Fracture fixation using ‘LOCKED’ plates

Ashok S Gavaskar

AO principles course – Vizag 2016

Learning outcomesWill discuss

•The need for locked plates based on mechano-biological characteristics•Advantages of locked plates •Technique of using locked compression plates using clinical case examples•Tips, tricks and shortcomings

Resist physiological loads

Ideal plate-screw-bone construct?

Sufficient stability

Minimal soft tissue dissection &

periosteal imprint

Avoid mechanical & biological failures

What happens in conventional plating?

Screw torque

Co-efficient of friction between plate & bone

OsteoporosisCancellous bone

ComminutionPathological host bone

Leaves a big periosteal footprint

Conventional plate biomechanics

Fracture under compression

LOADSHARING

CONSTRUCT

Applied Load

1

2 3

Bone protects the plate

Fracture comminution

Conventional plate biomechanicsApplied Load

LOADBEARING

CONSTRUCT

When patient loads > co-efficient of friction

of the bone - plate

•Progressive screw loosening• Failure of the plate

Evolution of the locked plate designs

Pc - Fix LISS LCP

Internal fixator DCU + LISS

Locked plate biomechanics

SINGLEBEAM

CONSTRUCT

No motion occurs between individual components of the construct

4 times stronger than load sharing constructs

Gautier E, Perren SM, Cordey J. Effect of plate position relative to

bend- ing direction on the rigidity of a plate osteosynthesis. A

theoretical analy- sis. Injury. 2000;31(suppl 3):C14–C20.

Bone after plating with DCP Bone after plating with LCP

Locked plate – Biological advantages

LHS and the LCP – Basic concepts

POSITION SCREW

FIXATION SCREW

Fixes the plate to the bone

Keeps 2 fragments in position

LHS – provide angular and axial stabilityNever as a stand alone or a lag screw

Locked plate – Advantages

Osteoporosis

LHS cannot be over-tightenedNo secondary loss of reductionImproved resistance to bending

Short segment

Locked plate – Advantages

Axial and angular stabilityNo primary loss of reduction

MIPO

No contouringNo primary loss of reductionFavorable as a load bearing construct

Locked plate – Advantages

LCP – when to use?

Any fracture can be treated with a locked compression plate

Absolute stability

Relative stability

Compression Splinting•Articular fractures•Osteoporosis •Simple diaphyseal fractures (upper limb)

•Multi-fragmentary fractures•Open wedge osteotomy•Periprosthetic fractures

•Segmental fractures•C2 and C3 articular fractures

LCP – Preoperative planningType of stability

•Anatomical reduction•Good host bone – conventional screws•Exact PREBENDING•Inter-fragmentary compressioni) DCUii) Lag screw and neutralisation plate

LHS – in poor bone quality

Absolute stability

Closed radial shaft fracture, 22-A2 (

25-year-old man, fall on arm

Principle: absolute stability Method: interfragmentary compression Technique: conventional plating (ORIF)

Case from Michael Wagner, Wien

LCP – Preoperative planningType of stability

Relative stability

•Indirect reduction•Long plate •No pre-bending•LHS - in main fragments•No screw in # zone•Elastic fixation

Closed, 12 – C3 fracture (humeral shaft)48 years female, Fall from height, NV status - intact

Comminuted diaphyseal #Principle: Relative stability Method: BridgingTechnique: MIPO

Periprosthetic distal femur & proximal tibia #s81 years female, osteoporotic

Principle: Relative stability Method: Locked splintingTechnique: Less invasive

LCP – combination techniqueCombine two ‘principles’ in a single construct -only when two different types of fractures in the same bone

Segmental fracture C2, C3 articular fractures

Open grade IIIA 33 – C3 fracture (distal femur)19 years male, MVA

Articular componentPrinciple: Absolute stability Method: CompressionTechnique: ORIF

Metaphyseal componentPrinciple: Relative stability Method: BridgingTechnique: Less invasive

Locked plate – tips & tricks

Lag first & lock next

Cannot help in reduction

In a locked plate achieve reduction first•Distractor•Percutaneous clamps

In a LCP – correction of axial & fracture malalignments is possible

Locked plate – tips & tricks

Simple fractures(transverse & oblique fractures)

Use in compression mode(Use the DCU)LHS – only in osteoporosis

LCP - Technical pearls in bridging

Pre - dynamizeNon-union generators •Longer plate

•Leave 2 empty screw holes over the fracture gap•Screw ratio: 0.4 – 0.5

•Improves working length•Decreases bending stiffness•Improves axial stiffness

Gap strain < 10%

Gautier E, Sommer C. Guidelines for the clinical application of

the LCP. Injury. 2003;34 Suppl 2:B63-76.

Locked plate – tips & tricks

Interface failure

Uncommon•Perfect insertion (upto 5°)•Torque limiter

Respect the FIXED angle

Locked plate – Tips & tricks

Screws Bone quality Fracture location Working length Comments

Unicortical Normal Diaphysis ADEQUATE (Humerus)

Bicortical Normal & osteopenic

Diaphysis & metaphysis

ADEQUATE Avoid self drilling screws

Unicortical Normal Metaphysis INADEQUATE Short segment epi-metaphyseal #s

Unicortical Osteopenic Diaphysis & metaphysis

INADEQUATE contraindication

J Bone Joint Surg Am. 2007;89:2298-307

Unicortical screwsPullout strength = conventional screws & 70% of LHS

•Bone quality•Rotational forces

To conclude..

Using a LCP will depend on - bone quality - fracture personality - anatomical region - surgeon’s preference

•Compression•Bridging•Combined

Absolute/relative stability

For successful practical application..•Preoperative planning•Biological & mechanical considerations•Never mix principles/methods