Augmented Fixation for Fractures of the Appendicular Skeleton

Experimental magnesium phosphate cement paste increases torque of trochanteric fixation nail advanced™ blades in human femoral heads

BACKGROUND

The use of polymethylmethacrylate cement for in-situ implant augmentation has considerable disadvantages: it is potentially cytotoxic, exothermic and non-degradable. Therefore, the primary aim of this study was to develop a magnesium phosphate cement which meets the requirements for in-situ implant augmentation as an alternative. Secondly, this experimental cement was compared to commercial bone cements in a biomechanical test set-up using augmented femoral head blades.

METHODS

A total of 40 human femoral heads were obtained from patients who underwent total hip arthroplasty. After bone mineral density was quantified, specimens were assigned to four treatment groups. A blade of the Trochanteric Fixation Nail Advanced™ was inserted into each specimen and augmented with either Traumacem™ V+, Paste-CPC, the experimental magnesium phosphate cement or no cement. A rotational load-to-failure-test (0° to 90°) was performed.

FINDINGS

A conventional two-component magnesium phosphate cement failed in-situ implant augmentation consistently due to filter pressing. Only a glycerol-based magnesium phosphate paste was suitable for the augmentation of femoral head blades. While the blades augmented with Traumacem™ V+ yielded the highest maximum torque overall (22.1 Nm), the blades augmented with Paste-CPC and the magnesium phosphate paste also showed higher maximum torque values (15.8 and 12.8 Nm) than the control group (10.8 Nm).

INTERPRETATION

This study shows for the first time the development of a degradable magnesium phosphate cement paste which fulfills the requirements for in-situ implant augmentation. Simultaneously, a 48% increase in stability is demonstrated for a scenario where implant anchorage is difficult in osteoporotic bone.

Degradation and Bone-Contact Biocompatibility of Two Drillable Magnesium Phosphate Bone Cements in an In Vivo Rabbit Bone Defect Model

The use of bone-cement-enforced osteosynthesis is a growing topic in trauma surgery. In this context, drillability is a desirable feature for cements that can improve fracture stability, which most of the available cement systems lack. Therefore, in this study, we evaluated a resorbable and drillable magnesium-phosphate (MgP)-based cement paste considering degradation behavior and biocompatibility in vivo. Two different magnesium-phosphate-based cement (MPC) pastes with different amounts of phytic acid (IP 6) as setting retarder (MPC 22.5 and MPC 25) were implanted in an orthotopic defect model of the lateral femoral condyle of New Zealand white rabbits for 6 weeks. After explantation, their resorption behavior and material characteristics were evaluated by means of X-ray diffraction (XRD), porosimetry measurement, histological staining, peripheral quantitative computed tomography (pQCT), cone-beam computed tomography (CBCT) and biomechanical load-to-failure tests. Both cement pastes displayed comparable results in mechanical strength and resorption kinetics. Bone-contact biocompatibility was excellent without any signs of inflammation. Initial resorption and bone remodeling could be observed. MPC pastes with IP 6 as setting retardant have the potential to be a valuable alternative in distinct fracture patterns. Drillability, promising resorption potential and high mechanical strength confirm their suitability for use in clinical routine.

Is the reconstruction of medial support important for revision following failed treatment of femoral trochanteric fractures? a retrospective comparative study

BACKGROUND

Hip-preserving revision in patients with failed treatment of femoral trochanteric fracture is still a major challenge. Whether the medial support reconstruction could benefit the patients and improve the success rate of hip-preserving revision is still controversial. Hence, the purpose of this study was to evaluate the clinical significance and prognosis of medial support reconstruction during the hip-preserving revision of failed femoral trochanteric fracture treatment.

METHODS

Patients with failed femoral trochanteric fractures treatments addressed by hip-preserving revision at our hospital from January 2014 to December 2020 were analyzed retrospectively. 31 patients were included and divided into a medial support group (n = 16) and a non-medial support group (n = 15). The fracture healing rate was the primary measurement. In addition, the differences in Oxford Hip Score (OHS), quality of life, surgical trauma, and complications were also evaluated.

RESULTS

The fracture healing rate (100%, 16/16 vs. 66.67%, 10/15), the OHS (42.06 ± 4.12 vs. 30.93 ± 11.56, M ± SD), and the mental component score of the 12-item Short-Form Survey (SF-12) (54.48 ± 5.38 vs. 47.90 ± 3.47, M ± SD), were significantly better and the incidence of complications [0(0/16) vs. 40%(6/15)] was significantly lower in the medial support group than the non-medial support group (p < 0.05). No significant differences in the physical component score of the SF-12, surgical trauma and reduction in collodiaphyseal angle of affected femur were observed between groups.

CONCLUSIONS

The reconstruction of medial support seems important for revision following failed treatment of femoral trochanteric fractures. Due to the medial augmentation and improvement of the mechanical stability for proximal femur, the patients might benefit from fracture healing prognosis and functional.

Experimental Drillable Magnesium Phosphate Cement Is a Promising Alternative to Conventional Bone Cements

Clinically used mineral bone cements lack high strength values, absorbability and drillability. Therefore, magnesium phosphate cements have recently received increasing attention as they unify a high mechanical performance with presumed degradation in vivo. To obtain a drillable cement formulation, farringtonite (Mg₃(PO₄)₂) and magnesium oxide (MgO) were modified with the setting retardant phytic acid (C₆H₁₈O₂₄P₆). In a pre-testing series, 13 different compositions of magnesium phosphate cements were analyzed concentrating on the clinical demands for application. Of these 13 composites, two cement formulations with different phytic acid content (22.5 wt% and 25 wt%) were identified to meet clinical demands. Both formulations were evaluated in terms of setting time, injectability, compressive strength, screw pullout tests and biomechanical tests in a clinically relevant fracture model. The cements were used as bone filler of a metaphyseal bone defect alone, and in combination with screws drilled through the cement. Both formulations achieved a setting time of 5 min 30 s and an injectability of 100%. Compressive strength was shown to be ~12–13 MPa and the overall displacement of the reduced fracture was <2 mm with and without screws. Maximum load until reduced fracture failure was ~2600 N for the cements only and ~3800 N for the combination with screws. Two new compositions of magnesium phosphate cements revealed high strength in clinically relevant biomechanical test set-ups and add clinically desired characteristics to its strength such as injectability and drillability.