Review Question - QID 217329

The patient sustained a radial shaft fracture which was fixed with a plate and screws in order to achieve absolute stability. Given the post-operative imaging, this surgeon most likely used the principles of compression plating by achieving cortical contact and using plate-assisted compression techniques. This construct leads to primary bone healing which occurs via Haversian remodeling.

It is important for orthopedic surgeons to understand the characteristics of fracture healing. Fracture healing depends on multiple variables including the fracture pattern, type of implant used, and intraoperative reduction/fixation. For example, the standard method of fixation for the radius fracture seen in Figure A would include anatomic reduction and compression plating with primary bone healing and absolute stability. Primary bone healing is accomplished through intramembranous ossification where cutting cones are able to jump the fracture gap in order to promote osteoblast migration through the Haversian system. In contrast, when bridge plating techniques are used or intramedullary nailing is performed, relative stability is accomplished, which leads to secondary bone healing through endochondral ossification.

Marsell et al. reviewed the biology of fracture healing, noting that bones heal through either direct, intramembranous, or indirect, endochondral pathways. While indirect healing is more common, direct healing allows the bone to regenerate Haversian systems without intermediary steps. In cases of indirect healing, an inflammatory response leads to a pathway where soft callous formation is eventually converted to a hard callous and calcified in to bone.

Sathyendra et al. review the basics of bone healing, noting that it can be influenced by host and environmental factors. They discuss the pathways involved in bony healing as well as risk factors affecting the success of healing, including NSAID use and smoking. Ultimately, they provide a summary of each type of bony healing and examples of how these are achieved.

Figure A demonstrates an AP forearm radiograph of a right radial shaft fracture. Figure B demonstrates this radial shaft fracture status post open reduction and internal fixation.

Incorrect Answers:
Answer 1: Secondary bone healing relies on endochondral ossification in which cartilaginous callous is converted to bone.
Answer 2: Fracture site strain should be <2% to achieve primary bone healing through an absolute stability construct.
Answer 3: Primary bone healing is achieved through intramembranous ossification, not endochondral ossification.
Answer 4: In more comminuted fracture patterns or those with significant bone loss, primary bone healing is not easily achieved as fracture apposition and contact is required.