23.1 Introduction

The integrity of geometrical shape of the distal radius, due to its two articular surfaces and adjacent joints, has a significant impact on the function of the wrist. Thus, when treating fractures or deformities of the distal radius the prime goal is to restore the original anatomy. However, the radius displays quite a complex three-dimensional (3D) structure, challenging the assessment, the understanding, and the feasibility of repair of the altered structures.

For almost a century, conventional X-rays represented the only method of imaging, evidently a technology that, due to projectional effects, distorts angles and, due to the divergence of the X-ray beams, alters length relationships. This drawback drove several surgeons to use complex mathematical models to compensate for this defect. ^{1 , 2 , 3} But even the most sophisticated calculations were unable to catch up for the limitations of a two-dimensional imaging technique. ^{2 , 3 , 4 , 5 , 6} Therefore, conventional radiographs are unable and insufficient to accurately depict a 3D object. ^{7 , 8}

With the advent of computed tomography (CT) the radiologists received a powerful tool capable to surmount these problems. However, tied to the traditional way of looking at radiographs, the output of the CT scanners remained hooked to single planes renouncing to extract the totality of the information gathered. It took more than three decades until the manufacturers and radiologists offered rather simplistic measuring and 3D representation options. Still not true 3D images, deprived of the possibility to interact and no attempt to manipulate. Thus, surgeons treating fractures or bone deformities continued to plan their interventions relying mainly on two perpendicular images and only exceptionally took in account rotatory deformities available from clumsy comparison of axial sections. ⁹

Although reconstruction of 3D models, 3D analysis, and virtual planning is available since the 1990s, it remained without practical use and spread in orthopaedic surgery. This omission was and still is justified by cost and difficulty. The latter has meanwhile well been resolved—on one hand by the availability of specific software and on the other by the massive intrusion of computer technologies in our daily lives and its inevitable acceptance. The cost indisputably higher than the rule-of-thumb techniques are well in line with other technological advanced treatments, increasingly accepted by providers and patients striving for the best possible result.

Meanwhile thanks to other technical progress, the possibilities have evolved much further; 3D printing allows for manufacturing patient-specific guides and aids in order to transform the virtual plan in the surgical setting.

23.2 Indications

The technique can be used for any fracture or deformity in which a precise preoperative assessment is required, a virtual trial reduction is desired, or intraoperative aids for realizing the planned surgical procedure are needed. The use, therefore, is not dictated by the pathology, but depends solely upon the availability of the software and hardware needed, and the willingness of the surgeon to apply these techniques and tools.

As for the conventional technique, a malunion has to be symptomatic resulting in pain with motion and loading in order to indicate an operative procedure. In extra-articular malunions, pain and reduced function mostly arises on the ulnar side of the wrist presenting as ulnocarpal impaction, incongruity, and/or instability of the distal radioulnar joint. In the radiocarpal joint symptoms result from intra-articular step-off, degenerative arthritis, concomitant ligamentous lesions and, in extra-articular malunions, extrinsic midcarpal instability. There still is not enough data for performing a preventive correction for nonsymptomatic extra-articular malunions, whereas an intra-articular step-off greater than 2 mm might be a more convincing argument being a prearthritic condition.

Nowadays, the minimal first step for a simple 3D analysis is easily available everywhere. Software for segmentation of CT scans can be downloaded for free. With this, at least the virtual radius can be moved in space and observed from any perspective. This permits to assess the orientation of the deformity, the fracture and the fragments in space, especially important and valuable because fracture planes, steps, and gaps are depicted in their true spatial orientation which almost never coincide with the routine projections and therefore tend to be underestimated.

According to the further sophistication of the software available, an increasing number of instruments can be applied: the virtual pathological radius (▶Fig. 23.1) can be compared with a healthy one (▶Fig. 23.2) allowing for exact calculation of the deformity, it may be cut in pieces mimicking osteotomies and aligned with the template answering on the feasibility of correction (▶Fig. 23.3). In fractures, the fragments can be moved until the fracture is reduced.

When these steps in the virtual model finally appear feasible and satisfactory, the preparation of execution of the surgery is done. Appropriate implants are selected and optimally located on the corrected virtual exemplar (▶Fig. 23.4). Implant site and the trajectories of the screws are implemented in the model (▶Fig. 23.4). Then the reduction process is reversed returning to the preoperative situation, now however with the afore created fragments carrying the screw and osteotomy trajectories (▶Fig. 23.5). Around these and along the bone surface, a mold can be created and prepared to serve as guide for saw cuts, ¹⁰ drill holes for the planned plate screws, joysticks for later reduction (▶Fig. 23.6). For intraarticular osteotomies, which usually do not cross the joint in a straight line, serial close meshed holes are drilled along the desired osteotomy line. ¹¹ Along these perforations, the bone can easily be broken creating a curved osteotomy line (▶Fig. 23.7). In the cases where locking (fixed angle) plates are used for fracture/osteotomy fixation, the screws inserted in the prepared holes are also used for reduction as their direction is predetermined and not variable. For other types of fixation, reduction guides are necessary. These guides need to be prepared upon the reduced virtual bone in the same manner as the first drill/cutting guide—they accommodate the aforementioned joysticks, now however in the reduced position.

23.3 Surgical Technique

The incision/approach is made according to the site where the position of the gigs and eventually the osteotomy and fixation are planned: palmar, dorsal, radial, or combined. The surface of the bone has to be cleaned meticulously, as (remember!) the gig has been planned with the CT-data, that is, the cortex. Thus, the periosteum and soft tissue has to be locally removed in order to permit an ideal fit of the gigs. Once an undisputed location and perfect fit is found, the gig is pressed on the bone surface and fixed there either by clamps or Kirschner wires (K wires). The holes in the gig are used to correctly place joysticks into the preliminary fragments, drill holes for later screws or for osteotomies, slots allow for perfectly oriented and sized saw cuts. After this the gig is removed, the osteotomies are completed and the fragments are mobilized enough to permit a smooth reduction. The precise reduction is controlled and guaranteed by the reduction guide slid over the prepared joysticks or the fixed-angle plate/screws inserted in one single direction, predefined by the plate/screw-hole geometry.

23.3.1 Extra-articular Malunion

The approach usually is palmar exposing the distal metaphysis of the radius after reflecting the pronator quadratus muscle. The palmar bone surface is flatter and disposes of much less bony landmarks than dorsal, which renders the unmistakable fit of the surface guides more difficult. Therefore, the adaptation of the guides requires the exposure of a larger contact surface or a shape with specs that embrace the radius (▶Fig. 23.8). At the beginning of our experience we used locking plates with a fixed angle of screw insertion. ¹² Thus, once the screw trajectories were drilled in the correct predetermined direction the plate positioning was unequivocally determined and the plate acted as a reduction device also. However, the screw placement in the distal fragment could not be adapted to the individual shape especially when this aberrated from the standard anatomy. This adaptation is possible using variable angle locking screws, which have become more and more popular, although at the expense of the virtue of the plate to serve as a reduction device. On the other hand, the predrilling of the holes through the guide that had to be removed before placing and attaching the plate seemed to be a superfluous additional step that is time consuming and fraught with potential error. Thanks to the fact that most extraarticular malunions present a “Colles deformity,” the plate can be attached to the distal fragment before completing the osteotomy, provided the shafts of the plate and the radius are oriented diverging in the exact amount and direction of the deformity (▶Fig. 23.9). In order to guarantee this, the space between the plate and the bone shaft has to be determined by the gig. This will present wedge-like therefore we call it a ramp-guide. The undersurface of this wedge-shaped gig fits to the distal radius metaphysis, incorporates a slot for the partial (ulnar sided) osteotomy (▶Fig. 23.10), and drill guides for the plate holes in the shaft. On the upper surface any desired plate can be fastened, which, provided the planning was been correct, fits exactly to the distal fragment (▶Fig. 23.11). Small imperfections of the contact surface can be corrected removing prominences with a rongeur or an osteotome. Then the distal plate is firmly fixed to the distal fragment, the ramp-guide is removed and the partial osteotomy is now completed (▶Fig. 23.12). After mobilization of the fragments, the plate can be attached to the proximal fragment and the shaft using the prepared screw holes, the osteotomy gap is filled with cancellous bone graft (▶Fig. 23.13). See ▶Fig. 23.14 for a clinical case of extra-articular malunion.

Related posts:

6 Is There a Role for External Fixation with or without Kirschner Wires? 12 Anterior Rim Fractures 18 Distal Ulna Fractures 28 Arthroscopic Management of Perilunate Dislocation and Fracture Dislocation 29 Radiocarpal Pain and Stiffness 13 Dorsal Rim Distal Radius Fractures with Radiocarpal Fracture-Dislocation

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