Biomechanical Background

The concept of plating for distal radius fractures is based on the three-column model.¹ The model says simply that the distal forearm consists of three columns (Fig. 11-1). The radial column is composed of the radial styloid process and the scaphoid facet; the intermediate column is formed by the lunate facet and the sigmoid notch; and the distal ulna is the ulnar column together with the triangular fibrocartilage and the ulnar part of the lunate facet and sigmoid notch. In extension fractures of the distal radius, the distal epiphyseal fragment is displaced toward the dorsal and radial directions. Separate buttressing of the intermediate and the radial columns by two individual plates to prevent dorsal (intermediate column plate) and radial (radial column plate) dislocation has been shown to be a stable mechanical construct with greater stiffness than a conventional 3.5-mm T-plate or a Pi plate (2.7 mm) in cadaver wrists that show a simulated dorsal metaphyseal defect.²

FIGURE 11-1 The Three-Column Model. Ulnar column with head of the ulna and TFCC; intermediate column with the lunate sulcus and ulnar notch (DRUJ); and radial column with scaphoid sulcus and radial styloid process.

(From Rikli DA, Businger A, Babst R: Dorsal double-plate fixation of the distal radius. Oper Orthop Traumatol 2005; 6:624-640. Used with permission.)

In vivo analysis of force transmission across the radioulnocarpal joint has revealed data that are consistent with the three-column model. Only a small amount of force is transmitted through the radial column. The radial column serves more as a radial osseous buttress and an insertion for the radiocarpal ligaments. In intra-articular fractures, the radial styloid most often is one single bone fragment without comminution or impaction of the joint surface. The greatest force is transmitted across the intermediate and the ulnar columns. In intra-articular fractures, the key articular fragments and impaction zones are found at the level of the intermediate column due to these compressive forces. The intermediate column, therefore, is the key to the radiocarpal joint. The ulnar column also transmits an amount of force that is comparable to that of the intermediate column. It is therefore very sensitive to radial shortening (relative ulnar overlength), which produces painful ulnar impaction. Thus, reconstruction of radial length is an important prognostic outcome factor. Moreover, the ulnar column is the pivot that serves as the center of rotation of the hand and carpus around the forearm, with a complex soft tissue stabilizing construct (TFC, ulnocarpal ligaments, ECU).³

In light of these biomechanical data and on the basis of clinical experience, it makes sense to look at the three columns separately. In distal radius fractures, all three columns should be stable or stabilized.

Three-Step Approach to High-Energy Intra-articular Distal Radial Fractures

High-energy impact to the wrist can lead to disruption of the three columns and to separation of the fragments, fragmentation of the column, impaction of articular fragments, osseous defects, cartilage damage and disruption, and avulsion of stabilizing ligaments. Soft tissue swelling is usually considerable, and bruising or even open wounds may be present. Acute median neuropathy may occur due to dorsal dislocation of the distal fragment or direct pressure of the shaft fragment on the nerve.

Analysis of the individual fracture personality on the basis of the initial emergency room radiograph when the fracture has been unreduced is difficult, and a clear treatment strategy often cannot be developed based on the initial imaging. So for complex, high-energy injuries, it may be advisable to perform a closed reduction and a joint-bridging external fixator as a first measure in the emergency situation (step 1). The advantages are as follows: closed reduction and external fixation are easy to perform, even by inexperienced staff; skin and soft tissue lesions can calm down over the coming days; and median nerve neuropathy usually resolves after preliminary closed reduction. A computed tomography (CT) scan of the wrist in traction allows accurate analysis of the fracture personality and provides more information about a definitive treatment strategy than does a CT scan of an unreduced fracture because some fragments are reduced under ligamentotaxis (step 2). When the swelling has subsided, usually after 3 to 7 days, the definitive osteosynthesis, according to the preoperative planning based on conventional radiographs and CT scans, can be performed (step 3). An external fixator in place is then a helpful intraoperative reduction tool.⁴

Analysis of the Fracture Personality

A thorough analysis of the fracture personality is the prerequisite for developing an adequate treatment strategy. Fernandez⁵ has proposed a pathomechanical classification that allows identification of the principal forces involved in the individual injury: bending, shear, avulsion, and compression. Categorizing the fracture into these groups helps to define the major treatment strategy: bending responds to ligamentotaxis; shear requires buttressing; avulsion needs reinsertion of ligaments; and compression affords individual reconstruction of the columns, often with formal revision of the intermediate column (“the key to the radiocarpal joint”).

In high-energy intra-articular fractures, a preoperative CT scan in traction should be indicated deliberately. If a three-step approach is performed, as delineated earlier, a CT scan with an external fixator in place is the preferred investigation. In our experience and in accordance with Melone,⁶ there are five key elements that should be analyzed in the CT image:

All five of these key elements should be identified and considered when planning treatment.

Dorsal Double Plating

The indications for dorsal double plating are any situations in which a dorsal arthrotomy is warranted in order to revise the radiocarpal joint surface and the proximal carpal row. We do not perform palmar arthrotomies so as to avoid provoking carpal ligament instability. A dorsal arthrotomy may be indicated to reconstruct the articular surface at the level of the intermediate column, especially when impacted articular fragments are present. Such fragments may require direct manipulation. In a dorsal arthrotomy, disruption of interosseous ligaments (especially the scapholunate) can be ruled out or confirmed and be treated immediately at the time of fixation of the distal radius fracture. Furthermore, a dorsal approach is preferred when a displaced dorsoulnar fragment is present. This fragment, which is a key fragment of the radiocarpal articular surface and the sigmoid notch, can then be reduced anatomically and fixed specifically with a separate intermediate column plate. In some cases of corrective osteotomies, a dorsal approach may also be preferred.⁷

A single dorsal approach should not be used if a palmar articular fragment is in hyperextension or if there is considerable comminution at the level of the palmar cortex.