Augmentation of femoral neck fracture fixation with an injectable calcium‐phosphate bone mineral cement

Abstract

The first goal of this study was to determine if augmentation with an injectable, in situ setting, calcium-phosphate cement that is capable of being remodeled and was designed to mimic bone mineral significantly improved the strength and stiffness of fixation in a cadaveric femoral neck fracture model. The second goal was to determine if greater increases in fixation strength were achieved as the bone density of the specimen decreased. Sixteen pairs of fresh cadaveric human femora with a mean age of 70.9 years (SD = 17.2 years) were utilized. The bone density of the femoral neck was measured with dual-energy x-ray absorptiometry. The femoral head was impacted vertically with the femoral shaft fixed in 12 degrees of adduction using a materials testing machine to create a fully displaced fracture. Following fracture, 30% inferior comminution was created in each specimen. One randomly chosen femur from each pair underwent anatomic reduction and fixation with three cannulated cancellous bone screws, 7 mm in diameter, in an inverted triangle configuration. The contralateral femur underwent the same fixation augmented with calcium-phosphate cement. Specimens were preconditioned followed by 1.000 cycles to one body weight (611.6 N) at 0.5 Hz to simulate single-limb stance loading. The stiffness in the first cycle was observed to be significantly greater in cement-augmented specimens compared with unaugmented controls (p < 0.05). After cycling, each specimen was loaded at 10 mm/min until complete displacement of the fracture surface and failure of fixation occurred. Specimens augmented with bone mineral cement failed at a mean of 4,573 N (SD = 1,243 N); this was significantly greater (p < 0.01) than the mean for controls (3,092 N, SD = 1,258 N). The relative improvement in fixation strength (augmented/control x 100%) was not inversely correlated to femoral neck bone density (p = 0.25, R2 = 0.09), was weakly correlated to the volume of cement injected (p = 0.07, R2 = 0.22), and was inversely related to the fixation failure load of the control specimen (p = 0.001, R2 = 0.54). There was a mean relative improvement in fixation strength of 169.6% (SD = 77.5). These findings suggest that calcium-phosphate cement provides initial beneficial augmentation to fixation of femoral neck fractures.

Biomechanical evaluation of a new augmentation method for enhanced screw fixation in osteoporotic proximal femoral fractures

“…Some investigators used injectable calcium phosphate cements. 18,[21][22][23][24][25] These materials, however, have inferior mechanical properties, especially in shear and tension, which occur in the human proximal femur. 19 Another drawback in earlier studies was the cement distribution pattern.…”

“…[12][13][14] The application of different bone cements, mostly based on polymethylmethacrylate (PMMA) or calcium phosphates (CaP), is a promising approach for further reducing implant cut-out. [15][16][17][18][19][20][21][22][23][24][25][26][27] However, no standardized technique has so far been developed that achieves safe and reproducible augmentation. Furthermore, infiltration of the trabecular network with viscous bone cements is difficult.…”

<i>In Vivo</i> Comparative Study of Two Injectable/Moldable Calcium Phosphate Bioceramics

“…To date, several injectable biomaterials have been developed. Some of these injectable bone substitutes are made of CaP hydraulic cements that harden in the bone defect [1,2]. Others are composed of CaP granules suspended in hydrogel as they are the most interesting carriers actually used for the development of injectable bone substitute.…”

Calcium phosphate cement for augmentation did not improve results after internal fixation of displaced femoral neck fractures: A randomized study of 118 patients

“…Over the last few years, synthetic bone substitutes have been introduced for use in fracture surgery with special emphasis on the enhancement of osteopenic bone. In a mechanical study by Stankewich et al (1996), augmentation with calcium phosphate cement provided enhanced stiffness, stability and strength of fixed femoral neck fractures. When resorbable substances are used, the idea is that the initial reinforcement will be followed by progressive resorption over timeassociated with a simultaneous increase in structural support provided by the healing bone (Witschger et al 1991, Constantz et al 1995, Kopylov et al 1996, Stankewich et al 1996, Mainil et al 1997, Moore et al 1997, Frankenburg et al 1998, Goodman et al 1998, Knaack et al 1998, Yetkinler et al 1999, Larsson and Bauer 2002.…”