MINIMALLY INVASIVE PLATE OSTEOSYNTHESIS Overview Introduction - - PowerPoint PPT Presentation

MINIMALLY INVASIVE PLATE OSTEOSYNTHESIS

Kirsten Deruddere – Residents Forum 2014 Advanced Vetcare - Melbourne

Overview

⦿ Introduction ⦿ Bone healing principles and

interfragmentory strain theory

⦿ ORIF vs biological osteosynthesis ⦿ Changes in plate design ⦿ MIPO principles ⦿ Important articles for exams

Plating History

⦿ Plating has been used since the 1800’s. ⦿ Common complications included

infection, malunion or nonunion or poor return to function.

⦿ Steam sterilisation (1886) and xrays

(1895)

⦿ 1949 – link between stability and type of

bone healing was made

Bone Healing Principles

Direct Bone Healing Summary

• ⦿

Simple fractures and

• steotomies, articular

fractures

⦿

Accurate anatomic reduction

⦿

Open reduction with direct visualisation of fragments

⦿

Little/no callus forms

⦿

Absolute stability using: plates and screws, lag screws, pins, etc

⦿

Healing takes 2-3 months in young animals, up to 12 months in adults

Absolute stability

Indirect Bone Healing Summary

⦿ Comminuted fractures,

non-articular fractures

⦿ No accurate anatomic

reduction

⦿ Ideally the fracture is not

exposed

⦿ A large callus forms ⦿ Relative stability is

achieved using: cast, bridging plates, IM pins, ESF, etc

⦿ Healing takes 4-6 weeks

in young animals, or up to 12 weeks in adults Relative stability

Absolute (Rigid) Relative (Flexible)

Spectrum of Stability

Cast IM Nail Compression Plating/ Lag screw Ex Fix Bridge Plating

Interfragmentory Strain Theory

⦿ Pluripotent cells are responsive to local

deformation within a fracture gap and different tissues can withstand specific levels

• f deformation beyond which they are unable

to survive.

⦿ Granulation tissue (100%)>cartilage

(15%)>Bone (2%)

⦿ Bone resorption occurs at the fracture gap

under conditions of relative stability to increase the gap, decrease strain and encourage deposition of cartilage and fibrous tissue.

The AO Principles

⦿

1962 – AO principles

• (1) restoration of anatomy,
• (2) stable fracture fixation,
• (3) preservation of blood supply,
• (4) early mobilization of the limb and patient.
• ⦿

New AO Principles

• Fracture reduction and fixation to restore anatomical relationships;
• Fracture fixation providing absolute or relative stability as the “personality”
• f the fracture, the patient, and the injury requires;
• Preservation of the blood supply to soft tissues and bone by gentle

reduction techniques and careful handling;

• Early and safe mobilization and rehabilitation of the injured part and the

patient as a whole.

• ⦿

Gradual change to more biological fixation

• Plate application
• Plate design

Change from ORIF to Biological Fixation

Change from ORIF to biological

• steosynthesis

⦿ Factors contributing to osteomyelitis, non-union and

sequestration (Rozbruch 1998):

• Extensive soft tissue dissection
• Disruption of the fracture haematoma
• Multifocal periosteal necrosis secondary to plate compression
• Iatrogenic trauma associated with interfragmentary implants

such as lag screws and cerclage wires.

• Best predictor of success: longer plates and fewer screws
• Time to union during this study went from 20 weeks to 13

weeks as techniques shifted towards biological

• steosynthesis.
• Nonunion rates dropped from 10% to 4%.
• Success rates increased despite less use of bone grafts.

ORIF to Biological Osteosynthesis

⦿ Biological osteosynthesis consists of less

precise reconstruction and less rigid fixation which reduces iatrogenic trauma to the fracture site and encourages early formation

• f callus with rapid secondary bone healing.

⦿ Generally this requires the use of locked

internal fixators which have minimal implant- to-bone contact, long-span bridging and fewer screws for fixation.

• Ie. Interlocking nails, bridge plating and internal

fixator-like devices (locking plates).

Principles of Biological Osteosynthesis

⦿ Indirect reduction ⦿ Flexible fixation ⦿ Avoidance of biological damage ⦿ Less reliance on the use of bone grafts

• ⦿ The aim is to produce the best biological

conditions for healing rather than absolute stability of fixation.

⦿ early solid union in both humans and animals

• Biological internal fixation is only applicable to living

bone

Changes in Plate Design

Limited Contact Plates

⦿ Early temporary porosity

• A correlation was seen between porosity and

the width of contact of the implant assumed due to damage to the periosteal blood supply

⦿ Limited contact plate

• Minimise bone contact and impingement on

periosteal blood supply minimises soft tissue necrosis

Locking plates (Internal Fixators)

⦿

Screw heads lock into the plate axial and angular stability.

⦿

Stability is not dependent on the frictional forces generated by lagging the plate to the bone as for conventional plates. Advantages:

⦿

Threads are unlikely to strip.

⦿

The plate does not need accurate contouring and sits

• ff the bone preserving the extraosseous blood supply.

⦿

Increased strength against pull-out cf DCP

⦿

Monocortical screws can be used because the locked head acts as a second cortex.

⦿

Some locking screws have a thicker core with increased bending stiffness.

Locking Plates

⦿ Anatomic reduction is not necessary ⦿ Iatrogenic trauma to the fracture site is

minimised

⦿ Ideal for bridging osteosynthesis,

comminuted fractures or fractures with large amounts of bone loss.

⦿ Achieves relative stability and secondary

bone healing.

• ⦿ Locking plates are ideal for MIPO!

Minimally Invasive Plate Osteosynthesis

What is MIPO?

Guiot 2011 VS

Minimally Invasive Plate Osteosynthesis

• 1. Use of indirect, closed reduction

techniques;

• 2. Epiperiosteal plate insertion through

small incisions remote to the unexposed fracture site; and

• 3. Minimal reliance on secondary implants

and bone grafts.

Advantages of MIPO (1)

⦿ Reduced operative time ⦿ Decreased risk of infection

• Shorter surgery time, limited soft tissue trauma,

less chance of contamination.

⦿ Increased callus formation ⦿ Preservation of periosteal blood supply

○ Farouk Arch Orthop Trauma Surg 1998, J Orthop

Trauma 1999, and Borrelli J Orthop Trauma 2002 showed this in humans.

○ Garfolo VS 2011 – showed this in radii in dog

cadavers.

Advantages of MIPO (2)

⦿ Faster healing than ORIF, less care than

ESF

• Baumgaertel Injury 1998 – sheep
• Johnson JAVMA 1998 – 35 dogs

⦿ Reduced post-op pain ⦿ More cosmetic closure

Disadvantages of MIPO

⦿ Technically challenging ⦿ Less suitable for simple and intra-

articular fractures

⦿ Access to intra-op fluoro is

recommended

⦿ Fluoroscopy greatly increases radiation

exposure to both patient and surgeon

Case Selection

Indications:

⦿

Comminuted diaphyseal or metaphyseal fractures

⦿

Excellent for radial and tibial fractures (Schmokel JSAP 2007)

• Less applicable:

⦿

Simple transverse fractures

⦿

Femoral and humeral fractures are more challenging to achieve alignment

⦿

Metaphyseal and epiphyseal fractures – commonly used in humans with special plates

• Contraindications:

⦿

Articular fractures

⦿

If anatomic reduction is required fluoro/arthroscopy should be used

⦿

If major neurovascular bundles overly the approach

⦿

MIPO should not be used if bone is necrotic.

Indirect Fracture Reduction

⦿ The aim of the reduction is to restore

length and alignment so that the joints proximal and distal to the fracture are in the correct orientation.

⦿ Vascularised fragments will be

incorporated into the fracture callus.

⦿ Indirect reduction – the fracture is not

exposed

Reduction – Hanging limb technique

Reduction Forceps

Circular/unilateral ESF

IM Pin

Pre-contoured plate/push-pull

Fracture Distractor

Traction Tables

Approach

⦿

Minimise trauma to nerves/vessels

⦿

One distal incision and one proximal, create an epiperiosteal tunnel and then stab incisions as needed

⦿

Optimal number of screws for MIPO in dogs/cats has not been determined

⦿

Human guidelines (Gautier and Sommer)

• Span large segments of bone at least 3X the length of the

fractured segment

• Screw-to-hole ratio to less than 0.5
• Leave at least 2-3 screw holes empty over the bone defect.
• Construct stiffness can be increased by increasing plate

size, increasing the number of screws or adding an IM pin.

Articles to Read

• Perren J Bone Jt Surg 2002 – Evolution of internal

fixation, interesting read and summary of conventional plating, locking internal fixators, reasons for changes in plate designs, ORIF vs MIPO, etc.

• Garfolo VS 2011 – MIPO disrupts less periosteal

vasculature of the canine radius than open plating.

• Hudson VCOT 2009 – Great review article on MIPO.
• Rovesti VCOT 2006 – First article using intraoperative

skeletal traction in dogs with special tables.

• Pozzi VCOT 2009 – Review of approaches to bones for

MIPO – more for practical use than for exams.

Case Series

• Schmokel JSAP 2007 – Tibial fractures, MIPO is feasible.
• Witsberger VCOT 2010 – Radial plate/ulnar rod MIPO adequate

healing.

• Guiot VS 2011 – Prospective study of 36 dogs and cats with

tibial fractures. Healing times and complications “appeared” shorter than ORIF but this was not specifically tested.

• Pozzi JAVMA 2012 – MIPO radius/ulna fractures healed

faster than ORIF (30 days and 64 days) fractures and with more callus.

• Baroncelli VCOT 2012 – MIPO vs ORIF tibial fractures. No

differences were found between the two techniques. First study comparing the two directly.

• Pozzi VS 2013 – Radius/ulna ORIF vs MIPO also found no

statistical difference in operating time, alignment, gap width or time to union.

• VCNA Sep 2012