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Clavicle hook plate fixation for distal-third clavicle fracture (Neer type II): comparison of clinical and radiologic outcomes between Neer types IIA and IIB
ARTICLE IN PRESS J Shoulder Elbow Surg (2016) ■■, ■■–■■
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ORIGINAL ARTICLE
Clavicle hook plate fixation for distal-third clavicle fracture (Neer type II): comparison of clinical and radiologic outcomes between Neer types IIA and IIB Wonyong Lee, MD, Chong-Hyuk Choi, MD, PhD, Yun-Rak Choi, MD, PhD, Kyung-Han Lim, MD, Yong-Min Chun, MD, PhD* The Department of Orthopaedic Surgery, Arthroscopy and Joint Research Institute, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea Background: The purpose of this study was to investigate clinical and radiologic outcomes of clavicle hook plate fixation for distal-third clavicle fracture (Neer type II) and to compare the clinical and radiologic outcomes and complications between Neer type IIA and type IIB. Methods: We retrospectively reviewed 35 patients who underwent open reduction and internal fixation with AO hook locking compression plate (LCP) for distal clavicle fracture, including 13 patients with Neer type IIA and 22 patients with type IIB. Visual analog scale pain score, shoulder scores (subjective shoulder value, University of California–Los Angeles shoulder score, American Shoulder and Elbow Surgeons score), and active range of motion were evaluated to determine clinical outcome. Coracoclavicular distance was measured, and that of the injured side at last follow-up was compared with that of the uninjured side to evaluate radiologic outcomes. Results: AO hook LCP fixation for distal-third clavicle fracture (Neer type II) produced satisfactory radiologic outcomes, including high union rates (100%) and coracoclavicular distance maintenance, as well as satisfactory clinical outcomes, including visual analog scale score for pain, shoulder scores (subjective shoulder value, University of California–Los Angeles shoulder score, American Shoulder and Elbow Surgeons score), and active range of motion. There were no significant differences between Neer type IIA and type IIB. With regard to complications, 22.9% of patients experienced shoulder stiffness and 17.1% had subacromial erosion; however, there were no significant differences between the 2 groups. Conclusion: The AO hook LCP is a suitable choice for Neer type IIA and type IIB distal-third clavicle fracture fixation. Level of evidence: Level III; Retrospective Cohort Design; Treatment Study © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. Keywords: Distal clavicle fracture; Neer type; unstable; hook plate; plate fixation; coracoclavicular distance
The Institutional Review Board of Severance Hospital approved this study: No. 4-2016-0486. The requirement for informed consent was waived. *Reprint requests: Yong-Min Chun, MD, PhD, The Department of Orthopaedic Surgery, Arthroscopy and Joint Research Institute, Severance Hospital, Yonsei University College of Medicine, CPO Box 8044, 50-1 Yonsei-ro, Seodaemun-gu, Seoul 120-752, Republic of Korea. E-mail addresses: [email protected], [email protected] (Y.-M. Chun). 1058-2746/$ - see front matter © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. http://dx.doi.org/10.1016/j.jse.2016.11.046
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Figure 1
Neer classification of distal clavicle fractures. (A) Neer type IIA. (B) Neer type IIB.
Distal-third clavicle fractures account for approximately 10% to 15% of all clavicle fractures16 and are subdivided into Neer types IIA and IIB, depending on the attachment status of the conoid ligament to the clavicle (Fig. 1). Neer type II distal clavicle fractures are unstable because bidirectional forces function at the fracture site, namely, the unhindered downward pull of the shoulder girdle on the distal fragment and the unimpeded superior pull by the trapezius muscle on the medial fragment.4 As a result, reported rates of delayed union or nonunion are high with conservative, nonsurgical treatment.3,14,18,24 Therefore, surgery is recommended for Neer type II distal clavicle fractures. Various surgical techniques have been introduced, such as K-wire fixation,8 tension band wiring,2 locking plate,19,25 and hook plate.9,17,23 However, there is no consensus as to the “gold standard” of fixation for Neer type II distal clavicle fracture. The AO hook locking compression plate (LCP; Synthes, Solothurn, Switzerland), a fixation technique originally used for acromioclavicular ligament injury, has shown especially good clinical and radiologic outcomes in acute injury by restoring normal coracoclavicular distance (CCD), even without repair or augmentation of the coracoclavicular ligament. Several studies have reported that this hook plate also showed good outcomes when used for Neer type II distal clavicle fracture fixation.5,9,13,23 However, there have been no studies comparing the clinical and radiologic outcomes between Neer type IIA and type IIB fractures treated with the AO hook LCP. The purpose of this study was to investigate the clinical and radiologic outcomes of using AO hook LCP fixation for unstable distal-third clavicle fracture and to compare the outcomes and complications between Neer type IIA and type IIB fractures. We hypothesized that clinical outcomes would not differ between patients with type IIA (group A) and type IIB (group B) fractures but that group B would exhibit higher nonunion rates and increased CCDs than patients in group A.
Materials and methods Study population This is a retrospective study of patients seen from March 2009 to May 2014 for Neer type II distal clavicle fracture fixation using the
AO hook LCP. During this period, 43 patients underwent open reduction and internal fixation with the AO hook LCP for Neer type II distal clavicle fracture. The inclusion criteria were acute fracture within 2 weeks of injury and availability for follow-up at 2 years after surgery. Exclusion criteria were previous surgical history on the affected shoulder and concomitant fracture around the affected shoulder. We retrospectively reviewed the medical records, including radiologic imaging, of 35 patients (13 in group A and 22 in group B) who met these criteria.
Functional and radiologic assessment For functional assessments, we used a visual analog scale (VAS) pain score, the subjective shoulder value (SSV), the American Shoulder and Elbow Surgeons (ASES) score, the University of California– Los Angeles (UCLA) shoulder score, and active range of motion (ROM). ROM was defined as forward flexion in the scapular plane and external rotation with the elbow at the side. Internal rotation was determined by measuring the highest spinal segment the patient could reach with the thumb pointed upward. To facilitate statistical analyses, the spinal segment level was converted to continuous numbers: T1 to T12 levels were represented by 1 through 12; L1 to L5 level were represented by 13 through 17; and the sacrum was represented by 18.10,11,15 An independent examiner blinded to patient data evaluated all values at each postoperative follow-up. For radiologic evaluation, both clavicle anteroposterior views were taken regularly after surgery (at 2 weeks, 6 weeks, 12 weeks, 6 months, and 1 year and annually thereafter). Bone union was defined as bridging callus across the fracture site or invisible fracture line. The CCD, defined as the perpendicular distance from the top of the coracoid process to the lower border of the clavicle, was measured by 2 independent examiners. The individual value was measured, and then the individual mean value was calculated. We compared the CCD of the injured side with that of the uninjured side to evaluate reduction status and to confirm control of superior migration of the proximal fragment by AO hook LCP.
Surgical procedures All patients underwent open reduction and internal fixation in the 20° beach chair position under general anesthesia by a single surgeon. A 9- to 10-cm incision was made on the distal clavicle and acromion. The facture fragments were identified after dissection, and a hook plate was placed under the acromion and on the fracture site extending medially. We checked the status of reduction, depth of
ARTICLE IN PRESS Hook plate for distal clavicle fracture Table I
3
Patient demographics
Sex, male/female Age (years) Side of injury, right/left Time to surgery (days) Proportion of comminuted fracture Time for implant removal (months)
Total (N = 35)
Neer type IIA (n = 13)
Neer type IIB (n = 22)
P value
24/11 40.7 ± 12.3 (22-62) 20/15 4.4 ± 2.4 (1-10) 45.7% (n = 16) 4.4 ± 1.2 (3-8)
9/4 41.8 ± 10.6 (22-54) 8/5 4.1 ± 1.7 (2-8) 30.8% (n = 4) 4.2 ± 1.2 (3-8)
15/7 40.0 ± 13.5 (22-62) 12/10 4.5 ± 2.8 (1-10) 54.5% (n = 12) 4.5 ± 1.3 (3-8)
.105 .124 .737 .775 .293 .511
the hook, and contour of the plate on the distal clavicle under fluoroscopic guidance. Adjustments of the plate contour with appropriate hook depth were made until optimal reduction and contour of the plate were achieved. Then, locking screw fixation of both medial and lateral fragments was performed. Even though an additional coracoclavicular ligament repair was not performed, the deltotrapezius fascial repair for reinforcement was done securely over the plate.
Table II
Injury mechanism
Fall down Bicycle accident Sports injury Traffic accident
Total (N = 35)
Neer type IIA (n = 13)
Neer type IIB (n = 22)
19 10 5 1
7 5 1 0
12 5 4 1
Postoperative rehabilitation and implant removal Regardless of Neer type, the affected arm was kept in a sling for 6 weeks after surgery. Pendulum exercise, self-assisted circumduction exercise, and gradual passive ROM began on the first day after surgery, as tolerable. At 6 weeks postoperatively, active ROM exercise began. After 3 months, the implant was removed if bone union was obtained; if not, implant removal was delayed until union was observed. If the patient experienced shoulder stiffness at the time of implant removal, brisement under general anesthesia and subsequent arthroscopic capsular release were performed concomitantly.
Statistical analysis Statistical analyses were performed using the SPSS software program (version 21.0; IBM, Armonk, NY, USA). The Mann-Whitney test was used to compare numerical data, such as VAS pain scores, ASES scores, UCLA shoulder scores, and the mean increase in CCD, between the 2 groups. A Wilcoxon signed rank test was used to compare preoperative and postoperative CCD values within each group. Fisher exact test was used to compare categorical data. Statistical significance was set at P < .05.
Results Patient demographics We identified a total of 35 patients, including 24 men and 11 women. The mean age of the patients at the time of operation was 40.7 ± 12.3 years overall (range, 22-62 years). The right arm was affected in 20 patients and the left arm was affected in 15 patients, with 8 right arms and 5 left arms in group A and 12 right arms and 10 left arms in group B. The mean time to surgery was 4.4 ± 2.4 days (range, 1-10 days). A total of 45.7% of patients had comminuted fractures, including 30.8% in group A and 54.5% in group B. All patients underwent plate removal surgery, and the mean time to removal of the hook plate was 4.4 ± 1.2 months (range, 3-8 months). There were no significant differences in patient demograph-
ic data (Table I). With regard to injury mechanism, 19 patients fell down, 10 patients experienced bicycle trauma, 1 patient was involved in a traffic accident, and 5 patients were injured during winter sports—3 during snowboarding and 2 during skiing (Table II).
Functional outcomes and radiologic outcomes At the 2-year follow-up, the mean VAS pain score was 1.4 ± 0.9 (range, 0-3). The mean SSV was 84.4 ± 9.1 (range, 60-100). The mean UCLA score was 32.6 ± 2.2 (range, 2635). The mean ASES score was 83.5 ± 7.9 (range, 66.7100). There were no significant differences in VAS pain scores and shoulder scores (SSV, UCLA, and ASES) between group A and group B. The mean active forward flexion was 157° ± 4° (range, 150°-165°). The mean active external rotation was 49° ± 3° (range, 44°-54°). The mean active internal rotation was 10 ± 1 (range, 9-12). There were no significant differences in active ROM between the 2 groups (Table III). Bone union was obtained in all patients. The mean preoperative CCD was 19.9 ± 3.6 mm (range, 13.2-28.8 mm), and the mean postoperative CCD at last follow-up was 11.3 ± 1.0 mm (range, 9.5-13.0 mm). Although there was a significant difference in preoperative CCD values between the 2 groups, there was no significant difference in mean postoperative CCD at last follow-up. The mean increase in CCD at final follow-up was 7.6% ± 2.2% (range, 3.1%-13.9%) compared with a preoperative measurement from the uninjured side; there was no significant difference between the 2 groups (Table IV).
Postoperative complications Postoperative stiffness occurred in 22.9% of all patients (n = 8), including 15.4% of group A (n = 2) and 27.3%
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W. Lee et al. Table III
Functional and clinical outcomes at last follow-up according to Neer type IIA and type IIB
VAS score SSV UCLA score ASES score Forward flexion External rotation Internal rotation
Total
Neer type IIA
Neer type IIB
P value
1.4 ± 0.9 (0-3) 84.4 ± 9.1 (60-100) 32.6 ± 2.2 (26-35) 83.5 ± 7.9 (66.7-100) 157° ± 4° (150°-165°) 49° ± 3° (44°-54°) 10 ± 1 (9-12)
1.5 ± 1.0 (0-3) 80.9 ± 11.2 (60-100) 33.2 ± 1.2 (31-35) 83.5 ± 6.4 (68.3-93.3) 158° ± 4° (152°-165°) 50° ± 3° (44°-54°) 10 ± 1 (9-12)
1.4 ± 0.8 (0-3) 86.6 ± 7.0 (70-100) 32.3 ± 2.6 (26-35) 83.6 ± 8.9 (66.7-100) 156° ± 4° (150°-162°) 48° ± 2° (44°-52°) 11 ± 1 (9-12)
.601 .130 .261 .906 .159 .130 .243
VAS, visual analog scale; SSV, subjective shoulder value; UCLA, University of California–Los Angeles; ASES, American Shoulder and Elbow Surgeons.
Table IV
Change in CCD according to Neer classification type IIA and type IIB
Preoperative uninjured side (mm) Preoperative injured side (mm) Last follow-up injured side (mm) Mean increase in CCD (%)
Total
Neer type IIA
Neer type IIB
P value
10.5 ± 1.0 (8.7-12.5) 19.9 ± 3.6 (13.2-28.8) 11.3 ± 1.0 (9.5-13.0) 7.6 ± 2.2 (3.1-13.9)
10.9 ± 0.9 (9.7-12.5) 17.7 ± 3.5 (13.2-20.9) 11.6 ± 0.9 (10.1-13.0) 6.9 ± 2.3 (3.1-11.6)
10.3 ± 1.0 (8.7-12.1) 21.4 ± 3.6 (14.5-28.8) 11.1 ± 1.0 (9.5-12.9) 8.1 ± 2.1 (4.9-13.9)
.070 .001 .131 .134
CCD, coracoclavicular distance.
Table V
Complications
Nonunion Delayed union Stiffness Subacromial erosion
Total (N = 35)
Neer type IIA (n = 13)
Neer type IIB (n = 22)
0 2.9% (n = 1) 22.9% (n = 8) 17.1% (n = 6)
0 0% (n = 0) 15.4% (n = 2) 30.8% (n = 4)
0 4.5% (1) 27.3% (n = 6) 9.1% (n = 2)
of group B (n = 6), although all patients were taught how to perform pendulum exercise and self-assisted circumduction exercise on the first day after surgery. For patients experiencing stiffness, we performed concomitant arthroscopic capsular release during the hardware removal operation. We educated and encouraged patients to perform passive ROM exercises including pendulum exercise on the first day after surgery to prevent shoulder stiffness. Despite these efforts, some patients were not compliant and experienced stiffness. We attempted physiotherapy for these patients; however, there was still no improvement. Therefore, we conducted brisement and arthroscopic capsular release under general anesthesia during the hardware removal operation. After arthroscopic capsular release, all patients recovered full ROM. In addition, 17.1% of patients (n = 6) had subacromial erosion, including 30.8% in group A (n = 4) and 9.1% in group B (n = 2) (Table V). Subacromial erosion was diagnosed on plain radiograph, and those patients had no specific symptom. After implant removal, there were no patients who complained of acromioclavicular joint pain. Except for shoulder stiffness and subacromial erosion, we did not find other postoperative complications, such as acromial fracture and infection.
Discussion The purpose of this study was to evaluate the clinical outcomes of displaced distal-third clavicle fractures treated with open reduction and internal fixation by a clavicle hook plate and to compare the outcomes according to Neer subtype classification (Neer type IIA and type IIB). Contrary to our initial hypothesis, there were no significant differences in nonunion rate or CCD change between patients with Neer type IIA and type IIB injuries. On the other hand, our results show satisfactory clinical and radiologic outcomes in both groups with no significant differences between the 2 groups. Shin et al19 reported satisfactory clinical outcomes and high union rates using anatomic clavicle LCP fixation in patients with unstable distal clavicle fractures, even when the lateral fragment was small. They tried to insert more than 4 small screws in the distal fragment to achieve secure fixation. Even though the aim of open reduction and internal fixation is to obtain absolute stability, it is challenging to achieve in cases of unstable distal-third clavicle fractures, particularly in comminuted distal fragments. In some comminuted fracture cases, it is difficult to insert even 2
ARTICLE IN PRESS Hook plate for distal clavicle fracture distal screws. Although recent studies have demonstrated satisfactory clinical and radiologic outcomes after treating Neer type II distal clavicle fracture using anatomic clavicle LCP,19,25 we thought that it would be difficult to control the force of the trapezius pulling on the proximal fragment superiorly if we could not insert enough screws in the distal fragment with anatomic clavicle LCP. Therefore, we hypothesized that the AO hook LCP could be an alternative option. Although there is no consensus as to a “gold standard” fixation method for Neer type II distal clavicle fractures, we obtained satisfactory outcomes using the AO hook LCP, despite not repairing or augmenting the coracoclavicular ligament. The favorable outcomes of this study may be due to the traits of the AO hook LCP. Just as in cases of acromioclavicular joint dislocation, this plate does not compress the fracture site firmly but instead works like a lever arm to maintain the level and alignment between the distal fragment and the proximal fragment, which may have migrated superiorly. In our study, we could not perform anatomic reduction and firm fixation for the distal portion of fracture in all cases, but we tried to maintain the level and alignment between the distal and proximal fragments using the AO hook LCP. Our results show that the mean increase in CCD was 7.6% compared with a preoperative measurement from the uninjured side. The extent of CCD increase in this study is comparable to that of studies using other techniques, such as anatomic clavicle LCP or suture anchors for distal clavicle fixation.19,20 Also, there was no significant difference in the mean increase in CCD between the 2 groups. This suggests that the clavicle hook plate has a positive role in preventing the proximal fragment from migrating superiorly and in maintaining the acromioclavicular joint level. We also showed that the hook plate works well regardless of Neer type IIA and type IIB. In this study, we report a high union rate, just as in other studies using the AO hook LCP.7,9,13,22,23 There have been many studies reporting the efficacy of the hook plate for distal-third clavicle fractures. Tiren et al reported a high fracture union rate (96%) and high shoulder scores, such as Constant-Murley score and Disabilities of the Arm, Shoulder, and Hand score, at midterm follow-up.23 Muramatsu et al also reported that all fractures in their study achieved solid bone union within 4 months after surgery (n = 15) with excellent clinical results.13 One weakness of this study is that we compared the union rate between Neer type IIA and type IIB in distal-third clavicle fractures, which show a high union rate when treated surgically. However, we hypothesized that there would be a difference in union rate between the 2 groups; namely, we thought that the union rate in group B would be lower because there were more comminuted cases than in group A, making firm distal fixation more difficult to be obtained in that group. Contrary to our initial hypothesis, there was no difference between the 2 groups, and complete union was obtained in all patients. Good clinical and radiologic outcomes have been reported in many other
5 studies using AO hook LCP fixation for distal clavicle fractures as well. Therefore, AO hook LCP is a suitable option for treating distal clavicle fractures of Neer type IIA and type IIB. There were a few complications related to use of the hook plate in distal-third clavicle fractures. Lin et al demonstrated subacromial impingement syndrome and rotator cuff lesions by musculoskeletal sonography12; subacromial osteolysis and erosion were other commonly reported complications.1,21 Several authors have reported that complications of the hook plate were related to late implant removal, and most complications disappeared after removal of the hook plate.5,6,21,23 Therefore, many surgeons have suggested early implant removal to minimize the complications of the AO hook LCP. Good et al showed the best outcomes when the plate was removed before 6 months postoperatively.5 In this study, we removed the hook plate as soon as bone union was achieved to minimize complications We observed 6 subacromial erosions, and 8 patients experienced stiffness after the operation. Shoulder stiffness after distal-third clavicle fracture surgery using the AO hook LCP has not been reported frequently in other studies. In all patients with stiffness in our study, there was comminution of the distal fragment, and we did not encourage the patients to perform active rehabilitation exercises, even 6 weeks after surgery, as there was doubt about secure fixation. Fortunately, all those patients had complete union and recovered full ROM through concomitant arthroscopic capsular release during hardware removal. Our study had some limitations. First, the study was retrospective and did not have a control group to compare AO hook LCP with other fixation methods. Second, the sample size was small, which may have resulted in a type II error caused by low statistical power. With a larger sample size, our conclusions might be more convincing.
Conclusion AO hook LCP fixation for distal-third clavicle fracture (Neer type II) exhibited satisfactory clinical and radiologic outcomes, including high union rates and satisfactory maintenance of CCD, without any significant differences between patients with Neer type IIA and type IIB injuries. There were also no significant differences between the 2 groups with regard to complications after surgery. The AO hook LCP is a suitable choice for Neer type II distal-third clavicle fracture fixation, regardless of subtype.
Acknowledgments The authors would like to thank Dong-Su Jang, MFA (Medical Illustrator, Medical Research Support Section, Yonsei University College of Medicine, Seoul, Korea), for his help with the illustrations.
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Disclaimer 12.
The authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.
13.
14.
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ORIGINAL ARTICLE
Clavicle hook plate fixation for distal-third clavicle fracture (Neer type II): comparison of clinical and radiologic outcomes between Neer types IIA and IIB Wonyong Lee, MD, Chong-Hyuk Choi, MD, PhD, Yun-Rak Choi, MD, PhD, Kyung-Han Lim, MD, Yong-Min Chun, MD, PhD* The Department of Orthopaedic Surgery, Arthroscopy and Joint Research Institute, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea Background: The purpose of this study was to investigate clinical and radiologic outcomes of clavicle hook plate fixation for distal-third clavicle fracture (Neer type II) and to compare the clinical and radiologic outcomes and complications between Neer type IIA and type IIB. Methods: We retrospectively reviewed 35 patients who underwent open reduction and internal fixation with AO hook locking compression plate (LCP) for distal clavicle fracture, including 13 patients with Neer type IIA and 22 patients with type IIB. Visual analog scale pain score, shoulder scores (subjective shoulder value, University of California–Los Angeles shoulder score, American Shoulder and Elbow Surgeons score), and active range of motion were evaluated to determine clinical outcome. Coracoclavicular distance was measured, and that of the injured side at last follow-up was compared with that of the uninjured side to evaluate radiologic outcomes. Results: AO hook LCP fixation for distal-third clavicle fracture (Neer type II) produced satisfactory radiologic outcomes, including high union rates (100%) and coracoclavicular distance maintenance, as well as satisfactory clinical outcomes, including visual analog scale score for pain, shoulder scores (subjective shoulder value, University of California–Los Angeles shoulder score, American Shoulder and Elbow Surgeons score), and active range of motion. There were no significant differences between Neer type IIA and type IIB. With regard to complications, 22.9% of patients experienced shoulder stiffness and 17.1% had subacromial erosion; however, there were no significant differences between the 2 groups. Conclusion: The AO hook LCP is a suitable choice for Neer type IIA and type IIB distal-third clavicle fracture fixation. Level of evidence: Level III; Retrospective Cohort Design; Treatment Study © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. Keywords: Distal clavicle fracture; Neer type; unstable; hook plate; plate fixation; coracoclavicular distance
The Institutional Review Board of Severance Hospital approved this study: No. 4-2016-0486. The requirement for informed consent was waived. *Reprint requests: Yong-Min Chun, MD, PhD, The Department of Orthopaedic Surgery, Arthroscopy and Joint Research Institute, Severance Hospital, Yonsei University College of Medicine, CPO Box 8044, 50-1 Yonsei-ro, Seodaemun-gu, Seoul 120-752, Republic of Korea. E-mail addresses: [email protected], [email protected] (Y.-M. Chun). 1058-2746/$ - see front matter © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. http://dx.doi.org/10.1016/j.jse.2016.11.046
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Figure 1
Neer classification of distal clavicle fractures. (A) Neer type IIA. (B) Neer type IIB.
Distal-third clavicle fractures account for approximately 10% to 15% of all clavicle fractures16 and are subdivided into Neer types IIA and IIB, depending on the attachment status of the conoid ligament to the clavicle (Fig. 1). Neer type II distal clavicle fractures are unstable because bidirectional forces function at the fracture site, namely, the unhindered downward pull of the shoulder girdle on the distal fragment and the unimpeded superior pull by the trapezius muscle on the medial fragment.4 As a result, reported rates of delayed union or nonunion are high with conservative, nonsurgical treatment.3,14,18,24 Therefore, surgery is recommended for Neer type II distal clavicle fractures. Various surgical techniques have been introduced, such as K-wire fixation,8 tension band wiring,2 locking plate,19,25 and hook plate.9,17,23 However, there is no consensus as to the “gold standard” of fixation for Neer type II distal clavicle fracture. The AO hook locking compression plate (LCP; Synthes, Solothurn, Switzerland), a fixation technique originally used for acromioclavicular ligament injury, has shown especially good clinical and radiologic outcomes in acute injury by restoring normal coracoclavicular distance (CCD), even without repair or augmentation of the coracoclavicular ligament. Several studies have reported that this hook plate also showed good outcomes when used for Neer type II distal clavicle fracture fixation.5,9,13,23 However, there have been no studies comparing the clinical and radiologic outcomes between Neer type IIA and type IIB fractures treated with the AO hook LCP. The purpose of this study was to investigate the clinical and radiologic outcomes of using AO hook LCP fixation for unstable distal-third clavicle fracture and to compare the outcomes and complications between Neer type IIA and type IIB fractures. We hypothesized that clinical outcomes would not differ between patients with type IIA (group A) and type IIB (group B) fractures but that group B would exhibit higher nonunion rates and increased CCDs than patients in group A.
Materials and methods Study population This is a retrospective study of patients seen from March 2009 to May 2014 for Neer type II distal clavicle fracture fixation using the
AO hook LCP. During this period, 43 patients underwent open reduction and internal fixation with the AO hook LCP for Neer type II distal clavicle fracture. The inclusion criteria were acute fracture within 2 weeks of injury and availability for follow-up at 2 years after surgery. Exclusion criteria were previous surgical history on the affected shoulder and concomitant fracture around the affected shoulder. We retrospectively reviewed the medical records, including radiologic imaging, of 35 patients (13 in group A and 22 in group B) who met these criteria.
Functional and radiologic assessment For functional assessments, we used a visual analog scale (VAS) pain score, the subjective shoulder value (SSV), the American Shoulder and Elbow Surgeons (ASES) score, the University of California– Los Angeles (UCLA) shoulder score, and active range of motion (ROM). ROM was defined as forward flexion in the scapular plane and external rotation with the elbow at the side. Internal rotation was determined by measuring the highest spinal segment the patient could reach with the thumb pointed upward. To facilitate statistical analyses, the spinal segment level was converted to continuous numbers: T1 to T12 levels were represented by 1 through 12; L1 to L5 level were represented by 13 through 17; and the sacrum was represented by 18.10,11,15 An independent examiner blinded to patient data evaluated all values at each postoperative follow-up. For radiologic evaluation, both clavicle anteroposterior views were taken regularly after surgery (at 2 weeks, 6 weeks, 12 weeks, 6 months, and 1 year and annually thereafter). Bone union was defined as bridging callus across the fracture site or invisible fracture line. The CCD, defined as the perpendicular distance from the top of the coracoid process to the lower border of the clavicle, was measured by 2 independent examiners. The individual value was measured, and then the individual mean value was calculated. We compared the CCD of the injured side with that of the uninjured side to evaluate reduction status and to confirm control of superior migration of the proximal fragment by AO hook LCP.
Surgical procedures All patients underwent open reduction and internal fixation in the 20° beach chair position under general anesthesia by a single surgeon. A 9- to 10-cm incision was made on the distal clavicle and acromion. The facture fragments were identified after dissection, and a hook plate was placed under the acromion and on the fracture site extending medially. We checked the status of reduction, depth of
ARTICLE IN PRESS Hook plate for distal clavicle fracture Table I
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Patient demographics
Sex, male/female Age (years) Side of injury, right/left Time to surgery (days) Proportion of comminuted fracture Time for implant removal (months)
Total (N = 35)
Neer type IIA (n = 13)
Neer type IIB (n = 22)
P value
24/11 40.7 ± 12.3 (22-62) 20/15 4.4 ± 2.4 (1-10) 45.7% (n = 16) 4.4 ± 1.2 (3-8)
9/4 41.8 ± 10.6 (22-54) 8/5 4.1 ± 1.7 (2-8) 30.8% (n = 4) 4.2 ± 1.2 (3-8)
15/7 40.0 ± 13.5 (22-62) 12/10 4.5 ± 2.8 (1-10) 54.5% (n = 12) 4.5 ± 1.3 (3-8)
.105 .124 .737 .775 .293 .511
the hook, and contour of the plate on the distal clavicle under fluoroscopic guidance. Adjustments of the plate contour with appropriate hook depth were made until optimal reduction and contour of the plate were achieved. Then, locking screw fixation of both medial and lateral fragments was performed. Even though an additional coracoclavicular ligament repair was not performed, the deltotrapezius fascial repair for reinforcement was done securely over the plate.
Table II
Injury mechanism
Fall down Bicycle accident Sports injury Traffic accident
Total (N = 35)
Neer type IIA (n = 13)
Neer type IIB (n = 22)
19 10 5 1
7 5 1 0
12 5 4 1
Postoperative rehabilitation and implant removal Regardless of Neer type, the affected arm was kept in a sling for 6 weeks after surgery. Pendulum exercise, self-assisted circumduction exercise, and gradual passive ROM began on the first day after surgery, as tolerable. At 6 weeks postoperatively, active ROM exercise began. After 3 months, the implant was removed if bone union was obtained; if not, implant removal was delayed until union was observed. If the patient experienced shoulder stiffness at the time of implant removal, brisement under general anesthesia and subsequent arthroscopic capsular release were performed concomitantly.
Statistical analysis Statistical analyses were performed using the SPSS software program (version 21.0; IBM, Armonk, NY, USA). The Mann-Whitney test was used to compare numerical data, such as VAS pain scores, ASES scores, UCLA shoulder scores, and the mean increase in CCD, between the 2 groups. A Wilcoxon signed rank test was used to compare preoperative and postoperative CCD values within each group. Fisher exact test was used to compare categorical data. Statistical significance was set at P < .05.
Results Patient demographics We identified a total of 35 patients, including 24 men and 11 women. The mean age of the patients at the time of operation was 40.7 ± 12.3 years overall (range, 22-62 years). The right arm was affected in 20 patients and the left arm was affected in 15 patients, with 8 right arms and 5 left arms in group A and 12 right arms and 10 left arms in group B. The mean time to surgery was 4.4 ± 2.4 days (range, 1-10 days). A total of 45.7% of patients had comminuted fractures, including 30.8% in group A and 54.5% in group B. All patients underwent plate removal surgery, and the mean time to removal of the hook plate was 4.4 ± 1.2 months (range, 3-8 months). There were no significant differences in patient demograph-
ic data (Table I). With regard to injury mechanism, 19 patients fell down, 10 patients experienced bicycle trauma, 1 patient was involved in a traffic accident, and 5 patients were injured during winter sports—3 during snowboarding and 2 during skiing (Table II).
Functional outcomes and radiologic outcomes At the 2-year follow-up, the mean VAS pain score was 1.4 ± 0.9 (range, 0-3). The mean SSV was 84.4 ± 9.1 (range, 60-100). The mean UCLA score was 32.6 ± 2.2 (range, 2635). The mean ASES score was 83.5 ± 7.9 (range, 66.7100). There were no significant differences in VAS pain scores and shoulder scores (SSV, UCLA, and ASES) between group A and group B. The mean active forward flexion was 157° ± 4° (range, 150°-165°). The mean active external rotation was 49° ± 3° (range, 44°-54°). The mean active internal rotation was 10 ± 1 (range, 9-12). There were no significant differences in active ROM between the 2 groups (Table III). Bone union was obtained in all patients. The mean preoperative CCD was 19.9 ± 3.6 mm (range, 13.2-28.8 mm), and the mean postoperative CCD at last follow-up was 11.3 ± 1.0 mm (range, 9.5-13.0 mm). Although there was a significant difference in preoperative CCD values between the 2 groups, there was no significant difference in mean postoperative CCD at last follow-up. The mean increase in CCD at final follow-up was 7.6% ± 2.2% (range, 3.1%-13.9%) compared with a preoperative measurement from the uninjured side; there was no significant difference between the 2 groups (Table IV).
Postoperative complications Postoperative stiffness occurred in 22.9% of all patients (n = 8), including 15.4% of group A (n = 2) and 27.3%
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W. Lee et al. Table III
Functional and clinical outcomes at last follow-up according to Neer type IIA and type IIB
VAS score SSV UCLA score ASES score Forward flexion External rotation Internal rotation
Total
Neer type IIA
Neer type IIB
P value
1.4 ± 0.9 (0-3) 84.4 ± 9.1 (60-100) 32.6 ± 2.2 (26-35) 83.5 ± 7.9 (66.7-100) 157° ± 4° (150°-165°) 49° ± 3° (44°-54°) 10 ± 1 (9-12)
1.5 ± 1.0 (0-3) 80.9 ± 11.2 (60-100) 33.2 ± 1.2 (31-35) 83.5 ± 6.4 (68.3-93.3) 158° ± 4° (152°-165°) 50° ± 3° (44°-54°) 10 ± 1 (9-12)
1.4 ± 0.8 (0-3) 86.6 ± 7.0 (70-100) 32.3 ± 2.6 (26-35) 83.6 ± 8.9 (66.7-100) 156° ± 4° (150°-162°) 48° ± 2° (44°-52°) 11 ± 1 (9-12)
.601 .130 .261 .906 .159 .130 .243
VAS, visual analog scale; SSV, subjective shoulder value; UCLA, University of California–Los Angeles; ASES, American Shoulder and Elbow Surgeons.
Table IV
Change in CCD according to Neer classification type IIA and type IIB
Preoperative uninjured side (mm) Preoperative injured side (mm) Last follow-up injured side (mm) Mean increase in CCD (%)
Total
Neer type IIA
Neer type IIB
P value
10.5 ± 1.0 (8.7-12.5) 19.9 ± 3.6 (13.2-28.8) 11.3 ± 1.0 (9.5-13.0) 7.6 ± 2.2 (3.1-13.9)
10.9 ± 0.9 (9.7-12.5) 17.7 ± 3.5 (13.2-20.9) 11.6 ± 0.9 (10.1-13.0) 6.9 ± 2.3 (3.1-11.6)
10.3 ± 1.0 (8.7-12.1) 21.4 ± 3.6 (14.5-28.8) 11.1 ± 1.0 (9.5-12.9) 8.1 ± 2.1 (4.9-13.9)
.070 .001 .131 .134
CCD, coracoclavicular distance.
Table V
Complications
Nonunion Delayed union Stiffness Subacromial erosion
Total (N = 35)
Neer type IIA (n = 13)
Neer type IIB (n = 22)
0 2.9% (n = 1) 22.9% (n = 8) 17.1% (n = 6)
0 0% (n = 0) 15.4% (n = 2) 30.8% (n = 4)
0 4.5% (1) 27.3% (n = 6) 9.1% (n = 2)
of group B (n = 6), although all patients were taught how to perform pendulum exercise and self-assisted circumduction exercise on the first day after surgery. For patients experiencing stiffness, we performed concomitant arthroscopic capsular release during the hardware removal operation. We educated and encouraged patients to perform passive ROM exercises including pendulum exercise on the first day after surgery to prevent shoulder stiffness. Despite these efforts, some patients were not compliant and experienced stiffness. We attempted physiotherapy for these patients; however, there was still no improvement. Therefore, we conducted brisement and arthroscopic capsular release under general anesthesia during the hardware removal operation. After arthroscopic capsular release, all patients recovered full ROM. In addition, 17.1% of patients (n = 6) had subacromial erosion, including 30.8% in group A (n = 4) and 9.1% in group B (n = 2) (Table V). Subacromial erosion was diagnosed on plain radiograph, and those patients had no specific symptom. After implant removal, there were no patients who complained of acromioclavicular joint pain. Except for shoulder stiffness and subacromial erosion, we did not find other postoperative complications, such as acromial fracture and infection.
Discussion The purpose of this study was to evaluate the clinical outcomes of displaced distal-third clavicle fractures treated with open reduction and internal fixation by a clavicle hook plate and to compare the outcomes according to Neer subtype classification (Neer type IIA and type IIB). Contrary to our initial hypothesis, there were no significant differences in nonunion rate or CCD change between patients with Neer type IIA and type IIB injuries. On the other hand, our results show satisfactory clinical and radiologic outcomes in both groups with no significant differences between the 2 groups. Shin et al19 reported satisfactory clinical outcomes and high union rates using anatomic clavicle LCP fixation in patients with unstable distal clavicle fractures, even when the lateral fragment was small. They tried to insert more than 4 small screws in the distal fragment to achieve secure fixation. Even though the aim of open reduction and internal fixation is to obtain absolute stability, it is challenging to achieve in cases of unstable distal-third clavicle fractures, particularly in comminuted distal fragments. In some comminuted fracture cases, it is difficult to insert even 2
ARTICLE IN PRESS Hook plate for distal clavicle fracture distal screws. Although recent studies have demonstrated satisfactory clinical and radiologic outcomes after treating Neer type II distal clavicle fracture using anatomic clavicle LCP,19,25 we thought that it would be difficult to control the force of the trapezius pulling on the proximal fragment superiorly if we could not insert enough screws in the distal fragment with anatomic clavicle LCP. Therefore, we hypothesized that the AO hook LCP could be an alternative option. Although there is no consensus as to a “gold standard” fixation method for Neer type II distal clavicle fractures, we obtained satisfactory outcomes using the AO hook LCP, despite not repairing or augmenting the coracoclavicular ligament. The favorable outcomes of this study may be due to the traits of the AO hook LCP. Just as in cases of acromioclavicular joint dislocation, this plate does not compress the fracture site firmly but instead works like a lever arm to maintain the level and alignment between the distal fragment and the proximal fragment, which may have migrated superiorly. In our study, we could not perform anatomic reduction and firm fixation for the distal portion of fracture in all cases, but we tried to maintain the level and alignment between the distal and proximal fragments using the AO hook LCP. Our results show that the mean increase in CCD was 7.6% compared with a preoperative measurement from the uninjured side. The extent of CCD increase in this study is comparable to that of studies using other techniques, such as anatomic clavicle LCP or suture anchors for distal clavicle fixation.19,20 Also, there was no significant difference in the mean increase in CCD between the 2 groups. This suggests that the clavicle hook plate has a positive role in preventing the proximal fragment from migrating superiorly and in maintaining the acromioclavicular joint level. We also showed that the hook plate works well regardless of Neer type IIA and type IIB. In this study, we report a high union rate, just as in other studies using the AO hook LCP.7,9,13,22,23 There have been many studies reporting the efficacy of the hook plate for distal-third clavicle fractures. Tiren et al reported a high fracture union rate (96%) and high shoulder scores, such as Constant-Murley score and Disabilities of the Arm, Shoulder, and Hand score, at midterm follow-up.23 Muramatsu et al also reported that all fractures in their study achieved solid bone union within 4 months after surgery (n = 15) with excellent clinical results.13 One weakness of this study is that we compared the union rate between Neer type IIA and type IIB in distal-third clavicle fractures, which show a high union rate when treated surgically. However, we hypothesized that there would be a difference in union rate between the 2 groups; namely, we thought that the union rate in group B would be lower because there were more comminuted cases than in group A, making firm distal fixation more difficult to be obtained in that group. Contrary to our initial hypothesis, there was no difference between the 2 groups, and complete union was obtained in all patients. Good clinical and radiologic outcomes have been reported in many other
5 studies using AO hook LCP fixation for distal clavicle fractures as well. Therefore, AO hook LCP is a suitable option for treating distal clavicle fractures of Neer type IIA and type IIB. There were a few complications related to use of the hook plate in distal-third clavicle fractures. Lin et al demonstrated subacromial impingement syndrome and rotator cuff lesions by musculoskeletal sonography12; subacromial osteolysis and erosion were other commonly reported complications.1,21 Several authors have reported that complications of the hook plate were related to late implant removal, and most complications disappeared after removal of the hook plate.5,6,21,23 Therefore, many surgeons have suggested early implant removal to minimize the complications of the AO hook LCP. Good et al showed the best outcomes when the plate was removed before 6 months postoperatively.5 In this study, we removed the hook plate as soon as bone union was achieved to minimize complications We observed 6 subacromial erosions, and 8 patients experienced stiffness after the operation. Shoulder stiffness after distal-third clavicle fracture surgery using the AO hook LCP has not been reported frequently in other studies. In all patients with stiffness in our study, there was comminution of the distal fragment, and we did not encourage the patients to perform active rehabilitation exercises, even 6 weeks after surgery, as there was doubt about secure fixation. Fortunately, all those patients had complete union and recovered full ROM through concomitant arthroscopic capsular release during hardware removal. Our study had some limitations. First, the study was retrospective and did not have a control group to compare AO hook LCP with other fixation methods. Second, the sample size was small, which may have resulted in a type II error caused by low statistical power. With a larger sample size, our conclusions might be more convincing.
Conclusion AO hook LCP fixation for distal-third clavicle fracture (Neer type II) exhibited satisfactory clinical and radiologic outcomes, including high union rates and satisfactory maintenance of CCD, without any significant differences between patients with Neer type IIA and type IIB injuries. There were also no significant differences between the 2 groups with regard to complications after surgery. The AO hook LCP is a suitable choice for Neer type II distal-third clavicle fracture fixation, regardless of subtype.
Acknowledgments The authors would like to thank Dong-Su Jang, MFA (Medical Illustrator, Medical Research Support Section, Yonsei University College of Medicine, Seoul, Korea), for his help with the illustrations.
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Disclaimer 12.
The authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.
13.
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