Single-balloon kyphoplasty via an extrapedicular approach has been reported to be effective because it requires less time than conventional two-balloon kyphoplasty and has comparable therapeutic efficacy. However, single-balloon kyphoplasty is not popular because the extrapedicular approach is believed to be complicated and unsuitable for the thoracolumbar and lumbar spine. The authors describe a standardized surgical technique that utilizes a far-lateral extrapedicular approach for single-balloon kyphoplasty, which can be performed in any part of the spine by physicians without substantial difficulty.

Object. The purposes of this retrospective study were to determine the radiological changes at the index and adjacent levels after cervical arthroplasty using the Bryan disc and Prodisc-C disc after a minimum 24 months followup, and to demonstrate the possible clinical factors related to these changes. Methods. Following single-level cervical arthroplasty using either the Bryan disc or Prodisc-C, the degree of facet degeneration and other radiological changes at the index and adjacent levels were assessed by observing radiographs and CT scans at a minimum 24 months after the operations. These findings were determined in relation to the clinical outcome, various perioperative factors, and prosthesis factors. Thirty-six patients were included in this investigation (19 in the Bryan disc group and 17 in the Prodisc-C group).Results. At the index level, progression of facet arthrosis (PFA) was observed in 7 of 36 levels (1 level with the Bryan disc, 6 with the Prodisc-C). At adjacent levels, PFA was minimally observed. Heterotopic ossification (HO) was observed at 19 levels (11 with the Bryan disc, 8 with Prodisc-C). Progression of facet arthrosis at the index segments was positively related to malposition of the prosthesis on the frontal plane, and decreased postoperative functional spinal unit range of motion at the index level. Occurrence of HO was correlated with the preoperative calcification of the posterior longitudinal ligament at the operated level, regardless of prosthesis type. Clinical outcome and the occurrence of PFA or HO did not show any significant relationship.Conclusions. This study demonstrates that the incidence of PFA at the index level is 19.4% after a minimum 24-month follow-up, and occurs more frequently in the Prodisc-C group. Progression of facet arthrosis is related to less functional spinal unit range of motion and anterior placement of the prosthesis. The occurrence rate of HO is high, regardless of the type of prosthesis, and it is significantly correlated with preoperative calcification of the posterior longitudinal ligament at the operated level. (DOI: 10.3171/2010.3.SPINE09445) Key WoRDS

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