Biomechanics in uniaxial compression of three distal radius volar plates

Biomechanics of Subcutaneous Locked Plating Versus Burke Plate and External Fixator for Comminuted Distal Radius Fractures

Background External fixators that span the wrist have been the historical norm in treating distal radius fractures. We have modified a dorsal distraction approach by using a subcutaneously applied locked bridge plate through two small incisions superficial to the extensor tendons and outside the extensor compartment. The purpose of this study was to biomechanically evaluate this modified method of fixation for comminuted distal radius fractures in comparison with two established constructs. Methods Matched cadaver specimens were used to model an AO Type 23-C3 distal radius fracture. Biochemical testing for stiffness during axial compressive loading was done on three constructs: a conventional Burke distraction plate, the subcutaneous internal fixation plating technique, and an external fixator. All specimens were cyclically loaded for 3000 cycles and then retested. Results The modified construct was found to be stiffer than the external fixator (p=0.013). When compared to the Burke plate, the modified construct was significantly less stiff before axial cycling (p=0.025). However, the difference was not maintained after cycling, and the post-axial loading stiffness difference was non-significant (p=0.456). Conclusion Our data demonstrate the biomechanical integrity of the subcutaneous plating technique for the fixation of comminuted distal radius fractures. It is stiffer than an external fixator and has the theoretical advantage of avoiding pin-tract infections. In addition, it is subcutaneous and not a cumbersome external construct. Our construct is minimally invasive, and it does not violate the dorsal extensor compartments. This allows for finger movement even while the construct is in place.

In adults, early mobilization may be beneficial for distal radius fractures treated with open reduction and internal fixation: a systematic review and meta-analysis

Objectives

It remains debatable if early mobilization (EM) yields a better clinical outcome than the late mobilization (LM) in adults with an acute and displaced distal radial fracture (DRF) of open reduction internal fixation (ORIF). Therefore, we aimed to perform a systematic review and meta-analysis of randomized controlled trials (RCTs), comparing clinical results with the safety of EM with LM following ORIF.

Methods

Databases such as Medline, Cochrane Central Register, and Embase were searched from Jan 1, 2000, to July 31, 2021, and RCTs comparing EM with LM for DRF with ORIF were included in the analysis. The primary outcome of study included disabilities of the Arm, Shoulder, and Hand (DASH) score at different follow-up times. Wherever the secondary outcomes included patient-rated wrist evaluation (PRWE), grip strength (GS), visual analog scale (VAS), wrist range of motion (WROM), and associated complications, the two independent reviewers did data extraction for the analysis. Effect sizes of outcome for each group were pooled using random-effects models; thereafter, the results were represented in the forest plots.

Results

Nine RCTs with 293 EM and 303 LM participants were identified and included in the study. Our analysis showed that the DASH score of the EM group was significantly better than LM group at the six weeks postoperatively (− 10.15; 95% CI − 15.74 to − 4.57, P < 0.01). Besides, the EM group also had better outcomes in PRWE, GS and WROM at 6 weeks. However, EM showed potential higher rate for implant loosening and/or fracture re-displacement complication (3.00; 95% CI 1.02–8.83, P = 0.05).

Conclusion

Functionally, at earlier stages, EM for patients with DRF of ORIF may have a beneficial effect than LM. The mean differences in the DASH score at 6 weeks surpassed the minimal clinically important difference; however, the potentially higher risk of implant loosening and/or fracture re-displacement cannot be ignored. Due to the lack of definitive evidence, multicenter and large sample RCTs are required for determining the optimal rehabilitation protocol for DRF with ORIF.

PROSPERO registration number: CRD42021240214 2021/2/28.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-021-02837-0.

Biomechanical investigation of a novel hybrid dorsal double plating for distal radius fractures by integrating topology optimization and finite element analysis

BACKGROUND

Currently available dorsal locking plates for the treatment of distal radius fractures are far less then volar locking plates, and there is limited evidence about biomechanical strength of dorsal plates. The aim of this study is to develop a novel hybrid dorsal double plating, which enhance biomechanical strength in the articular fixation region and achieve the minimally invasive surgical technique requirement of distal radius fracture treatment by combining weighted topology optimization and finite element (FE) analysis METHODS: A dorsal template bone plate design (based on dorsal double plating (DDP)) was constructed to perform weighted topology optimization and FE analysis under six fracture models with 50%, 30%, and 20% weighting of the joint subjected to axial, bending, and torsion moments, respectively. A novel hybrid dorsal double plating (HDDP) was generated using the union of six single dorsal plates to subtract the intersection of the original template dorsal model. A 100 N axial load with 1 Nm bending and torsion moments were applied at the end of the distal radius onto six fracture FE models to investigate the biomechanical differences between the DDP and HDDP approaches.

RESULTS

Results of weighted topology optimization showed that the profile of the HDDP presented a "Y" shape. Simulation results showed that the bone plate stress values for the distal radius fractures fixed with HDDP was much smaller than those with DDP regardless of the type of bone fractures and load conditions. The maximum bone stress value of the DDP approach was much higher than that of HDDP when the distal radius was a complete sagittal articular fracture and partial articular fracture involving lunate fossa. The corresponding maximum bone stress values for different loads might be higher than the ultimate strength of bone (150  MPa) and induced the risk of future bone fractures.

CONCLUSIONS

It is concluded that the novel HDDP demonstrated better resistance to functional loads, provided sufficient screw fixation at the articular surface, and can be placed on the dorsal site of the distal radius through the standard dorsal approach to minimize invasive surgeries and eliminate tendon irritations.

Rehabilitation after distal radius fractures: is there a need for immobilization and physiotherapy?

Although the literature generally agrees that displaced distal radius fractures require surgery, no single consensus exists concerning the length of immobilization and type of post-operative physiotherapeutic rehabilitation program. Palmar locking plate fixation represents a very stable fixation of the distal radius, and was assessed biomechanically in various studies. Surprisingly, most authors report additional immobilization after plate fixation. One reason might be due to the pain caused during active wrist mobilization in the early post-operative stages or secondly to protect the osteosynthesis in the early healing stages preventing secondary loss of reduction. This article addresses the biomechanical principles, current available evidence for early mobilization/immobilization and impact of physiotherapy after operatively treated distal radius fractures.

Comparison of a standard locking screw versus a double-threaded cortical compression screw for fixation of die-punch fragments in distal radius fractures with volar plating

The aim of this study was to use a compression screw in the epiphyseal medial orifice of a volar plate to reduce and stabilize the die-punch fragment in distal radius fractures (DRF) undergoing open reduction and internal fixation (ORIF). The main hypothesis was that the range of motion (ROM) in supination would be poorer when a standard screw was used. Our case series included 19 patients with an average age of 59 years (24-91) (SD -35.32) (10 male patients and 9 females) who underwent ORIF of DRFs with a volar plate. Group I included 10 patients in which the die-punch fragment was fixed with a standard locking screw and group II included the 9 patients in which the die-punch fragment was fixed with an angle stable compression screw through both cortices. At the 6-month follow-up visit, the average ROM in flexion was 83% in group I and 81% in group II (-2.327 [-13.657; 8.960]), the ROM in extension was 91% and 89% (-2.754 [-13.410; 7.602]), the ROM in pronation was 100% and 102% (+3.178 [-5.242; 11.457]), the ROM in supination 100% and 97% (-3.171 [-10.825; 4.537]), the pain level was 0.6/10 and 1/10 (+0.106 [-0.809; 0.977]), the QuickDASH score was 8.1/100 and 17.17/100 (+5.790 [-2.934; 15.012]), the PRWE was 6.2/100 and 22/100 (+13.109 [4.416; 22.779]) and the grip strength was 95% and 74% of the contralateral side (-12.478 [-24.832; 0.538]). No complications, nonunions or revision surgery were reported in the two groups. One case of secondary displacement of the die-punch fragment occurred in each group. The main hypothesis was not proven. In conclusion, despite what several biomechanical studies have suggested, the use of double-threaded compression screws for die-punch fragment fixation in DRFs does not improve the clinical outcomes compared to standard locking screws.

Clinical outcomes after carbon-plate osteosynthesis in patients with distal radius fractures

Background

Surgical implant material has changed over time, from metal to stainless steel to titanium. In recent decades a new material, carbon-fibre-reinforced polyether ether ketone, has been introduced. The aim of this study was to assess the clinical and radiological feasibility and functional outcome after treatment of distal radius fractures with this new implant.

Methods

Inclusion criteria: AO type B distal radius fractures treated with 2.7 mm CF/PEEK plates at one Level 1 trauma centre between 2016 and 2017. Follow-up period 1 year, measurement of range of motion and radiographic assessment, histological analysis of debris only after plate removal.

Results

Out of 112 eligible patients, 10 (8.9%) patients were included. Mean operation time was 65 ± 10 min. Radiographic healing was confirmed by radiologists at 6 weeks follow-up. During one-year follow-up, no adverse events were reported and functionality and patients subjective satisfaction improved significantly (p < 0.05). Only one plate was removed, with no histological signs of inflammation or allergic reaction.

Conclusions

The 2.7 mm CF/PEEK plate osteosynthesis appears to be a reliable and safe implant for certain types of distal radius fracture. Assessment of fracture union is substantially more practical and functionality improved significantly over 1 year.

Biomechanical comparison between stainless steel, titanium and carbon-fiber reinforced polyetheretherketone volar locking plates for distal radius fractures

INTRODUCTION

As the popularity of volar locked plate fixation for distal radius fractures has increased, so have the number and variety of implants, including variations in plate design, the size and angle of the screws, the locking screw mechanism, and the material of the plates.

HYPOTHESIS

Carbon-fiber reinforced polyetheretherketone (CFR-PEEK) plate features similar biomechanical properties to metallic plates, representing, therefore, an optimal alternative for the treatment of distal radius fractures.

MATERIALS AND METHODS

Three different materials-composed plates were evaluated: stainless steel volar lateral column (Zimmer); titanium DVR (Hand Innovations); CFR-PEEK DiPHOS-RM (Lima Corporate). Six plates for each type were implanted in sawbones and an extra-articular rectangular osteotomy was created. Three plates for each material were tested for load to failure and bending stiffness in axial compression. Moreover, 3 constructs for each plate were evaluated after dynamically loading for 6000 cycles of fatigue.

RESULTS

The mean bending stiffness pre-fatigue was significantly higher for the stainless steel plate. The titanium plate yielded the higher load to failure both pre and post fatigue. After cyclic loading, the bending stiffness increased by a mean of 24% for the stainless steel plate; 33% for the titanium; and 17% for the CFR-PEEK plate. The mean load to failure post-fatigue increased by a mean of 10% for the stainless steel and 14% for CFR-PEEK plates, whereas it decreased (-16%) for the titanium plate. Statistical analysis between groups reported significant values (p<001) for all comparisons except for Hand Innovations vs. Zimmer bending stiffness post fatigue (p=.197).

DISCUSSION

The significant higher load to failure of the titanium plate, makes it indicated for patients with higher functional requirements or at higher risk of trauma in the post-operative period. The CFR-PEEK plate showed material-specific disadvantages, represented by little tolerance to plastic deformation, and lower load to failure.

LEVEL OF EVIDENCE

N/A.

Novel adhesives for distal radius fixation: A biomechanical analysis

Wrist fractures can be difficult to treat due to advanced age of the patient, medical co-morbidities, and comminution of the bone. This study examines the effectiveness of two injectable glass polyalkenoate cements (GPCs), derived from two different glasses (A and B), as minimally invasive treatments for distal radius fractures. Twenty-seven fresh cadaveric radial pairs were tested either in compressive fatigue or to quasi-static compressive failure. The radii tested to failure had one pair fixated with a GPC while the other was left intact. The radii tested under fatigue had one pair fixated with a GPC and the other with a volar locking plate. A wedge osteotomy was used to simulate a severely comminuted fracture. When loaded to failure, the radii fixated with a GPC made from glass A or B were found to be, respectively, at least 57% and 62% as strong as their intact biological pair (95% Confidence Interval, Lower). Using a paired t-test, the radii fixated with either adhesive were found to be significantly stiffer than their biological pairs fixated with a volar locking plate for all cycles of fatigue loading. The adhesives under investigation demonstrate promise as treatment for distal radius fractures. In vivo investigations are warranted to determine the effect that the adhesives have on the bone remodelling process.

Volar Locking Plate Fixation of Distal Radius Fractures: Splint versus Immediate Mobilization

Background  The goal of this study was to demonstrate that the use of a splint after performing an osteosynthesis of the distal radius with a volar locking plate is unnecessary. The main hypothesis was that postoperative flexion of the wrist was greater without a splint. Secondary hypothesis was that patients who were allowed immediate mobilization got better results in terms of pain, Quick Disabilities of the Arm, Shoulder and Hand (DASH), Patient-Rated Wrist Evaluation (PRWE), strength, extension, pronation, and supination. Case Description  Our series included 72 patients, aged 59 years in average of which 59 were female patients. All patients had been operated for a volar locking plate fixation of a distal radius fracture. The first 36 patients (group I) were immobilized by a splint at 30° of extension of the wrist for 2 weeks. The following 36 patients (group II) were not immobilized. Results  At 3 months, all the average variables were better in the group without splint (group I: flexion 74.83%, extension 83.13%, pronation 92.07%, supination 88.11%, pain 1.72/10, Quick DASH 21.78/100, PRWE 22.97/100, strength 62.96%; group II: flexion 85.50%, extension 83.4%, pronation 92.96%, supination 92.96%, pain 1.28/10, Quick DASH 19.57/100, PRWE 20.56/100, strength 66.34%). No complication was reported. Conclusion  Overall, our results demonstrate that wearing a splint after volar locking plate fixation of a distal radius fracture is unnecessary.

Comparison of Locking and Frag-Loc Screws for Fixation of Die-Punch Fragments

Background  The Frag-Loc (FL) compression screw system was designed to stabilize dorsally displaced intra-articular dorsoulnar (die-punch) fragments in distal radius fractures. Purpose  Comparison of the biomechanical properties of fixation of the die-punch fragment (stiffness, ultimate strength, and displacement ratio of the fragment), using the FL and traditional locking screw (LS), and using simulated distal radial fractures in cadaveric specimens under axial compressive loading. Both screws were used with a volar locking plate (VLP). Materials and Methods  Eight matched pairs of formalin-fixed cadaveric specimens of the radius were used to simulate distal radius fractures with die-punch fragments. The die-punch fragment was fixed using VLP with either FL group or LS group. Biomechanical properties for the two fixation systems were evaluated under axial compression loading, applied at a constant rate of 0.5 mm/min until failure. Load data were recorded and the ultimate strength and change in the gap between the die-punch and proximal fragments measured, with the displacement ratio calculated by dividing the value of the gap before loading by the gap after loading. Failure was defined as 10 mm or more of fragment displacement, or screw failure. Results  There were no differences in ultimate strength ( p  = 0.47) or stiffness ( p  = 0.061) between the two fragment fixation systems. However, the displacement ratio was lower for the FL than for the LS system ( p  = 0.049). Conclusion  Compared with LS, the FL system lowers the displacement of die-punch fragments under compressive loading. Clinical Relevance  The FL system is effective for the treatment of distal radius fractures with die-punch fragments.

Early Rehabilitation of Distal Radius Fractures Stabilized by Volar Locking Plate: A Prospective Randomized Pilot Study

Background Distal radius fractures are very common and an increased incidence of 50% is estimated by 2030. Therefore, both operative and postsurgical treatment remains pertinent. Main aim in treating intra-articular fractures is to restore the articular surface by internal fixation and early mobilization (EM). Questions/Purposes The purpose of this study was to compare functional results between EM immediately after surgery and 5 weeks of immobilization (IM). Patients and Methods In a randomized prospective study, 30 patients with an isolated distal radius fracture were treated by open reduction and internal fixation using a single volar locking plate excluding bone graft. Fifteen patients were randomized in the EM group and 15 in the IM group. At 6 weeks, 9 weeks, 3 months, 6 months, and 1 year postsurgery, range of motion, grip strength and X-rays were evaluated. Additionally, Quick Disability of the Arm, Shoulder and Hand (QuickDASH) questionnaire, Patient-Rated Wrist Evaluation (PRWE), modified Green O'Brien (Mayo) score, and pain according to the Visual Analog Scale score were analyzed. Results Patients in the EM group had a significantly better range of motion in the sagittal plane, in grip strength up to 6 months, in the frontal plane up to 9 weeks, and in forearm rotation up to 6 weeks. Also QuickDASH and PRWE scores were better up to 6 weeks postsurgery. The Green O'Brien score differed significantly up to 1 year. At 1 year, 93% "excellent" and "good" results in the Green O'Brien score with a mean QuickDASH of 5.98 ± 10.94 and PRWE score of 4.27 ± 9.23 were observed in the EM group. No differences regarding loss of reduction, pain, duration of physiotherapy, and sick leave were noted. Conclusion EM of surgically treated distal radius fractures (without bone graft) is a safe method for postoperative aftercare and leads to an improved range of motion and grip strength at 6 months postsurgery compared with an IM of 5 weeks. Level of Evidence This is a level Ib clinical study.

Impact of double-tiered subchondral support procedure with a polyaxial locking plate on the stability of distal radius fractures using fresh cadaveric forearms: Biomechanical and radiographic analyses

BACKGROUND

The present study compared the changes in biomechanical and radiographic properties under cyclic axial loadings between the 'double-tiered subchondral support' (DSS) group (wherein two rows of screws were used) and the 'non-DSS' (NDSS) group (wherein only one row of distal screws was used) using cadaveric forearm models of radius fractures fixed with a polyaxial locking plate.

MATERIAL AND METHODS

Fifteen fresh cadaveric forearms were surgically operated to generate an Arbeitsgemeinschaft für Osteosynthesefragen (AO) type 23-C2 fracture model with the fixation of polyaxial volar locking plates. The model specimens were randomized into two groups: DSS (n = 7) and NDSS (n = 8). Both the groups received 4 locking screws in the most distal row, as is usually applied, whereas the DSS group received 2 additional screws in the second row inserted at an inclination of about 15° to support the dorsal aspect of the dorsal subchondral bone. Cyclic axial compression test was performed (3000 cycles; 0-250 N; 60 mm/min) to measure absolute rigidity and displacement, after 1, 1000, 2000 and 3000 cycles, and values were normalized relative to cycle 1. These absolute and normalized values were compared between those two groups. Radiographic images were taken before and after the cyclic loading to measure changes in volar tilt (ΔVT) and radial inclination (ΔRI).

RESULTS

The DSS group maintained significantly higher rigidity and lower displacement values than the NDSS group during the entire loading period. Radiographic analysis indicated that the ΔVT values of the DSS group were lower than those of the NDSS group. In contrast, the fixation design did not influence the impact of loading on the ΔRI values.

CONCLUSIONS

Biomechanical and radiographic analyses demonstrated that two rows of distal locking screws in the DSS procedure conferred higher stability than one row of distal locking screws.

Distal radius fractures-Design of locking mechanism in plate system and recent surgical procedures

Recently, many studies have emphasized the importance of the comprehension of detailed functional anatomy of the distal forearm and wrist joint, and their biomechanics. A significant contribution which yields good functional outcomes of surgical treatment was the development of the locking plate technology; this technology has facilitated the improvement of the surgical technique for the fixation of fractures. This article reviews the locking mechanism and design of the fixation screws and plate, and the details of the surgical technique including the double-tired subchondral support procedure as it is applied to common fractures. Arthroscopic-assisted surgical procedures can be used to reduce the intra-articular fracture fragments after realignment of the distal radius with the locking plate. This technique is also useful at the time of fixation to assess soft tissue injury. The combination of arthroscopic-assisted reduction and locking plate fixation is now indicated for AO type C2 and C3 intra-articular comminuted fractures.

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

Background

Extensor tendon irritation is one of the most common complications following volar locking plate osteosynthesis (VLPO) for distal radius fractures. It is most likely caused by distal screws protruding the dorsal cortex. Shorter distal screws could avoid this, yet the influence of distal screw length on the primary stability in VLPO is unknown. The aim of this study was to compare 75 to 100 % distal screw lengths in VLPO.

Methods

A biomechanical study was conducted on 11 paired fresh-frozen radii. HRpQCT scans were performed to assess bone mineral density (BMD) and bone mineral content (BMC). The specimens were randomized pair-wise into two groups: 100 % (group A) and 75 % (group B) unicortical distal screw lengths. A validated fracture model for extra-articular distal radius fractures (AO-23 A3) was used. Polyaxial volar locking plates were mounted, and distal screws was inserted using a drill guide block. For group A, the distal screw tips were intended to be flush or just short of the dorsal cortex. In group B, a target screw length of 75 % was calculated. The specimens were tested to failure using a displacement-controlled axial compression test. Primary biomechanical stability was assessed by stiffness, elastic limit, and maximum force as well as with residual tilt, which quantified plastic deformation.

Results

Nine specimens were tested successfully. BMD and BMC did not differ between the two groups. The mean distal screw length of group A was 21.7 ± 2.6 mm (range: 16 to 26 mm), for group B 16.9 ± 1.9 mm (range: 12 to 20 mm). Distal screws in group B were on average 5.6 ± 0.9 mm (range: 3 to 7 mm) shorter than measured. No significant differences were found for stiffness (706 ± 103 N/mm vs. 660 ± 124 N/mm), elastic limit (177 ± 25 N vs. 167 ± 36 N), maximum force (493 ± 139 N vs. 471 ± 149 N), or residual tilt (7.3° ± 0.7° vs. 7.1° ± 1.3°).

Conclusion

The 75 % distal screw length in VLPO provides similar primary stability to 100 % unicortical screw length. This study, for the first time, provides the biomechanical basis to choose distal screws significantly shorter then measured.

Electronic supplementary material

The online version of this article (doi:10.1186/s13018-015-0283-8) contains supplementary material, which is available to authorized users.

Volar locking plate fixation of distal radius fractures: use of an intra-operative 'carpal shoot through' view to identify dorsal compartment and distal radioulnar joint screw penetration

INTRODUCTION

We report our experience using a 'carpal shoot through' view of the distal radius to identify dorsal compartment screw penetration intra-operatively when performing volar plating of the distal radius.

METHODS

A prospective study of 42 patients (mean age 56 years) with acute distal radius fractures treated with open reduction internal fixation was undertaken. Surgical fixation was performed using a volar locking plate in all patients. After plate application, inclined posteroanterior and lateral radiographs were taken followed by the carpal shoot through view.

RESULTS

In six cases (14 %), the carpal shoot through view revealed dorsal screw protrusion, which was not detectable on standard PA and lateral views. In one case, a screw had penetrated the distal radioulnar joint (DRUJ), which was only apparent on the shoot through view. The overall screw exchange rate was 17 %.

CONCLUSIONS

Using the hand and carpus to minimise the contrast in X-ray penetration, the dorsal cortex of the distal radius may be imaged intra-operatively and dorsal compartment screw penetration detected in cases with significant multifragmentation when screw measurement is difficult. This view potentially reduces the risk of post-operative pain and extensor tendon injury and also provides excellent visualisation of the DRUJ.

Polyaxial versus uniaxial volar locking plate for distal radial fractures

PURPOSE

To compare the penetration of the distal screws in relation to the thickness of the distal metaphysis in the polyaxial versus uniaxial volar locking plates.

METHODS

Records of 78 patients aged 16 to 79 years who underwent open reduction and internal fixation for distal radial fractures (n=81) were reviewed. All fracture subtypes were included. 20 men and 22 women aged 18 to 79 (mean, 50) years were treated with the uniaxial locking plate, whereas 15 men and 21 women aged 16 to 79 (mean, 51) years were treated with the polyaxial locking plate. The choice of plate was determined by the operating surgeon based on familiarity and perceived advantages of the 2 plates. Penetration of the distal locking screws in relation to the volar-dorsal thickness of the distal radial metaphysis was measured, and the percentage of subchondral bone unsupported by the screws calculated.

RESULTS

The mean percentage of unsupported subchondral bone was significantly lower in the polyaxial than uniaxial volar locking plate group (12% vs. 23%, p<0.001). No patient had screw over-penetration.

CONCLUSION

The polyaxial volar locking plate system enabled deeper insertion of distal screws into the subchondral bone, and thus providing better buttress for the fracture fragments.

Design optimisation and experimental evaluation of dorsal double plating fixation for distal radius fracture

This study determines the relative effects of changes in osteoporosis condition, plate/screw design factors (plate angle/length/width/thickness and screw diameter) and fixation methods (screw number and screw length) on the biomechanical response of dorsal double plating (DDP) fixation at a distal radius fracture to determine the optimal design and evaluate its biomechanical strength using the dynamic fatigue test. Eighteen CAD and finite element (FE) models corresponding to a Taguchi L18 array were constructed to perform numerical simulations to simulate the mechanical responses of a DDP fixed in a simply distal radius fracture bone. The Taguchi method was employed to determine the significance of each design factor in controlling bone/plate/screw stress and distal fragment displacement under axial (100 N), bending (1 N m) and torsion (1 N m) loads. Simulation results indicated that the order rank to determine the mechanical response was the plate thickness, plate width, screw diameter, and number of screws. Dorsal intermediate (L) plate with 60 mm length, 1.8 mm thickness, 6.0 mm width and 2.8 mm diameter, 20 mm length dual-thread locking screw can be found for optimisation. The DDP, including an L plate with 0°, 30° and 60° angles and a straight I plate, were made with Ti6Al4V to fix onto the sawbones with three corresponding radius fractures to perform the dynamic testing. The specimens were oscillated with loads between 10 N and 150 N at 5 Hz for 20,000 cycles. The average stiffness in 20,000 test cycles was 425.7 N/mm, 461.1 N/mm and 532.1N/mm for the 0°, 30° and 60° constructs, respectively. No difference in stiffness was found in the same angled constructs throughout the 20,000 cycles of testing (p > 0.05). Lack of gross construct failures during cyclic testing and reasonable stiffness corroborated that our new constructs tested to date seem stable enough to support restricted post-operative loads.

Volar plating for distal radius fractures--do not trust the image intensifier when judging distal subchondral screw length

BACKGROUND

The use of the volar plate to treat distal radius fractures is increasing but despite the theoretical advantages of a volar approach there have been reports of extensor tendon ruptures due to prominent screw tips protruding past the dorsal cortex. The valley in the intermediate column between Lister tubercle and the sigmoid notch of the distal radius makes it difficult to rely on fluoroscopy to judge screw length. Our aim was to quantify the dimensions of this valley and to demonstrate the danger of relying on intraoperative image intensification fluoroscopy to determine lengths of distal screws.

METHODS AND RESULTS

We measured the depth of this valley in the intermediate column of the distal radius in 33 patients with computed tomographic (9 patients) or magnetic resonance image (24 patients) scans of the wrist. There was a consistent valley in all images examined [average 1.8 mm (95% confidence interval, 1.6-2.0 mm)]. Thirty-nine percent of wrists had a valley depth of at least 2 mm.

CONCLUSIONS

Standard lateral views or rotation of the forearm to obtain oblique views does not identify prominent screw tips; and whatever the rotation of the forearm, screw tips protruding beyond dorsal cortex may look as if it is within the bone when in fact it is out. When drilling we suggest noting the depth at which the drill bit just penetrates dorsal cortex and routinely downsize the distal screw length by 2 mm. We caution against relying on flourosocopy when judging the length of the distal subchondral screws.

Biomechanical properties of fixed-angle volar distal radius plates under dynamic loading

PURPOSE

To evaluate and compare the biomechanical properties of 8 different locked fixed-angle volar distal radius plates under conditions designed to reflect forces seen in early fracture healing and postoperative rehabilitation.

METHODS

We evaluated the Acumed Acu-Loc (Acumed, Hillsboro, OR), Hand Innovations DVR (Hand Innovations, Miami, FL), SBi SCS volar distal radial plate (Small Bone Innovations, Morrisville, PA), Synthes volar distal radius plate and EA extra-articular volar distal radius plate (Synthes, Paoli, PA), Stryker Matrix-SmartLock (Stryker Leibinger, Kalamazoo, MI), Wright Medical Technology Locon VLS (Wright Medical Technology, Arlington, TN), and Zimmer periarticular distal radius locking plate (Zimmer, Warsaw, IN). After affixing each plate to a synthetic corticocancellous radius, we created a standardized dorsal wedge osteotomy. Each construct had cyclic loading of 100 N, 200 N, and 300 N for a total of 6000 cycles. Outcomes, including load deformation curves, displacement, and ultimate yield strengths, were collected for each construct.

RESULTS

The Wright plate was significantly stiffer at the 100 N load than the Zimmer plate and was stiffer at the 300 N load than 4 other plates. The Zimmer and Hand Innovations plates had the highest yield strengths and significantly higher yield strengths than the Wright, SBi, Stryker, and Synthes EA plates.

CONCLUSIONS

Given the biomechanical properties of the plates tested, in light of the loads transmitted across the native wrist, all plate constructs met the anticipated demands. It seems clear that fracture configuration, screw placement, cost, and surgeon familiarity with instrumentation should take priority in selecting a plating system for distal radius fracture treatment.

CLINICAL RELEVANCE

This study provides further information to surgeons regarding the relative strengths of different plate options for the treatment of distal radius fractures.

A NEW VARIABLE ANGLED LOCKING VOLAR PLATE SYSTEM FOR COLLES' FRACTURE: OUTCOME STUDY AND TIME-COURSE IMPROVEMENT OF OBJECTIVE CLINICAL VARIABLES

Our purposes were to report the radiographic outcomes and complications of patients with Colles' fracture treated with the Nakashima locking volar plate system (variable angled distal screw locking mechanism) prospectively and to report the results of objective clinical variables such as grip strength and range of motion of the wrist prospectively at up to one year. This study consisted of eight men and 32 women for analysis of radiographic parameters (volar tilt, radial inclination and radial length) and complications. Radiographic parameters were measured pre-operatively, immediately post-operatively and at final follow-up visit. The average age at operation was 60.3 years old. Among them, we selected 25 cases (6 men and 19 women) whom we followed up at six weeks, three months, six months and one year post-operatively. The average age at operation in this group was 62 years old. We measured objective clinical variables (grip strength, forearm rotation, wrist extension/flexion) at each visit. Except for volar tilt, radiographic parameters revealed no significant changes between immediately post-operative radiographs and radiographs at final follow-up visit. Complications included loss of reduction in two cases. Objective clinical variables other than pronation measurement showed significant increase at each visit up to one year post-operatively. Satisfactory clinical and radiographic results were obtained by using this system. The variable angled distal fragment plating system appears to be a reliable construct for rigid fixation of Colles' fractures; however, technical errors can occur, as with other fixation systems. We demonstrated that the follow-up of Colles' fracture treated by our volar locking plate less than one year post-operative may be insufficient.

Clinical results of volar locking plate for distal radius fractures: conventional versus minimally invasive plate osteosynthesis

OBJECTIVES

The purpose of this study was to compare the postoperative radiologic and clinical outcomes of conventional plate osteosynthesis (C) with minimally invasive plate osteosynthesis (M) using a transverse skin incision without cutting the pronator quadratus muscle for distal radius fractures.

DESIGN

Retrospective consecutive cohort with prospective data collection.

SETTING

One community teaching hospital. Surgical treatment was performed by a single surgeon.

PATIENTS

Sixty-six patients (C group, 36; M group, 30) underwent open reduction and internal fixation of dorsally displaced distal radius fractures with the volar locking plating system from June 2006 to August 2008. Their mean age was 63.5 years and the mean follow-up period was 22.7 months.

MAIN OUTCOME MEASURES

Radiologic parameters (volar tilt, radial inclination, ulnar variance), range of motion, grip strength, and Disability of the Arm, Shoulder, and Hand score were evaluated at each examination. The visual analog scale of wrist pain and evaluations of cosmetic problems were assessed at the final follow-up.

RESULTS

The groups did not differ significantly in all main outcomes. In the M group, the mean values of the Disability of the Arm, Shoulder, and Hand score at 2 weeks postoperatively (P = 0.06) and visual analog scale (P = 0.07) were lower and the mean value of the patient's satisfaction score of cosmetic problems (P = 0.08) was higher than those in the C group, but no statistically significant differences were apparent in these values.

CONCLUSION

No significant differences were found between the minimally invasive plate osteosynthesis and conventional plating for distal radius fractures based on the data from postoperative radiologic and clinical outcomes.

Efficacy of radial styloid targeting screws in volar plate fixation of intra-articular distal radial fractures: a biomechanical study in a cadaver fracture model

Background

The locking screws target the radial styloid, theoretically provide greater stability against radial styloid fragment. However, it is unknown whether the radial styloid locking screws increased the stability of the volar plating system fixation along the entire distal radius or not. In this study, we evaluated the stability of the volar plating system fixation with or without the radial styloid screws using a biomechanical study in a cadaver fracture model.

Methods

Six matched pairs of fresh-frozen human cadaver wrists complete from the proximal forearm to the metacarpal bones were prepared to simulate standardized 3-part intra-articular and severe comminuted fractures. Specimens were fixed using the volar plating system with or without 2 radial styloid screws. Each specimen was loaded at a constant rate of 20 mm/min to failure. Load data was recorded and, ultimate strength and change in gap between distal and proximal fragments were measured. Data for ultimate strength and screw failure after failure loading were compared between the 2 groups.

Results

The average ultimate strength at failure of the volar plate fixation with radial styloid screws (913.5 ± 157.1 N) was significantly higher than that without them (682.2 ± 118.6 N). After failure loading, the average change in gap between the ulnar and proximal fragment was greater than that between the radial and proximal fragment. The number of bent or broken screws in ulnar fragment was higher than that in radial fragment. The number of specimens with bent or broken screws in cases with radial styloid screws was fewer than that in the fixation without radial styloid screws group.

Conclusion

The ulnar fragment is more intensively stressed than the radial fragment under axial loading of distal radius at full wrist extension. The radial styloid screws were effective in stable volar plate fixation of distal radial fractures.

Influence of screw diameter and number on reduction loss after plating of distal radius fractures

BACKGROUND

The current options for plate-screw combinations in volar locking distal radius plates used for the treatment of distal radius fractures are either plates with a single distal screw row or plates with multiple distal screw rows. Additionally, the screws themselves may have either fixed angle locking or polyaxial locking mechanisms. To date, there is no evidence or consensus regarding the optimal plate-screw combination. The aim of this study was to assess the biomechanical behaviour of different plate-screw combinations with respect to total distal screw number, number of distal screw rows and screw projection surface area of the most distal row.

METHODS

Biomechanical study to assess six different plating configurations in five different volar locking plate models in a Sawbone distal radius fracture model. The specimens were loaded with 800 Newton loads for 2.000 cycles at 1 Hz. After cyclic loading, load-to-failure testing was performed.

RESULTS

  With cyclical testing, there was a significant and positive correlation between rigidity and a greater projection area of the most distal screws. Dorsal tilting was significantly more pronounced in plate models with a lesser projection area of the most distal screws and a smaller number of distal screws. With load-to-failure testing, there was a significant increase in rigidity with increasing screw projection area of the most distal row and total number of distal screws.

CONCLUSIONS

Additional distal screw rows in volar locking distal radius plates might not add substantially to resistance against loss of reduction in the post-operative period.

Stability of volar locking plate systems for AO type C3 fractures of the distal radius: biomechanical study in a cadaveric model

BACKGROUND

The purpose of the present study was to compare the relative stability of five volar locking plates (all of which are available for the treatment of intraarticular fractures of the distal radius) under loading conditions simulating the physiological forces that occur during early active mobilization.

METHODS

Five plating techniques were applied to surgically simulated AO type C3.2 distal radius fractures in formalin-fixed cadavers. The specimens were tested with a servohydraulic materials testing machine with 250 N of axial compression load for 3000 cycles. After cyclic loading, the specimens were loaded until they demonstrated failure in axial compression. The five fixation systems studied included a DRV locking plate (group 1), a Stellar plate (group 2), an Acu-Loc plate (group 3), AO Locking Distal Radius System 2.4 (group 4); and a Matrix SmartLock plate (group 5).

RESULTS

None of the plate fixations tested failed during the cyclic loading. Group 2 had a higher elastic limit than groups 4 and 5. There were no significant differences among the five groups for the failure load. Failure occurred at the distal portion of the fixation system, at the ulnar side locking pin, or the locking screw was bent (groups 1, 2, 3); the ulnar side locking screw was broken (groups 3, 4); the locking screw became loose (group 4); and the ulnar side locking screw was uncoupled from the screw hole (group 5).

CONCLUSIONS

All of the five volar plate fixation systems provided sufficient stability to permit 3000 repeated motions of the digits after surgery for AO type C3 distal radius fractures.

Comparison of functional outcome after volar plate fixation with 2.4-mm titanium versus 3.5-mm stainless-steel plate for extra-articular fracture of distal radius

PURPOSE

Open reduction and locked volar plate and screw fixation is a popular treatment method for extra-articular distal radius fractures with dorsal metaphyseal comminution. In this study, we compared the use of a titanium 2.4-mm precontoured plate with that of a stainless-steel oblique 3.5-mm T-shaped plate to test the null hypothesis that there would be no difference in wrist function or upper extremity-specific health status in the internal fixation of AO-type A3.2 distal radius fractures.

METHODS

We retrospectively analyzed 24 patients treated with a 2.4-mm titanium plate and 38 patients treated with a 3.5-mm stainless-steel plate for an extra-articular and dorsally angulated distal radius fracture, from data gathered in a prospective cohort study of plate and screw fixation of distal radius fractures. The 2 cohorts were analyzed for differences in motion, grip strength, pain, Gartland and Werley score, Disabilities of the Arm, Shoulder, and Hand score, and Short Form-36 score at 6, 12, and 24 months of follow-up. Group differences and their change over time were determined using regression analysis and the likelihood ratio test.

RESULTS

There were no significant differences in wrist function and arm-specific health status between patients treated with a 2.4-mm plate and those treated with a 3.5-mm plate at 6, 12, or 24 months of follow-up. However, we observed a trend toward greater wrist flexion at 1 year (66 degrees vs 55 degrees ; p=.07) and greater flexion-extension arc (137 degrees vs 123 degrees ; p=.08) and pronation-supination arc (172 degrees vs 160 degrees ; p=.07) at 24 months after surgery in patients treated with a 2.4-mm plate.

CONCLUSIONS

Patients with a dorsally angulated extra-articular distal radius facture can expect similar results when treated with either a precontoured 2.4-mm titanium plate or a 3.5-mm stainless-steel T-shaped plate.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic III.

The effect of an associated ulnar styloid fracture on the outcome after fixation of a fracture of the distal radius

A total of 118 consecutive patients with a fracture of the distal radius were treated with a volar locking plate; 50 patients had no ulnar styloid fracture, 41 had a basal ulnar styloid fracture, and 27 had a fracture of the tip of the ulnar styloid. There were no significant differences in radiological and clinical results among the three groups. The outcome was good and was independent of the presence of a fracture of the ulnar styloid. A total of five patients (4.2%) had persistent ulnar-sided wrist pain at final follow-up. Nonunion of the ulnar styloid fracture did not necessarily lead to ulnar wrist pain. Patients with persistent ulnar pain had a higher mean initial ulnar variance and increased post-operative loss of ulnar variance.

The presence of an associated ulnar styloid fracture of the ulnar styloid does not adversely affect the outcome in patients with a fracture of the distal radius treated by volar plating.

Does a volar locking plate provide equivalent stability as a dorsal nonlocking plate in a dorsally comminuted distal radius fracture?: a biomechanical study

OBJECTIVES

The purpose of this study was to compare the fixation afforded by a dorsal nonlocking plate with a volar locking plate in a fracture model simulating an extra-articular distal radius fracture with dorsal comminution (OTA [Orthopaedic Trauma Association] type 23-A3.2).

METHODS

In 10 matched pairs of fresh-frozen cadaveric arms, a comminuted extra-articular dorsally unstable distal radius fracture (OTA type 23-A3.2) was created. The fractures were fixed with either dorsally placed nonlocking T-plate or volarly placed locking plate within matched pairs. The precycling stiffness with axial and torsional loading of the specimens was determined. The specimens were then loaded axially for 5000 cycles, and postcycling axial and torsional stiffness and load to failure were determined.

RESULTS

The mean axial and torsional stiffness before and after cyclic loading of fractures stabilized with dorsal nonlocking plate was not significantly different than fractures fixed with volar locking plate. Although the mean load to failure was greater for the volar locking plate group than dorsal nonlocking plate group, the difference was not significant.

CONCLUSIONS

This study suggests that the fixation obtained with volar locking plates is as stable as fixation with a dorsal plate in acute healing period and can withstand the functional demands of the immediate postoperative period in dorsally comminuted unstable extra-articular distal radius fractures. Elimination of dorsal tendinopathy by using volar locking plates may lead to fewer long-term complications. Locking plates provided better stability in specimens with osteoporosis.

Malunited fractures of the distal radius treated with corrective osteotomy using volar locking plate and a corticocancellous bone graft following immediate mobilisation

We describe our experience of using a volar locking plate for corrective osteotomy and bone grafting combined with early mobilisation in the treatment of distal radius malunions. Corrective osteotomy of the distal radius was performed through a volar approach, and fixated by a volar locking plate associated with corticocancellous iliac bone grafting in three patients aged 16, 71 and 75 years. Two patients had had volarly displaced malunion and one dorsally displaced malunion. Wrist motion was started immediately after surgery. The average follow-up was 15 months (range, 12-20 months). All osteotomies healed at an average 5.7 weeks post-operatively, resulting in a total arc of wrist motion of 133 degrees, forearm rotation of 167 degrees, and grip strength of 70% of that of the contralateral side. This treatment method proved to be effective and safe.

Precontoured fixed-angle volar distal radius plates: a comparison of anatomic fit

PURPOSE

To compare distal radius volar fixed-angle plates for anatomic fit.

METHODS

Twenty embalmed radii were stripped of soft tissues. The volar lip (watershed line) on the volar distal radius served as a reference line. Seven volar fixed-angle plates were tested (Acumed Acu-loc Standard, Hand Innovations DVRAW and DVRAN, Synthes Juxta-articular [JA], Synthes Extra-articular [EA], Trimed Volar Bearing, Zimmer Volar Lateral Column). Four parameters of anatomic fit were studied: (1) site of best fit; (2) percent plate contact; (3) pin-subchondral bone distance; and (4) extraosseous penetrations. The Wilcoxon signed rank test and Pearson's correlation coefficient were used to compare interobserver plate placement. A Kruskal-Wallis analysis of variance was used to compare percent plate contact and pin-subchondral bone distance across all plates. The Bonferroni correction for multiple comparisons was used to compare pin-subchondral bone distances for all possible plate combinations.

RESULTS

There was no difference between observers for plate placement. Each plate had a specific site of best fit, and the 7 plates varied widely in best fit location. Percent contact (range, 3% to 6%) between plates was significantly different. Pin-subchondral bone distance across all plates was significantly different. Analysis of all possible plate combinations showed that the Synthes EA pin-subchondral bone distances were significantly different than those of all plates except Zimmer. Amongst the 140 plate insertions, the radiocarpal joint was penetrated in 17, the styloid in 7, (with 6 associated with the DVRAW plate), and the distal radioulnar joint in 9 (all associated with the DVRAW plate).

CONCLUSIONS

There was considerable variation in ideal plate location among the 7 plates tested. Total contact was minimal for all plates tested. The Synthes EA pin-subchondral bone distance was significantly greater than those of other plates tested. Joint penetration was relatively common, necessitating use of fluoroscopy and proper plate width.

Volar plating of AO C3 distal radius fractures: biomechanical evaluation of locking screw and locking smooth peg configurations

PURPOSE

The goal of this study was to determine whether locking screws or smooth locking pegs optimize fixation of AO C3 intra-articular distal radius fractures. A secondary goal was to determine which combinations of locking screws and smooth locking pegs influence construct stability.

METHODS

In anatomic radius models, AO C3 intra-articular distal radius fractures were fixed using volar locking plates. For the first part, 16 specimens were randomized to receive either 2 locking screws or 2 smooth locking pegs in each of the 3 pairs of holes in the plate. For the second part, 30 specimens were randomized to receive any 4 combinations of locking screws and smooth locking pegs in each of the 3 pairs of holes. Axial loading to failure was applied.

RESULTS

Constructs consisting of 4 smooth locking pegs within the lunate fragment were significantly weaker than constructs with 4 locking screws (means 626 N vs 981 N, respectively). Constructs with smooth locking pegs in the ulnar positions of the lunate fragment were weaker than with locking screws in these positions (means 737 N vs 977 N, respectively). Locking screws in the subchondral position of the lunate fragment were stronger than smooth locking pegs in these positions (means 1,227 N vs 934 N, respectively) and any other combination (means 1,227 N vs 942 N, respectively).

CONCLUSIONS

Use of locking screws as opposed to smooth locking pegs for AO C3 intra-articular distal radius fractures, particularly subchondral and in the ulnar side of the lunate fragment, optimizes construct stability. This may have implications on postoperative rehabilitation protocols and may limit costs related to use of volar locking plates.

Biomechanical comparison of different volar fracture fixation plates for distal radius fractures

The purpose of this study was to compare the biomechanical properties of four volar fixed-angle fracture fixation plate designs in a novel sawbones model as well as in cadavers. Four volar fixed angle plating systems (Hand Innovations DVR-A, Avanta SCS/V, Wright Medical Lo-Con VLS, and Synthes stainless volar locking) were tested on sawbones models using an osteotomy gap model to simulate a distal radius fracture. Based on a power analysis, six plates from each system were tested to failure in axial compression. To simulate loads with physiologic wrist motion, six plates of each type were then tested to failure following 10,000 cycles applying 100N of compression. To compare plate failure behavior, two plates of each type were implanted in cadaver wrists and similar testing applied. All plate constructs were loaded to failure. All failed with in apex volar angulation. The Hand Innovations DVR-A plate demonstrated significantly more strength in peak load to failure and failure after fatigue cycling (p value < 0.001 for single load and fatigue failure). However, there was no significant difference in stiffness among the four plates in synthetic bone. The cadaveric model demonstrated the same mode of failure as the sawbones. None of the volar plates demonstrated screw breakage or pullout, except the tine plate (Avanta SCS/V) with 1 mm of pullout in 2 of 12 plates. This study demonstrates the utility of sawbones in biomechanical testing and indicates that volar fixation of unstable distal radius fractures with a fixed angle device is a reliable means of stabilization.

Prospective study of distal radius fractures treated with a volar locking plate system

PURPOSE

To prospectively determine the results of treatment of distal radius fractures with a volar locking plate system with no bone graft and early mobilization.

METHODS

Internal fixation and early mobilization of dorsally displaced, unstable fractures of the distal radius using a volar locking plate system without bone grafting was investigated in a prospective series of 49 fractures in 49 consecutive patients. All patients were allowed to move the wrist joint immediately after surgery. Physical examination at 5 weeks, 3 months, 6 months, and 1 year after the operation were performed. Radiographic parameters on preoperative, postoperative, and 1-year postoperative radiographs were compared. At 1-year review, the final clinical functions were evaluated with the Gartland and Werley functional scoring system, a modified Green and O'Brien system, and the Disabilities of the Arm, Shoulder, and Hand questionnaire.

RESULTS

The average radiographic results at 1 year were 9 degrees of volar tilt; 22 degrees of radial inclination; 1 mm of ulnar variance, and 0 mm of articular incongruity. At 1-year review, an excellent or good result was found according to the system of Gartland and Werley and a modified Green and O'Brien system with scores of 100% and 98%, respectively. The Disabilities of the Arm, Shoulder, and Hand score averaged 6, indicating a high degree of patient satisfaction. There were no cases of infection, complex regional pain syndrome, tendon rupture, tendon irritation, nerve injury, or implant failure.

CONCLUSIONS

The volar locking plate fixation without bone grafting and early mobilization is a safe and effective treatment for dorsally displaced, unstable fractures of the distal radius.

Biomechanical characteristics of nonbridging external fixators for distal radius fractures

PURPOSE

Nonbridging external fixation is becoming popular for distal radius fractures, although its biomechanical characteristics have not been documented. This study evaluated the biomechanical characteristics of nonbridging external fixators for distal radius fractures.

METHODS

We tested 3 currently available nonbridging fixators (F-Wrist fixator, Hoffman II Compact, and Pennig Dynamic Wrist Fixator) and determined their relative stiffness under axial compression, torsion, and bending moments (dorsal, volar, radial, and ulnar aspects) using a uniform unstable distal radius fracture model. The contact pressure and its total load on the fracture plane were also measured to evaluate the mechanical stimuli at the stable fracture site using a pressure-sensitive conductive rubber sensor.

RESULTS

Differences were observed in the stiffness: the Pennig fixator was the stiffest, whereas the F-Wrist fixator was the least rigid. The total load transmitted from the wrist joint to the fracture plane depended on the fixator stiffness in axial compression.

CONCLUSIONS

By determining the biomechanical characteristics of nonbridging external fixators, these data may help the clinician when deciding on a particular device for nonbridging external fixation.

Biomechanical evaluation of volar locking plates for distal radius fractures

PURPOSE

Fixed-angle devices have been a major advancement in orthopedic fracture care and have become an attractive option for fixation of distal radius fractures. Several volar locking plates exist, but there is insufficient literature comparing the strengths of these plates. This study compares the biomechanical strength of two popular volar locking plate systems (Synthes LCP and Hand Innovations DVR-A) along with a nonlocking volar T-plate (Synthes).

METHODS

Twenty-three formalin-fixed cadaveric forearms were divided into three groups with similar ages and bone densities. An unstable extra-articular fracture was created using a standardized osteotomy. Each group was fixed with one of the three plates. Each specimen was loaded in axial compression for 2000 cycles at a force of 400 N. Each specimen that completed cyclic testing was loaded to failure. Stiffness, yield point, and ultimate strength were recorded for each construct.

RESULTS

Each fixed-angle construct completed all 2000 cycles. The nonlocking plates failed at an average of 560 cycles. The mean stiffness of the DVR-A, LCP, and the volar T-plates were 277.00, 343.17, and 175.67 N/mm, respectively. There was a statistically significant difference between both fixed-angle plates and the nonlocking plate (p < 0.05). The difference between each fixed-angle construct did not reach significance. Yield point and ultimate strength could only be determined for the two fixed-angle devices. There was no statistically significant difference between the constructs for both yield point (DVR-A = 855.56 N, LCP = 894.15 N) and ultimate strength (DVR-A = 1,021.97 N, LCP = 1,114.87 N).

CONCLUSIONS

Given our data, fixed-angle constructs withstand cyclical loading representing normal physiologic forces encountered during post-operative rehabilitation. There was no significant biomechanical difference between the two fixed-angle constructs. Our results support that volar fixed-angle locking plates are an effective treatment for unstable extra-articular distal radius fractures, allowing early postoperative rehabilitation to safely be initiated.

A comparative study of clinical and radiological outcomes of dorsally angulated, unstable distal radius fractures in elderly patients: intrafocal pinning versus volar locking plating

PURPOSE

To compare the clinical and radiological outcomes of intrafocal pinning (IFP) and volar locking plating (VLP) of dorsally angulated, unstable distal radius fractures in elderly patients.

METHODS

The subjects were 62 consecutive patients over 60 years of age with dorsally angulated, unstable distal radius fractures treated with IFP or VLP. Bone mineral density (BMD) of the lumbar spine was measured by dual-energy x-ray absorptiometry at first examination. The range of motion and grip strength were measured at follow-up examinations, and ulnar variance (UV) was measured on radiographs at baseline and follow-up postoperative examinations.

RESULTS

There were no notable differences in gender, age, follow-up period, baseline UV, BMD, and AO classification between IFP and VLP groups. There was no difference between the UV in VLP immediately after surgery and at the final follow-up examination; however, IFP showed a significant loss of reduction as measured by UV. In patients with UV more than 5 mm or BMD less than 70% of young adult mean (YAM) at first examination, UV increased again at the final follow-up examination in IFP, while surgically corrected UV was maintained in VLP, independent of the degree of baseline UV and BMD. VLP resulted in earlier recovery of postoperative range of motion and grip strength compared with IFP. The range of flexion and the grip strength value were significantly larger in VLP at final examination.

CONCLUSIONS

VLP, but not IFP, can maintain surgically corrected UV in distal radius fractures, independent of the degrees of initial UV and BMD. VLP enhances earlier recovery in range of motion and grip strength than IFP.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic II.

Volar versus dorsal fixed-angle fixation of dorsally unstable extra-articular distal radius fractures: a biomechanic study

PURPOSE

To evaluate and compare the biomechanic rigidity and strength of 3 fixed-angle plates used to treat extra-articular distal radius fractures that are dorsally unstable. Volar fixed-angle plates were compared with a dorsal fixed-angle nail plate.

METHODS

Three plate constructs were tested: the dorsal nail plate (DNP), distal volar radius (DVR) plate, and locking compression plate (LCP) volar distal radius plate. With anatomic, third-generation, artificial composite radii, dorsally unstable extra-articular distal radius fracture models were made by cutting a wedge osteotomy with an 8-mm dorsal gap 1 cm from the articular surface. These models were then fixed with the 3 implants by the method recommended by the manufacturer. The proximal radii of each specimen were attached to the base of a materials testing machine with a probe centered at the radial side of the lunate fossa. The specimens were loaded at a constant rate to failure under axial compression. Load and displacement were plotted graphically, and the resulting rigidities and strengths of each plate were assessed statistically.

RESULTS

The DVR group had significantly greater stiffness than the LCP group. The DVR group had significantly higher maximum loads than both the DNP and LCP groups. There were no significant differences in yield loads. Both the DNP and DVR groups had significantly less displacement at yield than the LCP group.

CONCLUSIONS

These 3 groups had similar yield loads. However, the LCP was less stiff than the DVR and had more displacement at yield than both the DVR and DNP. The yield load of all 3 implants was much higher than previously described loads for active wrist and finger motion.

Biomechanical evaluation of the modified double-plating fixation for the distal radius fracture

BACKGROUND

Distal radius fracture is among the most common type of skeletal injuries. To conquer the surgical and biomechanical complications of the most-frequent used double-plating operation for this fracture, modified double-plating technique was proposed in this study. The aim of this study was to investigate the biomechanical interactions of double-plating, modified double-plating and traditional single plating fixations coupled with various load conditions using nonlinear finite element analysis.

METHODS

A three-dimensional finite element distal radius fracture model with three fixation methods (double-plating, modified double-plating and single) was generated based on computer tomography data. After model verification and validation, frictional (contact) elements were used to simulate the interface condition between the fixation plates and the bony surface. The rigidity, stress values and displacements at the radius end were observed under axial, bending and torsion load conditions.

FINDINGS

The simulated results showed that the modified double-plating model demonstrated the highest rigidity and the least displacement among the three techniques in bending, but not in axial compression (similar results across the three) and torsion (modified double-plating technique possessed lowest rigidity). The maximum von Mises stress for bone was lower in modified double-plating model as well. These results indicated that modified double-plating technique demonstrated a better structural strength against bending with the least potential of fracture fragments and screw loosening.

INTERPRETATION

Although a lower torsional rigidity, modified double-plating technique was a better choice in distal radius fracture fixation since the bending force, which has the potential to separate the fracture ends, is more detrimental in hindering fracture healing.

Biomechanical comparison of fixed-angle volar plate versus fixed-angle volar plate plus fragment-specific fixation in a cadaveric distal radius fracture model

PURPOSE

To test the hypothesis that combining orthogonal fragment-specific fixation with volar fixed-angle fixation provides markedly higher interfragment stability and construct strength compared with volar fixed-angle fixation alone.

METHODS

Eight matched pairs of fresh cadaveric hand and forearm specimens were potted upright in cement. Flexor and extensor tendons were isolated at insertion sites and sutured into a looped bundle for loading in flexion and extension, respectively (up to 61 N). Osteotomies to simulate an AO type C2, 3-part fracture pattern were created with a saw. One randomized specimen from each pair received a locking volar plate and a radial pin plate (VP+PP), and the other received a locking volar plate only (VP). The relative angular displacements between the radial, ulnar, and proximal fragments were obtained with a motion analysis system. After stability tests, specimens were compressed to failure in a wrist-extended position on a material testing machine. Paired t tests were used to compare the interfragment displacement, construct stiffness, and strength between the 2 groups.

RESULTS

Comparing fragment displacement in the VP+PP and VP groups showed that with flexion-extension and radial-ulnar deviation, distal fragment displacement was reduced to a statistically significant degree. The VP+PP group also showed higher failure strength and construct rigidity than the VP group.

CONCLUSIONS

In a simulated cadaveric model of the distal radius intra-articular fracture, the combined technique of fragment-specific plating with volar fixed-angle fixation alone provides superior biomechanical strength and stability over the volar fixed-angle fixation alone.

Volar versus dorsal locking plates with and without radial styloid locking plates for the fixation of dorsally comminuted distal radius fractures: A biomechanical study in cadavers

PURPOSE

To compare the stability and stiffness of dorsal and volar fixed-angle distal radius constructs in a cadaveric model.

METHODS

A locking distal radius system was used in a combination of a dorsal and styloid plate (group 1), a single volar plate (group 2), and a combination of a volar and styloid plate (group 3) configuration. In addition a single volar 3.5-mm steel locking plate was used in group 4. Each construct was tested on 6 fresh-frozen radii with simulated unstable dorsally comminuted extra-articular distal radius fractures. Specimens were tested on a material testing machine with an extensometer and subjected to axial compression fatigue and load-to-failure testing.

RESULTS

No construct failed in fatigue testing of 250 N for 5,000 cycles. Two specimens in each group were tested for 20,000 cycles without failure. The plastic deformation in the double-plate groups was lower compared with the single-plate groups, although the difference was not statistically significant. Group 1 had the highest and group 4 the lowest failure load and stiffness, respectively. The differences between group 1 and the other groups, except failure load compared with group 3, were statistically significant. Groups 2 and 3 had a significantly higher load to failure and group 3 had a significantly higher stiffness compared with group 4.

CONCLUSIONS

All constructs offer adequate stability with minimal deformation on fatigue testing under physiologic conditions. Dorsal fixed-angle constructs are stiffer and stronger than volar constructs. The addition of a styloid plate to a volar plate did not significantly improve stability in this model of simulated extra-articular dorsal comminution loaded in axial compression.

Delayed ruptures of the extensor tendon secondary to the use of volar locking compression plates for distal radial fractures

The use of volar locking compression plates for the treatment of fractures of the distal radius is becoming increasingly popular because of the stable biomechanical construct, less soft-tissue disturbance and early mobilisation of the wrist. A few studies have reported complications such as rupture of flexor tendons. We describe three cases of rupture of extensor tendons after the use of volar locking compression plates. We recommend extreme care when drilling and placing the distal radial screws to prevent damaging the extensor tendons.

Volar fixation for dorsally angulated extra-articular fractures of the distal radius: a biomechanical study

PURPOSE

To compare the biomechanical properties of 10 volar plate-fixation designs in 2 fracture models (dorsal wedge osteotomy, segmental resection osteotomy models).

METHODS

Forty-eight radiuses were used in this study including 8 pairs. In 40 specimens a 15-mm dorsally based wedge osteotomy was performed and the volar cortex was fractured manually. They were arranged into 10 fixation groups with 5 different fixation designs (test 1). In the contralateral specimens of 8 paired radiuses a 10-mm segment of bone was excised (test 2). Four of the 10 fixation systems were chosen for these specimens. Cadaver hands and the proximal radiuses were potted in polymethylmethacrylate and tested with a servohydraulic materials testing machine with 300 N of axial compression load at 1 N/s initially and after each 1,000 cycles up to 5,000 cycles. After cyclic loading the specimens were loaded to failure in axial compression at 2 mm/min. The stiffness, failure peak load, and failure mode of each specimen were recorded.

RESULTS

In test 1 in the wedge osteotomy specimens the T plate was the stiffest and the Synthes titanium plate was the least stiff; however, all specimens completed the 5,000 cycles of loading with no failures. There was no significant difference between the 10 fixation groups in failure peak load and only 7 of 40 failed at the distal portion of the hardware in the final load to failure testing. In test 2 the resection osteotomy specimens were less stiff and failed at a lower failure peak load compared with the wedge osteotomy specimens. Failure at the distal portion of the fixation system was seen in 7 of 8 specimens; nonlocking screws loosened and tines compressed the surrounding bone, resulting in tine-hole enlargement.

CONCLUSIONS

All of the plate-fixation systems delivered sufficient stability to permit the simulated postoperative regimen of 1 week of immobilization followed by 5 weeks of early mobilization until expected union at 6 weeks after surgery. Based on these results a preferable volar fixation system would appear to benefit from the following: (1) sufficient plate strength to support the distal fragment from the volar side, (2) a locking system with sufficient strength to remain locked during the healing process, and (3) a distal design that does not affect the bone adversely. The anatomic reduction of the volar cortex in the wedge osteotomy specimens added stability to the construct.

Volar fixed-angle plating of distal radius extension fractures: influence of plate position on secondary loss of reduction--a biomechanic study in a cadaveric model

PURPOSE

Treatment of extension fractures of the distal radius with volar fixed-angle plates has become increasingly popular in the past 2 years. It has been observed clinically that placement of the distal screws as close as possible to the subchondral zone is crucial to maintain radial length after surgery. The purposes of this study were (1) to evaluate radial shortening after plating with regard to plate position and (2) to evaluate whether plate position has an influence on the strength and rigidity of the plate-screw construct.

METHODS

An extra-articular fracture (AO classification, A3) was created in 7 pairs of fresh-frozen human cadaver radiuses. The radiuses then were plated with a volar distal radius locking compression plate. Seven plates were applied subchondrally; 7 plates were applied 4.5 mm to 7.5 mm proximal to the subchondral zone. The specimens were loaded with 800-N loads for 2,000 cycles to evaluate radial shortening in the 2 groups. Each specimen then was loaded to failure.

RESULTS

Radial shortening was significantly greater when the distal screws were placed proximal to the subchondral zone. The amount of shortening after cyclic loading correlated significantly with the distance the distal screws were placed from the subchondral zone. Rigidity of the plate systems was significantly higher in radiuses in which the distal screws were placed close to the subchondral zone.

CONCLUSIONS

To maintain radial length after volar fixed-angle plating, placement of the distal screws as subchondral as possible is essential. The subchondral plate-screw-bone constructs showed significantly greater rigidity, indicating higher resistance to postoperative loads and displacement forces.

A randomized comparison of locking and non-locking palmar plating for unstable Colles' fractures in the elderly

This study compared the effectiveness of locking and non-locking palmar plating for unstable Colles' fractures in the elderly. The patients treated with locking plates included 4 men and 18 women with a mean age of 68 years (Group A) and those treated with non-locking plates included 3 men and 28 women with a mean age of 74 years (Group B). Radiographic parameters, including palmar tilt, radial inclination and radial length were measured before surgery, after surgery and at final followup. There were no significant differences in respect of any of the radiographic parameters between the two groups pre-operatively. After surgery, all of the radiographic parameters were improved in both groups and there were no significant differences between the two groups at final followup.

Biomechanics and biology of plate fixation of distal radius fractures

The fracture management principles of anatomic or near anatomic reduction, fracture stabilization, minimal operative trauma, and early joint motion are paramount in man-aging unstable distal radial fractures. The operative approach and plate selection should correlate with the fracture configuration. Plates have the advantages of providing secure fixation throughout the entire healing process without protruding wires or pins and allowing early and intensive forearm, wrist, and digital exercises. Disadvantages include additional operative trauma, including fragment devascularization; some additional risk of wrist stiffness; occasional tendon rupture; and at times, the need for plate removal. New developments in plate and screw design and operative strategies, fragment specific fixation, and plate strength have improved results with plate fixation. Fixed angle blades and locking screws and pegs enhance overall plate stability, support the articular surface of the distal radius, and are effective in fractures occurring in osteopenic bone.

Volar fixation of dorsally displaced distal radius fractures using the 2.4-mm locking compression plates

PURPOSE

To determine whether volar fixed-angle plate fixation with a new plate system could be used to treat dorsally unstable distal radius fractures. We hypothesized that volar fixed-angle plate fixation with or without radial styloid fixed-angle plate fixation would provide sufficient rigidity to allow early active range of motion without compromising fracture reduction. The initiation of early active motion may improve functional outcomes.

METHODS

A retrospective review was conducted of one institution's initial experience using a new volar fixed-angle plate system to treat dorsally displaced intra-articular and extra-articular distal radius fractures. Thirty-two fractures in 32 patients with dorsally displaced distal radius fractures were treated with a volar fixed-angle plate with or without a radial styloid fixed-angle plate. Fractures were classified using the AO classification. Radiographic parameters on preoperative, postoperative, and final follow-up radiographs were compared. The time to initiation of active range of motion was determined. Final follow-up ranges of motion and complications were reported. Finally, comparisons were made between the 23 fractures treated with a volar plate alone and the 9 fractures treated with a volar plate and a radial styloid plate.

RESULTS

The average follow-up period was 13 months. Two thirds of the fractures were intra-articular. Average loss of reduction from initial postoperative to final follow-up radiographs was 0 degrees of volar tilt, 1 degrees of radial inclination, and 0 mm of radial length. Active wrist and forearm ranges of motion were initiated at an average of 11 days after surgery. The final follow-up flexion-extension and pronation-supination arcs averaged 112 degrees and 151 degrees , respectively. The 9 fractures treated with the combination of a fixed-angle volar plate with a fixed-angle radial styloid plate had greater initial displacement than did the 23 fractures treated with a volar plate alone. Otherwise, differences between the 2 groups were not significant. Only 1 radial styloid plate became symptomatic.

CONCLUSIONS

Volar plate fixation using a new fixed-angle plate system successfully can stabilize dorsally unstable distal radius fractures. Early active range of motion was facilitated without compromising fracture reduction.