Biomechanical study of different plate configurations for distal humerus osteosynthesis

Biomechanical design of a new proximal humerus fracture plate using alternative materials

Comminuted proximal humerus fractures are often repaired by metal plates, but potentially still experience bone refracture, bone "stress shielding," screw perforation, delayed healing, and so forth. This "proof of principle" investigation is the initial step towards the design of a new plate using alternative materials to address some of these problems. Finite element modeling was used to create design graphs for bone stress, plate stress, screw stress, and interfragmentary motion via three different fixations (no, 1, or 2 "kickstand" [KS] screws across the fracture) using a wide range of plate elastic moduli (EP = 5-200 GPa). Well-known design optimization criteria were used that could minimize bone, plate, and screw failure (i.e., peak stress < ultimate tensile strength), reduce bone "stress shielding" (i.e., bone stress under the new plate ≥ bone stress for an intact humerus, titanium plate, and/or steel plate "control"), and encourage callus growth leading to early healing (i.e., 0.2 mm ≤ axial interfragmentary motion ≤ 1 mm; shear/axial interfragmentary motion ratio <1.6). The findings suggest that a potentially optimal configuration involves the new plate being manufactured from a material with an EP of 5-41.5 GPa with 1 KS screw; but, using no KS screws would cause immediate bone fracture and 2 KS screws would almost certainly lead to delayed healing. A prototype plate might be fabricated using alternative materials suggested for orthopedics and other industries, like fiber-metal laminates, fiber-reinforced polymers, metal foams, pure polymers, shape memory alloys, or 3D-printed porous metals.

Biomechanical Design Optimization of Distal Humerus Fracture Plates: A Review

The goal of this article was to review studies on distal humerus fracture plates (DHFPs) to understand the biomechanical influence of systematically changing the plate or screw variables. The problem is that DHFPs are commonly used surgically, although complications can still occur, and it is unclear if implant configurations are always optimized using biomechanical criteria. A systematic search of the PubMed database was conducted to identify English-language biomechanical optimization studies of DHFPs that parametrically altered plate and/or screw variables to analyze their influence on engineering performance. Intraarticular and extraarticular fracture (EAF) data were separated and organized under commonly used biomechanical outcome metrics. The results identified 52 eligible DHFP studies, which evaluated various plate and screw variables. The most common plate variables evaluated were geometry, hole type, number, and position. Fewer studies assessed screw variables, with number and angle being the most common. However, no studies examined nonmetallic materials for plates or screws, which may be of interest in future research. Also, articles used various combinations of biomechanical outcome metrics, such as interfragmentary fracture motion, bone, plate, or screw stress, number of loading cycles to failure, and overall stiffness (Os) or failure strength (Fs). However, no study evaluated the bone stress under the plate to examine bone "stress shielding," which may impact bone health clinically. Surgeons treating intraarticular and extraarticular distal humerus fractures should seriously consider two precontoured, long, thick, locked, and parallel plates that are secured by long, thick, and plate-to-plate screws that are located at staggered levels along the proximal parts of the plates, as well as an extra transfracture plate screw. Also, research engineers could improve new studies by perusing recommendations in future work (e.g., studying alternative nonmetallic materials or "stress shielding"), clinical ramifications (e.g., benefits of locked plates), and study quality (e.g., experimental validation of computational studies).

Cadaveric biomechanical assessment of different configurations for a novel pin and plate fixation method in distal humerus fractures

Use of dual pre-contoured plates has been accepted as the treatment of choice in distal humerus fractures despite challenges especially in very distal or highly fragmented fractures. Aiming to improve results in such instances, our newly proposed method uses several K-wires fixated by a small reconstruction plate. Drawing on the results of previous finite element studies, the current study aims to compare the stiffness of three clinically common variations of this method using biomechanical testing in cadaveric humeri. 24 samples were divided into three groups and fractures were simulated. Groups I and II used 1.5 mm K-wires in differing configurations while 2 mm wires were used in group III. All samples underwent compression, anterior and posterior bending, and torsional testing as well as failure testing. Our results indicated that Group III had significantly higher stiffness in flexion, extension, and torsion (p < 0.05). In failure, group III had the highest mean stiffness in anterior bending and torsion (861.2 N, 30.9 Nm). Based on previous and current results, this new Persian fixation method, especially when implemented using 2 mm K-wires, shows promise in achieving suitable stability and may be useful as an alternative approach in complex distal humerus fractures.

Biomechanical effects of different loads and constraints on finite element modeling of the humerus

Currently, there is no established finite element (FE) method to apply physiologically realistic loads and constraints to the humerus. This FE study showed that 2 'simple' methods involving direct head loads, no head constraints, and rigid elbow or mid-length constraints created excessive stresses and bending. However, 2 'intermediate' methods involving direct head loads, but flexible head and elbow constraints, produced lower stresses and bending. Also, 2 'complex' methods involving muscles to generate head loads, plus flexible head and elbow constraints, generated the lowest stresses and moderate bending. This has implications for FE modeling research on intact and implanted humeri.

Adjunctive intraosseous wiring fixation technique for the comminuted distal humeral fractures

Distal humeral fractures are among the most challenging injuries to treat. Although precise repair of the articular surface is essential during surgery, accurate reconstruction of the metaphysis contributes to the overall stability of the fracture construct. The intraosseous wiring technique has been used for small-fragment fractures. However, its efficacy as an adjunct for distal humerus fixation has yet to be thoroughly investigated. This study aimed to demonstrate the applicability of this technique to comminuted, distal humeral fractures. In this retrospective case series, we describe 6 cases of intra-articular distal humerus fractures treated with this technique, followed by dual plating. We observed successful bone union in all patients, with the Mayo Elbow Performance Scores indicating "good" to "excellent" clinical outcomes for this procedure at the final follow-up. We believe that this intraosseous wiring technique should be an integral part of the toolbox of every surgeon because it is a relatively simple and highly effective procedure that requires no special instrument and can be used on various types of fractures.

Biomechanical analysis of different osteosynthesis configurations in the pin and plate fixation method for distal humerus fractures

Distal humerus fractures commonly occur in adults with low bone mineral density causing major technical challenges for orthopedic surgeons. Persian fixation method was introduced as a novel technique to stabilize small fragments in comminuted distal humerus fractures using a set of K-wires and a reconstruction plate. The present study aims to measure this technique's stiffness and stability of this technique and analyze the effect of influential parameters with numerical simulation and biomechanical testing on a cadaveric specimen. Validation of the finite element (FE) model was conducted based on results of experiments. The results indicated that Delta configuration mainly led to a higher stiffness in the case of axial loading and anterior bending compared to L configuration. Analyzing the influential factors of this technique suggests that changes in diameter and number of K-wires have a similarly significant effect on the construct stiffness while the height of plate had a slight influence. Also, the diameter of wires was the most effective parameter for implant failure, particularly in the 3-pin construct, which caused a reduction in failure risk by about 60%. The results revealed that the Persian fixation method would achieve suitable stability compared to the dual-plating technique.

Clinical comparison of double-plate fixation by the perpendicular plate method versus parallel plate method for distal humeral fracture: a multicenter (TRON group) study

INTRODUCTION

Double-plating methods are popular, with perpendicular and parallel plate methods being widely used surgical method for the rigid fixation of distal humeral fracture (DHF). However, which plate method is better for DHF remains controversial. The aim of this study was to compare patient outcomes including the incidences of complications and reoperation between the two plate methods.

METHODS

We extracted 383 patients with DHF undergoing surgery between 2011 and 2020 from our multicenter database, which is named TRON. We divided the subjects into two groups: perpendicular plating group (Group A) and parallel plating group (Group B). To adjust for baseline differences between the groups, patients were matched for age, sex, olecranon osteotomy, AO type, and type of injury. We assessed the Mayo Elbow Performance Score (MEPS) at 3 and 6 months and the last follow-up month as the clinical outcome. We investigated the incidences of complications and reoperations in both groups.

RESULTS

After matching, each group comprised 50 patients. There was no significant difference between Group A versus Group B in MEPS score at each time point. The incidence of implant removal in Group B was higher than that in Group A (26.5% vs 50%, p = 0.023).

DISCUSSION

Although there were no significant differences in clinical outcomes or complications between the two groups, the incidence of implant removal was higher in Group B than in Group A. In the parallel plate technique, where the plates have to be placed in areas with thin subcutaneous soft tissue, the incidence of implant removal might be high due to the discomfort caused by the implant.

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.

Dynamics analysis for flexion and extension of elbow joint motion based on musculoskeletal model of Anybody

PURPOSE

Little is known about how biomechanics governs the biological nature for humeral motion dynamically. Elbow motion ought to be investigated based on a musculoskeletal model and evidence the physiologic principle of upper limbs.

METHOD

A humeral model was reconstructed by MIMICS after CT images input in *.dicom format, it was processed by Geomagic Studio for Surfaces, then gridded mesh and assigned materials by Hypermesh. On the other hand, a musculoskeletal model was built by AnyBody, physical motions were then simulated to export boundary condition and myodynamia during flexion and extension. Finally, all the humeral model and boundary were imported to Abaqus for finite element analysis.

RESULT

During the simulative motion of flexion, the primary muscles are brachii biceps, brachialis anticus and teretipronator, their myodynamia increased and then decreased gradually, and reached its peak value at 30°; During extension, the main muscles are triceps brachii and brachialis anticus, their myodynamia increased and then decreased gradually too, and reached peak at 50°; In these two cases, their strain and displacement distributed at the middle of humerus.

CONCLUSION

AnyBody is a novel modelling system to simulate physical motion, for example flexion and extension. Biceps brachii and brachialis anticus are functional for flexion, and triceps brachii plays a key role in extension critically. This simulation confirms the physiologic rule for sport event, humeral fixation and postoperative healing with clinical significance that minimizing joint forces from injury onset may promote pain-free ways.

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.

Biomechanical evaluation of the stability of extra-articular distal radius fractures fixed with volar locking plates according to the length of the distal locking screw

Surgeons usually used short screws to avoid extensor tendon problems during volar locking plate fixation in distal radius fracture. However, the stability according to the length of distal locking screws have not been fully understood. We investigated this issue through finite element analysis and compression test using synthetic radius. Our results demonstrated that the bi-cortical full-length fixation does not contribute to the stiffness increase in the axial compression direction, and a reduction in length of up to more than 50% length can still provide similar stability to full-length screws. Our data can support that surgeon should undersize the distal screw.

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.

Biomechanical Analysis of a Novel Intercalary Prosthesis for Humeral Diaphyseal Segmental Defect Reconstruction

OBJECTIVE

To study the biomechanical properties of a novel modular intercalary prosthesis for humeral diaphyseal segmental defect reconstruction, to establish valid finite element humerus and prosthesis models, and to analyze the biomechanical differences in modular intercalary prostheses with or without plate fixation.

METHODS

Three groups were set up to compare the performance of the prosthesis: intact humerus, humerus-prosthesis and humerus-prosthesis-plate. The models of the three groups were transferred to finite element software. Boundary conditions, material properties, and mesh generation were set up for both the prosthesis and the humerus. In addition, 100 N or 2 N.m torsion was loaded to the elbow joint surface with the glenohumeral joint surface fixed. Humeral finite element models were established according to CT scans of the cadaveric bone; reverse engineering software Geomagic was used in this procedure. Components of prosthetic models were established using 3-D modeling software Solidworks. To verify the finite element models, the in vitro tests were simulated using a mechanical testing machine (Bionix; MTS Systems Corporation, USA). Starting with a 50 N preload, the specimen was subjected to 5 times tensile (300 N) and torsional (5 N.m) strength; interval time was 30 min to allow full recovery for the next specimen load. Axial tensile and torsional loads were applied to the elbow joint surface to simulate lifting heavy objects or twisting something, with the glenohumeral joint surface fixed.

RESULTS

Stress distribution on the humerus did not change its tendency notably after reconstruction by intercalary prosthesis whether with or without a plate. The special design which included a plate and prosthesis effectively diminished stress on the stem where aseptic loosening often takes place. Stress distribution major concentrate upon two stems without plate addition, maximum stress on proximal and distal stem respectively diminish 27.37% and 13.23% under tension, 10.66% and 11.16% under torsion after plate allied.

CONCLUSION

The novel intercalary prosthesis has excellent ability to reconstruct humeral diaphyseal defects. The accessory fixation system, which included a plate and prosthesis, improved the rigidity of anti-tension and anti-torsion, and diminished the risk of prosthetic loosening and dislocation. A finite element analysis is a kind of convenient and practicable method to be used as the confirmation of experimental biomechanics study.

Bicolumnar 90-90 plating of AO 13C type fractures

Objective

The aim of this study was to evaluate functional results and complication rate of patients who underwent medial-dorsolateral plating for intra-articular distal humeral fracture (Müller AO type 13C).

Methods

Twenty-four patients (14 men, 10 women; mean age: 47 years) with AO type 13C distal humerus fracture were included in the study. Mean follow-up time was 28 months. Nine patients were in 13C1 subgroup, according to AO classification system, 11 patients were categorized as 13C2, and 4 patients were 13C3. Final follow-up assessment of outcomes included Broberg and Morrey radiological criteria; Mayo Elbow Performance Score, disabilities of the Arm, Shoulder and Hand (DASH) Outcome Measure, score based on Jupiter criteria; and range of motion (ROM) values.

Results

The mean carrying angle of operated elbows was 11.37° (range: 0-20°). According to Broberg and Morrey radiological criteria, 14 patients, had radiologically normal elbow, 4 patients had mild change, 3 patients had moderate change, and 3 patients had severe radiological change. Mean DASH score was 21.91 (range: 0-50), and mean Mayo rating was 83.37 (range: 55-100). Jupiter criteria evaluation revealed excellent results in 10 cases, good in 12, and fair results in 2. One patient with fair result had open fracture, and the other had previous hemiparesis in the same extremity. There was no instance of nonunion observed at follow-up.

Conclusion

Osteosynthesis with medial-dorsolateral plating is a safe and effective method for the treatment of intra-articular fractures of distal humerus.

Level of evidence

Level IV, Therapeutic study.

[Distal humerus fracture-extensile approaches]

The majority of dislocated, intra-articular fractures are treated with an open reduction and internal fixation. In this paper we describe a variety of dorsal approaches to the distal humerus. Beside the dorsal approach through an olecranon osteotomy we also discuss the alternative dorsal approaches without osteotomy and their advantages and drawbacks. Moreover we discuss the preoperative planning and operative procedure. Early functional rehabilitation, without weight bearing, is important to achieve an optimal outcome. Finally we present the results of the last 6 years of patients treated operatively in our clinic with distal humeral fractures.

Surgical management of complex intra-articular distal femoral and bicondylar Hoffa fracture

Bicondylar Hoffa's fractures of distal femur are rare. We report the case of an 18-year-old male who sustained a closed complex fracture of both femoral condyles of the left femur on the sagittal plane (Hoffa fracture), combined with distal metaphyseal fracture. He was treated using parallel plates and interdigitating screws, with our technique based on an extrapolation of the principles of distal humerus fixation. The fracture united clinically and radiologically at 16 weeks. Twelve months postoperatively, the range of movement in the knee was 5°-115°. In this complex case, our technique provided stable fixation of the fragments and a satisfactory final functional outcome.

Distal humerus fractures: a review of current therapy concepts

Fractures of the distal humerus in the adult comprise approximately one third of all humeral fractures. Successful management of distal humerus fractures depends on correct reduction of the fracture, reconstruction of the articular surface if needed, stability and rigidity of the fixation, and appropriate rehabilitation. In this review, we evaluated the available literature and highlighted current therapy concepts. We assessed the evolution of internal fixation and elbow arthroplasty focusing on the established surgical approaches against the background of a growing incidence of distal humeral fractures in an aging patient population. Therefore evaluating the aspect and influence of age-dependent comorbidities like osteoporosis on successful treatment.