The biomechanical influence of the deltotrapezoid fascia on horizontal and vertical acromioclavicular joint stability

Does glenoid inclination affect the anterior stability of reverse total shoulder arthroplasty? A biomechanical study

PURPOSE

The anterior stability of reverse total shoulder arthroplasty is affected by multiple factors. However, the effect of glenosphere inclination on stability has rarely been investigated, which is what this study aims to look into.

METHODS

Reverse shoulder arthroplasty was performed on 15 cadaveric human shoulders. The anterior dislocation forces and range of motion in internal rotation in the glenohumeral joint (primary measured parameters) were tested in a shoulder simulator in different arm positions and implant configurations, as well as with a custom-made 10° inferiorly inclined glenosphere. The inclination and retroversion of the baseplate as well as the distance between the glenoid and coracoid tip in two planes (secondary measured parameters) were evaluated on CT scans.

RESULTS

In biomechanical testing, the custom-made inclined glenosphere showed no significant influence on anterior stability other than glenoid lateralisation over all arm positions as well as the neck-shaft angle in two arm positions. The 6 mm lateralised glenosphere reduced internal rotation at 30° and 60° of glenohumeral abduction. In 30° of glenohumeral abduction, joint stability was increased using the 155° epiphysis compared with the 145° epiphysis. The mean inclination was 16.1°. The inclination was positively, and the distance between the glenoid and coracoid tip in the anterior-to-posterior direction was negatively correlated with anterior dislocation forces.

CONCLUSIONS

The custom-made inferiorly inclined glenosphere did not influence anterior stability, but baseplate inclination itself had a significant effect on stability.

Presurgical perspective and postsurgical evaluation of acromioclavicular joint instability

Acromioclavicular joint (ACJ) dislocations are a common cause of pain in patients of any age. Athletes who participate in contact sports, such as hockey, football, rugby, and soccer, are particularly susceptible to such injuries. The ACJ has an important role in the function of the upper limb, and its complexity of movement makes it susceptible to acute injuries and chronic dysfunction with debilitating effects that must be treated appropriately and promptly to preserve function. Recently, ACJ has received increasing attention due to the development of new surgical techniques for the restoration of normal function and stability. There is some agreement about the treatment of ACJ dislocations, but controversy remains about the treatment of Rockwood grade III dislocations, and a new approach to these injuries is suggested by ISAKOS. Overall, the paper summarizes new concepts in the anatomy of the ACJ and reviews the utility of imaging methods in ACJ dislocations as well as their treatment and complications.

Acromioclavicular Joint Anatomy and Biomechanics: The Significance of Posterior Rotational and Translational Stability

The shoulder girdle extends from the sternoclavicular joint to the scapular stabilizing muscles posteriorly. It consists of 3 joints and 2 mobile regions. The shoulder girdle is statically stabilized by the acromioclavicular and coracoclavicular capsuloligamentous structures and dynamically stabilized by the trapezius, deltoid, and deltotrapezial fascia. During humerothoracic elevation, the clavicle elevates, protracts, and rotates posteriorly through the sternoclavicular joint while the scapula tilts posteriorly and rotates upward. The purpose of this article is to review the anatomy and biomechanics of the acromioclavicular joint and the shoulder girdle.

Dynamic Horizontal Instability of the Acromioclavicular Joint: A Case Report

CASE

A 19-year-old female patient with a history of shoulder trauma 6 years ago presented with dynamic horizontal instability of the acromioclavicular joint (ACJ). She was treated with open ACJ reconstruction using gracilis allograft and showed a satisfactory clinical result at 1-year follow-up.

CONCLUSION

Dynamic pure horizontal instability of the ACJ is a rare entity with only 6 cases reported in the literature. Till now, all reported patients who necessitated surgical treatment failed because of residual instability and/or pain. We present the seventh case of this type with a successful clinical outcome.

Deltotrapezial Stabilization of Acromioclavicular Joint Rotational Stability: A Biomechanical Evaluation

Background

Despite advances in surgical management of acromioclavicular (AC) joint reconstruction, many patients fail to maintain sustained anatomic reduction postoperatively.

Purpose

To determine the biomechanical support of the deltoid and trapezius on AC joint stability, focusing on the rotational stability provided by the muscles to posterior and anterior clavicular rotation. A novel technique was attempted to repair the deltoid and trapezius anatomically.

Study Design

Controlled laboratory study.

Methods

Twelve human cadaveric shoulders (mean ± SD age, 60.25 ± 10.25 years) underwent servohydraulic testing. Shoulders were randomly assigned to undergo serial defects to either the deltoid or trapezius surrounding the AC joint capsule, followed by a combined deltotrapezial muscle defect. Deltotrapezial defects were repaired with an all-suture anchor using an anatomic technique. The torque (N·m) required to rotate the clavicle 20° anterior and 20° posterior was recorded for the following conditions: intact (native), deltoid defect, trapezius defect, combined deltotrapezial defect, and repair.

Results

When compared with the native condition, the deltoid defect decreased the torque required to rotate the clavicle 20° posteriorly by 7.1% (P = .206) and 20° anteriorly by 6.1% (P = .002); the trapezial defect decreased the amount of rotational torque posteriorly by 5.3% (P = .079) and anteriorly by 4.9% (P = .032); and the combined deltotrapezial defect decreased the amount of rotational torque posteriorly by 9.9% (P = .002) and anteriorly by 9.4% (P < .001). Anatomic deltotrapezial repair increased posterior rotational torque by 5.3% posteriorly as compared with the combined deltotrapezial defect (P = .001) but failed to increase anterior rotational torque (P > .999). The rotational torque of the repair was significantly lower than the native joint in the posterior (P = .017) and anterior (P < .001) directions.

Conclusion

This study demonstrated that the deltoid and trapezius play a role in clavicular rotational stabilization. The proposed anatomic repair improved posterior rotational stability but did not improve anterior rotational stability as compared with the combined deltotrapezial defect; however, neither was restored to native stability.

Clinical Relevance

Traumatic or iatrogenic damage to the deltotrapezial fascia and the inability to restore anatomic deltotrapezial attachments to the acromioclavicular joint may contribute to rotational instability. Limiting damage and improving the repair of these muscles should be a consideration during AC reconstruction.

Kinematic analysis of scapulothoracic movements in the shoulder girdle: a whole cadaver study

Background

Existing kinematic studies of the shoulder girdle focus on humerothoracic movements. Isolated scapulothoracic movements are also performed during daily activities and rehabilitation but kinematic values are lacking.

Methods

A kinematic analysis was performed in 14 cadaveric shoulders during protraction, retraction, and shrug. An optical navigation system was used to analyze sternoclavicular, scapulothoracic, and acromioclavicular motions.

Results

In the sternoclavicular joint, shrug and retraction caused a posterior clavicular rotation of 5° (standard deviation [SD] 6°) and 3° (SD 2°), while protraction induced an anterior rotation of 3° (SD 2°). Shrug caused a large clavicular elevation of 25° (SD 5°). Shrug and retraction caused an increase in retraction of 17° (SD 5°) and 9° (SD 2°). Protraction induced an increase of 10° (SD 2°) toward protraction. In the scapulothoracic joint, shrug induced an increase of 3° (SD 2°) in anterior scapular tilt, and a lateral rotation of 26° (SD 4°). Retraction caused a lateral rotation of 4° (SD 3°). Protraction caused an increase of 7° (SD 2°) in the scapular protraction position, while shrug and retraction demonstrated a decrease of 9° (SD 2°) and 6° (SD 5°). In the acromioclavicular joint, posterior tilting of the scapula compared to the clavicle increased 23° (SD 6°) during shrug, while during protraction an increase of only 4° (SD 3°) was seen. During shrug, relative lateral rotation increased 13° (SD 4°). The protraction movement decreased the relative protraction position with 3° (SD 2°).

Conclusion

This study provided normative kinematic values of scapulothoracic movements in the shoulder girdle.

Clinical and radiological outcome of acute high-grade acromioclavicular joint dislocation: A retrospective cohort study on Hook plate versus arthroscopic assisted single coracoclavicular tunnel with DogBone™ button dual FiberTape® construct

Purpose

Hook plate (HP) is a popular implant of choice in the management of highgrade acute acromioclavicular joint (ACJ) dislocations. Recently, suspensory loop systems have drawn significant interest with comparable results and additionally does not warrant implant removal. However, no studies have compared the outcomes of HP vis-a-vis Dog Bone TM Button with dual FiberTape® (DB).

Methods

38 patients who underwent HP or Arthroscopic assisted single tunnel DB fixation to stabilize high-grade ACJ dislocations were retrospectively included in study for clinically and radiological evaluation at a minimum follow up of one year. American Shoulder and Elbow Society and Constant Murley scores were used for clinical assessment. The radiological evaluation was done by assessing quality of reduction, measuring coracoclavicular distance (CCD), and extent of subacromial erosion.

Results

For final follow up evaluation, both HP and DB group had 16 patients each. The mean follow-up was 55.38 ± 10.9 and 32.88 ± 14.0 months in HP and DB group, respectively. No significant difference in mean ASES (p=0.71) and CM score (p=0.62) was found between the two groups. The DB group revealed higher CCD at the final follow-up compared to the HP group (p=0.01). Although statistically insignificant, there were more subluxations and dislocations in the DB group (37.5%) compared to the HP group (25%). The subacromial erosion was noted in all cases of the HP group at time of implant removal.

Conclusion

Both groups revealed satisfactory functional and radiological outcome. However, the DB group showed a higher tendency of loss of reduction.

Three-Dimensional Footprint Mapping of the Deltoid and Trapezius: Anatomic Pearls for Acromioclavicular Joint Reconstruction

PURPOSE

To perform a quantitative anatomic evaluation of the deltoid and trapezius footprints in relation to the lateral clavicle and acromioclavicular (AC) joint capsule to assist in surgical technique of AC joint reconstructions.

METHODS

Fourteen fresh-frozen human cadaveric shoulders from 9 donors were analyzed. Meticulous dissection of the deltoid origin and trapezius insertions to the clavicle and AC joint was performed. Footprints were reconstructed using a MicroScribe digitizer. The inferior extension of the deltoid origin beneath the lateral clavicle and the footprints of the deltoid and trapezius onto the acromioclavicular ligamentous complex (ACLC) were quantified. Reproducibility was assessed by redigitizing 5 shoulders in a blinded and random fashion.

RESULTS

The anterior deltoid fibers extended on average 4.0 ± 1.6 mm inferiorly with respect to the anteroinferior clavicular ridge and attached to 90.9 ± 7.3% of the anterior ACLC. The trapezius inserted onto the posterior and superior ACLC, covering 15.3 ± 3.4% of the anterior-posterior width of the superior capsule. The deltopectoral interval was 6 cm, or 37% the length of the clavicle from the distal end of the clavicle.

CONCLUSIONS

The deltoid has superior, anterior, and not as well described, inferior attachments to the lateral clavicle. Furthermore, the deltoid and trapezius muscles have intimate attachments to the AC joint capsule, particularly the trapezius to the posterior and posterosuperior capsule. Lastly, the deltoid origin attaches to the lateral 6 cm of the clavicle.

CLINICAL RELEVANCE

Subperiosteal elevation of the deltoid off the lateral clavicle starting superiorly, anteriorly, and lastly inferiorly will reduce deltoid muscle injury and improve visibility of the coracoid process during reconstruction. Furthermore, knowledge of the attachments of the deltoid and trapezius to the ACLC may help limit iatrogenic injury to these dynamic stabilizers.

Kinematic Alterations in the Shoulder Complex in Rockwood V Acromioclavicular Injuries During Humerothoracic and Scapulothoracic Movements: A Whole-Cadaver Study

BACKGROUND

Previous cadaveric kinematic studies on acromioclavicular injuries described mainly rotational differences during humerothoracic movements. Although isolated scapulothoracic movements are also often performed during activities of daily life and can be painful after acromioclavicular injuries, they have not been extensively studied. Further, the analysis of joint translations in kinematic studies has received little attention compared with biomechanical studies.

HYPOTHESIS

A kinematic analysis of joint motions in the intact shoulder versus a shoulder with Rockwood V injury would demonstrate a different pattern of kinematic alterations during humerothoracic and scapulothoracic movements.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A kinematic analysis was performed in 14 cadaveric shoulders during 3 humerothoracic passive movements (coronal and sagittal plane elevation and horizontal adduction) and 3 scapulothoracic passive movements (protraction, retraction, and shrug). An optical navigation system registered rotational motions in the sternoclavicular, scapulothoracic, and acromioclavicular joints in the intact and Rockwood V conditions. In the acromioclavicular joint, mediolateral, anteroposterior, and superoinferior translations were also analyzed.

RESULTS

In the Rockwood V condition, a significant increase in clavicular elevation in the sternoclavicular joint during both humerothoracic and scapulothoracic movements was demonstrated, whereas a significant decrease in posterior rotation of the clavicle occurred only during humerothoracic movements. In the scapulothoracic joint, the scapular position changed most significantly during protraction. In the acromioclavicular joint, the scapular tilting position was altered significantly during both humerothoracic and scapulothoracic movements, whereas the scapular rotational position changed only during coronal and sagittal plane elevation. The largest significant changes in the scapular protraction position were seen during protraction movement. Further, in the acromioclavicular joint there was a significant inferior translation of the scapula during all motions, a significant anterior translation during protraction and horizontal adduction, and a significant posterior translation during coronal plane elevation. Mediolaterally, the acromial end of the scapula slid further under the distal clavicle during protraction than during horizontal adduction.

CONCLUSION

Large kinematic differences were seen between the intact state and a Rockwood V lesion not only during humerothoracic movements but also during scapulothoracic movements in the cadaveric model. During humerothoracic movements, rotational differences were mainly caused by alterations in the clavicular position. In contrast, during protraction, the alterations in the scapular position were the dominant factor.

CLINICAL RELEVANCE

This study demonstrates that protraction induces larger kinematic alterations than horizontal adduction in acromioclavicular injuries and can therefore be included in both clinical examination and kinematic analyses to identify lesions more clearly.

A Technique for a More Accurate Acromioclavicular Joint Reduction in Arthroscopic Coracoclavicular Stabilization of Acromioclavicular Joint Dislocation

Loss of reduction is the most common complication following acromioclavicular dislocations treatment, with literature showing greater postoperative coracoclavicular distances associated with worse clinical results. We present a surgical gesture that aims to help surgeons achieve and secure an anatomic acromioclavicular reduction during coracoclavicular fixation. This technique has the possibility to improve radiological and functional results of acromioclavicular dislocation treatment.

Acromioclavicular Joint Injuries: Effective Rehabilitation

Purpose

To perform a review of the literature focusing on rehabilitation protocols in patients with acromioclavicular (AC) joint injuries treated operatively and nonoperatively and to provide an updated rehabilitation treatment algorithm.

Methods

Studies were identified by searching the MEDLINE database from 01/1995 to 09/2020. Included studies contained detailed rehabilitation protocols with physiologic rationale for AC joint injuries. Biomechanical studies, technique articles, radiographic studies, systematic reviews, case studies, editorials, and studies that compared nonoperative versus operative treatment without focus on rehabilitation were excluded. Following identification of the literature, an updated treatment algorithm was created.

Results

The search strategy yielded 1742 studies, of which 1654 studies were excluded based on title, 60 on the abstract, and 25 on the full manuscript. One study was manually identified using article reference lists, yielding four publications presenting detailed rehabilitation protocols based on physiologic rationale. No randomized controlled trials or comparative studies were identified or cited as a basis for these rehabilitation protocols.

Conclusion

Few detailed rehabilitation protocols in patients with AC joint injuries have been published. These protocols are limited by their standardization, arbitrary timelines, and provide minimal assessment of individual patient characteristics. The quality of patient care can be improved with more practical guidelines that are goal-oriented and allow for critical thinking among clinicians to address individual patient needs. Three common barriers preventing successful rehabilitation were identified and addressed: Pain, Apprehension, and (anterior chest wall) Stiffness to regain Scapular control, effectively termed "PASS" for AC joint rehabilitation.

Clinical Relevance

Rehabilitation protocols for AC joint injuries should be less formulaic and instead allow for critical thinking and effective communication among clinicians and therapists to address individual patient needs.

Methods used to assess the severity of acromioclavicular joint separations in Japan: a survey

Background

In acromioclavicular joint (ACJ) separations, patient characteristics determine the indications for surgery. However, in Japan, classification methods used to assess the severity of ACJ separations differ between institutions, and even within a classification method, different interpretations can lead to different assessments of severity. Therefore, in this study, we conducted an email survey of Japan Shoulder Society (JSS) members regarding their assessment methods for ACJ separation severity.

Methods

A questionnaire about methods for assessing the severity of ACJ separations was emailed to JSS members (1655) including 59 JSS councilors. The survey focused on diagnostic imaging methods, classifications of severity assessments, and methods of assessing severity.

Results

In total, 183 responses were received. All respondents used an anteroposterior view of the ACJ. Severity assessments were classified by the Tossy classification (57 respondents), Rockwood classification (141 respondents), and other classifications (7 respondents) including duplication. Of the 141 respondents using the Rockwood classification, 119 diagnosed type III as ACJ dislocation when the inferior clavicle border translated above the superior acromial border, whereas 56 used the coracoclavicular distance. However, to diagnose type V, 118 respondents used the coracoclavicular distance whereas 38 used palpation. To diagnose type IV, 57 respondents considered all cases in which the clavicle translated posterior to the acromion, even when vertical ACJ dislocation occurred simultaneously. However, 88 respondents did so in the presence of posterior clavicle displacement and ACJ subluxation.

Conclusion

The Rockwood classification is commonly used for severity assessments in Japan; however, there is some disagreement regarding the assessment for the diagnosis of type IV. Methods to diagnose both superior and posterior translation of the clavicle need further debate.

Acromioclavicular joint reconstruction: an additional acromioclavicular cerclage does not improve horizontal stability in double coraco-clavicular tunnel technique

PURPOSE

Horizontal instability-especially in the posterior plane-is a common problem after acromioclavicular joint injuries. The purpose was to compare the stability of a single coraco-clavicular tunnel technique and a double coraco-clavicular tunnel technique for coraco-clavicular ligament reconstruction and to examine the influence of an additional acromioclavicular cerclage on the horizontal stability in the acromioclavicular joint.

METHODS

21 acromioclavicular joints of human cadaveric shoulders were randomly assigned to the following groups: single coraco-clavicular tunnel technique with horizontal augmented acromioclavicular cerclage (SCT + AC); double coraco-clavicular tunnel technique (DCT); double coraco-clavicular tunnel technique and acromioclavicular cerclage (DCT + AC). The specimens underwent cyclic horizontal testing and were recorded using a 3D optical measuring system.

RESULTS

The displacement and the increase in displacement in relation to the displacement after precondition for SCT + AC were significantly higher after every measured amount of cycles than for DCT (p₁₀ = 0.0023; p₅₀₀₀ = 0.0012) and DCT + AC (p₁₀ = 0.0006; p₅₀₀₀ = 0.0012). There was no significant difference in the total displacement, or in the increase in total displacement between double coraco-clavicular tunnel reconstructed groups with and without additional acromioclavicular cerclage.

CONCLUSION

Double coraco-clavicular tunnel technique with and without additional acromioclavicular cerclage results in a significant higher stability regarding the horizontal plane in comparison to single coraco-clavicular tunnel technique with acromioclavicular cerclage. Based on the results of this biomechanical in vitro study, the use of an additional acromioclavicular cerclage with single coraco-clavicular tunnel technique may not be indicated in most cases. The effect of an additional acromioclavicular cerclage seems to be negligible, at least in presence of a double-coraco-clavicular tunnel technique reconstruction. Techniques of AC joint reconstruction should focus on the use of double coraco-clavicular tunnel devices.

Percutaneous endobutton fixation of acute acromioclavicular joint injuries and lateral clavicle fractures

INTRODUCTION

This paper describes a novel technique developed by the senior author to address acute acromioclavicular joint (ACJ) dislocations and certain distal clavicle fractures.

METHODS

The procedure employs a four strand, single tunnel, double endobutton repair performed entirely percutaneously, without any arthroscopic guidance or deep surgical dissection.

RESULTS

We present the preliminary results from our series of 6 consecutive patients performed over a period of 18 months. The mean length of surgery was 36min (range 32-40) and the mean correction of coracoclavicular (CC) distance achieved was 12.6 mm (range 10.3-14.1). There was no restriction of movement in any of the patients post-operatively and their average QuickDASH scores at final follow-up was 4.2 (range 0-6.8).

CONCLUSION

Results in the present series were at least comparable to those for other techniques, validating percutaneous treatment as a solution for acute ACJ dislocations.

[Current aspects and new techniques in dislocation of the shoulder joint]

With 12% of all injuries concerning the shoulder, acromioclavicular (AC) joint dislocations are a common injury especially in young and active patients. The Rockwood classification is widely accepted, which differentiates between six types depending on the degree of injury and the vertical dislocation. Because the classification does not adequately address the horizontal instability, its benefits are questionable and there is currently no consensus. For this reason, the classification and the therapy of these injuries are increasingly becoming the subject of scientific investigations. Whereas conservative treatment for type I and II injuries and operative treatment for type IV-VI injuries are widely accepted, there is still no agreement in treating type III lesions. The goal of this review article is to present the current evidence for the diagnostics, different classifications and therapeutic possibilities.