1. DEPARTMENT OF ORTHOPAEDICS GANDHI MEDICAL COLLEGE, BHOPAL Seminar On PRINCIPLES AND TECHNIQUES OF AO Moderator : Dr. J. Shukla Dr. A. Gohiya Presented by : Dr. Radheyshyam

10. Buttress Position Neutral Position Load Position

13. Application of Compression Plate

18. Dynamic compression principle: The holes of the plate are shaped like an inclined and transverse cylinder. Like a ball, the screw head slides down the inclined cylinder. Because the screw head is fixed to the bone via the shaft, it can only move vertically relative to the bone. The horizontal movement of the head, as it impacts the angled side of the hole, results in movement of the bone fragment relative to the plate and leads to compression of the fracture.

20. General principles of internal fixation.

21. The shape of the holes of the dynamic compression plate allows inclination of the screws in a transverse direction of +7° and in a longitudinal direction of 25°.

24. The structure of a limited-contact dynamic compression plate. LC-DCP

25. In the dynamic compression plate (A), the area at the plate holes is less stiff than the area between them. During bending, the plate tends to bend only in the areas of the hole. The limited-contact dynamic compression plate (B) has an even stiffness without the risk of buckling at the screw holes.

28. Bridge Plating : Bridge Plating for comminuted fracture

29. Wave Plating : Wave Plating for non union.

35. Reconstruction plates are thicker than third tubular plates but not quite as thick as dynamic compression plates. Designed with deep notches between the holes, they can be contoured in 3 planes to fit complex surfaces, as around the pelvis and acetabulum. Reconstruction plates are provided in straight and slightly thicker and stiffer precurved lengths. As with tubular plates, they have oval screw holes, allowing potential for limited compression.

37. limited stability. The thin design allows for easy shaping and is primarily used on the lateral malleolus and distal ulna. The oval holes allow for limited fracture compression with eccentric screw placement.

39. The mechanical principle of a locked screw plate. (A) The plate sits slightly of the bone. (B) Tightening of the screw locks the screw head within the plate. The plate is not drawn toward the bone and there is no compression b/w the bone and the plate. The flux is bone/ screw/ plate/ screw/ bone.

40. Maintenance of primary reduction Once the locking screws engage the plate, no further tightening is possible. Therefore, the implant locks the bone segments in their relative positions regardless of degree of reduction. Precontouring the plate minimizes the gap between the plate and the bone, but an exact fit is not necessary for implant stability. This feature is especially advantageous in minimally or less invasive plating techniques because these techniques do not allow exact contouring of the plate to the bone surface. Bridge/Locked Plating Using Locking Screws • Screws lock to the plate, forming a fixed-angle construct. • Bone healing is achieved indirectly by callus formation when using locking screws exclusively.

41. Stability under load By locking the screws to the plate, the axial force is transmitted over the length of the plate. The risk of a secondary loss of the intraoperative reduction is reduced. Blood supply to the bone Locking the screw into the plate does not generate additional compression. Therefore, the periosteum will be protected and the blood supply to the bone preserved.

48. Plate screw density and fracture plate quotient

53. The screw thread is defined by its major or outside and minor or root diameters, pitch, lead, and number of threads. Bottom: Screw head drive types.

54. Common screw.

57. Cutting Edge Flute Margin Axis of drill Cutting lip Drill Bit

59. DIFFERENT AO SCREWS 1.5 mm Cortex Screw 2.0 mm Cortex Screw 2.7 mm Cortex Screw MINI SCREW 4.0 Canceleous Screw -Partially Threaded. -Fully Threaded 3.5 mm Cortical Screw SMALL FRAGMENT SCREW 3.5 Cannulated Screw 4.0 mm Cannulated Screw 6.5 Cannulated Screw CANNULATED SCREW SYSTEM Malleolar Screw 4.5 6.5 mm Cancellous Screw 4.5 mm Cortex Screw LARGE STANDARD SCREWS.

60. THE LAG SCREW A lag screw is the most effective way to achieve compression between two bone fragments; it pulls the fragments together producing pressure across the fracture line. It achieves this by providing purchase on the distal fragment while being able to turn freely in the proximal. If the screw threads engage both cortices, the fragments remain apart like two nuts on the same bolt.

61. Top: Biomechanics of cannulated and noncannulated screws. Bottom: Ideally, lag screw fixation produces maximum interfragmentary compression when the screw is placed perpendicular to the fracture line.

62. Optimal inclination of the screw in relation to a simple fracture plane.

63. T-lag screw.

65. 4.5mm 3.2mm 4.5mm 1.75mm 4.5 mm 3mm 4.5mm cortical 4.5mm 3.2mm 1.75mm 3.1mm 4.5mm 4.5mm cancellous screw 6.5mm 4.5mm 3.2mm 2.7mm 6.5mm 3.5mm 6.5mm cancellous screw 7mm 4.5mm 2.75mm 7mm 4.5mm 7mm Cancellous Screw Large Standard Screws Tap diameter Drill bit for thread hole Drill bit for gliding hole Pitch Thread diameter Core diameter Screw

66. 1.5mm 1.1mm 1.5mm 0.5mm 1.5mm 1mm 1.5mm Cortex Screw 2mm 1.5mm 2mm 0.6mm 2mm 1.3mm 2mm Cortex Screw 2.7mm 2mm 2.7mm 1mm 2.7mm 1.9mm 2.7mm Cortex Screw Mini Fragment Screws 3.5mm 2.5mm 3.5mm 1.25mm 3.5mm 2.4mm 3.5mm Cortex Screw 4mm 2.5mm 1.75mm 4mm 1.9mm 4mm Cancellous screw 3.5mm 2.7mm 1.25mm 3.5mm 2.5mm 3.5mm cancellous screw Small Fragment Screws

71. TENSION BAND PRINCIPLE Tension-band principle.

72. Tension-band principle at the femur.

80. Blk screws. Working Length

91. Thanks