Risk of axillary nerve injury during percutaneous proximal humerus locking plate insertion using an external aiming guide Neil Saran a , Stephane G. Bergeron a , Benoit Benoit b , Rudolf Reindl c , Edward J. Harvey d , Gregory K. Berry e, * a Division of Orthopaedic Surgery, Montreal General Hospital, McGill University Health Centre, 1650 Cedar Avenue Room L9.416, Montreal, Quebec H3G 1A4, Canada b University of Montreal, Division of Orthopaedic Surgery, Hoˆpital du Sacre ´ Coeur, 5400 Gouin Ouest, Local J-3245, Montreal, Quebec, Canada c Division of Orthopaedic Surgery, Montreal General Hospital, McGill University Health Centre, 1650 Cedar Avenue Room B5.159.2, Montreal, Quebec H3G 1A4, Canada d Division of Orthopaedic Surgery, Montreal General Hospital, McGill University Health Centre, 1650 Cedar Avenue Room B5.159.5, Montreal, Quebec H3G 1A4, Canada e Division of Orthopaedic Surgery, Montreal General Hospital, McGill University Health Centre, 1650 Cedar Avenue Room B5.159.4, Montreal, Quebec H3G 1A4, Canada Introduction Proximal humeral fracture fixation has recently undergone a significant transformation in both technique and implant hard- ware. These changes have attempted to preserve the biology of fracture healing in the face of extensive soft tissue injury. Injury to the ascending branch of the anterior circumflex humeral artery (ACHA) following a displaced proximal humerus fracture can result in partial or complete avascular necrosis (AVN) by disrupting the main blood supply to the humeral head. 7 The amount of dissection that is required with the traditional deltopectoral approach is thought to further contribute to the devascularisation of proximal humerus fractures at the time of internal fixation. 6,8,18 Minimally invasive techniques through a more lateral deltoid splitting exposure have been developed to avoid excessive surgical dissection during the deltopectoral approach to preserve the vascularity of the humeral head and minimise the risk of AVN and early collapse. 5,10 The use of locked plate technology has improved the treatment of osteoporotic proximal humerus fractures in the elderly. Several studies have reported favourable biomechanical and clinical outcomes following the use of these new devices. 1,3,4,9,10,12,15,16,19 Locking plates have been combined with minimally invasive techniques to provide biological fixation of proximal humerus fractures and promote fracture healing. A minimally invasive lateral deltoid splitting approach has been described using a proximal humerus locking plate that has shown good results for 2- part and 3-part valgus impacted proximal humerus fractures. 10 However, the accurate insertion of the locking screws without a percutaneous guide can be technically difficult as the traditional screw insertion guide block cannot be used percutaneously without risk of stretching the axillary nerve. 17 External guides Injury, Int. J. Care Injured 41 (2010) 1037–1040 ARTICLE INFO Article history: Accepted 14 April 2010 Keywords: Aiming arm Deltoid-splitting approach Neurological injury Fracture reduction Minimally invasive ABSTRACT Objectives: The purpose of this study was to determine which screws could be safely inserted percutaneously into a proximal humerus locking plate using a new external aiming guide without injuring the axillary nerve. We also sought to evaluate that all the screws could be accurately inserted in a locked position with the external guide. Methods: Eight cadaveric specimens were implanted with a proximal humerus locking plate using a minimally invasive direct-lateral deltoid splitting approach using an attached external aiming guide for screw insertion. The anatomic proximity of the axillary nerve to the guidewires and screws was measured following soft tissue dissection and inspection of the nerve. Results: The two superior holes (C1 and C2) were proximal to the axillary nerve with an average distance of 15.1 mm. Screw F was on average 6.6 mm distal to the axillary nerve but within 2 mm of the nerve in two specimens. In all specimens, the locking screws were appropriately seated in a locked position using the external aiming guide. Conclusions: This study suggests that percutaneous fixation of a proximal humerus locking plate with an external aiming guide can be safely used for proximal humerus fractures. The limited number of screws that can be inserted into the proximal fragment using the current external guide arm may compromise fixation of more unstable fractures. Therefore, the indications for percutaneous locking plate fixation of the proximal humerus using an external aiming guide should be limited to stable fracture patterns that can be anatomically reduced. ß 2010 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: +1 514 934 1934x42734; fax: +1 514 934 8453. E-mail address: greg.berry@muhc.mcgill.ca (G.K. Berry). Contents lists available at ScienceDirect Injury journal homepage: www.elsevier.com/locate/injury 0020–1383/$ – see front matter ß 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.injury.2010.04.014