Biomechanical comparison of different external fixator configurations for stabilization of supracondylar humerus fractures in children

Locking plate versus K-wires and cast fixation in lateral closing-wedge osteotomy for cubitus varus deformity

Background

The aim of this study was to assess the clinical and radiographic outcomes of cubitus varus treatments based on different fixation methods: Locking plate vs. Kirschner-wires (K-wires) and cast fixation.

Methods

This retrospective study of 28 patients was performed in lateral-wedge osteotomy for cubitus varus deformity in our hospital from July 2018 to July 2020. 14 patients in group A were treated by locking plate after lateral closing-wedge osteotomy, whereas other 14 patients were treated by K-wires in group B. We measured the bony union and carrying angle. The clinical and radiographic outcomes were assessed according to the Bellemore criteria.

Results

No nonunion, neurovascular injury or myositis ossificans was noted at follow-up. In group A, 1 patient with lateral condylar prominence was found. In group B, 2 patients with pinning site infection were treated successfully with oral antibiotics and 2 patients needed revision surgery for residual varus. According to the Bellemore criteria, statistically significant difference was noted between the two groups (P = 0.0458). In the present study, no statistically significant difference was noted in the length of incision and operation time between the 2 groups (P > 0.05). However, the postoperative carrying angle was significantly different at final follow-up between the 2 groups (P < 0.01).

Conclusions

Compared with K-wires and cast fixation, we recommend the wedge osteotomy with lateral locking plate to treat the cubitus varus deformity because locking plate could achieve better functional and cosmetic results and stabilize the distal humerus rigidly.

Is methyl methacrylate fixator reliable for the treatment of gartland type IV supracondylar fractures?

Background

In childhood supracondylar fractures of the humerus, fixation with percutaneous Kirschner wire is the standard treatment. In the case of irreducible-unstable fractures, these can be defined as fractures in which reduction is not well-achieved or in which fixation cannot be achieved with the K-wire. Intraoperative management of these types of fractures may be difficult. Treatment with a methyl methacrylate fixator consisting of K-wire and methyl methacrylate cement, as defined by the senior author of the article, may be a good option for Gartland type IV supracondylar humeral fractures where the fracture is unstable in flexion and extension due to complete periosteal tearing.

Materials and Methods

The short-term and mid-term results of 27 patients between the ages of 4-12 with Gartland type IV supracondylar fracture of the humerus treated with methyl methacrylate fixation were reviewed. The patients were scored in terms of function and cosmetic satisfaction.

Results

A total of 19 of the 27 patients treated with the methyl methacrylate fixator had full elbow motion function and rated the outcome of the treatment as excellent, which was judged by orthopedic surgeons on the basis of Flynn's criteria. Six patients had nearly full elbow motion and evaluated their recovery outcome as good. Two patients reported nearly full range of motion (ROM) and evaluated the method as moderate in terms of treatment.

Discussion

Treatment with the methyl methacrylate fixation method is an inexpensive method that allows early joint mobilization, provides strong biomechanical stability, ensures good outcomes, and should be considered in the treatment of irreducible and unstable supracondylar fractures of the humerus.

Comparative evaluation of pinning and cast fixation vs. external fixation after lateral closing-wedge osteotomy for cubitus varus in children

BACKGROUND

Cubitus varus has been regarded as a poor functional and cosmetic consequence of supracondylar humerus fracture in children. The aim of this study was to assess the clinical and radiologic outcomes of cubitus varus treatments based on fixation methods: Kirschner (K)-wire and cast fixation or external fixation.

METHODS

Forty consecutive patients with cubitus varus secondary to supracondylar fractures were retrospectively enrolled between October 2015 and December 2018. Following lateral closing-wedge osteotomy, those undergoing K-wire and cast fixation were included in group A (n = 21) and those who were treated with external fixation comprised group B (n = 19). We measured the bony union, elbow joint range of motion, and carrying angle. The clinical and radiographic results were assessed according to the Bellemore criteria.

RESULTS

No significant difference was found between the 2 groups in terms of age, gender, operation duration, union time, and postoperative elbow range of motion (P > .05). A significant difference was noted, however, in postoperative carrying angle and results according to Bellemore criteria in group B (P < .05). No nonunion, myositis ossificans, or neurovascular injury was found at follow-up in the 2 groups. In group A, revision surgery was needed for residual varus in 1 patient and lateral condylar prominence was found in 2 patients. In group B, a superficial pin-site infection occurred in 2 patients, who were treated successfully with oral antibiotics.

CONCLUSIONS

Both K-wire and external fixation after lateral closing-wedge osteotomy are reliable and effective for the treatment of cubitus varus in children. Compared with the K-wire method, external fixation achieves better functional and cosmetic results with a shorter learning curve.

Treatment of Pediatric Intercondylar Humerus Fracture With External Fixation and Percutaneous Pinning After Closed Reduction

BACKGROUND

It is uncommon for young children to suffer an intercondylar fracture of the distal humerus. Although many approaches have been described to manage, there is no specific and accepted treatment protocol for such fracture patterns. This study aimed to identify the incidence of intercondylar fracture of the distal humerus in the pediatric population and report the clinical outcome of external fixation and percutaneous pinning in such injury patterns.

METHODS

Pediatric patients under the age of 14 years who had an intercondylar fracture of the distal humerus treated with external fixation and percutaneous pinning between January 2013 and December 2018 at the author's Wuhan Union Hospital were retrospectively evaluated. The detailed baseline information of the patients, operating time, time to union time, and carrying angle difference (CAD) of the injured extremity were collected. During the follow-up visit, clinical results were evaluated using the Mayo Elbow Performance Score (MEPS) and the Flynn criteria.

RESULTS

A total of eight patients (2 women and 6 men) with an average age of 8 years (5-12 years) who had an intercondylar fracture of the distal humerus (1 C2 and 7 C1) were included. All the patients achieved union, and the average MEPS score was 95 points 24 months after the surgery.

CONCLUSION

The intercondylar fracture of the distal humerus in children is rare, and closed reduction and external fixation is a viable treatment option, especially for the C1 type of fracture pattern.

An engineering review of external fixators

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Mechanical stability plays a key role in the effectiveness of external fixators.

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Strength and stiffness are the main factors which contributes towards stability.

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Modified configurations of linear, circular and hybrid fixators are investigated.

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Light weight composite materials are gradually replacing traditional metallic alloys.

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Existing research gaps in further optimizing external fixators are identified.

External Fixators are a common technique used to treat a variety of issues related to bones, predominantly due to its non-intrusive nature and versatility in terms of form and materials. While it is mainly used to treat open fractures, its other uses include limb lengthening, deformity correction, bone grafting, compression of non-unions and stabilization of dislocations. Its earliest use dates as far back as 400 BCE and has undergone significant improvements, focusing on both customization and optimization. These two aspects highlight the significance of complementing the orthopaedic requirements with engineering knowledge and its applications. Hence, this review paper aims to conduct an examination of recent developments of external fixators with a special focus on its structure, the usage of materials and biomechanical investigations using experimental and numerical techniques. The paper presents the existing level of engineering knowledge with regards to these aspects and identifies research gaps, which can improve the quality of the commonly used external fixators.

Lateral entry pins and Slongo's external fixation: which method is more ideal for older children with supracondylar humeral fractures?

Objective

The standard surgical treatment for supracondylar humeral fractures in children is closed reduction and percutaneous pinning. Given the need for greater fixation strength and higher risk of joint stiffness for children older than 8 years, external fixation is often performed for treating supracondylar humeral fractures in older children. The aim of this study was to compare the efficacy of lateral entry pins and Slongo’s external fixation for treating supracondylar humeral fractures in older children.

Methods

Children older than 8 years who underwent surgery for supracondylar humeral fractures at our hospital for surgery from January 2016 to December 2020 are to be retrospectively assessed. One group (n = 36) underwent internal fixation and percutaneous pinning with three lateral Kirschner wires, and the other group (n = 32) underwent Slongo’s external fixator surgery. The demographic data, operation duration, number of fluoroscopies, and fracture healing time were compared between both groups. The elbow joint function was evaluated 6 months after the surgery on the basis of fracture healing time, lifting angle, elbow joint range of motion (ROM), and Flynn score. The incidence of postoperative complications was also recorded.

Results

There was no significant difference between the two patient groups in terms of the demographic parameters. Compared to external fixation surgery, Kirschner wire surgery required shorter duration and fewer fluoroscopies (P < 0.05). Nevertheless, the fracture healing time was significantly less (P < 0.05), and the elbow ROM and Flynn scores were higher in the external fixator group compared to the Kirschner wire fixation group (P < 0.05). There was one case of secondary fracture displacement in the Kirschner wire group and one of pin tract infection in the external fixator group. No other iatrogenic injuries or complications were observed.

Conclusion

Maybe Slongo’s external fixator is a suitable alternative treatment option for supracondylar humeral fractures in children older than 8 years since it can achieve better fixation strength and early restoration of elbow joint movement with a lower risk of joint stiffness.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-021-02541-z.

Surgical management of delayed Gartland type III supracondylar humeral fractures in children: A retrospective comparison of radial external fixator and crossed pinning

Radial external fixator has been proposed to treat delayed irreducible Gartland type III supracondylar humeral fracture, and this study aims to compare its effects with crossed pinning in a retrospective fashion. Delayed supracondylar humeral fracture is defined as more than 72 hours after injury, 2 or more than 2 times failed attempts of closed reduction can be deemed as irreducible fracture.Between January 2010 and January 2017, patients of Gartland type III supracondylar fractures of the humerus receiving surgery were all selected and reviewed. Overall, 39 patients fitting the inclusion criteria were chosen for the External Fixator Group and patients for control group of crossed pinning with matched age, sex, and clinical parameters (fracture location, injured side, and fracture type) were selected from the database. Surgery duration, number of intraoperative X-ray images, incidence of ulnar nerve injury, postoperative redisplacement, and function of the elbow joint were recorded and analyzed.In this study, 39 patients treated with radial external fixator had significantly shorter surgery duration, fewer intraoperative X-ray images, and lower incidence of ulnar nerve injury, and postoperative redisplacement than those receiving crossed pinning. Patients in 2 groups displayed similar range of motion for elbow joint at follow-up.Radial external fixator is an effective and safe method to treat Gartland type III supracondylar fractures that were diagnosed late.

Mechanical stability study of three techniques used in the fixation of transverse and oblique metaphyseal-diaphyseal junction fractures of the distal humerus in children: a finite element analysis

Background

Management of distal humerus metaphyseal-diaphyseal junction (MDJ) region fractures can be very challenging mainly because of the higher location and characteristics of the fracture lines. Loss of reduction is relatively higher in MDJ fractures treated with classical supracondylar humerus fractures (SHFs) fixation techniques.

Methods

Three different fracture patterns including transverse, medial oblique and lateral oblique fractures were computationally simulated in the coronal plane in the distal MDJ region of a pediatric humerus and fixated with Kirschner Wires (K-wires), elastic stable intramedullary nails (ESIN), and lateral external fixation system (EF). Stiffness values in flexion, extension, valgus, varus, internal, and external rotations for each fixation technique were calculated.

Results

In the transverse fracture model, 3C (1-medial, 2-lateral K-wires) had the best stiffness in flexion, varus, internal, and external rotations, while 3L (3-divergent lateral K-wires) was the most stable in extension and valgus. In the medial oblique fracture model, EF had the best stiffness in flexion, extension, valgus, and varus loadings, while the best stiffness in internal and external rotations was generated by 3MC (2-medial, 1-lateral K-wires). In the lateral oblique fracture model, 3C (1-medial, 2-lateral K-wires) had the best stiffness in flexion and internal and external rotations, while ESIN had the best stiffness in extension and valgus and varus loadings.

Conclusion

The best stability against translational forces in lateral oblique, medial oblique, and transverse MDJ fractures would be provided by ESIN, EF, and K-wires, respectively. K-wires are however superior to both ESIN and EF in stabilizing all three fracture types against torsional forces, with both 2-crossed and 3-crossed K-wires having comparable stability. Depending on the fracture pattern, a 3-crossed configuration with either 2-divergent lateral and 1-medial K-wires or 2-medial and 1-lateral K-wires may offer the best stability.

Outcome evaluation of new calcium titanate schanz-screws for external fixators. First clinical results and cadaver studies

OBJECTIVE

External fixators are important for correcting length discrepancies and axis deformities in pediatric or trauma orthopedic surgery. Pin loosening is a common pitfall during therapy that can lead to pain, infection, and necessary revisions. This study aims to present clinical data using calcium titanate (CaTiO₃) Schanz screws and to measure the fixation strength.

PATIENTS AND METHODS

22 titanate screws were used for external fixators in 4 pediatric patients. Therapy was initiated to lengthen or correct axial deformities after congenital abnormalities. The maximum tightening torque was measured during implantation, and the loosening torque was measured during explantation. In addition, screws of the same type were used in a cadaver study and compared with stainless steel and hydroxyapatite-coated screws. 12 screws of each type were inserted in four tibias, and the loosening and tightening torque was documented.

RESULTS

The fixation index in the in vivo measurement showed a significant increase between screw insertion and extraction in three of the four patients. The pins were in situ for 91 to 150 days, and the torque increased significantly (P = 0.0004) from insertion to extraction. The cadaveric study showed lower extraction torques than insertion torques, as expected in this setting. The calculated fixation index was significantly higher in the CaTiO₃ group than in the other groups (P = 0.0208 vs. HA and P < 0.0001 vs. steel) and in the HA group vs. plain steel group (P = 0.0448).

CONCLUSION

The calcium titanate screws showed favorable fixation strength compared to HA and stainless steel screws and should be considered in long-term therapy of external fixation.

Pinning of supracondylar fractures in children - Strategies to avoid complications

In the pediatric population supracondylar humerus fracture (SHF) is one of the most common injuries. Diagnosis is based on inspection and conventional radiography. SHFs should be classified according to the modified Gartland classification, which guides treatment. Non-displaced or minimally displaced fractures (Gartland type-I) should be treated non-operatively, completely displaced type III fractures require closed reduction and K-wire fixation. In type-II fractures, important landmarks, such as the anterior humeral line (Roger´s line), the shaft-physeal angle (Baumann´s angle) and the shaft condylar angle should be considered to guide treatment. Special attention has to be paid for potential rotational dislocation, which is indicated by a ventral spur. In such cases surgery is necessary. The degree of acceptable extension malpositioning depends on patient´s age. In 10-year-old children fractures with a shaft condylar angle of more than 15° are still suitable for non-operative therapy. Timing for surgery is controversially discussed. Postponing surgery to the next day seems reasonable if absence of pain, intact soft tissue and normal neurovascular status are present. Neurovascular complications are not uncommon, especially in Gartland type-III fractures and in cases with additional forearm injuries. A white hand without palpable pulse needs emergency surgery, the management of the pulseless pink hand is still controversially discussed. Different operative techniques exist for surgical treatment. The golden standard is closed reduction and percutaneous K-wire pinning. Crossed pinning seems to achieve best biomechanical stability. Since ulnar nerve injuries are reported to occur in 6% after medially inserting K-wires, lateral divergent insertion of two K-wires has been compared to crossed pinning fixation in several randomized controlled trials. Meta-analyses demonstrated a higher risk for ulnar nerve injury for the crossed pinning technique while risk for loss of fixation was higher in lateral only pinning. In both cases, K-wires should be removed 3-6 weeks after surgery with consolidation of the fracture. Clinical and radiological follow-up should be carried out at 3 weeks post fracture fixation to rule out loss of reduction. If this should occur, early revision surgery has been demonstrated beneficial.

Use of external fixation for juxta-articular fractures in children

In this article, the use of external fixation in the management of juxta-articular fractures in paediatric patients is discussed. Basic principles of Ilizarov technique are described for distal radial, distal femoral, distal humeral and distal tibial fractures. Common indications for external fixation in pediatric fractures are comminuted, complicated, and/or open fractures, particularly at the distal humerus, distal radius, distal femur and distal tibia. There are several benefits of external frame fixation in these type of injuries in children. This method avoids additional injury to the growth plate as K-wires are not placed through it. It enables careful reduction without interfragmentary compression and correct anatomic alignment. There is no soft tissue dissection and periosteal blood supply is preserved. External fixation ensures primary fracture stability even in presence of comminution and high adjustment capability. Immediate joint motion and early weight-bearing are further advantages. Joint bridging is an option in severe bone loss or soft tissue injuries.

Methyl methacrylate in external fixation of supracondylar humerus fractures: An experimental study

Supracondylar humerus fractures are common fractures around the elbow. Open fractures, comminuted metaphyseal fractures and also fractures with bone loss may need to be treated with external fixators. The aim of this study is to compare two different external fixators, tubular external fixators and polymethyl methacrylate with K wires external fixators, with regard to stiffness and stability for metaphyseal-diaphyseal osteotomies of distal humerus close to the joint. Six matched pairs (24 specimens) of second-generation sawbone humerus were prepared in a standard fashion to create a metaphyseal fracture, 5 cm proximal to the distal joint line of humerus and were randomly divided into two groups of 12 specimens each. Each sawbone humerus was osteotomized transversely at the mid-olecranon fossa with a 2-mm oscillating saw to simulate a Gartland type III fracture. The osteotomy was then reduced and stabilized using two different external fixation methods: carbon tubular external fixator with Schanz screws and methyl methacrylate with multiple K wires. Three-point bending and torsion tests were performed on the specimens. Bending and torsional stiffness of specimens were obtained for the fixation methods. According to the results of the study, the methyl methacrylate group has provided higher stiffness than classical tubular fixator with Schanz screws in three-point bending test (7.79 ± 2.33 N/mm vs 3.78 ± 1.18 N/mm, p = 0.006). The methyl methacrylate group also showed better stiffness in torsion test (0.12 ± 0.042 N m/° vs 0.067 ± 0.013 N m/°, p = 0.02). We determined for the first time in literature that external fixation with methyl methacrylate was significantly superior to the classical tubular external fixator with Schanz screws with regard to stiffness and stability under three-point bending and torsional loads. Moreover, methyl methacrylate is inexpensive and easily applied.

Biomechanical analysis between Orthofix® external fixator and different K-wire configurations for pediatric supracondylar humerus fractures

Background

Closed reduction and percutaneous fixation are considered as the optional treatments for displaced supracondylar humerus fractures. However, there was no published report about the biomechanical analysis in Orthofix® external fixator. In this study, we developed a model of supracondylar humerus fractures and compared the biomechanical analysis of external fixator and different K-wires configurations in order to evaluate the stability of external fixator in supracondylar humerus fractures.

Methods

We developed an anatomic humerus model by third-generation synthetic composite, and 60 synthetic humeris were osteotomized to simulate the humeral transverse supracondylar fracture. Those fractures were reduced and fixed by external fixator or K-wires, and then biomechanical analysis was performed in extension, varus, valgus, and internal and external rotation loading. A paired-sample t test was used to evaluate the distance at the fracture site between the external fixator and K-wire configurations.

Results

During all direction loading, there was a significant statistical difference between external fixator and K-wires (P < 0.001 for all pairwise comparisons). In extension and internal rotation loading, the external fixator and three crossed K-wires had no comparable stiffness values (P = 0.572; P = 0.795), and both were significantly greater than two crossed and lateral K-wires (P < 0.05). In external rotation loading, there was no significance between the external fixator and K-wire configurations except two lateral K-wires (P > 0.05). In valgus loading, the stability of the external fixator was less than that of three crossed K-wires (P = 0.001) but was not significantly different with those of two crossed or three lateral K-wires (P = 0.126; P = 0.564). In varus loading, the stability of the external fixator was larger than those of two and three lateral K-wires (P = 0.000; P = 007).

Conclusions

External fixator could provide enough stability for pediatric supracondylar humerus fractures without the injury of the ulnar nerve. Besides, it could enhance the rotational stiffness of the construct in rotation loading to avoid the complication of cubitus varus.

A comparative biomechanical study on different fixation techniques in the management of transverse metaphyseal-diaphyseal junction fractures of the distal humerus in children

BACKGROUND

Metaphyseal-diaphyseal junction (MDJ) fractures of the distal humerus are problematic to reduce and more susceptible to post-operative complications. This biomechanical study was designed to compare Kirschner wires (KW), lateral external fixation, and elastic stable intramedullary nails (ESIN) in simulated transverse MDJ fractures of various heights.

METHOD

Sagittally oblique, transverse MDJ fractures were created in fourth-generation composite bone models at three levels: high, mid, and low fractures, respectively, and then fixed with either Kirschner wires, lateral external fixation (EF), or ESIN respectively and tested in extension, flexion, valgus, varus, internal, and external rotations.

RESULTS

In the high fractures, ESIN had better overall stiffness than the other techniques. In the mid groups, three crossed pinning (1-medial and 2-lateral pins) had the best overall stiffness, followed by two crossed pinning (1-medial and 1-lateral pins). In the low fractures, three crossed pinning was superior to all other techniques. Two crossed pinning and three -lateral pinning techniques yielded comparable stiffness in the low fracture model.

CONCLUSIONS

From a biomechanical perspective, ESIN provides the best overall stability for fractures located in the upper region of the MDJ, while percutaneous pinning is superior in stabilizing fractures of the lower region. Two lateral and one medial pins make the most stable crossed pinning construct for these fractures.