Application of Cal-Cemex bone substitute in fractures of the proximal meta-epiphysis of the tibia

Fractures of the proximal tibial metaepiphysis are relatively complex multicomponent injuries involving damage to the articular surface and formation of a bone defect. The incidence of complications after tibial plateau fractures ranges from 2 to 23.6%, while the rate of required repeat revision surgery reaches up to 20%. The main goals of surgical treatment are restoration of the mechanical and anatomical axes of the tibia, restoration of range of motion, and restoration of knee joint stability. Reduction and osteosynthesis using plates and screws is the preferred treatment method for fractures at this location. However, the main problem in such situations is replacement of bone defects. Numerous materials are used for bone defect reconstruction, including autologous and allogeneic bone grafts, bone cements, and many different bone substitutes. Calcium phosphate and calcium sulfate are also widely used because of their good biocompatibility and osteointegration, although they have limited resistance to axial loading. Polymethyl methacrylate (PMMA) has greater mechanical strength and a higher elastic modulus but does not have good biocompatibility with bone tissue.

The Italian company Tecres S.p.A. (Verona, Italy) developed a new Cal-Cemex bone substitute with a hybrid formulation consisting of β-tricalcium phosphate (β-TCP) and PMMA. The efficacy of the clinical use of this material was evaluated in the article “Efficacy of Cal-Cemex as bone substitute for tibial plateau fractures.” The study was published in the Journal of Orthopaedic Surgery and Research in 2023. A group of authors from three European centers—Carlo Poma Hospital (Mantua, Italy), F. Miulli Regional General Hospital (Bari, Italy), and Sytenko Institute (Kharkiv, Ukraine)—conducted a retrospective multicenter study between December 2016 and March 2022. The outcomes of treatment for 45 displaced tibial plateau fractures were evaluated. According to the Schatzker classification of proximal tibial fractures, the group included 13 type II injuries, 24 type III fractures, 3 type V fractures, and 5 type VI injuries. In addition to reduction of the bone fragments and osteosynthesis, all patients underwent filling of bone defects in the tibial metaepiphyseal region with Cal-Cemex. Postoperative follow-up included clinical and radiographic examinations at 6 weeks, 12 weeks, and 1 year after surgery. Computed tomography was performed preoperatively and 1 year after surgery. Full weight-bearing on the limb was permitted during the first 6 weeks after surgery. To evaluate knee and limb function, the authors used three scales: the Rasmussen knee function score, KOOS score, and Hospital for Special Surgery knee rating score (HSS).

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The Cal-Cemex application technique involves mixing two separate sterile components, a powder and a liquid, using the dedicated Shakit device. The resulting homogeneous paste is delivered through the Xtruder device, which consists of a syringe and a cannula connected to a T-shaped handle. After polymerization, the Cal-Cemex paste hardens into a cement-like material that can be drilled or cut without compromising its biomechanical properties.

The mean postoperative follow-up was 42.8 months. Computed tomography performed 1 year after surgery showed good osteointegration without osteolysis, with convincing evidence of bone tissue ingrowth into the Cal-Cemex material. Functional outcomes at 1 year after surgery were as follows: mean Rasmussen score, 24.7; mean KOOS score, 90.7; and mean HSS score, 89.9. The mean time to restoration of full weight-bearing was 34.9 days. No complications were recorded in any patient in the study group. There were also no cases requiring repeat surgery or implant removal for any reason.

As reported in a number of literature sources and confirmed in this publication, Cal-Cemex combines the mechanical strength of PMMA with the biological properties of β-TCP. Its mechanical properties are achieved immediately after polymerization and do not change over time, whereas its biological characteristics only improve over time. β-TCP micropores create a network of interconnected capillaries, while β-TCP macropores promote osteoconduction and progressive bone ingrowth through the interconnected pores. This microporous structure of Cal-Cemex provides interconnection with bone, while macroporosity facilitates osteointegration. Another advantage of Cal-Cemex is its radiopacity, which helps optimize percutaneous delivery of the material under fluoroscopic guidance. Finally, after polymerization, Cal-Cemex can be easily perforated and/or cut without compromising its density or its connection with bone. This is particularly important because it may subsequently allow knee arthroplasty to be performed if required.

Indications for the use of bone substitutes to compensate for bone loss in various pathological conditions in both traumatology and orthopedics continue to expand. Ideally, a bone substitute should have mechanical properties close to those of natural bone, provide complete integration, and undergo resorption. Potentially, it may also serve as a delivery system for factors that stimulate fracture healing or for antibiotics intended to prevent or treat infection. Cal-Cemex (β-TCP+PMMA), a new bone substitute, combines biological properties with good mechanical characteristics. This makes it a highly attractive material, particularly for the treatment of unstable fractures associated with bone loss and/or fractures of the metaepiphyseal regions of long bones in the setting of osteoporosis.

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The results of this Cal-Cemex study, in comparison with other materials, confirm its high safety and efficacy, together with the combination of biological properties and good mechanical characteristics. Cal-Cemex demonstrated biocompatibility, osteoconductivity, and osteointegration, although it is not completely resorbed. After polymerization, the β-TCP component provides the bone substitute with macro- and microporosity, allowing biological fluids to penetrate the material and stimulating bone ingrowth. Importantly, according to the literature, when other bone substitute materials are used, the mean time to initiation of weight-bearing ranges from 6 to 12 weeks. In patients treated with Cal-Cemex in the study group, however, full axial weight-bearing was restored within 6 weeks after surgery.

The authors emphasize the need for further studies with long-term follow-up to confirm the efficacy of Cal-Cemex in injuries involving other anatomical regions. There is a genuine need to continue studying the properties of this material in reconstructive surgical treatment of neoplastic bone processes. The publication also notes the potential to expand the indications for Cal-Cemex in other areas of orthopedics and traumatology.