Enhanced biomechanical stiffness with large pins in the operative treatment of pediatric supracondylar humerus fractures

Analysis of the location and trajectory of the Kirschner wires in the fixation of extension-type supracondylar fracture of the humerus by 3D computational simulation

BACKGROUND

Closed reduction and percutaneous pinning is still a preference for the treatment of supracondylar humerus fractures in children. However, no reports have shown the pin trajectory and the characteristics of the entry point so far. So we established a computational simulation model of the elbow to observe the trajectory of pinning for supracondylar humerus fractures.

METHODS

We reconstructed an adult elbow computationally and simulated pin placement through lateral and medial pinning. Pin trajectories were traced after placement and after the addition of the skin profile; the relative entry points of the pins were determined. We used the center of the dorsal olecranon inflection as an anatomic reference for the entry points of lateral pinning. Four quadrants were established based on the center of the dorsal olecranon inflection: upper medial quadrant, upper lateral quadrant, lower medial quadrant, and lower lateral quadrant (LLQ).

RESULTS

The maximum angle of pinning through the lateral column was 64° ± 3°. The minimum angles of pinning through the lateral column and middle column were 37° ± 3° and 20° ± 2°, respectively. The range of safe angle pinning through the medial column was between 18° ± 2° and 57° ± 3° to avoid penetration of the olecranon fossa and the cortex of the medial column. The entry points of lateral pinning were within the lateral half of the LLQ, and the lateral one-third of the LLQ contained all entry points of the pins through the lateral column and minor points of the pins through the middle column. The exit points of the medial pinning were within the lateral fringe of the metaphyseal-diaphyseal junction region; entering from the inferior two-thirds of the medial epicondyle could lead to the exit points in the proximal half of the metaphyseal-diaphyseal junction region laterally.

DISCUSSION

For lateral pinning, the entry points would be within the lateral half of the LLQ. For the pins through the lateral column, the entry points should be within the lateral one-third of the LLQ. For medial pinning, entering from the inferior two-thirds of the medial epicondyle would lead to a more proximal exit.

The effect of different pin configurations on cyclic stability in pediatric proximal humerus fracture fixation: A Sawbones model study

BACKGROUND

In sawbones with proximal humerus fracture model, three different fixation configurations, Parallel-Straight K-wires, Cross-Straight K-wires and Palm-Tree Method, were biomechanically compared.

METHODS

A total of 36 anatomical pediatric humerus sawbones models were used. They were divided into three equal groups; parallel fixation with straight K-wires (Group PS), cross fixation with straight K-wires (Group CS), and Palm-Tree Method (Group PT). Models were tested in abduction and torsional at a speed of 0.5 mm/s and a 0-5 mm displacement range. Loading (N) and Stiffness (N/mm) data were calculated and compared statistically.

RESULTS

Group PS was significantly higher than the other two groups in abduction bending cyclic load values (P<0.001). It was also significantly higher in Group CS than in Group PT (P < 0.001). No significant differences were detected between the three different fixation groups' cyclic torsional load values (p < 0.05).

CONCLUSION

The parallel configuration with straight K-wires will provide a more stable fixation than the cross configuration with straight or Palm-Tree Method in pediatric proximal humeral sawbones fracture modeling.

Sagittal plane alignment affects the strength of pin fixation in supracondylar humerus fractures

Closed reduction with percutaneous pin fixation is commonly used to treat pediatric supracondylar humerus fractures. Various pin configurations of varying biomechanical strength have been described. However, to our knowledge, no biomechanical study has focused on pin alignment in the sagittal plane. Our goal was to compare the stability of fixation using 3 different pin constructs: 3 lateral pins diverging in the coronal plane but parallel in the sagittal plane (3LDP), 3 lateral pins diverging in the coronal and sagittal planes (3LDD), and 2 crossed pins (1 medial and 1 lateral).Transverse fractures were made through the olecranon fossa of 48 synthetic humeri, which were then reduced and pinned in the 3LDP, 3LDD, and crossed-pin configurations (16 specimens per group) using 1.6-mm Kirschner wires. The sagittal plane pin spread was significantly greater in the 3LDD group than in the 3LDP group, whereas we found no difference in the coronal plane. Sagittal extension testing was performed from 0° to 20° at 1°/s for 10 cycles using a mechanical torque stand. The torque required to extend the distal fragment 20° from neutral was compared between groups using one-way analysis of variance with multiple comparison post-hoc analysis. P values ≤.05 were considered significant.The 3LDD configuration was more stable than the 3LDP and crossed-pin configurations. The mean torque required to displace the pinned fractures was 5.7 Nm in the 3LDD group versus 4.1 Nm in the 3LDP group and 3.7 Nm in the crossed-pin group (both, P < .01). We found no difference in stability between the 3LDP and crossed-pin groups (P = .45).In a synthetic biomechanical model of supracondylar humerus fracture, sagittal alignment influenced pin construct stability, and greater pin spread in the sagittal plane increased construct stability when using 3 lateral pins. The lateral pin configurations were superior in stability to the crossed-pin configuration.Level of Evidence: Level V.

Management of acute paediatric fractures treated surgically in the UK: a cross-sectional study

INTRODUCTION

The epidemiology of acute paediatric orthopaedic trauma managed surgically across the NHS is poorly described. Compliance against national standards for the management of supracondylar humeral fractures is also unknown at a national level.

METHODS

Collaborators in 129 NHS hospitals prospectively collected data on surgically managed acute paediatric orthopaedic trauma cases. Data were collected over a seven-day period and included demographics, injury characteristics, operative details and timing of surgery. A national audit was also undertaken to evaluate compliance with the British Orthopaedic Association Standards for Trauma Guideline 11: Supracondylar Fractures of the Humerus in Children.

RESULTS

Data were captured on 770 surgically treated cases. The three most common injuries were forearm fractures of both bones (n = 235), distal radius fractures (n = 194) and supracondylar elbow fractures (n = 89). The mode day of injury was Friday (n = 136) and the mode day of surgery was Saturday (n = 138). 88% of supracondylar fractures received surgery on the day of presentation or the following day. Only 14% of supracondylar fractures were treated surgically after 8pm; 33/89 used 2.0mm Kirschner wires, 38/89 used 1.6mm wires and 2/89 used 1.2mm wires.

CONCLUSION

Forearm fractures of both bones, distal radius fractures and supracondylar humeral fractures were the three most common injuries treated surgically. There is wide variation in compliance against national standards in the management of supracondylar humeral fractures with 88% undertaking surgery on the day of or the day following presentation but only 37% using the recommended 2.0mm Kirschner wires.

Closed Reduction and Percutaneous Pinning in the Treatment of Humeral Distal Metaphyseal-Diaphyseal Junction Fractures in Children: A Technique Note and Preliminary Results

Objective: The metaphyseal-diaphyseal junction (MDJ) fracture is an uncommon but problematic type of fracture occurring at the distal humerus in children. Closed reduction and fixation are challenging and may not be possible with the conventional reduction maneuver utilized in supracondylar fractures. The purpose of this study was to evaluate a novel closed reduction and percutaneous pinning (CRPP) technique for the treatment of these fractures. Methods: We retrospectively evaluated 14 children (8 boys and 6 girls) who underwent closed reduction and percutaneous fixation for the treatment of MDJ fractures. Six children who underwent treatment with a novel CRPP technique were enrolled as Group A. Eight children underwent the conventional reduction maneuver utilized in supracondylar fracture and were enrolled as Group B. Clinical and radiographic outcomes in the two groups were then compared. Results: In Group A, all six MDJ fractures were treated successfully with the novel CRPP technique without the need for open procedures or re-operation. No complications such as pin-site infection or iatrogenic nerve injury were found in this group. In group B, five of the eight fractures were treated successfully with the conventional CRPP technique; three fractures needed open reduction, and one of them had further surgery because of the loss of fixation. Children with successful CRPP in each group were included to compare the efficacy of the novel CRPP technique. The average duration of the surgery in Group A was significantly shorter than that in Group B (p < 0.001). At last follow-up, both groups obtained satisfactory clinical and radiographic outcomes. Conclusion: MDJ fractures can be reduced successfully and fixed stably via a novel CRPP technique, and laborious and frustrating attempts at closed reduction and further open reduction can be avoided.

Fracture obliquity is a predictor for loss of reduction in supracondylar humeral fractures in older children

Supracondylar humeral fractures in older children have different biomechanical characteristics and surgical outcomes when compared to the same fractures in younger children. We aimed to analyze the fracture's architecture in a large group of older children and investigate the correlation between patients' variables, fracture patterns, fixation techniques and the rate of loss of reduction (LOR). A retrospective review study was conducted. We collected the records of 240 consecutive patients aged 8-14 years that sustained Gartland type 2/3 supracondylar humeral fractures between 2004 and 2014 and were operated at our hospital. We excluded patients with intra-articular or pathological fractures. Following the radiographical analysis and chart review, we conducted a multivariable regression analysis. Fracture obliquity on the sagittal plane ( > 20°) occurred in 33% of the cases and was found to be the only factor related to LOR (P = 0.01). Gartland type 3 fractures and more than two lateral pin configuration did not correlate to fixation failure (P = 0.69 and 0.14, respectively). The incidence of flexion-type fractures (5.8%) was found to be higher than in the total pediatric population. The sagittal oblique supracondylar humeral fracture is common and is related to fixation instability and LOR. This pattern needs to be considered when investigating different pin configurations, complication rates, and biomechanical properties. Subclassifying Gartland type 2/3 supracondylar humeral fractures as 'oblique' or 'transverse' might offer more comprehensive information about the anticipated operative results, lead to applying more stable pin constructs to these fractures and allow improved outcomes following surgical fixation.

Multicentre collaborative cohort study of the use of Kirschner wires for the management of supracondylar fractures in children

PURPOSE

Supracondylar fractures of the humerus cause significant morbidity in children. Nerve damage and loss of fracture reduction are common recognised complications in patients with this injury. Uncertainty surrounds the optimal Kirschner wire configuration and diameter for closed reduction and pinning of these fractures. This study describes current practice and examined the association between wire configuration or diameter and outcomes (clinical and radiological) in the operative management of paediatric supracondylar fractures.

METHODS

Children presenting with Gartland II or III supracondylar fractures at five hospitals in south-west England were eligible for inclusion. Collaborators scrutinised paper and electronic case notes. Outcome measures were maintenance of reduction and iatrogenic nerve injury.

RESULTS

Altogether 209 patients were eligible for inclusion: 15.7% had a documented neurological deficit at presentation; 3.9% who were neurologically intact at presentation sustained a new deficit caused by treatment and 13.4% experienced a clinically significant loss of reduction following fixation. Maintenance of reduction was significantly better in patients treated specifically with crossed ×3 Kirschner wire configuration compared to all other configurations. The incidence of iatrogenic nerve injury was not significantly different between groups treated with different wire configurations.

CONCLUSION

We present a large multicentre cohort study showing that crossed ×3 Kirschner wires are associated with better maintenance of reduction than crossed ×2 or lateral entry wires. Greater numbers would be required to properly investigate nerve injury relating to operative management of supracondylar fractures. We found significant variations in practice and compliance with the British Orthopaedic Association Standard for Trauma (BOAST) 11 guidelines.

Biomechanical Assessment of Torsional Stiffness in a Supracondylar Humerus Fracture Model

BACKGROUND

We assessed the effect on the torsional stability by different pin diameters and varied pin configurations in a biomechanical supracondylar humerus fracture model.

METHODS

After scanning a model of a pediatric humerus, the image was imported into software. Variable pin trajectories were planned. Acrylonitrile butadiene styrene plastic models were 3-dimensionally printed with predetermined pin trajectories. Models were osteotomized and potted with a polyurethane resin. Five-pin configurations were designed to test coronal and sagittal patterns of pin placement. Each included 3 lateral pins and a medial pin. Pin diameters of 1.6, 2.0, and 2.4 mm were tested in all configurations. Three models for each pin diameter/configuration were tested to ensure uniformity. Stability of the construct was tested to determine the torque needed to deflect the osteotomy 10 degrees in internal/external rotation. Each model was tested 3 times.

RESULTS

In all models/configurations, the 2.4 mm pin diameter was statistically stiffer than 1.6 mm diameter pins; this lost statistical significance in certain patterns when comparing 2.0- and 2.4-mm pins. When comparing a divergent to a parallel configuration in the coronal plane, there was no significant difference in stability when pin diameter or number were controlled. The convergent pin configuration was, in general, the least stable pattern. Use of a medial pin conferred statistically significant stiffness throughout most models as demonstrated with pin deletion. Use of 2 pins was significantly less stiff than most 3-pin models.

CONCLUSIONS

Larger pin diameters confer greater stiffness among all patterns. The use of 3 lateral and 1 medial pin was not statistically different than 2 lateral and 1 medial pin in our models. Both patterns were stiffer than 3 lateral pins only or other fewer pin constructs. The alignment of pins in the sagittal plane did not affect overall construct stiffness.

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.

Pediatric Orthopedic Trauma: An Evidence-Based Approach

The management of pediatric fractures has evolved over the past several decades, and many injuries that were previously being managed nonoperatively are now being treated surgically. The American Academy of Orthopaedic Surgeons has developed clinical guidelines to help guide decision making and streamline patient care for certain injuries, but many topics remain controversial. This article analyzes the evidence regarding management of 5 of the most common and controversial injuries in pediatric orthopedics today.

Pediatric Supracondylar Fractures: Variation in Fracture Patterns and the Biomechanical Effects of Pin Configuration

BACKGROUND

Transverse pediatric supracondylar fractures through the midolecranon fossa are frequently encountered and modeled in biomechanical studies. Our objective is to investigate the optimal pin configurations for low, sagittal oblique, and high fracture varieties that have not been previously investigated.

METHODS

A total of 100 synthetic composite pediatric humeri were tested. Three groups of 30 were used to simulate 1 of 3 fracture variations. Subgroups of 10 were stabilized with 2 lateral pins (2LP), 3 lateral pins (3LP), or cross K-wires (XP). The 90 fracture and 10 intact models were tested for anterior posterior (AP), medial lateral (ML), and rotational stiffness.

RESULTS

In low fractures, AP, ML, and rotational stiffness of 2LP and 3LP were similar to intact. ML stiffness was less using XP. AP and ML stiffness of 2LP and 3LP were significantly greater than XP.In oblique fractures, AP, ML, and rotational stiffness of 2LP was similar to intact but 3LP was significantly less. AP and ML stiffness of XP was significantly less. 2LP demonstrated greater AP, ML, and rotational stiffness than 3LP and XP.In high fractures, all configurations demonstrated significantly less rotational stiffness than intact and AP stiffness similar to intact. Rotational stiffness of 3LP was greater than 2LP and XP. AP and ML stiffness were not different among configurations.

CONCLUSIONS

2LP are stiffer than 3LP and XP for sagittal oblique fractures. 2LP and 3LP stiffness were similar in low transverse fractures, and both constructs demonstrated greater stiffness than XP configuration. 3LP is preferable for high transverse fractures. XP were never stiffer than the lateral only constructs in any of the patterns tested.

CLINICAL RELEVANCE

All-lateral pin constructs may provide adequate stiffness to maintain reduction of low transverse, sagittal oblique, and high transverse patterns of pediatric supracondylar humerus fractures without risk of injury to the ulnar nerve.

Increased pin diameter improves torsional stability in supracondylar humerus fractures: an experimental study

BACKGROUND

Pediatric supracondylar humerus fractures are the most common elbow fractures seen in children, and account for 16 % of all pediatric fractures. Closed reduction and percutaneous pin fixation is the current treatment technique of choice for displaced supracondylar fractures of the distal humerus in children. The purpose of this study was to determine whether pin diameter affects the torsional strength of supracondylar humerus fractures treated by closed reduction and pin fixation.

METHODS

Pediatric sawbone humeri simulating a Gartland type III fracture were utilized. Four different pin configurations were compared. Specimens were subjected to a torsional load producing internal rotation of the distal fragment. The stability provided by 1.25- and 1.6-mm pins was compared.

RESULTS

The amount of torque required to produce 15° and 25° of rotation was greater using larger diameter pins in all models tested. The two lateral and one medial large pin (1.6 mm) configuration required the highest amount of torque to produce both 15° and 25° of rotation.

CONCLUSIONS

In a synthetic pediatric humerus model of supracondylar humerus fractures, larger diameter pins (1.6 mm) provided increased stability compared with small diameter pins (1.25 mm). Fixation using larger diameter pins created a stronger construct and improved the strength of fixation.

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

BACKGROUND

Currently, closed reduction and percutaneous pinning are considered the treatment of choice for displaced supracondylar humerus fractures. However, indications exist for the use of external fixation with Schanz screws. In this in vitro study, we evaluate the biomechanical properties of a new variation for external fixation and compare them to an established construct.

METHODS

Twenty distal cadaver humeri (10 pairs) were allocated to 2 groups. The humeri of the first group were fixed by an external fixator consisting of Schanz screws and an oblique K-wire inserted from the distal radial cortex of the humerus, those of the second group were fixed by a new variation with the oblique K-wire inserted from the distal ulnar cortex of the humerus. Displacement and stiffness in static loading in internal and external rotation, as well as in extension and flexion were evaluated and compared.

FINDINGS

The variation of the external fixator of the second group proved to be statistically significantly superior to the variation of the first group in internal rotation loading (p>0.05). In sagittal loading conditions and external rotation loading, the variations were equally stable (p>0.05). There was no significant effect of the samples' bone density on displacement and stiffness values in any direction of loading.

INTERPRETATION

In cases of pediatric supracondylar humerus fractures when an external fixator is used for osteosynthesis, the insertion of an additional ulnarly inserted anti-rotation K-wire should be preferred to a radially inserted one as it reduces secondary displacement of the distal fragment.

Stiffness of various pin configurations for pediatric supracondylar humeral fracture: a systematic review on biomechanical studies

To compare the biomechanical stability of various pin configurations for pediatric supracondylar humeral fractures under varus, internal rotation, and extension conditions. After electronic retrieval, 11 biomechanical studies were included. Stiffness values of pin configurations under different loading conditions were extracted and pooled. There were no statistically significant differences between two cross pins and two divergent lateral pins on the basis of the 'Hamdi method' (P=0.249-0.737). An additional pin did not strengthen two-pin construct (P=0.124-0.367), but better stabilized fractures with medial comminution (P<0.01). Isolated lateral pins are preferable because of a better balance of a lower risk of nerve injury and comparable fixation strength. Limitations such as differences in experimental setup among recruited studies and small sample size may compromise the methodologic power of this study.