Patient Position Is Related to the Risk of Neurovascular Injury in Clavicular Plating: A Cadaveric Study
Authors: Chuaychoosakoon Chaiwat , Suwanno Porames , Boonriong Tanarat , Suwannaphisit Sitthiphong , Klabklay Prapakorn , Parinyakhup Wachirapan , Maliwankul Korakot , Duangnumsawang Yada , Tangtrakulwanich Boonsin 
Published: August 2019

Abstract

Background
Fixation of clavicle shaft fractures with a plate and screws can endanger the neurovascular structures if proper care is not taken. Although prior studies have looked at the risk of clavicular plates and screws (for example, length and positions) to vulnerable neurovascular structures (such as the subclavian vein, subclavian artery, and brachial plexus) in the supine position, no studies to our knowledge have compared these distances in the beach chair position.

Questions/purposes
(1) In superior and anteroinferior plating of midclavicle fractures, which screw tips in a typical clavicular plating approach place the neurovascular structures at risk of injury? (2) How does patient positioning (supine or beach chair) affect the distance between the screws and the neurovascular structures?

Methods
The clavicles of 15 fresh-frozen cadavers were dissected. A hypothetical fracture line was marked at the midpoint of each clavicle. A precontoured six-hole 3.5-mm reconstruction locking compression plate was applied to the superior surface of the clavicle by using the fracture line to position the center of the plate. The direction of the drill bits and screws through screw holes that offer the greater risk of injury to the neurovascular structures were identified, and were defined as the risky screw holes, and the distances from the screw tips to the neurovascular structures were measured according to a standard protocol with a Vernier caliper in both supine and beach chair positions. Anteroinferior plating was also assessed following the same steps. The different distances from the screw tips to the neurovascular structures in the supine position were compared with the distances in the beach chair position using an unpaired t-test.

Results
The risky screw holes were the first medial and second medial screw holes. The relative distance ratios compared with the entire clavicular length for the distances from the sternoclavicular joint to the first medial and second medial screw holes were 0.46 and 0.36 in superior plating and 0.47 and 0.37 in anteroinferior plating, respectively. The riskiest screw hole for both superior and anteroinferior plates was the second medial screw hole in both the supine and beach chair positions (supine superior plating: 8.2 mm ± 3.1 mm [minimum: 1.1 mm]; beach chair anteroinferior plating: 7.6 mm ± 4.2 mm [minimum: 1.1 mm]). Patient positioning affected the distances between the riskiest screw tip and the nearest neurovascular structures, whereas in superior plating, changing from the supine position to the beach chair position increased this distance by 1.4 mm (95% CI -2.8 to -0.1; supine 8.2 ± 3.1 mm, beach chair 9.6 ± 2.1 mm; p = 0.037); by contrast, in anteroinferior plating, changing from the beach chair position to the supine position increased this distance by 5.4 mm (95% CI 3.6 to 7.4; beach chair 7.6 ± 4.2 mm, supine 13.0 ± 3.2 mm; p < 0.001).

Conclusions
The second medial screw hole places the neurovascular structures at the most risk, particularly with superior plating in the supine position and anteroinferior plating in the beach chair position.

Clinical Relevance
The surgeon should be careful while making the first medial and second medial screw holes. Superior plating is safer to perform in the beach chair position, while anteroinferior plating is more safely performed in the supine position.