subsequent management of shoulder pathology can be challenging to clinicians. Because of its proximal location in the schlerotome and the extensive convergence of afferent signals from this region to the dorsal horn of the spinal cord, pain reference patterns can be broadly distributed to the deltoid, trapezius, and or the posterior scapular regions. This pain behavior can make diagnosis difficult in the shoulder region, as the location of symptoms may or may not correspond to the proximity of the pain generator. Therefore, a thorough history and reliable physical examination should rest at the center of the diagnostic process. Effective management of the painful shoulder is closely linked to a tissue-specific clinical examination. Painful shoulder conditions can present with or without limitations in passive and or active motion. Limits in passive motion can be classified as either capsular or noncapsular patterns. Conversely, patients can present with shoulder pain that demonstrates no limitation of motion. Bursitis, tendopathy and rotator cuff tears can produce shoulder pain that is challenging to diagnose, especially when they are the consequence of impingement and or instability. Numerous nonsurgical measures can be implemented in treating the painful shoulder, reserving surgical interventions for those patients who are resistant to conservative care.

Effect of selective capsulorrhaphy on the passive range of motion of the glenohumeral joint

BACKGROUND

Capsulorrhaphy of the glenohumeral joint is a common surgical procedure for the treatment of instability caused by increased capsular laxity. The effect of capsulorrhaphy on the range of motion of the shoulder is poorly understood.

METHODS

We simulated localized capsular contractures by selective capsular plications in eight human cadaveric shoulders and studied the effect of such plications on the passive range of glenohumeral abduction, flexion, and external and internal rotation in different degrees of abduction. A 0.5 or 1-N-m torque was applied to the humerus, and the range of glenohumeral motion was measured with electronic goniometers in three planes and compared with those of the intact shoulder.

RESULTS

Anterosuperior capsular plication most markedly affected external rotation of the adducted arm, decreasing it by a mean of 30.1 degrees (p < 0.0001). Anteroinferior plication significantly reduced abduction by a mean of 19.4 degrees (p < 0.0001) and external rotation by a mean of 20.6 degrees (p = 0.0046). Posterosuperior plication mostly limited internal rotation of the adducted arm (mean decrease, 16.1 degrees, p = 0.0045). On the average, total anterior and total posterior plication each limited flexion by approximately 20 degrees (p = 0.005) and abduction by >or=15 degrees (p < 0.005), whereas total anterior plication limited external rotation by >30 degrees (p <or= 0.0002) and total posterior plication limited internal rotation by >20 degrees (p < 0.0001). Total inferior capsular plication restricted abduction (by a mean of 27.7 degrees, p = 0.0001), flexion, and rotation. Total superior plication restricted external rotation and flexion.

CONCLUSIONS AND CLINICAL RELEVANCE

Localized plications of the glenohumeral joint capsule lead to predictable patterns of loss of glenohumeral mobility. If plication is planned, losses of movement can be anticipated. The findings of this study may assist surgeons in identifying the parts of the capsule that are contracted and that may need lengthening.

Capsular elongation in shoulders with recurrent anterior dislocation. Quantitative assessment with magnetic resonance arthrography

BACKGROUND

Elongation of the shoulder capsule is often noticed on arthrograms or during surgery in shoulders of patients who have experienced recurrent anterior dislocations.

HYPOTHESIS

We can quantify the elongation of the capsule in shoulders with recurrent anterior dislocations by using magnetic resonance arthrography.

STUDY DESIGN

Retrospective review of prospectively collected data.

METHODS

Twelve patients with unilateral recurrent anterior shoulder dislocations were enrolled in this study. Magnetic resonance images in the axial and coronal oblique planes were obtained from both shoulders (involved and uninvolved sides) after 10 ml of gadolinium/saline solution was injected into the glenohumeral joint. The length of the anteroinferior, inferior, and posteroinferior portions of the capsule was measured by using image analyzing software and normalized to the humeral head diameter.

RESULTS

The anteroinferior capsule was significantly elongated in the involved shoulder at 4 mm (16% elongation) and 10 mm (19% elongation) superior to the inferior margin of the glenoid. The inferior capsule was also significantly elongated in the involved side both at the center (12% elongation) and at 4 mm anterior to the center of the glenoid (29% elongation). The posteroinferior capsule did not show any significant elongation.

CONCLUSIONS

The anteroinferior and inferior portions of the shoulder capsule are elongated an average of 19% in shoulders with recurrent anterior dislocation.

Preoperative magnetic resonance imaging diagnosis of the floating anterior inferior glenohumeral ligament

Approximately a century ago, labral avulsion from the glenoid was described as a source of recurrent anterior shoulder dislocation. Since then, the significance of other origins of shoulder instability has been a controversial issue. Cadaveric dissection, biomechanical evaluation, and surgical observation have led to the discovery of additional pathologic conditions associated with glenohumeral instability that must be properly identified and addressed for operative success. Recently, several authors have emphasized the importance of lesions of the glenohumeral ligament as a cause of post-traumatic shoulder instability. One such condition is bipolar avulsion of the anterior inferior glenohumeral ligament (AIGHL), or floating AIGHL. In previous reports, this finding has only been identified during surgery. We present a case of traumatic anterior shoulder dislocation in which a preoperative diagnosis of floating AIGHL was made by magnetic resonance imaging. Recognition of this rare lesion before surgical intervention is advantageous for appropriate preoperative planning and management of patients with posttraumatic anterior glenohumeral instability.

Deformation and strain characteristics along the length of the anterior band of the inferior glenohumeral ligament

Efficacious surgical treatment of anterior glenohumeral instability often requires repair of the anteroinferior capsulolabral structures, including the glenoid origin of the anterior band of the inferior glenohumeral ligament. Rupture in this location, the Bankart lesion, may be accompanied by nonrecoverable stretching of the anterior band. The purpose of this study was to evaluate the amount and location of nonrecoverable stretching with tensile testing. Twelve glenoid-soft tissue-humerus complexes from fresh-frozen glenohumeral joints were studied by means of a custom jig, an Instron machine, and a video digitizing system. The joints were positioned to simulate that known to cause apprehension for anterior instability. Nonrecoverable deformation differed along the length of the anterior band but was slight in all locations. For those that failed at the glenoid insertion region, the mean nonrecoverable deformation was 0.10 +/- 0.16 mm (mean +/- SEM) at the bone-labral junction of the glenoid insertion region and 0.38 +/- 0.23 mm at the labral-ligament junction of the glenoid insertion region. It was 0.53 +/- 0.23 mm at the ligament midsubstance and 0.04 +/- 0.10 mm at the humeral insertion region. For those that failed at the glenoid insertion region, the nonrecoverable stretching was 1.4% +/- 1.9% at the bone-labral junction of the glenoid insertion region and 3.5% +/- 2.0% at the labral-ligament junction of the glenoid insertion region. It was 2.3% +/- 1.1% at the ligament midsubstance and 0.0% +/- 1.4% at the humeral insertion region. Rupture of the anterior band resulted in little nonrecoverable stretching at both the site of failure and elsewhere along the length, remote from the failure site. Surgical repairs after initial dislocation may restore the length of the anterior band of the inferior glenohumeral ligament with little shortening.

Anatomical composition of the anterior shoulder joint capsule. A cadaver study on 12 glenohumeral joints

Twelve right cadaver shoulder joints were investigated after alcohol-formalin-glycerol fixation. The tendons of the "rotator cuff" were separated from the joint capsule. The capsulo-ligamentous structures: Lig. coracohumerale, Lig. coracoglenoidale and Ligg. glenohumeralia were dissected. In addition to the Ligg. glenohumerale superius, medium et inferius, an "unknown glenohumeral ligament" coursed in the midline of the superficial layer of the anterior shoulder joint capsule. It arose from the axillary part of the Lig. glenohumerale inferius and the insertion tendon of the Caput longum m. tricipitis brachii, coursed upwards laterally and fused with the Lig. glenohumerale medium. Between the Ligg. glenohumerale medium et inferius it was connected with the shoulder joint capsule by loose connective tissue. Craniolaterally it melted into the superior portion of the M. subscapularis and inserted together with its tendon to the Tuberculum minus of the Humerus. The ascending fibres of the "unknown glenohumeral ligament" and the oblique, descending fibres of the Ligg. glenohumeralia medium et inferius crossed twice and formed X-shape connections between the ligaments. In external rotation and abduction or anteversion the course of fibres of the "unknown glenohumeral ligament" was spiral. According to the shape and anatomical position of the "unknown glenohumeral ligament" we propose to name it "Lig. glenohumerale spirale".