The usage of the external fixation apparatus in arthroscopy of the wrist joint: from experiment to practice

Rationale: Distal radius fracture (DRF) occupy a leading place in the structure of fractures of the upper limb. Adequate reposition of fragments in intraarticular fractures is acceptable with arthroscopic control, which is carried out under conditions of distraction. Existing devices make it difficult to X-ray control after osteosynthesis with a volar plate, and therefore a method of distraction of the carpal joint in the external fixation apparatus (EFA) is proposed. Objective: To assess changes in the relationship of the topographic-anatomical elements of the carpal joint in the conditions of EFA, as well as to study the effect of these changes on arthroscopy. Methods: The study was conducted on the cadaver upper extremities (n = 16). Prior to the manipulations, the distance from standard arthroscopic ports to the main anatomical structures (e.g., the sensitive branches n.radialis and n.ulnaris) was measured. The carpal joint was then subjected to distraction in the EFA and the distances were re-measured. Results: From port 1-2, the average distance to the dorsal and volar branches of n.radialis was 3±1.4 mm and 4±2.3 mm, respectively. A. radialis was located in 3.4±1.7 mm. After the installation of EFA, the distance to the nearest surface branch of n.radialis did not change: 3±1.9 mm, p = 0.98. From the 3-4 port to the sensitive branches of n.radialis, the distance was 14±4.5 mm, and to a.radialis - 25±3.7 mm. The distance from port 4-5 to the dorsal branch of n.ulnaris was 58±14 mm. Therefore, the distance from ports 3-4 and 4-5 was not measured after the installation of the EFA. The smallest distance to the sensory nerves was observed when using port 6R (2±1.6 mm), which did not change during distraction under EFA conditions (2±1.8 mm; p = 0.93). Discussion: The most "dangerous” (i.e. those with the maximum risk of damage to anatomical structures) were ports 1-2 and 6R. Port 1-2 has already been described in the literature as the closest to the surface branch of n. radialis in the cadaver experiment. However, port 6R is considered "safe” in the literature, which was not confirmed in our experiment. The most "safe” ports (i.e. those with minimal risk of damage to anatomical structures) were ports 3-4 and 4-5, since the distance to the arteries and nerves was more than 1 cm in all measurements. Given the safety of the method, it was proposed to introduce it into practice, which is confirmed by clinical observation. Conclusion: The study demonstrated the safety of performing arthroscopy in the conditions of EFA. The proposed technique did not affect the mutual location of the anatomical structures of the wrist joint and did not lead to an increase in the risk of their damage during arthroscopy. Clinical observation made it possible to assess the possibility of practical application of the proposed technique.