Disclosures Synthes A Biomechanical Comparison Between Superior and - - PowerPoint PPT Presentation

5/8/2014 1

A Biomechanical Comparison Between Superior and Anterior Plating Positions for Mid-Shaft Clavicle Fractures Using Pre-contoured Plates

Paul Toogood, MD/MS, Dezba Coughlin, PhD, David Rodriguez, Jeffery Lotz, PhD, Brian Feeley, MD

Disclosures

Synthes OREF JOJ

Background

Historic data suggested

extremely low non-union rates with mid-shaft clavicle fractures

Neer, JAMA, 1960:

2235 non-

• peratively treated

clavicles

3 nonunions

Nonoperative Treatment Compared with Plate Fixation of Displaced Midshaft Clavicular Fractures

• Multicenter, prospective RCT
• N = 132
• 67 ORIF
• 65 sling
• Outcomes
• DASH
• Constant Score
• Radiographic/clinical f/u
• DASH:
• Better in ORIF at all time points up to 1 yr
• Constant Score:
• Better in ORIF at all time points up to 1 yr
• Time to Union:
• ORIF: 16.4 wks
• Sling: 28.4 wks
• Non-unions:
• ORIF: 2
• Sling: 7
• Complications:
• ORIF: 37% (hardware irritation, infection)
• Sling: 63% (non-union, malunion requiring

treatment

Canadian Orthopaedic Trauma Society JBJS, 2007

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Plate Position

Anterior Superior

1) Less prominent (less ROH) 2) Longer anterior-posterior screw purchase 3) Instrumentation away from at risk neurovascular structures 1) Flat surface 2) Less muscular stripping

Prior Literature

• No clinical comparisons
• Biomechanical Data:

Celestre, 2008, JOT Harnroongroj, 1996, Clin

Biomech

Iannotti, 2002, JSES Robertson, 2009, JSES Taylor, 2011, Clin Biomech Partal, 2010, JOT

Favored superior plating Favored anterior plating

Prior Literature: Limitations

Author Implants Loading Fracture Model Harnroongroj, 1996 1/3rd Tubular Bending Transverse Fx Iannotti, 2002 Reconstruction Compression, Torsion Transverse Fx Celestre, 2008 DCP Compression, Torsion, Bending Transverse Fx Robertson, 2009 Reconstruction Compression, Torsion, Bending Transverse Fx Partal, 2010 Reconstruction Compression, Torsion, Bending Transverse Fx Taylor, 2011 Pre-contoured Bending Transverse Fx

Transverse Fracture Pattern

Epidemiologic data suggests these fractures are uncommon (~5%) clinically2. Prior authors admit it is also uniquely stable fracture pattern12,15..

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Purpose

To biomechanically compare superior and

anterior plating positions of:

Clinically relevant mid-shaft clavicle fracture

patterns

Using pre-contoured plates When loaded in axial compression, torsion, and

cantilever bending.

Methods: Fracture Model

OTA/AO/ASIF Classification

• Oblique Fracture Pattern (B1.2):
• Single most common fracture pattern

(26.3%)2.

• More reproducible than the spiral pattern,

and less tested than the transverse pattern.

Methods: Fracture Model

• Bending Wedge Fracture Pattern

(B2.2):

• The entire B2 category is

amongst the more common fracture patterns (28.9%)2.

• Of the three, it was felt the

Bending wedge would be the most reproducible.

Methods: Fracture Model

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• Comminuted Fracture Pattern (B3.3):
• When segmental fractures occur, they are
• verwhelmingly comminuted (79.9%)2.

Methods: Fracture Model Methods: Fracture Model

B1.2: 32 degrees, superior-lateral to inferior medial B2.2: Wedge will be 16% of clavicular length B3.3: Comminuted section will be 21% of clavicular length

x75

Methods: Clavicle Model

Synthetic clavicles (Pacific Research Laboratories

model 3408-1)

Easier to obtain Reduces variability in bone geometry and quality > 2 testing groups Now produce an intact model

Methods: Implants

1) Pre-contoured Superior Left Locking Mid-shaft Clavicle Plate, 8-hole 2) Pre-contoured Anterior Left Locking Mid-shaft Clavicle Plate, 8-hole

Three locking screw on each side of the fracture Lag screws placed across

• blique and wedge patterns

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Methods: Loading

Compression Torsion Cantilever bending

12 Oblique B1.2 12 Bending Wedge B 2.2 12 Complex Comminuted B 3.3

6 Superiorly Plated 6 Superiorly Plated 6 Superiorly Plated 6 Anteriorly Plated 6 Anteriorly Plated 6 Anteriorly Plated

Torsion Axial Compression Cantilever Torsion Axial Compression Cantilever Torsion Axial Compression Cantilever Torsion Axial Compression Cantilever Torsion Axial Compression Cantilever Torsion Axial Compression Cantilever

Osteotomy Osteotomy

Results: Axial Compression

Superior stiffer than anterior for all fracture patterns Oblique stiffer than wedge & comminuted patterns

Oblique Wedge Comminuted 3142 1657 1257 2873 1212 1008

Axial Compression

Superior Plate Anterior Plate

Results: Torsion

Superior stiffer than anterior for all fracture patterns, except no difference oblique fx clockwise torsion* Oblique stiffer than wedge & comminuted patterns

Oblique Wedge Comminuted 914 650 578 973 455 465

Torsion Clockwise

Superior Plate Anterior Plate Oblique Wedge Comminuted 805 573 552 735 433 418

Torsion Counter-Clockwise

Superior Plate Anterior Plate

*

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Results: Cantilever Bending

Anterior stiffer than superior for all fracture patterns Oblique stiffer than wedge & comminuted patterns

Oblique Wedge Comminuted 100 41 25 116 69 75

Cantilever Bending

Superior Plate Anterior Plate

Anterior Plate

Resistance to

Cantilever bending

Lies with a larger

dimension (width) perpendicular to the line of force

Anterior Superior

Superior Plate

Resistance to Torsion

Greater mass (18.5 vs

13 gm)

S-shape

Moves mass away from

centeroid, increasing polar moment of inertia

Resistance to

Compression

Flat along axis of

compression

Superior Anterior

Limitations

Little is know about in vivo loading of the clavicle Clinical failure is fatigue vs construct stiffness Sequential testing

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Conclusions

Current study suggests that for multiple mid-

shaft clavicle fracture patterns:

Compression and torsion appear better controlled with

a pre-contoured superior plate

Cantilever bending is bettered resisted by the improved

areal moment of inertia of the pre-contoured anterior plate

Until the relative importance of these forces is

known, reasons other than biomechanics should be used to determine plate position

References

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• 2) Robinson CM. Fractures of the clavicle in the adult: Epidemiology and classification. J Bone Joint Surg [Br]. 1998;80-B:476-84
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