Volar fixed-angle plating of distal radius fractures: screws versus pegs--a biomechanical study in a cadaveric model

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

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

Three-dimensional imaging of the distal radius with reference to volar locking plate surgery

BACKGROUND

The watershed line is widely accepted as the distal limit of the volar locking plate (VLP); however, the VLP placement could vary depending on the plate contour and morphology of the distal radius. The aim of this study was to investigate the morphology of the distal radius and VLP fitting using 3D images.

HYPOTHESIS

We hypothesized that attachment of the VLP would affect the contour of the volar prominence of the distal radius.

PATIENTS AND METHODS

Variable-angle LCP two-column volar distal radius Plate 2.4 and 16 formalin-fixed cadavers were studied. The plate and forearm were scanned using a computed tomography scanner. The plate was fixed to the radial shaft in the most distal position without flexor pollicis longus tendon contact. Postero-antero and lateral radiographs were obtained using fluoroscopy. Postero-antero radiographs were superimposed on a 3D image of the distal radius. The virtual plate was attached to the distal radius in the computer simulations and the plate was adjusted in the sagittal plane. In the postero-antero radiographs, the distance between the plate and distal end of the radius (DPR) was measured. In the sagittal plane, the height of the volar lunate facet (VLF) and the plate-to-bone distance of each locking screw hole was measured. The volar cortical angle (VCA) was measured as the angle formed by a line drawn along the volar surface and a line drawn on the radial shaft on the sagittal plane at each locking screw plane.

RESULTS

A significant correlation was observed between the height of the VLF and the DPR and between the height of the VLF and the VCA. The plate-to-bone distance at the ulnar screw hole was significantly smaller than that of the other screw holes.

DISCUSSION

Our study revealed that the higher the VLF, the more proximal is the VLP. The plate fits on the bone surface at the ulnar side, whereas the radial side has more space between the plate and bone.

LEVEL OF EVIDENCE

III, diagnostic Level.

Ulnar facet locking screw locations of volar locking plates placed without flexor pollicis longus tendon contact: A cadaver study

BACKGROUND

The volar locking plate (VLP) system provides stable fixation and is widely used for distal radius fractures. Studies have shown that irritation of the implant prominence is a risk factor for flexor tendon rupture, especially of the flexor pollicis longus (FPL). Contact between VLPs and flexor tendons should be avoided. We aimed to investigate the ulnar facet locking screw locations of various VLPs placed without FPL tendon contact in cadaver wrists.

HYPOTHESIS

We hypothesized that ulnar facet locking screws would be in the vicinity of the subchondral bone when the plate is placed in the most distal position without FPL tendon contact.

MATERIALS AND METHODS

The study assessed two variable-angles and four fixed locking plates. We placed each plate in six different cadavers, resulting in 36 different plate-cadaver combinations. Plates were placed in the most distal position without FPL tendon contact. We drilled the most ulnar hole (hole A) and the second ulnar hole (hole B) of the distal row. All drilling procedures were performed using a specific jig for each fixed locking plate. For variable-angle locking plates, we drilled with a fixed jig for each plate. We obtained lateral radiographs when the drill penetrated the dorsal cortex and measured the distance between the drill and the articular surface.

RESULTS

With regard to hole A, the mean distances between the drill and the center of the articular surface were 2.6-5.2mm for the four fixed locking plates and 4.9-5.6mm for the two variable-angle locking plates. With regard to hole B, the mean distances between the drill and the center of the articular surface were 3.8-5.9mm for the four fixed locking plates and 5.5-5.9mm for the two variable-angle locking plates.

DISCUSSION

When clinicians place a VLP without FPL tendon contact, the distance between the ulnar facet screws and the center of the articular surface is over 3mm in most cases. Surgeons should select variable-angle drilling for strong articular support when using variable-angle locking plates.

LEVEL OF EVIDENCE

III, diagnostic Level.

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

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

Effect of screw thread length on stiffness of proximal humerus locking plate constructs: A finite element study

Plate-based treatment of proximal humerus fractures is associated with a high risk of complications such as screw perforation into glenohumeral joint. Smooth and threaded pegs were developed with the hope of minimising these risks. No consensus exists onto which threading profile achieves stiffest bone-plate construct. This study investigated the biomechanical effect of five percentages of threading on individual humeral head screws on a bone-plate construct. A finite element model simulating a two-part proximal humerus fracture treated with a Spatial Subchondral Support plate was developed and validated against in vitro biomechanical tests. The proportion of the humeral head screw length that was threaded was varied between 0%-100% in 25% increments. A 5-mm cantilever varus displacement was applied and the required load (F₅) was calculated. Full (100%) threading achieved the stiffest construct for all six screws. Fully threading all smooth pegs at once increased F₅ by 18%. Threading did not increase F₅ equally in all screws. Inferior three plate screws exhibited a larger increase in stiffness than superior three. Most of the mechanical benefits of threading in inferior three screws can be achieved by using threaded pegs (50% threading) while the superior three screws need to be fully threaded. In practice, the smooth surface profile may also offer additional mechanical benefits if implanted with longer lengths and larger diameters. Threading is an effective way of increasing the varus bending stiffness of proximal humerus plates constructs.

Damage in a Distal Radius Fracture Model Treated With Locked Volar Plating After Simulated Postoperative Loading

PURPOSE

"Damage" is an engineering term defining a period between a state of material perfection and the onset of crack initiation. Clinically, it is a loss of fixation due to microstructural breakdown, indirectly measured as a reduction of stiffness of the bone-implant construct, normalized by the cross-sectional area and length of the bone. The purpose of this study was to characterize damage in a cadaver model of extra-articular distal radius fracture with dorsal comminution treated using 2-column volar distal radius plates.

METHODS

Ten matched distal radii were randomly divided into 2 groups: group I specimens were treated with a volar distal radius plate with an independent, 2-tiered scaffold design; group II specimens (contralateral limbs) were treated with a volar plate with a single-head design for enhanced ulnar buttressing. Specimens were cyclically loaded to simulate a 6-month postoperative load-bearing period. We report damage after a defined protocol of cyclical loading and load to failure simulating a fall on an outstretched hand.

RESULTS

Group II specimens experienced more damage under cyclic loading conditions than group I specimens. Group I specimens were stiffer than group II specimens under load-to-failure conditions. Ultimate force at failure in group I and group II specimens was not different. Specimens failed by plate bending (group I, n = 6/10; group II, n = 2/10) and fracture of the lunate facet (group I, n = 4/10; group II, n = 8/10).

CONCLUSIONS

Group I specimens had less screw cutout at the lunate facet than group II specimens under cyclic loading as indicated by lower damage measures and fewer facet fractures during load-to-failure testing. The overall strength of the construct is not affected by plate design.

CLINICAL RELEVANCE

Microstructural damage or a loss of fixation due to an overly rigid volar plate design may cause malunion or nonunion of fracture fragments and lead to bone-implant instability.

The Detection of Prominent Hardware in Volar Locked Plating of Distal Radius Fractures: Intraoperative Fluoroscopy Versus Computed Tomography

OBJECTIVES

To assess the utility of the dorsal tangential view (DTV) in detecting intraoperative dorsal screw penetration in distal radius fractures treated with volar locked plating.

DESIGN

Retrospective cohort study.

SETTING

Academic level 1 trauma center.

PATIENTS/PARTICIPANTS

Skeletally mature patients where open reduction internal fixation with volar locked plating was the definitive treatment. A total of twenty-six patients were evaluated.

INTERVENTION

Intraoperative anteroposterior, lateral, 20 degree tilted lateral, and DTVs were obtained through fluoroscopy in all wrists. Screw exchange and position by fluoroscopic view was recorded. A computed tomography (CT) was taken postoperatively to identify residual prominent screws.

MAIN OUTCOME MEASURES

Data points included frequency of screw exchange by standard fluoroscopic views, the DTV, and residual prominent screws detected by CT.

RESULTS

Eight constructs of thirty (27%) had prominent screws evident on the DTV but not seen on standard fluoroscopic analysis. CT identified 5 additional screws with ≥1 mm dorsal penetration not identified by the DTV. All except 1 screw was in the second dorsal wrist compartment. The DTV was 67% sensitive with a negative predictive value of 97%.

CONCLUSION

It is risky and unnecessary to place bicortical screws in the distal part of a volar plate. Given that the DTV view was not sufficient to avoid dorsal screw prominence, distal screws should be intentionally 2-4 mm shorter than measured. Recent studies propose bicortical distal locking screws are not needed for sufficient construct stiffness in volar locked plating. We suggest caution when using this view to verify acceptable placement of screws in proximity to the second dorsal compartment.

LEVEL OF EVIDENCE

Diagnostic level III. See Instructions for Authors for a complete description of levels of evidence.

Pearls and Pitfalls of the Volar Locking Plating for Distal Radius Fractures

Volar locking plate fixation has been widely accepted method for the treatment of unstable distal radius fractures. Although the results of volar locking plate fixation are encouraging, it may cause implant-related complications such as flexor or extensor tendon injuries. In depth understanding of anatomy of the distal radius is mandatory in order to obtain adequate fixation of the fracture fragments and to avoid these complications. This article will review the anatomic characteristics of the distal radius because selecting proper implant and positioning of the plate is closely related to the volar surface anatomy of the distal radius. The number and the length of distal locking screws are also important to provide adequate fixation strength to maintain fracture fixation. We will discuss the pros and cons of the variable-angle locking plate, which was introduced in an effort to provide surgeons with more freedom for fixation. Finally, we will discuss about correcting radial length and volar tilt by using eccentric drill holes and distal locking first technique.

Comparative clinical study of locking screws versus smooth locking pegs in volar plating of distal radius fractures

The present study was performed to test the null hypothesis on no difference in stability of fixation after volar plating of intra-articular distal radius fractures (AO C2-C3) with either locking smooth pegs or locking screws in a clinical setting. A retrospective evaluation included adult patients with C2-C3 AO fractures treated with a volar plate with locking smooth pegs or locking screws. Radiographic assessment was performed to evaluate extra- and intra-articular parameters in the early postoperative period and after bone union. Twenty-seven consecutive patients were included. Thirteen cases had fixation with locking screws and 14 had fixation with locking smooth pegs. Both groups had bone fragment displacement after fixation. However, there were no significant differences between the groups either in extra- or intra-articular parameters defined by Kreder et al. (1996). Our study shows that, in a clinical setting, there is no difference in stability fixation between locking screws or smooth locking pegs in C2-C3 distal radius fractures.