Patrick Burns, DPM, FASPS Assistant Professor of Orthopaedic Surgery University of Pittsburgh School of Medicine

Stability v Compression

• No Conflicts

Patrick R. Burns, DPM

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• What is needed for bone healing

• Types of bone healing • Types of stability • Types of fixation

• Fractures v arthrodesis

• Traditional teaching

Compression v stability

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• Primary – Contact

• Secondary – Callus – “Natural”

Bone healing

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• Compression techniques produce friction

• Friction gives rigid stabilization

• Cutting cones are allowed to connect the fragments undisturbed

Primary bone healing

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• Fragments are held “stable” • Micromotion available • “natural” healing, signals are

produced in response to injury

• Need to control shear strains – Opposing forces parallel to

surface

Secondary bone healing

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• Absolute – No movement at site – Interfragmentary compression – Friction gives rigidity – Direct bone contact/healing – No callus formed

• Relative – Controlled movement at site – “splinting” of site – Indirect bone healing – Callus is formed

Stability

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• Compression techiques – Screw, by technique – Screw, by design – Compression plate – Tension band

• No gap, so how do you know it is healing?

• Screws across site reduce surface area to heal

Absolute stability

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• 40 sawbone models • 6.5, 7.0 screws • 2 v 3 screws • 9% v 16% surface area

– Not significant

• What is required for fusion? – Surface area – Percentage

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• Splint/bridge techniques – IM rod – External fixator – Internal fixator

• Varying degrees of stability

• Motion allows for biologic signals

• Callus forms quickly

• See gap fill, watch hardware

Relative stability

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• Lord J Charnley – JBJS 1951 – “Compression eliminates all

shearing strains”

• AO – 1958 – Atraumatic technique – Anatomic reduction – Stable internal fixation – Early active pain free

mobilization

• In reality was original AO that stable?

Traditional teaching

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• Plates changed • Screws changed

• Application of techniques

changed

Compression increased over the years…too much?

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• Rabbit tibia • Varying compression at the

osteotomy site • Permitted some degrees of

motion

How do we know compression is not necessary?

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• Compression itself was not a beneficial factor

• In excess, compression acted adversely – Slower callus – Less mature callus – Resorption of bone

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• Tibial osteotomy in sheep • Compression plate v dynamic

application • 6x more callus with dynamic • 2x as strong with dynamic

• Overly rigid suppresses callus

formation and biologic bone healing

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• Creating a more biologically friendly construct

• Non-union up to 19% with locked plates

• Far cortical locking better? • Reduces stiffness, maintains

strength

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• JFAS 2008 • 1 screw, N=16 • 1 screw and plate, N=18

• No statistical difference

– Union – Time to heal – Pt outcomes

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• 195 first ray surgeries – 85 1st MTP – 110 1st MCJ

• Twin-plate fixation • No interfrag • 97% bone healing, no

hardware failure

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P. Dayton et al. / The Journal of Foot & Ankle Surgery 58 (2019) 427−433

UPMC

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• Achieved in different ways

• Type of fixation – Screw – Plate type

• Way fixation is applied – Buttress – Compressive

• Fixation material – Titanium v stainless

Require “rigid” for healing

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• FAI 2006 • Xray and CT 6, 12 months • STJ, triples • Continued fusion, bone

activity still increasing at 1 yr

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• Bone healing should be revisited

• Understand fixation types available and their potential applications

• Remember stability is paramount, the amount of compression is still up for debate

Final thoughts

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