Validation of joint space narrowing on plain radiographs and its relevance to partial knee arthroplasty

Abstract

Aims: To explore the clinical relevance of joint space width (JSW) narrowing on standardized-flexion (SF) radiographs in the assessment of cartilage degeneration in specific subregions seen on MRI sequences in knee osteoarthritis (OA) with neutral, valgus, and varus alignments, and potential planning of partial knee arthroplasty.

Methods: We retrospectively reviewed 639 subjects, aged 45 to 79 years, in the Osteoarthritis Initiative (OAI) study, who had symptomatic knees with Kellgren and Lawrence grade 2 to 4. Knees were categorized as neutral, valgus, and varus knees by measuring hip-knee-angles on hip-knee-ankle radiographs. Femorotibial JSW was measured on posteroanterior SF radiographs using a special software. The femorotibial compartment was divided into 16 subregions, and MR-tomographic measurements of cartilage volume, thickness, and subchondral bone area were documented. Linear regression with adjustment for age, sex, body mass index, and Kellgren and Lawrence grade was used.

Results: We studied 345 neutral, 87 valgus, and 207 varus knees. Radiological JSW narrowing was significantly (p < 0.01) associated with cartilage volume and thickness in medial femorotibial compartment in neutral (r = 0.78, odds ratio (OR) 2.33) and varus knees (r = 0.86, OR 1.92), and in lateral tibial subregions in valgus knees (r = 0.87, OR 3.71). A significant negative correlation was found between JSW narrowing and area of subchondral bone in external lateral tibial subregion in valgus knees (r = -0.65, p < 0.01) and in external medial tibial subregion in varus knees (r = -0.77, p < 0.01). No statistically significant correlation was found in anterior and posterior subregions.

Conclusion: SF radiographs can be potentially used for initial detection of cartilage degeneration as assessed by MRI in medial and lateral but not in anterior or posterior subregions. Cite this article: Bone Joint Res 2021;10(3):173-187.

Keywords: Cartilage radiography; Joint space narrowing; Osteoarthritis cartilage; Osteoarthritis radiography; Partial knee arthroplasty.

Fig. 1

Flow diagram presenting the subjects investigated from the entire Osteoarthritis Initiative Cohort. OAI, Osteoarthritis Initiative.

Fig. 2

The analyzed subregions at the tibia (left) and the femur (right). aLT, anterior lateral tibia; aMT, anterior medial tibia; ccLF, central lateral femur; ccMF, central medial femur; cLT, central lateral tibia; cMT, central medial tibia; ecLF, external central lateral femur; ecMF, external central medial femur; eLT, external lateral tibia; eMT, external medial tibia; icLF, internal central lateral femur; icMF, internal central medial femur; iLT, internal lateral tibia; iMT, internal medial tibia; pLT, posterior lateral tibia; pMT, posterior medial tibia.

Fig. 3

Posteroanterior radiography with a) upright standing position with the great toes touching the anterior wall of the frame and both feet in 10° external rotation, and b) both knees and thighs pressed against the anterior wall of the frame in order to fix flexion of the knees, resulting in vertical alignment of the patella, toes, and chest. The x-ray beam is angled 10° caudal and centred at the level of the joint line until the anterior and posterior margins of the tibial plateau superimposed.

Fig. 4

Measurements of femorotibial joint space width at increments of 0.025 using Duryea et al’s customized software tool.

Fig. 5

Data derived from Table I show the analyzed subregions at the tibia (lower section) and the femur (upper section) with highlights of specific areas of high correlation between cartilage volume loss and its corresponding (x)-specific location. Colour-coded correlations: Blue area, subregion with low statistical correlation (r < 0.7); pink area, subregion with high statistical correlation (r ≥ 0.7); red area, subregion with highest statistical correlation in its alignment group; arrow, (x)-location with highest statistical correlation in its alignment group. aLT, anterior lateral tibia; aMT, anterior medial tibia; ccLF, central lateral femur; ccMF, central medial femur; cLT, central lateral tibia; cMT, central medial tibia; ecLF, external central lateral femur; ecMF, external central medial femur; eLT, external lateral tibia; eMT, external medial tibia; icLF, internal central lateral femur; icMF, internal central medial femur; iLT, internal lateral tibia; iMT, internal medial tibia; pLT, posterior lateral tibia; pMT, posterior medial tibia.

Fig. 6

Data derived from Table II show the analyzed subregions at the tibia (lower section) and the femur (upper section) with highlights of specific areas of high correlation between cartilage thickness loss and its corresponding (x)-specific location. Colour-coded correlations: Blue area, subregion with low statistical correlation (r < 0.7); pink area, subregion with high statistical correlation (r ≥ 0.7); red area, subregion with highest statistical correlation in its alignment group; arrow, (x)-location with highest statistical correlation in its alignment group. aLT, anterior lateral tibia; aMT, anterior medial tibia; ccLF, central lateral femur; ccMF, central medial femur; cLT, central lateral tibia; cMT, central medial tibia; ecLF, external central lateral femur; ecMF, external central medial femur; eLT, external lateral tibia; eMT, external medial tibia; icLF, internal central lateral femur; icMF, internal central medial femur; iLT, internal lateral tibia; iMT, internal medial tibia; pLT, posterior lateral tibia; pMT, posterior medial tibia.

Fig. 7

Data derived from Table III show the analyzed subregions at the tibia (lower section) and the femur (upper section) with highlights of specific areas of high correlation between percentage of subchondral bone denuded of cartilage and its corresponding (x)-specific location. Colour-coded correlations: blue area, subregion with low statistical correlation (r > -0.6); pink area, subregion with high statistical correlation (r ≤ -0.7); red area, subregion with highest statistical correlation in its alignment group; arrow, (x)-location with highest statistical correlation in its alignment group. aLT, anterior lateral tibia; aMT, anterior medial tibia; ccLF, central lateral femur; ccMF, central medial femur; cLT, central lateral tibia; cMT, central medial tibia; ecLF, external central lateral femur; ecMF, external central medial femur; eLT, external lateral tibia; eMT, external medial tibia; icLF, internal central lateral femur; icMF, internal central medial femur; iLT, internal lateral tibia; iMT, internal medial tibia; pLT, posterior lateral tibia; pMT, posterior medial tibia.