Internal bone-fixation screws

Case study C internal bone-fixation screws... 

Early reports of the biomedical use of poly(lactic acid) date back to the 1960s [3, 175]. Since then, PLA has gained widespread application in the medical field, for use in sutures [8], drug delivery devices [15, 17, 24, 59-90], prosthetics, scaffolds, vascular grafts, and bone screws, pins and plates for temporary internal fracture fixation [10-13]. Good mechanical properties and the fact that it de-... 

With external fracture fixation, the bone fragments are held in aUgnment by pins placed through the skin onto the skeleton, structurally supported by external bars. With internal fracture fixation, the bone fragments are held by wires, screws, plates, and/or intramedullary devices. Figure 45.1a,b show radiographs of externally and internally fixed fractures. 

Intramedullary devices (IM nails) are used as internal struts to stabilize long bone fractures. IM nails are also used for fixation of femoral neck or intertrochanteric bone fractures however, this apphcation requires the addition of long screws. A gamut of designs are available, going from solid to cylindrical, with shapes such as cloverleaf, diamond, and C (slotted cylinders). Figure 45.6 shows a variety of... 

PMMA is also injected into vertebral bodies for fixation of fragility fractures of the spine, injected into screw holes to augment internal fixation in osteopenic bone, and injected into stmctural voids following resection of benign tumors to control dead space and support the surrounding bone. In many of these applications antimicrobial powder can be added to the PMMA for drug delivery when local delivery of antimicrobials is needed. 

Biodegradable internal fixation devices such as screws, pins, and plates are already nsed in clinical applications such as orthopaedic surgery. The advantage of using biodegradable fixation devices instead of metallic counterparts in bone orthopaedic snrgery is obvions - the device simply disappears after the bone heals. Loads... 

Fig. 28. X-ray control 2V2 years post-operatively shows re-ossification in the C2 body. The posterior internal fixation using wires can be seen. The screws shows where the bilateral bone grafts have been fixed to the occipital bone...

---