Growth and development of the pediatric cervical spine documented radiographically.

BACKGROUND: The radiographic anatomy of the cervical spine in children is complex and can be difficult to interpret. The present study was undertaken to document radiographically the growth and development of the cervical spine in a prospective, longitudinal manner and to establish standard radiographic measurements on the basis of findings in patients who were followed serially from the age of three months until skeletal maturity. METHODS: The radiographic resources of the Cleveland Study of Normal Growth and Development (Bolton-Brush Collection, Cleveland, Ohio) were reviewed. From this large database, we identified fifty boys and forty-six girls who had a sufficient number of radiographs of the cervical spine for inclusion in our study. With use of a computerized image analyzer, the growth and development of the atlantodens interval, the diameter of the spinal canal, the Torg ratio, the height and width of the second through fifth cervical vertebral bodies, the height of the dens, and the ossification of the first cervical vertebra were assessed on serial radiographs made from the age of three months until skeletal maturity. RESULTS: Serial measurements of the atlantodens interval, the anteroposterior diameter of the cervical canal, the height and anteroposterior width of the cervical vertebral bodies, and the height of the dens, made in normal, healthy children from the age of three months to fifteen years, are presented in tabular and graphic forms. The median Torg ratio was 1.47 for both males and females primarily, and it reached values of 1.06 for males and 1.10 for females by maturity. The anterior arch of the first cervical vertebra had ossified in 33% of the children by the age of three months and in 81% of the children by the age of one year. Closure of the synchondroses was completed in all children by the age of three years. CONCLUSIONS: The measurements presented in the current study are important because they are the first, as far as we know, to document the radiographic parameters of the cervical spine in children who were followed longitudinally from before the age of three years through the course of growth and development until skeletal maturity.

Subclinical slipped capital femoral epiphysis. Relationship to osteoarthrosis of the hip.

We examined the femora of 2665 adult human skeletons from an osteological collection to determine the prevalence of post-slip morphology termed femoral head-tilt deformity by Murray and pistol-grip deformity by Stulberg et al. The hypothesis was that primary osteoarthrosis of the hip is a secondary manifestation of a subclinical developmental disorder of the hip. The prevalence of post-slip morphology was 8 per cent (215 of 2665 skeletons). Severe osteoarthrosis was more prevalent in association with post-slip morphology (116 [38 per cent] of 306 hips) than in the matched controls (seventy-nine [26 per cent] of 306 hips) (p < 0.005). In the skeletons that had unilateral post-slip morphology, severe osteoarthrosis was more prevalent in the involved hips (thirty-one [37 per cent] of eighty-three) than in the contralateral, normal hips (eighteen [22 per cent] of eighty-three) (p < 0.05). Post-slip morphology, which was unrelated to age, was found to be a major risk factor for the development of high-grade osteoarthrosis. We noted evidence of high-grade osteoarthrosis in sixty-three (68 percent) of the ninety-three hips with minimum post-slip morphology in skeletons from individuals who had been fifty-six years old or more at the time of death compared with forty-five (48 percent) of the ninety-three control hips. This difference was significant (p < 0.025) [corrected]. The osteoarthrosis in the hips with post-slip morphology was distinctly characterized by anterior flattening of the acetabulum, cystic degeneration in the anterior metaphyseal-epiphyseal region, and progression to global osteoarthrosis of the hip.

Induction of bone by a demineralized bone matrix gel: a study in a rat femoral defect model.

Demineralized bone matrix contains osteoinductive factors and stimulates filling of gaps and defects with bone; however, it is difficult to handle by itself and various preparations have been tested. Demineralized bone matrix with a gel consistency now is available for clinical use. We studied, in a femoral segment defect in the rat, the effects of rat demineralized bone matrix gel with and without a ceramic substratum. This preparation is analogous to the human demineralized bone matrix in the same carrier, used clinically for humans. One hundred adult male Fischer rats were divided into 10 experimental groups. Independent variables included the presence or absence of hydroxyapatite ceramic cylinders, the presence of demineralized bone matrix in carrier or carrier alone (glycerol), and the duration of observation (1, 2, and 4 months). Defects filled with the gel alone had significantly higher radiographic scores for host-graft union at 4 months compared with ceramic with the gel, ceramic alone, or carrier alone. Demineralized bone matrix gel significantly increased the total histologic score for host-graft union, whether ceramic was present or not, and a three-way interaction occurred among ceramic, the gel, and time. Demineralized bone matrix gel was an effective inducer of bone formation in this model. An additional substratum was not required; in fact, significantly more bone was formed in the absence of the ceramic cylinder. Neither the gel nor the ceramic were impediments to revascularization of the defect. Host-graft union was enhanced by demineralized bone matrix gel but not by the ceramic cylinder.

The influence of surface-blasting on the incorporation of titanium-alloy implants in a rabbit intramedullary model.

The apposition of new bone to polished solid implants and to implants with surfaces that had been blasted with one of three methods of grit-blasting was studied in a rabbit intramedullary model to test the hypothesis that blasted implant surfaces support osseous integration. Intramedullary titanium-alloy (Ti-6Al-4V) plugs, press-fit into the distal aspect of the femoral canal, were implanted bilaterally in fifty-six rabbits. Four surface treatments were studied: polished (a surface roughness of 0.4 to 0.6 micrometer) and blasted with stainless-steel shot (a surface roughness of five to seven micrometers), with thirty-six-grit aluminum oxide (a surface roughness of five to seven micrometers), or with sixty-grit aluminum oxide (a surface roughness of three to five micrometers). Localized attachment of new bone to the surfaces of the blasted implants was present radiographically at twelve weeks. The total bone area was significantly affected by the level of the section (the diaphysis had a greater bone area than the proximal part of the metaphysis and the proximal part of the metaphysis had a greater bone area than the distal part of the metaphysis; p < 0.001) and the quadrant within each section (the posterior and anterior quadrants had greater bone area than the medial and lateral quadrants; p < 0.00001). The length of the bone-implant interface was significantly affected by the surface treatment (the length of the bone-implant interface for the implants that had been blasted with sixty-grit aluminum oxide was greater than the length for the polished implants; p = 0.02), the time after implantation (the interface was longer at six and twelve weeks than at three weeks; p < 0.00001), and the level of the section (the interface was longer at the diaphysis than at the proximal part of the metaphysis and longer at the proximal part of the metaphysis than at the distal part of the metaphysis; p = 0.004). Blasting of the surface of titanium-alloy implants did not have an effect on the area of bone formation around the implants, but it did significantly affect the area of bone formation on the implant and the shear strength at the bone-implant interface. The two effects were not necessarily parallel, as significantly less (p < 0.05) bone formed on implants that had been blasted with stainless-steel shot than on those blasted with aluminum grit, whereas their interface shear strengths were similar.

Biologic and biomechanic evaluation of posterior lumbar fusion in the rabbit. The effect of fixation rigidity.

STUDY DESIGN: The histologic and biomechanic characteristics of posterior lumbar fusion with varying rigidity of a novel internal fixation construct in the rabbit were analyzed. OBJECTIVES: To evaluate this rabbit model for future studies of fusion augmentation. SUMMARY OF BACKGROUND DATA: Previous studies in goats and dogs showed internal fixation enhances spinal arthrodesis. METHODS: Twenty eight New Zealand white rabbits underwent a posterior midline fusion from L4 to L6. Some animals received autogenous iliac crest bone graft, stabilized by wiring the superior facets bilaterally, and supplementation with polymethylmethacrylate. The experimental groups were iliac crest bone graft with either no fixation, wire fixation, or wire and polymethylmethacrylate fixation; and no graft and either no fixation, wire fixation, or wire and polymethylmethacrylate fixation. Animals were killed 2 months after surgery, and the specimens were nondestructively tested biomechanically for stiffness in six modes (flexion, extension, left and right bending, compression, and torsion) and histologically for evidence of fusion, revascularization, and new bone formation. RESULTS: Fusions with either wire or wire and polymethylmethacrylate fixation were significantly stiffer than those without fixation (P < 0.05). There was no statistical difference between the iliac crest bone graft and wire group and the iliac crest bone graft, wire, and polymethylmethacrylate group in the modes tested. Nine of 14 motion segments receiving the stiffest construct (iliac crest bone graft, wire, and polymethylmethacrylate) had evidence of solid bony fusion. None of the 12 motion segments receiving iliac crest bone graft and wire had evidence of bony fusion, but five had a fibrocartilage union with some ossification present. Eight of 12 motion segments receiving iliac crest bone graft and no fixation had predominantly fibrous unions with some fibrocartilage, and only one motion segment of 12 showed bony fusion. CONCLUSIONS: This study suggests that more rigid fixation produces more successful union in rabbit posterior spinal fusion. This model may be useful in evaluating the ability of various biomaterials to augment spinal arthrodesis.