PubMed · 9525163
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V I Sendax. 1996. Mini-implants as adjuncts for transitional prostheses.. https://pubmed.ncbi.nlm.nih.gov/9525163/
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STUDY DESIGN: A series of 65 instrumented patients without stimulation were compared with a later series of 65 patients with instrumentation and implantable electrical stimulation. The groups were evaluated for risk factors, age, diagnostic groups, levels fused, and radiographic and clinical success. OBJECTIVES: To test the efficacy of electrical stimulation in instrumented high-risk lumbar fusions. SUMMARY OF BACKGROUND DATA: Spinal instrumentation and implantable electrical stimulation have been shown to improve fusion success rates. METHODS: All patients were instrumented via pedicle screws and autologous bone graft. Diagnostic groups were evaluated, and the risk factors in each group were identified and compared. Postoperation management and follow-up regimen were similar in each group. Radiographs were evaluated via Dawson's criteria and confirmed by an independent radiologist. Clinical success was evaluated via the Modified Smiley-Webster Scale and confirmed by a second orthopedic surgeon. RESULTS: Fusion success was 95.6% in the stimulated group compared with 87% in the nonstimulated group (P = 0.05). Clinical success was 91% in the stimulated group and 79% in the nonstimulated group (P = 0.02). In a workers' compensation subset, fusion success was 93% in the stimulated group and 81% in the nonstimulated group. Clinical success was 57% in the stimulated group and 46% in the nonstimulated group. CONCLUSIONS: The results from using both instrumentation and electrical stimulation in a high-risk pool of patients show a statistically significant difference, with higher rates of fusion and clinical success than in a similar pool that did not receive stimulation.
STUDY DESIGN: Kappa statistics were used to compare the accuracy of two different techniques for verifying pedicle screw pilot hole placement in cadaveric vertebrae. OBJECTIVE: To determine whether clinicians radiographically detect misplaced pedicle screw holes with greater sensitivity and specificity when beaded wires rather than straight Kirschner wires are used. SUMMARY OF BACKGROUND DATA: Pedicle screws commonly are used in orthopedic surgery to obtain and maintain spinal stability. Pedicle screws are reportedly misplaced at a rate of 20% to 40%. Radiographic verification is commonly used to place pedicle screw pilot holes, but this technique is known to be less than 100% accurate. Computer-assisted techniques may allow more accurate screw placement, but these techniques require expensive equipment. METHODS: Pedicle screw pilot holes were drilled into 12 human lumbar and thoracic vertebrae. Some of the holes were misplaced deliberately so that they violated the pedicle walls. Lateral and posteroanterior radiographs of the vertebrae were evaluated by 13 experienced orthopedic spine surgeons and 3 inexperienced observers. At different times, the observers were shown radiographs depicting Kirschner wires or beaded wires placed in the pilot holes. Observers indicated whether they thought the pedicle screw pilot hole violated the pedicle. RESULTS: The sensitivity and specificity of using posteroanterior or lateral radiographs to detect misplaced pedicle screws were increased when beaded wires were placed in the pilot holes. CONCLUSIONS: Radiographic evaluation of beaded wires placed in pedicle screw pilot holes can be both sensitive and specific for misplaced screws. The highest sensitivity and specificity were found using posteroanterior radiographs.
STUDY DESIGN: A static nondestructive bending analysis of pedicle screws inserted into vertebral analogues was conducted. Pedicle screw load was studied as a function of variables in insertion technique. OBJECTIVES: To determine how the sagittal bending moment in pedicle screws is affected by changes in pedicle screw length, insertional depth, and sagittal placement. BACKGROUND DATA: An unexpectedly high rate of clinical failure has been observed in pedicle screws used in short-segment instrumentation for unstable burst fractures. The majority of screws fail in sagittal bending within the pedicle. Little is known of the insertion technical factors that affect in situ loads incurred by pedicle screws. METHODS: Synthetic vertebral analogues were fabricated. Pedicle screws internally instrumented with strain gauges were used as load transducers to determine screw bending moments within the pedicle and body of the analogue. Analogues were loaded in compression to simulate loading of an unstable burst fracture. RESULTS: Screw bending moments within the pedicle increased 33% and 52% when screws were left 3 mm and 5 mm short of full insertion. Intrapedicular moments increased 20% to 29% in screws inserted superiorly or inferiorly within the pedicle. Thirty-five-millimeter screws developed intrapedicular moments 16% higher than 40-mm and 45-mm screws. CONCLUSIONS: In situ pedicle screw loads increased significantly as a direct result of variations in surgical technique. Screws left short of full insertion, placed off center in the sagittal plane of the pedicle, or less than 40 mm long developed increased intrapedicular bending moments.