Weight bearing versus conventional CT for the measurement of patellar alignment and stability in patients after surgical treatment for patellar recurrent dislocation

Radiol Med. 2021 Jun;126(6):869-877. doi: 10.1007/s11547-021-01339-7. Epub 2021 Mar 3.


Purpose: To compare weight-bearing cone-beam computer tomography (CBCT) and conventional computer tomography (CT)-based measurements of patellofemoral alignment and stability in patients surgically treated for recurrent patellar dislocation. These scans implied respectively single-leg up-right posture, the knee flexed, and lower limb muscles activation, versus supine position with the knee extended.

Methods: A total of 17 patients (11 males/6 females) after surgical reconstruction with fascia lata allograft for recurrent patellofemoral dislocation were analyzed at 60-month follow-up. Tilt and congruence angles and tibial tuberosity-trochlear groove (TT-TG) offset were measured on images obtained from CBCT and conventional CT scans by three independent and expert radiologists. Paired t tests were performed to compare measurements obtained from the two scans. Inter-rater reliability was assessed using a two-way mixed-effects model intra-class correlation coefficient (ICC).

Results: Only TT-TG offset was found significantly smaller (p < 0.001) in CBCT (mean 9.9 ± 5.3 mm) than in conventional CT (mean 15.9 ± 4.9 mm) scans. ICC for tilt and congruence angles and for TT-TG offset ranged between 0.80-0.94 with measurements in CBCT scans, between 0.52 and0.78 in conventional CT.

Conclusion: In patients surgically treated for recurrent patellar dislocation, TT-TG offset was found overestimated with conventional CT. All measurements of patellofemoral stability and alignment were found more consistent when obtained with weight-bearing CBCT compared to conventional CT.

Keywords: Cone-beam CT; Conventional CT; Patellofemoral instability; Weight-bearing.

MeSH terms

  • Adolescent
  • Adult
  • Cone-Beam Computed Tomography / methods*
  • Female
  • Follow-Up Studies
  • Humans
  • Male
  • Orthopedic Procedures / methods*
  • Patellar Dislocation / physiopathology*
  • Patellar Dislocation / surgery
  • Patellofemoral Joint / diagnostic imaging
  • Patellofemoral Joint / physiopathology*
  • Postoperative Period
  • Range of Motion, Articular / physiology
  • Reproducibility of Results
  • Retrospective Studies
  • Time Factors
  • Weight-Bearing / physiology*
  • Young Adult