Biomechanical comparison of osteoporotic distal radius fractures fixed by distal locking screws with different length

Evaluation of Unicortical Locking Screw Placement for Torsional Loads in Distal Radius Fractures: A Biomechanical Study in Cadavers

Background We aimed to compare bio-mechanical outcomes of short-length 75%-length uni-cortical screw (SL75UCS) and full-length 100%-length screws (FL100S) under axial compression (AXC) and torsional compression (TRC) in cadaveric distal radius volar plate model. Methodology A total of 20 wrists from 10 fresh frozen cadavers were included. A 2.5 mm titanium alloy distal radius anatomical plate was placed to the distal radii in full anatomical position, just proximal to the watershed line. Three bi-cortical screws to the shaft of the radius, followed by uni-cortical drilling for distal screwing were placed. Measurement by pulling the drill once it reached the opposite cortex was applied. We selected the screw lengths such that they corresponded to the SL75UCS. In the same configuration for each of the cadavers, we delivered six screws from distal radius holes of the anatomical plate. An oscillating handsaw was used to create an extra-articular distal radius fracture model (AO 23-A3.2). We created a dorsal AP model by performing a 1-cm wedge osteotomy from the dorsal aspect. Complete separation of the volar cortex was achieved. Potting was performed by embedding the shaft of the prepared radius into the polyurethane medium. We placed aluminum apparatus into the distal end to ensure applying of AXC and TRC in bio-mechanistic tests. Results No statistically significant difference of stiffness between the SL75UCS and FL100S both under AXC (p=0.88) and TRC (p=0.82). SL75UCS and FL100S groups did not differ in elastic limit under AXC (p=0.71) and TRC (p=0.71). Maximal force on SL75UCS and FL100S groups were also similar under both AXC (p=0.71) and TRC (p=0.50). Conclusions Our study findings suggest that drilling the dorsal cortex may not be necessary in the management of distal radius fractures. Instead, utilizing SL75UCS could serve as a viable alternative. This approach offers potential advantages in reducing the risk of extensor tendon complications associated with drilling or screw protrusion. It is a safe method under torsional load to avoid drilling of the dorsal cortex and SL75UCS could be performed in order to prevent from extensor tendon complications secondary to drilling or screw protrusion.

Reduction Techniques in Volar Locking Plate Fixation of Distal Radius Fractures

Distal radius fractures are the most common upper extremity fracture and volar locking plate fixation has become a common modality for operative management of these injuries over the last 2 decades. However, despite the widespread use of volar locking plates, there remains no comprehensive guide detailing the available reduction techniques using these systems. This review aims to consolidate the reduction techniques from the literature along with the authors' experiences into a blueprint for distal radius fracture reduction when using a volar plate. Techniques described include those with and without use of the plate and with supplementary means of fixation for both extra-articular and intra-articular fracture patterns.

Mechanical Comparison of a Novel Hybrid and Commercial Dorsal Double Plating for Distal Radius Fracture: In Vitro Fatigue Four-Point Bending and Biomechanical Testing

This study compares the absolute and relative stabilities of a novel hybrid dorsal double plating (HDDP) to the often-used dorsal double plating (DDP) under distal radius fracture. The “Y” shape profile with 1.6 mm HDDP thickness was obtained by combining weighted topology optimization and finite element (FE) analysis and fabricated using Ti6Al4V alloy to perform the experimental tests. Static and fatigue four-point bending testing for HDDP and straight L-plate DDP was carried out to obtain the corresponding proof load, strength, and stiffness and the endurance limit (passed at 1 × 10⁶ load cycles) based on the ASTM F382 testing protocol. Biomechanical fatigue tests were performed for HDDP and commercial DDP systems fixed on the composite Sawbone under physiological loads with axial loading, bending, and torsion to understand the relative stability in a standardized AO OTA 2R3A3.1 fracture model. The static four-point bending results showed that the corresponding average proof load values for HDDP and DDPs were 109.22 N and 47.36 N, that the bending strengths were 1911.29 N/mm and 1183.93 N/mm, and that the bending stiffnesses were 42.85 N/mm and 4.85 N/mm, respectively. The proof load, bending strength and bending stiffness of the HDDPs were all significantly higher than those of DDPs. The HDDP failure patterns were found around the fourth locking screw hole from the proximal site, while slight plate bending deformations without breaks were found for DDP. The endurance limit was 76.50 N (equal to torque 1338.75 N/mm) for HDDP and 37.89 N (equal to torque 947.20 N/mm) for DDP. The biomechanical fatigue test indicated that displacements under axial load, bending, and torsion showed no significant differences between the HDDP and DDP groups. This study concluded that the mechanical strength and endurance limit of the HDDP was superior to a commercial DDP straight plate in the four-point bending test. The stabilities on the artificial radius fractured system were equivalent for novel HDDP and commercial DDP under physiological loads in biomechanical fatigue tests.

Avoiding Complications in Distal Radius Fractures

Managing fractures of the distal radius is a fundamental skill for orthopaedic surgeons. Given the prevalence of these fractures, complications following operative management are well described and frequently encountered. Surgeons should be observant in the acute phase for emergent conditions such as acute carpal tunnel syndrome. Careful radiographic examination intra-operatively can help prevent delayed complications by identifying surgical errors such as hardware malposition or malreduction. Many problems that arise during the treatment of distal radius fractures are the result of technical errors and can be anticipated.

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.

Electrospun PCL, gold nanoparticles, and soy lecithin composite material for tissue engineering applications

Soy lecithin has been shown to play a critical role in cell signaling and cellular membrane structure. In addition, it has been shown to increase biocompatibility, hydrophilicity, and decrease cytotoxicity. Gold nanoparticles have also shown to improve cellularity. Lecithin, gold nanoparticles, and polycaprolactone (PCL) solutions were electrospun in order to develop unique mesh materials for the treatment of osteoarthritis. The electrospinning parameters were optimized to achieve different solution ratios for fiber optimization. The amount of lecithin mixed with PCL varied from 30 wt.% to 50 wt.% . Gold nanoparticles (1% to 10% concentrations) were also added to lecithin-PCL mixture. The mechanical and chemical properties of the fiber mesh were analyzed via contact angle test, tensile mechanical tests, Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Cell viability was measured using a WST-1 Assay. Scanning electron microscopy confirmed the successful formation of fiber mesh. The compositions of 40% soy lecithin with PCL in 40% solvent (40:40) resulted in the most well-formed fiber mesh. DSC melt temperatures were statically insignificant; uniaxial stresses and the moduli resulted in no significant difference between the test composition and pristine PCL compositions. WST-1 assay revealed all compositions were non-cytotoxic. Overall, the addition of lecithin increased hydrophilicity while maintaining cell viability and the mechanical and chemical properties of PCL. This study demonstrated that it is possible to successfully electrospin a lecithin, gold nanoparticle, and polycaprolactone scaffold for tissue engineering applications.

Screw Length Optimization of a Volar Locking Plate Using Three Dimensional Preoperative Planning in Distal Radius Fractures

BACKGROUND

A three-dimensional (3D) digital pre-operative planning system for the osteosynthesis of distal radius fracture was developed. The objective of this study was to evaluate screw choices for three-dimensional (3D) digital pre-operative planning of osteosynthesis of distal radius fractures and to compare with the screw choices for the conventional method.

METHODS

Distal radius fracture patients who underwent osteosynthesis using volar locking plates were evaluated. Thirty wrists in the plan group utilized 3D preoperative planning, and nineteen wrists in the control group utilized conventional preoperative assessment. In the plan group, the 3D preoperative planning was performed prior to surgery. The reduction was simulated with 3D image, and the implant choice/placement also simulated on the 3D image. In the control group, standard preoperative planning was performed using posterior-anterior and lateral view radiographs, and CT scan. After the planning, osteosynthesis was performed. During the surgery, the operator performed the reduction and the placement of the plate while comparing images between the pre-operative plan and fluoroscopy. The distal screw lengths and the anteroposterior diameter of the radius along the axis of the distal screws were measured. The ratios of the screw length and radius diameter were evaluated. The screw/radius ratios within the range of 0.75-1.00 were considered appropriate. The screw choices less than 0.75, or greater than 1.00 were considered inappropriate. The rate of appropriate screw choices were compared between plan and control groups.

RESULTS

The results of appropriate screw choices were 86.1% and 74.8% in the plan group and the control group, respectively. The inappropriate screw choices were 14.0% and 25.2% in the plan group and the control group, respectively. The three-dimensional planning significantly increased appropriate screw choices compared to the conventional planning (p < 0.05).

CONCLUSIONS

Three-dimensional digital preoperative planning is useful for the optimization of screw lengths in osteosynthesis of distal radius fractures.

Forces in the Distal Radius During a Pushup or Active Wrist Motions

PURPOSE

To determine the 6 degrees of freedom forces and moments in the distal radius that occur during a pushup or other active wrist motions.

METHODS

Eight fresh-frozen cadaveric wrists were moved through 6 physiological motions and held at 1 static pushup position while the force through the distal radius was measured with a 6 degrees of freedom load cell. Three levels of compressive force were applied at the pushup position.

RESULTS

Active wrist motions caused axial forces up to 283 N and moments up to 0.7 N-m. Those motions with a smaller range had significantly smaller axial forces than the larger flexion-extension or dart-thrower's motions. With an 89-N pushup force applied, the average maximum axial force was 69 N, the radially directed force was 12 N, and the moment about the radioulnar axis was 2.3 N-m. Linear extrapolation of the forces to 100% body weight indicate that the axial force going through the distal radius would be 663 N, the radial force would be 147 N, and the moment about the radioulnar axis would be 18.6 N-m.

CONCLUSIONS

Large distal radius forces and moments can occur during pushup and active wrist motions. There are not only large axial compressive forces but also nontrivial radially directed forces.

CLINICAL RELEVANCE

This study may help surgeons and therapists better treat complicated distal radius fractures as well as provide for better comparisons of existing or new distal radius plates and constructs that are designed to treat these complicated loading patterns.

Biomechanical Assessment of the Dorsal Spanning Bridge Plate in Distal Radius Fracture Fixation: Implications for Immediate Weight-Bearing

BACKGROUND

The goal of this study was to compare the biomechanical stability of a 2.4-mm dorsal spanning bridge plate with a volar locking plate (VLP) in a distal radius fracture model, during simulated crutch weight-bearing.

METHODS

Five paired cadaveric forearms were tested. A 1-cm dorsal wedge osteotomy was created to simulate an unstable distal radius fracture with dorsal comminution. Fractures were fixed with a VLP or a dorsal bridge plate (DBP). Specimens were mounted to a crutch handle, and optical motion-tracking sensors were attached to the proximal and distal segments. Specimens were loaded in compression at 1 mm/s on a servohydraulic test frame until failure, defined as 2 mm of gap site displacement.

RESULTS

The VLP construct was significantly more stable to axial load in a crutch weight-bearing model compared with the DBP plate (VLP: 493 N vs DBP: 332 N). Stiffness was higher in the VLP constructs, but this was not statistically significant (VLP: 51.4 N/mm vs DBP: 32.4 N/mm). With the crutch weight-bearing model, DBP failed consistently with wrist flexion and plate bending, whereas VLP failed with axial compression at the fracture site and dorsal collapse.

CONCLUSIONS

Dorsal spanning bridge plating is effective as an internal spanning fixator in treating highly comminuted intra-articular distal radius fracture and prevents axial collapse at the radiocarpal joint. However, bridge plating may not offer advantages in early weight-bearing or transfer in polytrauma patients, with less axial stability in our crutch weight-bearing model compared with volar plating. A stiffer 3.5-mm DBP or use of a DBP construct without the central holes may be considered for distal radius fractures if the goal is early crutch weight-bearing through the injured extremity.

Detection of penetration of the dorsal cortex by epiphyseal screws of distal radius volar plates: Anatomical study comparing ultrasound and fluoroscopy

HYPOTHESIS

Osteosynthesis of the distal radius by a volar plate can be complicated by lesions of extensor tendons by screws penetrating the dorsal cortex. The fluoroscopic skyline view enables to confirm the length of the screws. To avoid its risk of irradiation, some authors have recommended using ultrasound instead.

MATERIAL AND METHODS

The goal of this study was to demonstrate that the detection rate of screws penetrating the dorsal cortex was at least as good using ultrasound compared to fluoroscopic skyline. A volar plate in which one screw penetrated the dorsal cortex was implanted in 10 cadaveric wrists. Three observers had to detect which screw penetrated the dorsal cortex using ultrasound and then a fluoroscopic skyline.

RESULTS

The detection rate of screws penetrating the dorsal cortex was 43.33% with ultrasound and 96.97% using the fluoroscopic skyline. Agreement between the observers was poor with ultrasound and good with fluoroscopy.

CONCLUSION

Our results show that ultrasound cannot replace the fluoroscopic skyline view to detect screws penetrating the dorsal cortex of the distal radius in clinical practice.

LEVEL OF EVIDENCE

II.

[Distal radius fracture of the adult : Diagnostics and therapy]

Fractures of the distal radius are very common. The majority of patients are elderly females. High impact trauma are often responsible for fractures in young men. Clinical and radiological diagnostics, including computer-assisted tomography (CAT) scan, are generally sufficient. The indication for conservative treatment is still recommended for specific fracture patterns. Application of palmar locking plates after open reduction proved to be efficacious for the majority of fracture patterns. Furthermore, precise detection and treatment of concomitant lesions are mandatory in order to prevent complications.

[Design of distal radius volar locking plates : Anatomical, surgical and biomechanical aspects]

The operative treatment of unstable distal radius fractures primarily aims for the anatomical reduction of the joint while addressing accompanying injuries. Anatomical reduction, stable fixation and early functional movement of the joint are the three cornerstones of modern treatment concepts of distal radius fractures. Distal radius volar locking plates play a major role in the treatment and rehabilitation of the most commonly occurring fracture in humans. This article outlines the different principles in the current design of available distal radius volar locking plates. The biomechanical aspects, anatomical findings and clinical evaluation that have influenced current design features and trends in new developments of the latest plates are emphasized. This is an ongoing process that is supported through the investigation and feedback of clinical science.

Using self-drilling screws in volar plate osteosynthesis for distal radius fractures: a feasibility study

Background

Symptomatic extensor tendon irritation is a frequent complication in volar plate osteosynthesis of distal radius fractures. It is typically caused by dorsal screw protrusion and overdrilling of the dorsal cortex. The use of self-drilling locking screws (SDLS) could overcome both causes. The practical applicability of SDLS depends on two prerequisites: (1) the feasibility of preoperative distal screw length determination, and (2) sufficient primary biomechanical stability of SDLS compared to standard locking screws (SLS).

Methods

We first assessed the feasibility of preoperative screw length determination (1): Distal radius width, depth and distal screw lengths were measured in 38 human radii. Correlations between distal radius width and depth were assessed, a cluster analysis (Ward’s method and squared Euclidean distance) for distal radius width conducted, and intra-cluster screw lengths analyzed (ANOVA). The biomechanical performance of SDLS (2) was assessed by comparison to SLS in a distal radius fracture model (AO-23 A3). 75 % distal screw length was chosen for both groups to simulate a worst-case scenario. Uniaxial compression tests were conducted to measure stiffness, elastic limit, maximum force and residual tilt. Statistics comprised of independent sample t-tests and a Bonferroni correction (p < 0.0125).

Results

(1) Distal radius width and depth showed a high correlation (R² = 0.79; p < 0.001). Three distal radius width clusters could be identified: small <34 mm; medium 34–36.9 mm; large >36.9 mm. ANOVA and Tukey post-hoc analysis revealed significantly different volar-dorsal depths (p < 0.05) for nearly all screws. (2) To assess biomechanical stability nine specimens were tested each; no significant differences were found between the SDLS and SLS groups.

Conclusions

This feasibility study demonstrates that (1) distal radius width can be used as a predictor for distal screw length and (2) that SDLS provides mechanical stability equivalent to SLS. These results highlight the feasibility of applying SDLS screws in volar plate osteosynthesis at least in extraarticular fractures.

The past, present and future in scaffold-based tendon treatments

Tendon injuries represent a significant clinical burden on healthcare systems worldwide. As the human population ages and the life expectancy increases, tendon injuries will become more prevalent, especially among young individuals with long life ahead of them. Advancements in engineering, chemistry and biology have made available an array of three-dimensional scaffold-based intervention strategies, natural or synthetic in origin. Further, functionalisation strategies, based on biophysical, biochemical and biological cues, offer control over cellular functions; localisation and sustained release of therapeutics/biologics; and the ability to positively interact with the host to promote repair and regeneration. Herein, we critically discuss current therapies and emerging technologies that aim to transform tendon treatments in the years to come.