title: [Lumbar and lumbo-sacral fusion using Twinflex devices in 114 cases with minimal follow-up of 1 year].
abstract: The author presents a series of 114 cases of lumbo-sacral fusion with a minimum follow-up of 1 year and a mean of 21.7 months.Since the use of the first transpedicular screws (1963 R. Roy-Camille) spinal instrumentation has considerably eased post-operative care in lumbo-sacral fusion as well as fusion rate. Recently, instrumentation has became more and more rigid. But rigidity has it's limits. Pain as well as poor bone grafting frequently occurs eventhough surgery was performed correctly. This is why the author has developed a concept of flexible transpedicular instrumentation. The aims are: - To avoid stress-shielding of the graftsimplify implantation during surgery - Avoid excessive stress on the bone and adjacent disc - Improved short and long term acceptance of instrumentation - Avoid removal of implants. Some elements guided instrumentation design. Low profile - Ease of removal - restricted number of implants and instruments. The system developed is based on transpedicular screws with 2.5 mm rods. Stainless steel was prefered to Titanium because of it's flexibility. The mechanical results of the first prospective series of 114 cases are studied. Follow up ranges from 12 to 39 months maximum with an average of 21.7 months. 65% of the patients are female. Age ranges from 14 to 89 years old with an average of 50 years.•Pathologies are : 74 cases of discopathy with or without associated disc, 8 cases of degenerative lumbar scoliosis and 32 cases of spondylolisthesis with 13 cases of isthmus lysis and 19 cases of degenerative spondylolisthesis.During the post operative period patients stand between 24 and 48 hours. Walking is allowed with twill corset during the day for the first 3 months.•Length of fixation: In 32 cases it is a floating arthrodesis (L4-5 18 cases, others 14 cases). In 82 cases sacrum is included in the fusion (L3-S1.15 cases, L4-S1.35 cases, L5-S1 20 cases, others 12 cases).•
  
  
  RESULTS
  No infections were seen. No phlebitis or pulmonary embolism.•Mechanical complications: They are analysed with an average follow up of 21.7 months and a minimum of 12 months. Screw fractures: Only one case occured at 4 months post op in a L4-5 isthmic spondylolisthesis. Fusion was still obtained within the usual 6 months. Patient went back to work on the 8 th post op month without further complication 14th month post operative. Rod fractures: Fracture of the rod is the demonstration of a pseudarthrosis when occuring between 8 to 12 months post-op. The average pseudarthrosis rate is 3.5% (4 cases). In this series we used two different size of rods. The first group consists of 65 cases with 2 mm diameter rods. The second group consists of 49 cases with 2.5 mm rods. All the pseudarthroses occured in the first group (4 cases). In the second group with an average follow up of 17.2 month no pseudarthroses occured.In 4 cases (3.5%) revision surgery was necessary. Two cases were related to pseudarthrosis and 2 cases to remove instrumentation.Fusion rate in this first prospective series is 96.5%. Rod failure in the first post operative year is the demonstration of pseudarthrosis. On the reverse non failure is a way of assessing fusion without doubt.This homogeneous series demontrates the ability of flexible fixation to obtain a high rate of fusion and a good medium term acceptibility for the patient. Instrumentation was removed only in two cases at patient request.
authors.affiliation: Institut Mutualiste Montsouris, C.M.C. de la Porte de Choisy, 6, Place de Port au Prince, F-75013, Paris, France.
authors.forename: C
authors.initials: C
authors.lastname: Mazel