Comparison of 2 Radiographic Techniques for Measurement of Tibiofemoral Joint Space Width

Abstract

Background:No consensus is available regarding the best method for measuring tibiofemoral joint space width (JSW) on radiographs to quantify joint changes after injury. Studies that track articular cartilage thickness after injury frequently use patients’ uninjured contralateral knees as controls, although the literature supporting this comparison is limited.Purpose:(1) To compare JSW measurements using 2 established measurement techniques in healthy control participants and (2) to determine whether the mean JSW of the uninjured contralateral knee in a cohort with anterior cruciate ligament (ACL) reconstruction is different from that obtained from a true control population.Study Design:Cohort study (diagnosis); Level of evidence, 2.Methods:Medial and lateral JSWs were measured on standardized, bilateral, semiflexed metatarsophalangeal positioning, posteroanterior radiographs of 60 healthy individuals (26 females; mean ± SD age, 25 ± 6.2 years; no history of knee injury) via 2 published techniques: a computerized surface-delineation method (surface-fit method) and a manual digitization method (midpoint method). Bland-Altman method was used to examine the agreement between JSW measurements obtained with the 2 methods and to examine the agreement between measurements obtained on left and right knees within a participant for each measurement method. Within- and between-participant variance components and intraclass correlation coefficients (ICCs) were computed for JSW measurements corresponding to each method. Two-sample t tests were used to compare the surface-fit method measurements of mean JSW of the true control group (n = 60) with the previously published mean JSW measurements from the Multicenter Orthopaedics Outcomes Network (MOON) nested cohort of 262 contralateral uninjured knees 2 to 3 years after ACL reconstruction.Results:For JSW in the medial compartment, the surface-fit method had lower within-participant interknee variability (σ2 within, 0.064; 95% CI, 0.04-0.09) compared with the midpoint method (σ2 within, 0.28; 95% CI, 0.20-0.43) and a higher ICC (0.93 vs 0.65; P < .001). Lateral JSW values were similar for the surface-fit method (σ2 within, 0.27; 95% CI, 0.18-0.43) and the midpoint method (σ2 within, 0.20; 95% CI, 0.14-0.31), with ICCs of 0.75 and 0.77, respectively (P = .80). With the surface-fit method, mean JSW measurements of the medial and lateral compartments of a control population were not significantly different from the contralateral uninjured knees of patients after ACL reconstruction.Conclusion:For measuring medial JSW, the surface-fit method was less variable across knees within a participant than the midpoint method, as evidenced by larger ICCs and lower interknee variability. For measuring lateral JSW, the 2 methods were similar. The JSW measurements of uninjured contralateral knees of patients with ACL reconstruction at 2 to 3 years postsurgery were not significantly different from those of a cohort of healthy control participants. Future work should be performed to demonstrate the ...

Differences in the Lateral Compartment Joint Space Width After Anterior Cruciate Ligament Reconstruction: Response

“…We evaluated the measurement technique in a separate manuscript and found that the difference between normal right and left knees is 0.04 mm (95% CI, –0.18 to 0.26 mm), with an interknee estimate of variability of s 2 within = 0.27 (95% CI, 0.18-0.43). 1 We agree that the difference is small and the variability in this measurement is large, as evidenced by the large standard deviation and the large dispersion of data points presented in our figures. We do not think that this is a clinically significant difference for the patients at the 2-year time point; however, this is one of the largest reported prospective longitudinal cohorts utilizing a standard radiograph for joint space narrowing in the anterior cruciate ligament literature.…”

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“…(C) The lateral and medial width of the joint space were analyzed by grouping the space between the edges of the femoral epicondyles into four quadrants. Then, the width of the joint space was evaluated 12 . (D) The correction angle was analyzed as described in the literature 14 .…”