Background: The gold standard for evaluating leg alignment is a long leg standing radiograph (LSR). The research states that a correct LSR should have a patella that is centered and facing forward as well as a fibula head superimposition (FHS) with a tibia that is 1/3 larger than the fibula. The purpose of this study was to determine levels of quality for LSR by quantifying and correlating the patella position and fibular head superimposition.
Method: 741 lower limbs were included using two distinct measurement techniques, we calculated the patella position's (PD) departure from the center of the knee joint (M1 and M2). To measure the inter-rater dependability in assessing PD and FHS, intraclass correlation coefficients were determined. The Bland-Altman approach was used to compare M1 with M2's performance. We created three quality groups based on the average quantity of PD.
Results: The mean PD was 3.5 mm for M1 and 4.1 mm for M2, respectively. Three quality categories were created: group A for PD ≤ 5 mm, group B for PD 5-10 mm, and group C for PD of ≥10 mm. Group A takes up 70.9% of the LSR. Interestingly, group A's FHS was 21.3% than the typical value of 1/3.
Conclusions: The patella's center should be centered within a 5 mm range and the fibular head should be 1/5 covered from the tibia. This study is the first to define quantitative metrics based on LSR analysis.
Level of evidence: Level IV (diagnostic retrospective case series).
Keywords: Alignment; Deformity correction; Fibula; Fibula head superimposition; Fibula overlap; Knee; Long leg standing radiograph; Lower extremity; Patella; Patella deviation; Radiology; X-ray.
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