Abstract
Background
A limitation of hook plate (HP) fixation for treating acromioclavicular (AC) joint dislocations is reduction loss after plate removal. While the healing of the coracoclavicular (CC) ligament is generally reliable after HP fixation, the healing status of the acromioclavicular ligament complex (ACLC) remains less understood. Our hypothesis was that ACLC healing failure would increase the risk of reduction loss.
Methods
Patients who underwent HP fixation within 2 weeks of injury and had preoperative and post-HP removal magnetic resonance imaging (MRI) from May 2018 to May 2023 for acute Rockwood type III or V AC joint dislocations were retrospectively reviewed. Reduction loss was defined as a coracoclavicular distance (CCD) ratio (CCD of the injured side / uninjured side × 100) greater than 150 at final follow-up. Ligament healing was assessed using the Ihara grade, with grades 1 and 2 considered healed. The tear sites of the ACLC were identified with bony attachment and mid-substance site.
Results
A total of 33 patients were included. CC ligaments healed in all cases. The mean follow-up period was 11.8 ± 4.1 months. The mean time to HP removal was 3.4 ± 0.8 months postoperatively. ACLC healing was observed in 21 patients, and non-healing in 12 patients. Reduction loss was significantly more frequent in the non-healing group (83.3%, 10 / 12) than in the healing group (23.8%, 5 / 21) (OR, 16.0; 95% CI, 2.59–98.77; p = 0.001). The ACLC healing failure rate was significantly higher in the bony attachment tear group (52.6%, 10 / 19) than in the mid-substance tear group (14.3%, 2 / 14) (OR, 6.67; 95% CI, 1.16–38.94; p = 0.024). Reduction loss was also significantly more frequent in bony attachment tears (63.2%, 12 / 19) than in mid-substance tears (21.4%, 3 / 14) (OR, 6.29; 95% CI, 1.29–30.54; p = 0.017).
Conclusions
Reduction loss after HP fixation for treating AC joint dislocations was associated with the healing status and tear sites of the ACLC. Particularly, bony attachment site tears demonstrated lower healing potential and a higher risk of reduction loss, suggesting that additional procedures beyond HP fixation should be considered when such tears are identified preoperatively on MRI.
Keywords: Acromioclavicular joint injuries, Shoulder dislocation, Bone plates, Magnetic resonance imaging
Acromioclavicular (AC) joint dislocations are common, accounting for 4%–20% of shoulder injuries, particularly in young patients.1,2,3) Hook plate (HP) fixation is a widely used technique for treating AC joint dislocations. While it provides rigid fixation and facilitates early recovery,4) it may be associated with complications, including postoperative coracoclavicular distance (CCD) widening.5,6)
The cause of postoperative CCD widening or reduction loss after treatment of AC joint dislocations remains poorly understood. The AC and coracoclavicular (CC) ligaments have been known to influence this phenomenon.7,8,9) HP fixation promotes the natural healing process of the AC and CC ligaments in AC joint dislocations.10) The CC ligament plays a primary role in vertical stability1) and is generally reported to have a high healing rate, with approximately 90% of cases healing successfully.10,11) Despite this typically high healing rate of the CC ligament, a high frequency of reduction loss occurs, leading us to hypothesize that the AC ligament may contribute to CCD widening.
The acromioclavicular ligament complex (ACLC) has also been reported to significantly affect AC joint stability,12) and a biomechanical study has indicated that the ACLC contributes partially to vertical stability.13) Although the healing of the ACLC is crucial for AC joint stability, there is a lack of studies evaluating the healing status of the ACLC after HP fixation. In addition, several studies have reported that ACLC tears in AC joint dislocations can occur at various sites, such as the clavicular, mid-substance, and acromial portions.14) A biomechanical study demonstrated that tears on the clavicular side are most likely to occur.10) However, no studies have reported on the healing rate or other aspects related to the injury site.
The purpose of this study was to evaluate the healing status of the ACLC after HP fixation for treating AC joint dislocations and its correlation with the reduction loss. We used post-HP removal magnetic resonance imaging (MRI) to assess the postoperative integrity of these ligaments and to determine their healing status. We hypothesized that failure of ACLC healing would increase the risk of postoperative reduction loss and that healing potential would differ depending on the tear site.
METHODS
All protocols were approved by the Institutional Review Board of Hallym University Kangnam Sacred Heart Hospital (IRB No. 2023-07-028), and the requirement for informed consent was waived due to the retrospective design of the study.
We retrospectively reviewed the medical records of patients diagnosed with AC joint dislocations at a single center between May 2018 and May 2023. The inclusion criteria were as follows: (1) acute AC joint dislocation (trauma < 2 weeks, Rockwood III or V); (2) treatment with HP fixation; and (3) records of pre- and post-HP removal MRI; (4) patients identified as having CC ligament healing on post-HP removal MRI. We excluded patients with (1) a history of previous shoulder surgery; (2) concomitant fracture of the clavicle, scapula, or humerus; (3) inadequate radiologic data to assess the parameters; and (4) unhealed CC ligament on post-HP removal MRI.
Radiologic Parameters and MRI Protocol
The images were obtained using the institutional Picture Archiving and Communication System (Infinitt PACS M6, INFINITT Healthcare). Radiographs taken before and after HP surgery were reviewed for radiological assessment. Additionally, all patients underwent MRI twice: once before HP fixation and once after HP plate removal (approximately 3 months after HP fixation). The postoperative MRI was performed 1 day after plate removal, using a 3.0T scanner (Skyra, Siemens).
Radiographs included bilateral clavicular anteroposterior and 30° caudal tilting views. The CCD was measured using the method described by Minkus et al.3) and Stein et al.4) in the bilateral clavicular anteroposterior view (Fig. 1). The CCD refers to the space between the lower cortex of the clavicle and the uppermost point of the coracoid process, measured parallel to the ground. To evaluate CCD widening after HP removal, we calculated the CCD ratio. The CCD ratio was defined as the CCD of the injured side divided by the CCD of the uninjured side, multiplied by 100. In this study, CCD widening was categorized into 2 groups: greater than 150 and less than 150. Reduction loss was defined as a CCD ratio greater than 150.5) We measured the CCD ratio at 3 time points: preoperative (before surgery), post-HP fixation (post-reduction), and final follow-up (approximately 1 year after the initial surgery with HP removal).
Fig. 1. Representative bilateral clavicular anteroposterior radiographs used for coracoclavicular distance (CCD) measurement. (A) CCD was measured on both injured and uninjured sides using the vertical distance between the superior border of the coracoid process and the inferior border of the clavicle after hook plate fixation. (B) Follow-up radiograph after plate removal showing CCD measurement for postoperative evaluation.
MRI measurements were performed according to the following protocol. The injury of the ACLC was evaluated on the T2-weighted image.15) The method used to measure the healing status of the ACLC was based on the healing grade described by Ihara et al.16) which assesses healing of the anterior cruciate ligament. The MRI presentations of the healed ACLC were classified into 4 grades based on uniformity, straightness, and size. Grade 1 represents a clearly defined, normal-sized, straight band with homogenous low signal intensity; grade 2, a clearly defined straight band with low signal intensity interspersed with areas of high signal intensity; grade 3, a thin band with a low signal intensity containing areas of high signal intensity; and grade 4, a band with an indiscernible dark signal. This study considered grades 1 and 2 to correspond to successful healing (Fig. 2).
Fig. 2. Post-hook plate removal T2-weighted magnetic resonance images. The healing grade of the acromioclavicular ligament by Ihara. (A) The white arrow shows the integrity of the healed acromioclavicular ligament complex. (B) The white arrow depicts a non-healed acromioclavicular ligament complex.
The injuries of the ACLC were divided according to the site.14,17) The sites of injuries were categorized as mid-substance or at a bony attachment, including both clavicular and acromial sides, on the coronal proton-density weighted image (Fig. 3). The tears of ACLC represent ligament disruption with high signal intensity, which is consistent with fluid or hemorrhage. A musculoskeletal radiologist (IY) and a shoulder fellowship-trained surgeon (YTC) measured radiologic parameters to assess reliability. These parameters were evaluated at 2-week intervals to assess both intra- and interobserver reliability. The reliability of the CCD was assessed using the intraclass correlation coefficient, while the reliability of injury site and healing status was assessed using Cohen’s kappa coefficient.
Fig. 3. Preoperative coronal proton-density weighted magnetic resonance images of a ruptured acromioclavicular ligament complex. (A) A clavicular-sided injury is depicted by the absence of any attached tissue at the clavicular tear site (white arrow), with high signal intensity. (B) A mid-substance-sided injury represents soft tissues attached to the bony attachment site (white arrow and arrowhead), with a space of high signal intensity in the mid-substance. (C) An acromial-side injury is depicted, with the white arrow indicating acromial-sided detachment.
Operative Technique and Rehabilitation
All operations were performed by a single surgeon (JK). The patients were placed under general anesthesia and positioned in a beach chair. A sagittal 6–8-cm incision was made. The lateral clavicle and AC joint were identified and cleared of interposed remnant tissue. AC joint reduction was anatomically performed, and a titanium LCP Clavicle Hook plate (Synthes) was applied. The deltotrapezial fascia over the clavicle, including the AC joint capsule, was repaired using a 1-0 absorbable braided suture (Vicryl, Ethicon).
As part of our routine clinical protocol, HP removal was scheduled at approximately 3 months (12 weeks) postoperatively. This decision was not based on radiologic or clinical assessment of healing, as there is currently no established method to reliably confirm ligament healing at the AC joint. Instead, the timing followed common practice reported in previous literature.4,18) However, the exact removal date varied slightly depending on patient-related factors. Patients were prescribed a sling for 6 weeks and were allowed to engage in daily activities such as eating and movement below the shoulder level for up to 6 weeks following the surgical intervention. Beyond the initial 6-week postoperative period, the patients were granted unrestricted mobility.
Statistical Analysis
Statistical analysis was performed using SPSS 27 software (IBM Corp.). The p-value for statistical significance was set at p < 0.05. The Shapiro-Wilk test was used to assess the standard normal distribution. Fisher’s exact test was used to analyze categorical data. The independent t-test was used to compare continuous variables. A post-hoc power analysis was performed using G*Power software (version 3.1.9.7; Heinrich-Heine-Universität Düsseldorf) to determine statistical power based on the observed effect size derived from the difference in final CCD ratio between groups. In this study, 21 patients were included in the ACLC healing group and 12 in the non-healing group. The calculated statistical power was 0.93 (effect size, 1.15; alpha, 0.05).
The intra- and interobserver reliability were determined using the intraclass correlation coefficient for continuous variables and Cohen’s kappa coefficient for categorical variables. ICCs of 0.81–1.0, 0.61–0.80, 0.41–0.60, 0.21–0.40, and ≤ 0.20 were defined as excellent, high, moderate, fair, or poor agreement, respectively. Cohen’s kappa coefficients23 of 0.801–1.000, 0.601–0.800, 0.401–0.600, 0.201–0.400, and 0.000–0.200 were defined as almost perfect, substantial, moderate, fair, slight, and poor agreement, respectively.
RESULTS
Patient Demographics
We retrospectively reviewed the records of 46 patients with AC joint dislocation treated with HP fixation. We excluded 4 patients with unhealed CC ligaments and 9 who did not undergo post-HP removal MRI. Finally, 33 patients were included in the final cohort. The average age of the study participants was 45.3 ± 13.7 years (range, 21–66 years), with 29 men (87.9%) and 4 women (12.1%). The average period from HP fixation surgery to removal was 3.4 ± 0.8 months (range, 3–6 months). The average follow-up duration was 11.8 ± 4.1 months (range, 9–31 months). The injury mechanisms included falls in 12 cases (36.4%), traffic collisions in 10 cases (30.3%), and sports injuries in 11 cases (33.3%). In the analysis of ACLC healing, 21 cases (63.4%) showed healing, while 12 cases (36.4%) showed non-healing. Tear sites occurred in 16 cases (48.5%) at the clavicular side, 14 cases (42.4%) at the mid-substance, and 3 cases (9.1%) at the acromial side. Reduction loss occurred in 15 cases (45.5%), while 18 cases (54.5%) maintained reduction at final follow-up. The demographic data are summarized in Table 1.
Table 1. Patient Characteristics.
| Characteristics | Value (n = 33) | |
|---|---|---|
| Age (yr) | 45.3 ± 13.7 (21–66) | |
| Follow-up period (mo) | 11.8 ± 4.1 (9–31) | |
| Time to removal (mo) | 3.4 ± 0.8 (3–6) | |
| Sex (male : female) | ||
| Male | 29 (87.9) | |
| Female | 4 (12.1) | |
| Side (dominant : non-dominant) | ||
| Dominant | 19 (57.6) | |
| Non-dominant | 14 (42.4) | |
| Rockwood classification | ||
| III | 10 (30.3) | |
| V | 23 (69.7) | |
| Injury mechanism | ||
| Fall | 12 (36.4) | |
| Traffic collision | 10 (30.3) | |
| Sports injury | 11 (33.3) | |
| Smoking | ||
| Smoker | 9 (27.3) | |
| Non-smoker | 24 (72.7) | |
| Deltotrapezial fascia injury (present : absent) | ||
| Injured | 25 (75.8) | |
| Uninjured | 8 (24.2) | |
Values are presented as mean ± standard deviation (range) or number (%).
Reliability of Radiologic Measurements
Interobserver reliability for injury site and healing status demonstrated substantial agreement, with kappa statistics of 0.816 (95% CI, 0.618–1.014; p < 0.001) for injury site and 0.836 (95% CI, 0.618–1.054; p < 0.001) for healing status. Intra-observer reliability for injury site and healing status showed almost perfect agreement, with kappa statistics of 0.852 (95% CI, 0.686–1.018; p < 0.001) for injury site and 0.848 (95% CI, 0.646–1.050; p <0.001) for healing status. Interobserver reliability for CCD ratio was excellent, with an ICC of 0.936 (95% CI, 0.851–0.970; p < 0.001). Intraobserver reliability for CCD was also excellent, with an ICC of 0.968 (95% CI, 0.934–0.984; p < 0.001). Given the high level of inter- and intraobserver agreement, the radiological parameters used for statistical analysis were based on the assessments made by the shoulder fellowship-trained surgeon without the need for additional consensus adjustment.
Comparison of Demographics and Radiological Findings Regarding ACLC Healing Status
Patient characteristics based on ACLC healing are summarized in Table 2. No statistically significant differences were observed in demographic variables between the healing and non-healing groups. The ACLC healing failure rate was significantly higher in the bony attachment tear group (52.6%, 10 / 19) than in the mid-substance tear group (14.3%, 2 / 14) (OR, 6.67; 95% CI, 1.16–38.94; p = 0.02). The CCD ratio at the final follow-up was significantly lower in the healing group (124.2 ± 31.5; 95% CI, 110.71–137.65) than in the non-healing group (161.7 ± 33.5; 95% CI, 142.71–180.67) (p = 0.003). Reduction loss was significantly more frequent in the non-healing group (83.3%, 10 / 12) than in the healing group (23.8%, 5 / 21) (OR, 16.0; 95% CI, 2.59–98.77; p = 0.001).
Table 2. Demographic and Radiological Comparisons Regarding Healing Status of the Acromioclavicular Ligament Complex (n = 33).
| Variable | ACLC healing (n = 21) | ACLC non-healing (n = 12) | p-value | |
|---|---|---|---|---|
| Age (yr) | 44.2 ± 14.4 | 47.3 ± 12.8 | 0.546 | |
| Follow-up period (mo) | 10.8 ± 1.7 | 13.7 ± 6.2 | 0.135 | |
| Sex (male : female) | 19 : 2 | 10 : 2 | 0.610 | |
| Side (dominant : non-dominant) | 14 : 7 | 5 : 7 | 0.162 | |
| Time to removal (mo) | 3.4 ± 0.9 | 3.3 ± 0.6 | 0.557 | |
| Rockwood classification (III : V) | 7 : 14 | 3 : 9 | 0.616 | |
| Injury mechanism | 0.176 | |||
| Fall | 9 | 3 | ||
| Traffic collision | 4 | 6 | ||
| Sports injury | 8 | 3 | ||
| Smoking (smoker : non-smoker) | 7 : 14 | 2 : 10 | 0.301 | |
| Deltotrapezial fascia injury (present : absent) | 15 : 6 | 10 : 2 | 0.443 | |
| Tear site (bony attachment : mid-substance) | 0.024* | |||
| Bony attachment | 9 | 10 | ||
| Mid-substance | 12 | 2 | ||
| CCD ratio | ||||
| Preoperative | 223.3 ± 82.0 | 236.2 ± 94.9 | 0.684 | |
| Post-reduction | 99.7 ± 27.6 | 107.5 ± 45.2 | 0.541 | |
| Final follow-up | 124.2 ± 31.5 | 161.7 ± 33.5 | 0.003* | |
| Reduction loss | < 0.001* | |||
| Reduction maintenance | 16 | 2 | ||
| Reduction loss | 5 | 10 | ||
Values are presented as mean ± standard deviation or number.
AC: acromioclavicular, ACLC: acromioclavicular ligament complex, CCD: coracoclavicular distance.
*Indicates statistical significance at p < 0.05.
Comparison of Demographics and Radiological Findings Regarding Reduction Loss
The analysis of patient characteristics and radiological parameters based on reduction state at the final follow-up is presented in Table 3. No statistically significant differences were observed in demographic variables between the 2 groups. Reduction loss was significantly more frequent in the bony attachment tear group (63.2%, 12 / 19) than in the mid-substance tear group (21.4%, 3 / 14) (OR, 6.29; 95% CI, 1.29–30.54; p = 0.017). The preoperative CCD ratio was significantly greater in the reduction loss group (261.1 ± 90.8; 95% CI, 215.17–307.07) than in the maintenance group (200.4 ± 72.5; 95% CI, 166.88–233.88) (p = 0.041) (Table 3).
Table 3. Demographic and Radiological Comparisons between Patients with and without Reduction Loss after Hook Plate Fixation for AC Joint Dislocation (n = 33).
| Variable | Reduction maintenance (n = 18) | Reduction loss (n = 15) | p-value | |
|---|---|---|---|---|
| Age (yr) | 42.4 ± 12.6 | 48.8 ± 14.6 | 0.185 | |
| Follow-up period (mo) | 10.9 ± 1.7 | 12.9 ± 5.7 | 0.226 | |
| Sex (male : female) | 17 : 1 | 12 : 3 | 0.308 | |
| Side (dominant : non-dominant) | 10 : 8 | 9 : 6 | 0.797 | |
| Time to removal (mo) | 3.5 ± 1.0 | 3.2 ± 0.6 | 0.304 | |
| Rockwood Classification (III : V) | 8 : 10 | 2 : 13 | 0.070 | |
| Injury mechanism | 0.525 | |||
| Fall | 7 | 5 | ||
| Traffic collision | 4 | 6 | ||
| Sports injury | 7 | 4 | ||
| Smoking (smoker : non-smoker) | 5 : 13 | 4 : 11 | 0.627 | |
| Deltotrapezial fascia injury (present : absent) | 12 : 6 | 13 : 2 | 0.242 | |
| ACLC healing status | < 0.001* | |||
| Healing | 16 | 5 | ||
| Non-healing | 2 | 10 | ||
| CCD ratio | ||||
| Preoperative | 200.4 ± 72.5 | 261.1 ± 90.8 | 0.041* | |
| Post-reduction | 99.4 ± 28.1 | 106.3 ± 41.7 | 0.575 | |
| Final follow-up | 111.0 ± 20.0 | 170.0 ± 23.5 | < 0.001* | |
| Tear site | 0.017* | |||
| Bony attachment | 7 | 12 | ||
| Mid-substance | 11 | 3 | ||
Values are presented as mean ± standard deviation or number.
ACLC: acromioclavicular ligament complex, CCD: coracoclavicular distance.
*Indicates statistical significance at p < 0.05.
DISCUSSION
The most important finding of this study is that reduction loss is associated with ACLC healing status, and the healing rate of ACLC differs depending on the ligament tear site when treating AC joint dislocation with HP fixation. The present study used postoperative MRI immediately after HP removal to investigate the specific etiology of reduction loss. Our findings confirmed that the healing state of the ACLC contributes to the maintenance of AC joint reduction after HP removal. According to Fukuda et al.1) and Mazzocca et al.2), the AC ligament primarily influences horizontal stability, a point supported by several studies.19,20,21) Several studies explained reduction loss after HP fixation. One study suggested that advanced age and female sex are risk factors for reduction loss, as these factors affect ligament healing.9) Another study reported that the occurrence of reduction loss is influenced by whether AC ligament reinforcement was performed in conjunction with CC ligament reconstruction.7,8) Additionally, a biomechanical study by Kurata et al.13) reported that the AC ligament plays an important role in maintaining AC joint stability in the superior direction, and displacement of more than 50% of the AC joint can occur with isolated AC ligamentous injury. These findings align with our study. In this study, we observed a relationship between the healing status of the ACLC and reduction loss, suggesting that the ACLC might contribute to vertical stability to some extent.
This study revealed that the ligament healing rate varied depending on the ACLC tear site in cases of HP fixation for AC joint dislocations. White et al.14) observed that the incidence of AC joint dislocations differed depending on the AC ligament injury site in hockey players. Maier et al.17) classified the ACLC injury patterns in AC joint dislocations into clavicular, oblique, midportion, and acromial categories, and revealed that clavicular injuries were associated with a larger articular disc size. According to studies by Nakazawa et al.22) and Emura et al.,23) the superoposterior bundle of the AC ligament, which primarily influences stability, is attached to the superolateral side (the acromial side). They also demonstrated that the articular disc was mainly attached to the acromial side, arguing that the clavicular side had biomechanical weakness. This study showed that clavicular injury of the ACLC occurred more frequently compared to injuries at other sites. The present study demonstrates that bony attachment site injuries have poor healing rates. It can be expected that a larger articular disc size, which is more frequently vulnerable to clavicular injury,17) could lead to an insufficient reduction of the AC joint when performing HP fixation, resulting in lower stability and decreased ligament healing. Although no significant difference was found in post-reduction CCD ratios between the tear location groups, this does not necessarily imply equivalent anatomical restoration or healing potential. Intraoperatively, bony attachment site tears were often accompanied by substantial soft tissue disruption, including injury to the articular disc, which limited effective repair. The HP provided temporary mechanical stability, but the underlying biological environment may have been suboptimal for ACLC healing at these sites. A few studies demonstrated that injuries proximal to the insertion sites of the medial collateral ligament of the knee exhibited a slower healing rate than those located at the midsubstance of the ligament.24,25) These studies attributed this phenomenon to the amount of scar tissue found at the injury location, explaining that, near the ligament’s insertion point into the bone, the constrained environment allows for relatively less scar formation, particularly at the bone interface. This finding is consistent with the results of this study. Therefore, our study partially explains the lower healing rate at the ligament insertion site.
In the study by Lee et al.9), the preoperative CCD ratio in the reduction loss group was significantly greater than in the maintenance group, and the proportion of patients with Rockwood type V in the reduction loss group was significantly higher compared to those with Rockwood type III. A biomechanical study postulated that soft tissues around the AC joint, such as the AC joint capsule and deltotrapezial fascia, may contribute to the stability of the AC joint.26) Our study revealed that the preoperative CCD ratio was related to reduction loss. However, we found no significant association between Rockwood classification, deltotrapezial fascia injury, and reduction loss. This may be due to the statistical limitations of Rockwood classification, a lack of investigation into other soft tissue injuries, and the limited sample size. Additionally, we confirmed that the preoperative CCD ratio, reflecting the degree of AC joint displacement immediately after injury, did not significantly influence ACLC ligament healing or the injury site, but it did affect reduction loss. Further randomized controlled trials with larger sample sizes are needed to investigate this phenomenon.
The frequency of reduction loss after HP removal in the present study was higher than in previous reports.4,5,6,27) This discrepancy may be attributed to differences in study design and patient demographics. For example, Chang et al.27) reported an 8% rate of AC joint subluxation in their HP group, with a nearly equal distribution of Rockwood type III and V injuries and a mean preoperative CCD ratio of 202.4% ± 54.5%. Additionally, their mean implant removal time was 6 months. In contrast, approximately 70% of patients in our study were classified as Rockwood type V, with a higher mean preoperative CCD ratio of 232.9% ± 85.6%, and HP removal was performed after an average of 3.4 months, indicating a more severe patient population with shorter fixation periods. Eschler et al.5) did not report baseline injury characteristics, limiting direct comparison. Furthermore, definitions of reduction loss vary across studies5,27) — some define it as a CCD increase of 100% or more compared to the uninjured side. In our study, only 1 case showed a postoperative CCD ratio > 200% at final follow-up. A prospective study comparing HP fixation and double-button suspension also reported a postoperative CCD ratio of 141.81 ± 31.20, which is comparable to our results.4)
In this study, bony attachment site injury of the ACLC suggested that HP fixation alone may not adequately promote ligament healing, potentially leading to a higher likelihood of reduction loss after HP removal. Sheu et al.,28) comparing HPs alone, HPs with suture anchors, and CC suspensory fixation in patients with AC joint dislocation, showed that the group with HPs with anchor fixation showed potential for biological AC joint reduction. Additionally, this group maintained sound reduction without CCD widening even at the 2-year follow-up, explaining fewer complications such as osteolysis and acromial fracture due to overcorrection. Izadpanah et al.29) proposed reconstruction of the AC ligament based on the pathoanatomical injury pattern. Based on our study findings, additional procedures besides HP fixation may benefit clavicular injuries. Using a clavicle-sided transosseous suture,29) an HP with CC fixation,28) or a suture tape cerclage 30) for reinforcement could also be options.
This study had several limitations, including its retrospective design and small sample size. We conducted evaluations using postoperative MRI immediately after HP removal, focusing on short-term outcomes. However, the relatively short follow-up period limited our ability to assess long-term results. Additionally, MRI was performed 1 day after plate removal, which may have affected signal intensity due to fluid accumulation or inflammation. Although the Ihara grading system considers ligament uniformity, size, and morphology in addition to signal intensity, the timing of imaging could have introduced potential bias in the assessment of ACLC healing. While we identified factors that may influence reduction loss, further research is needed to explore the correlations between these factors. Moreover, the number of acromial side tears observed in this study was limited (n = 3, 9.1%), precluding a separate subgroup analysis for this specific tear location. Although the bony attachment site group included both clavicular and acromial side tears, this grouping may not fully reflect anatomical or biomechanical differences. Further studies with larger cohorts are needed to validate these differences and clarify their clinical significance. The reason for the variation in tear sites could not be determined in this study. However, previous studies and clinical observations suggest that acromial-sided tears may be associated with high-energy trauma. Further research is warranted to validate this relationship and its clinical implications. Finally, functional outcomes were not evaluated due to the nature of this trauma-focused study, in which patients were not routinely followed after plate removal unless complications occurred. Nevertheless, our study is the first to analyze ligament healing using postoperative MRI after HP removal, and it is also the first to partially explain the causes of reduction loss commonly observed after HP removal based on the healing status of the ACLC.
Reduction loss was related to the healing status and tear sites of the ACLC. A greater preoperative CCD widening contributed to an increased risk of reduction loss. When bony attachment site injury of the AC joint is present, HP fixation alone may not lead to favorable AC joint maintenance, and additional procedures for reinforcement should be considered.
ACKNOWLEDGEMENTS
This study was supported by the Hallym University Medical Center Research Fund, Mighty Hallym 4.0 (MH 4.0-202205460001).
Footnotes
CONFLICT OF INTEREST: No potential conflict of interest relevant to this article was reported.
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