Biomechanical comparison of orthogonal versus parallel double plating systems in intraarticular distal humerus fractures

Biomechanical comparison of three internal fixation configurations for low transcondylar fractures of the distal humerus

BACKGROUND

We aimed to evaluate the biomechanical stiffness and strength of different internal fixation configurations and find suitable treatment strategies for low transcondylar fractures of the distal humerus.

METHODS AND MATERIALS

Thirty 4^th generation composite humeri were used to create low transcondylar fracture models that were fixed by orthogonal and parallel double plates as well as posterolateral plate and medial screw (PPMS) configurations (n=10 in each group) using an anatomical locking compression plate-screw system and fully threaded medial cortical screws. Posterior bending (maximum 50 N), axial loading (maximum 200 N) and internal rotation (maximum 10 N·m) were tested, in that order, for each specimen. Stiffness under different biomechanical settings among different configurations were compared. Another 18 sets of fracture models were created using these three configurations (n=6 in each group) and the load to failure under axial loading among different configurations was compared.

RESULTS

Under posterior bending, the stiffness of parallel group was higher than orthogonal group (P<0.001), and orthogonal group was higher than PPMS group (P<0.001). Under axial loading, the stiffness of parallel group was higher than orthogonal group (P=0.001) and PPMS group (P<0.001); however, the difference between orthogonal and PPMS group was not statistically significant (P>0.05). Under internal rotation, the stiffness of parallel group was higher than orthogonal group (P=0.044), and orthogonal group was higher than PPMS group (P=0.029). In failure test under axial loading, the load to failure in the orthogonal group was lower than parallel group (P=0.009) and PPMS group (P=0.021), but the difference between parallel group and PPMS group was not statistically significant (P>0.05). All specimens in orthogonal group demonstrated "distal medial failure"; most specimens had "distal medial and trochlear failure" in the parallel group; most specimens exhibited "contact failure" in the PPMS group.

CONCLUSION

For treating low transcondylar fractures, the overall stiffness and strength of the parallel configuration were superior to those of the orthogonal and PPMS configurations. Nevertheless, the PPMS configuration can provide adequate stability and stiffness comparable to double-plate configurations under axial loading. Therefore, the PPMS construct may have certain clinical value.

Length of Plates and Number of Screws for the Fixation of Distal Humerus Fractures: A Finite Element Biomechanical Study

PURPOSE

We performed a biomechanical analysis using the finite element method to assess the effects of plate length and the number of screws on construct stiffness, stress distribution, and fracture displacement in the fixation of type A2 distal humerus fractures.

METHODS

A 3-dimensional humerus model was constructed using computed tomography of a healthy man. After creating a 2-mm extra-articular fracture gap, orthogonal double-plate fixation was performed with an incremental increase in plate length and the number of screws, creating 17 fixation models. Four screws were placed in each plate's distal segment, and the number of screws was increased incrementally in the segment proximal to the fracture, starting from 2 in the medial (M) and 2 in the lateral (L) plate (M2∗L2).

RESULTS

The fifth screw proximal to the fracture in the lateral plate (L5) played an essential role in increasing stiffness under bending, axial, and torsional forces surpassing the intact bone, which may have been due to the bypassing of the stress riser area. Minimum construct stiffness was created when 5 (M3∗L2) screws were inserted into the proximal segment. For bending forces, the M4∗L2 construct was stronger than M3∗L3 (total 6 proximal screws), and M5∗L3 was stronger than M4∗L4 (total 8 proximal screws), showing higher stiffness when the plates ended at different levels. The M4∗L2 construct (6 screws) had stiffness comparable with M4∗L3, M4∗L4, and M5∗L4 during bending, showing comparable stiffness with the least instrumentation density.

CONCLUSION

Our findings suggested M3∗L5 as the optimum and M3∗L2 as the minimum construct to resist all bending, axial and torsional forces.

CLINICAL RELEVANCE

Applying the results may improve surgical techniques, decrease the rate of complications, including fixation failure and nerve injury, and optimize the time of surgery. Moreover, hardware removal is less cumbersome with fewer screws.

Intra-articular Distal Humerus Fractures: Parallel Versus Orthogonal Plating

Background: Dual-plating osteosynthesis is the standard treatment for Orthopedic Trauma Association (OTA)-type 13-C distal humerus fractures. However, optimal plate position is debated. Purpose: The purpose of this study was to evaluate dual-plate positioning following intra-articular distal humerus fracture repair by comparing outcomes between patients plated in parallel and those plated orthogonally following open-reduction, internal-fixation (ORIF) of intra-articular distal humerus fractures. Methods: All OTA-type 13-C intra-articular distal humerus fractures treated operatively at our institution over a 10-year period were reviewed. Clinical outcomes and complications were compared between those plated in parallel and those plated orthogonally. Data were analyzed using independent-samples t-tests, Mann-Whitney U tests, chi-square tests, and Fisher's exact tests. Results: A total of 69 patients met inclusion criteria. Mean follow-up among this cohort was 19.3 months; 45 (64.8%) patients had orthogonal dual plating, and 24 (35.2%) had parallel plating. Groups did not differ with respect to demographics or duration of follow-up. Clinically, there were no significant differences in time to union, elbow arc of motion at any time point, or patient Mayo Elbow Performance Index (MEPI) scores at final follow-up. Furthermore, there were no differences in complications. Conclusion: Parallel and orthogonal plating following ORIF of distal humerus fractures with modern, contoured locking compression plates had similar outcomes in this study. This study represents the largest comparative series in the literature at the time of its writing. Both techniques may be considered when deciding on dual-plating technique for treating intra-articular distal humerus fractures.

Dynamic effect of three locking plates fixated to humeral fracture based on multibody musculoskeletal model

OBJECTIVE

This study attempts to analyse the biomechanical effect of internal fixation (plated in parallel or plated vertically) on the basis of distal humeral fractures on musculoskeletal multibody dynamics using AnyBody in Finite Element Method.

METHOD

Humeral 3D models were reconstructed by MIMICS after volunteers' CT image input in *.dicom format, and processed by Geomagic Studio for surfaces, while locking plates and screws were then designed by Pro-E. A humeral model of T-type fracture was created and assembled in Hypermesh, to integrate fixtures (e.g., MPL/PML/ML), to grid the mesh and then assign materials. A musculoskeletal model of the upper limb was established by AnyBody to simulate elbow flexion and extension. They were finally imported to Abaqus for boundary conditions and dynamic analysis.

RESULT

In terms of Von Mises stress, its maximum increased and then decreased gradually during the joint motion, but p > 0.05 in SPSS suggests no significant difference for all three fixtures. In terms of displacement, when the elbow was at 90°, each motional pattern reached its peak as follows: ML180° = 0.28 mm, MPL90° = 0.49 mm & PML90° = 0.54 mm during flexion; ML180° = 0.073 mm, MPL90° = 0.10 mm & PML90° = 0.12 mm during extension. p < 0.05 suggests a significant difference for the displacements of all three fixations. p = 0.007 < 0.01667 suggests the significant difference between the two fixations, for example, PML90° and ML180°, indicating that the peak displacement of ML180° is less than that of PML90°.

CONCLUSION

After generally analysed in musculoskeletal dynamics, the biomechanical property of the fixtures was presented as follows: the displacement of the parallel plate was less than that of the vertical, and the parallel plate may optimise the clinical reduction anatomically.

Optimal Fixation of the Capitellar Fragment in Distal Humerus Fractures

OBJECTIVES

To determine if orthogonal or parallel plate position provides superior fixation of the separate capitellar fragment often present in intra-articular distal humerus fractures. We hypothesized that orthogonal plating would provide stiffer fixation given a greater number of opportunities for capitellar fixation and screw trajectories perpendicular to the fracture plane offered by a posterolateral plate compared with a parallel plate construct.

METHODS

Ten matched pairs of cadaveric distal humeri were used to compare parallel and orthogonal plating in a fracture gap model with an isolated capitellar fragment. The capitellum was loaded in 20 degrees of flexion using a cyclic, ramp-loading protocol. Fracture displacement was measured using video tracking software. The primary outcome was axial stiffness for each construct. Secondary outcomes included maximum axial and angular fracture displacement.

RESULTS

The parallel plate construct was more than twice as stiff as the orthogonal plate construct averaged across all loads (1464.8 ± 224.0 N/mm vs. 526.3 ± 90.8 N/mm, P < 0.001). Average axial fracture displacement was 0.15 ± 0.03 mm versus 0.53 ± 0.10 mm for parallel versus orthogonal plating, respectively (P = 0.003). Angular fracture displacement was minimal for both constructs (0.009 ± 0.001 degrees vs. 0.028 ± 0.006 degrees for parallel vs. orthogonal constructs).

CONCLUSIONS

Despite fewer points of fixation, a parallel plate construct provided stiffer fixation with less displacement of the simulated capitellar fracture fragment than an orthogonal plate construct in this biomechanical study. In the setting of an articular fracture, in which absolute stability and primary bone healing are desirable, parallel fixation should be considered even in fractures with a separate capitellar fragment if the size of fragment and fracture orientation allows.

Does posterior configuration have similar strength as parallel configuration for treating comminuted distal humerus fractures? A cadaveric biomechanical study

BACKGROUND

The posterior plating technique could be used as a clinical alternative to parallel plating for treating comminuted distal humerus fractures (DHFs) successfully with good clinical results. However, the biomechanical characteristics for posterior fixation are still unclear. The purpose of this study is to evaluate the biomechanical properties of the posterior fixation and to make comparisons between the parallel and the posterior fixation systems.

MATERIALS AND METHODS

We performed a cadaveric biomechanical testing with two posterior plating systems (a posterior two plating and a single posterior pre-contoured Y plating system) and one parallel two plating system to treat AO/OTA type-C2.3 DHFs. Among three groups, we compared construct stiffness, failure strength, and intercondylar width changes after 5000-cycle fatigue loading and failure loads and failure modes after destructive tests in both the axial compression and (sagittal) posterior bending directions. The correlations between construct failure loads and bone marrow density (BMD) were also compared.

RESULTS

In axial direction, there were no significant differences in the stiffness and failure load between the posterior and the parallel constructs. However, in sagittal direction, the two-plate groups (posterior two plating and parallel plating group) had significant higher stiffness and failure loads than the one-plate group (single posterior Y plating). There was no fixation failure after 5000-cyclic loading in both directions for all groups. Positive correlation was noted between BMD and failure loads on parallel fixation.

CONCLUSIONS

We found that when using two plates for treating comminuted DHFs, there were no significant differences in terms of most biomechanical measurements between posterior and parallel fixation. However, the single pre-contoured posterior Y plate construct was biomechanically weaker in the sagittal plane than the parallel and the posterior two-plate constructs, although there was no fixation failure after the fatigue test for all groups regardless of the fixation methods.

LEVEL OF EVIDENCE

Biomechanical study.

A custom-made distal humerus plate fabricated by selective laser melting

This study aims to evaluate the mechanical performance of custom 3D-printed titanium plates in the treatment of distal humerus fractures. Rigidity of four plating configurations were investigated by finite element analysis. The results reveal that implementation of custom designs with minimal screw holes, lateral-medial linking screw and lateral brim could significantly improve stiffness and consequently leads to better biomechanical stability as compared to standard osteosynthesis design. Biomechanical testing was also performed to validate practical usability. The results confirm that newly designed custom plates fabricated by selective laser melting is a possible alternative for the treatment of distal humerus fracture.

Number of screws in the articular segment of distal humerus AO/OTA C-type fractures treated with open reduction internal fixation is associated with complication rate

Introduction: Surgical treatment of distal humerus fractures can lead to numerous complications. Data suggest that the number of screws in the distal (articular) segment may be associated with complication rate. The purpose of this study is to evaluate the association between a number of screws in the distal segment and complication rate for surgical treatment of distal humerus fractures. We hypothesize that the number of screws in the articular segment of distal humerus AO/OTA C-type fractures treated with open reduction internal fixation (ORIF) will be inversely proportional to the complication rate. Methods: We performed a single-center retrospective cohort study of 27 patients who underwent ORIF of distal humerus fractures C-type with at least six months of radiographic and clinical follow-up. Clinical outcomes including a range of motion, pain, revision surgery for stiffness and/or heterotopic ossification (HO), nonunion, and persistent ulnar nerve symptoms requiring revision neurolysis were recorded. Results: In C-type fractures, the use of three or fewer articular screws was significantly associated with nonunion or loss of fixation (RR 17, p = 0.006). Nineteen of 36 (53%) patients experienced at least one complication. The surgical approach, plate configuration, age, and ulnar nerve treatment (none, in situ release, transposition) were not associated with the need for revision surgery. Men had a higher risk of requiring surgical contracture release due to improving post-operative stiffness (RR 12, p = 0.02). Conclusion: In this retrospective study, the use of three or fewer screws to fix articular fragments in AO type C fractures was a significant risk for nonunion or loss of fixation. Plate configuration and surgical approach did not correlate with outcomes. Men had higher rates of complications and required more frequent revision surgery compared to women.

Surgical tips and tricks for coronal shear fractures of the elbow

INTRODUCTION

Coronal shear fractures of the distal humerus represent an uncommon lesion and could be burdened by high complications. This complex lesion requires an accurate reduction and surgical fixation for a better outcome. Different techniques have been described, however no standard protocol have been proposed. Purpose of this retrospective study, is to evaluate the clinical and radiological outcome with posterior cannulated self-tapping headless screws followed by an early-active-motion protocol and to outline the surgical tips and tricks for different fracture patterns.

MATERIALS AND METHODS

From 2013 to 2019, a consecutive series of 24 patients with coronal shear fracture undergoing ORIF were included in the study. Fractures were classified according to Dubberley's classification. Cannulated self-tapping headless screws were used to fix the fragments. When necessary, additional cannulated half-threaded screws on the lateral edge of the humerus were used, as well as bone chips and fibrin sealant on severe comminution. All patients underwent an assisted early-active-motion rehabilitation protocol. Mean follow-up was 30 months; patients underwent standard X-rays and clinical outcome assessment with range of motion, Broberg and Morrey score and MEPI score.

RESULTS

Surgical fixation with headless screw guaranteed complete healing of all shear fractures examined, no loss of reduction were reported. ROM assessment showed good results with an average arc of 113.1°. Excellent to good Broberg-Morrey and MEPI score were reported. No cases of avascular necrosis nor post-traumatic osteoarthritis resulted in our series. Complications occurred in 16.6% of the patients.

CONCLUSION

Coronal shear fracture represents a challenging injury to treat. Anatomical reduction and the use of cannulated self-tapping headless screws from posterior provide a stable fixation, high union rates and good elbow function, with a low cartilage damage and risks of necrosis over 2 years of follow-up.

LEVEL OF EVIDENCE

Therapeutic III.

A pilot biomechanical study comparing a novel, intramedullary Nail/Plate construct to standard Dual-Plate fixation of intra-articular C2.3 distal humerus fractures

BACKGROUND

The gold-standard treatment for intra-articular distal humerus fractures (DHFs) is dual-plate/dual-column fixation, though optimal orientation is not yet established. With a superior method not yet identified, we propose a load-sharing construct, combining absolute stability (extramedullary plate fixation) for distal articular fragments and relative stability (load-sharing intramedullary nail) for the metaphyseal segment. The purpose of this pilot study was to evaluate the biomechanical performance of a novel implant compared to orthogonal dual-plating.

MATERIALS AND METHODS

Ten fresh-frozen matched-pairs of human cadaveric upper extremities with no prior elbow pathology/surgery were used. Pairs were randomized into two groups: Dual-Plate (medial and posterolateral) or novel Nail/Plate (cross-locked medial nail and posterolateral plate). AO/ASIF type 13-C2.3 multifragmentary fractures with simulated metaphyseal comminution. Biomechanical testing included stiffness (MPa) and load to failure (Newtons) in axial (100 cycles at 3 Hz at 20 N increments from 20 to 100 N) and coronal (varus/valgus; 4,000 cycles from 50N-100 N at 3 Hz) planes. Failed specimens were not analyzed and mechanisms were identified. For all failures, mechanisms were identified and reviewed by three consultant surgeons for revision vs. immobilization, to attempt to recreate a real-world scenario. All outcomes were compared between groups.

RESULTS

During stiffness testing, zero Nail/Plate specimens failed, but two (20%) Dual-Plate specimens failed (mechanisms: fracture diastasis; bone collapse and intussusception into osteotomy, yielding articular congruency loss). For remaining samples, Nail/Plate (n = 10) coronal (varus/valgus) stiffness was comparable to Dual-Plate (n = 8) constructs (41.5 vs. 39.0 MPa, p = 0.440). Remaining Dual-Plate constructs had greater axial overall stiffness than Nail/Plate (118.3 ± 48.3 vs. 95.6 ± 34.7 MPa, p = 0.020). Failure loads were comparable between Nail/Plate and Dual-Plate constructs (1,327.8 vs. 1,032.4 N, p = 0.170). Individual nail yield strength ranged from 1,101.1-1,124.4 N (n = 2). In review of all failures, the most common overall mechanism was fracture/osteotomy site posterolateral plate bending. Revision recommendation rate was comparable between constructs (Nail/Plate, 22.2% vs. Dual-Plate, 44.4%, p>0.05).

CONCLUSIONS

The novel Nail/Plate construct demonstrated non-inferior coronal (varus/valgus) stiffness, despite producing lower axial stiffness than orthogonal dual-plating, potentially due to the load-sharing cross-locked design. Considering comparable biomechanical performance, with no failures and comparable recommendations for revision, this novel construct warrants further evaluation as an alternative to the gold-standard, dual-plate fixation method for intra-articular distal humerus fractures.

LEVEL OF EVIDENCE

N/A.

Parallel versus orthogonal plate osteosynthesis of adult distal humerus fractures: a meta-analysis of biomechanical studies

PURPOSE

There are two widely used distal humerus fracture (DHF) fixation methods with either orthogonal or parallel double-plate osteosynthesis. However, biomechanical studies have shown inconsistent results on which technique is more effective. We performed a meta-analysis to compare these two fixation methods for adult DHF fixation.

METHODS

We searched the literature for entries discussing the biomechanical testing of orthogonal and parallel fixation techniques for DHFs. We then performed a meta-analysis of the following biomechanical outcome measures: axial/sagittal/coronal/torsional stiffness, load to failure, and torque to failure.

RESULTS

Seventeen studies comparing both constructs were included. The parallel configuration exhibited greater mechanical strength with respect to axial stiffness/load to failure, torsional stiffness, and posterior bending load to failure than the orthogonal constructs. Subgroup analysis revealed that parallel constructs also had higher torsional stiffness in supracondylar fractures.

CONCLUSIONS

This meta-analysis shows that parallel constructs provide greater axial stiffness, axial strength, and torsional stiffness than orthogonal plate for DHF fixation. A subgroup analysis revealed that parallel constructs had better torsional stiffness in supracondylar fracture fixation.

LEVEL OF EVIDENCE

IA.

Evaluation of risk factors for stiffness after distal humerus plating

PURPOSE

In distal humerus fractures, the goal is to achieve a functional range of motion of 30°-130° which is not always possible. The aims of the study were to evaluate the functional results after distal humerus fracture operation and to investigate the risk factors for stiffness.

METHODS

Between 2005 and 2014, 75 patients with the mean age of 37.8 years (17-80) underwent open reduction and plate fixation for distal humerus fractures. Range of motion (ROM), Mayo elbow performance scores, and quick DASH scores were used for functional evaluation. Patients were divided into two groups according their ROM. Group 1 had > 100° of extension-flexion ROM and group 2 had < 100°. Older age (> 60), AO type C2-3 fracture, open fracture, longer injury-surgery interval, type of plating, and presence of olecranon osteotomy were investigated as risk factors for poor outcome.

RESULTS

At a mean follow-up of 25 months (6-80), 40 patients were in group 1 and 35 patients were in group 2. Group 1 had significantly better functional scores than group 2. AO type C2 and C3 fracture (odds ratio (OR) 16.6, p < 0.0001) and injury-surgery interval longer than 7 days (OR 2.59, p 0.047) were found as significant risk factors for stiffness.

CONCLUSIONS

Patients who had distal humerus fracture should be informed about the risk of elbow stiffness especially in AO type C2-C3 fractures and surgical treatment should be planned without any delay.