7.1 Introduction

In recent years, the treatment of distal radius fracture has seen a significant change in trend, moving away from conservative treatment towards surgical treatment. Secondary dislocation after an initially good reduction outcome, inadequate restoration of the articular surface after closed reduction in the case of intra-articular fractures, and a long period of wrist immobilization often lead to unsatisfactory outcomes. Using the osteosynthesis methods of Kirschner wire (K-wire) fixation and the external fixator, it was often impossible to achieve satisfactory anatomical reduction and long-term retention. The difficulty with plate osteosynthesis, especially in the case of a dorsal comminuted fracture zone and intraarticular fractures, was that in the distal comminuted fracture zone, standard screws are insecure and it was often necessary to perform a cancellous bone graft as well. In addition, it was not always possible to make plate design meet the requirements for accurate reduction and retention; therefore, there are often scar problems and misaligned healing.

Only upon introduction of fixed-angle plates and ultimately also multidirectional fixed-angle plates, it was possible to solve many of these problems. ¹ Locking plates act as an internal fixator where the screws are locked in the plate and by that can stabilize comminuted areas till bony healing is present. Fixed-angle plates are always preferable for osteosynthesis of unstable distal radius fractures because, with this method, the risk of secondary dislocation of the fragments is much lower. Palmar fixed-angle plate osteosynthesis now represents the preferred method of osteosynthesis and allows long-term anatomical retention of the articular surface, especially in cases of intra-articular involvement. In the case of fractures with a pronounced dorsal comminuted fracture zone or a dislocation that cannot be reduced from palmar, the development of special dorsal osteosynthesis plates has brought about considerable progress. Additionally, arthroscopically assisted fracture management with a direct view of the radius articular surface allows precisely examining the reduction. ²

7.2 Locking Mechanisms

A distinction is made between unidirectional and multidirectional fixed-angle plates as well as between palmar and dorsal use thereof. In the case of unidirectional fixed angles, the direction of the screw is dictated by the plate. This is often adequate if plate position is optimal. However, if the plate has to be positioned far distal or far proximal on account of the fracture situation, there is a risk of an intra-articular screw position or suboptimal support of the articular surface because the screws can no longer be positioned subchondral.

With the multidirectional fixed-angle plate, the screws can be introduced in various directions with a lateral deviation of up to approximately 15° from the perpendicular position. This permits screw positioning that is customized, fracture-oriented, and adapted to plate position. ³

There are three fundamentally different methods of locking the screw head with the plate.

Applying the principle of material deformation, a hard external thread in the region of the screw head cuts into the softer plate material. The drawback with this is that if the screw direction is adjusted, the screw head tends to take the path of least resistance and returns to the original direction. In addition, when the plate is removed, there is the problem of cold fusion between the screw head and the plate, which makes sometimes removal impossible or leads to breakage of the screw head.

Another method often used is to interlock the screw by engaging an external thread in the head section with an internal thread in the plate section. However, the disadvantage of this is that in the interlock, the screw head seeks the path of least resistance and thus counteracts the variability of screw direction.

A more recent method is spherical head space locking in which, during insertion of the screw head into the plate, friction grip occurs when resistance has been overcome; by that, a kind of wedging takes place between the screw head and the plate (▶Fig. 7.1). This creates the advantage of infinite locking without the risk of any cold fusion. In addition, with this method, the plate design can be kept very flat and metal removal, when indicated, is possible without any problems.

7.3 Indications

7.3.1 Plate Design and Plate Position

The historical shape of the palmar radius plate is represented by the traditional T-plate (▶Fig. 7.2 ). Later on, with the development of the multidirectional locking plates, the principles of two distal rows were established to provide better support of the articular surface, especially in case of severe comminution and osteoporosis (▶Fig. 7.3 ). Through the distal row, the screws can be placed exactly in the subchondral area, which represents the most stable part and through the proximal row, support of the dorsal aspect of the radius is possible (▶Fig. 7.4 ).

Secondary ruptures of the flexor tendons, especially the long thumb flexor tendon (flexor pollicis longus [FPL] tendon), are a feared complication. Prominent distal plate rims and projecting screw heads increase the risk of a rupture. ⁴ For this reason, plates were developed with a low-profile design as well as special plates that are recessed in the region of the FPL tendon, thus minimizing the secondary rupture risk.

With the recognition of the anatomical shape of the radius, the term watershed line was established as the distal border of plate position to avoid flexor tendon injuries. ⁵ Based on this concept, plates with watershed design were developed to allow far distal placement, especially for the so-called troublesome lunate facet fragments (▶Fig. 7.4 ). To support the lunate area far distal, the FPL design was created, which spares the floor of FPL tendon completely (▶Fig. 7.5 ). Limits for fracture plate fixation alone are seen in case of rim fractures, which require additionally fragment-specific fixation by small hook plates, tiny screws, or even tension band techniques, which is described in Chapter 12. ⁶

The distal and palmar prominence of the plates is defined by Soong line (▶Fig. 7.6 ). Soong 0 describes an optimal plate position. In Soong 1, the distal plate end exhibits palmar prominence. In Soong 2, there is palmar and distal plate prominence, which requires absolutely hardware removal. ^{7 , 8}

Related posts:

6 Is There a Role for External Fixation with or without Kirschner Wires? 18 Distal Ulna Fractures 21 Extra-articular Malunion 29 Radiocarpal Pain and Stiffness 25 Open Surgery for Chronic Scapholunate Injury 16 Radiocarpal Dislocation

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