Alternatives In Fixation For Osteoporotic Bone
The polyaxial system also allows eccentric loading. This allows the foot and ankle surgeon to take advantage of many plating principles. Surgeons may use this system to facilitate conventional compression of a solid, reducible area of a fracture or osteotomy while reserving the opportunity to lock and bridge an area of significant bone grafting or comminution within the same plate.
This “lag and lock” principle involves the combination of compressing the plate to bone while the locking screws are locked to the plate. Foot and ankle surgeons can use this principle in cases in which good bone quality and bicortical screw purchase coexist with diseased or osteoporotic bone. The locking compression plates can maintain both angular stability and interfragmentary compression within one plate.
Polyaxial locking plates allow surgeons to apply the fixed angle concept in more than one axial relationship.22 Previous locking constructs limited the option for screw plate locking to one 90-degree option. The polyaxial concept opens the door for screw placements in upward of a 15-degree divergence in any one direction or plane. The advancement of the polyaxial concept makes it possible to introduce multiple locking screws with an independent axis of orientation. Studies have shown that surgeons can accomplish the polyaxial concept without compromising torque to failure or pullout strengths of the implant.23
What You Should Know About Screws And Other Fixation
Screw type can also affect fixation outcomes in osteoporotic bone. Cannulated screws offer the surgeon the advantage of precise anatomic placement but may possess decreased holding strength in comparison to non-cannulated screws.
Ramaswamy and colleagues examined the holding power of four types of small fragment, cannulated screws in normal versus osteoporotic bone.24 Their study determined that the Barouk screw, which possesses more threads and a greater surface area, demonstrated a greater pullout and push out strength than the other types tested. Interestingly, the authors did find that the average pullout strength decreased by 4 to 30 percent in normal and osteoporotic bone after surgeons implanted the screws, removed them and then reinserted them.
Researchers have discussed other methods of fixation in the literature for osteoporotic bone. For example, authors have described intramedullary nailing as a viable alternative for ankle fractures in bone with decreased density. This method offers the additional benefit of a minimal incision with decreased risk of soft tissue infection.2,25 Other authors have described the utilization of a nylon cavity plug in osteoporotic bone for instances in which the tapped thread in cortical bone has become stripped.25
What About Post-Op Considerations?
Postoperative management is another key component when caring for patients with osteoporotic bone. It important to keep in mind that extended periods of immobilization or non-weightbearing may significantly impact long-term joint range of motion as well as negatively impact already depleted bone density values.26 This factor is another reason for judicious application of fixation methods in these patients.
The surgeon should also keep in mind that comorbidities as well as cigarette smoking can be complicating factors and have deleterious effects on the outcomes of these patients.2,5 In a study of complications after ankle fracture in elderly patients, Lynde and co-workers found 18.18 percent and 10.87 percent complication rates in patients with and without comorbidities respectively.16