title: Solid and hollow pedicle screws affect the electrical resistance: A potential source of error with stimulus-evoked electromyography.
abstract: BACKGROUND
  Although stimulus evoked electromyography (EMG) is commonly used to confirm the accuracy of pedicle screw placement. There are no studies to differentiate between solid screws and hollow screws to the electrical resistance of pedicle screws. We speculate that the electrical resistance of the solid and hollow pedicle screws may be different and then a potential source of error with stimulus-evoked EMG may happen.
  
  
  METHODS
  Resistance measurements were obtained from 12 pedicle screw varieties (6 screws of each manufacturer) across the screw shank based on known constant current and measured voltage. The voltage was measured 5 times at each site.
  
  
  RESULTS
  Resistance of all solid screws ranged from 0.084 Ω to 0.151 Ω (mean =0.118 ± 0.024 Ω) and hollow screws ranged from 0.148 Ω to 0.402 Ω (mean = 0.285 ± 0.081 Ω). There was a significant difference of resistance between the solid screws and hollow screws (P < 0.05). The screw with the largest diameter no matter solid screws or hollow screws had lower resistance than screws with other diameters. No matter in solid screws group or hollow screws group, there were significant differences (P < 0.05) between the 5.0 mm screws and 6.0 mm screws, 6.0 mm screws and 7.0 mm screws, 5.0 mm screws and 7.0 mm screws, 4.5 mm screws and 5.5 mm screws, 5.5 mm screws and 6.5 mm screws, 4.5 mm screws and 6.5 mm screws. The resistance of hollow screws was much larger than the solid screws in the same diameter group (P < 0.05).
  
  
  CONCLUSIONS
  Hollow pedicle screws have the potential for high electrical resistance compared to the solid pedicle screws and therefore may affect the EMG response during stimulus-evoked EMG testing in pedicle screw fixation especially in minimally invasive percutaneous pedical screw fixation surgery.
authors: Department of Orthopaedics, Xinqiao Hospital, Chongqing, China.
authors: Hongwei
authors: H
authors: Wang
authors: Xinhua
authors: X
authors: Liao
authors: Xianguang
authors: X
authors: Ma
authors: Changqing
authors: C
authors: Li
authors: Jianda
authors: J
authors: Han
authors: Yue
authors: Y
authors: Zhou
keywords: Electrical resistance; electromyography; pedicle screw; percutaneous pedicle screw
references: Spine (Phila Pa 1976). 1996 Mar 1;21(5):600-4
references: 8852316
references: J Neurosurg Spine. 2007 Feb;6(2):126-32
references: 17330579
references: Spine J. 2006 Nov-Dec;6(6):708-13
references: 17088202
references: Spine (Phila Pa 1976). 2002 Jul 15;27(14):1577-81
references: 12131721
references: Bosn J Basic Med Sci. 2009 Oct;9 Suppl 1:77-82
references: 19912122
references: J Spinal Disord Tech. 2004 Aug;17(4):277-83
references: 15280755
references: Spine (Phila Pa 1976). 1988 Sep;13(9):1012-8
references: 3206294
references: Spine (Phila Pa 1976). 2001 Dec 1;26(23):2521-32; discussion 2532-4
references: 11725230
references: Spine (Phila Pa 1976). 1991 May;16(5):576-9
references: 2053001
references: Spine (Phila Pa 1976). 1993 Nov;18(15):2231-8; discussion 2238-9
references: 8278838
references: Spine (Phila Pa 1976). 2007 Nov 15;32(24):2673-8
references: 18007243
references: J Neurosurg. 2002 Jul;97(1 Suppl):7-12
references: 12120655
references: Neurosurgery. 2002 Nov;51(5 Suppl):S166-81
references: 12234445
references: Clin Orthop Relat Res. 1988 Dec;(237):125-31
references: 3191620
references: Spine (Phila Pa 1976). 1992 Jun;17(6 Suppl):S184-9
references: 1631716
references: Spine (Phila Pa 1976). 1990 Nov;15(11):1159-65
references: 2267611
references: Spine (Phila Pa 1976). 1987 Mar;12(2):160-6
references: 3589807
references: J Spinal Disord Tech. 2005 Dec;18(6):515-8
references: 16306841
references: J Neurosurg Spine. 2010 May;12(5):533-9
references: 20433301
references: Clin Orthop Relat Res. 1986 Feb;(203):45-53
references: 3955996
references: Spine (Phila Pa 1976). 1996 Jun 1;21(11):1320-4
references: 8725923
references: Spine (Phila Pa 1976). 1990 Jan;15(1):11-4
references: 2326693
references: Spine (Phila Pa 1976). 1992 Oct;17(10):1229-35
references: 1440014
references: Minim Invasive Neurosurg. 2005 Oct;48(5):273-7
references: 16320188
references: Spine (Phila Pa 1976). 1995 May 1;20(9):1068-74
references: 7631237
references: J Neurosurg Spine. 2010 Nov;13(5):600-5
references: 21039151