Analysis of the curative effect of arthroscopic coracoid process drill-free U-shaped suspension fixation in the treatment of acute acromioclavicular joint dislocation

DOI: https://doi.org/10.21203/rs.3.rs-1839739/v1

Abstract

Background: Currently, there is still have some controversies in surgical treatment modality for acute acromioclavicular joint dislocation. The objective of this study is to investigate the clinical effect of arthroscopic coracoid process drill-free U-shaped suspension fixation in the treatment of acute acromioclavicular joint dislocation, compared with coracoid process drilling TightRope fixation technique.

Patients and methods: Twenty-five patients with acute acromioclavicular joint dislocation admitted to our hospital were reviewed from May 2015 to June 2021. The patients were divided into drill-free group (the use of coracoid process drill-free U-shaped suspension fixation technique under arthroscopy, 12 cases) and drilling group (the use of coracoid process drilling TightRope fixation technique under arthroscopy, 13 cases). The (UCLA) score, (VAS) score, Constant score and shortest distance between the coracoid process and clavicle (CCD) were evaluated before and after surgery. 

Results: The patients were followed up with a mean time of 41.3 (rang,12-84) months. At the final follow-up, the postoperative (UCLA) score, Constant score and (VAS) score of both groups were significantly improved compared with those before surgery, and the difference was significant (P<0.05). In terms of imaging evaluation, the (CCD) and the side-to-side (CCD) difference of both groups were significantly reduced immediately after surgery and at the final follow-up, and the difference were significant (P<0.05). There was no significant difference between the groups. Unfortunately, reduction loss occurred in 4 patients (drill-free group: 33%, drilling group: 31%) in both groups, but it had no significant effect on patients' pain perception and life and work, 2 patients (15%) in the drilling group developed coracoid fractures in the postoperative 6-week follow-up and received surgery, no cases of coracoid fractures were observed in the drill-free group.

Conclusion: The use of arthroscopic coracoid process drill-free U-shaped suspension fixation in the treatment of patients with acute acromioclavicular joint dislocation can obtain the same good clinical effects as the arthroscopic coracoid process drilling TightRope technique, and can reduce the complications of coracoid fractures.

Level of evidence: Level IV, therapeutic case series.

1. Introduction

Acromioclavicular joint dislocation is a relatively common shoulder injury seen in young people who engage in sports and people who have suffered high-energy trauma [1], and it accounts for approximately 9%-12% of shoulder injuries [2, 3], The degree of injury ranges from mild to severe. According to the Rockwood classification system, the injury is divided into type I to type VI [4]. Currently, type I and type II can be treated nonsurgically, type IV to VI require surgery. However, the optimal treatment of type III injuries remains controversial., and there is no clear consensus exists [5].

There is also no gold standard for the choice of surgical treatment modality. The choice of clavicle hook plate and Kirschner wire fixation can fully reduce the acromioclavicular joint and firmly fix it, which is beneficial to early functional exercise after shoulder surgery, but there are disadvantages, such as acromion impingement, acromioclavicular arthritis, high recurrence rate, and the need for a second surgery to remove it. In a study by Jensen et al [6] comparing the use of hook plate (HP) and TightRope (TR) techniques in 56 patients, 63% of the patients in the HP group developed hypertrophic scarring of the shoulder and 28% of the patients developed clavicle arthritis, 13% of patients required revision surgery for shoulder stiffness, 46% of patients in the TR group had mild pain and paresthesia in the clavicle button area, 19% had acromioclavicular arthritis, and 12% required revision surgery. The choice of clavicle hook plate or Kirschner wire fixation technique may have more complications than TightRope technique. Andreani et al [7] compared the results of the TightRope technique with the hook plate fixation technique and found that the patients in the TightRope group had a higher Constant value and did not need a second surgery to remove the hardware. In a comparative study of hook plate and TightRope technique conducted by Liu et al [8], it was found that both techniques can achieve satisfactory 1-year curative effects, but TightRope technique is more favorable for early postoperative function restored of 1 month and 3 months. These evidences suggest that the TightRope-like technique appears to be a superior choice, but its potential complication-coracoid fracture has also been reported in the literature. Bindra et al [9] used the TightRope technique to acute a patient with a type III injury, found coracoid fracture and loss of reduction at week 8 after surgery.

Most of the anatomical reconstruction techniques of the coracoclavicular ligament reported in the literature require the establishment of a coracoid tunnel, and there are complications such as coracoid iatrogenic fractures and fixation failure. In a case series by Milewski et al [10], 2 coracoid fractures occurred in 10 patients who underwent coracoid ligament reconstruction using a coracoid tunnel. Such patients often require revision surgery, and revision surgery also faces great challenges, increasing the hospitalization costs of patients and exacerbating the contradiction between doctors and patients.

This paper retrospectively analyzes the clinical treatment of patients with acute acromioclavicular joint dislocation using the arthroscopic coracoid process drilling TightRope fixation technique in the early stage from May 2015 to June 2021 and the arthroscopic coracoid process drill-free U-shaped suspension fixation technique in the later stage, there is no literature comparing these two techniques. We hypothesized that arthroscopic coracoid process drill-free U-shaped suspension fixation could achieve the same good clinical effect as the arthroscopic coracoid process drilling TightRope fixation technique, and could reduce the complications of coracoid fractures.

2. Patients And Methods

2.1 Patient selection criteria

From May 2015 to June 2021, a total of 25 adult patients with acute acromioclavicular joint dislocation were treated in our hospital. Before June 2018, a total of 13 patients were treated with the arthroscopic coracoid process drilling TightRope fixation technique. A total of 12 patients were treated with the arthroscopic coracoid process drill-free U-shaped suspension fixation technique. Inclusion criteria: (1) injury time ≤ 3 weeks; (2) Rockwood classification of type III to VI; (3) no chronic shoulder injury (such as rotator cuff tear, shoulder joint instability, anterior and posterior upper labrum lesions, shoulder joint adhesion, acromioclavicular arthritis, etc.) and adjacent tumor diseases; and (4) no previous surgery on the shoulder or inferior vascular injury. Informed consent was obtained from all patients before inclusion in the study, and all patients were surgically treated by a senior surgeon.

2.2 General Information

Drilling group: 8 males and 5 females; aged 22–55 years, with an average age of 32.0 years. Rockwood classification: 5 cases were type III, 6 cases were type IV, and 2 cases were type V. The time from injury to surgery was 4–10 days, with an average of 6.0 days. Body mass index is 18–27㎏/㎡, with an average of 22.5㎏/㎡. Drill-free group: 8 males and 4 females; aged 19–52 years, with an average age of 30.5 years. Rockwood classification: 4 cases were type III, 7 cases were type IV, and 1 case was type V. The time from injury to surgery was 3–10 days, with an average of 6.5 days. Body mass index is 20–28㎏/㎡, with an average of 23.1㎏/㎡. There was no significant difference in general data such as gender, age, injury type, time from injury to surgery or body mass index between the patients of groups (P > 0.05) (Table 1).

Table 1

Patient general information

Group

Drilling Group

(n = 13)

Drill-free Group (n = 12)

P Value

F Value

Male/female

8/5

8/4

1.000

-

Age

32.0 ± 8.4(22–55)

30.5 ± 8.9(19–52)

.648

0.214

Time to surgery

6.0 ± 1.7(4–10)

6.5 ± 2.2(3–10)

.272

1.266

Body mass index

22.5 ± 2.8(18–27)

23.1 ± 2.6(20–28)

.736

0.117

Rockwood classification

1.000

-

5

6

2

4

7

1


2.3 Surgical methods

The arthroscopic coracoid process drill-free U-shaped suspension fixation technique was adopted for the drill-free group: all patients were under general anesthesia in the beach chair position, the conventional posterior approach was used to examine whether there was any combined injury in the joint, and an anterior approach was established. The anterior space of the rotator cuff and the inferior surface of the coracoid process were exposed; the arthroscope was placed under the acromion through the conventional posterior approach, an anterolateral approach was established, and the upper surface of the rotator cuff was explored and cleaned; then, the arthroscope was placed from the anterolateral approach to fully expose the coracoid process, syndesmotic tendon, and coracoacromial ligament, entering from the surface of the coracoacromial ligament to explore the acromioclavicular joint and coracoclavicular ligament. Special attention was given to protecting the stump of the ligament. An anterior-medial approach was established, the medial side of the coracoid process was processed, part of the insertion point of the pectoralis minor muscle was stripped from the medial side of the coracoid process, the right-angle forceps thread guide was passed from the medial side of the coracoid process through the lower surface and out from the lateral side, and an absorbable thread was introduced for use. The epidural needle was used to assist in positioning the clavicular tunnel. The medial tunnel was located at the anatomical point of the conoid ligament, and the lateral tunnel was located at the anatomical point of the trapezoid ligament. Two small incisions of 1 cm were made on the upper surface of the clavicle to reach the bone surface. Two 4 mm bone tunnels were established under guidance, and the two ends of the absorbable wire around the coracoid were pulled out from the tunnels. One end of the adjustable TightRope fixation set was tied to one end of the absorbable wire and pulled into the bone tunnel, while the other end of the absorbable wire was tightened and pulled out from the other bone tunnel. When the loop plate reached the surface of the clavicle, the adjustable wire of the fixation set was tightened until the acromioclavicular joint was completely reduced, and the reduction process can be completely monitored under the microscope (Fig. 1).

In the drilling group, traditional arthroscopic guides were used to assist in the establishment of the clavicle and coracoid tunnels. The diameter of the tunnels was 4.5 mm, and a TightRope fixation device was placed to tighten and fix them. For details, please refer to our earlier proposed arthroscopic coracoid drilling TightRope fixation technique (Fig. 2) [11].

2.4 Post-operative exercise

The affected limb was immobilized with a forearm sling within 6 weeks after surgery; passive shoulder joint functional rehabilitation treatment was performed within 1 week after surgery, and active shoulder movement was performed after 6 weeks. Strength training was available 3 months later. Overhead and contact sports were usually performed 1 year after surgery, after mobility and strength were restored. The annual activity and strength were recovered under the guidance of a professional rehabilitation specialist.

2.5 Clinical evaluation

Each patient underwent preoperative assessment and postoperative follow-up assessment using the University of California Los Angeles (UCLA) Shoulder Rating Scale score, Constant score, and Visual Analog Scale (VAS) pain score.

2.6 Imaging assessment

Each patient underwent X-ray processing before surgery, immediately after surgery, and at the final follow-up after surgery, including frontal radiographs of the left and right shoulder joints, and the shortest distance between the coracoid process and the clavicle (CCD) was measured and defined as the shortest distance between the uppermost edge of the upper cortex of the coracoid process and the lowermost edge of the distal lower cortex of the clavicle (Fig. 3). This was used to assess the superior and inferior displacements of the clavicle. Loss of reduction was defined as a 25% or greater increase in (CCD) compared with the contralateral side; failure was defined as concurrent acromioclavicular dislocation at final follow-up[12].

2.7 Statistical methods

Statistical software (SPSS 22.0) was used to analyze the data, and the data were expressed as mean ± standard deviation. Normality test was performed, and skewed data was tested by Mann-Whitney U test. The comparison of gender and injury type between groups was performed by Fisher's exact test, and the data of normal distribution was by independent samples t test; the comparison of normal distribution of subjective scores before and after surgery within the group was performed by paired t test, and the data of (CCD) values and left and right differences in different periods of surgery were compared. Repeated measures ANOVA was used; test level α = 0.05.

3. Results

The patients of both groups were followed up with a mean time of 41.3 (rang,12–84) months, according to the time pattern of 6 weeks, 3 months, 6 months, 12 months, and 12 months after surgery, no patients were lost to follow-up. At the final follow-up, the postoperative (UCLA) score, Constant score and (VAS) score of the both groups were significantly improved compared with those before surgery, and the difference was statistically significant (P < 0.05) (Table 2). In terms of imaging evaluation, the (CCD) in the drilling group decreased from 21.6 ± 2.0mm before surgery to 8.8 ± 0.9mm immediately after surgery, and the final follow-up was 10.9 ± 1.0mm; the side-to-side (CCD) difference decreased from 11.8 ± 1.6mm before surgery to 1.2 ± 0.5mm immediately after surgery, and the final follow-up was 3.3 ± 0.9mm. In the drill-free group, the (CCD) decreased from 22.1 ± 1.5mm before surgery to 9.0 ± 0.6mm immediately after surgery, and the final follow-up was 10.6 ± 0.7mm; the side-to-side (CCD) difference decreased from 12.5 ± 1.0mm before surgery to 1.2 ± 0.4mm immediately after surgery, and the final follow-up was 2.8 ± 0.8mm. Immediately after surgery and at the final follow-up, the (CCD) of the both groups were significantly reduced compared with those before surgery, and the difference was statistically significant (P < 0.05), the side-to-Side (CCD) difference were significantly reduced compared with those before surgery, and the difference was statistically significant (P < 0.05) (Table 3). There was no significant difference between the two groups. Unfortunately, reduction loss occurred in 4 patients (drill-free group: 33%, drilling group: 31%) in both groups, but it had no significant effect on patients' pain perception and life and work, 2 patients (15%) in the drilling group developed coracoid fractures in the postoperative 6-week follow-up (Table 3) (Fig. 4), and received surgery. No cases of coracoid fractures were observed in the drill-free group (Fig. 5).

Table 2

Comparison of UCLA, Constant, and VAS scores between the both groups before surgery and at the final follow-up

Group

Drilling Group(n = 13)

Drill-free Group(n = 12)

Outcome Scores

Before Surgery

Final

Follow-up

P

Value

Before Surgery

Final

Follow-up

P

Value

UCLA Score

8.8 ± 2.6

32.3 ± 1.5

.000

9.0 ± 3.3

32.5 ± 1.9

.000

Constant Score

20.6 ± 4.0

89.3 ± 5.6

.000

21.3 ± 3.9

89.3 ± 5.5

.000

VAS Score

7.8 ± 1.2

0.7 ± 0.6

.000

7.7 ± 1.1

0.7 ± 0.5

.000


Table 3

Comparison of radiological results between the both groups of patients before surgery, immediately after surgery and at the final follow-up

Group

Before Surgery

Immediately After Surgery

Final Follow-up

P Value

Complication

Drilling Group (n = 13)

CCD, mm,

21.6 ± 2.0

8.8 ± 0.9

10.9 ± 1.0

.000

2(coracoid fracture)

4(reduction loss)

Side-to-Side Difference

11.8 ± 1.6

1.2 ± 0.5

3.3 ± 0.9

.000

Drill-free Group

(n = 12)

CCD, mm,

22.1 ± 1.5

9.0 ± 0.6

10.6 ± 0.7

.000

4(reduction loss)

Side-to-Side Difference

12.5 ± 1.0

1.2 ± 0.4

2.8 ± 0.8

.000

4. Discussion

The most important finding of this study is that the use of arthroscopic coracoid process drill-free U-suspension fixation technique in the treatment of patients with acute acromioclavicular joint dislocation obtained the same good clinical evaluation and radiological assessment as the coracoid process drilling TightRope fixation technique.

The biggest advantage of the technique we have adopted is the coracoid process drill-free U-shaped suspension fixation, which theoretically reduces the complications of coracoid fractures. An anatomical study by Mazzocca et al [13] found that the mean width and height of the coracoid process were 24.9 mm and 11.9 mm, respectively, and the mean length was 45.2 mm. This evidence suggests that the coracoid process is a short, flat, narrow bony structure with limited maneuvering space for surgeons, making tunneling difficult. Once the tunnel is established, there may be no opportunity to adjust the tunnel position. At the same time, the coracoid tunnel will face a higher risk of fracture, and the double tunnel will face a higher risk. A biomechanical study showed that a 4 mm tunnel was created in the coracoid process with an average width of 25.1 mm, and the coracoid process was at a higher risk of fracture [14]. For those with short stature and a small coracoid process, the risk of fracture will increase. In addition, Ferreira et al [15] showed that when the coracoid tunnel was established, the upper entrance and lower exit of the tunnel in the center-center or middle-center direction could reduce the fracture risk, and the risk of coracoid fracture in the other tunnel directions was the higher. This requires the surgeon to have a high level of expertise. For most surgeons, it is difficult to establish a standard direction tunnel, and the coracoid process will face a higher risk of fracture. At present, for the anatomy of the coracoid in Chinese patients, although some studies based on fresh specimens, dried specimens and CT three-dimensional reconstructions have given more detailed anatomical parameters [1618], used to guide intraoperative positioning and reduce fracture risk, the risk of coracoid fracture objectively exists. Once the coracoid process is fractured in the early stage, the reconstruction of the coracoclavicular ligament fails, the acromioclavicular joint will be dislocated again, and its revision will face great challenges. Milewski et al [10] conducted a study on coracoid single-tunnel reconstruction of the coracoid ligament. The coracoid process was fractured 10 weeks after the surgery, and the reduction of the acromioclavicular joint was lost 8 weeks after the resurgery. In our study, 2 cases of coracoid fractures occurred in the drilling group, and surgery was performed; meanwhile, a coracoid tunnel was not established in the drill-free group, and coracoid fractures were avoided to a greater extent.

Lu et al [19] used the LARS artificial ligament for coracoid process drill-free suspension to reconstruct the coracoclavicular ligament in a study of 24 patients with acute acromioclavicular joint dislocation. At a mean follow-up of 36 months, 20 anatomical reductions occurred, 4 patients lost the reduction slightly, and no coracoid fracture occurred. In a study of coracoclavicular ligament reconstruction in 17 patients conducted by Banffy et al [20], an artificial material was used to form a ring in the coracoid process for suspension, and satisfactory results were obtained at the 2-year follow-up, with no coracoid fracturs. In a series of 48 cases of coracoclavicular ligament reconstruction conducted conducted by Li et al [21], used coracoid process drill-free suspension fixation, only 8.3% of patients had partial (CCD) loss, and no pain, instability, or coracoid fracture-related complications were reported. These evidences suggest that coracoclavicular ligament reconstruction with drill-free suspension fixation of the coracoid process can not only achieve good clinical effects but also avoid coracoid fractures, our results are basically consistent with those reported in the literature.

The technique we use also provides effective support for the coracoclavicular ligament to maintain its anatomical position, preserves the ligament footprint and stump of the conoid and trapezoid ligaments, and creates conditions for promoting ligament healing. The double-tunnel anatomical reconstruction is superior to the single-tunnel nonanatomical reconstruction mentioned in the literature in terms of strength, anti-rotation, and anatomy. Furthermore, it can avoid the failure of fixation and the erosion of wire knots that appear in the literature due to the widening of the tunnel due to excessive stress, clavicle fracture caused by clavicle, loss of reduction caused by square knot loosening, and other related complications [12, 20].

However, admittedly, this study has some limitations. First, this was a retrospective study. Second, the sample size is small, which may lead to certain statistical biases in the conclusion. Third, the follow-up time was relatively short, especially those patients of the drill-free group, and some complications were difficult to detect during short-term follow-up.

5. Conclusion

The use of arthroscopic coracoid process drill-free U-shaped suspension fixation in the treatment of patients with acute acromioclavicular joint dislocation can obtain the same good clinical effects as the arthroscopic coracoid process drilling TightRope technique, and can reduce the complications of coracoid fractures.

Abbreviations

CCD:The shortest distance between the uppermost edge of the upper cortex of the coracoid process and the lowermost edge of the distal lower cortex of the clavicle. UCLA:The University of California Los Angeles. VAS: Visual Analog Scale.

Declarations

Acknowledgements

We thank Ling Shen of the Statistics Department of Kunming Medical University for him help with completing statistical analysis.

Availability of data and materials

Data associated with this study is retained at a central repository at the Orthopaedic Department, the Second Affiliated Hospital of Kunming Medical University. If there are any questions, please contact the corresponding author.

Ethics approval and consent to participate

This study follows the principles of the Declaration of Helsnki and was approved by the Institutional Review Board of Kunming Medical University. All subjects provided their informed consent to participate in this study.

Consent for publication

Written informed consent for publication was obtained from the guardian.

Disclosure of interest

The authors declare that they have no competing interest.

Funding

This work was supported by grants from the National Natural Science Foundation of China (No. 81960412)and the Yunnan province basic research program (No.202001AT070007).

Authors’ contributions

YSL and YHY participated in the acquisition of the data. YSL contributed to data analysis. DHZ and YSL revised the manuscript carefully for important content. DHZ conceived, designed, and led the study. YSL and YHY made contributions to drafting the manuscript. All authors read and approved the final manuscript.

References

  1. Tamaoki MJ, Belloti JC, Lenza M. Surgical versus conservative interventions for treating acromioclavicular dislocation of the shoulder in adults.Cochrane Database Syst Rev.2010VN8:CD007429.
  2. Lemos MJ. The evaluation and treatment of the injured acromioclvicular joint in athletes. Am J Sports Med.1998;26(1):137–144.
  3. Mazzocca AD, Arciero RA, Bicos J. Evaluation and treatment of acromioclavicular joint injuries. Am J Sports Med.2007;35(2):316–29.
  4. Gorbaty JD, Hsu JE, Gee AO. Classifications in Brief: Rockwood Classification of Acromioclavicular Joint Separations. CLIN ORTHOP RELAT R. 2017-01-01;475(1):283–287.
  5. Virk MS, Apostolakos J, Cote MP, Baker B, Beitzel K, Mazzocca AD. Operative and Nonoperative Treatment of Acromioclavicular Dislocation:A Critical Analysis Review.JBJS Rev.2015V3N10.
  6. Jensen G, Katthagen JG, Alvarado LE, Lill H. Has the arthroscopically assisted reduction of acute AC joint separations with the double tight-rope technique advantages over the clavicular hook plate fixation?KNEE SURG SPORT TR A. 2014-02-01;22(2):422–30.
  7. Andreani L, Bonicoli E, Parchi P, Piolanti N, Michele L. Acromio-clavicular repair using two different techniques.EUR J ORTHOP SURG TR. 2014-02-01;24(2):237–42.
  8. Liu S, Li C, Song Z, Bai X, Wu H. Comparison of open reduction and fixation with hook plate and modified closed reduction and fixation with tightrope loop plate for treatment of rockwood type III acromioclavicular joint dislocation.BMC Musculoskelet Disord. 2022-03-29;23(1):301.
  9. Bindra J, VanDenBogaerde J, Hunter JC. Coracoid fracture with recurrent AC joint separation after Tightrope repair of AC joint dislocation.Radiol Case Rep. 2015-11-06;6(4):624.
  10. Milewski MD, Tompkins M, Giugale JM. Complications related to anatomic reconstruction of the coracoclavicular ligaments.AM J SPORT MED. 2012-07-01;40(7):1628–34.
  11. Wang Chaoran, Zhang Jun, Zhao Daohong,etc. Arthroscopic Twin Tail TightRope combined with distal joint capsule repair technique for acute acromioclavicular joint dislocation. Chinese Journal of Rehabilitation an Reconstruction Surgery, 2019, 33(08): 970–975.
  12. Choi NH, Lim SM, Lee SY, Lim TK. Loss of reduction and complications of coracoclavicular ligament reconstruction with autogenous tendon graft in acute acromioclavicular dislocations.J Shoulder Elbow Surg.2017;26(4):692–698.
  13. Rios CG, Arciero RA, Mazzocca AD. Anatomy of the clavicle and coracoid process for reconstruction of the coracoclavicular ligaments.Am J Sports Med.2007V35N5:811–7.
  14. Martetschläger F, Saier T, Weigert A. Effect of Coracoid drilling for Acromioclavicular Joint Reconstruction Techniques on Coracoid Fracture Risk:A Biomechanical Study.Arthroscopy.2016V32N6:982–7.
  15. Ferreira JV, Chowaniec D, Obopilwe E, Nowak MD.Biomechanical evaluation of effect of coracoid tunnel placement on load to failure of fixation during repair of acromioclavicular joint dislocations.Arthroscopy.2012V28N9:1230–6.
  16. Zhang Lei, Tang Xiaogao, Jin Yufeng, Zhang Huaqiang,et al. Anatomical morphometric measurement and clinical significance of the coracoclavicular ligament based on fresh specimens. Acta Anatomy. 2021,52(06).
  17. Zhang Lei, Chen Hengshu, Qi Ji, Zeng Yan,et al. Anatomical morphological measurement of the coracoid process and its clinical significance.Chinese Journal of Clinical Anatomy. 2018,36(06).
  18. Zeng Shengqiang, Ma Li, Zhang Lei, Wang Guoyou,et al. Morphologial measurement and clinical significance of coracoid process in Chinese based on CT three-dimensional reconstruction.Acta Anatomy.2019,50(02).
  19. Nan Lu, Lei Zhu, Tianwen Ye, Aimin Chen. Evaluation of the coracoclavicular reconstruction using LARS artifificial ligament in acute acromioclavicular joint dislocation. Knee Surg Sports Traumatol Arthrosc.2014V22N9:2223–7.
  20. Banffy MB, van Eck CF, ElAttrache NS. Clinical outcomes of a single-tunnel technique for coracoclavicular and acromioclavicular ligament reconstruction. Shoulder Elbow Surg.2018V27N6S:S70-S75.
  21. Li F, Li Y, Lu Y, Zhu Y. Clinical Outcome of a Modified Coracoid Tunnel-Free Coracoclavicular Sling Technique With Remnant Preservation for the Treatment of High-Grade Acromioclavicular Joint Separation:A Report of 48 Cases With 2 to 5 Years of Follow-up.Am J Sports Med.2021V49N6:1612–1618.