Original Research

Use of a Novel Magnesium-Based Resorbable Bone Cement for Augmenting Anchor and Tendon Fixation

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References

Calcium phosphate bone void fillers have been commonly used in orthopedic surgery for several applications, including, but not limited to, a variety of fracture fixation or augmentation procedures.1-8 Continuing research on calcium phosphates has evidenced that the addition of magnesium phosphate to the formulation results in improved reactivity of the bone void filler. An in vitro study demonstrated enhanced attachment and proliferation of MG63 osteoblast-like cells on calcium magnesium phosphate cement (CMPC), in comparison with calcium phosphate cement (CPC), along with increased cellular alkaline phosphatase activity.9 The authors further explored the proliferation rates of MG63 cells by comparing CMPC with CPC and magnesium phosphate cement (MPC), and observed significantly increased proliferation of cells on CMPC. They also compared CMPC and CPC using a rabbit bone void model and observed substantial CMPC resorption with new bone formation at the 3-month time point and further reported that the majority of the defect had filled with new bone at 6 months, whereas CPC resulted in <10% new bone formation after 6 months.10 The authors continued to study the differences between CPC, MPC, and CMPC and identified increased proliferation of bone marrow stromal cells (bMSCs), when the cells were associated with CMPC and MPC, and when compared to that with CPC. The osteogenic differentiation of bMSCs was highest in the CMPC and CPC groups, when compared to that in the MPC group, with no significant difference between the CMPC and CPC groups. The authors also compared these 3 different formulations using a rabbit maxillary sinus floor elevation model, in which CMPC resulted in increased new bone formation and mineralization compared to that with CPC and MPC, which was further enhanced with the addition of bMSCs.11

These studies highlight the importance of having both a magnesium phosphate and a calcium phosphate component for a resorbable cement intended for use as a bone void filler. The rationale behind this strategy is related to the release of magnesium ions from the magnesium phosphate component. Magnesium has been shown to increase the proliferation of bMSCs, improve the attachment and growth of osteoblasts, stimulate the proteins involved in bone regeneration, enhance new bone formation, and boost bone mineralization.12,13

OsteoCrete (Bone Solutions Incorporation) is a novel CMPC composed of magnesium oxide, monopotassium phosphate, monosodium phosphate, hydroxyapatite, and sucrose. OsteoCrete has been demonstrated to significantly increase peak torque-to-failure of stainless-steel cortical bone screw fixation, when compared with screw fixation without augmentation and screw fixation with calcium phosphate augmentation using an in vivo equine model. In the same study, the authors showed that OsteoCrete resulted in an interface toughness that was significantly increased compared to that with no treatment, CPC augmentation, and polymethylmethacrylate (PMMA) augmentation. At 6 months after implantation, woven bone had replaced 69% of the OsteoCrete at the screw interface, compared to 44% of that with CPC.14 An equine study examined the effects of OsteoCrete on bone stability and healing using a metatarsal osteotomy model; the study reported significantly improved radiographic callus formation and a greater amount of new bone formation within the fracture gap when compared to that with CPC augmentation or no augmentation. OsteoCrete also secured the fragment significantly better than the CPC and control groups based on a decreased fracture gap over time.15 Another study using a preclinical anterior cruciate ligament (ACL) reconstruction model reported that OsteoCrete resulted in significantly better new bone formation in the tibial tunnel, a smaller amount of fibrous tissue, more cartilage formation at the tendon-bone interface, and a higher ultimate load-to-failure compared to that with standard ACL reconstruction in the contralateral limb after 6 weeks.16 OsteoCrete and PMMA were evaluated in terms of biomechanical fixation of a stemless humeral prosthesis, with data showing that both groups have higher failure loads, failure displacements, and failure cycles when compared to those with the control, nonaugmented group.17 Another preclinical model evaluated cranial bone flap augmentation with 2 resorbable cements and highlighted faster cement resorption and replacement with bone, along with superior stability within the OsteoCrete group compared to that with CPC.18 In a preclinical bone void study conducted for obtaining US Food and Drug Administration 510(k) clearance, OsteoCrete resulted in 83% greater resorption than that with CPC after 12 weeks and 35% greater resorption at 26 weeks, with 84% of OsteoCrete being resorbed and replaced with woven or lamellar mineralized bone of normal morphology at the 26-week time point (unpublished data provided by Bone Solutions Incorporated [BSI]).

These data indicate that CMPCs such as OsteoCrete appear to have potential benefits for augmenting the healing of bone implants and bone soft tissue. Therefore, the objective of this study was to assess the safety and efficacy of OsteoCrete in applications for the augmentation of anchor and tendon fixation in rotator cuff repair and biceps tenodesis procedures, respectively. Improving healing for these 2 commonly performed procedures would be of great benefit in improving the functional outcomes and mitigating the complications and morbidity.

MATERIALS AND METHODS

IN VITRO STUDY METHODS

Cadaveric humeri (N = 12, six matched pairs) of females (age, 70-75 years) were warmed to 37°C prior to testing. Two 4.75-mm vented anchors (SwiveLock, Arthrex) with FiberTape were implanted into a lateral row position (anterior and posterior anchor positioning) of a double-row rotator cuff repair within the greater tuberosity. One anchor was injected with 1 ml of OsteoCrete–after preparation according to the manufacturer’s instructions–through the cannulation channel after placement, and the other anchor served as the uninjected control for each humerus. For the six matched pairs, the OsteoCrete group and the control group were rotated with respect to anterior vs posterior location within the lateral row position. After 15 minutes of the injection, straight pull-to-failure (12 in/min) was performed. Data were compared between the groups for significant (P < .05) differences using t-tests and Pearson correlation.

Continue to: IN VIVO STUDY METHODS

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