To our knowledge, the mean duration of follow-up in the present study (12.7 years) is the longest reported follow-up for anatomic CC ligament reconstruction. The overall results of this CC ligament reconstruction technique were very successful, with high mean Constant and ASES scores (97.1 and 98.8, respectively) that were comparable with those in previous studies: the mean Constant and ASES scores were both 98.0 at a mean of 5.2 years as reported by Struhl and Wolfson6, and the mean Constant score was 96.6 at a mean of 17 months as reported by Yoo et al.28. Furthermore, there were no complications such as coracoid and/or clavicular fractures related to the index procedures, and no revision procedures had been performed after a minimum duration of follow-up of 10 years. Interestingly, 2 shoulders (Cases 4 and 17) had pullout of the coracoid button with maintenance of AC joint reduction. This finding suggests that this technique potentially can result in AC stabilization with complete soft-tissue healing even if the artificial ligament is disrupted. Seventeen shoulders (85%) had a CCD ratio of <25% and no posterior AC displacement in conjunction with significantly higher clinical scores compared with those for the shoulders with a CCD ratio of ≥25%; however, degenerative changes still developed in the AC joint.
The satisfactory radiographic results may have been achieved for the following reasons. First, our choice of operative drill diameter (3.5 mm for the clavicular tunnel, 4.5 mm for the coracoid tunnel) and ENDOBUTTON size (4 × 12 mm) were supported by previous studies. A 4.5-mm coracoid tunnel is reportedly superior to a 6-mm coracoid tunnel for biomechanically rigid fixation after CC ligament reconstruction29, the Telos ligament has good mechanical properties (ultimate tensile strength, 1,866 N; stiffness, 68.3 N/mm) compared with natural ligament30 (ultimate tensile strength, 1,730 N; stiffness, 182 N/mm), and the pullout strength of a metallic button is >1,150 N31,32. Hence, our choices of implant and ligament were appropriate for rigid intraoperative fixation of the CC interspace and avoidance of implant migration into the clavicular and/or coracoid tunnel.
Second, the clavicular tunnel could have been located inside the anatomic insertion of the CC ligaments in the present study, considering that the mean CTR ranged from 0.16 to 0.18 in all groups (Table IV). In 1 anatomic study, the ratio of the distance from the lateral clavicular edge to the conoid center to clavicular length was 23.8% and the ratio of the distance from the lateral clavicular edge to the trapezoid center to clavicular length was 17.6%33; in another study, these ratios were 25.5% and 15.6%, respectively34. Those reports support the location of our clavicular tunnel placement inside the attachment of the CC ligaments as an anatomically proper position33,34, even allowing for anatomic variance of the CC ligaments35.
Third, the placement of the coracoid tunnel was located at the base of the coracoid in all shoulders, although not all shoulders had center-center coracoid tunnel orientation. The coracoid tunnel orientation did not significantly influence radiographic outcomes among the groups (Table IV). The entry point of the coracoid tunnel was located at the base of the coracoid in all shoulders, although only 11 shoulders (55%) had center-canter coracoid tunnel orientation. A previous cadaveric study demonstrated no significant difference between a base-centered and distal-centered 4.5-mm tunnel at the base of the coracoid with respect to the mean ultimate load and energy at ultimate load29. Additionally, Yi and Kim26 investigated the influence of specific radiographic parameters on radiographic results following the use of the single TightRope (Arthrex) technique and found no significant difference in the tunnel-to-medial coracoid ratio between dissociated and nondissociated groups. Our results are consistent with the results of those 2 studies26,29 because the location of the coracoid tunnel did not significantly differ between the 2 groups.
Fourth, the mean CTAP angle in Group 1 (1.9°) had a more perpendicular placement compared with that in Group 2 (12.1°). The CTAP angle in patients with dissociation is reportedly more acute than the angle in patients with nondissociation, indicating better clinical outcomes in the latter patients26. In the present study, only the CTAP angle significantly differed between Groups 1 and 2. The clinical results in Group 2 were significantly inferior to those in Group 1. Given these clinical and radiographic results, a lower CTAP angle seems to be desirable for a good outcome. Surgeons should intraoperatively monitor the direction of the coracoid and clavicular tunnels to produce a lower CTAP angle10,26. This monitoring is reportedly facilitated during arthroscopically assisted surgery with use of a transclavicular-transcoracoid drilling guide and fluoroscopy despite longer operation times and the risk of coracoid fracture36.
The present study had several limitations. First, it had a small sample size, especially in Group 2. The limited statistical power meant that the CTAP angle was not conclusively determined to be a significant predictive factor of an unfavorable outcome, despite the fact that the CTAP angle significantly differed between Groups 1 and 226. Nevertheless, we believe that the CTAP angle is an important operative factor affecting outcome. Previous studies have indicated that the interval between trauma and surgery and the age at the time of trauma significantly influence clinical and radiographic outcomes2,10; however, in the present study, these 2 factors did not significantly influence the outcomes in either group, possibly because of the small sample size. Second, the present study was retrospective and had no control group. Third, using clinical scores and classifying patients on the basis of the CCD ratio have not yet been validated for the assessment of AC joint dislocations. Indeed, considering the small sample sizes in the groups, the statistical results could not demonstrate the superiority of Group 1A over 1B. However, we consider that reduction of the AC joint by <25% of the CCD ratio is desirable for better long-term outcomes on the basis of the comparative results between Groups 1A and 1B and between Groups 1 and 2. Fourth, 2 of the 3 patients in Group 2 (Cases 18 and 20) had lower clinical scores because of pain than did the patients in Group 1, whereas 1 patient (Case 19) had maximum clinical scores. One possible explanation is that the latter patient (Case 19) achieved full range of motion and strength without pain because of comprehensive scapulothoracic functionality2,6,37.
In conclusion, the present study showed successful clinical and radiographic outcomes at a minimum of 10 years after anatomic CC ligament reconstruction for the treatment of acute AC joint dislocation. Longer-term successful outcomes may be achieved by ensuring the proper direction of drill-holes to create a lower CTAP angle and anatomically proper placement of the clavicular and coracoid tunnels intraoperatively.
A table showing baseline variables and clinical scores for 1 patient who declined radiographic examinations and 2 patients who were managed with the double-bundle technique as well as radiographs of Case 2 are available with the online version of this article as a data supplement at jbjs.org (http://links.lww.com/JBJSOA/A17).
The authors are grateful to Yoshihiko Tsuda (medical illustrator, Davinci Medical Illustration Office), to Hajime Yamakage, MD, for the statistical analyses, and to Mutsumi Nishida, PhD, Naoki Umatani, MD, Hideo Ito, MD, and Hiroshi Funakoshi, MD, for valuable discussion.
Investigation performed at Kyoto Shimogamo Hospital, Kyoto, Japan
Disclosure: The authors report no conflicts of interest. No outside funding was received for this study. The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJSOA/A16).
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