Abstract
Background
Recent advances in intramedullary (IM) nailing have focused on removing free play
at the nail-screw interface to provide enhanced construct torsional stiffness. These
changes also increase axial construct stiffness and reduce axial interfragmentary
movement, which is required for optimal secondary fracture healing. This study tested
whether a novel intramedullary nail, the Flexible Axial Stimulation (FAST) nail, can
simultaneously provide controlled axial interfragmentary motion with enhanced torsional
stiffness.
Methods
Novel tibial nails and matched controls (N = 6 per group) were tested in a cadaveric osteotomy fracture model and in explanted
bench testing. In cadaver and bench tests, nails were tested in axial tension/compression,
torsion, bending, and shear. Overall construct stiffness values were calculated in
each loading mode and axial and torsional low-load micromotion plateaus were quantified.
Findings
The novel nails produced 1 mm of controlled axial interfragmentary motion, which was associated with a 22% reduction
in axial stiffness compared to standard controls (P = 0.026, effect size 2.5). The novel constructs also allowed less low-load torsional
movement compared to the controls (3.8 deg vs. 7.1 deg, P = 0.010, effect size 1.9), which was associated with a 14% increase in overall construct
torsional stiffness (P = 0.003, effect size 1.3). There were no observable differences in performance between
the novel and control nails in anteroposterior/mediolateral bending or shear.
Interpretation
These results suggest that an IM nailing construct can provide axial interfragmentary
motion while retaining high torsional stiffness, a combination which may potentially
enhance healing.
Keywords
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References
- Trial to Evaluate the Effectiveness of Angular Stable Locking System (ASLS) in Patients with Distal Tibial Fractures.([Online]) U.S. National Institutes of Health, 2009 (Available: http://clinicaltrials.gov/ct2/show/study/NCT00875992 [Accessed 6 Jan 2012])
- Shear movement at the fracture site delays healing in a diaphyseal fracture model.J. Orthop. Res. 2003; 21: 1011-1017
- Interfragmentary movement in diaphyseal tibia fractures fixed with locked intramedullary nails.J. Orthop. Trauma. 2008; 22: 30-36
- Phoenix Tibial Nail System Surgical Technique.Biomet, Inc., Parsippany, NJ, USA2007
- Far cortical locking can reduce stiffness of locked plating constructs while retaining construct strength.J. Bone Joint Surg. Am. 2009; 91A: 1985-1994
- Effects of construct stiffness on healing of fractures stabilized with locking plates.J. Bone Joint Surg. Am. 2010; 92A: 12-22
- Failure of less invasive stabilization system plates in the distal femur — a report of four cases.J. Orthop. Trauma. 2004; 18: 565-570
- Influence of size and stability of the osteotomy gap on the success of fracture healing.J. Orthop. Res. 1997; 15: 577-584
- Mechanical validation of whole bone composite tibia models.J. Biomech. 2000; 33: 279-288
- A novel intramedullary nail for micromotion stimulation of tibial fractures.Clin. Biomech. 2012; 27: 182-188
- The dynamic locking screw (DLS) can increase interfragmentary motion on the near cortex of locked plating constructs by reducing the axial stiffness.Langenbecks Arch. Surg. 2010; 395: 421-428
- Timely fracture-healing requires optimization of axial fixation stability.J. Bone Joint Surg. Am. 2007; 89A: 1575-1585
- Dynamic interfragmentary motion in fractures during routine patient activity.Clin. Orthop. Relat. Res. 1997; : 216-225
- Strain rate and timing of stimulation in mechanical modulation of fracture healing.Clin. Orthop. Relat. Res. 1998; : S105-S115
- Structural properties of a new design of composite replicate femurs and tibias.J. Biomech. 2001; 34: 773-781
- Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures: a biomechanical study.Injury. 2009; 40: 767-771
- Angle stable locking reduces interfragmentary movements and promotes healing after unreamed nailing — study of a displaced osteotomy model in sheep tibiae.J. Bone Joint Surg. Am. 2005; 87A: 2028-2037
- Closed locked intramedullary nailing — its application to comminuted fractures of the femur.J. Bone Joint Surg. Am. 1985; 67: 709-720
- Controlled mechanical stimulation in the treatment of tibial fractures.Clin. Orthop. Relat. Res. 1989; 36–47
- Axial movement and tibial fractures — a controlled randomized trial of treatment.J. Bone Joint Surg. Br. 1991; 73: 654-659
- Tibial external fixation, weight bearing, and fracture movement.Clin. Orthop. Relat. Res. 1993; 28–36
- The evolution of locked plates.J. Bone Joint Surg. Am. 2006; 88A: 189-200
- Influence of intramedullary nail diameter and locking mode on the stability of tibial shaft fracture fixation.Arch. Orthop. Trauma Surg. 2009; 129: 525-531
- Primary bone healing — an experimental study in the rabbit.J. Bone Joint Surg. Am. 1971; A53: 783-786
- The course of bone healing is influenced by the initial shear fixation stability.J. Orthop. Res. 2005; 23: 1022-1028
- TRIGEN META-NAIL Tibial Nail System—Surgical Technique.Smith & Nephew Inc., Memphis, TN, USA2007
- First clinical results of the locking compression plate (LCP).Injury. 2003; 34: 43-54
- Expert Tibial Nail Technique Guide.Synthes GmbH, Oberdorf, Switzerland2006
- Angular Stable Locking System (ASLS) Technique Guide.Synthes GmbH, Oberdorf, Switzerland2008
- Dynamic Locking Screw (DLS) System Technique Guide.Synthes USA, West Chester, Pennsylvania, USA2011
- Internal plate fixation of fractures: short history and recent developments.J. Orthop. Sci. 2006; 11: 118-126
- Internal loads in the human tibia during gait.Clin. Biomech. 2009; 24: 299-302
- The effects of external mechanical stimulation on the healing of diaphyseal osteotomies fixed by flexible external fixation.Clin. Biomech. 1998; 13: 359-364
- Zimmer Natural Nail System.Zimmer, Inc., Warsaw, IN, USA2010
Article info
Publication history
Published online: May 17, 2013
Accepted:
April 16,
2013
Received:
September 27,
2012
Identification
Copyright
© 2013 Elsevier Ltd. Published by Elsevier Inc. All rights reserved.
