title: Computerized tomography based "patient specific blocks" improve postoperative mechanical alignment in primary total knee arthroplasty.
abstract: OBJECTIVE
  To compare the postoperative mechanical alignment achieved after total knee arthroplasty (TKA) using computer tomography (CT) based patient specific blocks (PSB) to conventional instruments (CI).
  
  
  METHODS
  Total 80 knees were included in the study, with 40 knees in both the groups operated using PSB and CI. All the knees were performed by a single surgeon using the same cruciate sacrificing implants. In our study we used CT based PSB to compare with CI. Postoperative mechanical femoro-tibial angle (MFT angle) was measured on long leg x-rays using picture archiving and communication system (PACS). We compared mechanical alignment achieved using PSB and CI in TKA using statistical analysis.
  
  
  RESULTS
  The PSB group (group 1) included 17 females and seven males while in CI group (group 2) there were 15 females and eight males. The mean age of patients in group 1 was 60.5 years and in group 2 it was 60.2 years. The mean postoperative MFT angle measured on long-leg radiographs in group 1 was 178.23° (SD = 2.67°, range: 171.9° to 182.5°) while in group 2, the mean MFT angle was 175.73° (SD = 3.62°, range: 166.0° to 179.8°). There was significant improvement in postoperative mechanical alignment (P value = 0.001), in PSB group compared to CI. Number of outliers were also found to be less in group operated with PSB (7 Knee) compared to those operated with CI (17 Knee).
  
  
  CONCLUSIONS
  PSB improve mechanical alignment after total knee arthroplasty, compared to CI. This may lead to lower rates of revision in the PSB based TKA as compared to the conventional instrumentation.
authors.affiliation: Raju Vaishya, Vipul Vijay, Vikas P Birla, Amit K Agarwal, Department of Orthopaedics, Joint Replacement and Arthroscopy, Indraprastha Apollo Hospital, New Delhi 110076, India.
authors.forename: Raju
authors.initials: R
authors.lastname: Vaishya
authors.affiliation: Raju Vaishya, Vipul Vijay, Vikas P Birla, Amit K Agarwal, Department of Orthopaedics, Joint Replacement and Arthroscopy, Indraprastha Apollo Hospital, New Delhi 110076, India.
authors.forename: Vipul
authors.initials: V
authors.lastname: Vijay
authors.affiliation: Raju Vaishya, Vipul Vijay, Vikas P Birla, Amit K Agarwal, Department of Orthopaedics, Joint Replacement and Arthroscopy, Indraprastha Apollo Hospital, New Delhi 110076, India.
authors.forename: Vikas P
authors.initials: VP
authors.lastname: Birla
authors.affiliation: Raju Vaishya, Vipul Vijay, Vikas P Birla, Amit K Agarwal, Department of Orthopaedics, Joint Replacement and Arthroscopy, Indraprastha Apollo Hospital, New Delhi 110076, India.
authors.forename: Amit K
authors.initials: AK
authors.lastname: Agarwal
keywords: Arthroplasty; Conventional jigs; Knee; Patient specific jigs; Replacement