Tipping the Balance: Manipulating the mechanical environment by reverse dynamization can accelerate bone healing

Reverse Dynamization Accelerates Regenerate Bone Formation and Remodeling in a Goat Distraction Osteogenesis Model

UPDATE

This article was updated on December 20, 2023, because of previous errors, which were discovered after the preliminary version of the article was posted online. Figure 4 has been replaced with a figure that presents different p values. Also, on page 1943, the text that had read: "Quantitative microCT confirmed that the total volume of the regenerate in the RD group was much smaller compared with the SF (p = 0.06) and DF (p = 0.007) groups, although it was significantly smaller only compared with the DF group (Fig. 4-A). The total volume of the intact bone (contralateral tibia) was significantly smaller in the RD group compared with the other groups, but the RD group had values closest to those for the intact tibia. Similarly, the RD group had less bone volume compared with the SF and DF groups, and this value was significantly different from the DF group (p = 0.034; Fig. 4-B). Of the 3 groups, the RD group had vBMD that was the closest to that of intact bone. It also had significantly higher vBMD compared with the SF and DF groups (p < 0.0001 for both; Fig. 4-C).The results of torsional testing (Fig. 4-D) confirmed that the regenerate bone formed under conditions of RD was significantly stronger than that formed under SF or DF (p < 0.001 versus SF group, and p = 0.0493 versus DF group)."now reads: "Quantitative microCT confirmed that the total volume of the regenerate in the RD group was significantly smaller compared with the SF and DF groups (p < 0.01 for both groups; Fig. 4-A). The total volume of the intact bone (contralateral tibia) was significantly smaller compared with the SF and DF groups (p < 0.0001 for both). The RD group had values closest to those for the intact tibia, and this difference was not significant (Fig. 4-A). Similarly, the RD group had less bone volume compared with the SF and DF groups, and this value was significantly different from the DF group (p < 0.01; Fig. 4-B). Of the 3 groups, the RD group had vBMD that was the closest to that of intact bone, but the intact bone was significantly different compared with all of the other groups (p < 0.0001 for all groups). The RD group had significantly higher vBMD compared with the SF and DF groups (p = 0.042 and p = 0.046, respectively; Fig. 4-C).The results of torsional testing (Fig. 4-D) confirmed that the regenerate bone formed under conditions of RD was significantly stronger than that formed under SF or DF (p < 0.0001 versus SF group, and p = 0.0493 versus DF group). The intact group was significantly different compared with the SF group (p < 0.0001)."

Reverse Dynamization Accelerates Bone-Healing in a Large-Animal Osteotomy Model

BACKGROUND

Reverse dynamization is a mechanical manipulation regimen designed to accelerate bone-healing and remodeling. It is based on the hypothesis that a fracture that is initially stabilized less rigidly allows micromotion to encourage initial cartilaginous callus formation. Once substantial callus has formed, the stabilization should then be converted to a rigid configuration to prevent the disruption of neovascularization. The aim of the present study was to investigate whether bone-healing can be accelerated using a regimen of reverse dynamization in a large-animal osteotomy model.

METHODS

Transverse 2-mm tibial osteotomies were created in 18 goats, stabilized using circular external fixation, and divided into groups of 6 goats each: static fixation (rigid fixation), dynamic fixation (continuous micromotion using dynamizers), and reverse dynamization (initial micromotion using dynamizers followed by rigid fixation at 3 weeks postoperatively). Healing was assessed with the use of radiographs, micro-computed tomography, and mechanical testing.

RESULTS

Radiographic evaluation showed earlier and more robust callus formation in the dynamic fixation and reverse dynamization groups compared with the static fixation group. After 8 weeks of treatment, the reverse dynamization group had reduced callus size, less bone volume, higher bone mineral density, and no evidence of radiolucent lines compared with the static fixation and dynamic fixation groups. This appearance is characteristic of advanced remodeling, returning closest to the values of intact bone. Moreover, the tibiae in the reverse dynamization group were significantly stronger in torsion compared with those in the static fixation and dynamic fixation groups.

CONCLUSIONS

These findings confirmed that tibial osteotomies under reverse dynamization healed faster, healed objectively better, and were considerably stronger, all suggesting an accelerated healing and remodeling process.

CLINICAL RELEVANCE

This study demonstrates that the concept of reverse dynamization challenges the current understanding regarding the optimal fixation stability necessary to maximize the regenerative capacity of bone-healing. When reverse dynamization is employed in the clinical setting, it may be able to improve the treatment of fractures by reducing the time to union and potentially lowering the risk of delayed union and nonunion.