Alternatives In Fixation For Osteoporotic Bone
Typically, screw and plate fixation are the protocol for fixation in osteoporotic bone, but some research has demonstrated the efficacy of more biological type of fixation techniques. Researchers have demonstrated that the holding strength of screws in osteoporotic bone may be decreased by up to 10 times, lending to the utilization of alternative types of fixation and possible augmentation of fixation with bone cement.2
A variety of research regarding the fixation of upper extremity fractures in osteoporotic bone has occurred because this is where the majority of these fractures happen. However, one can apply these principles to the lower extremity as well.
What The Literature Reveals About Plate Fixation And Osteoporotic Bone
Plating is one of the most commonly utilized techniques for fixation of osteoporotic bone. Proposed methods for improved fixation have included long plates, which allow for greater distance between the fracture/osteotomy site and the farthest screw position as well as an improved resistance to rotational loading.
Traditional plating techniques rely on friction as a means of ensuring rigid internal fixation. However, successful fixation only occurs when there is enough friction along the plate, bone and fracture fragments held together in compression.10 The traditional plating technique can resist axial, torsional and bending loads when no fracture gaps exist and the surgeon properly positions the plate.
One can achieve increased resistance to screw pullout and increased torque at the bone plate interface in traditional plating with bicortical screw purchase.11 Screw pullout and available torque are related to the material into which the surgeon inserts them. Systemic diseases associated with bone demineralization or generalized osteopenia present the kind of deficient bone quality in pedal cases that can fail to resist the advancing torque or screw pullout forces one encounters in a typical postoperative period.
Traditional plating techniques create potential risks in foot and ankle surgical cases in which comminution, significant gaps in bone or inherent instability of non-anatomically reduced fractures are common.11 Shortcomings in traditional plating methods lead to small amounts of motion at the plate’s bone-to-screw interface. This motion can loosen fixation. Lost or failed fixation directly leads to nonunion as described in Perren’s “strain theory of bone.”12
Research has demonstrated that using blade plates to provide improved fixation at the plate assists in decreasing the dependence of screw thread purchase on adequate fixation.13 There have been mixed findings regarding whether locking or non-locking plating offers superior fixation in osteoporotic bone.
When Should You Use Locking Plates?
Kim and colleagues theorized that osteoporotic bone does not provide an adequate foundation for traditional plating techniques, thus necessitating the use of locking plate technology.7 The authors went on to evaluate the relationship between bone mineral density and plating styles, determining that there was a strong relationship among achievement of adequate fixation, traditional plating and bone mineral density. The authors found locking plates to be successful independent of the level of bone mineral density.
Zehnder and co-workers, in their comparison of locking plates with four screw angulation fixation methods, found no initial difference in load to failure rates between fixation types.14 However, they did find that with increased loading, the locking plates proved to be superior to the non-locking styles.