title: Subsidence and malplacement with the Oblique Maverick Lumbar Disc Arthroplasty: technical note.
abstract: BACKGROUND
  The A-Mav (Medtronic, Sofamor Danek, Memphis, TN) is a well-established lumbar total disc arthroplasty device. The O-Mav (Medtronic) is a more recent innovation designed to minimize the potential vascular complications associated with A-Mav insertion at L4/5. No study has hitherto studied the relative accuracy or safety of the two techniques.
  
  
  OBJECTIVE
  To compare the accuracy of lumbar disc arthroplasty placement by using the anterior technique (A-Mav) with the oblique (O-Mav) technique.
  
  
  METHODS
  Technical report.
  
  
  METHODS
  Fourteen patients.
  
  
  METHODS
  Implant placement accuracy on high-resolution computed tomography scan. Comparative morbidity, mortality, blood loss, and operating time were also assessed.
  
  
  METHODS
  Patients were considered for lumbar disc arthroplasty who had suffered chronic discogenic low back pain unresponsive to nonoperative management for at least 6 months. All patients were operated on at the L4/5 level. A-Mavs were inserted in 7 patients and O-Mavs in 7. Implant placement was analyzed postoperatively by using computer software on high-resolution computed tomography scan with respect to four parameters: (1) off-center malplacement, (2) axial rotational malplacement, (3) coronal tilt, and (4) vertebral body susbsidence. Comparative morbidity, mortality, blood loss, and operating time were also assessed.
  
  
  RESULTS
  Subsidence, off-center malplacement, and rotational malplacement were significantly increased in O-Mavs compared with A-Mavs (4.3+/-0.6 mm vs. 1.6+/-0.6 mm, p=.008; 3.1+/-0.4 mm vs. 1.3+/-0.4 mm, p=.006; 6.5 degrees +/-1.2 degrees vs. 3.8 degrees +/-0.4 degrees , p=.046). No significant differences were found between O-Mavs and A-Mavs in tilt, operating time, blood loss, or morbidity and mortality.
  
  
  CONCLUSIONS
  O-Mav insertion appears to be complicated by significantly greater vertebral body subsidence and malplacement than A-Mav insertion. A-Mav insertion therefore appears to be more accurate and less complicated yet equally as safe as O-Mav insertion.
authors.affiliation: Department of Spinal Surgery, University Hospital of North Tees, Hardwick, Stockton North Tees, TS19 8PE. l.a.g.marshman@btinternet.com
authors.forename: Laurence A G
authors.initials: LA
authors.lastname: Marshman
authors.forename: Tai
authors.initials: T
authors.lastname: Friesem
authors.forename: Y Raja
authors.initials: YR
authors.lastname: Rampersaud
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Le Huec
authors.forename: Manoj
authors.initials: M
authors.lastname: Krishna
mesh_terms: D000328:Adult; D019643:Arthroplasty, Replacement / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000601:surgery*; D007405:Intervertebral Disc Displacement / Q000000981:diagnostic imaging / Q000601:surgery*; D008159:Lumbar Vertebrae; D008875:Middle Aged; D019919:Prosthesis Implantation / Q000295:instrumentation* / Q000379:methods; D011859:Radiography; D015203:Reproducibility of Results