Impact of Screw Length on Proximal Scaphoid Fracture Biomechanics

Abstract

Background Proximal scaphoid fractures display high nonunion rates and increased revision cases. Waist fracture fixation involves maximizing screw length within the cortex; however, the optimal screw length for proximal scaphoid fractures remains unknown.

Purpose The main purpose of this article is to compare stiffness and ultimate load for proximal scaphoid fracture fixation of various headless compression screw lengths.

Methods Eighteen scaphoids underwent an osteotomy simulating a 7 mm oblique proximal fracture. Screws of three lengths (10, 18, and 24 mm) were randomly assigned for fixation. Each specimen underwent cyclic loading with stiffness calculated during the last loading cycle. Specimens that withstood cyclic loading were loaded to failure.

Results No significant difference in stiffness between screw lengths was found. Ultimate load was significantly impacted by the screw length. A significant difference in ultimate load between a 10 and 24 mm screw was found; however, no significant difference occurred in ultimate load between an 18 and 24 mm screw.

Conclusions No significant difference in stiffness between all groups could be due to similarities in purchase in the proximal aspect. The 10 mm screw withstanding less ultimate load compared to the 24 mm screw could be due to the 10 mm screw gaining less purchase on either side of the fracture site compared to the 24 mm screw. Lack of significant difference in ultimate load between the 18 and 24 mm screw could be occurring because the fracture site is closer to the 18 mm screw midpoint, as distal threads are engaged closer to the fracture.

Clinical Relevance Maximizing screw length may not provide superior fixation biomechanically compared with fixation utilizing a 6 mm shorter screw for proximal scaphoid fractures.

Keywords

screw length - fixation - proximal scaphoid - biomechanics

• References

• 1 Al-Ashhab ME, Elbegawi HEA. Percutaneous screw fixation for scaphoid fractures. Orthopedics 2017; 40 (04) e729-e734
• 2 Duckworth AD, Jenkins PJ, Aitken SA, Clement ND, Court-Brown CM, McQueen MM. Scaphoid fracture epidemiology. J Trauma Acute Care Surg 2012; 72 (02) E41-E45
• 3 Sugathan HK, Kilpatrick M, Joyce TJ, Harrison JW. A biomechanical study on variation of compressive force along the Acutrak 2 screw. Injury 2012; 43 (02) 205-208
• 4 Trumble TE, Vo D. Proximal pole scaphoid fractures and nonunion. J Hand Surg Am 2001; 1–3: 155-171
• 5 Fowler JR, Ilyas AM. Headless compression screw fixation of scaphoid fractures. Hand Clin 2010; 26 (03) 351-361
• 6 Szabo RM, Manske D. Displaced fractures of the scaphoid. Clin Orthop Relat Res 1988; (230) 30-38
• 7 McQueen MM, Gelbke MK, Wakefield A, Will EM, Gaebler C. Percutaneous screw fixation versus conservative treatment for fractures of the waist of the scaphoid: a prospective randomised study. J Bone Joint Surg Br 2008; 90 (01) 66-71
• 8 Rettig ME, Kozin SH, Cooney WP. Open reduction and internal fixation of acute displaced scaphoid waist fractures. J Hand Surg Am 2001; 26 (02) 271-276
• 9 Rettig ME, Raskin KB. Retrograde compression screw fixation of acute proximal pole scaphoid fractures. J Hand Surg Am. 1999; 24 (06) 1206-1210
• 10 Yip HS, Wu WC, Chang RY, So TY. Percutaneous cannulated screw fixation of acute scaphoid waist fracture. J Hand Surg [Br] 2002; 27 (01) 42-46
• 11 Clay NR, Dias JJ, Costigan PS, Gregg PJ, Barton NJ. Need the thumb be immobilised in scaphoid fractures? A randomised prospective trial. J Bone Joint Surg Br 1991; 73 (05) 828-832
• 12 McCallister WV, Knight J, Kaliappan R, Trumble TE. Central placement of the screw in simulated fractures of the scaphoid waist: a biomechanical study. J Bone Joint Surg Am 2003; 85-A (01) 72-77
• 13 Rettig AC. Management of acute scaphoid fractures. Hand Clin 2000; 16 (03) 381-395
• 14 Beutel BG, Melamed E, Hinds RM, Gottschalk MB, Capo JT. Mechanical evaluation of four internal fixation constructs for scaphoid fractures. Hand (N Y) 2016; 11 (01) 72-77
• 15 Faucher GK, Golden III ML, Sweeney KR, Hutton WC, Jarrett CD. Comparison of screw trajectory on stability of oblique scaphoid fractures: a mechanical study. J Hand Surg Am 2014; 39 (03) 430-435
• 16 Luria S, Lenart L, Lenart B, Peleg E, Kastelec M. Optimal fixation of oblique scaphoid fractures: a cadaver model. J Hand Surg Am 2012; 37 (07) 1400-1404
• 17 Dodds SD, Panjabi MM, Slade III JF. Screw fixation of scaphoid fractures: a biomechanical assessment of screw length and screw augmentation. J Hand Surg Am 2006; 31 (03) 405-413
• 18 Heaton DJ, Trumble T, Rhodes D. Determination of the central axis of the scaphoid. J Wrist Surg 2015; 4 (03) 214-220
• 19 Erhart J, Unger E, Schefzig P. , et al. Rotational stability of scaphoid osteosyntheses: an in vitro comparison of small fragment cannulated screws to novel bone screw sets. PLoS One 2016; 11 (06) e0156080
• 20 Gruszka D, Herr R, Hely H. , et al. Impact of different screw designs on durability of fracture fixation: in vitro study with cyclic loading of scaphoid bones. PLoS ONE 2016; 11 (01) e0145949