Biomechanical analysis of acromioclavicular joint dislocation treated with clavicle hook plates in different lengths

Biomechanical comparison between low profile 2.7 mm distal locking hook plate and 3.5 mm distal locking hook plate for acromioclavicular joint injury: A finite element analysis

PURPOSE

Although hook plate fixation is popularly used, concerns exist regarding periprosthetic fractures and the necessity to remove the plate to prevent subacromial erosion and subsequent acromion fracture, due to its non-anatomical design. We hypothesized that a low profile 2.7 mm distal locking hook plate would provide comparable stability to a properly used 3.5 mm distal locking hook plate MATERIALS AND METHODS: A 3.5 mm distal locking plate (type 1) and a low profile 2.7 mm plate (type 2) were assessed by finite element analysis. Peak von Mises stress (PVMS) was calculated on the acromion's undersurface, clavicle shaft, and hook, focusing on how these stresses varied with the number and placement of distal locking screws.

RESULTS

Increased distal screws in both types led to lower PVMS on the acromion's undersurface and the hook, with the lowest acromion PVMS observed in type 2 with three distal screws, and on the hook in type 1 with two distal screws. Increasing the number of distal screws similarly reduced PVMS on the clavicle shaft, with the lowest in type 1 with two distal screws. In both plate types, the most posterior distal locking screw played a crucial role in distributing stress across the acromion and the hook.

CONCLUSION

The low profile 2.7 mm distal locking hook plate showed comparable biomechanical results to the 3.5 mm distal locking hook plate. Increasing the number of distal locking screws showed less stress concentration on the bone and hook in both models. The most posterior distal locking screw showed an essential role in stress distribution.

Optimizing hook implantation angle of the clavicular hook plate: a cadaveric study

PURPOSE

While Clavicle hook plates have demonstrated favorable results regarding bone and shoulder function, their design can potentially lead to complications due to pressure concentration at the plate's tip. This study aims to investigate the impact of different hook implantation angles on the contact surface area between the hook plate and acromion, with the goal of minimizing mismatch and maximizing contact surface area.

METHODS

Twenty soft shoulder cadavers were included in the study, and the contact surface area of the hook plate was measured in different positions based on the hook implantation angle.

RESULTS

The results showed variations in compatibility, width, and length of the contact surface area depending on the hook implantation angle and the medial or lateral row placement. The lateral row generally demonstrated superior compatibility (84.0% vs 46.67%, p-value < 0.001), with a broader contact area (3.55 ± 0.08 mm vs 3.09 ± 0.10 mm, p-value = 0.004) and a longer contact area (7.36 ± 0.19 mm vs 5.10 ± 0.23 mm, p-value < 0.001) at specific angles. A detailed analysis of the lateral position revealed that the zero angle of implantation resulted in the greatest contact surface area, measuring 3.91 ± 0.70 mm in width (p value = 0.083) and 8.85 ± 1.24 mm in length (p value < 0.001).

CONCLUSION

Placing the hook laterally and at the zero position according to the hook implantation angle can maximize contact surface area, may reduce stress concentration, and minimize complications in hook plate fixation. Further research and consideration of anatomical variations are warranted to refine the placement technique and enhance patient outcomes.

LEVEL OF EVIDENCE

Level V evidence.

Evaluation of the coracoid bone tunnel placement on Dog Bone™ button fixation for acromioclavicular joint dislocation: a cadaver study combined with finite element analysis

BACKGROUND

Dog Bone™ button fixation is frequently used to treat acromioclavicular joint (ACJ) dislocation. However, various studies have reported complications after fixation.

OBJECTIVE

To investigate the effect of the coracoid bone tunnel location on the treatment of ACJ dislocation through single-tunnel coracoclavicular (CC) ligament fixation with the Dog Bone™ button.

METHODS

Six cadaveric shoulders were used. Each specimen was subjected to five testing conditions in the following order: (1) normal ACJ (Gn); (2) acromioclavicular and CC ligaments were removed (G0); (3) CC ligament reconstruction was performed using the Dog Bone™ technique, and the coracoid bone tunnel was at the center of the coracoid base (G1); (4) reconstruction was performed at 5 mm distal from the G1 site, along the axis of the coracoid (G2); (5) reconstruction was performed at 10 mm distal from the G1 site, along the axis of the coracoid (G3). The angles of pronation and supination of the clavicle under the same load (30 N) were measured. Next, a finite element (FE) model was created using computed tomography (CT) images of the normal shoulder. Model 1 (M1), model 2 (M2), and model 3 (M3) correspond to G1, G2, and G3, respectively. A force of 70 N was applied as a vertical upward load to the distal clavicle. Subsequently, the von Mises stress, the strain LE along the FiberWire, and the displacement nephogram of the three models were obtained.

RESULTS

After single-tunnel CC ligament fixation using the Dog Bone™ technique, the clavicle in the G2 group (20.50 (19.50, 21.25) °, 20.00 (18.75, 21.25) °) had the best rotational stability. The peak von Mises stress, the strain LE along the FiberWire, and the maximum displacement were smaller in M2 than in M1 and M3.

CONCLUSIONS

When the coracoid bone tunnel was located 5 mm anterior to the center of the coracoid base (along the axis of the coracoid), the clavicle showed greater rotational stability.

Biomechanical effects of different numbers and locations of screw-in clavicle hook plates

Purpose: We sought to analyze the biomechanical effects which both different numbers and locations of screws have on three different clavicle hook plates, as well as any possible causes of sub-acromial bone erosion and peri-implant clavicular fractures.

Methods: This study built thirteen groups of finite element models using three different clavicle hook plates (short plates, long plates, and posterior hook offset plates) in varying numbers and locations of the screws. The von Mises stress distribution of the clavicle and hook plate, as well as the reaction force of the acromion was evaluated.

Results: The results show that inserting screws in all available screw holes on the hook plate produces a relatively large reaction force on the acromion, particularly in the axial direction of the bone plate. The fewer the screws implanted into the clavicle hook plate, the larger the area of high-stress distribution there is in the middle of the clavicle, and also, the higher the stress distribution on the clavicle hook plate.

Conclusion: This study provides orthopedic physicians with the biomechanical analysis of different numbers and locations of screws in clavicle hook plates to help minimize surgical complications.

Risk factors for clavicular midshaft fractures after hook plate fixation for the treatment of Neer type II clavicular fractures

OBJECTIVE

Neer type II fractures are common, and hook plate fixation is one of the recommended treatments. Although clavicular midshaft fractures after hook plate fixation are rare, such fractures increase patients' suffering and worsen their functional outcomes. This study was performed to identify the risk factors for this complication.

METHODS

From 2009 to 2018, 425 patients were admitted with Neer type II clavicular fractures. According to the selection criteria, 352 patients were included in this retrospective observational study. All patients were divided into either the complications group (patients with midshaft fractures) or the control group (patients without midshaft fractures). Data collected included patient demographics and surgical, hook plate, and screw characteristics. The chi-square test was used to conduct between-group comparisons of risk factors. Statistically significant variables were included in a logistic regression model.

RESULTS

In both the complications group (n = 21) and control group (n = 331), significantly more patients of advanced age and significantly more patients treated with hook plates that were not bent during surgery developed midshaft fractures.

CONCLUSION

The risk of a clavicular midshaft fracture after hook plate fixation may be significantly increased by advanced age or a lack of hook plate bending.

Biomechanical analysis of a novel clavicular hook plate for the treatment of acromioclavicular joint dislocation: A finite element analysis

BACKGROUND

Clavicular hook plates are frequently used in clinical orthopedics to treat acromioclavicular joint dislocation. However, patients often exhibit acromial osteolysis and peri-implant fracture after hook plate fixation. To solve the above problems, we developed a novel double-hook clavicular plate and used finite element analysis (FEA) to investigate its biomechanical properties.

METHODS

A finite element (FE) model was constructed and validated. Then, a double-hook clavicular plate, a single-hook clavicular plate, and an anatomical double-hook clavicular plate was implanted into the acromioclavicular joint and fixed with screws in groups 1, 2 and 3, respectively. Finally, a load was applied, and some indicators were recorded and analyzed.

RESULTS

For both the proximal clavicular rotation angle and the distal clavicular displacement, the range of motion in groups 1 and 3 was more than 90% lower than that in group 2. The maximum von Mises stress of the clavicle in groups 1 and 3 was more than 45% lower than that in group 2. The maximum stress of the acromion in group 2 was significantly higher than that in groups 1 and 3, and that in group 3 was less than that in group 1, for both cortical and cancellous bone.

CONCLUSIONS

The double-hook clavicular plate could immediately reconstruct the stability of the acromioclavicular joint, effectively reducing the stress of the bone around the clavicle and screws. Additionally, the double-hook clavicular plate could reduce the peak stress of the acromion and produce a more uniform stress distribution.

To explore the reasonable selection of clavicular hook plate to reduce the occurrence of subacromial impingement syndrome after operation

Background

Acromioclavicular joint dislocation is a shoulder joint injury common in the clinical setting and is generally surgically treated with clavicular hook plate technique with confirmed curative effect. However, symptoms such as shoulder abduction limitation, shoulder discomfort and joint pain postoperatively may occur in some patients. Therefore, this study aimed to explore whether the existing clavicular hook plate can be reasonably selected to reduce the incidence of subacromial impingement syndrome (SIS) and provide a reference for clinical diagnosis and treatment.

Materials and methods

Patients with SIS admitted from March 2018 to June 2020 were selected as the experimental group and asymptomatic patients postoperatively, as the control group. The hook end depth and acromial height of the hook plate used in patients were recorded, and the difference between them was calculated.

Results

The difference between the hook plate depth and acromial height was 7.500±1.912 mm and 6.563±1.537 mm in the experimental and control groups, respectively, with statistically significant difference (t=3.021, P=0.006). A difference of >0.6 mm as a grouping index is required to perform a single factor analysis, with statistically significant difference (t=3.908, P=0.048).

Conclusions

The occurrence of SIS after placing the clavicular hook plate may be related to the difference between its depth and the acromial height. A difference of >6 mm may be a factor affecting the occurrence of SIS. Pre-imaging measurement of the acromial height can provide suggestions for selecting the type of hook plate intraoperatively.

Peri-implant Fractures Following Hook Plate Fixation for Unstable Distal Clavicle Fractures

Clavicle hook plate is a common implant for treating distal clavicle fracture. Although high bone union rate and good functional outcome have been reported, so have several complications, such as osteolysis and fracture of the acromion, loss reduction, hook impingement, and rotator cuff tear. Peri-implant fracture over the medial side of the hook plate is a rare complication. Sporadic cases have been reported, and most of them have had no history of trauma. Between June 2015 and August 2018, 7 patients treated for distal clavicle fracture with a 3.5-mm locking compression hook plate with no history of trauma experienced peri-implant fracture of the medial clavicle. This complication occurred at a mean of 29 days. The incidence rate was 9.8%. Peri-implant fracture following hook plate fixation for distal clavicle fracture was not rare. Small hook angle, prolonged retention of the implant, an eccentric medial screw, high plate screw density, and small clavicle diameter may be risk factors for peri-implant fracture. Regarding treatment, 2 patients chose fracture revision with a distal clavicle locking plate and 5 patients chose conservative treatment. All patients achieved bone union at fracture sites. Surgical and conservative management of peri-implant fracture can achieve good functional outcome. [Orthopedics. 2020;43(5);e359-e363.].

Relationship between the lateral acromion angle and postoperative persistent pain of distal clavicle fracture treated with clavicle hook plate

Background

The clavicular hook plate is an accepted surgical procedure for distal clavicle fractures. The relationship of the characteristics of the hook plate, acromioclavicular joint and acromion morphology, and clinical outcome has remained poorly understood. We reviewed the clinical records of patients who had distal clavicle fractures with different lateral acromion angles treated using a clavicle hook plate and evaluated their clinical outcomes with respect to shoulder pain and acromial morphology.

Methods

We retrospectively reviewed 102 patients with distal clavicle fractures treated with hook plates at our institution from 2010 to 2017. They were divided into four groups according to lateral acromion angle on shoulder AP view X-rays. The angle was defined as the incline angle between the superior surface of distal clavicle and the inferior facet of acromion on coronal plane. We reviewed their clinical features, including Neer’s impingement sign, MRI findings, and outcomes using Japanese Orthopaedic Association Scores. The mean follow-up was 25.5 months (range, 24 to 28 months).

Results

All patients in group D (large lateral acromion angle (α) > 40°, acromion coronal angle (β) < 60°) complained of postoperative symptoms. Compared to those with common lateral acromion angle, the incidence of postoperative impingement in group D was undoubtedly much higher (100%). Japanese Orthopaedic Association (JOA) scores in group D were worse at 3 months post-surgery, 3 months post plate removal, and at the last follow-up despite a slightly earlier removal in this group.

Conclusion

Lateral acromion angle appears to be an important factor in the development of postoperative pain and worse outcomes (JOA scores) in patients treated with the hook plate. The incidence of subacromial impingement and rotator cuff lesion (RCL) increased with the α angle. Early limited mobility and removal of the implant may improve the prognosis and resolve the postoperative shoulder pain.

Study design

Retrospective review, level of evidence IV.

Comparison of two methods for coracoclavicular ligament reconstruction: A finite element analysis

OBJECTIVE

This study aimed to compare two different tendon grafting techniques for coracoclavicular ligament reconstruction from the data obtained using finite element analysis.

METHODS

Three different finite element models of the shoulder girdle were formulated using computerized tomography images: the reference model, coracoid loop technique (CLT), and drilling technique (DT) model. In all these models, forces were applied to the clavicle along three axes (x, y, and z) of the trapezius and sternocleidomastoid muscles. Thereafter, data regarding the loading values of the tendon grafts, loads on the coracoid base, and coracoclavicular vertical distance were measured.

RESULTS

While the reference model yielded the lowest values for all the loading conditions as well as the shortest coracoclavicular distance, the DT model demonstrated the highest values for all the loading conditions and the largest coracoclavicular distance.

CONCLUSION

Different tendon grafting techniques may offer different loading values on both bone surface and tendon graft during coracoclavicular ligament reconstruction. The drilling technique may be associated with increased loading on the tendon graft and bone surface, causing further loss of reduction and consequent complications.

Three-dimensional scapular dyskinesis in hook-plated acromioclavicular dislocation including hook motion

BACKGROUND

The purpose of this study is to analyze the 3-dimensional scapular dyskinesis and the kinematics of a hook plate relative to the acromion after hook-plated acromioclavicular dislocation in vivo. Reported complications of acromioclavicular reduction using a hook plate include subacromial erosion and impingement. However, there are few reports of the 3-dimensional kinematics of the hook and scapula after the aforementioned surgical procedure.

METHODS

We studied 15 cases of acromioclavicular dislocation treated with a hook plate and 15 contralateral normal shoulders using computed tomography in the neutral and full forward flexion positions. Three-dimensional motion of the scapula relative to the thorax during arm elevation was analyzed using a computer simulation program. We also measured the distance from the tip of the hook plate to the greater tuberosity, as well as the angular motion of the plate tip in the subacromial space.

RESULTS

Decreased posterior tilting (22° ± 10° vs 31° ± 8°) in the sagittal plane and increased external rotation (19° ± 9° vs 7° ± 5°) in the axial plane were evident in the affected shoulders. The mean values of translation of the hook plate and angular motion against the acromion were 4.0 ± 1.6 mm and 15° ± 8°, respectively. The minimum value of the distance from the hook plate to the humeral head tuberosity was 6.9 mm during arm elevation.

CONCLUSIONS

Acromioclavicular reduction using a hook plate may cause scapular dyskinesis. Translational and angular motion of the hook plate against the acromion could lead to subacromial erosion. However, the hook does not seem to impinge directly on the humeral head.

Modified closed-loop double-endobutton technique for repair of rockwood type III acromioclavicular dislocation

Acromioclavicular dislocation (ACD) is a common injury. According to the Rockwood classification, ACD is classified into six types (type I–VI); however, for type III injuries, it remains controversial whether or not operative treatment should be applied. Numerous studies have advocated early surgical treatment to ensure early rehabilitation activities. Thus, the present study aimed to investigate a modified closed-loop double-endobutton technique (MCDT), that may be used to repair Rockwood type III ACD. In the current study, 61 patients with Rockwood type III ACD were enrolled during a period of 5 years at the Affiliated Traditional Chinese Medicine Hospital of Southwest Medical University. Patients were divided into three groups according to the surgical method used, the MCDT group (n=20), the common closed-loop double-endobutton technique (CCDT) group (n=21), and the clavicular hook plate fixation (CHPF) group (n=20). Preoperative and intraoperative information were recorded. Furthermore, the functional scores of injured shoulder were evaluated prior to surgery and following surgery with a 1-year follow-up. Among the three groups, postoperative functional scores were significantly more improved compared with those prior to surgery (P<0.05), and no significant difference was observed regarding the coracoclavicular interval with the 1-year follow-up (P>0.05). Postoperative functional scores in the MCDT and CCDT groups were significantly more improved compared those in the CHPF group (P<0.05). In addition, the duration of surgery in the MCDT group was significantly shorter compared with that in the CCDT group (P<0.05). Furthermore, compared with the CHPF group, the incision length was significantly shorter with reduced hemorrhage in the MCDT group (P<0.05). In conclusion, the results of the current study suggest that MCDT is more simple, convenient and efficient compared with CCDT, and is worth popularizing.

Three-dimensional morphological analysis of acromioclavicular joint in patients with and without subacromial erosion after hook plate fixation

Objective

To investigate the role of acromioclavicular joint morphology in the presence of subacromial erosion after hook plate fixation.

Methods

We retrospectively analyzed the clinical data of 36 patients (17 men, 19 women; mean age, 48.7 years; range, 21–76 years) treated with hook plate fixation for distal clavicular fractures (n = 20) or acromioclavicular joint dislocation (n = 16) from August 2011 to March 2013. The patients were divided into two groups: the subacromial erosion group (18 patients) and the normal group (18 patients). Differences in multiple anatomical parameters between the two groups were measured and compared.

Results

The distal clavicle–acromion angle was significantly larger in the subacromial erosion group (mean, 51.37° ± 5.59°) than in the normal group (mean, 44.20° ± 3.83°), as was the distal clavicle–coronal angle (mean, 25.44° ± 2.51° vs. 21.67° ± 4.06°, respectively). The thickness of the acromion was significantly different between men and women (9.72 ± 1.13 vs. 8.16 ± 1.89 mm, respectively).

Conclusion

The results of this study indicate that the distal clavicle–acromion angle and distal clavicle–coronal angle are closely correlated with the occurrence of subacromial erosion after hook plate fixation.

BIOMECHANICAL EFFECT OF DIFFERENT LAG SCREW LENGTHS WITH DIFFERENT BARREL LENGTHS IN DYNAMIC HIP SCREW SYSTEM: A FINITE ELEMENT ANALYSIS STUDY

The dynamic hip screw (DHS) system is commonly used to treat intertrochanteric fracture of the hip joint. Breakage of the lag screw was noted in clinical practice and the length of lag screw as well as the length of the side plate in the DHS system appeared to play a role in the risk of breakage. Thus, the aim of this study was to investigate the biomechanical effect of different lag screw lengths and barrel plate lengths in the DHS implant system by finite element analysis (FEA). Four FEA simulation models were created according to different lengths of lag screw (79[Formula: see text]mm and 63[Formula: see text]mm) and different lengths of barrel side plate (43[Formula: see text]mm and 37[Formula: see text]mm). The von Mises stress was used as the observation indicator. The results showed that the maximum tensile stress on the long lag screw was slightly greater than that of the shorter lag screw. Use of a shorter barrel side plate may also cause high stress between the lag screw and the barrel side plate. This finding provides biomechanical reference data that may be of value to orthopedic surgeons with respect to choice of implant size and length in the treatment of intertrochanteric fracture with a DHS system to prevent complications such as implant failure caused by broken lag screws.

INFLUENCE OF THREE DIFFERENT CURVATURES FLEX-FOOT PROSTHESIS WHILE SINGLE-LEG STANDING OR RUNNING: A FINITE ELEMENT ANALYSIS STUDY

Flex foot device was one of the most common prosthesis for the athletes with the transtibial amputation on the recent market. Thus, the results of investigation with biomechanics on the flex foot would be a considerable impact on the performance of disabled athletes wearing the flex foots. This study was designed to investigate the biomechanical condition of the flex foot prosthesis with different curvatures while standing and running by finite element analysis. This study demonstrated finite element models of flex foot established with three different curvatures 20[Formula: see text] (small bending), 35[Formula: see text] (medium bending) and 50[Formula: see text] (big bending). Besides, it simulates and investigates the condition of flex foot while a person is wearing it with single-leg standing or running. The evaluation indices were selected as von Mises stress and displacements at top of socket surface. The results show that the big-bending flex foot generated the higher stress and the larger deformed displacement. Without exceeding the material tolerance of the flex foot, the larger displacement of big-bending flex foot could generate more energy, which possessed larger resilient potential energy and enabled the athletes to have better performance after using the flex foot. As a result, due to its beneficial property of energy storage and return, the large-bending flex foot user could have better effect. In the future, more innovative designs of the flex foot prosthesis can be laid out with the reference of the result in this study.

Biomechanical analysis of clavicle hook plate implantation with different hook angles in the acromioclavicular joint

PURPOSE

A clavicle hook plate is a simple and effective method for treating acromioclavicular dislocation and distal clavicle fractures. However, subacromial osteolysis and peri-implant fractures are complicated for surgeons to manage. This study uses finite element analysis (FEA) to investigate the post-implantation biomechanics of clavicle hook plates with different hook angles.

METHODS

This FEA study constructed a model with a clavicle, acromion, clavicle hook plate, and screws to simulate the implantation of clavicle hook plates at different hook angles (90°, 95°, 100°, 105°, and 110°) for treating acromioclavicular joint dislocations. This study investigated the biomechanics of the acromion, clavicle, hook plate, and screws.

RESULTS

A smaller hook angle increases the stress on the middle third of the clavicle. A larger hook angle increases the force exerted by the clavicle hook plate on the acromion. The screw at the most medial position on the plate generated the highest stress. The highest stress on the implanted clavicle hook plate was on the turning corner of the hook.

CONCLUSIONS

A clavicle hook plate with different hook angles may induce different biomechanical behaviors in the clavicle and acromion. Orthopedic surgeons must select a suitable clavicle hook plate based on the anatomical structure of each patient.

Clinical and radiological results on the fixation of Neer type 2 distal clavicle fractures with a hook plate

Objective

The aim of this study was to analyze the clinical and functional results of hook plate fixation in Neer type 2 distal clavicle fractures.

Methods

We retrospectively analyzed 16 patients (11 males, 5 females) who were diagnosed with Neer type 2 distal clavicle fractures and treated with hook plate fixation between 2013 and 2014. Mean age was 38 (range: 27–61), and mean follow-up time was 14.3 (range: 12–18) months. Complications seen on radiographs were implant failure and subacromial osteolysis. The clinical results were evaluated with modified UCLA (University of California Los Angeles) scoring system.

Results

Bone union was achieved in all patients at the end of the first 4 months. Mean modified UCLA score was 32.75 (range 31–35). In 12 patients (68%), the implants had to be removed due to complications. After removal, the complaints regressed and shoulders' range of motion increased.

Conclusion

Clinical and radiological results on the fixation of Neer type 2 distal clavicle fractures with a hook plate are good in terms of fracture union and function. The major disadvantage of the method was the requirement of early implant removal due to the hardware related complications and good results can be achieved only after plate removal. Optimizing the length of hook plate may lower the rate of complications.

Level of evidence

Level IV, Therapeutic study.

Anatomical principles for minimally invasive reconstruction of the acromioclavicular joint with anchors

PURPOSE

The aim of this study was to evaluate the outcome of a minimally invasive surgical technique for the treatment of patients with acromioclavicular joint dislocation.

METHODS

Sixteen patients with complete acromioclavicular joint dislocation were enrolled in this study. All patients were asked to follow the less active rehabilitation protocol post-operatively. Computed tomography with 3-D reconstruction of the injured shoulder was performed on each patient post operatively for the assessment of the accuracy of the suture anchor placement in the coracoid process and the reduction of the acromioclavicular joint. Radiographs of Zanca view and axillary view of both shoulders were taken for evaluating the maintenance of the acromioclavicular joint reduction at each follow-up visit. The Constant shoulder score was used for function assessment at the final follow-up.

RESULTS

Twenty seven of the 32 anchors implanted in the coracoid process met the criteria of good position. One patient developed complete loss of reduction and another had partial loss of reduction in the anteroposterior plane. For the other 14 patients, the mean Constant score was 90 (range, 82-95). For the patients with partial and complete loss of reduction, the Constant score were 92 and 76 respectively. All of them got nearly normal range of motion of the shoulders and restored to pre-operative life and works.

CONCLUSION

With this minimally invasive approach and limited exposure of the coracoid, a surgeon can place the suture anchors at the anatomical insertions of the coracoclavicular ligament and allow the dislocated joint reduced and maintained well.

LEVEL OF EVIDENCE

Level IV, Case series; therapeutic study.

Biomechanical Analysis of Implanted Clavicle Hook Plates With Different Implant Depths and Materials in the Acromioclavicular Joint: A Finite Element Analysis Study

Clinical implantation of clavicle hook plates is often used as a treatment for acromioclavicular joint dislocation. However, it is not uncommon to find patients that have developed acromion osteolysis or had peri-implant fracture after hook plate fixation. With the aim of preventing complications or fixation failure caused by implantation of inappropriate clavicle hook plates, the present study investigated the biomechanics of clavicle hook plates made of different materials and with different hook depths in treating acromioclavicular joint dislocation, using finite element analysis (FEA). This study established four parts using computer models: the clavicle, acromion, clavicle hook plate, and screws, and these established models were used for FEA. Moreover, implantations of clavicle hook plates made of different materials (stainless steel and titanium alloy) and with different depths (12, 15, and 18 mm) in patients with acromioclavicular joint dislocation were simulated in the biomechanical analysis. The results indicate that deeper implantation of the clavicle hook plate reduces stress on the clavicle, and also reduces the force applied to the acromion by the clavicle hook plate. Even though a clavicle hook plate made of titanium alloy (a material with a lower Young's modulus) reduces the force applied to the acromion by the clavicle hook plate, slightly higher stress on the clavicle may occur. The results obtained in this study provide a better reference for orthopedic surgeons in choosing different clavicle hook plates for surgery.