Discussion

Masao made a cortical window at the apex of the radial styloid process through a 2 cm longitudinal skin incision centred over the radial styloid. He did not mention accurately the position of the entry point for the cortical window. In his clinical study, Masao did not report cases with extensor tendon rupture or irritation or screw penetration into the radiocarpal joint or DRUJ. Results of his clinical study will be mentioned in the discussion of the clinical study.40

Tan et al. used a 2 – 3 cm longitudinal skin incision over the radial styloid process as a surgical approach for treatment of distal radius fracture with Micronail™. They indicated that the best place for entry point for the cortical window is over the radial styloid 3 – 4 mm proximal to the apex of the

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radial styloid process between I. and II. extensor compartments. However, in this position the risk of disruption of the tip of the radial styloid or breach of the scaphoidal facet of the articular surface of the radius is great, because the diameter of the cannulated drill is 6.1mm. Also, in this position, the danger of screw penetration into the radiocarpal joint is very large. Tan et al. stated that it is preferable to make the entry point for the cortical window to the radial edge of the II. extensor compartment in the case of dorsal dislocation of the distal fragment and to the ulnar edge of the I. extensor compartment in the case of volar dislocation. Tan et al., in their clinical study, did not report complications in terms of tendon irritation or screw penetration into the radiocarpal joint or DRUJ.110

Vugt et al. placed the cortical window 3 mm proximal to the radioscaphoid joint between I. and II. extensor compartment. In this position, also, the risk of disruption of the tip of the radial styloid or breach of the scaphoidal facet of the articular surface of the radius is great. Vugt et al. did not observe complications in terms of tendon irritation or joint or cortical screw penetration.111

Dantuluri used the same approach, but the entry point was placed 5 mm proximal to the tip of the radial styloid process between I. and II. extensor compartments, and pointed out how cortical entry point of Micronail must be proximally enough to avoid disruption of the radial styloid process or breach of the scafoidal facet of the articular surface of the radius. At the same time, it must not be too proximally so as to avoid non-subchondral displacement of the screws. Then, he extended cortical window about 0.5 cm proximally while preparing a channel of a suitable size for Micronail with the aid of rasps.112 Shin described the same surgical approach with the placement of the cortical window between I. and II. extensor compartments without stating the proper distance from the tip of radial styloid process. In these studies, the angle in the transverse plane, in which the implant is to be implemented, was not mentioned.38

In this experimental study, in 89% of the attempts, in which Micronail™ was placed 5mm from the tip of the radial styloid, there was screw penetration to the radiocarpal joint. During rasping, almost always a minor extension in cortical window proximally occurred that makes the distal end of Micronail™ be more proximally than the original bone entry point. This may explain why there was no screw penetration to the radiocarpal joint space in the aforementioned works. In our study, the final placement of the distal end of the implant was exactly in the original entry point.

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In their clinical study, Ilyas et al. stated, that in 3 patients from 10 was screw penetration into DRUJ. However, in our studies, clinical and experimental, there were no cases of screw penetration into DRUJ.113

Orbay and Brooks described the insertion technique of the implant Dorsal Nail Plate (Hand Innovations LLC, Miami, FL, USA) (Fig. 27a). This implant is considered a hybrid implant that combines a small distal plate and an intramedullary nail. The device uses 4 distal locking fixed angle screws to support the subchondral bone of the distal radius. Indications and contraindications of the use of this implant are the same as Micronail™. The insertion of the nail needs 3-4cm skin incision on the dorsal side of the distal radius over Lister prominent. After preparation of the superficial branch of the radial nerve, EPL tendon is released and Lister tubercle is removed. The cortical window is placed in the proximal fragment in parallel with III. extensor compartment. The distal edge of implant has to be 4mm from the radiocarpal joint line and just sit on the dorsal cortex. Orbay treated 200 patients with distal radial fractures using DNP and demonstrated excellent results with low rate complications.108,114

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Rampoldi treated 47 patients with extra-articular (36 cases) or simple articular (11 cases) fractures using Dorsal Nail Plate®. He reported two intra-operative complications of partial laceration of the EPL tendon that was damaged between the implant and the dorsal cortex of the radius during nail introduction. Loss of initial reduction was observed in two fractures.109 Using Micronail™, however,

the skin incision is smaller, the EPL tendon is not released and Lister tubercle is not removed. Plate portion of the implant Dorsal Nail Plate remains on the dorsal surface of the distal radius, which can lead to extensor tendon injury or irritation.

Gradl et al. used the Targon DR® nail (B. Braun-Aesculap, Tuttlingen, Germany) (Fig. 27b) in the treatment of extra-articular fractures of the distal radius with dorsal comminution and articular fractures without displacement and with a sagittal fracture line. The entry point for the nail was performed between I. and II. extensor compartment and 2 - 3 mm from the tip of the radial styloid. They treated 103 patients with this implant. 95 patients experienced the 8-week follow-up, 50 patients the 1-year follow-up. They reported good to excellent outcomes.115

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