Coronal knee alignment measurements differ on long-standing radiographs vs. by navigation.

Area of Science:

• Orthopedic surgery
• Biomechanical analysis
• Medical imaging

Background:

• Long-standing radiographs (LSRs) are standard for assessing knee alignment post-total knee arthroplasty (TKA).
• Accuracy of LSRs is debated due to influencing factors.
• Computer-assisted surgery (CAS) offers precise measurements, but few studies compare it with LSRs.

Purpose of the Study:

• To compare hip-knee-ankle (HKA) angle measurements between LSRs and CAS before and after TKA.
• To evaluate the accuracy and comparability of LSRs versus CAS for knee alignment in TKA patients.

Main Methods:

• Retrospective observational study of 126 knees undergoing TKA.
• HKA angles measured using bipedal full-weight-bearing LSRs pre-operatively and 3 months post-operatively.
• Comparison of LSR measurements with data obtained from CAS.

Main Results:

• Pre-operatively, LSRs overestimated knee deformity compared to CAS (SD 2.672, LOA {-5.391; +5.082}).
• Post-operatively, LSR and CAS measurements showed poor agreement (SD 3.113, LOA {-6.426; +5.776}), with low intra-class coefficients.
• Agreement varied by alignment type, with poor reliability for normal and >10° valgus alignments.

Conclusions:

• LSRs are not directly comparable to CAS for knee alignment assessment after TKA.
• Pre-operative LSRs tend to overestimate deformity when compared to CAS.
• Findings support the continued use of LSRs for routine assessment and healthcare cost estimations.