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

Review of Weaver and Dunn on treatment of acromioclavicular injuries, especially complete acromioclavicular separation

This classic discusses the original publication "Treatment of acromioclavicular injuries, especially complete acromioclavicular separation" by Weaver and Dunn, which collaborated to develop a technique for acromioclavicular joint reconstruction in 1972. Their surgical technique described resection of 2 cm of the distal clavicle and transfer of the acromial end of the coracoacromial ligament into the medullary canal of the distal clavicle. (modified) Weaver-Dunn procedures have been regarded as one of the most effective techniques to treat complete acromioclavicular joint dislocation for a long time. However, anatomic reconstructions have taken over this position since recent biomechanical studies have demonstrated superior results. Although the Weaver-Dunn procedure has fallen out of favour, it remains of historical significance. For this reason, this review will comprise the historical overview of the Weaver-Dunn procedure, the men behind the eponym and the clinical implication then and now.

Optimal Management of Acromioclavicular Dislocation: Current Perspectives

Injuries to the acromioclavicular (AC) joint are common and mostly involve younger, male individuals. Whereas the majority of AC joint dislocations can be treated nonoperatively with a trial of immobilization, pain medication, cryotherapy, and physiotherapy, there are patients that do not respond well to conservative management and may require surgical treatment. Identifying and treating these patients according to the type and chronicity of AC joint dislocation is paramount. To date, a myriad of surgical techniques have been proposed to address unstable AC joint dislocations and are indicative of the uncertainty that exists in optimal management of these injuries. Historically research has focused on the restoration of the coracoclavicular ligament complex. However, recently the importance of the acromioclavicular capsule and ligaments has been emphasized. This review aims to provide the reader with an overview of current treatment strategies and research, as well as future perspectives.

Biomechanical evaluation of acromioclavicular joint reconstructions using a 3-dimensional model based on the finite element method

BACKGROUND

This study aims to evaluate the influence of stabilization of acromioclavicular (AC) joint dislocation through the modified Weaver-Dunn technique and coracoclavicular (CC) ligaments using the finite element method. The goal is to determine which surgical technique allows behavior that is most similar to the joint, guaranteeing the necessary stability without restricting joint movements for the considered conditions.

METHODS

The analysis is based on the three-dimensional finite element models. The control group of this study is represented by a three-dimensional model of the whole structure based on finite element methods.

FINDINGS

The finite element models showed the stress and displacement values found in the intact acromioclavicular joint and surgical procedures. It was concluded that transferring the coracoacromial ligament to stabilize the acromioclavicular joint did not have a positive impact on the outcome.

INTERPRETATION

The finite element analysis on the treatment of acromioclavicular dislocation presented here provides medical teams with new parameters for choosing a suitable surgical procedure in the occurrence of acromioclavicular dislocation. The development and validation of the finite element models allow the variation of the conditions and enables different surgical configurations to be simulated.

Acromioclavicular Joint Stabilization: A Biomechanical Study of Bidirectional Stability and Strength

Background:

It is important to restore horizontal and vertical stability to the acromioclavicular (AC) joint when treating dislocations of this joint. Most surgical stabilization techniques of the AC joint have primarily addressed the coracoclavicular ligament complex; however, these techniques may not satisfactorily restore horizontal stability to the AC joint.

Purpose:

To evaluate the strength and bidirectional stability of 3 AC joint stabilizing techniques in a cadaveric model.

Study Design:

Controlled laboratory study.

Methods:

A total of 24 cadaveric shoulders were randomly allocated to 3 treatment groups. For each group, a standardized AC joint stabilizing procedure was performed, and the specimens were potted for mechanical testing. The following reconstruction techniques were used: a single clavicular tunnel for group A, a double clavicular tunnel for group B, and a double clavicular tunnel plus suture fixation across the AC joint for group C. The specimens underwent cyclic loading in the horizontal and vertical planes and then load to failure. Eight control specimens also underwent cyclic loading in both planes. Construct stiffness during cyclic loading, change in displacement after cyclic loading in both planes, load to failure in the vertical plane, and mode of failure were evaluated, and stiffness was compared among the treatment groups as well as with a control group.

Results:

There was a decrease in joint stiffness for all groups, including controls, during the cyclic loading. Compared with controls, all 3 treatment groups demonstrated equivalent stiffness and displacement in the vertical plane. In the horizontal plane, all 3 treatment groups demonstrated decreased stiffness, increased displacement, or both when compared with controls. When groups were compared, no treatment arm proved superior regarding stiffness or displacement in either plane. Load-to-failure testing of the 3 treatment groups in the vertical plane demonstrated construct strength and stiffness comparable with reports for the native AC joint. The mode of failure was predominantly fracture at the point of fixation to the testing apparatus.

Conclusion:

There was no difference in bidirectional strength and stability between the single– and double–clavicular tunnel techniques of coracoclavicular reconstruction. The addition of a stabilizing suture across the AC joint does not improve horizontal stability in the absence of repair of the AC joint capsule and deltotrapezial fascia.

Clinical Relevance:

This laboratory study provides further evidence of the importance of the AC joint capsule and associated soft tissues in affording horizontal stability to that joint. Information from this and subsequent studies utilizing a bidirectional model can influence the choice of surgical procedure in the clinical treatment of AC joint dislocations.

Axial-Plane Biomechanical Evaluation of 2 Suspensory Cortical Button Fixation Constructs for Acromioclavicular Joint Reconstruction

BACKGROUND

Although numerous suture-button fixation techniques for acromioclavicular (AC) joint reconstruction have been validated with biomechanical testing in the superior direction, clinical reports continue to demonstrate high rates of construct slippage and breakage.

PURPOSE

To compare the stability of a novel closed-loop double Endobutton construct with a commercially available cortical button system in both the axial and superior directions.

STUDY DESIGN

Controlled laboratory study.

METHODS

Six matched pairs of fresh-frozen cadaveric upper extremities were anatomically dissected and prepared to simulate a complete AC joint dislocation. One side of each pair was reconstructed with the double Endobutton (DE) construct and other side with the dog bone button (DB) construct. The specimens were then tested using a materials testing machine, determining initial superior and axial displacements with a preload, and then cyclically loaded in the axial direction with 70 N for 5000 cycles. Displacement was again measured with the same preloads at fixed cycle intervals. The specimens were then loaded superiorly to failure.

RESULTS

At 5000 cycles, the mean axial displacement was 1.7 mm for the DB group and 1.2 mm for the DE group (P = .19), and the mean superior displacement was 1.1 mm for the DB group and 0.7 mm for the DE group (P = .32). Load at failure was similar (558 N for DE, 552 N for DB; P = .96). There was no statistically significant difference in the modes of failure.

CONCLUSION

Biomechanical testing of both constructs showed similar fixation stability after cyclical axial loading and similar loads to failure.

CLINICAL RELEVANCE

The strength of both constructs after cyclical loading in the axial plane and load-to-failure testing in the superior plane validate their continued clinical use for achieving stability in AC joint reconstruction procedures.

Comparing mini-open and arthroscopic acromioclavicular joint repair: functional results and return to sport

INTRODUCTION

Acromioclavicular joint (ACJ) dislocation is a common injury that can result from sports activities. The surgical technique for the treatment of Type III and Type IV injuries, according to the Rockwood classification, remains controversial. The purpose of the study was to determine the functional outcome after minimally invasive and arthroscopic surgery. The mini-open surgery was done with MINAR^® system, whereas the arthroscopic technique was done with Dog Bone^TM Button.

STUDY DESIGN

Retrospective Cohort study.

METHODS

We reviewed 31 who were surgically treated for acute acromioclavicular dislocation Type III and Type IV (2012-2015). We excluded subjects with chronic dislocation or other injury. We selected 16 patients (average age 37).  Half of the sample patients were treated with mini-open surgery with the MINAR^® system, and the other half of the patients were treated with the Dog Bone arthroscopic technique. The Constant Shoulder Score, the Oxford Shoulder Score, the Simple Shoulder Test and the Subjective Patient Outcome for Return to Sports (SPORTS) score were used to assess functional outcome of the treated shoulder.

RESULTS

Mean follow-up was 13 months (range 6-27 months). The mean Constant Shoulder Score was 91.10 (range 82.76-96.66), Oxford Shoulder Score was 46.19 (range 42.00-48.00), the Simple Shoulder Test was 10.50 (range 9.00-12.00), and the SPORTS score was 7.88 (range 3-10). There is a statistically significant difference between the sample operated with the mini-open surgery and the group operated with arthroscopic technique. The probability of return to their sport, according to the results of the SPORTS score, was significantly higher for patients treated with the MINAR^® system (p < 0.001). However, the objective parameter of Constant scale is statistically better in patients operated by arthroscopic technique (p < 0.05; p < 0.001).

CONCLUSION

Restoration of ACJ anatomy is the key to a successful therapy. The surgical technique should be personalized. The miny-open surgery and also the arthroscopic surgery are adequate with good clinical results. However, according to the SPORTS score, the patients treated with mini-open surgery returned to their sport with less pain and better performance than those belonging to the other group.

Biomechanical evaluation of 3 stabilization methods on acromioclavicular joint dislocations

BACKGROUND

Traumatic acromioclavicular (AC) joint dislocations can be addressed with several surgical stabilization techniques. The aim of this in vitro study was to evaluate biomechanical features of the native joint compared with 3 different stabilization methods: locking hook plate (HP), TightRope (TR), and bone anchor system (AS).

HYPOTHESIS

The HP provides higher stiffness than the anatomic reconstruction techniques.

STUDY DESIGN

Controlled laboratory study.

METHODS

A new biomechanical in vitro model of the AC joint was used to analyze joint stability after surgical repair (HP, TR, and AS). Eighteen cadaveric specimens were randomized for bone density and diameter in the midclavicle section. Joint stiffness was measured by applying an axial load and a defined physiological range of motion for internal and external rotations and upward and downward rotations. Data were recorded at 3 stages: for the native joint after dissecting the AC ligaments, directly after repair, and after axial cyclic loading (1000 cycles with 20 and 70 N at 1 Hz). To evaluate which implant mimics physiological joint properties best, axial stiffness of vertical stability was assessed in combination with rotation. Finally, static loading in the superior direction was applied until failure of the joints occurred.

RESULTS

Axial stiffness of the TR and AS groups was 2-fold higher than for the HP group and the native joint (67.1, 66.1, and 22.5 N/mm, respectively; P < .004). Decreased load-to-failure rates were recorded in the HP group compared with the TR and AS groups (248.9 ± 72.7, 832.0 ± 401.4, and 538.0 ± 166.1 N, respectively). The stiffness of the rotations was not significantly different between the treatment methods but was lower in horizontal and downward rotations compared with the native state. Thus, native AC ligaments contributed a significant share to joint stiffness.

CONCLUSION

The TR and AS groups demonstrated higher vertical load capacity. Compared with the TR and AS, the HP demonstrated an axial stiffness closest to the native joint. For restoring physiological properties, reconstruction of the AC ligaments may be necessary.

CLINICAL RELEVANCE

The results show different biomechanical properties of the HP and anatomic reconstructions.

Operative treatment of acute acromioclavicular joint injuries graded Rockwood III and IV: risks and benefits in tight rope technique vs. k-wire fixation

Background

Operative treatment of acromioclavicular joint injuries is recommended for higher degree dislocations. Recently a new option has become available with the minimally-invasive tight rope technique. Whereas clinical studies justify the medical use, risks and benefits remain unclear. Therefore, this study analyzed these facts associated with this procedure and compared them to K-wire fixation.

Material and Methods

A retrospective analysis was performed of patients surgically treated either with the TightRope™-technique (TR) or K-wires (KW) for a first event isolated Rockwood type III or higher acromioclavicular joint dislocation between 2004 and 2011. Timing for surgery, surgical duration, length of hospital stay, costs, complications and outpatient visits were recorded.

Results

41 patients were included (TR: n = 18; KW: n = 23) with comparable demographics and injury severity. A trend towards shorter operation time was seen in the TR group (TR: 64.3 ±19.8 min. vs. KW: 80.9 ±33.7 min., n.s.) A tendency for lower total operation theater costs was seen in the TR group (TR: 474 ±436.5€ vs. KW: 749.1 ±31.2€, n.s.). Patients from the TR group left hospital earlier (TR: 2 ±1d vs. KW: 3.6 ±1.8d, p = 0.002). Severe complications (i.e. a fracture of the clavicle or nerve damage) occurred in neither of the groups. Early loss of reduction (n = 1) and impaired wound healing (n = 2) was seen in the TR group. Migrating K-wires (n = 4), loss of reduction (n = 1) and impingement syndrome (n = 1) were recorded in the KW group.

Conclusion

Usage of the tight rope technique offered advantages, such as being a safe minimally-invasive technique and showed a tendency towards shorter operation time, and lower physician- and total operation and theater costs. Material costs were significantly higher for this device but patients were discharged earlier. The influence of different clinical long-term results on the financial outcome needs to be evaluated in further studies.

Biomechanical properties of repairs for dislocated AC joints using suture button systems with integrated tendon augmentation

PURPOSE

To evaluate the biomechanical performance of different techniques for CC reconstruction using suture button systems with integrated tendon augmentation. Hypothesis was that (1) reconstructions using a cortical button combined with a biological augmentation (semitendinosus allograft) will demonstrate improved stability than a modified Weaver-Dunn procedure and (2) constructs using two tunnels at the clavicle for fixation will show superior horizontal stability than single-tunnel constructs.

METHODS

The acromioclavicular joints of 47 cadaveric shoulders were tested for anterior, posterior, and superior translations (70 N load) and maximal load to failure (superior). Shoulders were assigned to 4 groups: (1) native (n = 18) and after sectioning the AC and CC ligaments; (2) CC reconstruction with 1 clavicular and 1 coracoid tunnel (GR-ST) augmented with semitendinosus graft (n = 15); (3) CC reconstruction augmented with semitendinosus tendon (GR-DT) with 2 clavicular and 1 coracoid tunnel (n = 8); and (4) modified Weaver-Dunn reconstruction (n = 6).

RESULTS

The Weaver-Dunn demonstrated statistically more translation than the native joint for posterior direction (P = 0.038). The GR-ST had significantly less translation than the Weaver-Dunn for anterior and posterior translations (P = 0.003, P = 0.004) and compared to the native for superior translation (P = 0.028). The GR-DT differed significantly in anterior and posterior translations compared to the Weaver-Dunn (P = 0.002, P = 0.001). The modified Weaver-Dunn failed at significantly less load to failure compared to all other groups (P = 0.002, P = 0.002, P = 0.005). There was no significant difference between the native and the other reconstructions.

CONCLUSION

The evaluated techniques for isolated CC ligament reconstruction (GR-ST) in AC joint dislocation showed biomechanical stability superior to the modified Weaver-Dunn procedure and obtained similar measures compared to the native control. A modified technique (GR-DT), which used two fixation points at the clavicle, did not result in decreased horizontal or vertical translation and therefore no superiority of the GR-DT technique could be shown compared to the GR-ST.

LEVEL OF EVIDENCE

Controlled laboratory study.

[Revision and salvage procedures for injuries to the acromioclavicular joint]

Failed conservative treatment or surgical procedures for acute AC joint seperations create the demand for revision or salvage procedures to successfully treat persistent AC joint instability. Besides the classic Weaver-Dunn procedure and its modifications lately new procedures combining a more or less rigid implant for primary stability with a biologic augmentation using an autologous tendon graft have been developed. These procedures are performed arthroscopically or arthroscopically assisted.

Outcome of conjoined tendon and coracoacromial ligament transfer for the treatment of chronic type V acromioclavicular joint separation

BACKGROUND

Numerous surgical methods are used to treat acromioclavicular (AC) joint dislocations, and an anatomical reconstruction using a free tendon graft has attracted considerable attention, particularly for chronic cases. The purpose of this study was to introduce the results of lateral half conjoined tendon (LHCT) and coracoacromial ligament (CAL) transfer for chronic type V injuries.

MATERIALS AND METHODS

A retrospective evaluation was performed on the clinical and radiographic outcomes of the 12 patients who underwent LHCT and CAL transfer for chronic type V AC injuries and had been followed for 2 years postoperatively. All 12 patients were males with a mean age of 37.3 ± 7.7 years (range: 26-49 years) at surgery. The causes of the injury were traffic accidents (five), falls (three) and sports injuries (four). The mean time elapsed between trauma and surgery was 12.5 ± 5.4 weeks (range: 7-22 weeks).

RESULTS

No reduction loss was observed at the final follow-up. The postoperative coracoclavicular (CC) distance was 8.9 ± 1.6mm, which represented a significant improvement versus the preoperative status (20.3 ± 3.0mm; p < 0.001), and no significant difference was observed between the injured and uninjured contralateral sides (8.7 ± 0.8mm), postoperatively (p = 0.619). The temporary use of a Steinman pin for AC fixation did not cause any complications. On the other hand, there were eight cases of mild radiographic arthrosis at the AC joint and two cases of heterotopic ossification of the CC space, although neither affected the functional outcomes. The mean modified UCLA score was 18.5 ± 2.1 (range: 12-20), which represented an excellent result in 11 of the 12 cases. The single case with a poorer postoperative score had a pre-existing brachial plexus injury.

CONCLUSIONS

Despite the small study cohort, the results of LHCT and CAL transfer in chronic type V AC separation are promising. CAL transfer alone has been shown to be biomechanically insufficient for an AC reconstruction, particularly in chronic situations. The advantage of LHCT transfer is that it does not require a distant donor site or incur the costs of an allograft or implant.

Biomechanical comparison of arthroscopic repairs for acromioclavicular joint instability: suture button systems without biological augmentation

BACKGROUND

Arthroscopic procedures for reconstruction of acromioclavicular (AC) joint separations are increasingly used in clinical practice. Multiple surgical techniques exist, but there are still few data on biomechanical performances of commonly used arthroscopic techniques and fixation methods.

HYPOTHESIS

Single and double clavicular tunnel reconstructions show comparable primary stability with a modified Weaver-Dunn procedure, and double tunnel constructs show superior horizontal stability.

STUDY DESIGN

Controlled laboratory study.

METHODS

The AC joints of 40 cadaveric shoulders were tested for anterior, posterior, and superior translation (70-N load) and maximal load to failure (superior) with the MTS 858 Bionix II Servohydraulic testing system. Shoulders were assigned to 4 groups: (1) native (n = 18), (2) coracoclavicular (CC) reconstruction with 1 clavicular and 1 coracoid tunnel (SCT) fixed with a suture pulley and 2 buttons (n = 8), (3) CC reconstruction with 2 clavicular and 1 coracoid tunnel (DCT) fixed with a suture pulley and 3 buttons (n = 8), and (4) modified Weaver-Dunn reconstruction (n = 6).

RESULTS

Native specimens showed a mean anterior translation of 7.92 mm (±1.69 mm), a mean posterior translation of 7.84 mm (±2.09 mm), and a superior translation of 4.28 mm (±1.81 mm). Maximal load to failure was 579.44 N (±148.01 N). The SCT technique showed a mean anterior translation of 5.81 mm (±1.16 mm), posterior translation of 8.30 mm (±1.94 mm), and a superior translation of 2.28 mm (±0.52 mm). The maximal load to failure was 591.35 N (±231.17 N). Anterior and superior translations were significantly less compared with the native specimen (P = .005 and P = .003). The DCT technique had an anterior translation of 4.68 mm (±0.6 mm), posterior translation of 6.85 mm (±0.83 mm), and superior translation of 2.09 mm (±0.86 mm). The mean maximal load to failure was 651.16 N (±226.93 N). Anterior and superior translations were significantly less compared with the native specimens (P = .000 and P = .001). No statistically significant differences were shown between SCT and DCT reconstruction for all measurements (P > .05). One reconstruction of the modified Weaver-Dunn procedure failed directly after mounting it into the testing device. The remaining 5 showed a mean anterior translation of 11.36 mm (±3.17 mm), a mean posterior translation of 13.51 mm (±2.21 mm), and a mean superior translation of 3.31 mm (±0.47 mm). Anterior and posterior translations were significantly increased compared with the native specimen (P = .019 and P = .000). The mean maximal load to failure measured 311.13 N (±52.2 N) and was significantly less compared with the native specimen (P = .000). The Weaver-Dunn technique showed significantly less maximal load to failure and more anterior and posterior translation compared with SCT and DCT (P ≤ .05).

CONCLUSION

Isolated reconstruction of the CC ligaments using single and double clavicular tunnel techniques results in a high load to failure for superior translation, which is equal to the native stability, and less translation in all 3 directions as well as higher superior stability when compared with the modified Weaver-Dunn procedure. A potential drawback is the risk of coracoid fracture, as the high load to failure of the device may exceed load to failure of cortical bone prior to device breakage.

CLINICAL RELEVANCE

Single clavicular tunnel arthroscopic reconstructions of the coracoacromial ligaments show good biomechanical results.

Reconstrução coracoclavicular com enxerto tendíneo na luxação acromioclavicular crônica

OBJETIVO: Apresentar os resultados radiográficos e funcionais de pacientes submetidos ao tratamento da luxação acromioclavicular crônica com reconstrução dos ligamentos coracoclaviculares com enxerto de tendão semitendíneo. MÉTODO: Quinze pacientes, entre abril de 2007 e junho de 2008, foram submetidos a reconstrução dos ligamentos coracoclaviculares com enxerto tendíneo. Dois pacientes foram excluídos do estudo por seguimento inadequado. Treze pacientes foram seguidos clinicamente e radiograficamente, em média, por 16 meses (12-26 meses). Os pacientes foram submetidos a avaliação clinica pré e pós-operatória, utilizando os escores Constant e UCLA. Radiografias pré e pós-operatórias foram comparadas. RESULTADOS: Neste grupo de 13 pacientes com seguimento mínimo de um ano, o escore Constant variou de 60,9 (26-88) na avaliação pré-operatória para 87 (60-98) na última avaliação no período pós-operatório. O escore UCLA foi de 16,8 (11-27) no pré operatório para 33 (29-35) na avaliação pós-operatória (p=0,001). No controle radiográfico com um ano de pós-operatório, encontramos 12 pacientes (92%) com a distância coracoclavicular igual comparando o ombro operado ao contralateral. Todos os ombros operados apresentavam-se sem translação na direção antero-posterior no perfil axilar. CONCLUSÃO: O resultado funcional e radiográfico foi muito satisfatório nos pacientes submetidos à reconstrução das luxações acromioclaviculares crônicas, com baixo indice de recidiva. Nivel de Evidência IV, série de casos.

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.

Failure of coracoclavicular artificial graft reconstructions from repetitive rotation

PURPOSE

To assess how suture type and suture construct in an augmented Weaver-Dunn reconstruction affect coracoclavicular sling failure and rotary stability.

METHODS

Fifteen cadaveric shoulders were tested in rotation about the long axis of the clavicle with 10 lb of simulated arm weight. The clavicle was rotated 50 degrees about its long axis, and the applied torque was recorded. Next, modified Weaver-Dunn reconstruction was conducted. Two types of coracoclavicular sling (opposed drill holes through the clavicle and complete loop around the clavicle) were tested by use of 3 different sutures (FiberWire [Arthrex, Naples, FL], Mersilene tape [Ethicon, Somerville, NJ], and braided polydioxanone [PDS] [Ethicon]). For each sling-suture combination, the joint was retested over 50 degrees of rotation and then cycled over 40 degrees of rotation for 15,000 cycles or until failure.

RESULTS

After modified Weaver-Dunn reconstruction with either sling construct, mean torque over 50 degrees of acromioclavicular rotation was significantly reduced in posterior (P < .0001) and anterior (P < .0001) rotation, with any suture material tested. When the coracoclavicular sling was placed through opposed drill holes, no wear to the bone or suture was observed. When the sling material was looped around the clavicle, FiberWire and PDS resulted in abrasion of soft tissue and periosteum. In all cases sawing motion between bone and suture was observed at the coracoid. The FiberWire itself failed at a mean of 8,213 cycles. Some wear was noted in the Mersilene tape. PDS suture showed no wear.

CONCLUSIONS

In a cadaveric model of modified Weaver-Dunn reconstruction, a coracoclavicular suture loop was used to augment coracoacromial ligament transfer. Suture loops secured around the entire clavicle were shown to contribute to increased abrasive wear. Securing suture loops through opposed drill holes in the clavicle resulted in decreased abrasive wear.

CLINICAL RELEVANCE

Proper selection of suture type and suture construct may affect the failure rate of augmented Weaver-Dunn reconstructions.