a Departamento de Ortopedia, Santa Casa de São Paulo, São Paulo, SP, Brasil
b Serviço de Ortopedia e Traumatologia, Hospital Israelita Albert Einstein, Universidade Federal de São Paulo (Unifesp), São Paulo, SP,Brasil
c Instituto de Ortopedia, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo (USP), São Paulo, SP, Brasil
d Escola Paulista de Medicina, Universidade Federal de São Paulo (Unifesp), São Paulo, SP, Brasil
Introduction
The clavicle has important anatomical relationships with thesubclavian artery, subclavian vein and brachial plexus, espe-cially in its middle third, where the curvature is the referencepoint used for accessing these structures. In cases of traumaand/or surgery in the middle third of the clavicle, and espe-cially is situations of fractures that need to be reduced andfixed by means of open surgery, Using synthesis material,these structures may become injured because of their anatom-ical proximity.
The brachial plexus is formed by the roots of C5, C6, C7,C8 and T1. It originates from the cervical spine, heads towardthe upper limbs and passes between the middle and ante-rior scalene muscles. The roots of C5 and C6 form the uppertrunk, from which the suprascapular nerve emerges. Eachtrunk divides into anterior and posterior portions when itpasses below the clavicle.
The right subclavian artery is a branch of the brachio-cephalic trunk and the left subclavian artery is a branch ofthe aortic arch. The reference anatomical structure for thesubclavian artery is the anterior scalene muscle, and this canbe found at the posteromedial border of this muscle or at itslateral border. The subclavian vein is a continuation of theaxillary vein and extends from the border of the first rib to themedial border of the anterior scalene muscle, where it joinsthe internal jugular vein to form the brachiocephalic vein. Theclavicle and the subclavian muscle are located anteriorly to thesubclavian vein.
The aim of this study was to establish a neurovascularsafety zone at the surgical access to the middle third of theclavicle, by means of dissection in cadavers.
Methods
Ten recently chilled cadavers were selected. Three werefemale and seven were male. Their mean age was 63.6 years(range: 55-73), mean height 1.67 m (1.58-1.73), mean weight62 kg (40.4-77) and mean BMI 22.1 kg/m2(16.1-25.65). They didnot present any congenital abnormalities, signs of trauma orprevious surgery in the shoulders studied. All the dissectionswere performed by the same group of researchers. A pilotstudy was initially conducted on the four shoulders of twocadavers, before data-gathering was started, in order to studyand gain better knowledge of the local anatomy (Table 1).
The procedures were performed with the cadaver in astandardized horizontal dorsal decubitus position, with a padunder the ipsilateral scapula and the upper limb in neutralposition. Using a surgical pen, the superficial anatomy of theclavicle and the acromioclavicular and sternoclavicular jointswas marked out on the skin. A transverse incision was made inthe skin along the entire length of the clavicle and the musclelayers were dissected, with exposure of the subclavian muscle(origin and insertion). Its relationship with the middle third ofthe clavicle was demonstrated using markers anteroinferiorly(Fig. 1).
After exposure of the muscle, the clavicle was divided intothree thirds and deeper dissection of the middle third wasperformed. In this, the following neurovascular structureswere identified: subclavian vein, upper trunk of the brachialplexus (anterior and posterior divisions) and suprascapularnerve. These structures were demarcated using colored mark-ers and the distances to the closest point of the middle thirdof the clavicle was recorded using a Kingtools®150 mm digitalpachymeter (Fig. 2).
For the statistical analysis, the paired Wilcoxon test wasused. The significance level adopted was 5% and the softwareused for the analysis was SAS version 9.2.
Results
The mean distances from the middle third of the clavicle to thesuprascapular nerve, subclavian vein, upper trunk, anterior
division of the upper trunk and posterior division of the uppertrunk on the right side were, respectively: 15.92 cm; 10.77 cm;23.68 cm; 14.60 cm; and 15.42 cm; and on the left side: 12.69 cm;9.82 cm; 22.19 cm; 12.16 cm; and 13.46 cm.
Table 2 presents the results from the measurements madebetween the middle third of the clavicle and the neurovascularstructures studied.
Discussion
The number of indications for surgical treatment of fracturesof the middle third of the clavicle has increased over theyears because of better understanding of the biomechanicsand function of the clavicle, the greater number of prospectivestudies demonstrating comparative results and the modern-ization of synthesis materials for fixation of these fractures.Today, some types of shortening and deformities are no longeracceptable.
According to Iannotti et al.6treatment of fractures of themiddle third of the clavicle through placement of a plate onits upper surface presented biomechanical advantages andfacilitated surgical access. However, Kloen et al.7demon-strated that iatrogenic lesions of the neurovascular structuresbelow the clavicle occurred more frequently in these types ofosteosynthesis and that the risk diminished when the platewas positioned anteroinferiorly.
Labrocini et al.10demonstrated that the branches of thesuprascapular nerve, which are responsible for the sensi-tivity on the clavicle, and the anteromedial region of theshoulder and proximal region of the chest are vulnerable incases of fractures of the clavicle and their surgical treatment.According to Sinha et al.4the structures at greatest risk ofinjury during osteosynthesis of the middle third of the clav-icle are the subclavian vein, subclavian artery, the brachialplexus and the pulmonary pleura. According to their study,the subclavian vein was closer to the middle third of the clav-icle than was the brachial plexus, with a mean distance of12.45 mm. In our study, the right subclavian vein was at amean distance of 10.77 mm and the left at 9.82 mm from the
middle third of the clavicle and was also the closest vascularstructure.4,10
According to Mouzopoulos et al.8the association betweenfractures of the clavicle and injuries to the brachial plexus iswell known and usually occurs due to high-energy supraclav-icular traction. Fractures of the clavicle are associated withthese events but are not the causal factor. In another study,by Della Santa et al.9it was demonstrated that direct traumaof the brachial plexus caused by fragments of the clavicleoccurred at low frequency (1%).
Jeyaseelan et al.11reported that involvement of the supras-capular nerve is a common finding in fractures of the clavicle,because this is the structure of the brachial plexus that isclosest to the middle third of the clavicle. Shortening of theclavicle and mobilization of the fragments of the fracture dur-ing fixation may cause compression of the brachial plexus, dueto the decreased infraclavicular space. In conservative treat-ment, the presence of the bone callus may also be the causeof lesions of the suprascapular nerve, due to compression. Inour study, the brachial plexus structure that was closest to themiddle third of the clavicle was the suprascapular nerve.
Therefore, according to the literature consulted, periclavic-ular neurovascular lesions are more associated with surgicaliatrogenic lesions than with the trauma itself. In our study,the neurovascular structures closest to the middle third ofthe clavicular and therefore most susceptible to injury in thisregion were the suprascapular nerve and subclavian vein,respectively. During our dissections, it was also observed thatthe subclavian muscle provided anterosuperior protection forthe adjacent neurovascular structures and that it could beused as an anatomical reference point for delimiting a "safetyzone".
Conclusion
There was a statistical difference in the distances from thesuprascapular nerve and the anterior division of the uppertrunk, comparatively between the right and left. The neu-rovascular structures closest to the middle third of the claviclewere the suprascapular nerve and subclavian vein.
Conflicts of interest
The authors declare no conflicts of interest.
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