Bone defect reconstruction with a novel biomaterial containing calcium phosphate and aluminum oxide reinforcement.

BACKGROUND: Reconstruction of metaphyseal fractures represents a clinical challenge for orthopedic surgeons. Especially in osteoporotic bone, these fractures are frequently accompanied by osseous substance defects. In order to ensure rapid mobilization of patients, high stability requirements must be met by osteosynthesis. Various bone graft materials have been introduced in the past, such as autologous bone or exogenous bone substitute materials. These are used as bone void fillers or as augmentation techniques to ensure safe fixation of osteosynthesis. New calcium phosphate-based bone void-filling materials could be a promising alternative to autologous bone or to the currently and widely used polymethylmethacrylate (PMMA)-based cement. The aim of this study was to evaluate a novel paste-like bone void filler in vivo and in vitro with regard to biocompatibility and osteoconductivity. METHODS: In addition to in vitro testing of cell compatibility using pre-osteoblasts (MC3T3-E1), 35 Wistar rats were treated in vivo with implantation of various material mixtures based on calcium phosphate and aluminum oxide reinforcement in a metaphyseal drill hole defect. After 4 weeks, an examination by micro-computed tomography (µCT) and histology was performed. RESULTS: The in vitro analysis showed good biocompatibility with a high cell survival of osteoblasts. In the in vivo experiments, a significantly higher bone ingrowth compared to the empty defect was shown by µCT and histological analysis. Here, the group receiving material reinforced with aluminum oxide (Al2O3) showed a bone volume/tissue volume (BV/TV) of 89.19% compared to a BV/TV of 83.14% for the empty defect (p = 0.0013). In the group treated with a polysaccharide matrix, no increase in BV/TV was observed given a mean ratio of 80.14%. Scoring of histological sections did not reveal a significant difference between CaP and CaP that was substituted with Al2O3. CONCLUSION: The results of this study show an encouraging first step towards the development of new pasty, bone void-filling materials. We demonstrated that a new paste-like bone-filling material, based on calcium phosphate granulates and aluminum oxide to provide strength, exhibits good biocompatibility and osteoconductivity. Further biomechanical test in an osteoporotic animal model will have to be performed, to prove feasibility in metaphyseal defects.

The point of epiphyseal penetration affects rotational stability of screw fixation in slipped capital femoral epiphysis: A biomechanical study.

The epiphyseal tubercle, a posterosuperior projection of the epiphysis into the metaphysis, serves as the axis of rotation in slipped capital femoral epiphysis (SCFE) and a source of physeal stability. We hypothesized that in a biomechanical model of single screw fixation of stable SCFE, a screw passing through the epiphyseal tubercle (the axis of rotation) would confer less rotational stability than a centrally placed screw. Three femurs were selected from a sample population of 8- to 15-year-old healthy hips to represent three stages of maturation: a "young" femur with a prominent epiphyseal tubercle and decreased epiphyseal cupping around the metaphysis, a "median" femur with a subsiding tubercle, and a "mature" femur with a subsided epiphyseal tubercle and increased peripheral epiphyseal cupping. Specimens were three-dimensional printed with one of two screw trajectories: passing centrally in the epiphysis or directly through the epiphyseal tubercle. Resistance to rotational displacement was measured through stiffness and maximum torque over 30° degrees of displacement. In the "young" model, epiphyseal tubercle screw position conferred less rotational stiffness and required less maximum torque during rotational displacement when compared to a centrally placed screw (P < .001). In the "median" and "mature" models where the tubercle has subsided and is replaced by peripheral epiphyseal cupping, screw position through the tubercle was associated with equal or greater rotational stiffness and maximum torque during displacement as a centrally placed screw.

Growth Modulation for Knee Coronal Plane Deformities in Children With Nutritional Rickets: A Prospective Series With Treatment Algorithm.

To report prospectively the radioclinical outcome of guided growth surgery for coronal plane deformities around the knee in young children with nutritional rickets on the intermediate term, to assess the responsiveness of torsional deformities of the tibias to guided growth regarding function and objective clinical parameters, and to propose a treatment algorithm. Methods: Fifty children (male:female, 27:23) with knee coronal plane deformities (knees:physes, 86:99), (varum:valgum, 51:35) secondary to nutritional rickets were subjected to femoral and/or tibial temporary hemiepiphysiodesis using a two-hole 8-plate. The mean age at implantation was 3.8 ± 1.5 years (range 2.5 to 5). The mean follow-up was 2.8 years (range 2 to 4). All children received a standing full-length AP radiographs of both lower limbs in neutral rotation to measure the mechanical axis deviation, tibiofemoral angle, and joint orientation angles. Tibial torsion was objectively assessed by measuring the bimalleolar axis. Results: The radiologic measurements, tibiofemoral angle, mechanical axis deviation, mechanical lateral distal femoral angle, medial proximal tibial angle, and Hilgenreiner-epiphyseal angle, showed a highly statistically significant improvement (P ≤ 0.001). Radiographic outcomes correlated with their clinical counterparts. The mean duration of correction of the mechanical axis was 10.8 ± 2.4 months (7 to 21). The mean follow-up for rebound of the deformity was 1.5 years (range 1 to 3). Conclusion: The radioclinical outcome is rewarding with a tolerable complication profile. The mechanical complications were mostly related to lengthy implant retainment encountered in severe deformities. Internal tibial torsion seems profoundly responsive to correction of coronal plane deformity. And, derotation osteotomies are rarely justified. Our proposed algorithm may be used as a decision-taking guide for achieving the desired growth modulation in a more efficient manner.

Evaluation of four biodegradable, injectable bone cements in an experimental drill hole model in sheep.

Four cement applications were tested in this investigation. Two dicalcium phosphate dihydrate (DCPD-brushite) hydraulic cements, an apatite hydraulic fiber loaded cement, and a calcium sulfate cement (Plaster of Paris) were implanted in epiphyseal and metaphyseal cylindrical bone defects in sheep. The in vivo study was performed to assess the biocompatibility and bone remodeling of four cement formulations. After time periods of 2, 4, and 6 months, the cement samples were clinically and histologically evaluated. Histomorphometrically, the amount of new bone formation, fibrous tissue, and bone marrow and the area of remaining cement were measured. In all specimens, no signs of inflammation were detectable either macroscopically or microscopically. Cements differed mainly in their resorption time. Calcium sulfate was already completely resorbed at 2 months and showed a variable amount of new bone formation and/or fibrous tissue in the original drill hole over all time periods. The two DCPD cements in contrast were degraded to a large amount at 6 months, whereas the apatite was almost unchanged over all time periods.

Guided growth for pathological physes: radiographic improvement during realignment.

BACKGROUND: Children with rickets are prone to having deformities of the lower extremities that are bilateral and often symmetrical. Although initially attributed to pathological or "sick" physes, the deformities are eventually seen in the metaphyses and diaphyses of the long bones; if left untreated, they may result in bone pain and stress fractures. The orthopaedists' role in managing these children is to correct and maintain alignment. Alternatively, we have exploited the use of hemiepiphysiodesis or guided growth, using staples or, more recently, the 8-plate (Orthofix, Verona, Italy). While gradually normalizing the mechanical axis, we have noted improvement in the appearance and width of all of the ipsilateral physes, not only at the knee but at the hip and ankle as well. This report summarizes our observations of the effects on the pathological physes in a group of patients with rickets who were preferentially treated with guided growth, often starting at a young age. METHOD: This retrospective review approved by an institutional review board included 14 children with rickets, including 10 treated with staples and 4 with 8-plates, who collectively underwent a total of 68 hemiepiphysiodeses (guided growth) and 35 osteotomies. Each was under appropriate medical management during the entire course of treatment, before and after surgery. We measured the mechanical axis deviation and anatomic angles of the femur and proximal tibia, noting the width and appearance of their physes at the hips, knees, and ankles preoperatively and upon correction of the axis. RESULTS: Of the 10 stapled patients, we noted 24 (45%) of 53 migrations and 41% rebound deformity. Four patients with 15 deformities that corrected with 8-plates experienced no hardware migration; for them, it is too early to comment on rebound deformity. While gradually correcting the mechanical axis, we have noted improvement in the appearance and width, not only of the pan-genu physes but also of remote physes at the hip and ankle. We suspect that the improved quality of the physes reflects not only the normalization of the mechanical axis but also the corresponding resolution of the waddling (varus) or circumduction (valgus) gait pattern. CONCLUSION: We recommend early intervention, via guided growth, to restore and preserve a neutral axis so that the child can enjoy a normal lifestyle while maximizing the growth potential of his or her physes, not only of the knees but the hips and ankles as well. We believe that by correcting and maintaining alignment, secondary bony deformities may be ameliorated and osteotomies for angular correction deferred if not avoided altogether. LEVEL OF EVIDENCE: IV (retrospective clinical series).

Cone epiphysis of the knee and scurvy.

A rare case of metaphyseal cupping of the distal femur resulting from infantile scury in a child is reported. The radiological and surgical aspects of this case are of particular interest. MRI demonstrated central epiphysiodesis of the right knee, surgery achieved rupture of the epiphyseal plate and resulted in femoral lengthening. The child's limp disappeared as a result.