The Effect of Circular External Fixation on Limb Alignment

Abstract

Diagnostic level II.

Methods for Assessing Leg Length Discrepancy

“…This will avoid underestimation of the LLD that can occur with the patient plantarflexing the ankle on the short side and flexing the contralateral knee in an attempt to level the pelvis. Similarly, any lower extremity joint contractures or overlying external fixators can diminish the accuracy of LLD measurement using either of the two imaging techniques [36]. However, there are potential pitfalls with using this radiograph, including the need for special radiographic equipment such as grids, filters, and processors along with the need for long radiographic cassettes that may not be readily available with recent advances in digital imaging and can be difficult to store.…”

“…Despite a magnification of approximately 5%, the measurement of LLD using fulllength standing AP radiographs is very similar in accuracy to the scanogram, especially on the absence of significant mechanical axis deviation [38]. In another study, Sabharwal et al [36] compared the measurements based on full-length standing radiographs (teleoroentgenograms) before and after removal of a circular external fixator. They found the mean absolute difference in the radiographic measurement of limb lengths between the two radiographs to be 20 mm (p \ 0.0001) for the ipsilateral and 20.2 mm (p \ 0.0001) for the contralateral unaffected extremity.…”

Pediatric Deformity Correction Using a Multiaxial Correction Fixator

“…The healing index for those patients lengthened (Groups I and III) was 42 days/ cm, which compares to the literature of approximately 40 to 50 days/cm with a longer healing index for tibial lengthenings than femoral [9,11]. Like all fixators, both ring and monolateral, the fixator can interfere with radiographic evaluation either by directly obscuring the osteotomy site or secondary to patient positioning errors (such as knee flexion), which may lead to errors in angular or length measurements [8]. Care must be taken in accounting for these errors and oblique radiographs may need to be used to better visualize the osteotomy site.…”

Limb Lengthening and Reconstruction Surgery Case Atlas

“…Monthly X-rays are obtained from then on until consolidation is observed on radiographs, at which time the device can then be removed. As with all fixators, it can affect radiographic evaluation by directly obscuring the osteotomy site, which may lead to errors in measurements (Sabharwal et al 2008). One must take account for these errors; oblique radiographs maybe used to better visualize the osteotomy site, location of the CORA, and coexistent valgus deformities of the femur.…”