Posterior Rotational and Translational Stability in Acromioclavicular Ligament Complex Reconstruction: A Comparative Biomechanical Analysis in Cadaveric Specimens

ANATOMICAL AND BIOMECHANICAL ROLE OF STATIC STABILIZERS OF THE ACROMIOCLAVICULAR JOINT

OBJECTIVE

The aim: To determine the anatomical and biomechanical significance of the static stabilizers of the acromioclavicular joint by conducting numerical modeling using the finite element method and experimental investigation.

PATIENTS AND METHODS

Materials and methods: To ensure the study, modeling of the deformation processes of the clavicle and scapula systems with various combinations of ligament damage was conducted. The COMPAS-3D software package was used to build the simulation model, which allowed obtaining models that are closest to reality. To verify the results of the numerical modeling, corresponding studies of the mechanical characteristics and determination of the stiffness of the investigated systems were carried out using the upgraded TIRAtest-2151 testing stand.

RESULTS

Results: The stiffest system is the system in which all ligaments are intact, and the sequence of decreasing stiffness of the system is presented in the following order: damage to lig. trapezoideum; lig. conoideum; lig. claviculo-acoacromiale inferior; lig. claviculo-acoacromiale superior; the coracoclavicular ligament complex; the acromioclavicular ligament complex.

CONCLUSION

Conclusions: Static stabilizers in general, and their components in particular, are characterized by significant anatomical and functional features. The natural stabilization of the acromioclavicular joint is provided by their synergistic interaction, which is the basis for the development and implementation of surgical interventions, the scope of which includes the restoration of both ligament complexes. The loss of stiffness in the «clavicle-scapula» system is significantly more pronounced when lig. acromioclaviculare superior and inferior are damaged (8.5 N/mm) than when lig. conoideum and lig. trapezoideum are damaged (11.6 N/mm).

The stress and strain pattern in the ligaments of the acromioclavicular joint using a quasi-static model

BACKGROUND

The precise role of the acromioclavicular and coracoclavicular ligaments during shoulder motion is unclear. We evaluate changes in the stress-strain distribution of the acromioclavicular joint's ligaments during different shoulder passive motion positions.

METHODS

A 3D acromioclavicular joint model was reconstructed. A constitutive hyperelastic model was used for the ligaments. The kinematics of the shoulder girdle was taken to simulate shoulder abduction (Motion 1) and horizontal adduction (Motion 2). A computer-generated quasi-static and non-linear finite element model was used to predict the 3D stress-strain distribution pattern of the acromioclavicular ligament and the coracoclavicular ligament complex.

FINDINGS

In motion 1, from 20 to 90° the peak von Mises stress was found in the conoid (4.14 MPa) and the anteroinferior bundle (2.46 MPa), while from 90 to 120° it was found in the conoid and the trapezoid. However, there were no significant differences between the mean stress values between anteroinferior bundle and trapezoid throughout the motion (p = 0.98). In Motion 2, from 20 to 80° the maximum equivalent elastic strain was found in the anteroinferior bundle (0.68 mm/mm) and the conoid (0.57 mm/mm), while from 80 to 100° it was higher in the conoid (0.88 mm/mm) than in the anteroinferior bundle (0.77 mm/mm).

INTERPRETATION

The coracoclavicular ligament complex demonstrated a high stress-strain concentration during simulated passive shoulder abduction. Additionally, it was shown that the acromioclavicular ligament plays an important role in joint restraint during passive horizontal adduction, changing the primary role with the trapezoid and conoid at different motion intervals.

Acromioclavicular reconstruction techniques after acromioclavicular joint injuries: A systematic review of biomechanical studies

BACKGROUND

Residual horizontal instability after surgical treatment for acromioclavicular joint injuries is seen as a potential cause of suboptimal clinical outcomes. Biomechanical studies have demonstrated that the acromioclavicular capsule/ligaments are the primary restraints for anteroposterior translation. However, limited studies have addressed the biomechanics of a reconstruction of the acromioclavicular capsule/ligaments. The aim of this systematic review was to evaluate the biomechanical role of acromioclavicular capsule/ligament reconstruction techniques after an acromioclavicular joint injury.

METHODS

A search was carried out on the databases Medline and EMBASE, and was conducted according to the PRISMA guidelines. Biomechanical studies addressing horizontal and vertical displacement or joint stiffness after reconstructing the acromioclavicular capsule/ligament with or without coracoclavicular ligament reconstruction, were included.

FINDINGS

Nineteen studies were included in this review after screening and eligibility assessment. Five of them investigated different sole acromioclavicular capsule/ligament reconstruction techniques. In 10 studies, a sole coracoclavicular ligament reconstruction was compared to a coracoclavicular ligament reconstruction with additional acromioclavicular capsule/ligament reconstruction. The remaining 4 studies compared different acromioclavicular capsule/ligament with coracoclavicular reconstruction techniques with each other.

INTERPRETATION

Several testing protocols to evaluate acromioclavicular capsule/ligament reconstruction have been described and can make it difficult to compare the results of the different studies. Acromioclavicular capsule/ligament reconstruction may provide increased anteroposterior and rotational stability but an optimal reconstruction technique, which mimics all biomechanical characteristics of the native joint is not yet available.

Reconstruction of the Acromioclavicular Joint Using a Double Augmentation With Hamstrings Tendon and Dermal Graft

The purpose of this article is to describe a technique to restore both vertical and horizontal stability using an augmentation of the acromioclavicular ligament complex (ACLC) and coracoclavicular (CC) ligaments with the combination of synthetic and biological support. Our technique introduces a modification in the surgical procedure for acromioclavicular (AC) joint dislocations; it provides the use of biological supplements not only during the repair of the CC ligaments but also when the ACLC is restored due to the use of a dermal patch as an augmentation allograft after the use of a horizontal cerclage. The main purpose of this technique is to replicate the anatomy and functionality of the native ligaments that stabilize the AC joint to improve both clinical and functional results.

The Role of the Trapezius in Stabilization of the Acromioclavicular Joint: A Biomechanical Evaluation

Background

Acromioclavicular joint (ACJ) injuries are common, and many are adequately treated nonoperatively. Biomechanical studies have mainly focused on static ligamentous stabilizers. Few studies have quantified ACJ stabilization provided by the trapezius.

Purpose/Hypothesis

To elucidate the stabilization provided by the trapezius to the ACJ during scapular internal and external rotation (protraction and retraction). It was hypothesized that sequential trapezial resection would result in increasing ACJ instability.

Study Design

Controlled laboratory study.

Methods

A biomechanical approach was pursued, with 10 cadaveric shoulders with the trapezius anatomically force loaded to normal. The trapezius was then serially transected over 8 trials, which alternated between clavicular defects (CD) and scapular defects (SD); each sequential defect consisted of 25% of the clavicular or scapular trapezial attachment. After each defect, specimens were tested with angle-controlled scapular internal and external rotation (12°) with rotary torque measurements to evaluate ACJ stability.

Results

The mean resistance in rotary torque for 12° of scapular internal rotation (protraction) with native specimens was 7.0 ± 2.0 N·m. Overall, internal rotation demonstrated a significant decrease in ACJ stability with trapezial injury (P < .001). Eight sequential defects resulted in the following significant percentage decreases in rotary torque from native internal rotation: 1.5% (25% CD; 0% SD), 5.6% (25% CD; 25% SD), 5.1% (50% CD; 25% SD), 6.5% (50% CD; 50% SD), 3.8% (75% CD; 50% SD), 7.1% (75% CD; 75% SD), 6.7% (100% CD; 75% SD), and 12.3% (100% CD 100% SD) (P < .001). The mean resistance in rotary torque for 12° of scapular external rotation (retraction) with native specimens was 7.1 ± 1.7 N·m. External rotation did not demonstrate a significant decrease in ACJ stability with trapezial injury (P = .596). The 8 sequential defects resulted in decreases in rotary torque from native external rotation of 0%, 3.8%, 4.0%, 3.2%, 3.5%, 3.4%, 4.2%, and 0.7%.

Conclusion

Trapezial injury resulted in increased instability in the setting of scapular internal rotation (protraction) of the ACJ.

Clinical Relevance

These findings validate the inclusion of deltotrapezial fascial injury consideration in the modified Rockwood classification system. Repair of the trapezial insertion on the ACJ may provide improved outcomes in the setting of ACJ reconstruction.

Qualitative and Quantitative Anatomic Descriptions of the Coracoclavicular and Acromioclavicular Ligaments: A Systematic Review

Purpose

Methods

Results

Conclusions

Clinical Relevance

The Morphology of the Acromioclavicular Joint Does Not Influence the Postoperative Outcome Following Acute Stabilization—A Case Series of 81 Patients

Purpose

To specifically evaluate the influence of the acromioclavicular (AC)-joint morphology on the outcome after arthroscopically assisted coracoclavicular (CC) stabilization surgery with suspensory fixation systems and to investigate whether an additional open AC-joint reduction and AC cerclage improves the clinical outcome for patients with certain morphologic AC-joint subtypes.

Methods

Patients with an acute acromioclavicular joint injury, who underwent arthroscopically assisted CC stabilization with suspensory fixation systems with or without concomitant AC cerclage between January 2009 and June 2017 were identified and included in this retrospective cohort analysis. AC-joint morphology was assessed on preoperative radiographs and categorized as “flat” or “non-flat” (“oblique”/“curved”) subtypes. After a minimum of 2 years of follow-up, postoperative Single Assessment Numeric Evaluation (SANE), American Shoulder and Elbow Surgeons (ASES), and visual analog scale (VAS) scores for pain were collected. A subgroup analysis of clinical outcomes depending on the surgical technique and morphological subtype of the AC joint was performed.

Results

Eighty-one patients (95% male, mean age 35 ± 12 years) could be included at a mean follow-up of 57 ± 14 months. Radiographic assessment of AC-joint morphology showed 24 (30%) cases of flat type, 38 (47%) cases of curved type, and 19 (23%) cases of oblique morphology. Postoperatively, no clinically significant difference could be detected after the treatment of AC joint injury via CC stabilization with or without concomitant AC cerclage (VAS_rest: P = .067; VAS_max: P = .144, ASES: P = .548; SANE: P = .045). No clinically significant differences were found between the surgical techniques for the flat morphologic subtype (VAS_rest: P = .820; VAS_max: P = .251; SANE: P = .104; ASES: P = .343) or the non-flat subtype (VAS_res: P = .021; VAS_max: P = .488; SANE: P = .243, ASES: P = .843).

Conclusions

In arthroscopically assisted AC stabilization surgery with suspensory fixation systems for acute AC-joint injury, the AC-joint morphology did not influence the postoperative outcome, independent of the surgical technique. No clinical benefit of performing an additional horizontal stabilization could be detected in our collective at mid-term follow-up.

Level of Evidence

Level IV, therapeutic case series.

Addressing Arthroscopic-Assisted Acromioclavicular Joint Reconstruction in the Beach Chair Position With Concomitant Labral Pathology in the Lateral Decubitus Position

High-grade Acromioclavicular (AC) injuries are complete dislocations, involving ruptures of the AC and coracoclavicular ligaments. They occur following trauma after a fall, direct-blow to an adducted arm, or indirectly by falling onto an abducted, outstretched extremity. Given this traumatic etiology, additional intra-articular pathologies can arise and may go unnoticed because of the painful and prominent AC joint (ACJ). Previous studies have evaluated patients with high-grade ACJ injuries with diagnostic arthroscopy at the time of an ACJ reconstruction. They found associated injuries to the labrum/biceps, rotator cuff, and articular cartilage. The arthroscopic-assisted ACJ reconstruction (AA-ACJR) technique has made it possible to identify the associated injuries and treat them concurrently. The previous studies have performed this reconstruction in the beach chair position (BCP) and have addressed the concomitant pathology in the same position. As opposed to the BCP, the lateral decubitus position (LDP) allows for easier application of traction to the arm and, thus, improves visualization of the glenoid, especially the inferior and posteroinferior portions. It is imperative to gain appropriate access to the inferior glenoid for anchor placement to address this component of traumatic instability. We present the technique for addressing high-grade ACJ injuries with AA-ACJR in the BCP preceded by labral repair in the LDP.

Anteroinferior bundle of the acromioclavicular ligament plays a substantial role in the joint function during shoulder elevation and horizontal adduction: a finite element model

Background

Postoperative acromioclavicular (AC) ligament deficiency has been identified as a common cause of failure after isolated coracoclavicular reconstruction. The two-bundle arrangement of the acromioclavicular ligament has recently been reported in histological and anatomical research. In addition, a clear structural advantage of the superoposterior bundle (SPB) over the less consistent anteroinferior bundle (AIB) was also found. However, the current understanding of the function of the acromioclavicular ligament in joint stability is based on uniaxial bone loading experiments and sequential ligament sectioning. Consequently, these rigid biomechanics models do not reproduce the coupled physiological kinematics, neither in the normal joint nor in the postoperative condition. Therefore, our goal was to build a quasi-static finite element model to study the function of the acromioclavicular ligament based on its biomechanical performance patterns using the benefits of computational models.

Methods

A three-dimensional bone model is reconstructed using images from a healthy shoulder. The ligament structures were modeled according to the architecture and dimensions of the bone. The kinematics conditions for the shoulder girdle were determined after the osseous axes aligned to simulate the shoulder elevation in the coronal plane and horizontal adduction. Three patterns evaluated ligament function. The peak von Mises stress values were recorded using a clock model that identified the stress distribution. In addition, the variation in length and displacement of the ligament during shoulder motion were compared using a two-tailed hypotheses test. P values < 0.01 were considered statistically significant.

Results

The peak von Mises stress was consistently observed in the AIB at 2:30 in coronal elevation (4.06 MPa) and horizontal adduction (2.32 MPa). Except in the position 2:00, statistically significant higher deformations were identified in the two bundles during shoulder elevation. The highest ligament displacement was observed on the Y- and Z-axes.

Conclusions

The AIB has the primary role in restricting the acromioclavicular joint during shoulder motion, even though the two bundles of the AC ligament have a complementary mode of action. During horizontal adduction, the SPB appears to prevent anterior and superior translation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-02966-0.

Injuries to the anterolateral ligament are observed more frequently compared to lesions to the deep iliotibial tract (Kaplan fibers) in anterior cruciate ligamant deficient knees using magnetic resonance imaging

PURPOSE

To determine the accuracy of detection, injury rate and inter- and intrarater reproducibility in visualizing lesions to the anterolateral ligament (ALL) and the deep portion of the iliotibial tract (dITT) in anterior cruciate ligament (ACL) deficient knees.

METHODS

Ninety-one consecutive patients, out of those 25 children (age 14.3 ± 3.5 years), with diagnosed ACL tears were included. Two musculoskeletal radiologists retrospectively reviewed MRI data focusing on accuracy of detection and potential injuries to the ALL or dITT. Lesion were diagnosed in case of discontinued fibers in combination with intra- or peri-ligamentous edema and graded as intact, partial or complete tears. Cohen's Kappa and 95% confidence intervals (95% CI) were determined for inter- and intrarater reliability measures.

RESULTS

The ALL and dITT were visible in 52 (78.8%) and 56 (84.8%) of adult-and 25 (100%) and 19 (76.0%) of pediatric patients, respectively. The ALL was injured in 45 (58.5%; partial: 36.4%, compleate: 22.1%) patients. Partial and comleate tears, where visualized in 21 (40.4%) and 16 (30.8%) adult- and seven (28.0%) and one (4%) peditric patients. A total of 16 (21.3%; partial: 13.3%, compleate: 8.0%) dITT injuries were identified. Partal and complete lesions were seen in seven (12.5%) and five (8.9%) adult- and three (15.8%) and one (5.3%) pediatric patients. Combined injuries were visualized in nine (12.7%) patients. Inter-observer (0.91-0.95) and intra-observer (0.93-0.95) reproducibility was high.

CONCLUSION

In ACL injured knees, tears of the ALL are observed more frequently compared to lesions to the deep iliotibial tract. Combined injuries of both structures are rare. Clinically, the preoperative visualization of potentially injured structures of the anterolateral knee is crucial and is important for a more personalized preoperative planning and tailored anatomical reconstruction. The clinical implication of injuries to the anterolateral complex of the knee needs further investigation.

LEVEL OF EVIDENCE

II.

Editorial Commentary: Arthroscopic-Assisted Coracoclavicular Ligament Reconstruction Leads to Improved Patient-Reported Outcomes, But Patient Satisfaction Is a Harder Threshold to PASS

There are numerous described techniques for surgical management of high-grade acromioclavicular (AC) joint injuries, and the associated clinical outcomes can be quite variable. Contemporary techniques are typically directed at anatomic reconstruction of the coracoclavicular (CC) ligaments through either an arthroscopy-assisted or an open approach. Most patients treated with acute surgery improve, whereas in chronic cases, the majority improve, but a significant number have persistent recurrent deformity due to loss of anatomic reduction. In addition, whether acute or chronic, over one quarter of patients do not have a PASS (patient acceptable symptomatic state). Of interest, PASS may not primarily be related to the final deformity in terms of coracoclavicular distance, and investigation is still required in terms of the effect of anteroposterior or rotational instability of the AC joint after injury and surgery. Finally, PASS values for AC separation are not well established, resulting in a current limitation of the strength of applying threshold values to this pathology.

Quantitative and Qualitative Surgical Anatomy of the Acromioclavicular Joint Capsule and Ligament: A Cadaveric Study

BACKGROUND

The acromioclavicular (AC) capsule and ligament have been found to play a major role in maintaining horizontal stability. To reconstruct the AC capsule and ligament, precise knowledge of their anatomy is essential.

PURPOSE/HYPOTHESIS

The purposes of this study were (1) to determine the angle of the posterosuperior ligament in regard to the axis of the clavicle, (2) to determine the width of the attachment (footprint) of the AC capsule and ligament on the acromion and clavicle, (3) to determine the distance to the AC capsule from the cartilage border of the acromion and clavicle, and (4) to develop a clockface model of the insertion of the posterosuperior ligament on the acromion and clavicle. It was hypothesized that consistent angles, attachment areas, distances, and insertion sites would be identified.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A total of 12 fresh-frozen shoulders were used (mean age, 55 years [range, 41-64 years]). All soft tissue was removed, leaving only the AC capsule and ligament intact. After a qualitative inspection, a quantitative assessment was performed. The AC joint was fixed in an anatomic position, and the attachment angle of the posterosuperior ligament was measured using a digital protractor. The capsule and ligament were removed, and a coordinate measuring device was utilized to assess the width of the AC capsule footprint and the distance from the footprint to the cartilage border of the acromion and clavicle. The AC joint was then disarticulated, and the previously marked posterosuperior ligament insertion was transferred into a clockface model. The mean values across the 12 specimens were demonstrated with 95% CIs.

RESULTS

The mean attachment angle of the posterosuperior ligament was 51.4° (95% CI, 45.2°-57.6°) in relation to the long axis of the entire clavicle and 41.5° (95% CI, 33.8°-49.1°) in relation to the long axis of the distal third of the clavicle. The mean clavicular footprint width of the AC capsule was 6.4 mm (95% CI, 5.8-6.9 mm) at the superior clavicle and 4.4 mm (95% CI, 3.9-4.8 mm) at the inferior clavicle. The mean acromial footprint width of the AC capsule was 4.6 mm (95% CI, 4.2-4.9 mm) at the superior side and 4.0 mm (95% CI, 3.6-4.4 mm) at the inferior side. The mean distance from the lateral clavicular attachment of the AC capsule to the clavicular cartilage border was 4.3 mm (95% CI, 4.0-4.6 mm), and the mean distance from the medial acromial attachment of the AC capsule to the acromial cartilage border was 3.1 mm (95% CI, 2.9-3.4 mm). On the clockface model of the right shoulder, the clavicular attachment of the posterosuperior ligament ranged from the 9:05 (range, 8:00-9:30) to 11:20 (range, 10:00-12:30) position, and the acromial attachment ranged from the 12:20 (range, 11:00-1:30) to 2:10 (range, 13:30-14:40) position.

CONCLUSION

The finding that the posterosuperior ligament did not course perpendicular to the AC joint but rather was oriented obliquely to the long axis of the clavicle, in combination with the newly developed clockface model, may help surgeons to optimally reconstruct this ligament.

CLINICAL RELEVANCE

Our results of a narrow inferior footprint and a short distance from the inferior AC capsule to cartilage suggest that proposed reconstruction of the AC joint capsule should focus primarily on its superior portion.