Principles of locking compression plates

Absolute and relative stability principles, locking compression plate principles

1. Absolute and relative stability and locking plate principles Presenter: DR SOUVIK PAUL

2. Goal of this seminar AO Principles( Martin Allgöwer, Robert Schneider, and Hans Willenegger) Elaboration of absolute and relative stability Discuss about locking compression plates 2

3. AO Principles 1. # reduction and fixation to restore anatomical relationships 2. Stability by fixation or splintage , as personality of fracture and injury requires. 3. Preservation of blood supply to soft tissues and bone by careful handling and gentle reduction techniques. 4. Early and safe mobilization of the part and patient. 3

4. “ Surfaces of the fracture do not displace under functional load” No micromotion R eduction of strain to a level below critical level primary healing without callus compressive preload and friction Rigid fixation , perfect alignment Absolute stability

5. Cutting cone theory

6. Relative stability S ome motion secondary bone healing by callus formation Better in multifragmentary fractures More fragments less strain between fragments less rigid construct requirement “Stress distribution”

7. Biomechanics of callus formation Post op interfragmentary mobility:- amount of external loading stiffness of the splints stiffness of the tissues bridging the fracture. 7

8. Perren's strain theory ε=d/G   where  ε -the inter-fragmentary strain,  d -fracture ends displacement, &  G – gap between ends

9. Methods of absolute stability Compression by Lag Screw:> 2500N

10. Dynamic compression by Tension band

11. Methods of relative stability Bridging plate

12. intramedullary nailing

13. External fixation

14. Plate function Neutralization[Protection] plate Compression plate Tension band plate Buttress plate Bridge plate 14

15. Neutralization Plates Neutralizes/protects lag screws from shear, bending, and torsional forces across fx “Protection Plate"

16. Tension Band Plates Plate counteracts natural bending moment seen wih physiologic loading of bone tension side converts bending force to compression

17. Buttress / Antiglide Plates Resist shear forces Used in metaphyseal areas Plate must match contour Buttress Plate intra- articular fractures Antiglide Plate diaphyseal fractures

18. Bridge Plates Goal: Maintain length, rotation, & axial alignment Avoids soft tissue disruption

19. DCP First introduced in 1969 by Danis Revolutionary concept of compression plating Featured a new hole designed for axial compression Compression depend on friction of plate over bone

20. allow 1mm compression Additional compression with 1 more eccentric screw before locking first screw Compression of several fragments individually in comminuted fractures Oval shape allows 25 deg inclination in longitudinal & 7deg in transverse plane

21. Problems with DCP Unstable fixation leads to fatigue & failure Strict adherence to principles of compression Compromised blood supply “ Refractures ” after plate removal

22. Locking compression plate (LCP) dynamic compression unit conical and threaded unit

23. Mechanics/biomechanics of plate/screw fixation Plate fixation with conventional screws Screws in tension Plate/bone friction Compression at fracture site Disturbed blood supply Plate fixation with locking head screws (LHS) Screws in shear Noncontact plate No compression of fracture Preserved blood supply

24. Functions of LHS Always in combination with a plate Never as lag screw Never cross an unreduced fracture Fixation screw Fix the plate to the bone Position screw Keeps two fragments in correct relative anatomical position

25. Features and advantages of LHS Axial and angular stability Not preloaded Cannot be over-tightened Higher resistance against bending loads Monocortical insertion is possible  Lag first, lock second No primary/ secondary loss of reduction

26. Features and advantages of locked plates Screw-plate system with angular and axial stability Locked internal fixator/noncontact plate Individual blade plate Anatomically contoured High pull out strength

27. Biological advantages Reduced compression of the periosteum Protects blood supply to the bone,less infection Callus formation/bone healing under the plate bone after plating with a DCP bone after plating with a LCP

28. Technical/mechanical advantages Angular and axial stability No need for exact preshaping Good for osteoporotic bone — bicortical LHS Optimal predefined screw placement No need for drilling, measuring, or tapping MIPO is easier

29. Splinting with locked plates—prerequisites Indirect, closed, no precise reduction Long plate Fixation with LHS only on main fragments No screws in fracture zone Prebending not necessary Elastic fixation

30. Drawback of fixation with LHS Screw insertion is only possible in a 90° angle Possible loss of the feel for the quality of the bone during screw insertion and tightening Screw jamming and difficult implant removal

31. Splinting with locked plates—shortcomings and disadvantages Stability depends on rigidity of construct Plate takes over the entire load MIPO is a demanding/difficult technique

32. Combination of compression and splinting with one plate A combination of both methods is only possible when two different fractures occur in same bone. Indications Segmental fractures Articular fracture with additional metaphyseal / diaphyseal fracture

33. LISS-Less Invasive Stabilization System

34. LISS

35. conclusion Two different methods and principles: compression —absolute stability splinting —relative stability no mixture of principles/methods in same fracture

36. Compression plating after anatomical reduction in articular and simple fractures. Splinting/bridge plating in multifragmentary Good for Osteoporotic , Periprosthetic #