title: ProDisc-L learning curve: 24-Month clinical and radiographic outcomes in 44 consecutive cases.
abstract: BACKGROUND
  Total disc replacement (TDR) promises preservation of spine biomechanics in the treatment of degenerative disc disease but requires more careful device placement than tradition fusion and potentially has a more challenging learning curve.
  
  
  METHODS
  A cohort of 44 consecutive patients had 1-level lumbar disc replacement surgery at a single institution by a single surgeon. Patients were followed up clinically and radiographically for 24 months. Patients were divided into 2 groups of 22 sequential cases each. Clinically, preoperative and postoperative Oswestry Disability Index, visual analog scale, Short Form 12 (SF-12) Mental and Physical Components, and postoperative satisfaction were measured. Radiographically, preoperative and postoperative range of motion (ROM) dimensions, prosthesis deviation from the midline, and disc height were measured. TDR-related complications were noted. Logarithmic curve-fit regression analysis was used to assess the learning curve.
  
  
  RESULTS
  Operative time decreased as cases progressed, with an asymptote after 22 cases. The operative time for the later group was significantly lower (P < .0005), but hospital stay was significantly longer (P = .03). There was no significant difference in amount of blood loss (P = .10) or prosthesis midline deviation (P = .86). Clinically, there was no significant difference in postoperative scores between groups in Oswestry Disability Index (P = .63), visual analog scale (P = .45), SF-12 Mental Component (P = .66), SF-12 Physical Component (P = .75), or postoperative satisfaction (P = .92) at 24 months. Radiographically, there was no significant difference in improvement between groups in ROM (P = .67) or disc height (P = .87 for anterior and P = .13 for posterior) at 24 months. For both groups, there was significant improvement for all clinical outcomes and disc height over preoperative values. One patient in the later group had device failure with subluxation of the polyethylene, which required revision.
  
  
  CONCLUSIONS
  Early experience can quickly reduce operative time but does not affect clinical outcomes or ROM significantly (level IV case series).
  
  
  CONCLUSIONS
  Lumbar TDR is a rapidly learnable technique in treatment of degenerative disc disease.
authors.affiliation: Yale Orthopedics/Spine Service, New Haven, CT.
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Low
authors.affiliation: Yale Orthopedics/Spine Service, New Haven, CT.
authors.forename: Jerry
authors.initials: J
authors.lastname: Du
authors.affiliation: Yale Orthopedics/Spine Service, New Haven, CT.
authors.forename: Kai
authors.initials: K
authors.lastname: Zhang
authors.affiliation: Yale Orthopedics/Spine Service, New Haven, CT.
authors.forename: James J
authors.initials: JJ
authors.lastname: Yue
keywords: Learning curve; ProDisc-L; Total disc replacement