Dynamic Stabilization with Active Locking Plates Delivers Faster, Stronger, and More Symmetric Fracture-Healing

Abstract

Background: Axial dynamization of fractures can promote healing, and overly stiff fixation can suppress healing. A novel technology, termed active plating, provides controlled axial dynamization by the elastic suspension of locking holes within the plate. This prospective, controlled animal study evaluated the effect of active plates on fracture-healing in an established ovine osteotomy model. We hypothesized that symmetric axial dynamization with active plates stimulates circumferential callus and delivers faster and stronger healing relative to standard locking plates. Methods: Twelve sheep were randomly assigned to receive a standard locking plate or an active locking plate for stabilization of a 3-mm tibial osteotomy gap. The only difference between plates was that locking holes of active plates were elastically suspended, allowing up to 1.5 mm of axial motion at the fracture. Fracture-healing was analyzed weekly on radiographs. After sacrifice at nine weeks postoperatively, callus volume and distribution were assessed by computed tomography. Finally, to determine their strength, healed tibiae and contralateral tibiae were tested in torsion until failure. Results: At each follow-up, the active locking plate group had more callus (p < 0.001) than the standard locking plate group. At postoperative week 6, all active locking plate group specimens had bridging callus at the three visible cortices. In standard locking plate group specimens, only 50% of these cortices had bridged. Computed tomography demonstrated that all active locking plate group specimens and one of the six standard locking plate group specimens had developed circumferential callus. Torsion tests after plate removal demonstrated that active locking plate group specimens recovered 81% of their native strength and were 399% stronger than standard locking plate group specimens (p < 0.001), which had recovered only 17% of their native strength. All active locking plate group specimens failed by spiral fracture outside the callus zone, but standard locking plate group specimens fractured through the osteotomy gap. Conclusions: Symmetric axial dynamization with active locking plates stimulates circumferential callus and yields faster and stronger healing than standard locking plates. Clinical Relevance: The stimulatory effect of controlled motion on fracture-healing by active locking plates has the potential to reduce healing complications and to shorten the time to return to function.

A Concert between Biology and Biomechanics: The Influence of the Mechanical Environment on Bone Healing

“…However, in some circumstances the constructs are considered too rigid and fracture healing can be delayed, resulting in implant failure and subsequent non-union (Figure 4; Gautier and Sommer, 2003; Lujan et al, 2010). Further research to address this issue has led to the development of modified designs that limit the stiffness of the implant-fracture construct, including far-cortical locking screws (Bottlang et al, 2009) and the recently proposed “active” plate (Bottlang et al, 2016). It is far too soon to know whether either of these developments will demonstrate sufficient advantages clinically, or will instead lead to further modifications to internal fixation.…”

Nonunion fracture healing: Evaluation of effectiveness of demineralized bone matrix and mesenchymal stem cells in a novel sheep bone nonunion model

“…Indeed, in all treated bone where spiral fracture occurred, the fracture passed through, or more likely originated from, a “cortical defect” (screw hole). Otherwise, the torsion will have determine an horizontal fracture through the callus, as already described in previous reports (Bottlang et al, ; Lu et al, ). Therefore, it is interesting to note that the spiral fracture occurred only in one case in the DBM + MSC group against the two cases observed in the DBM group, where a hybrid fracture took place in other two cases.…”

“…Indeed, the spiral fracture, which occurred in all intact tibiae tested in the present study, is typical of an intact bone segment subjected to torsion (Johner, Stäubli, Gunst, & Cordey, ; Paavolainen, ; Robinson, McLauchlan, McLean, & Court‐Brown, ; Strömberg & Dalén, ). In a treated bone, this mode of failure can occur only in presence of a hard callus: The fracture can propagate along the shaft only when the mechanical competence of the callus is at least comparable with the one of bone stumps (Bottlang et al, ), taking into account the stress concentration effect of screw holes (Brooks, Burstein, & Frankel, ). Indeed, in all treated bone where spiral fracture occurred, the fracture passed through, or more likely originated from, a “cortical defect” (screw hole).…”

Virtual Mechanical Testing from Low-Dose CT Scans Predicts Tibial Fracture Time to Union and Outperforms Subjective Outcomes Scoring

“…18 A virtual torsion test was chosen as the summary measure of mechanical integrity in each model. Torsional stiffness relative to intact paired controls is often used as a summary indicator of healing in preclinical models, [19][20][21][22][23] because it is direction independent. 24…”