The influence of distal screw length on the primary stability of volar plate osteosynthesis--a biomechanical study

Volar Locking Plating of Extra-articular Distal Radius Fracture: A Retrospective Clinical Study Comparing Locking Screws versus Smooth Locking Pegs

Background  Open reduction and internal fixation of distal radius fractures is one of the most common procedures performed in wrist surgery. The use of volar locking plate has gained increasing interest in the past decade. Epiphyseal fixation can be done either with locking screws or smooth locking pegs, with no evidence supporting the use of one rather than the other. Purpose  The aim of this study is to compare the stability of distal radius fixation by volar locking plate using locking screws or smooth locking pegs. Methods  Adult patients with A2-A3 AO fractures treated with a volar plate with locking screws only or smooth locking pegs only were retrospectively included. Radiographic assessment was performed to evaluate extra-articular parameters in the intraoperative postreduction and fixation period and after bony healing. Forty-seven distal radius fractures were included. Results  Twenty-four fractures had fixation with locking screws and 23 had fixation with smooth locking pegs. For both groups, all radiographic parameters measured showed a statistically significant difference between the intraoperative postreduction and fixation period and the remote postoperative period after union of the fracture ( p  < 0.05) attesting a slight loss of reduction. Nevertheless, there were no significant differences between the groups in radiographic extra-articular parameters. Conclusion  This clinical study shows that there is no difference in stability fixation between locking screws or smooth locking pegs in A2-A3 distal radius fractures. Clinical Relevance  The use of smooth locking pegs only for epiphyseal fixation appears to be safe in volar plating of A2-A3 distal radius fractures in adult patients and could be an alternative to locking screws. More clinical data are needed to confirm these results. Level of Evidence  Level III; retrospective comparative study.

Avoiding screw overlength using dorsal horizon view in palmar plate osteosynthesis of distal radius fractures: a prospective randomized trial

INTRODUCTION

Distal radius fractures are the most commonly reported fractures in adults. Treatment has changed in recent years to open reduction and palmar plate fixation. Penetration of the dorsal screw, however, is a well-known complication. Intraoperative anteroposterior and lateral radiographs lack the exact assessment of dorsal screw length and intraoperative measurement is therefore very likely to be inaccurate in a comminuted dorsal radial cortex. Secondary extensor tendon ruptures are reported in up to 6% following palmar plate fixation of distal radius fracture.

MATERIALS AND METHODS

A prospective randomized trial was performed to assess the value of the dorsal horizon view. The hypothesis was that the traditional anteroposterior and lateral fluoroscopic views aided by an axial view of the dorsal part of the radius, named dorsal horizon view, could prevent dorsal screw penetration. A total of 40 patients, 6 male and 34 female, were included in the study. Standardized anteroposterior and lateral radiographs were performed intraoperatively in 18 patients (standard group = control group). In 22 patients, intraoperative axial fluoroscopic views (dorsal horizon view) were added to anteroposterior and lateral images (horizon group). Numbers of intraoperative screw changes due to the two different radiological examinations were analyzed as well as exact postoperative CT guided measurement of screw length.

RESULTS

The total numbers of intraoperative screw changes were significantly higher in the horizon group. Forty-two screws were changed in 15 patients in the horizon group while only 8 screws were changed in 3 patients in the standard group. Postoperative computed tomography scans showed significantly lower total numbers of perforating screws in the horizon group with 11 screws in 22 patients compared to 20 screws in 18 patients in the standard group (p = 0.02).

CONCLUSIONS

Based on the results of this study, the dorsal horizon view improves the assessment of the correct screw length and should routinely be used in palmar plate osteosynthesis of distal radius fractures. Since screw protrusion cannot be absolutely ruled out using the dorsal horizon view, monocortical drilling or screw downsizing is still mandatory.

TRIAL REGISTRATION

This clinical trial was not registered because it was a clinical examination without any experimental techniques.

LEVEL OF EVIDENCE: 2

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.

Accuracy of osseointegrated screw-bone construct stiffness and peri-implant loading predicted by homogenized FE models relative to micro-FE models

Computational predictions of stiffness and peri-implant loading of screw-bone constructs are highly relevant to investigate and improve bone fracture fixations. Homogenized finite element (hFE) models have been used for this purpose in the past, but their accuracy has been questioned given the numerous simplifications, such as neglecting screw threads and modelling the trabecular bone structure as a continuum. This study aimed to investigate the accuracy of hFE models of an osseointegrated screw-bone construct when compared to micro-FE models considering the simplified screw geometry and different trabecular bone material models. Micro-FE and hFE models were created from 15 cylindrical bone samples with a virtually inserted, osseointegrated screw (fully bonded interface). Micro-FE models were created including the screw with threads (=reference models) and without threads to quantify the error due to screw geometry simplification. In the hFE models, the screws were modelled without threads and four different trabecular bone material models were used, including orthotropic and isotropic material derived from homogenization with kinematic uniform boundary conditions (KUBC), as well as from periodicity-compatible mixed uniform boundary conditions (PMUBC). Three load cases were simulated (pullout, shear in two directions) and errors in the construct stiffness and the volume average strain energy density (SED) in the peri-implant region were evaluated relative to the micro-FE model with a threaded screw. The pooled error caused by only omitting screw threads was low (max: 8.0%) compared to the pooled error additionally including homogenized trabecular bone material (max: 92.2%). Stiffness was predicted most accurately using PMUBC-derived orthotropic material (error: -0.7 ± 8.0%) and least accurately using KUBC-derived isotropic material (error: +23.1 ± 24.4%). Peri-implant SED averages were generally well correlated (R² ≥ 0.76), but slightly over- or underestimated by the hFE models and SED distributions were qualitatively different between hFE and micro-FE models. This study suggests that osseointegrated screw-bone construct stiffness can be predicted accurately using hFE models when compared to micro-FE models and that volume average peri-implant SEDs are well correlated. However, the hFE models are highly sensitive to the choice of trabecular bone material properties. PMUBC-derived isotropic material properties represented the best trade-off between model accuracy and complexity in this study.

Optimal screw length in volar locking plate osteosynthesis for distal radius fractures: a systematic review

BACKGROUND

Fractures of the distal radius represent the most common fracture of the upper limb, and can be managed surgically with volar locking plate osteosynthesis (VLPO). Uncertainty remains regarding the optimal length of the distal locking screws. The aim of this study was to determine the optimal VLPO screw length which provided adequate stability while minimizing complications.

METHODS

A systematic review of relevant literature published within Cochrane, PubMed, MEDLINE and Embase, including studies up to April 2020, was performed using the Preferred Reporting Items for Systemic Reviews and Meta-analysis (PRISMA) guidelines. Studies were included if they investigated distal radius fracture fixation with VLPO, screw lengths, complications, and associated imaging.

RESULTS

Search results identified 664 relevant studies, of which 14 studies examining 926 radii were included for review. Synthesis revealed that unicortical locking fixation with screws ~75% the depth of the radius, or 2 mm short of the dorsal cortex, provided equivalent stability to bicortical fixation. The lunate may be used as a proxy to determine radial depth at each quartile column. Inadvertent screw protrusion can be assessed by taking four images intra-operatively; anteroposterior (AP), lateral, 45° supinated and dorsal tangential views (DTVs). Radial shaft screws can have up to 2 mm prominence with no clinical significance.

CONCLUSION

Unicortical locking fixation at least 75% the depth of the distal radius provides equivalent stability to bicortical fixation in extra-articular fractures with lower complication rates. Imaging should be used to confirm that penetration of the dorsal cortex has not occurred.

Loss of radial height in extra-articular distal radial fracture following volar locking plate fixation

BACKGROUND

Radial height is an important prognostic factor in treating distal radius fracture. However, does further collapse of radial height in distal radius fractures after with volar locking plate fixation have a great impact on the prognosis? The present study aimed to elucidate radial height loss and determine the associated risk factors after open reduction and internal fixation with volar locking plate in patients with extra-articular distal radius fractures.

HYPOTHESIS

Patients with radial height collapse after fracture reduction and internal fixation with a volar locking plate may have poor outcomes.

METHODS

Data of 87 patients (21 male) undergoing surgery for acute extra-articular distal radius fractures (AO: 23-A2 or 23-A3) between February 2014 and July 2016 were evaluated retrospectively. Patients were divided into two groups by radial height loss. Potential risk factors were tested by Pearson correlation coefficients. Stepwise multiple regression logistic analysis determined significant independent risk factors for extra-articular distal radius fractures. Clinical evaluation was performed by the same surgeon by determining wrist ROM. Grip strength was measured with a Jamar dynamometer and compared with non-affect wrist in percentage. In addition, all the patients were asked to grade modified Mayo wrist score and Visual Analogue Scale (VAS) score. These findings were recorded postoperative 1 year of follow-up.

RESULTS

Mean radial height loss was 1.3±0.9mm. Age (ß=0.002, p=0.003), postoperative ulnar-positive deformity (ß=0.107, p<0.001), DEXA (ß=-0.015, p=0.008), and shortest diameter of distal fracture fragment in AP and lateral views (ß=-0.050, p=0.037; ß=-0.080, p=0.043) were significantly associated with radial height loss. As for the outcome of clinical prognosis, though radial height collapse group had poorer wrist range of motion, there was no statistical difference. Besides, there were no significant differences in grips strength and VAS score between these two groups. However, in regards of modified Mayo wrist score, the percentage of patients with poor outcomes is significant higher in radial height collapse group (p=0.039). Moreover, all patients with poor outcomes in radial height collapse groups were older than 65-year-old.

DISCUSSION

Radial height loss is noted in patients undergoing open reduction and internal fixation with volar locking plate for extra-articular distal radius fractures. Risk factors for radial height collapse include advanced age, poor bone quality, shortest distance between fracture site and articular surface and postoperative ulnar-positive deformity.

LEVEL OF EVIDENCE

IV; non-comparative prospective study.

Effect of Downsized Screw Selection on Bone Healing and Postoperative Complications in Volar Plating of Distal Radius Fractures

When performing volar plating of distal radius fractures, selecting downsized subchondral screws may prevent dorsal screw penetration (DSP), which is a risk factor for extensor tendon rupture. However, downsizing may cause loss of reduction or poor bone healing. This prospective study investigated the effect of downsized screw selection on bone healing and postoperative complications. A total of 115 patients with postoperative follow-up longer than 6 months comprised the study population. Using a depth gauge, screws that were 2-mm shorter than the measured value were selected. The DSP then was checked using dorsal tangential view (DTV) radiographs during surgery and at final follow-up. Baseline data included bone healing, loss of reduction of radiological parameters, DSP location, and postoperative complications. To assess DSP on DTV radiographs, the dorsal surface of the radius was divided into the radial and ulnar sides at the Lister tubercle, and each was further divided into 2 equal regions. These 4 regions were defined as zones 1 to 4 from the radial side. A total of 114 patients (99%) showed bone healing. Mean loss of reduction was approximately 1° and within 1 mm in radiological parameters. Eleven patients (9.6%) showed DSP during surgery or at final follow-up despite using 2-mm downsized screws. The most common site of DSP was zone 3. Extensor pollicis longus rupture occurred in 2 patients (1.7%) despite no DSP. Downsized screw selection provided a high rate of bone healing with minimum loss of reduction and a low complication rate. The extensor tendon can be torn regardless of DSP. [Orthopedics. 2021;44(2):e259-e265.].

Common Complications of Distal Radial Fractures

Distal radial fractures are associated with good outcomes; however, although they occur at low rates, complications can significantly impair treatment success. Therefore, the treating surgeon should be aware of potential complications associated with each treatment type and how to best prevent them. Although certain patient-specific and fracture-specific factors may increase the risk of adverse outcomes, most are nonmodifiable risk factors at the time of presentation, so it is imperative that every effort is made to mitigate these risk factors to prevent long-term morbidity. Patients should be well-informed about these complications and potential symptoms so that they can be addressed expeditiously.

Distal radius fracture fixation using volar plate: A comparative study evaluating the biomechanical behavior of uni and bicortical distal screws

Extensor tendon ruptures caused by bicortical screws impingement following distal radius fracture fixation with volar plates are extensively reported in the literature. Thus, a biomechanical study comparing unicortical and bicortical fixations in intra-articular distal radius fracture models is critical in decision-making regarding distal radius fracture management. Forty-two synthetic radius models were fixed using a variable angle volar distal locking plate with seven screws. They were divided into 6 groups (n = 7): G1/G3/G4 unicortical fixation (75% of anteroposterior distal radius lenght); G2/G4/G6 bicortical fixation. Each group underwent a different mechanical test: axial compression (G1/G2), dorsal flexion (G3/G4), and volar flexion (G5/G6). The load application rate was 5 mm/min and 1000 cycles of 50 to 250 N at 1 Hz were performed between both static tests. Comparative results in the first static test, in the second static test, and in failure generally showed a very similar behavior. Models depicted similar behavior in the second static test when cyclic load was performed. Therefore, one can realize that stiffness differed during dorsal flexion only in the first static test. Maximum force to break the model in axial compression was greater in bicortical than in unicortical construct. Since biomechanical properties are similar, we recommend using unicortical distal locking screws in distal radius fracture fixation with volar plates to prevent extensor tendon ruptures.

Systematic use of short unicortical epiphyseal locking screws versus full-length unicortical locking screws in distal radius fracture volar plating: A prospective and comparative study

PURPOSE

Volar locking plates, used in distal radius fracture (DRF), present a risk of injuring extensor tendons with screws penetrating the dorsal cortex of the radius. Actually, even when aiming to use maximum-length unicortical locking screws, some still could be bicortical. We hypothesize the use of only short unicortical screws would allow a proper stabilization of the radial epiphysis without the risk of dorsal cortex penetration.

MATERIALS AND METHODS

A prospective monocentric non-randomized study was conducted. Patients with DRF (excepted for partial dorsal joint fractures) were treated in group A with short locking epiphyseal screws (16 mm for females, 18 mm for males) and in group B with full-length unicortical locking screws. Ultrasound was done 3 months postoperatively to evaluate the number and length of prominent dorsal screws. X-rays were performed after 6 weeks to assess stability according to volar tilt and radial inclination variations.

RESULTS

There were 37 patients in group A and 39 in group B with 148 and 156 epiphyseal screws, respectively. In group A, there were 0% of dorsal penetrating screws against 6.5% (10 screws from 8 patients) in group B (p < 0.05). There was no significant difference for the stability between the groups: mean volar tilt variation ( - 0.6° vs. - 0.7°) and mean radial inclination variation ( - 0.4° vs. - 0.4°).

CONCLUSION

For a same stability with volar locking plates for DRF, short epiphyseal locking screws should be preferred to full-length unicortical screws in order to prevent extensor tendon injuries. Based on 75% of distal radial average anteroposterior width for each sex, screw lengths of 16 mm for females and 18 mm for males seem to be the length to use. LEVEL OF EVIDENCE 2: Prospective, Comparisons made, non-randomized.

Towards optimization of volar plate fixations of distal radius fractures: Using finite element analyses to reduce the number of screws

BACKGROUND

Using fewer distal screws in volar plate fixation of distal radius fractures could reduce treatment costs and complications. However, there is currently no consensus on the ideal screw configuration, likely due to experimental limitations and its subject-specific nature. In this study, finite element analysis was used to investigate (1) if reducing the number of screws is biomechanically feasible and (2) if an optimal screw configuration is subject-specific.

METHODS

Validated subject-specific finite element models of 16 human radii with extra articular distal radius fractures and volar plate fixation with six distal screws were used as a baseline. 41 additional configurations with three to six distal screws were simulated for each subject. Axial stiffness and peri-implant strains around the distal screws were evaluated. Subject-specific optimum configurations were determined using a lower bound for the axial stiffness and minimizing peri-implant strains.

FINDINGS

Even using three distal screws led to only minor deterioration of the biomechanical properties in the best configuration (axial stiffness: -11.2%, peri-implant strains: -35.0%), but a considerable deterioration in the worst configuration (axial stiffness: -46.2%, peri-implant strains: +112.4%). The optimization showed that the ideal screw configuration is subject-specific and on average 1.9 screws could be saved based on the herein used optimization criterion.

INTERPRETATION

This study highlights that not only how many, but which screws are used in volar plate fixation of distal radius fractures is critical. Using a patient-specific selection of distal screws bears potential to save costs and reduce complications.

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.

Volar Locking Plate Fixation for Distal Radius Fractures by Intraoperative Computed Tomographic–Guided Navigation

Purpose

Unstable distal radius intra-articular fractures require restoration of alignment. Exact fixation of intra-articular fragments is ideal. Here, we employed intraoperative computed tomography (CT) navigation to insert screws accurately in the intra-articular dorsal fragments during treatment with a volar locking plate for distal radius intra-articular fractures. The main purposes of this study were to evaluate the accuracy of this procedure and the postoperative stability of the articular fragments through CT findings, as well as to assess clinical outcomes.

Methods

This study included 26 patients with distal radius fractures, who were treated with a volar locking plate using intraoperative CT navigation with a minimum follow-up of 12 months. Mean patient age was 63 years and mean follow-up was 16 months. We examined the position of the inserted distal screws and articular displacement on preoperative, intraoperative, and post–bone union CT images. The 3 distal ulnar screw positions that influence the stability of the dorsoulnar articular fragment were evaluated. The Mayo wrist score and Disabilities of the Arm, Shoulder, and Hand score were also clinically evaluated.

Results

Computed tomography evaluation revealed that the distal locking screws were appropriately inserted at the subchondral position, with sufficient length to stabilize the dorsal fragments, and reduction and stability of the articular fragment were acceptable. At the final follow-up, mean Mayo wrist score was 90.8 and mean Disabilities of the Arm, Shoulder, and Hand score was 9.6.

Conclusions

Intraoperative CT navigation was successfully used for volar locking plate fixation of intra-articular distal radius fractures. Computed tomography evaluation revealed that the screws were precisely inserted for articular fragments and bone union was achieved, maintaining good intra-articular alignment. The findings demonstrate the accuracy of volar locking plate fixation assisted by intraoperative CT navigation and the good clinical outcomes of this procedure.

Type of study/level of evidence

Therapeutic IV.

Effect of CT imaging on the accuracy of the finite element modelling in bone

The finite element (FE) analysis is a highly promising tool to simulate the behaviour of bone. Skeletal FE models in clinical routine rely on the information about the geometry and bone mineral density distribution from quantitative computed tomography (CT) imaging systems. Several parameters in CT imaging have been reported to affect the accuracy of FE models. FE models of bone are exclusively developed in vitro under scanning conditions deviating from the clinical setting, resulting in variability of FE results (< 10%). Slice thickness and field of view had little effect on FE predicted bone behaviour (≤ 4%), while the reconstruction kernels showed to have a larger effect (≤ 20%). Due to large interscanner variations (≤ 20%), the translation from an experimental model into clinical reality is a critical step. Those variations are assumed to be mostly caused by different “black box” reconstruction kernels and the varying frequency of higher density voxels, representing cortical bone. Considering the low number of studies together with the significant effect of CT imaging on the finite element model outcome leading to high variability in the predicted behaviour, we propose further systematic research and validation studies, ideally preceding multicentre and longitudinal studies.

Diaphyseal Screw Prominence in Distal Radius Volar Plating

Background  Volar plating for distal radius fractures has become common. Screw prominence on the dorsal side from long screws can lead to tendon injury. Methods for detecting screws that penetrate the far cortex involve X-ray or ultrasound. These have focused on the distal row of screws. No studies have addressed screw penetration in the diaphysis. We describe two cases where diaphyseal screws caused symptoms. We then insert screws in the diaphysis of synbones 2 mm longer than measured and determine what angle of pronation or supination was best to detect this on X-ray. Methods  Three synbones were plated using Synthes volar plate. The three diaphyseal screws were drilled perpendicular to the plate, and the depth measured. Cortical 2.4-mm screws were inserted, 2 mm longer than measured. The three synbones were then placed in a custom clamp to measure rotation. Lateral X-rays were taken at 0 degree rotation, and 5, 10, and 15 degrees of supination and pronation. The prominence of each screw was measured using the synapse digital ruler. Results  For the screws that were placed at a neutral angle (perpendicular to the plate) the maximum visualization of the prominent tips occurred around 0 degree rotation. With screws angled 15 degrees ulna, maximum visualization was between 5 and 10 degrees of pronation. With screws angled 15 degrees radial, maximum visualization was between 5 and 10 degrees of supination. Every 5 degrees of rotation changes the profile of the screw by 0.4 mm. Discussion  The diaphysis of the radius becomes approximately trapezoidal distally. Prominent screws that are placed below the "peak" of the trapezoid may appear to be the correct length. Rotating the wrist into pronation or supination to bring the relevant cortex as parallel to the X-ray beam as possible will help to identify if screws are of the correct length. Screws that are prominent in the second compartment may be particularly symptomatic as the tendons here are closely opposed to the bone. We recommend screening for 2 mm diaphyseal screw prominence in neutral, with 10 degrees of pronation and supination.

Three-Dimensional Characterization of Trabecular Bone Mineral Density of the Distal Radius Utilizing Quantitative Computed Tomography

Background: Distal radius (DR) fractures demonstrate patterns of predictable fragments. Bone mineral density (BMD) measurements of these regions of interest (ROIs) may guide more precise treatment. Methods: Computed tomography (CT) scans of the DR of 42 healthy volunteers (23 female) were analyzed using quantitative CT software, measuring BMD within trabecular bone. Seven ROIs were described by alignment with the distal (volar ulnar distal [VUD], dorsal ulnar distal [DUD], volar radial distal [VRD], and dorsal radial distal [DRD]) or proximal (middle ulnar proximal [MUP], middle proximal [MP], and middle radial proximal [MRP]) sigmoid notch. Additional ROIs were the radial styloid (RS) and metadiaphysis (MD). A general estimation equation assessed subject's BMDs with predictive factors of gender, ROI, and age. The interaction between gender, ROI, and age was included in the model to allow for differences in ROI to vary with gender and/or age. Results: Comparing ROIs within the same gender and, separately, within the same age group revealed significantly higher BMD adjacent to the radioulnar and radiocarpal joints. Male and female individuals aged ≥50 years (mean: 172.7 mg/cm³ ± 6.1) had significantly lower BMD than those aged <50 years (mean: 202.7 mg/cm³ ± 5.8) when all ROIs were considered. Males had higher mean BMD at each ROI compared with females; these differences were significant in 5 of the 9 ROIs: VUD, DUD, DRD, RS, MUP. Conclusions: Trabecular BMD of the DR is highest adjacent to the radioulnar and radiocarpal joints. Female patients and those ≥50 years have lower trabecular BMD.

Biomechanical considerations for strategies to improve outcomes following volar plating of distal radius fractures

This article is a systematic review of the recent published literature on the biomechanics of volar locking plate fixation of distal radius fractures. PUBMED/MEDLINE and EMBASE databases were searched on 13th Sep 2018. Biomechanical papers on volar locking plate fixation of distal radius fractures since 2010 were included. Papers were analysed and included studies were appraised by the author using the validated quality assessment GRADE tool. The search revealed 456 papers between January 2010 and the present day whose abstracts were reviewed for relevance and 21 papers were included for full paper review. The aim of this systematic review was to evaluate the evidence to determine the surgical techniques and strategies that are associated with the best biomechanical outcomes of volar plating for distal radius fractures. Review of the literature revealed that it was not necessary to fill all available distal locking screws, there was little evidence to support the use of 2 rows of screws distally over 1 row. Screws of 75% length of the distal cortex are sufficient to withstand standard postoperative regimes in extrarticular fractures. The was a paucity of evidence to conclude multidirectional locking plates were superior to fixed angle plates or that one brand of plate was superior to another.

Complications in the Management of Distal Radius Fractures: How Do We Avoid them?

PURPOSE OF THIS REVIEW

Distal radius fractures are one of the most common fractures in the upper extremity. The purpose of this review is to outline common complications that may arise when caring for distal radius fractures and to describe the treatment strategies when faced with such complications.

RECENT FINDINGS

Tendon complications are not uncommon after distal radius fractures. Recent literature highlights new plating technology for dorsal plating techniques. Moreover, new literature has outlined parameters for flexor tendon complications when using volar locking plates in an effort to avoid flexor tendon irritation and rupture. In summary, it is important to understand the various complications that can arise when treating distal radius fractures in an effort to avoid suboptimal outcomes.

Screw placement is everything: Risk factors for loss of reduction with volar locking distal radius plates

AIM

To determine factors correlated with postoperative radial shortening in patients with distal radius fractures treated with volar locking distal radius plates.

METHODS

A total of 250 patients with a distal radius fracture stabilised with volar locking plates between January 2010 and December 2014 were included in a multicentre retrospective cohort study. We measured the distance of the distal locking screws to the joint line immediately postoperatively and then measured radial shortening after six to eight weeks using the change in ulnar variance.

RESULTS

Multivariate linear regression analysis showed that there was a significant linear association between the distance of the screws from the joint line and radial shortening. No other patient, injury, or treatment-related characteristic significantly influenced radial shortening in multivariate analysis.

CONCLUSION

Distal locking screws should be placed as close as possible to the subchondral joint line to prevent postoperative loss of reduction.

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.

[Biomechanics of distal radius fractures : Basics principles and GPS treatment strategy for locking plate osteosynthesis]

Fractures of the distal radius are most commonly caused by hyperextension injuries of the wrist. Tensile forces and force vectors, strength of impact, bone strength and soft tissue tension create individually different fracture patterns. Metaphyseal comminution, loss of cortical support, ligament avulsion and shear fragments are defining parameters for fracture instability. The dislocation of the articular fragment follows the force vectors of the extrinsic forearm muscles bridging the joint. The goal-plan-standardized (GPS) treatment strategy has proven to be helpful in choosing the ideal individual treatment. It is based on individual patient demands on wrist function and an analysis of fracture instability in computed tomography (CT) scans. The "goal" is a realistic expectation assessed by patient and surgeon. The "plan" includes a benefit-risk analysis and selection of an appropriate treatment modality. The "standardized treatment" of surgical and follow-up treatment is based on biomechanical knowledge. Locking plate osteosynthesis aims to neutralize dislocating force vectors and to allow early active mobility. Unidirectional instability can be indirectly neutralized by palmar locking plate systems. A multidirectional instability can be addressed by multiple plating following the column theory. Distal shear and avulsion fractures may require a fragment-specific osteosynthesis approach.

The influence of bone density and anisotropy in finite element models of distal radius fracture osteosynthesis: Evaluations and comparison to experiments

Continuum-level finite element (FE) models can be used to analyze and improve osteosynthesis procedures for distal radius fractures (DRF) from a biomechanical point of view. However, previous models oversimplified the bone material and lacked thorough experimental validation. The goal of this study was to assess the influence of local bone density and anisotropy in FE models of DRF osteosynthesis for predictions of axial stiffness, implant plate stresses, and screw loads. Experiments and FE analysis were conducted in 25 fresh frozen cadaveric radii with DRFs treated by volar locking plate osteosynthesis. Specimen specific geometries were captured using clinical quantitative CT (QCT) scans of the prepared samples. Local bone material properties were computed based on high resolution CT (HR-pQCT) scans of the intact radii. The axial stiffness and individual screw loads were evaluated in FE models, with (1) orthotropic inhomogeneous (OrthoInhom), (2) isotropic inhomogeneous (IsoInhom), and (3) isotropic homogeneous (IsoHom) bone material and compared to the experimental axial stiffness and screw-plate interface failures. FE simulated and experimental axial stiffness correlated significantly (p<0.0001) for all three model types. The coefficient of determination was similar for OrthoInhom (R(2)=0.807) and IsoInhom (R(2)=0.816) models but considerably lower for IsoHom models (R(2)=0.500). The peak screw loads were in qualitative agreement with experimental screw-plate interface failure. Individual loads and implant plate stresses of IsoHom models differed significantly (p<0.05) from OrthoInhom and IsoInhom models. In conclusion, including local bone density in FE models of DRF osteosynthesis is essential whereas local bone anisotropy hardly effects the models׳ predictive abilities.