Anatomy of the clavicle and coracoid process for reconstruction of the coracoclavicular ligaments

An anatomic study of the coracoid process as it relates to bone transfer procedures

INTRODUCTION

The Latarjet and Bristow procedures address recurrent anterior shoulder instability in the context of a significant bony defect. However, the bony and soft tissue anatomy of the coracoid as they relate to coracoid transfer procedures has not yet been defined. The purpose of this study was to describe the soft tissue attachments of the coracoid as they relate to the bony anatomy and to define the average amount of bone available for use in coracoid transfer.

METHODS

Ten paired fresh frozen shoulders from deceased donors were dissected, exposing the coracoid, lateral clavicle, and acromion, along with the coracoid soft tissue attachments. The bony dimensions of the coracoid and the locations and sizes of the soft tissue footprints of the coracoid were measured.

RESULTS

The mean maximum length of the coracoid available for transfer (ie, distance from the coracoid tip to the anterior border of the coracoclavicular ligament) was 28.5 mm. The mean distance from the coracoid tip to the anterior pectoralis minor was 4.6 mm, to the posterior pectoralis minor was 17.7 mm, to the anterior coracoacromial ligament was 7.8 mm, and to the posterior coracoacromial ligament was 25.7 mm.

CONCLUSION

Average dimensions of the bony coracoid and average locations and sizes of coracoid soft tissue footprints are provided. This anatomic description of the coracoid bony anatomy and its soft tissue insertions allows surgeons to correlate the location of their coracoid osteotomy with the soft tissue implications of the coracoid transfer as the native anatomy is manipulated in these nonanatomic procedures.

Biomechanical comparison of coracoclavicular reconstructive techniques

BACKGROUND

Acromioclavicular joint dislocations are common orthopaedic injuries. Numerous operative techniques have been described, but the gold standard has yet to be defined. The goal of fixation is to create a stiff and strong reconstruction of the coracoclavicular ligaments to provide optimal stability. The modified Weaver-Dunn is the traditional surgical procedure. However, due to the high rate of recurrent instability with this technique, a shift toward a more anatomic repair has occurred.

PURPOSE

To evaluate the biomechanical performance of multiple types of coracoclavicular ligament reconstruction.

STUDY DESIGN

Controlled laboratory study.

METHODS

Thirty fresh-frozen human cadaveric shoulders were assigned to 1 of 5 reconstruction groups or a control group: modified Weaver-Dunn, nonanatomic allograft, anatomic allograft, anatomic suture, and GraftRope. A type III acromioclavicular joint dislocation was simulated in all specimens. The 5 techniques were completed, and a cyclic preload and a load-to-failure protocol were performed.

RESULTS

The control had an average load to failure of 1330.6 ± 447.0 N. Compared with all techniques, the anatomic allograft had the highest load to failure, 948 ± 148 N. It had a significantly higher load to failure than the modified Weaver-Dunn (523.2 ± 98.6 N, P = .001), the anatomic suture (578.2 ± 195.3 N, P = .01), the nonanatomic allograft (591.2 ± 65.6 N, P = .003), and the GraftRope (646 ± 167.4, P = .016). No significant difference in load to failure was found between the remaining techniques.

CONCLUSION

The anatomic allograft reconstruction has superior initial biomechanical properties compared with the modified Weaver-Dunn, nonanatomic allograft, anatomic suture, and GraftRope techniques.

CLINICAL RELEVANCE

Anatomic reconstruction of the coracoclavicular ligaments with allograft may provide a stronger biological solution for acromioclavicular joint dislocations. This reconstruction may minimize recurrent subluxation and pain and permit earlier rehabilitation when compared with current techniques.

Acromioclavicular joint injuries: anatomy, diagnosis, and treatment

Acromioclavicular (AC) joint injuries are common in athletic populations and account for 40% to 50% of shoulder injuries in many contact sports, including lacrosse, hockey, rugby and football. The AC joint is stabilized by static and dynamic restraints, including the coracoclavicular (CC) ligaments. Knowledge of these supporting structures is important when identifying injury and directing treatment. Management of AC injuries should be guided by severity of injury, duration of injury and symptoms, and individual patient factors. These help determine how best to guide management, and whether patients should be treated surgically or nonsurgically. Treatment options for AC injuries continue to expand, and include arthroscopic-assisted anatomic reconstruction of the CC ligaments. The purpose of this article is to review the anatomy, diagnostic methods, and treatment options for AC joint injuries. In addition, the authors' preferred reconstruction technique and outcomes are presented.

Tratamento artroscópico da luxação acromioclavicular aguda com âncoras

OBJETIVO: Apresentar os resultados clínicos e radiográficos de uma série de casos com diagnóstico de Luxação Acromioclavicular (LAC) Aguda, tratados através da fixação coracoclavicular com âncoras por via artroscópica. MÉTODO: Vinte pacientes apresentando LAC com menos de 30 dias de evolução foram operados pela técnica da estabilização coracoclavicular com âncoras por via artroscópica. Duas âncoras metálicas com dois fios cada, foram inseridas no coracóide. Os fios foram amarrados sobre a clavícula passando por túneis transósseos claviculares. Para a avaliação radiográfica, foi utilizada a medida comparativa da distância coracoclavicular com o lado contralateral e a avaliação funcional através dos escores de Constant e UCLA o seguimento foi de seis meses. RESULTADO: Dos vinte casos inicialmente selecionados, seis necessitaram de novo procedimento cirúrgico e foram excluídos do estudo. Dos quatorze pacientes restantes, apenas dois mantiveram redução da articulação acromioclavicular, enquanto os demais apresentaram algum grau de desvio no decorrer da evolução. Desconsiderando os pacientes excluídos, os escores de Constant e UCLA tiveram média 94,79 (82-100) e, 32,64 (26-35), respectivamente. CONCLUSÃO: A técnica apresentou um alto índice de perda da redução ao longo da evolução de seis meses. A avaliação funcional apresentou resultado satisfatório com escore médio elevado de Evidência: Nível de Evidência: Nível III, estudo retrospectivo.

Management of the failed AC joint reconstruction: causation and treatment

With recent studies showing improved biomechanical behavior of anatomic acromioclavicular joint reconstructions, these techniques are more frequently being performed. With both the more historic methods of fixation such as coracoacromial ligament transfer along with the newer anatomic reconstruction, potential for failure exists. However, there is a paucity of literature addressing these failures and possible treatment options. The purpose of this review is to report cases of failed reconstructions, describe failure mechanisms, and propose treatment options.

The effect of distal clavicle excision on in situ graft forces in coracoclavicular ligament reconstruction

BACKGROUND

Recently, some have suggested that the acromioclavicular articulation confers stability to the construct after coracoclavicular ligament reconstruction for acromioclavicular joint separation. Therefore, it has been suggested that distal clavicle excision should not be performed in this context to protect the graft during healing.

HYPOTHESIS

Sectioning the acromioclavicular ligaments would significantly increase in situ forces of a coracoclavicular ligament graft, whereas performing a distal clavicle resection would not further increase in situ graft forces.

DESIGN

Controlled laboratory study.

METHODS

A simulated coracoclavicular reconstruction was performed on 5 cadaveric shoulders. Static loads of 80 N and 210 N were applied directly to the clavicle in 5 directions: anterior, anterosuperior, superior, posterosuperior, and posterior. The in situ graft force was measured using a force transducer under 3 testing conditions: (1) intact acromioclavicular ligaments, (2) sectioned acromioclavicular ligaments, and (3) distal clavicle excision.

RESULTS

For both magnitudes of load, in all directions, in situ graft force with intact acromioclavicular ligaments was significantly less than that with sectioned acromioclavicular ligaments (P < .001). Distal clavicle excision did not further increase the in situ graft forces with load applied to the clavicle in an anterior, anterosuperior, or superior direction. However, in situ graft forces were increased with distal clavicle excision when the clavicle was loaded with 210 N in the posterosuperior direction (60.4 ± 6.3 N vs 52.5 ± 7.1 N; P = .048) and tended to be increased with posterior loading of the clavicle (71.8 ± 6.2 N vs 53.1 ± 8.8 N; P = .125).

CONCLUSION

Intact acromioclavicular ligaments protect the coracoclavicular reconstruction by decreasing the in situ graft force. The slight increase in the in situ graft force only in the posterosuperior and posterior direction after distal clavicle excision suggests only a marginal protective role of the acromioclavicular articulation. Further, the peak graft forces observed represent only a small fraction of the ultimate failure strength of the graft.

CLINICAL RELEVANCE

Distal clavicle excision can perhaps be safely performed in the context of coracoclavicular ligament reconstruction without subjecting the graft to detrimental in situ force. Although the acromioclavicular articulation serves only a marginal role in protecting the coracoclavicular ligament graft, reconstruction of the acromioclavicular ligaments may serve an important role in decreasing in situ graft force during healing.

Triple endobuttton technique for the treatment of acute complete acromioclavicular joint dislocations: preliminary results

Numerous procedures have been described for the operative management of acromioclavicular (AC) joint injuries. Some of these techniques, including hardware fixation and non-anatomical reconstructions, are associated with serious complications and high failure rates. Recently, AC joint reconstruction techniques have focused on anatomical restoration of the coracoclavicular ligaments to achieve optimal clinical outcomes. We used a triple endobutton technique to separately reconstruct the trapezoid and the coronoid portions of the coracoclavicular ligament. We evaluated the preliminary clinical and radiological results of this technique in patients with acute complete dislocation of the AC joint. All patients achieved a significant improvement in the pain and function of shoulder at a mean follow-up interval of 12 months (range, 8-14 months). Excellent reduction of the AC joint was maintained. The triple endobutton technique may be safe and effective for the treatment of acute complete AC joint dislocations.

Arthroscopically assisted 2-bundle anatomical reduction of acute acromioclavicular joint separations

BACKGROUND

To achieve reduction of an acute acromioclavicular (AC) joint separation, novel procedures aim to provide stability and function by restoring the coracoclavicular anatomy.

HYPOTHESIS

Anatomical reconstruction for acute AC joint disruption using 2 flip-button devices results in satisfactory clinical function and provides a stable fixation.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

The outcome of 23 consecutive patients (21 men, 2 women; mean age, 37.5 +/- 10.2 years; range, 21-59 years) who underwent anatomical reduction for an acute AC joint dislocation using 2 flip-button devices, each separately replacing 1 coracoclavicular ligament, was evaluated clinically and radiographically preoperatively and 6, 12, and 24 months postoperatively. The evaluation included a visual analog scale for pain, the Constant score, the simple shoulder test, and the Short Form-36. An additional 7 patients had similar surgery during the same period, but 4 were lost to follow-up, 2 required surgical revision, and 1 developed postoperative infection.

RESULTS

There were 3 Rockwood type III, 3 type IV, and 17 type V separations. Mean follow-up was 30.6 +/- 5.4 months (range, 24-40 months). The visual analog scale and Constant score showed significant improvements from preoperative 4.5 +/- 1.9 (range, 1-7) and 34.3 +/- 6.9 (range, 22-44) to postoperative 0.25 +/- 0.5 (range, 0-1) and 94.3 +/- 3.2 (range, 88-98) at 24 months, respectively. Postoperative radiographic AC joint alignment was unsatisfactory in 8 cases, either in the coronal, axillary, or both planes, with no different clinical outcome when compared with the remaining patients.

CONCLUSION

Immediate anatomical reduction of an acute AC separation with flip-button devices provides satisfactory clinical results at intermediate-term follow-up. This technique should be performed by an experienced arthroscopist; tunnel and button placement are of utmost importance to avoid postoperative failure or loss of reduction.

Biomechanical comparison of a modified Weaver-Dunn and a free-tissue graft reconstruction of the acromioclavicular joint complex

BACKGROUND

Most surgical reconstructions of the separated acromioclavicular joint do not address the injured ligaments and capsule of the acromioclavicular joint.

PURPOSE

This study was undertaken to compare the biomechanical characteristics of a modified Weaver-Dunn reconstruction and an intramedullary acromioclavicular joint reconstruction that uses a free-tissue graft for reconstruction of both the coracoclavicular and acromioclavicular ligaments.

STUDY DESIGN

Controlled laboratory study.

METHODS

Each pair of 6 matched pairs of cadaveric shoulders was randomly selected for a modified Weaver-Dunn reconstruction on 1 side and the contralateral side was used for free-tissue graft reconstruction of the coracoclavicular and acromioclavicular ligamentous complexes. Anterior-posterior and superior-inferior acromioclavicular joint translation (in millimeters) was measured with acromioclavicular joint compressions of 10, 20, and 30 N, and with translational loads of 10 and 15 N both before and after acromioclavicular joint reconstruction. Load-to-failure testing was then performed for each construct. Repeated-measures analysis of variance (translational testing) and Wilcoxon signed rank test (load-to-failure testing), both with P = .05, were used for statistical analysis.

RESULTS

Mean anterior-posterior and superior-inferior translation of the intramedullary acromioclavicular joint reconstruction was significantly less than that of the modified Weaver-Dunn under all loading conditions (P < .001 and P = .001, respectively), but was not significantly different from that of the intact state (P = .656 and P = .173, respectively). Although the mean ultimate and yield loads and linear stiffness for the intramedullary acromioclavicular reconstruction were greater than that of the modified Weaver-Dunn reconstruction, this did not reach statistical significance (P = .625, P = .625, and P = .625, respectively).

CONCLUSION

Acromioclavicular joint reconstruction with free-tissue graft for both the coracoclavicular and acromioclavicular ligamentous complexes demonstrates initial stability significantly better than a modified Weaver-Dunn and similar to that of intact specimens.

CLINICAL RELEVANCE

This acromioclavicular joint reconstruction provides the surgeon with a relatively nondestructive option.

The cortical ring sign: a reliable radiographic landmark for percutaneous coracoclavicular fixation

BACKGROUND

For treatment of acute acromioclavicular separations, we have been using a reproducible radiographic view of the coracoid-the cortical ring sign-that we believe allows for placement of percutaneous coracoclavicular fixation safely and reliably in the center of the coracoid base, while avoiding the coracoid tip. This study evaluates the coracoid anatomy that the cortical ring sign represents, its utility for guiding fixation trajectory, and the proximity of neurovascular structures to this proposed trajectory.

MATERIALS AND METHODS

Kirschner wires were used to measure the orientation of the fluoroscopic beam in relation to the scapula and the proposed fixation trajectory using this radiographic view.

RESULTS

The cortical ring sign is achieved by first directing the x-ray beam perpendicular to the medial border of the scapula in the parasagittal plane and 49 degrees off the axis of the scapular spine in the axial plane, then fine-tuning until the coracoid cortical ring becomes evident. The nearest neurovascular structures to the fixation trajectory are the suprascapular artery and nerve (< 2 cm).

CONCLUSION

The cortical ring sign view targets the coracoid base and, as such, allows reliable, safe, percutaneous fixation in the center of the coracoid base.

LEVEL OF EVIDENCE

Basic Science.

Postnatal growth of the clavicle: birth to 18 years of age

BACKGROUND

The purpose of our study was to perform a large cross-sectional study aimed at determining the postnatal growth pattern of the clavicle from birth to 18 years of age.

METHODS

We analyzed the digital chest radiographs of a convenience sample of 961 individuals between birth and 18 years of age. Malrotated radiographs were excluded. Right and left clavicle lengths were measured in millimeters from the most lateral ossified border to the most medial ossified border of each clavicle. Study patients were divided into 19 subgroups with the first group being labeled as "birth to 11 months of age" followed by 1-year-olds, 2-year olds, etc. Patients were also grouped by sex. There was a minimum of 25 patients in each group.

RESULTS

At 18 years of age the mean+/-SD clavicle length for females was 149+/-12 mm and for males it was 161+/-11 mm. Although a statistically significant difference (P=0.049) was noted between the length of right and left clavicles it was not clinically significant (0.036 mm). A steady growth rate was noted for both genders from birth to the age of 12 years (8.4 mm/y). Above the age of 12 years there were significant differences in the growth of the clavicles of girls (2.6 mm/y) versus boys (5.4 mm/y) (P<0.001). Our data suggest that females achieve 80% of their clavicle length by 9 years of age and boys by 12 years of age.

CONCLUSION

This cross-sectional study establishes that relatively little clavicle growth (20%) remains for girls beyond age 9 years and for boys beyond 12 years. The length of one clavicle may be properly judged by comparing it with the contralateral clavicle.

CLINICAL RELEVANCE

Remodeling of the clavicle shaft fractures is currently believed to be proportional to remaining growth. Our study questions the capacity of the clavicle to re-establish normal length beyond the age thresholds we have identified.

Analysis of the capsule and ligament insertions about the acromioclavicular joint: a cadaveric study

PURPOSE

The purpose of this study was to analyze the capsular and ligamentous insertions about the acromioclavicular (AC) joint to determine the amount of bone that can be removed without destabilizing the joint.

METHODS

We dissected 28 cadaveric shoulders. The AC ligament insertions were measured under loupe magnification with a digital caliper on the acromial and clavicular sides on the anterior, posterior, superior, and inferior edges. We measured the distance to the coracoacromial (CA) and coracoclavicular ligaments. In addition, the axial and coronal angle of the AC joint was measured.

RESULTS

The AC joint capsular insertion on the acromion begins, on average, 2.8 mm (range, 2.3 to 3.3 mm) from the medial acromion and begins on the lateral clavicle a mean of 3.5 mm (range, 2.9 to 3.9 mm) from the distal clavicle. The mean capsular width ranged from 1.6 to 2.9 mm. The mean distance from the medial acromion to the CA ligament insertion was 3.5 mm. The mean axial angle of the AC joint was 51 degrees , with a 12 degrees coronal angle. The mean distance from the lateral clavicle to the start of the trapezoid ligament was 14.7 mm, and that to the conoid ligament was 32.1 mm.

CONCLUSIONS

An anatomic-based recommendation for safe AC joint resection is that 2 to 3 mm of the medial acromion and 3 to 4 mm of the distal clavicle can be resected without removing the AC capsular insertions. The trapezial and CA attachments are in close proximity to the AC capsular insertions. Medial resections greater that 15 mm will begin to take down the trapezoid ligament. Arthroscopic bone resection should be directed into the AC joint at approximately 50 degrees in the axial plane and 12 degrees in the coronal plane for safe symmetric resection.

CLINICAL RELEVANCE

These anatomic measurements suggest that AC joint resections (5 to 7 mm) with 2 to 3 mm from the acromial side and 3 to 4 mm from the clavicular side will not disrupt the stabilizing ligaments of the AC joint after distal clavicle resection.

Suspension suture augmentation for repair of coracoclavicular ligament disruptions

Surgical reconstruction of the coracoclavicular ligament is a fundamental part of management of high-grade acromioclavicular dislocations and Type II lateral third clavicular fractures. However, no single surgical procedure is fully satisfactory because of failure or complications. We present an alternative coracoclavicular stabilization technique, which avoids the use of hardware or tendon graft, that was used in 10 consecutive patients with complete coracoclavicular ligament disruptions. These patients were followed for a minimum of 14 months (average, 34.8 months; range, 14-55 months). At the final followup, functional outcome measurement instruments (University of California-Los Angeles shoulder rating system and Western Ontario Shoulder Instability Index) and radiographic analysis were adopted as the main outcome measures of shoulder function. The mean University of California-Los Angeles shoulder rating score and the mean Western Ontario Shoulder Instability Index aggregation score at 12 months after surgery were 33.8 (95% confidence interval, 32.8-34.8) and 93.4 (95% confidence interval, 88.2-98.6), respectively. The radiographic analysis revealed all patients had maintained reduction on radiographs at the final followup. These preliminary results suggest that this simple technique can achieve stable coracoclavicular reconstruction and facilitate healing of the repaired ligaments or fractures.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Coracoclavicular ligament reconstruction: biomechanical comparison of tendon graft repairs to a synthetic double bundle augmentation

For currently presented anatomical coracoclavicular ligament repairs issues such as autologous tendon graft versus synthetic suture augmentation and the optimum fixation strategies for both types of reconstruction are not solved. The purpose of the study was to compare the biomechanical properties of different tendon graft repairs to the characteristics of a synthetic polyester augmentation. Four anatomical coracoclavicular ligament repairs were biomechanically tested: 5 mm coracoclavicular tendon loop with suture fixation, tendon loop with flip button fixation, tendon loop with interference screw fixation versus a double 1.0-mm polyester repair with flip button fixation. The biomechanical testing included cyclic superio-inferior loading and a subsequent load to failure protocol. The ultimate failure loads were significantly higher for the double polyester/flip button repair (927 N) compared to all tendon repair techniques (maximum 640 N). In contrast the stiffness level was higher for the tendon repairs compared to the polyester/flip button repair (68.7 N/mm) but strongly dependent on the fixation technique (interference screw 97.2 N/mm, flip button 84.9 N/mm, side to side suture 60.9 N/mm). A synthetic coracoclavicular augmentation using a polyester suture provides adequate structural properties compared to a tendon repair. Therefore the decision for a tendon graft should be made by the necessity of a biologic substrate rather than by the assumption of a biomechanical advantage.

Acromioclavicular joint problems in athletes and new methods of management

The acromioclavicular (AC) complex consists of bony and ligamentous structures that stabilize the upper extremity through the scapula to the axial skeleton. The AC joint pathology in the athlete is generally caused by 1 of 3 processes: trauma (fracture, AC joint separation, or dislocation); AC joint arthrosis (posttraumatic or idiopathic); or distal clavicle osteolysis. This article presents systematically the relevant anatomy, classification, evaluation, and treatment of these disorders. Management of AC joint problems is dictated by the severity and chronicity of the injury, and the patient's needs and expectations.

Acromioclavicular joint injuries: diagnosis and management

Acromioclavicular joint injuries represent nearly half of all athletic shoulder injuries, often resulting from a fall onto the tip of the shoulder with the arm in adduction. Stability of this joint depends on the integrity of the acromioclavicular ligaments and capsule as well as the coracoclavicular ligaments and the trapezius and deltoid muscles. Along with clinical examination for tenderness and instability, radiographic examination is critical in the evaluation of acromioclavicular joint injuries. Nonsurgical treatment is indicated for type I and II injuries; surgery is almost always recommended for type IV, V, and VI injuries. Management of type III injuries remains controversial, with nonsurgical treatment favored in most instances and reconstruction of the acromioclavicular joint reserved for symptomatic instability. Recommended techniques for stabilization in cases of acute and late symptomatic instability include screw fixation of the coracoid process to the clavicle, coracoacromial ligament transfer, and coracoclavicular ligament reconstruction. Biomechanical studies have demonstrated that anatomic acromioclavicular joint reconstruction is the most effective treatment for persistent instability.

The coracoidal insertion of the coracoclavicular ligaments: an anatomic study

BACKGROUND

Current surgical procedures restoring a dislocated acromioclavicular joint aim to perform an anatomically correct and biomechanically stable reconstruction. However, the coracoidal insertions for the coracoclavicular ligaments have not yet been defined.

PURPOSE

The objective was to evaluate dimension and orientation of the coracoclavicular footprints with respect to bony landmarks for use in anatomic reconstruction of the coracoclavicular ligament complex.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Twenty-three (17 female, 6 male) fresh-frozen cadaveric human shoulders were dissected, and the coracoclavicular ligaments including the coracoid and the lateral clavicle were exposed. After measurement of bony coracoidal dimensions, the ligaments were dissected and the insertion sites as well as the footprint centers were identified and marked. Each coracoclavicular insertion dimension and its distance to the bony landmarks was recorded. Sex-related differences were calculated.

RESULTS

The mean total coracoidal length was 43.1 +/- 2.2 mm. The distance from the tip of the coracoid to the precipice, the point at which the undersurface of the coracoid changes from a horizontal to a vertical direction, measured 20.3 +/- 2.6 mm. The mean distance from the conoidal center to the medial coracoidal boarder and to the precipice was 1.7 +/- 0.7 mm and 16.4 +/- 2.4 mm, respectively. The mean distance from the trapezoidal center to the medial border and to the precipice was 8.7 +/- 3 mm and 10.9 +/- 2.4 mm, respectively. The mean distance between the footprint centers was 10.1 +/- 4.2 mm.

CONCLUSION

Reproducible dimensions and orientation of the coracoclavicular footprints are given.

CLINICAL RELEVANCE

Coracoidal anatomic landmarks can be used intraoperatively for an anatomic reconstruction of the coracoclavicular ligaments.

The anatomic reconstruction of acromioclavicular joint dislocations using 2 TightRope devices: a biomechanical study

BACKGROUND

For the reconstruction of acromioclavicular (AC) joint separation, several operative procedures have been described; however, the anatomic reconstruction of both coracoclavicular ligaments has rarely been reported.

PURPOSE

The aim of this biomechanical study is to describe a new procedure for anatomic reconstruction of the AC joint.

STUDY DESIGN

Controlled laboratory study.

MATERIALS AND METHODS

Forty fresh-frozen cadaveric shoulders were tested. Cyclic loading and a load-to-failure protocol was performed in vertical (native, n = 10; reconstructed, n = 10) and anterior directions (native, n = 10; reconstructed, n = 10) on 20 AC joints and repeated after anatomic reconstruction. Reconstruction of conoid and trapezoid ligaments was achieved by 2 TightRope devices (Arthrex, Naples, Florida). Dynamic, cyclic, and static loading until failure in vertical (n = 5) and horizontal (n = 5) directions were tested in native as well as reconstructed joints in a standardized setting.

RESULTS

The native coracoclavicular ligaments in static load for vertical force measured 598 N (range, 409-687), elongation 10 mm (range, 6-14), and stiffness 99 N/mm (range, 67-130); static load for anterior force was 338 N (range, 186-561), elongation 4 mm (range, 3-7), and stiffness 140 N/mm (range, 70-210). The mean maximum static load until failure in reconstruction for vertical force was 982 N (range, 584-1330) (P =.001), elongation 4 mm (range, 3-6) (P < .001), and stiffness 80 N/mm (range, 66.6-105) (P = .091); and for anterior static force 627 N (range, 364-973) (P < .001), elongation 6.5 mm (range, 4-10) (P = .023), and stiffness 78 N/mm (range, 46-120) (P = .009). During dynamic testing of the native coracoclavicular ligaments, the mean amount of repetitions (100 repetitions per stage, stage 0-100 N, 100-200 N, 200-300 N, etc, and a frequency of 1.5 Hz) in native vertical direction was 593 repetitions (range, 426-683) and an average of 552 N (range, 452-683) load until failure. In vertical reconstructed testing, there were 742 repetitions (range, 488-893) (P = .222) with a load until failure of 768 N (range, 486-900) (P = .095). In the anterior direction load, the native ligament failed after an average of 365 repetitions (range, 330-475) and an average load of 360 N (range, 307-411), while reconstructed joints ended in 549 repetitions (range, 498-566) (P = .008) with a load until failure of 547 N (range, 490-585) (P = .008). In all testing procedures, a preload of 5 N was performed.

CONCLUSION

The anatomic reconstruction of the AC joint using TightRope is a stable and functional anatomic reconstruction procedure. The reconstruction technique led to favorable in vitro results with equal or even higher forces than native ligaments.

CLINICAL RELEVANCE

Through anatomic repair, stable function of the AC joint can be achieved in an anatomic manner.

Biomechanical evaluation of an augmented coracoacromial ligament transfer for acromioclavicular joint instability

PURPOSE

The purpose of this study was to establish and biomechanically evaluate an augmented coracoacromial ligament (CAL) transfer technique that eliminates the biomechanical drawbacks of the conventional Weaver-Dunn procedure and restores the intact joint kinematics.

METHODS

The acromioclavicular joints of 12 human shoulder specimens were tested for anterior, posterior, and superior translation during cyclic loading as well as for stiffness and ultimate tensile strength in a subsequent load-to-failure protocol. After luxation, the specimens were randomly assigned to 2 treatment groups: CAL transfer and polyester-augmented CAL transfer. For the coracoclavicular augmentation, a strong 1-mm polyester loop was intertwined between 2 flip buttons for coracoid and clavicle fixation. Only the medial half of the CAL was transferred and fixed in a medialized position at the clavicle.

RESULTS

Translational testing showed significantly higher anterior (12.1 mm), posterior (9 mm), and superior (13.4 mm) translation for the CAL transfer technique as compared with the native joint (5.4 mm, 3.3 mm, and 3.4 mm, respectively) and the modified augmented CAL transfer procedure (6.2 mm, 4.2 mm, and 3.6 mm, respectively) (P < .05). No significant differences were found between the intact acromioclavicular joint and the augmented CAL transfer regarding anterior and superior translation. Posterior translation was significantly higher for the augmented CAL transfer compared with the native joints (P = .033), but the quantitative difference was small (0.8 mm).

CONCLUSIONS

The augmented CAL transfer using the medial half of the CAL and supplementing it with a strong 1-mm polyester loop intertwined between 2 flip buttons for coracoid and clavicle fixation has been shown to restore anterior and superior translation of the native acromioclavicular joint.

CLINICAL RELEVANCE

The promising biomechanical in vitro results must be interpreted in the context of clinical investigations regarding the risk of bony erosion resulting from the use of permanent suture material.

Arthroscopically assisted coracoclavicular ligament reconstruction for chronic acromioclavicular joint instability

The treatment of symptomatic chronic acromioclavicular joint dislocations can be challenging. Different surgical procedures have been described in the literature. We present an arthroscopically assisted stabilization using a gracilis tendon transclavicular-transcoracoid loop technique augmented with a Tight-Rope (Arthrex, Naples, FL, USA). In contrast to the classic Weaver-Dunn procedures this technique is designed to stabilize the acromioclavicular joint by recreating the anatomy of the coracoclavicular ligaments via a minimal invasive approach.