Abstract
Background
AO clavicular hook plates have been widely used for treating acromioclavicular (AC) joint dislocation and distal clavicle fractures. Many complications have been reported, and many patients have complained about the discomfort of the plate. However, no study on the impact of clavicular hook plates in AC joint 3D printing models has been reported.
Objective
To evaluate the matching performance of hook plates with different hook depths when they were implanted in 3D printing models of normal Chinese AC joints and to propose a further design to achieve a better match.
Methods
AO clavicular hook plates with two different hook depths of 15 mm and 18 mm were implanted in 3D printing models of forty Chinese normal AC joints. The angle between the distal clavicle and plate (CPA) and the drop between acromion and distal clavicle (ACD) of normal AC joints with and without plates were measured.
Results
Mismatch was found when the hook plates were implanted, with an average CPA of 18.8 ± 5.1° with the 15-mm hook plate and 10.2 ± 4.9° with the 18-mm hook plate. To eliminate the CPA, the ACD decreased by 6.3 ± 1.1 mm with the 15-mm hook plate and 2.9 ± 0.9 mm with the 18-mm hook plate.
Conclusions
The results revealed that AO clavicular hook plates with different hook depths were very likely to result in over-reduction of the AC joint. It is necessary to bend the hook angle to fit the patient’s AC joint to achieve accurate reduction.
Keywords: Acromioclavicular joint, Hook plate, 3D printing, Matching performance
Introduction
Open reduction and internal fixation (ORIF) with a clavicular hook plate is a simple and effective treatment for treating AC joint dislocation and distal clavicle fractures [1–6]. As hook plates have been widely used, many complications, such as subacromial osteolysis, rotator cuff impingement, rotator cuff tears, and peri-implant fractures, have been reported after the implantation of clavicular hook plates for AC joint dislocation and distal clavicle fracture treatment [7–11]. In many cases, shoulder function and pain can be improved after removal of the hook plate. These complications may be related to the mismatch between the AC joint and the clavicular hook plate [12, 13]. Nevertheless, we do not know what happens to the structure of the AC joint after the plate is implanted.
This study aimed to assess the matching performance of the hook plate and to determine the impact of the plate on the structure of the AC joint after implantation based on a 3D printing model.
Materials and Methods
In this study, 40 normal shoulder joint CT data (Siemens 64-slice spiral CT, DICOM format) of adults (20 males, 20 females) with a mean age of 58.4 ± 5.2 years (from 44 year to 76 year) who had undergone CT of the proximal humerus between Apr 2016 and Oct 2018 were selected from the previous imaging database of the hospital. Among the shoulder joint image data, 14 were left shoulder joints and 26 were right shoulder joints. During the CT scan, patients were placed in the supine position, with the arms along the lateral sides of the body and with the shoulder in a neutral position. The slice thickness was 0.6 mm. Cases involving deformities, osteoarthritis, and tumors were excluded. The scan results were delivered in a data imaging and communications in medicine (DICOM) format. Then, CT data were imported into an interactive medical image control system 19.0 (MIMICS 19.0 by Materialise, Belgium). The threshold was set to 180–3071 HU, and the bone tissues were separated using the thresholding tool. The AC joints were reconstructed into 3D models using the Calculate 3D tool. The Morphology operation tool was used to fill the small voids on the surface and to smooth the surface of the bone structure. The AC joint models were then exported to an STL (Standard Triangulation Language) format file. The AC joint models were imported into Rhino 5.1 (Robert McNeel, USA). As the clavicle and scapula are separated from each other, a connecting rod 1 cm in diameter was used to connect the proximal clavicle and the medial aspect of the scapula to maintain a relative position (Fig. 1). Then, the AC joint 3D models were 3D printed utilizing a UV-curing printing technique via a 3D printing machine (SLA660, ZRapid Tech Inc., Jiangsu, China). Off-white resin material with an accuracy of 0.1 mm was used to 3D print the digital skeleton models (Fig. 2). AO clavicular hook plates (DePuy Synthes, Bettlach, Switzerland) with two different hook depths of 15 mm and 18 mm (Fig. 3) were implanted into the normal 3D printing models of the acromioclavicular joints similar to the surgery we performed for the treatment of AO joint dislocation. The angle between the distal clavicle and plate (CPA) and the drop between acromion and distal clavicle (ACD) with and without plates were measured (Fig. 4). The differences in the ACD with and without plates were calculated.
Fig. 1.
Connecting rod 1 cm in diameter was used to connect the proximal clavicle and the medial aspect of the scapula to maintain a relative position
Fig. 2.
3D printing AC joint model (off-white resin material, accuracy of 0.1 mm)
Fig. 3.
AO clavicular hook plates with two different hook depths of 15 mm and 18 mm
Fig. 4.
a Drop between the distal clavicle and acromion (ACD). b Angle between the distal clavicle and plate (CPA). c The ACD changed after the hook plate was implanted
The ACD was measured with an electronic digital caliper (accuracy 0.1 mm) and was recorded in millimeters. The CPA was determined in degrees with a goniometer (accuracy 1°). Each measurement was taken three times, and the mean value was calculated for use in the data analysis.
The program SPSS 23.0 (SPSS Inc., Chicago, IL, USA) was used for the statistical evaluation of the measurement results. Mean values and standard deviations of the results were calculated.
Results
Measurements of 40 3D printing AC joint models with and without plates are documented in Table 1.
Table 1.
Measurements of 40 3D printing AC joint models with and without plate
| No. | Gender | ACD (mm) | 15 mm hook plate | 18 mm hook plate | ||||
|---|---|---|---|---|---|---|---|---|
| CPA (°) | ACD (mm) | ΔACD (mm) | CPA (°) | ACD (mm) | ΔACD (mm) | |||
| 1 | F | 4.6 | 15.0 | − 1.1 | 5.7 | 5.0 | 2.7 | 1.9 |
| 2 | F | 4.9 | 16.0 | − 1.2 | 6.1 | 8.0 | 2.5 | 2.4 |
| 3 | F | 5.2 | 14.0 | − 1.5 | 6.7 | 6.0 | 2.2 | 3.0 |
| 4 | F | 4.3 | 17.0 | − 0.5 | 4.8 | 10.0 | 2.5 | 1.8 |
| 5 | F | 4.8 | 18.0 | − 0.6 | 5.4 | 7.0 | 2.7 | 2.1 |
| 6 | F | 4.7 | 12.0 | − 2.1 | 6.8 | 3.0 | 3.1 | 1.6 |
| 7 | F | 5.1 | 13.0 | − 0.5 | 5.6 | 7.0 | 2.3 | 2.8 |
| 8 | F | 4.9 | 13.0 | − 0.5 | 5.4 | 10.0 | 2.5 | 2.4 |
| 9 | F | 5.3 | 22.0 | − 1.1 | 6.4 | 9.0 | 2.0 | 3.3 |
| 10 | F | 4.8 | 18.0 | 0.8 | 4.0 | 12.0 | 3.5 | 1.3 |
| 11 | F | 5.3 | 20.0 | − 1.2 | 6.5 | 10.0 | 2.0 | 3.3 |
| 12 | F | 5.0 | 15.0 | − 0.2 | 5.2 | 8.0 | 2.2 | 2.8 |
| 13 | F | 5.4 | 25.0 | − 1.0 | 6.4 | 13.0 | 2.0 | 3.4 |
| 14 | F | 4.8 | 16.0 | − 0.5 | 5.3 | 5.0 | 2.4 | 2.4 |
| 15 | F | 5.3 | 18.0 | − 0.8 | 6.1 | 12.0 | 2.4 | 2.9 |
| 16 | F | 5.5 | 22.0 | − 0.6 | 6.1 | 10.0 | 2.1 | 3.4 |
| 17 | F | 5.1 | 18.0 | − 1.5 | 6.6 | 15.0 | 1.2 | 3.9 |
| 18 | F | 4.6 | 12.0 | − 0.5 | 5.1 | 9.0 | 1.8 | 2.8 |
| 19 | F | 4.4 | 10.0 | 0.0 | 4.4 | 6.0 | 2.8 | 1.6 |
| 20 | F | 5.3 | 14.0 | − 1.2 | 6.5 | 6.0 | 2.2 | 3.1 |
| 21 | M | 5.2 | 15.0 | − 1.8 | 7.0 | 7.0 | 1.8 | 3.4 |
| 22 | M | 4.8 | 17.0 | 1.1 | 3.7 | 4.0 | 3.5 | 1.3 |
| 23 | M | 5.5 | 32.0 | − 1.0 | 6.5 | 22.0 | 1.0 | 4.5 |
| 24 | M | 5.7 | 30.0 | − 1.8 | 7.5 | 18.0 | 1.1 | 4.6 |
| 25 | M | 5.2 | 22.0 | − 1.6 | 6.8 | 15.0 | 1.2 | 4.0 |
| 26 | M | 5.3 | 24.0 | − 2.3 | 7.6 | 17.0 | 1.3 | 4.0 |
| 27 | M | 4.9 | 15.0 | − 1.1 | 6.0 | 4.0 | 3.5 | 1.4 |
| 28 | M | 5.7 | 28.0 | − 1.3 | 7.0 | 22.0 | 1.4 | 4.3 |
| 29 | M | 5.5 | 24.0 | − 0.9 | 6.4 | 18.0 | 1.9 | 3.6 |
| 30 | M | 5.3 | 26.0 | − 1.2 | 6.5 | 12.0 | 1.5 | 3.8 |
| 31 | M | 4.8 | 15.0 | − 3.2 | 8.0 | 5.0 | 2.8 | 2.0 |
| 32 | M | 5.2 | 17.0 | − 1.6 | 6.8 | 8.0 | 1.8 | 3.4 |
| 33 | M | 4.9 | 15.0 | − 2.5 | 7.4 | 8.0 | 2.1 | 2.8 |
| 34 | M | 5.5 | 23.0 | − 1.3 | 6.8 | 12.0 | 1.5 | 4.0 |
| 35 | M | 5.0 | 18.0 | − 0.8 | 5.8 | 7.0 | 2.4 | 2.6 |
| 36 | M | 5.2 | 22.0 | − 3.5 | 8.7 | 14.0 | 1.5 | 3.7 |
| 37 | M | 4.6 | 18.0 | − 1.9 | 6.5 | 4.0 | 2.4 | 2.2 |
| 38 | M | 5.2 | 22.0 | − 3.1 | 8.3 | 13.0 | 2.7 | 2.5 |
| 39 | M | 5.2 | 21.0 | − 2.5 | 7.7 | 12.0 | 1.7 | 3.5 |
| 40 | M | 5.6 | 18.0 | − 1.3 | 6.9 | 15.0 | 1.8 | 3.8 |
| Mean ± SD | 5.1 ± 0.3 | 18.8 ± 5.1 | − 1.2 ± 1 | 6.3 ± 1.1 | 10.2 ± 4.9 | 2.2 ± 0.6 | 2.9 ± 0.9 | |
| Female | 5.0 ± 0.3 | 16.4 ± 3.8 | − 0.8 ± 0.6 | 5.8 ± 0.8 | 8.6 ± 3 | 2.4 ± 0.5 | 2.6 ± 0.7 | |
| Male | 5.2 ± 0.3 | 20.8 ± 5.3 | − 1.7 ± 1 | 6.9 ± 1 | 11.6 ± 5.8 | 2.0 ± 0.7 | 3.3 ± 1 | |
ΔACD the difference of ACD between with plate and without plate
ACD acromioclavicular drop, CPA angle between clavicle and plate
On the 3D printing models of normal AC joints, the ACD was 5.1 ± 0.3 mm (female 5.0 ± 0.3 mm, male 5.2 ± 0.3 mm). The CPA was 18.8 ± 5.1° (female 16.4 ± 3.8°, male 20.8 ± 5.3°) with the 15-mm hook plate and 8.6 ± 3.0° (female 16.4 ± 3.8°, male 20.8 ± 5.3°) with the 18-mm hook plate. To eliminate the gap between the clavicle and the plate, with pressure on the medial side of the plate, the ACD decreased from 5.1 ± 0.3 mm to − 1.2 ± 1.0 mm (ΔACD = 6.3 ± 1.1 mm) with the 15-mm hook plate and decreased from 5.1 ± 0.3 mm to 2.2 ± 0.6 mm (ΔACD = 2.9 ± 0.9 mm) with the 18-mm hook plate.
Discussion
The clavicular hook plate uses the principles of a lever to reduce the AC joint, which makes the operation much easier. The unique hook shape of the clavicular hook plate can provide good stability [14, 15].
Although the hook plate has many advantages, complications with hook plates have been reported in many studies. Many morphological studies of AC joint and hook plate based on cadaver and CT data have been reported [16–19], but none of them used 3D printing models. With the help of the 3D printing model, this study revealed what would happen after we implanted a hook plate without pre-contouring. Moreover, with 3D printing technology, we could bend the plate to fit the AC joint model to achieve accurate reduction [20], which makes the study more valuable to the clinic.
After the hook plate was implanted on a normal 3D printing AC joint model, the CPA was considerable and resulted in a typical mismatch of the plate (Fig. 5). There are two options to eliminate the gap between the plate and the clavicle:
Compress the medial part of the plate to allow for better contact between the plate and the clavicle (Fig. 6).
Bend the hook to increase the hook angle to the same degree as the CPA to fit the AC joint (Fig. 7).
Fig. 5.
Typical mismatch of the hook plate with a normal AC joint
Fig. 6.
To allow for better contact between the plate and the clavicle, the ACD was decreased, and the hook occupied a large area under the acromion (red area)
Fig. 7.
Increase the hook angle to allow a better fit with the AC joint
If the first option is chosen, the ACD will be obviously decreased, and the pressure between the plate and the bones will be definitely increased, which might result in severe pain and discomfort in terms of the plate. Furthermore, as an amphiarthrodial joint, the AC joint has its own range of motion. If the AC joint is over-reduced and the range of motion is limited, this will very likely result in a poor outcome.
In this study, we found that the CPA was 18.8 ± 5.1° (range from 10° to 32°) with the 15-mm hook plate and 10.2 ± 4.9° (range from 3° to 22°) with the 18-mm hook plate. It is better to choose the second option with an increase in the hook angle to decrease the CPA to make a better fit than it is to over-reduce the AC joint. Moreover, increasing the hook degree will reduce the space occupied by the hook implant under the acromion, which will reduce the risk of subacromial impingement [21, 22].
During the operation, it is not easy to bend the hook precisely if the surgeon does not know the CPA of the plate on a normal AC joint. Therefore, we recommend pre-contouring the hook angle on a mirrored contralateral 3D printing AC joint model before the operation [20].
Conclusions
The results revealed that AO clavicular hook plates with different hook depths were very likely to result in over-reduction of the AC joint. It is necessary to bend the hook angle to fit the patient’s AC joint to achieve accurate reduction.
Acknowledgements
We would like to thank the Central Laboratory of the First Affiliated Hospital of Soochow University for the technical guidance.
Abbreviations
- AC
Acromioclavicular
- CPA
Angle between clavicle and plate
- ORIF
Open reduction and internal fixation
- ACD
Drop between the distal clavicle and acromion
Author contribution
XW conceived the study, and XW and GW participated in its design and coordination. QX and KR performed the operations. XW, XY, and GW analyzed the data and drafted the manuscript. All authors interpreted the data and participated in drafting the text and tables. All authors read and approved the final manuscript.
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Data availability
The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.
Compliance with Ethical Standards
Conflict of interest
The authors declare that they have no competing interests.
Ethical standard statement
The Ethics Committee of the First Affiliated Hospital of Soochow University approved this study.
Informed consent
Not applicable.
Footnotes
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Xuhua Wu and Gang Wang are co-first authors.
Contributor Information
Xuhua Wu, Email: johnwoo1983@alumni.sjtu.edu.cn.
Gang Wang, Email: wangpingguo520@163.com.
Qingquan Xia, Email: talentedbird@aliyun.com.
Ke Rong, Email: rongke@alumni.sjtu.edu.cn.
Minfeng Gan, Email: ganminfeng@suda.edu.cn.
Gen Wen, Email: wengen2006@126.com.
Xiaofan Yin, Email: 18918169029@189.cn.
Huilin Yang, Email: suzhouspine@outlook.com.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.