PubMed · 7208000
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Iu I Diukov. 1980. [Errors, hazards and complications in using metallosynthesis].. https://pubmed.ncbi.nlm.nih.gov/7208000/
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STUDY DESIGN AND OBJECTIVE: A mechanical skull model was used to compare axial loads to failure for three marketed and one experimental halo ring. SUMMARY OF BACKGROUND DATA: Open-back halo rings have become increasingly popular; however, to the authors' best knowledge the literature provides no comparison of the fixation strength of an open-back halo versus the traditional closed design. METHODS: A model biomechanically similar to a human skull was used to compare the axial force necessary to distract each of four halo rings to failure. Three clinically used halo rings were compared: a closed titanium ring, an open titanium ring, and an open graphite ring. One additional open titanium halo ring was constructed with an angular profile; this ring was compared with the clinically used halos. RESULTS: The mean force to failure for the closed titanium ring significantly exceeded that for the open rings (P < 0.005). No significant differences were noted among the open halo rings. DISCUSSION: The data obtained by use of this biomechanical model show that the closed halo ring provides distraction strength greater than that of the open rings, suggesting a more rigid system with the closed device. Use of an angular halo did not improve fixation strength in the open ring device. These findings may support use of a closed halo ring in cervical spine traction and immobilization, if this greater strength is shown to be sufficiently clinically important to offset any disadvantages of a closed ring.
STUDY DESIGN: Retrospective review of the results of submuscular rod placement with and without limited apical fusion for the treatment of severe spinal deformities in young children. OBJECTIVES: To determine the success of this method for controlling severe deformities while allowing for spinal growth and to compare this method with previously reported results. SUMMARY OF BACKGROUND DATA: A variety of methods for controlling scoliosis in young children have been reported, but complications including spontaneous fusion, loss of correction, instrumentation failure, and limited spinal growth are common. METHODS: The cases of 29 young children with progressive scoliosis or kyphoscoliosis as a result of a variety of diagnoses treated with a submuscular Isola rod and a postoperative orthosis were retrospectively reviewed. Eleven patients also had a short anterior and posterior apical fusion or convex hemiepiphysiodesis to aid in correction and stabilization of their deformity. The remaining 18 patients had a submuscular rod only. RESULTS: The mean age at surgery was 6.7 years (range, 1-11 years). The initial preoperative mean magnitude of the major curve was 66 degrees (range, 42-112 degrees ). After surgery this decreased to a mean of 38 degrees (range, 16-70 degrees ). The most recent radiographs demonstrated a mean 47 degrees curve (range, 28-79 degrees ). The mean number of lengthenings per patient has been two (range, 0-5). Nine patients have reached a suitable age and have been converted to a posterior spinal fusion and segmental spinal instrumentation. Nine complications have occurred in seven patients (24%). These included five hook displacements and three rod breakages. These were treated by hook reinsertion and rod exchange or sleeve and a repeat lengthening. There was one superficial infection treated medically. CONCLUSION: This technique is useful in the management of severe spinal deformities in young children who have either failed, or have a contraindication to, orthotic management. Complications are relatively frequent but well tolerated.
STUDY DESIGN: Synthetic spine models were used to compare the effects of hook pattern and kyphotic angulation on stiffness and rod strain in long-segment posterior spinal constructs. OBJECTIVES: To examine the biomechanical effects of hook patterns and kyphotic angulation on long-segment posterior spinal constructs. SUMMARY OF BACKGROUND DATA: Kyphotic deformities managed by increasing rod diameter and hence construct stiffness have shown decreased postoperative loss of correction and hardware complications. The biomechanical effects of hook pattern and kyphosis are unknown. METHODS: Spine models of 0 degrees, 27 degrees 54 degrees sagittal contour, composed of polypropylene vertebral blocks and isoprene elastomer intervertebral spacers, representing T3-T12, were used for biomechanical testing of long-segment posterior spinal constructs. Models were instrumented with 6.35-mm titanium rods and one of the following hook configurations: 20-hook compression, 16-hook compression, 16-hook claw apex-empty,16-hook claw apex-full, or 8-hook claw. Construct stiffness and rod strain during axial compression were determined. RESULTS: The compression-hook patterns provided at least a 45% increase in construct stiffness (P = 0.013)and a 22% decrease in rod strain (P < 0.0001) compared with those obtained with the claw-hook pattern with the best biomechanical performance. When analyzing all five hook patterns, there was a 19% decrease in construct stiffness and 27% increase in rod strain when progressing from straight alignment to 27 degrees of sagittal contour (P < 0.0001). Progressing from straight alignment to 54 degrees decreased construct stiffness by 48% and increased rod strain by 55% (P < 0.0001). Construct stiffness was inversely correlated to rod strain in all five hook patterns (R2 = 0.82-0.98, P < 0.001). CONCLUSIONS: Using compressive-hook patterns and decreasing the kyphotic deformity significantly increases construct stiffness and decreases rod strain.