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SCIENTIFIC ARTICLE

Biomechanical Comparison of Dorsal Nail Plate Versus

Screw and K-Wire Construct for Extra-Articular Distal

Radius Fractures in a Cadaver Bone Model

Daniela Klitscher, MD, Isabella Mehling, MD, Lukas Nowak, Tobias Nowak, MD,Pol M. Rommens, MD, PhD, Lars P. Müller, MD, PhD

Purpose The purpose of the study was to compare the biomechanical stability of distalradius fracture fixation with 2 new implants, the DNP (Hand Innovations LLC, Miami,FL), a dorsal locked hybrid of nail and plate, and the XSCREW (Zimmer, Freiburg,Germany), an implant combining a cannulated screw and K-wires, in a cadaver bonedistal radius fracture model.

Methods Eight pairs of fresh-frozen cadaver radii were used. To simulate an extra-articulardistal radius fracture, a 5-mm volar open wedge osteotomy was made. Axial loads of 10 to100 N and torque loads of �1.5 to 1.5 Nm were applied by a testing machine to the intactradii and to the radii after each device was fixed as recommended by the manufacturer. Onethousand cycles in torque and failure tests were performed.

Results With a median of 136.0 N/mm, the axial stiffness of XSCREW-fixed specimens washigher than that of DNP-fixed specimens, with a median of 69.5 N/mm, but differences werenot statistically significant. With a median of 0.163 Nm/°, the torque stiffness of XSCREW-fixed specimens was significantly higher than that of DNP-fixed specimens, with a medianof 0.068 Nm/°. The XSCREW-group reached 33% of the axial stiffness and 49% of thetorque stiffness of the intact radii, and the DNP-group reached 14% of the axial stiffness and20% of the torque stiffness of the intact radii.

Conclusions In this human cadaver bone biomechanical study, the XSCREW provided morestability than the DNP in torque stiffness but not in axial stiffness. (J Hand Surg 2010;35A:611–618. © 2010 Published by Elsevier Inc. on behalf of the American Society for Surgery of theHand.)

Key words Biomechanics, distal radius, fracture, internal fixation, intramedullary.

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RACTURES OF THE distal radius are common, ac-counting for approximately 15% of all extremityfractures.1 Established methods in treating distal

adius fractures are closed reduction and casting,2,3

ercutaneous pinning,2–4 external fixation3,5,6 and openeduction and internal fixation,7–10 each with its own

From the Center for Trauma and Orthopaedic Surgery, University Medical Center, Mainz, Germany.

Received for publication September 27, 2009; accepted in revised form January 22, 2010.

TheauthorswishtoacknowledgeDr.KlausBurkhartforsupportingthepreparationof the manuscript. Theauthors wish to thank Dr. Stefaan Nijs and Mr. Werner Sternstein for their technical assistance.

Daniella Klitscher and Isabella Mehling contributed equally to this work. This work is part of the doc-

toral thesis of Lukas Nowak. d

dvantages and potential complications. The main ob-ectives of treatment are to gain and maintain anatom-cal reduction while the fracture heals, to restore pain-ess wrist motion and strength, and to avoid typicalomplications.2– 4,11,12 Locking plates are strongnough for the fixation of unstable distal radius frac-

o benefits in any form have been received or will be received related directly or indirectly to theubject of this article.

orresponding author: Daniela Klitscher, MD, Center for Trauma and Orthopaedic Surgery, Univer-ity Medical Center, Langenbeckstraße 1, D-55101, Mainz, Germany; e-mail: dklitscher@aol.com.

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612 BIOMECHANICAL COMPARISION OF DNP AND XSCREW

tures and provide favorable clinical results.7–9,13,14

Dorsal plating can cause extensor tendon irritationand rupture because extensor tendons glide directlyover the bone of the distal radius and are exposed toplates applied in this region. Flexor tendons are bet-ter protected by the pronator quadratus muscle andconcave contour of the distal radius, which providesa volar recess for the plate.15 But volar plating canstill cause flexor tendon ruptures, and can also causeextensor tendon ruptures due to dorsal cortex screwpenetration.9,15,16 Intramedullary or partial intramed-ullary implants, such as the Dorsal Nail Plate (DNP,Hand Innovations LLC, Miami, FL),13,17,18 theMicronail (Wright Medical Technology, Arling-ton, TN),18 –22 the TargonDR (Aesculap, Tuttlin-gen, Germany),23 or the XSCREW (Zimmer,Freiburg, Germany), have been developed recentlyfor internal fixation of the distal radius. Theseimplants are thought to allow stable fixation ofsome fracture types while minimizing soft tissuetrauma. Early clinical results are described aspromising but require longer follow-up.18,19,21

Few biomechanical studies have been performed tocompare the ability of these new devices to allowearly loading and motion of the wrist joint.13,22

The purpose of our study was to compare thebiomechanical properties of 2 of these implants,the DNP and the XSCREW, in fixation of a ca-

FIGURE 1: Radiographs after implant fixation before biomechB Lateral view after fixation with a DNP. C Posteroanterior vwith an XSCREW.

daver bone model of a distal radius fracture.

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MATERIALS AND METHODS

Specimen preparation

Eight pairs of fresh-frozen cadaver radii were selected,and the soft tissue was stripped from the bone. Themean age of the cadavers was 81 years (range 74–88years). Of the 8 pairs, 3 were male and 5 were female.All specimens were radiographed before testing to ex-clude any pathology. The radii were stored at �25°Cuntil testing. Radii were cut at 13 cm proximal to thearticular surface. The radius shaft and the distal endwere embedded in methyl methacrylate. Each radialspecimen was placed in a servo-pneumatic materialstesting machine (Sinco Tec, Clausthal-Zellerfeld, Ger-many) and was first tested intact. After that, the distalmethyl methacrylate block was removed until test-ing with the implant. A volar open wedge osteot-omy with a 5-mm volar gap and a 2-mm dorsal gapwas made, using an oscillating saw with a kerf sizeof 2 mm, to simulate an extra-articular metaphy-seal fracture, an AO type A3 fracture. The dorsalosteotomy was centered 20 mm proximal to themiddle of the dorsal articular surface. Before im-plant placement, the integrity of the volar cortexwas maintained. Pairs were randomized so thateach implant was applied 4 times in a right and 4times in a left radius. Each implant was applied asrecommended by the manufacturer.24,25 The volar cortex

l testing. A Posteroanterior view after fixation with a DNP.fter fixation with an XSCREW. D Lateral view after fixation

anicaiew a

was resected to complete the metaphyseal gap after im-

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BIOMECHANICAL COMPARISION OF DNP AND XSCREW 613

plant insertion. Radiographs were taken to check correctimplantation before biomechanical testing (Fig. 1).

Implant design and technique

DNP: The DNP (Hand Innovations LLC) is a fixed-angle implant that is applied on the dorsal aspect of theradius.24 The head of the implant, the plate section with3 divergent locking pegs, fits on the floor of the thirdcompartment, requiring mobilization of the long thumbextensor tendon and removal of Lister’s tubercle. Theproximal part, the nail section, is placed into the med-ullary canal. The DNP is thought to avoid impairmentof soft tissue, particularly of the extensor tendons, ow-ing to its low profile and the necessity of only a smallincision. The implant is intended for use in metaphysealand simple intra-articular fractures in which reductioncan be achieved by closed means.

The silhouette of the head of the implant is drawnwith a marking pen so that the distal edge of the implantwill rest 4 mm proximal to the articular surface. Lister’stubercle is removed with a rongeur. The medullarycanal is opened with an awl, and the DNP isinserted with the insertion jig and advanced intothe medullary canal. First, the most distal subchon-dral locking peg is inserted. Protrusion of the pegthrough the volar cortex is avoided. Next, theproximal 3 unicortical screws are placed in a dor-sal-to-volar direction through the aiming jig. Fi-nally, the remaining 2 distal pegs are positioned.

XSCREW: The XSCREW (Zimmer) is an implantthat combines a cannulated screw and K-wires.25 Toachieve a locked system, K-wires are inserted throughholes in the screw. The 2 distal holes for the K-wires aredrilled at an angle of 45° in relation to the screw axis,and the maintaining holes are perpendicular to thescrew axis. Implantation occurs through a radial styloidapproach between the first and second extensor com-partment. The XSCREW is indicated for extra-articularmetaphyseal fractures, Chauffeurs fractures and simpleintra-articular fractures.

A semiradiolucent alignment device is used to definethe position of the screw. A guide wire is inserted underimage intensifier control. After the length is measuredand drilling is completed, the screw is placed over theguide wire. Among the available lengths (38, 43, 48, 53,and 58 mm), a screw with appropriate length is se-lected, allowing penetration of the ulnar cortex of theradial shaft. The targeting device is placed. Theprotection sleeve is introduced into the guide holesof the targeting device, and 1.6 mm K-wires withthreaded tips are inserted into the protection sleeve

and drilled through both cortices. The K-wires

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are cut at 1–3 mm, and the targeting device isremoved.

After implant insertion, the distal methyl methacry-late block was fixed with a screw. Contact of the im-plants with the methyl methacrylate block was avoided.

Biomechanical testing

First, 6 cycles of axial loads of 10 to 100 N and torqueloads of �1.5 to 1.5 Nm with sinusoidal load alterationswere applied to the intact radius. After implantation ofa DNP or an XSCREW, these 6 cycles were appliedagain in the same manner. Next, 1000 cycles of dy-namic torque load alterations of 0.5 to 1.5 Nm (or �0.5to �1.5 Nm convenient to side) at 0.5 Hz with a preloadof 10 N were performed. In the specimens that were stillintact after 1000 cycles, loading in torque was contin-ued until failure occurred. Axial and torque stiffnessvalues of the osteosynthesis system were calculated,using computer software (Prism, version 5.02, GraphPad Software Inc., San Diego, CA). Figure 2 shows anXSCREW-fixed specimen placed in the testing ma-

FIGURE 2: The experimental set-up with an XSCREW-fixedspecimen. After proximal and distal ends were embedded inmethyl methacrylate, the radii were placed in a servo-pneumatic testing machine (Sinco Tec, Clausthal-Zellerfeld,Germany). Axial and torque loads were applied.

chine.

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614 BIOMECHANICAL COMPARISION OF DNP AND XSCREW

Statistical methods

We used the Wilcoxon matched pairs test to evaluatedifferences between implant pairs in axial and torquestiffness and to evaluate differences between intact radiibefore implant insertion and radii after implantation ofan XSCREW or a DNP. A p value �.05 was consid-ered significant. The results of stiffness values are pre-sented in the form of box plots.

RESULTS

Axial stiffness

Table 1 shows medians, 25th percentiles, 75th percen-tiles, means, and standard deviations of the axial stiff-ness values of the intact radii and the implant-fixedspecimens. Under 6 cycles of axial loads of 10 to 100 Nand torque loads of �1.5 to 1.5 Nm, the calculatedmedian of axial stiffness of the intact radii before im-plantation of an XSCREW was 517.0 N/mm, of theintact radii before implantation of a DNP was 445.5N/mm, of the radii after implantation of an XSCREWwas 136.0 N/mm, and of the radii after implantation ofa DNP was 69.5 N/mm. Figure 3 shows the box plots ofaxial stiffness values of the intact radii and the implant-fixed specimens. The axial stiffness values of intactradii before implant insertion were significantly higherthan stiffness values after implantation of XSCREW orDNP (p � .008). With a median of 136.0 N/mm, theaxial stiffness of XSCREW-fixed specimens was higherthan that of DNP-fixed specimens, with a median of69.5 N/mm, although this difference between the pairsdid not show statistical significance. On average, theXSCREW-group reached 33% and the DNP-groupreached 14% of the axial stiffness of the intact radii.

Torque stiffness

Table 2 shows medians, 25th percentiles, 75th percen-tiles, means, and standard deviations of torque stiffnessvalues of the intact radii and the implant-fixed speci-mens. Under 6 cycles of axial loads of 10 to 100 N andtorque loads of �1.5 to 1.5 Nm, we observed calculated

TABLE 1. Medians, 25th Percentiles, 75th PercentilIntact Radii and the Implant-Fixed Specimens

Axial Stiffness (N/mm) Median 25

Intact specimens XSCREW group 517.0

Intact specimens DNP group 445.5

XSCREW-fixed specimens 136.0

DNP-fixed specimens 69.5

medians of torque stiffness of 0.319 Nm/° in intact radii

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before implantation of an XSCREW, of 0.372 Nm/° inintact radii before implantation of a DNP, of 0.163Nm/° in specimens after implantation of an XSCREW,and of 0.068 Nm/° in specimens after implantation of aDNP. Figure 4 shows the box plots of torque stiffnessvalues of the specimens before and after implantation ofan XSCREW or a DNP. Torque stiffness values ofintact radii were significantly higher than stiffness val-ues after implantation of an XSCREW or a DNP (p �.008, p � .031). Torque stiffness of XSCREW-fixedspecimens, with a median of 0.163 Nm/°, was signifi-cantly higher than that of DNP-fixed specimens, with a

FIGURE 3: Box plots of axial stiffness values of the intactradii before implantation of XSCREW® or DNP®, of theXSCREW-fixed specimens and of the DNP-fixed specimens.

eans, and SDs of Axial Stiffness Values of the

rcentile 75th Percentile Mean SD

4.0 656.0 498.5 154.0

7.6 613.0 469.0 138.4

4.4 222.7 151.8 111.9

1.5 88.7 63.5 30.3

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33

34

6

4

median of 0.068 Nm/° (p � .03). On average, the

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BIOMECHANICAL COMPARISION OF DNP AND XSCREW 615

XSCREW group reached 49% and the DNP groupreached 20% of the torque stiffness of the intact radii.

Cyclic loading and failure tests

During 1000 cycles of dynamic torque load alterationsof 0.5 to 1.5 Nm (or �0.5 to �1.5 Nm) at 0.5 Hz witha preload of 10 N, only 4 specimens in the XSCREWgroup and one specimen in the DNP group did not fail.In these specimens, cyclic loading was continued untilfailure occurred. In the DNP group, 5 cases of failureoccurred by longitudinal fracture in the sagittal planealong the monocortical screws of the proximal fragment

TABLE 2. Medians, 25th Percentiles, 75th PercentilIntact Radii and the Implant-Fixed Specimens

Torque Stiffness (Nm/°) Median 25

Intact specimens XSCREW group 0.319

Intact specimens DNP group 0.372

XSCREW-fixed specimens 0.163

DNP-fixed specimens 0.068

FIGURE 4: Box plots of torsional stiffness values of the intactradii before implantation of XSCREW or DNP, of theXSCREW-fixed specimens and of the DNP-fixed specimens.

(Fig. 5). In 3 of these cases, the osteotomy gap was

JHS �Vol A, A

partially or completely closed. In 2 cases, the osteotomygap was not closed. In some cases, these longitudinalfractures were hardly visible or not visible in the radio-graphs. In one case, the DNP broke out from the prox-imal fragment and the osteotomy gap was closed. In 2cases of the DNP group, failure occurred due to irre-versible deformation of the implant–bone construct inthe distal fragment, with partial or complete closure ofthe osteotomy gap. In the XSCREW group, we ob-served 3 cases of the screw breaking out of the distal

eans, and SDs of Torque Stiffness Values of the

ercentile 75th Percentile Mean SDs

272 0.421 0.340 0.092

265 0.412 0.339 0.103

117 0.185 0.160 0.040

054 0.100 0.078 0.032

FIGURE 5: Front view of a DNP-fixed specimen after failureoccurred by a longitudinal fracture in the sagittal plane alongthe monocortical screws of the proximal fragment (whitearrow).

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fragment with closure of the osteotomy gap and 3 cases

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616 BIOMECHANICAL COMPARISION OF DNP AND XSCREW

of longitudinal fractures in the frontal plane of theproximal fragment. In 2 of these cases, the osteotomygap was not closed, and in one case, the osteotomy gapwas partially closed. In one case, failure occurred as aresult of irreversible deformation of the implant–boneconstruct in the distal fragment and in another case byan oblique fracture of the proximal fragment with par-tial closure of the osteotomy gap.

DISCUSSIONThe outcome of distal radius fractures correlates withthe stable restoration of the anatomy.2,3,26 Lockingplates have been shown to be strong enough to maintainreduction of unstable distal radius fractures while theyheal and provide favorable clinical results.7–9,13,14 Awell-known complication of dorsally applied plates istendon rupture, and volar plating can also cause tendonirritation and rupture.9,15,16 Both volar and dorsal ap-proaches might disturb fracture fragment vascularity.18

To minimize soft tissue impairment, intramedullary orpartial intramedullary implants such as the DNP, theXSCREW, and the Micronail have been developed forunstable metaphyseal and simple intra-articular distalradius fractures. To date, only a few clinical and bio-mechanical results have been presented in the literaturewith respect to these new implants.13,17,22,24

Biomechanical comparisons of an intramedullaryimplant for distal radius fractures to other devices wereperformed by McCall et al.13 and Capo et al.22 In thestudy of McCall et al., in a distal radius fracture modelof a dorsally unstable extra-articular fracture, the DNP,the DVR (Distal Volar Radius plate; Hand InnovationsLLC) and the LCP (Locking Compression Plate; Syn-thes, Paoli, PA) were tested on artificial compositeradii.13 Only axial loading was performed. The DVRhad the greatest axial stiffness, with a mean of 619N/mm, followed by the DNP with 494 N/mm and theLCP with 283 N/mm. The axial stiffness values of theDVR were significantly higher than those of the LCP(p � .001). The axial stiffness values of the DNP werehigher than those of the LCP, but they did not reachstatistical significance. We observed a median of axialstiffness of 69.5 N/mm in DNP-fixed specimens. Thespecimens used by McCall et al. were artificial com-posite radii (Sawbones; Pacific Research Laboratories,Vashon, WA), replicating approximately, in some den-sities, the material properties of bone. Our results mightdiffer because we examined fresh cadaver radii with amean age of 81 years. Capo et al. examined 4 fixationconstructs: the Micronail, an intramedullary implant;the DVR, a volar locked plate; the Locon-T plate

(Wright Medical Technology, Arlington, TN), a dorsal

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nonlocking plate; and a construct with 2 dual-columnplates, using 2.4-mm titanium locked plates.22 An ex-tra-articular wedge osteotomy was performed in 28fresh-frozen cadaver radii, and dorsal bending loadswere applied. The DVR plate had the highest values inbending stiffness and load to failure, followed by theMicronail, the dual-column plates, and the Locon-Tplate. The DVR-plate was significantly more rigid thanthe Locon-T plate (p � .003) and significantly strongerthan the Locon-T plate (p � .001) and the dual-columnplates (p � .05). No statistically significant differenceswere found between the DVR-plate and the Micronail.The authors concluded that comparable stability can beachieved with the volar locked DVR-plate and the Mi-cronail. In a previous study, we compared the axialstiffness of 5 different plates in a distal radius osteot-omy cadaver model.27 In that study, the median of axialstiffness was 331.1 N/mm for the Martin radius correc-tion plate (Martin, Tuttlingen, Germany); 307.6 N/mmfor the Martin radius correction plate with lateraltongue; 128.1 N/mm for the DVR; 111.5 N/mm for theLCP; and 93.1 for the Synthes standard, stainless steel,3.5-mm T-plate (Synthes, Solothurn, Switzerland), anon-locked plate. In the present study, with a median of136.0 N/mm, axial stiffness of XSCREW-fixed speci-mens was higher than that of DNP-fixed specimens,with a median of 69.5 N/mm, but it did not reachstatistical significance (p � .054). This study includedtorque loading; with a median of 0.163 Nm/°, torquestiffness of XSCREW-fixed specimens was signifi-cantly higher than that of DNP-fixed specimens. with amedian of 0.068 Nm/° (p � .03). Estimated from the-oretical calculations, a 100-N load compares to thephysiological loads expected during active wrist jointmotion and to the loads across the wrist joint duringactivities of daily living.28–30 During 1000 cycles ofdynamic torque load alterations of 0.5 to 1.5 Nm (or�0.5 to �1.5 Nm) at 0.5 Hz with a preload of 10 N,only 4 specimens in the XSCREW-group and one spec-imen in the DNP group did not fail. Our results suggestthat postoperative physiotherapy after fixation with anXSCREW or a DNP in elderly people should be donecarefully or delayed until first callus formation is visiblein control radiographs.

In the DNP group, the common mode of failure wasa longitudinal fracture in the sagittal plane along themonocortical screws of the proximal fragment (Fig. 5).Bicortical screws might prevent these fractures. Weobserved some cases in which the longitudinal fracturewas hardly visible or not visible in the radiographs andthe osteotomy gap was not closed. Therefore, it is

possible that, in clinical circumstances, a DNP-fixed

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BIOMECHANICAL COMPARISION OF DNP AND XSCREW 617

distal radius fracture heals uneventfully despite such alongitudinal fracture or, if mechanical complicationsare not detected early, continuous exercises can lead todisplaced fracture patterns.

For internal fixation the stiffest implant is not nec-essarily optimal. Both stability and micromotion at thefracture site are important for fracture healing. There isno exact definition of the amount of interfragmentarymovement required to stimulate callus formation, or theamount that will inhibit bone healing.31 Therefore, bio-mechanical in vitro studies cannot replace clinical stud-ies.

To date, few clinical studies of these new implantshave been performed.17,19,21,24 In more than 200 caseswith extra-articular or nondisplaced intra-articular distalradius fractures treated with DNP, Orbay et al.24 ob-served only 4 complications. In this preliminary report,describing only early experiences, the authors concludethat the functional results were satisfying. Most patientswere able to perform activities of daily living after thefirst or second postoperative week.24 Espen et al. de-scribed one rupture of the long thumb extensor tendonand one loosening of the locking screws, but no sec-ondary fracture displacement, in 32 cases treated withDNP.17

To date, there are no clinical or biomechanicalstudies concerning the XSCREW in the literature.We found preliminary results of another new in-tramedullary implant, the Micronail (Wright Med-ical Technology).19,21 The Micronail is implantedthrough the tip of the radial styloid, using a similarapproach to that for the XSCREW. But in contrastto the XSCREW, the Micronail sits completelywithin the medullary canal.19,20 Tan et al. reportedearly results of Micronail-fixation in 15 cases ofdistal radius fractures.21 They observed a transientradial sensory nerve disturbance in 3 patients. Ilyaset al. observed 10 patients with AO type A andtype C distal radius fractures after fixation with aMicronail.19 According to the DASH question-naire, there were 8 excellent, 1 good, and 1 poorresult. They found 2 cases of temporary radialsensory nerve disturbance, 3 cases of screw pene-tration, and 2 cases of loss of reduction. Althoughthe DNP is mainly located within the medullarycanal, there is still a risk of injury of the extensortendons, especially of the long thumb extensortendon.17 Potential complications of using im-plants involving a radial approach, such as with theXSCREW or the Micronail, are lesions of theradial sensory nerve and the first extensor com-

partment.20,21

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More clinical studies with a longer follow-up arerequired in order to determine the frequency ofcomplications after fracture fixation with thesenew devices in comparison to treatments with es-tablished implants. Further biomechanical studiesin different fracture types are necessary to deter-mine whether the new devices are useful alterna-tives for fixation of distal radius fractures.

REFERENCES1. Nana AD, Joshi A, Lichtman DM. Plating of the distal radius. J Am

Acad Orthop Surg 2005;13:159–171.2. Siebert HR, Klonz A. Distale Radiusfraktur. Unfallchirurg 2005;

108:135–153.3. Nijs S, Broos PLO. Fractures of the distal radius: a contemporary

approach. Acta Chir Belg 2004;104:401–412.4. Weber SC, Szabo RM. Severely comminuted distal radial fracture as

an unsolved problem: complications associated with external fixationand pins and plaster techniques. J Hand Surg 1986;11A:157–165.

5. Suso S, Cambalia A, Segur JM, Garcia-Ramiro S, Ramon R. Com-minuted intra-articular fractures of the distal end of the radius treatedwith the Hoffmann external fixator. J Trauma 1993;35:61–66.

6. Agee JM, Szabo RM, Chidgey LK, King FC, Kerfoot C. Treatmentof comminuted distal radius fractures: an approach based on patho-mechanics. Orthopedics 1994;17:1115–1122.

7. Orbay JL, Fernandez DL. Volar fixed-angle plate fixation for unsta-ble distal radius fractures in the elderly patient. J Hand Surg 2004;29A:96–102.

8. Orbay JL, Fernandez DL. Volar fixation for dorsally displacedfractures of the distal radius: a preliminary report. J Hand Surg2002;27A:205–215.

9. Arora R, Lutz M, Hennerbichler A, Krappinger D, Espen D, Gabl M.Complications following internal fixation of unstable distal radius frac-ture with a palmar locking-plate. J Orthop Trauma 2007;21:316–322.

10. Basten K, Hansen M, Rommens PM. Die operative Behandlung derdistalen Radiusfraktur durch T-Plattenosteosynthese [Operativetreatment of distal radius fractures by T-plate-osteosynthesis]. AktTraumatol 1999;29:137–143.

11. Murakami K, Abe Y, Takahashi K. Surgical treatment of unstabledistal radius fractures with volar locking plates. J Orthop Sci 2007;12:134–140.

12. Wolf JC, Weil WM, Hanel DP, Trumble TE. A biomechanic com-parison of an internal radiocarpal-spanning 2.4-mm locking plate andexternal fixation in a model of distal radius fractures. J Hand Surg2006;31A:1578–1586.

13. McCall T, Conrad B, Badman B, Wright T. Volar versus dorsalfixed-angle fixation of dorsally unstable extra-articular distal radiusfractures. A biomechanical study. J Hand Surg 2007;32A:806–812.

14. Leung F, Zhu L, Ho H, Lu WW, Chow SP. Palmar plate fixation ofAO type C2 fracture of distal radius using a locking compressionplate—a biomechanical study in a cadaveric model. J Hand Surg2003;28A:263–266.

15. Buzzell JE, Weikert DR, Watson JT, Lee DH. Precontoured fixed-angle volar distal radius plates: a comparison of anatomic fit. J HandSurg 2008;33A:1144–1152.

16. Maschke SD, Evans PJ, Schub D, Drake R, Lawton JN. Radio-graphic evaluation of dorsal screw penetration after volar fixed-angleplating of the distal radius: a cadaveric study. Hand 2007;2:144–150.

17. Espen D, Lauri G, Fernandez D. Stabilisation of distal radius frac-tures by a novel endomedullary, fixed-angle plate: first experience[in German]. Handchir Mikrochir Plast Chir 2007;39:73–77.

18. Brooks KR, Capo JT, Warburton M, Tan V. Internal fixation of distalradius fractures with novel intramedullary implants. Clin Orthop

Relat Res 2006;445:42–50.

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19. Ilyas AM, Thoder JJ. Intramedullary fixation of displaced distal radiusfractures: a preliminary report. J Hand Surg 2008;33A:1706–1715.

20. Ilyas AM, Reish MW, Beg TM, Thoder JJ. Treatment of distal radiusmalunions with an intramedullary nail. Tech Hand Surg 2009;13:30–33.

21. Tan V, Capo J, Warburton M. Distal radius fracture fixation with anintramedullary nail. Tech Hand Surg 2005;9:195–201.

22. Capo JT, Kinchelow T, Brooks K, Tan V, Manigrasso M, FranciscoK. Biomechanical stability of four fixation constructs for distalradius fractures. Hand 2009;4:272–278.

23. Gradl G, Wendt M, Gierer P, Beck M, Mittlmeier T. IntramedulläreVersorgung der distalen Radiusfraktur. Trauma Berufskrankh 2008;10(Suppl. 2):241–244.

24. Orbay JL, Touhami A, Orbay C. Fixed angle fixation of distal radiusfractures through a minimally invasive approach. Tech Hand Surg2005;9:142–148.

25. XSCREW Locking System. Product Information and Surgical Tech-nique. Zimmer, Freiburg, Germany, 2008.

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26. Knirk JL, Jupiter JB. Intra-articular fractures of the distal end of theradius in young adults. J Bone Joint Surg 1986;68A:647–659.

27. Müller LP, Klitscher D, Mehler D, Rommens PM, Prommers-berger KJ. Locking plates for corrective osteotomy of maluniteddorsally tilted distal radial fractures. J Hand Surg 2006;31B:556 –561.

28. An KN, Chao EY, Cooney WP, Linscheid RL. Forces in the normaland abnormal hand. Orthop Res 1985;3:202–211.

29. Chao EY, Opgrande JD, Axmear FE. Three-dimensional force anal-ysis of finger joints in selected isometric hand functions. J Biomech1976;9:387–396.

30. Putnam MD, Meyer NJ, Nelson EW, Gesensway D, Lewis JL. Distalradial metaphyseal forces in an extrinsic grip model: implications forpostfracture rehabilitation. J Hand Surg 2000;25A:469–475.

31. Perren SM, Claes L. Biologie und Biomechanik im Frakturmanage-ment. In: Rüedi TP, Murphy WM, eds. AO Prinzipien des Fraktur-

managements [AO Principles of Fracture Management]. 5th ed.Stuttgart, New York: Thieme, 2003:7–31.

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