Despite the high frequency of acromioclavicular (AC) joint dislocations, the optimal treatment remains controversial. Conservative management and several techniques of surgical intervention have been well described. Each of these techniques has had numerous modifications with inherent potential complications.1 However, a high incidence of intra- or postoperative complications, such as hardware failure or migration, fracture of the clavicle or coracoid process, distal clavicle osteolysis, coracoclavicular calcification, and infection of fixation or augmentation devices, have been reported in many series.2–5
The efficacy of the button technique—either double or triple button—in the treatment of these injuries has not been well defined. A few authors have published on the early result of the AC joint separations with the application of the button fixation, but no evidence exists to focus on the long-term outcome of the early reconstruction of severe AC joint dislocation using the button technique.6,7 This series includes all patients with AC joint dislocation Rockwood type IV and V who were treated at the authors’ institution with the flipptack fixation button technique from December 2006 until December 2009. The purposes of the current study were to analyze the clinical, functional, and radiographic results and to determine the impact of these injuries on the shoulder joint. The authors hypothesized that the flipptack fixation button technique is an effective treatment for the severe AC joint separations and the result will be maintained over time.
Materials and Methods
This is a retrospective study that was conducted after approval by the Research and Ethics Committee at the authors’ institution. All study participants signed an informed consent form. Between December 2006 and December 2009, the authors admitted 135 consecutive patients with 135 dislocations of the AC joint. Conservative treatment, other types of surgical intervention, and the flipptack fixation button technique were used for the management of these injuries. Inclusion criteria for this retrospective review were an AC joint dislocation Rockwood type V and IV treated with the flipptack fixation button technique in the first 2 weeks after the injury in patients without previous shoulder symptoms. Eighty-two patients did not meet the inclusion criteria and were excluded from this study.
According to the Rockwood classification, 39 dislocations were type I, 10 were type II, and 33 were type III. All of these injuries were treated conservatively. Fifty-three patients met the inclusion criteria. Sufficient data were obtained in 50 AC dislocations. Three patients were unable to return for a formal follow-up because they had moved to another location. The mechanisms of injury included a fall from a height (n=27), a road traffic accident (n=9), and a sports-related injury (n=14). There were 38 men and 12 women with an average age of 35.5 years (range, 20 to 71 years). The dominant arm was involved in 32 patients. The pre- and postoperative profile of this study is provided in Table 1.
To determine the severity of the AC joint separation, standard anteroposterior radiographs, along with the axillary lateral and Zanca views of both shoulders, were supplemented in all cases by stress radiographs, with patients having 5 kg of traction on each wrist while standing and pulling back both shoulders. The axillary lateral view contributed significantly to the determination of type IV AC joint separations. The inferior and posterior dislocation of the distal end of clavicle was seen best on this view. According to the Rockwood classification scheme, 21 (42%) dislocations were type V and 29 (58%) were type IV. Mean coracoclavicular distance in the injured arm was 13.0 mm (range, 9.5–15 mm), and this distance increased in stress radiographs to 13.3 mm (range, 10–15 mm) (Table 2). All injuries were closed. Coexisting injuries to the other osseous structures included patella fracture in 1 patient, tibia fracture in 1 patient, and ipsilateral metatarsal fracture in 2 patients. All operations were performed on a scheduled basis at an average of 4.2 days (range, 0–12 days) by the most senior orthopedic surgeon of this study (D.L.K.).
Mean Coracoclavicular Distance
All patients were placed in the beach chair position. A 3-cm–long incision was made above the edge of the clavicle. The coracoid process was identified and cleared off to the base so thorough access was achieved. After exposing the entire coracoid process, a special aiming device was hooked under the base of the coracoid arch. With the drill guide held in this position, a guide pin was drilled through the posterosuperior surface of the coracoid to the middle of its base and was then over-drilled with a 4.5-mm cannulated reamer to create the coracoid tunnel. The optimal location for the coracoid tunnel placement was considered to be at the posterior aspect of the base of the coracoid near the footprint of the conoid ligament.8
It was necessary to lead the drill through the retainer of the sliding bullet to make sure that the landing wire and the drill were not going too far distally but were stopped by the aiming hook. The already prepared cord construct was placed in the flipptak inserter and then into the drill hole and pushed through with the appropriate pusher. Leaving the flipptack pusher in place, the flipptack was flipped underneath the coracoid by pulling on the cord. After that, the authors proceeded to the preparation of the clavicular tunnel.
In the case of dislocation of the AC joint Rockwood type V and IV, the delta and trapezius fascia is already ruptured and the clavicle lies free. Using a small periosteal elevator, all of the soft tissues overlying the superior surface of the clavicle were freed in a horizontal direction. The clavicle was manually reduced and, following the same steps, a drill hole was created into the top of the clavicle approximately 3 cm medial to the AC joint and midway between the anterior and posterior border of the clavicle. Using a suture awl equipped with a thread loop through the drill hole of the clavicle, the flipptack-cord was pulled through the clavicle. With the AC-repositioner, the clavicle was set to bone and the cord was knotted. The wound was closed in layers. Two authors (D.B., S.T.), who did not participate in either the surgical procedure or the clinical evaluation of the patients and were not aware of the radiographs’ identity, analyzed the radiographic results.
All operations were performed as out-patient procedures. Standard anteroposterior radiographs and stress radiographs with 5 kg of traction added on each wrist were obtained in both shoulders in all patients on the day of discharge. The arm was placed in a Kenny Howard sling for 3 weeks. Passive shoulder mobilization was initiated by the physiotherapist as soon as the postoperative pain had settled. At the end of 2 weeks, waist-level pendulum exercises and gradual active range of motion exercises were begun. Return to contact sports activities was allowed 4 months after the procedure. Depending on the possibility to approach the authors’ institution, all patients were reviewed every 2 to 4 weeks until 6 weeks postoperatively.
Forty-seven (94%) patients were able to return for a formal follow-up at a mean time of 42 months (range, 36 to 49 months) that included clinical and radiographic evaluations. Three patients were unable to return for a formal follow-up. These patients were interviewed via telephone and completed a questionnaire that was mailed back. They also underwent a physical examination by a local physician and the results were forwarded to the authors. Standard anteroposterior radiographs, along with axillary lateral and Zanca views and stress radiographs with 5 kg of traction added on each wrist and the patient standing and pulling back both shoulders, were obtained in both shoulders in all patients. The clinical outcome was evaluated using the Constant score.9,10 To assess the functional outcome of AC joint dislocations, the bother index of the short Musculoskeletal Function Assessment (MFA)11 was completed by all patients.
Anatomic reduction of the AC joint was recorded immediately postoperatively in all patients and was retained in 49 at the last follow-up (Figures 1–2). In 1 patient, the button under the coracoid slipped into the drill hole in the coracoid, which resulted in a loss of the anatomical reduction. That was confirmed on radiographs of the involved AC joint immediately postoperatively. The patient refused to have any other type of reconstructive surgery. No patient had a breakdown or loosening of the fixation button. No deep infection was recorded. Local skin irritation at the surgical approach was recorded in 4 patients; no treatment was needed and the wound healed uneventfully. Coracoclavicular calcification was found in 2 patients. No patient with AC arthritis was recorded in this series. No other reconstructive surgeries were needed in this series.
Preoperative anteroposterior radiograph of the left shoulder showing type IV acromioclavicular joint dislocation.
Final postoperative anteroposterior radiograph of the left shoulder showing an excellent result.
Mean Constant score was 93.04 (range, 84–100). In patients with a type IV dislocation (n=29), mean Constant score was 94 (range, 84 to 100), whereas in patients with a type V dislocation (n=21), mean Constant score was 92 (range, 85–100). Statistical analysis showed no statistically significant difference between the dislocation type and the clinical result at the final follow-up (P=.430; chi-square, 6.820, Kruskal Wallis test).
The average (±SD) short MFA bother score was 20.88±8.95 (range, 2.0–49). The average (±SD) short MFA bother score for the general population was 31.22±20.84 (range, 0–94). Higher scores indicate poorer function. Compared with previously reported scores for patients with upper extremity injury (average, 26.72±18.86; range, 0–77),11 a decreased value in any of the four subsections—recreation and leisure, sleep and rest, work, and family—was demonstrated.
In the healthy side, mean coracoclavicular distance was 8.8 mm (range, 8.5–9.2 mm) and increased to 9.3 mm (range, 8.8–9.7 mm) with 5 kg of traction. Immediately postoperatively, mean coracoclavicular distance was 9.1 mm (range, 8.7–10 mm) and increased to 9.4 mm (range, 8.9–10.2 mm) with 5 kg of traction on the affected arm. At final follow-up, mean coracoclavicular distance was 9.2 mm (range, 8.7–10.2 mm), whereas in the stress radiographs with 5 kg of traction, the mean coracoclavicular distance was 9.5 mm (range, 8.9–10.6 mm). Statistical analysis showed no statistically significant increase of the coracoclavicular distance with traction on the affected arm both immediately postoperatively (P=.227; chi-square, 6.910, Kruskal Wallis test) and for the final follow-up analysis (P=.276; chi-square, 6.319, Kruskal Wallis test).
Various authors have adopted different methods of treatment for the AC joint dislocations. Since 1990, there has been a general consensus in the literature for nonoperative treatment of Rockwood type I and II injuries, initial nonsurgical treatment of type III injuries,12,13 and acute operative intervention for Rockwood type IV to VI injuries.
However, few authors have explicitly studied patients with AC joint dislocation Rockwood type IV and V. Most reports have dealt with the surgical treatment of a limited number of patients with Rock-wood type III and IV AC joint dislocation, and they have focused mainly on the early results such as the shoulder function and the radiographic appearance.14–16 A high incidence of intraoperative complications, such as fracture of the clavicle or the coracoid process, was associated with the use of rigid implants. As a result, coracoclavicular augmentation techniques using a rigid suture cord have been developed.17,18 The principle behind this technique is the use of augmentation of the coracoclavicular ligaments to promote healing without elongation. Biomechanical and clinical studies have shown that stable coracoclavicular stabilization can be reached by combining a polyester nonabsorbable suture with an extracortical fixation button, which is familiar from cruciate ligament surgery.19,20 A further problem is the observation that rotational movement of the clavicle can cause the sutures to cut through the bone or to cause fractures, which make revision a significant challenge. Even under cyclical loading, this device does not cut through the clavicle and is difficult to cause fractures. Combining the fixation button and suture delivers the same pull-out strength as using a conventional suture cerclage and provides almost double the pull-out strength as using a suture anchor augmentation.
Acromioclavicular joint stability on the coronal plane depends mainly on the coracoclavicular ligaments, whereas the superior and inferior portion of the articular AC joint capsule has a fundamental role on the transversal plane.21–23 Common complications after AC joint reconstruction include malreduction of the AC joint or an inability to maintain the anatomical reduction.24,25 Yeow et al26 experienced an early reduction loss rate of 50%, whereas Mayr et al27 reported a reduction loss rate of 28%, with a less satisfactory outcome in these patients. In the current authors’ series, anatomic reduction of the AC joint was achieved in all cases immediately postoperatively. To strengthen the significance of this finding, the anatomical reduction was retained in all but one case at final follow-up. This finding is contrary to most international literature that no type of isolated synthetic, bioreabsorbable, or tendinous loop is able to restore the native coracoclavicular and/or AC ligament complex stiffness, which may reach up to 115 N/mm.23,28–30 It seems that the biomechanical properties of the flipptack fixation system are capable of accomplishing all of the osseous and ligamentous characteristics of the AC anatomy complex.
On the other hand, there is no agreement in the literature regarding the impact of an incomplete reduction of the AC joint on final shoulder function and subsequently on the incidence of secondary late joint osteoarthritis and remaining shoulder discomfort. Several authors found that complete anatomic reduction is not necessary to regain adequate shoulder function, and that the degree of displacement in AC joint dislocations seems not to have a strong influence on the final result.31–33 However, Calvo et al34 stated that the ability to achieve a functional and anatomic reconstruction of the joint anatomy seems to be a beneficial factor to avoid the appearance of secondary late joint osteoarthritis and to avoid persistent shoulder discomfort. In the current study, no patient with AC joint arthritis was recorded at the final follow-up; and the authors strongly believe that this finding is due to the anatomic restoration of the coracoclavicular distance both immediately postoperatively and at final follow-up. Although the free interval between the injury and the appearance of the posttraumatic arthritic changes remains controversial, their findings corroborate with the statement that anatomic reconstruction of the AC joint may lessen the incidence of posttraumatic arthritis of the joint.
The mean Constant score in this series is favorable comparable with many other studies.35,36 Furthermore, the mean MFA score reflects a satisfactory restoration of shoulder function. To the best of the authors’ knowledge, no other study in the literature has evaluated the function of the shoulder joint by taking into consideration the MFA score.
The main limitations of the authors’ study are inherent in its retrospective design. The lack of pre- and postoperative computed tomography scan is also a limitation of the study, considering the information regarding the morphology of the injury and the accuracy of the reduction taken by computed tomography scan. Another limitation of this study is that the follow-up of 42 months has not been clinically and biomechanically proven to be the end point of the final result for this type of injury. On the other hand, the follow-up in this series is one of the longest in present literature and the retrieval rate (94%) for the final examination of eligible patients is also extremely high.
To the authors’ knowledge, the current study is the first attempt to evaluate the midterm outcome of severe AC joint dislocations treated with the application of an artificial ligament that holds the fixation solidly between 2 points while the native ligaments heal. It provides solid clinical and radiographic evidence that once all of the parameters of the initial injury have been well managed and the complications eliminated, AC joint dislocations treated with the flipptack fixation technique have a good chance of obtaining a satisfactory midterm clinical functional and radiologic results that do not seem to deteriorate over time.
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|Patient No./Age, y/Sex||Rockwood Type||Preop Coracoclavicular Distance, mm||Follow-up, mo||Postop Coracoclavicular Distance, mm||Postop Coracoclavicular Distance With 5-kg Weight, mm||Constant Score||Short Bother MFA|
Mean Coracoclavicular Distance
|Side||Without Traction||With Traction|
|Healthy, mm (range)||8.8 (8.5–9.2)||9.3 (8.8–9.7)|
|Injured, preoperatively, mm (range)||12.8 (9.5–15)||13.3 (10–15)|
|Injured, postoperatively, mm (range)||9.1 (8.7–10)||9.4 (8.9–10.2)|
|Injured, final follow-up, mm (range)||9.2 (8.7–10.2)||9.5 (8.9–10.6)|