Full-leg Radiographs Research Articles

Preoperative Radiographic Assessment of Limb-length Discrepancy in Total Hip Arthroplasty

Pelvic radiographs are helpful in assessing limb-length discrepancy (LLD) before and after THA but are subject to variation. Different methods are used to determine LLDs. As a pelvic reference, both ischial tuberosities and the teardrops are used, and as a femoral reference, the lesser trochanter and center of the femoral head are used. We validated the different methods for preoperative radiographic measurement of LLDs and evaluated their reliability. LLDs were measured on full-leg radiographs for 52 patients (29 men, 23 women) with osteoarthritis (OA) of the hip and compared with different methods for measuring LLDs on AP radiographs of the pelvis. The true LLD varied from -8.0 to 9.1 mm. When the biischial line was used as a pelvic reference, the LLD measured on AP pelvis radiographs was different from the true LLD. No difference was found when the interteardrop line was used as a pelvic reference. There was substantial interobserver agreement when the lesser trochanter was used as a femoral reference (kappa = 0.66-0.70) and excellent interobserver and intraobserver agreement for all other measurements (kappa = 0.84-0.93). Our data show use of the biischial line as a pelvic reference should be discouraged and the interteardrop line is a better alternative. The center of the femoral head is a more reliable femoral landmark compared with the lesser trochanter.

The association of quadriceps strength with the knee adduction moment in medial knee osteoarthritis

To investigate the relationship between quadriceps strength and the peak knee adduction moment during walking in medial tibiofemoral osteoarthritis (OA), and whether varus malalignment influences this relationship. Maximum isometric quadriceps strength at 60 degrees flexion relative to body mass and the peak knee adduction moment during walking were assessed in 184 community volunteers with medial knee OA. Mechanical knee alignment was determined either directly from full-leg radiograph or extrapolated from anatomic alignment on knee radiograph using regression equations. Pearson's correlation coefficient was used to assess the association between quadriceps strength and peak knee adduction moment. The independent relationship between quadriceps strength and peak knee adduction moment, and the impact of varus malalignment on this relationship, was assessed using multiple regression analyses with and without adjustment for covariates. Quadriceps strength was not significantly associated with peak knee adduction moment (r = 0.14, P = 0.059). Neither quadriceps strength (b = 0.25, P = 0.142) nor the interaction between quadriceps strength and varus malalignment (b = -0.01, P = 0.693) significantly contributed to the variance in peak knee adduction moment. Results were unchanged with the inclusion of covariates. No significant association was observed between quadriceps strength and the peak knee adduction moment, and the severity of varus malalignment did not influence the relationship. Results suggest that clinicians should not be concerned that patients with knee OA and stronger quadriceps are more likely to demonstrate a higher knee adduction moment.

Is there an alternative to the full‐leg radiograph for determining knee joint alignment in osteoarthritis?

To assess the concurrent validity of alternative measures of frontal plane knee alignment, namely the radiographic anatomic axis and 5 clinical measures, in medial compartment knee osteoarthritis (OA) as compared with the mechanical axis on radiograph. Forty individuals (mean +/- SD age 64.7 +/- 9.4 years) with symptomatic medial knee OA participated. Knee alignment was measured according to the following methods: lower-limb mechanical axis on radiograph, lower-limb anatomic axis on radiograph, visual observation, distance between medial knee joint lines or medial malleoli using a caliper, distance between a plumb line and medial knee joint line or malleolus using a caliper, tibial alignment using a gravity inclinometer, and lower-limb alignment using a goniometer. Data were analyzed using Pearson's correlation coefficient or Spearman's rho correlation coefficient and simple linear regression. The anatomic axis best correlated with the mechanical axis (r = 0.88), followed closely by the inclinometer method (r = 0.80). Other clinical measures of alignment that were significantly associated with the mechanical axis were the caliper method, the plumb-line method, and visual observation (r = 0.76, 0.71, and -0.52, respectively). However, the goniometer method failed to correlate. The anatomic axis on radiograph and the inclinometer method appear to be valid alternatives to the mechanical axis on full-leg radiograph for determining frontal plane knee alignment in medial knee OA. These alternative methods of measuring knee alignment may increase the assessment of this parameter by clinicians and researchers alike, given that malalignment is an important indicator of disease progression and treatment outcome.