Relationships between tibial rim alignment and joint space width measurement reproducibility in non-fluoroscopic radiographs of osteoarthritic knees

Fixed-flexion knee radiography using a new positioning device produced highly repeatable measurements of joint space width: ELSA-Brasil Musculoskeletal Study (ELSA-Brasil MSK)

OBJECTIVE

To describe the performance of a non-fluoroscopic fixed-flexion PA radiographic protocol with a new positioning device, developed for the assessment of knee osteoarthritis (OA) in Brazilian Longitudinal Study of Adult Health Musculoskeletal Study (ELSA-Brasil MSK).

MATERIAL AND METHODS

A test-retest design including 19 adults (38 knee images) was conducted. Feasibility of the radiographic protocol was assessed by image quality parameters and presence of radioanatomic alignment according to intermargin distance (IMD) values. Repeatability was assessed for IMD and joint space width (JSW) measured at three different locations.

RESULTS

Approximately 90% of knee images presented excellent quality. Frequencies of nearly perfect radioanatomic alignment (IMD ≤1mm) ranged from 29% to 50%, and satisfactory alignment was found in up to 71% and 76% of the images (IMD ≤1.5mm and ≤1.7mm, respectively). Repeatability analyses yielded the following results: IMD [SD of mean difference=1.08; coefficient of variation (%CV)=54.68%; intraclass correlation coefficient (ICC) (95%CI)=0.59 (0.34-0.77)]; JSW [SD of mean difference=0.34-0.61; %CV=4.48%-9.80%; ICC (95%CI)=0.74 (0.55-0.85)-0.94 (0.87-0.97)]. Adequately reproducible measurements of IMD and JSW were found in 68% and 87% of the images, respectively.

CONCLUSIONS

Despite the difficulty in achieving consistent radioanatomic alignment between subsequent radiographs in terms of IMD, the protocol produced highly repeatable JSW measurements when these were taken at midpoint and 10mm from the medial extremity of the medial tibial plateau. Therefore, measurements of JSW at these locations can be considered adequate for the assessment of knee OA in ELSA-Brasil MSK.

Tibial subchondral bone mineral density: sources of variability and reproducibility

OBJECTIVES

It has been shown that subchondral bone mineral density (sBMD) measurement may be a relevant parameter of osteoarthritis (OA) progression. However, factors implicating the reproducibility and contributing to the variability of the measurement have not been fully described. Thus, the aim of this study was to explore the reproducibility of sBMD by Dual energy X-ray Absorptiometry (DXA) and to further examine its sources of variability.

METHODS

In this study, short-term, intra and inter-observer reproducibility of sBMD was examined on knee images obtained on DXA scans. The influence of software (lumbar spine and forearm modes), knee positioning (flexion or extension), site and size of regions of interest (ROI) and use of rice, on both lateral and medial tibial sBMD, were assessed. Root mean square coefficient of variation (RMS CV) and least significant changes (LSC) were calculated.

RESULTS

The short-term precision of sBMD ranged between 2.24% and 5.12% for RMS CV and between 0.053 and 0.135 g/cm(2) for LSC. Good intra-observer precision was found for knee flexion conditions whatever the software used (RMS CV ranging from 0.43 to 1.41%). The reproducibility was dependant from the ROI size (the ROI including joint space exhibiting better precision results than ROI including solely the subchondral plate). For a constant size of the ROI, the precision results were site-dependant. Inter-observer RMS CV results ranged from 0.59 to 5.01% according to ROI and software used. For the specific task of monitoring medial sBMD in the ROI including solely subchondral plate, forearm flexion condition produced the highest intra-observer and short-term precision (respectively RMS CV: 0.45% and 2.77%; LSC: 0.013 and 0.080 g/cm(2)).

CONCLUSION

Taking account into the excellent precision of the sBMD measurements expressed as RMS CV with the protocol proposed in the present study, clinical application of these measurements might be envisaged.

Assessment of early tibiofemoral joint space width changes after anterior cruciate ligament injury and reconstruction: a matched case-control study

BACKGROUND

Progression of primary knee osteoarthritis (OA) is often quantified by measuring structural alterations of the joint such as those in tibiofemoral joint space width (JSW) over time. Limited information is available regarding changes that occur during the onset and progression of posttraumatic OA (PTOA) that are often associated with anterior cruciate ligament (ACL) injury. Furthermore, there is a paucity of information regarding JSW changes in healthy patients, making JSW interpretation challenging during early PTOA progression.

PURPOSE

To evaluate tibiofemoral JSW after ACL injury, ACL reconstruction, and rehabilitation compared with healthy, matched controls.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 39 ACL-injured patients and 32 matched controls were evaluated. Injured patients were assessed at presurgical baseline and after ACL reconstruction (mean follow-up, 46 months), as were controls. Bilateral, standing, fluoroscopy-assisted, and posterior-anterior metatarsal-phalangeal view knee radiographs were obtained at each visit and JSW was measured.

RESULTS

The JSW differences between knees in control patients were not significantly different and did not change over time. Baseline JSW differences in the ACL group were significantly different than in controls. Three patients (7.9% of total) had an increased JSW difference, and 1 patient (2.6%) had a decreased medial JSW difference. In the lateral compartment, 6 patients (15.8%) had a decreased JSW difference. At follow-up, 2 patients in the ACL group (5%) had a decreased medial JSW difference, and 3 (7.9%) had a significantly increased difference in relation to controls. Lateral compartment analyses revealed 7 (18.4%) patients with a significantly decreased JSW difference and no patients with an increased difference compared with controls.

CONCLUSION

One third of ACL-injured knees underwent significant JSW change soon after injury; consequently, evaluation of within-knee JSW changes over time in ACL-injured patients may not be appropriate with a study based on case-control analysis. The JSWs in the healthy knee of ACL-injured patients do not change over time, allowing this knee to be used as a control for the injured knee. This is important when evaluating the earliest stages of PTOA after ACL injury, when patients are asymptomatic and intervention may be most beneficial.

Reproducibility of computer-assisted joint alignment measurement in OA knee radiographs

OBJECTIVES

(1) To investigate the reproducibility of computer-assisted measurements of knee alignment angle (KA) from digitized radiographs of osteoarthritis (OA) participants requiring total knee arthroplasty (TKA) and (2) to determine whether landmark choice affects the precision of KA measurements on radiographs.

METHODS

Using a custom algorithm, femoral, central, and tibial measurement-guiding rules were interactively placed on digitized posteroanterior fixed-flexion knee radiographs by mouse control and positioned according to different anatomic landmarks. The angle subtended by lines connecting these guiding rules was measured by three readers to assess interobserver, intraobserver and experience-inexperience reproducibility. Test-retest reproducibility was evaluated with duplicate radiographs from a healthy cohort. Reproducibility was assessed using root-mean square coefficients of variation (RMSCV%). The Bland-Altman method was performed on data obtained from varying anatomic landmarks (confidence interval, CI= 95%).

RESULTS

From 16 healthy and 30 TKA participants, reproducibility analyses revealed a high degree of intraobserver (n=38, RMSCV=0.56%), interobserver (n=38, RMSCV=0.72%), test-retest (n=16, RMSCV=0.87%) and experience-inexperience (n=38, RMSCV=0.73%) reproducibility with variances below 1%. Varying the orientation of tibial and femoral rules according to anatomic landmarks produced a difference that exceeded an a priori limit of agreement of -1.11 degrees to +1.67 degrees.

CONCLUSION

Our custom-designed software provides a robust method for measuring KAs within digitized knee radiographs. Although test-retest analyses were only performed in a healthy cohort, we anticipate a similar degree of reproducibility in an OA sample. A standardized set of anatomic landmarks employed for KA measurement is recommended since arbitrary selection of landmarks resulted in imprecise KA measurement even with a computer-assisted technique.