Plate and screw fixation

Plate and screw fixation is a method of internal fixation used in orthopedic surgery. It is most commonly used in open reduction internal fixation (ORIF) surgeries as well as fixation of bone post osteotomy (e.g. high tibial osteotomy or rotational osteotomy). 

When applied to the convex side of an eccentrically loaded bone, plate and screw fixation uses the tension band principle and converts tensile forces to compressive forces. The plate is usually applied to the tensile side of the bone (the convex side). If applied to the compressive side (concave) then there is a higher rate of fatigue and hardware failure. 

The application of plates, in addition to screws, is important as this allows the neutralisation of deforming forces that screw fixation alone may not be able to achieve. Appropriate screw placement/sequence is important as incorrect screw placement may result in loss of reduction due to shear forces or displacement. A minimum of six cortices is required for screw fixation (i.e. three bicortical screws on either side of the fracture) and appropriate plate length are essential for adequate fracture fixation. Plates should be longer when used in larger bones with greater stressors. In cases where there is severe comminution bone grafting may be used - this may be cancellous bone grating or cortical (as in the case of strut grafting). 

Advantages and disadvantages

Advantages

• anatomic reduction

• stability for early function

Disadvantages

• refracture post removal of hardware

• stress protection and osteoporosis beneath the plate

• irritation

Shapes and designs

There are many shapes and designs of plates and these are used in conjunction with cortical and cancellous screws. 

Shapes

• tubular (semi-, one-third-, one-quarter-)

• T- and L-shaped plates

• spoon plates

• arthrodesis plates

Designs

• neutralisation plate: neutralise torsional, shear and bending forces when used in conjunction with interfragmentary screws and are typically used in fracture patterns such as butterfly or wedge-type fractures

• compression plate

  • e.g. dynamic compression plates (DCP), locking compression plates (LCP)

  • create compression across the fracture and counteract torsional, shear and bending forces

  • have specially designed holes allowing self-compression by translating the plate as the screw engages it

  • locking plates consist of locking and non-locking screw holes with variable and fixed angles

• buttress plate: counteract compression and shear forces

• bridge plate: can be used In fractures where there is significant comminution or bony defects making anatomic reduction and stability difficult

Material

• polyether-ether-ketone (PEEK) excellent alternative to titanium alloys in the development of implantable load-bearing medical devices, which require greater strength and biocompatibility

History and etymology

The word osteosynthesis was proposed by A. Lambotte in 1904. Its definition, given in 1908, is current: "Osteosynthesis is the artificial contention of bone fragments from fractures, by means of special devices which act directly on the bones, whether exposed or not, with the aim of firmly fixing them in their original position".