title: Footprint mismatch in total cervical disc arthroplasty.
abstract: OBJECTIVE
  Cervical disc arthroplasty has become a commonplace surgery for the treatment of cervical radiculopathy and myelopathy. Most manufacturers derive their implant dimensions from early published cadaver studies. Ideal footprint match of the prosthesis is essential for good surgical outcome.
  
  
  METHODS
  We measured the dimensions of cervical vertebrae from computed tomography (CT) scans and to assess the accuracy of match achieved with the most common cervical disc prostheses [Bryan (Medtronic), Prestige LP (Medtronic), Discover (DePuy) Prodisc-C (Synthes)]. A total of 192 endplates in 24 patients (56.3 years) were assessed. The anterior-posterior and mediolateral diameters of the superior and inferior endplates were measured with a digital measuring system.
  
  
  RESULTS
  Overall, 53.5 % of the largest device footprints were smaller in the anterior-posterior diameter and 51.1 % in the mediolateral diameter were smaller than cervical endplate diameters. For levels C5/C6 and C6/C7 an inappropriate size match was noted in 61.9 % as calculated from the anteroposterior diameter. Mismatch at the center mediolateral diameter was noted in 56.8 %. Of the endplates in the current study up to 58.1 % of C5/C6 and C6/C7, and up to 45.3 % of C3/C4 and C4/C5 were larger than the most frequently implanted cervical disc devices.
  
  
  CONCLUSIONS
  Surgeons and manufacturers should be aware of the size mismatch in currently available cervical disc prostheses, which may endanger the safety and efficacy of the procedure. Undersizing the prosthetic device may lead to subsidence, loosening, heterotopic ossification and biomechanical failure caused by an incorrect center of rotation and load distribution, affecting the facet joints.
authors.affiliation: Department of Orthopaedic Surgery, Innsbruck Medical University, Anichstr. 35, 6020 Innsbruck, Austria. martin.thaler@uki.at
authors.forename: Martin
authors.initials: M
authors.lastname: Thaler
authors.forename: Sebastian
authors.initials: S
authors.lastname: Hartmann
authors.forename: Michaela
authors.initials: M
authors.lastname: Gstöttner
authors.forename: Ricarda
authors.initials: R
authors.lastname: Lechner
authors.forename: Michael
authors.initials: M
authors.lastname: Gabl
authors.forename: Christian
authors.initials: C
authors.lastname: Bach
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007403:Intervertebral Disc / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D019736:Prostheses and Implants; D011474:Prosthesis Design; D011843:Radiculopathy / Q000601:surgery; D013118:Spinal Cord Diseases / Q000601:surgery; D014057:Tomography, X-Ray Computed; D059145:Total Disc Replacement / Q000295:instrumentation* / Q000379:methods; D016896:Treatment Outcome