Surgical treatment of chronic acromioclavicular dislocation with biologic graft vs synthetic ligament: a prospective randomized comparative study
© The Author(s) 2013
Received: 19 April 2012
Accepted: 9 April 2013
Published: 7 May 2013
Acromioclavicular (AC) dislocation involves complete loss of articular contact; it is defined as chronic when it follows conservative management or unsuccessful surgical treatment.
Materials and methods
The study compared the clinical and radiographic outcomes of AC joint stabilization performed in 40 patients with chronic dislocation using a biological allograft (group A) or a synthetic ligament (group B). Demographic data included: M/F: 25/15; mean age: 35 ± 3.2 years; previous surgery in 11 patients, including Weaver–Dunn (3), coracoacromial ligament repair (4), stabilization with K-wires (4). Dislocation was type III in 14 (35 %) and type IV in 26 (65 %) patients. Clinical assessment was with the Constant–Murley score (pre- and postoperative) and with the modified UCLA score. Enrollment started in January 2004 and was completed in March 2008. Patients were evaluated at 1 and 4 years. Postoperative X-rays were examined to assess joint stability in the coronal and axial planes, coracoclavicular ossification, and signs of AC joint osteoarthritis and distal clavicular osteolysis.
The “biological” group achieved significantly better clinical scores than the “synthetic” group at both 1 and 4 years. Poor subjective satisfaction and lower clinical scores were found in the 3 patients (1 from group A and 2 from group B) who experienced complete postoperative dislocation. No significant correlations were found with other radiographic parameters.
The biological graft afforded better clinical and radiographic outcomes than the synthetic ligament in patients with chronic AC joint instability. Fixation to the clavicle constitutes the main weakness of both approaches and needs improving.
KeywordsAcromioclavicular Dislocation Biological Synthetic Stabilization
Acromioclavicular (AC) dislocation involves complete loss of articular contact; a dislocation that is not untreated, is treated conservatively or is treated unsuccessfully by surgery is defined as chronic or inveterate [1, 2]. The AC and coracoclavicular ligaments contribute to anterior–posterior and superior–inferior joint stability, respectively . Complete instability requires rigid fixation of the coracoclavicular ligaments to counteract the AC joint laxity that induces posterior translation of the clavicle. The classification of AC dislocation into 6 degrees of severity, as devised by Rockwood et al. , is still the one most commonly used. While there is consensus on the conservative treatment of types I and II, there is still debate over whether types III to V should be managed surgically [5, 6]. Among the surgical approaches developed to treat acute and chronic AC dislocation, some authors [5, 16, 17, 31] have recommended procedures that restore the original joint anatomy and congruity ; a number of these techniques use biological or synthetic means [8, 9].
This study compares the clinical and radiographic outcomes of surgical AC joint stabilization performed in 40 patients with chronic dislocation using a biological graft or a synthetic ligament.
Materials and methods
This was a prospective randomized clinical study that was designed to ascertain the results of AC joint stabilization using two systems of fixation. All of the patients gave informed consent prior to being included in the study, which was authorized by the local ethical committee (Cometico AV/IRST no. 4442/C012/I5/169) and was performed in accordance with the Ethical Standards of the 1964 Declaration of Helsinki as revised in 2000.
Randomization and sample size
The intent-to-treat population included 40 patients who were fully randomized using a block list that was generated by dedicated software (Research Randomizer, version 3.0, 2011). Envelopes containing the treatment assignments were used to randomize the patients in the two groups. A power analysis was performed in which a 7-point difference in the Constant score between the two groups was required, and a standard deviation of 6 points. Using these parameters, it was calculated that a minimum of 38 subjects were needed.
Demographic data for the patients enrolled in the study
No. of patients
Mean age (years ± SD)
36 ± 4.3
34 ± 2.8
Dominant arm (right/left) (%)
Overhead workers (N°) (%)
Previous surgery (N°) (%)
Degree of dislocation
Eleven patients (27.5 %) had undergone surgical treatment at other institutions as follows: Weaver–Dunn procedure, 3 patients (5 %, 1 in group A and 2 in group B); coracoacromial ligament repair with non-absorbable suture, 4 patients (10 %, 2 in group A, 2 in group B); stabilization with K wires, 4 patients (all group B). All patients complained of pain involving the AC joint and the trapezius that worsened with cross-arm adduction. Active ROM was full in all patients. Weakness beyond 90° of elevation was seen in 5 patients (12.5 %, 2 in group A and 3 in group B). Patients were examined for keloids, AC joint deformity, pain on palpation or during passive mobilization in forward elevation and forced adduction, and joint instability during active mobilization. The Constant–Murley score  was used for clinical assessments before and after the operation and the modified UCLA score  was employed after the operation. This study required that clinical follow-up was performed at 1 and 4 years.
AP and axillary views were examined to assess AC joint stability in the coronal and axial planes, coracoclavicular ossification, signs of osteoarthritis, and distal clavicular osteolysis. X-rays were routinely performed at 2 months; for the requirements of the current study, additional radiograms were taken at 1 and 4 years. Postoperative AC joint stability was assessed according to Rosenorm and Pedersen ; the AC joint was considered to be stable if it showed no dislocation compared to the contralateral joint; subluxated if the dislocation was ≤50 % of the contralateral joint; or dislocated if there was complete dislocation accounting for ≥100 % of the AC joint surface.
Coracoclavicular ossification was deemed incomplete if there was no continuity between clavicle and coracoid process, and complete if it obliterated the coracoclavicular space.
Arthritis was considered to be present if the joint showed joint space narrowing, osteophytes, or sclerosis. Clavicular osteolysis was defined as signs of demineralization around the screws or on the lateral portion of the clavicle.
Clinical scores were expressed as the mean ± standard deviation. Student’s unpaired t test was applied to assess differences between the two groups. Significance was set at 5 % (p < 0.05).
Preoperative and postoperative clinical scores
43.5 ± 6.1
44.05 ± 8.9
88 ± 10
59 ± 7.9
94.2 ± 4.9
85.9 ± 16
Modified UCLA score
17.8 ± 1.8
11.8 ± 4.9
18.2 ± 1.7
15.4 ± 4.2
8.7 ± 3.4
8.4 ± 2.6
3.7 ± 1.6
4.1 ± 1.5
3.9 ± 1.8
3.9 ± 1.4
Group B: the mean Constant–Murley score rose from 44.05 ± 8.9 to 59 ± 7.9 at 1 year (p = 0.0049) and to 85.9 ± 16 at 4 years (p = 0.0089). The mean UCLA score was 11.8 ± 4.9 at 1 year and 15.4 ± 4.2 at 4 years (Table 2).
Subjective satisfaction was good in 17 patients (85 %) from group A and in 14 patients (55 %) from group B. A significant improvement was registered for both groups at 1 year (p = 0.011 and at 4 years (p = 0.014). None of the 40 patients had to change their habits after the operation due to the clinical outcome, including returning to sports or a job.
We did not find a significant difference between the 11 patients previously treated surgically and the study population in their clinical scores and subjective satisfaction.
Postoperative radiographic findings
AC joint arthritis
AC joint arthritis
Subjective satisfaction was not related to the degree of AC joint reduction. Although early postoperative radiographs showed partial loss of AC joint alignment in 3 patients (15 %) from group A and in 6 (30 %) from group B, poor satisfaction was only reported by 4 group B patients (20 %).
At 4 years, <50 % partial dislocation (subluxation), which was found in 4 patients from group A (20 %) and in 4 from group B (20 %), did not correlate with the clinical scores (p > 0.05). Poor subjective satisfaction and lower clinical scores were found in the 3 patients (1 from group A and 2 from group B) who had experienced complete joint dislocation after the operation. No correlation was found between clinical score and coracoclavicular ossification, clavicular osteolysis, or AC joint osteoarthritis.
From 1861  to the present, 60 different surgical procedures have been devised to treat acute and chronic AC joint dislocation, but finding the gold standard has proved an elusive task. In 1972, Weaver–Dunn  proposed the transposition of the coracoacromial ligament to the lateral portion of the clavicle. This approach involves sacrificing the coracoacromial ligament (a humeral stabilizer). The interest in this type of technique, which is based on the assumption that AC joint reduction and anatomical restoration provide more satisfactory outcomes , has recently been revived by the introduction of synthetic ligaments [17, 18] and biological grafts [16, 19]. Techniques based on the transposition of the patient’s tendons that show resistance to cyclic loading, similiar to rigid osteosynthesis (screws, plates, pins, metal or synthetic cerclage) [20, 21] but with lower rates of intra- and postoperative complications, were developed to address these problems [8, 19, 22–24]. Bailey  was the first to report the results of tendon transposition; Dewar and Barrington  used only coracoid transposition and obtained better mid-term outcomes compared with the Weaver–Dunn procedure in young patients . Although transposition of the coracoid with the conjoint tendon reinforces the reconstructed coracoacromial ligament, it involves a greater risk of coracoid fracture and musculocutaneous nerve injury; furthermore, bone cerclage may result in coracoid or clavicle osteolysis.
Materials that are used for artificial ligaments include polyester, Dacron®, Dupont®, Wilmington®, Notthingam® [8, 23], carbon fiber , polytetrafluoroethylene (Gore-Tex®) , and PET (LARS LAC®) . The characteristic interwoven fibers and the porosity of the synthetic ligament promote fibroblast colonization and make the ligament biocompatible and resistant to traction and torsion; nonetheless, intolerance, inflammation, and rejection have been described . Tendon autografts or allografts were initially used in salvage procedures after failed coracoacromial ligament reconstruction . The most widely used allografts are semitendinosus , gracilis, hallux extensor , and peroneus brevis tendons . Biocompatibility, resistance, and rigidity of the system used for joint reduction are crucial for postoperative stability in chronic AC joint dislocation.
Although good outcomes of synthetic  and biological grafts  have been (separately) described in several reports, no single study has, to our knowledge, used both materials and compared them. Although anatomical AC joint reconstruction cannot restore original stability to the joint, tendon grafts provide greater resistance and rigidity than the Weaver–Dunn procedure . Analysis of the results of our study disclosed significantly greater clinical scores in the “biological” compared with the “synthetic” group at both follow-up time points, with mean intergroup differences in Constant–Murley score of >29 points at 1 year and >8.9 points at 4 years, and mean differences in modified UCLA score of 6 points at 1 year and 2.8 points at 4 years.
Eleven out of 40 patients were previously surgically treated using different surgical techniques, which affected the articular biomechanics of the AC joint in different ways, and consequently influenced the homogeneity of the study population. In these patients, we found a higher incidence of periarticular ossifications, clavicular osteolysis, and fibrous adhesions intraoperatively, which made it more difficult to expose the clavicle and acromion. Furthermore, the passage of the graft under the coracoid required a longer surgical step due to the thickening of the surrounding soft tissues. Despite these difficulties, we did not find any significant effects on the clinical scores and AC joint stability based on the X-rays for this subgroup of patients.
Postoperative AC joint stability is the main factor affecting final outcome; the best results were recorded in patients with completely stable joints.
Although the synthetic graft is effective from a biomechanical standpoint, graft shredding and wear and bone remodeling around the screws can compromise mechanical strength over time, particularly in elderly patients and in those with poor clavicle bone thickness or osteoporosis.
Biological grafts provide joint stability in the axial and the coronal planes through suture of the lateral stump of the graft to the acromion, a finding confirmed by recent  and earlier  studies; axial stability appears more difficult to restore using a synthetic graft.
Biological grafts are fixed to the clavicle with resorbable screws and are a valuable option when treating patients with postoperative recurrence of dislocation due to synthetic graft failure.
The major limitations of this study are the small sample size, the lack of inter- and intraobserver data, and the absence of patients treated with tendon autografts.
In conclusion, our findings show that biological grafts provide biocompatible, durable, and effective reduction, as well as better clinical outcomes and radiographic findings than synthetic ligaments, and thus represent the most reasonable alternative to the Weaver–Dunn  procedure in shoulders with chronic AC joint instability. Graft fixation to the clavicle is the major weakness of both procedures and should be improved.
Conflict of interest
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