title: The analysis of risk factors in no thumb test in total knee arthroplasty.
abstract: BACKGROUND
  We would like to analyze the risk factors of no thumb test among knee alignment tests during total knee arthroplasty surgery.
  
  
  METHODS
  The 156 cases of total knee arthroplasty by an operator from October 2009 to April 2010 were analyzed according to preoperative indicators including body weight, height, degree of varus deformity, and patella subluxation and surgical indicators such as pre-osteotomy patella thickness, degree of patella degeneration, no thumb test which was evaluated after medial prepatella incision and before bone resection (1st test), no thumb test which was evaluated with corrective valgus stress (2nd test, J test), and the kind of prosthesis. We comparatively analyzed indicators affecting no thumb test (3rd test).
  
  
  RESULTS
  There was no relation between age, sex, and body weight and no thumb test (3rd test). Patellar sulcus angle (p = 0.795), patellar congruence angle (p = 0.276) and preoperative mechanical axis showed no relationship. The 1st no thumb test (p = 0.007) and 2nd test (p = 0.002) showed significant relation with the 3rd no thumb test. Among surgical indicators, pre-osteotomy patella thickness (p = 0.275) and degeneration of patella (p = 0.320) were not relevant but post-osteotomy patellar thickness (p = 0.002) was relevant to no thumb test (3rd test). According to prosthesis, there was no significance with Nexgen (p = 0.575). However, there was significant correlation between Scorpio (p = 0.011), Vanguard (p = 0.049) and no thumb test (3rd test). Especially, Scorpio had a tendency to dislocate the patella, but Vanguard to stabilize the patella.
  
  
  CONCLUSIONS
  No thumb test (3rd test) is correlated positively with 1st test, 2nd test, and post-osteotomy patella thickness. Therefore, the more patella osteotomy and the prosthesis with high affinity to patellofemoral alignment would be required for correct patella alignment.
authors.affiliation: Department of Orthopedic Surgery, Seoul Sacred Heart General Hospital, Seoul, Korea.
authors.forename: Jee Hyoung
authors.initials: JH
authors.lastname: Kim
authors.forename: Song
authors.initials: S
authors.lastname: Lee
authors.forename: Dong Oh
authors.initials: DO
authors.lastname: Ko
authors.forename: Chang Wook
authors.initials: CW
authors.lastname: Yoo
authors.forename: Tae Hwan
authors.initials: TH
authors.lastname: Chun
authors.forename: Jung Soo
authors.initials: JS
authors.lastname: Lee
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D006801:Humans; D007430:Intraoperative Care / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010027:Osteotomy; D010329:Patella / Q000033:anatomy & histology* / Q000601:surgery; D010808:Physical Examination; D012307:Risk Factors