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Minimally Invasive Percutaneous Trans-Isthmic Fixation for Vertebral Spondylolysis under CT and Fluoroscopic Guidance: Description of a New Technique 2011

Interventional Spine

Patrick, Browaeys, MD
Nicolas, Amoretti, MD, Non ASSR Member

Paper/Non-Mentor

Purpose

To describe and analyse the outcome of a new method of spondylolysis treatment which consists of a direct trans-isthmic fixation, realized under CT and fluoroscopic guidance and under local anaesthesia.

Methods & Materials

Prospective study including 10 patients (4 males & 6 females, mean age 57) between Jan 2007 and Jan 2008. Inclusion criteria were: a)bilateral L5-S1 spondylolysis with grade 1 or 2 associated spondylolisthesis; b) refractory pain to medical therapy and paraisthmic infiltration under CT guidance; c) orthopedic surgical indication for classic osteosynthesis. Visual Analogic Score (VAS) for pain and Oswestry Disability Index (ODI) for daily activity were measured by an independent evaluator before the procedure, at 1, 3, 6, 12 and 24 months after the procedure. Technique itself consists of an isotropic CT acquisition of the lumbar spine (GE Lightview 8 rows MSCT, GE Healthcare, Milwaukee, MI, USA). Under surgical conditions of aseptia and local anaesthesia, a 20-Gauge Shiba needle is first inserted on each side through the spondylolysis under fluoroscopic guidance, and after planification of the entry point and trajectory based on multiplanar reformation of the CT acquisition. Transfixition of the spondylolysis by the needle is assessed by iterative CT acquisition. A 13-Gauge Trocar t'AM (Thiebaud, France) is then inserted over the Shiba needle whom hub has been removed. Rotation motion is prefered over hammer for the trocar progression, up to the pedicle. A Kirschner wire is then inserted within the trocar and anchored to the pedicle. Trocar is withdrawn, and a 4mm self-drilling self-tapping Asnis IV screw (Stryker, Switzerland) is positioned over the K-wire. The length of the screw is calculated after the isthmus morphology using the CT acquisition. Fixation of the screw within the isthmus is done under fluoroscopic guidance and iterative CT acquisition to check its optimal placement and avoidance of nervous structures or intracanal cortical disruption. K-wire is finally withdrawn and a final CT acquisition is performed to confirm correct positioning of the screws.

Results

Bilateral minimally invasive percutaneous spondylolysis was successful in each patient. A total of 20 screws were placed (2 by patient) Average procedure time was 50 minutes. Patients were hospitalized for a total of 48h and instructed to return to full activity immediately after discharge. No complication was observed during the procedure. There was no significant bleeding. No infection occurred during the immediate post intervention period nor during the 2 years follow-up. No screw disruption nor displacement were observed during the 2 years follow-up. The VAS for pain decreased from 7.8 +/- 1.7 before the procedure to 1.9 +/- 1.2 after the procedure (p<0.001). Post-procedure VAS were unchanged at 1, 3, 6, 12 and 24 months. The ODI for daily activity decreased from 62.3 +/- 17.2% before the procedure to 15.1 +/- 6% after the procedure (p<0.001). Post-procedure ODI were also unchanged at 1, 3, 6, 12 and 24 months.

Conclusion

Trans-isthmic fixation under CT and fluoroscopic guidance appears to be a safe and effective therapeutic procedure for L5-S1 spondylolysis with low-grade spondylolisthesis. To our knowledge, this technique has never been described. We think that this procedure might improve patient care in this specific indication, by minimizing post-operative disability compared to classic open surgery, both because of absence of soft tissue injury and avoidance of general anaesthesia. It could also significantly reduce the overall treatment cost, with a limited hospitalisation time and a lighter procedure when compared to classic surgery.

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