Endobutton combined with reinforced anchor effectively treated Tossy III acromioclavicular joint dislocation

Abstract

Objective:

This study aimed to evaluate the clinical efficacy of endobutton combined with a reinforced anchor in the treatment of Tossy III acromioclavicular joint (ACJ) dislocation.

Methods:

A total of 42 patients with Tossy Ⅲ ACJ dislocation treated between July 2017 and June 2023 were retrospectively analyzed. Operation time, intraoperative blood loss, length of hospital stay, and postoperative outcomes were assessed. Outcomes included Visual Analog Scale (VAS) scores for pain at 1 and 6 months, Constant–Murley scores for shoulder function, Karlsson scores for treatment efficacy, and postoperative complications.

Results:

The mean follow-up period was 23.43 ± 7.70 months. All patients achieved effective reduction and incision healing. The mean operation time was 64.29 ± 5.13 minutes, intraoperative blood loss was 46.79 ± 4.25 mL, and hospital stay was 4.95 ± 1.29 days. Postoperative VAS scores significantly decreased compared with preoperative values (P < .001), while Constant–Murley scores markedly improved at 1 and 6 months (P < .001). Karlsson scores showed 40 excellent and 2 good outcomes. Magnetic resonance imaging confirmed satisfactory healing at 1 and 6 months. Two patients demonstrated partial loss of ACJ reduction at 3 months, without clinical symptoms. No cases of complete radiological failure occurred.

Conclusion:

Endobutton combined with reinforced anchor demonstrated satisfactory early clinical efficacy in the treatment of Tossy Ⅲ ACJ dislocation, with improved pain relief, functional recovery, and a low complication rate.

Level of Evidence:

Level IV, Therapeutic Study.

Highlights

• This study investigated the efficacy of the endobutton combined with a reinforced anchor in the treatment of Tossy Ⅲ acromioclavicular joint dislocation.

• All patients achieved primary healing of the incision, and no complications.

• The postoperative 1-month and 6-month Visual Analog Scale scores for shoulder joint pain were significantly lower than those preoperatively.

• The postoperative 1-month and 6-month Constant–Murley scores for shoulder joint function were significantly higher than preoperative scores.

Introduction

The acromioclavicular (AC) joint (ACJ) is a joint consisting of the clavicle’s acromial end and the medial margin of the scapular acromial process. Acromioclavicular joint dislocation is a common shoulder injury with high incidence, which accounts for about 12% of shoulder injuries¹ and 9% of shoulder strap injuries.² There are many clinical classifications of ACJ dislocation; the Tossy classification is commonly used (Figure 1). For Tossy type III ACJ dislocation, complete rupture of the acromioclavicular ligaments and coracoclavicular ligaments may occur, and surgical treatment is suggested clinically.³

Figure 1.

Tossy classification of acromioclavicular joint dislocation. Type I: Radiographs show only a slight shift of the clavicular bone, suggesting laceration and partial rupture of the acromioclavicular ligament. Type II: Radiographs show half of the diameter of the outer end of the clavicle protruding beyond the acromion, indicating a rupture of the acromioclavicular ligament and a strain of the coracoclavicular ligament. Type III: Radiographs show complete displacement of the external end of the clavicle and a significant increase in the distance between the coracoid process and the clavicle, indicating complete rupture of the acromioclavicular and coracoclavicular ligaments.

To date, many surgical interventions have been applied to treat displaced AC dislocations. Examples include AC or coracoclavicular joint reconstruction with or without tendon transfer, AC fixation with screws and sutures, Weaver-Dunn surgery, arthroscopic-assisted surgery, and annular suspension fixation.^4-10 Following these intervention methods, postoperative complications such as shoulder pain, subacromial impingement, osteolysis, pin site infection, fixation failure, dynamic posterior translation, repeated instability after pin removal, restriction of shoulder joint abduction, and stress fracture were common after these fixations, and a second operation is required to remove the internal fixation.^4-10 This situation not only increases the medical cost but also brings the trauma of the second operation to the health of the patient, especially for patients with severe osteoporosis.^4-10 Another main problem of these ACJ patients is “radiological failure” or “radiological recurrence,” which presents as the following status: patients often have acromioclavicular osteoarthritis, partial or complete ACJ reduction. The ACJ appears to have a slight recurrent displacement under radiological examinations, though these conditions do not affect the functions of the ACJ among the patients.^7,11,12

In summary, there is a lack of consensus on whether surgical intervention is necessary for AC dislocation and which surgical treatment is the best choice for AC dislocation. In addition, the current problems of ACJ dislocation treatment were complications such as shoulder pain, fixation failure, repeated instability, and radiological failures that may not have affected the ACJ functions.

To fix these problems, a modified technique of the endobutton and a reinforced anchor was used in a series of patients. This modified technique involved reconstructing the trapezoid ligament, achieving a more accurate reconstruction of the coracoclavicular ligament in the clavicular coracoid process and distal footprint area. This study was to explore the early clinical efficacy in these patients who had experienced complete ACJ dislocation and were treated by the modified technique of endobutton and a reinforced anchor.

Material and methods

Case selection

The patients with ACJ dislocation who were treated from July 2017 to June 2023 were included. This study was approved by the Institutional Review Board of The Third Affiliated Hospital of Wenzhou Medical University (No. LZM2021052) on November 4, 2021, in accordance with the Declaration of Helsinki, and each patient provided a written informed consent for the treatment and the publication of the current study. Inclusion criteria: age ≥18 years old; time from dislocation to surgery ≤2 weeks; closed injury; complete ACJ dislocation of Tossy type III in accordance with relevant clinical diagnostic criteria; signed informed consent. Exclusion criteria: open injury; history of chronic shoulder pain; combined with other fractures or dislocations of the shoulder, such as scapular fractures, clavicle fractures, shoulder dislocations, etc.; combined with vascular and nerve injuries of the ipsilateral upper limb.

Surgical technique

Preoperative X-ray examination of the ACJ was performed. Figure 2 shows the manual treatment method. Under brachial plexus anesthesia, the patient was placed in a beach chair position, and an arc incision was made between the distal end of the clavicle and the coracoid process, about 7 cm long. The subcutaneous tissue and muscle were sequentially incised, and the deltoid muscle was bluntly dissected to expose the coracoid process and shoulder joint. The ruptured joint disc was cleaned, and the shoulder joint was reset. The acromion was temporarily fixed with Kirschner wires to make the site of the shoulder joint stable. The subclavian vascular and nerve bundle were fully protected in this way, so that the following surgery could be performed in a convenient way. A guidewire was inserted into the medial side of the distal end of the clavicle about 3 cm from the posterior superior to the anterior inferior direction through the clavicle and coracoid process. Then, a 4.5 mm hollow drill was used to enlarge the bone tunnel. The distance between the clavicle and coracoid process was measured, and a suitable length of a looped endobutton of 30 mm (Smith & Nephew) was selected. Two No. 2 non-absorbable Eibergen sutures were passed through the plate, and a self-made wire was used as a guide to pass through the coracoid foramen and place it at the base of the coracoid process. Then, a wire guide was used to guide the wire from the surface of the clavicle through the hole to bring the loop into place. Another looped button plate without a loop was placed inside it. Two No. 2 Eibergen sutures were passed through the 2 holes on the upper lateral edge of the button plate on the surface of the clavicle. The sutures were flipped to rest tightly against the clavicle and tied into a loop to complete the reconstruction of the conical ligament part of the coracoclavicular ligament. Then, a double-wire anchor of 2.7 mm (Smith & Nephew) was implanted at the base of the coracoid process. The double wire was passed through the gap between the coracoid and clavicle and brought out to the back of the clavicle as a reference for the attachment point of the trapezius muscle. About 1 cm from the distal end of the clavicle and 1/3 of the anterior part of the clavicle, a 2.0 mm drill was used to drill a hole, and one of the anchor sutures was passed through this hole and tied into a knot for fixation. The other anchor suture was wrapped around the distal end of the clavicle between the loop and the first anchor suture and tied into a knot for fixation. This completed the reconstruction of the trapezius ligament and repaired the AC ligament and joint capsule. The temporary Kirschner wires that fixed the acromion were removed, and the incisions were closed.

Figure 2.

The manual treatment method. The blue line indicates the arc incision.

Postoperative management

Routine prophylactic antibiotics were administered for 24 hours postoperatively. The patient wore a cervical harness for fixation for 4 weeks postoperatively. Muscle function exercises of the affected limb (hands, wrists) were started on the second day after surgery, depending on the patient’s pain tolerance. Passive exercises of flexion, extension, and abduction of the shoulder joint in a small range of motion started 1 week after surgery. Painless shoulder motion exercises of the shoulder joint were started 1 month after surgery and gradually transitioned to partial weight-bearing exercise and normal activities. Regular follow-up visits were conducted to guide rehabilitation exercises. Return visits started from the postoperative period at 1 month, 3 months, and 6 months. Then, a return visit or a telephone visit was done every 6 months for the following time.

Observation indicators

The operation time, intraoperative blood loss, hospital stay, and complications were observed. Observations were made during the operation, including the time taken, amount of blood loss, hospital stay, and complications. The Visual Analog Scale (VAS) was utilized to evaluate shoulder joint pain. The scores ranged from 0 to 10, with higher scores indicating more intense muscular pain. The Constant–Murley score¹³ was used to assess shoulder function. It consists of 15 points for pain, 20 points for daily activity, 40 points for active range of motion, and 25 points for strength. Lower scores indicated lower patient recovery levels. The shoulder joint pain was evaluated using the Karlsson scale,¹⁴ which classified the results as excellent, good, or poor, depending on the level of pain, muscle strength, and range of motion. Excellent: no shoulder pain, normal muscle strength, free movement, X-ray shows anatomical reset of the ACJ or a gap of <5 mm; Good: slight shoulder pain, moderate muscle strength, range of motion of the shoulder joint of 90°-180°, X-ray shows the ACJ gap of 5-10 mm; Poor: shoulder pain, poor muscle strength, shoulder joint movement of <90°, and the joint is still in a state of subluxation on X-ray.

Statistical methods

The data were processed using the SPSS 23.0 statistical software (IBM Inc., USA). Quantitative data are expressed as mean ± SD (x̅ ± s). The comparison of different time points before and after surgery was performed using ANOVA. A P-value less than .05 was considered statistically significant.

Results

Baseline data

In this study, a total of 50 patients received the endobutton combined with a reinforced anchor for the treatment of complete ACJ dislocation. Among the 50 patients, 1 patient had an open injury, 2 had a history of chronic shoulder pain, 4 had other shoulder fractures combined, and 1 had an upper limb nerve injury. After exclusion, a total of 42 patients were included in the final study.

This group of patients included 24 males and 18 females, aged 21-66 years old, with an average age of (43.60 ± 9.56) years old. The cause of injury was as follows: road traffic accidents accounted for 32 cases, while the other 10 cases were accidental falls. The injury to surgery time was 1-4 days, with an average of (2.29 ± 0.89) days. Preoperative routine shoulder X-ray examination was completed.

Treatment data

All patients were followed up for 12-36 months, with an average of (23.43 ± 7.70) months. All patients achieved effective reduction, primary healing of the incision, and no incision infection, vascular or nerve injury, or clavicle fractures occurred. The operation time was (64.29 ± 5.13) minutes, the intraoperative blood loss was (46.79 ± 4.25) ml, and the hospital stay was (4.95 ± 1.29) days (Table 1). The VAS pain scores at 1 month and 6 months postoperatively were (2.81 ± 0.63) and (0.67 ± 0.48) points, which were significantly lower than the preoperative score of (5.38 ± 0.82) points (P <.001, Table 2). The Constant–Murley shoulder function total scores at 1 month and 6 months postoperatively were (73.02 ± 1.76), (92.88 ± 1.70, Min: 90, Max: 95) points, which were significantly higher than the preoperative score of (34.00 ± 1.81) points (P <.001; Table 3). The scores in the parameters of pain, daily activities, range of motion, and muscle strength at 1 month and 6 months postoperatively were significantly higher than the preoperative scores (P <.001; Table 3). According to the Karlsson score, 40 cases were excellent and 2 cases were good.

Table 1.

Perioperative information of patients (n = 42)

Operation time (min)	Intraoperative blood loss (mL)	Hospital stay (days)	Karlsson score
			Excellent	Good
64.29 ± 5.13	46.79 ± 4.25	4.95 ± 1.29	40	2

Table 2.

Pre- and postoperative Visual Analog Scale scores

	Preoperative	Postoperative 1 month	Postoperative 6 months	F	P
VAS	5.38 ± 0.82	2.81 ± 0.63	0.67 ± 0.48	535.835	<.001

VAS, Visual Analog Scale.

Table 3.

Comparison of shoulder Constant–Murley score before and after operation (x® ± s)

Time	Constant–Murley Score
	Pain	Daily activities	Range of motion	Muscle strength	Total score
Preoperative	5.38 ± 0.82	6.50 ± 0.94	15.74 ± 1.52	6.38 ± 1.08	34.00 ± 1.81
Postoperative 1 month	9.64 ± 1.21	13.52 ± 0.89	33.07 ± 0.78	16.79±1.20	73.02 ± 1.76
Postoperative 6 months	13.69 ± 0.95	18.38 ± 1.25	36.50 ± 0.99	24.31 ± 1.09	92.88 ± 1.70
F	716.293	1387.146	4014.583	2684.824	12219.212
P*	<.001	<.001	<.001	<.001	<.001
P #	<.001	<.001	<.001	<.001	<.001

*Presents the P-values of the Constant–Murley Score at postoperative 1 month compared to that at preoperative period.

^#Presents the P-values of the Constant–Murley Score at postoperative 6 month compared to that at preoperative period.

All patients were able to return to their normal life and work at 12-month follow-up, including physical activities, without significant limitation in the range of motion of the shoulder joint. Only 1 patient reported an incision infection after surgery, and he recovered after taking anti-inflammatory and anti-infective drugs and was discharged from the hospital. Additionally, 2 patients experienced mild shoulder pain postoperatively which did not require special intervention. Figure 3D shows the preoperative and postoperative images of a 42-year-old male patient who presented with a right acromioclavicular joint dislocation (Tossy type III) resulting from a motor vehicle accident. Figure 3E and F show magnetic resonance imaging demonstrating good healing in the patients at 1 month and 6 months postoperatively, respectively.

Figure 3.

Magnetic resonance images of a 42-year-old male patient presented with a right acromioclavicular joint dislocation (Tossy type III) resulting from a motor vehicle accident. A: Preoperative anteroposterior X-ray of the right shoulder showed acromioclavicular joint dislocation. B and C: Magnetic resonance imaging of the right shoulder indicating tears of the acromioclavicular ligament and coracoclavicular ligament, respectively (highlighted by red arrows). D: On the second postoperative day, an anteroposterior X-ray of the right shoulder demonstrated good reduction of the acromioclavicular joint dislocation using the endobutton combined with reinforced anchor technology. The radiolucent hole at the distal end of the clavicle (marked with a red arrow) corresponds to the footprint area of the trapezoid ligament on the clavicle. E and F: Anteroposterior X-rays of the right shoulder taken at 1 month and 6 months postoperatively showed well-maintained reduction of the acromioclavicular joint.

During the 12-month follow-up, 2 patients were found to have partial acromioclavicular joint reduction lost at 3 months postoperatively under magnetic resonance (MR) examinations without any complaints of pain or functional problems. These 2 patients reported that everything in their daily life was normal before this MR examination and in the following follow-up. Figure 4A and B shows the radiological failure in 1 patient who was observed of partial acromioclavicular joint reduction loss. No complete radiological failure was observed in any patient.

Figure 4.

Magnetic resonance images of a patient presented with acromioclavicular joint dislocation (Tossy type III) that was observed of partial acromioclavicular joint reduction lost at 3 month postoperatively. A: The X-ray image immediately after the operation; B: Partial acromioclavicular joint reduction loss at 3 months postoperatively.

Discussion

In this study, all patients had significantly improved shoulder joint function Constant–Murley scores compared with preoperative levels, and shoulder joint function was basically restored to preoperative levels at 6 months postoperatively. The VAS scores also decreased over time. There was no occurrence of acromial impingement syndrome. Postoperative Karlsson scores were excellent. All patients were able to return to their normal lives and work. Only 1 patient had an incision infection postoperatively, and recovered after intervention, and 2 patients experienced mild shoulder pain postoperatively, which did not require special intervention. No complete radiological failure was observed in any patient. 2 patients were found to have partial acromioclavicular joint reduction lost at 3 months postoperatively under MR examinations without any complaints of pain or functional problems.

The ACJ is a micro-mobile semi-joint formed by the acromion and the distal end of the clavicle. It has 3 forms of movement: vertical, horizontal, and rotation along the long axis of the clavicle.¹⁵ Among them, the coracoclavicular ligament is an important structure that stabilizes the ACJ joint as a ligament that connects the clavicle to the coracoid process of the scapula. When the clavicle rotates, the coracoclavicular ligament lengthens. When the upper extremity is abducted, it has the function of accommodating the range of ACJ motion of 20°. Both vertical and horizontal stability should be assured to ensure better clinical recovery.¹⁶

As stated in the introduction section, the early surgical methods often led to complications such as fixation failure or recurrent operations.^8-10 There was no significant difference in biomechanical strength between single-row and double-row anchor fixation.¹⁷ The tightrope or clavicular hook plate is also effective in ACJ fixation and does not show great differences.¹⁸ The reconstruction of the coracoclavicular ligament using button plate technology for non-rigid fixation is more in line with the biological anatomy of the ACJ, allowing the reconstruction of the coracoclavicular ligament.^19-21 However, at present, there are still many cases of reduction loss in the treatment using the endobutton in clinical reports. Both domestic and foreign scholars have reported “bungee effect” and “windshield wiper effect.”²² These 2 terms²² mean that when the shoulder joint performs overhead movements, axial rotation of the clavicle produces a cutting action between the annular loop and bone tunnel. This situation leads to bone wear loss and instability of the button plate, resulting in reduction loss.²² In addition, for the endobutton technique, long-term persistent micro-motion of the ACJ will cause creep to occur in the annular loop, leading to a decrease in strength and a certain degree of reduction loss.^21,22

There is no uniform method to treat ACJ dislocation. Therefore, a new, improved technology was tried in this study. The author modified the endobutton technique by using a reinforced anchor to reconstruct the trapezoid ligament, which more accurately reconstructs the footprint area of the coracoclavicular ligament at the base of the coracoid process and distal end of the clavicle. This study showed the significant efficacy of the new endobutton technique. In this study, no complete radiological failure was observed in any patient, which is different from previous literature.^8-10,15-18 Two patients who were found to have partial loss of acromioclavicular joint reduction at 3 months postoperatively under MR examinations were observed without any complaints of pain or functional problems. These results supported the opinion of “radiological failure not influencing the ACJ function.”^7,11,12

In addition, in comparison with the relevant study reported,²³ blood loss was reduced, and hospitalization time was shorter compared to the hook plate in this study. However, there was a prolongation in operative time in the current study compared to the hook plate, which may be associated with the addition of a single reinforcing anchor nail.²⁴ The VAS scores were improved compared to the hook plate in the early stages at 1 month as well as at 6 months, as previously reported in the literature.^9,21,22 Similarly, Constant–Murley scores were also improved with higher scores than the hook plate at the follow-up duration.^9,24,25 These results showed the efficacy of the improved technique among these patients in this study.

There are still some problems with the treatment of ACJ dislocation using the endobutton combined with reinforced anchor technology in this study. For example, it requires good exposure of the coracoid process to reveal the footprint area of the coracoclavicular ligament, so that the anchor can be accurately implanted. This puts higher surgical technical requirements on the operator, increasing the operation time and hospitalization costs. This study was also limited by its small sample size from a single center. In addition, this study did not take a long follow-up, and the radiological follow-up was only reported at 6 months postoperatively. The conclusion of this study should be validated in the future via a multi-center, large-sample study with long follow-up of radiological data.

In summary, the treatment of acromioclavicular dislocation using the endobutton combined with reinforced anchor technology can better reconstruct the coracoclavicular ligament anatomically, with satisfactory short-term clinical results. But these results need to be validated via a multi-center, large-sample study with long follow-up of radiological data.

Funding Statement

This study was supported by Ruian City Science and Technology Bureau (No. MS2023018).

Data Availability Statement:

The data that support the findings of this study are available on request from the corresponding author.