Determination of leg geometry by ultrasound

Posttraumatic malalignments are a frequent sequlae of IM nailing of lower e xtremity fractures. Conventional US has proven to be inferior to CT determi nations of tibial or femural length and torsion. A new 3-D US method is pre sented that allows for accurate single step determination of lower extremit y length and torsion without ionizing radiation, a regular US machine with a 5 Mhz linear probe is combined with an US localizer. Reference markers af fixed to the lower-extremity eliminate errors associated with patient posti tion or motion. The 3-D US method was compared against CT (Ulm's method) in the measurement of torsion and length of the tibia and femur in 50 adults and 50 children. In both methods, the maximum difference of the intraindivi dual torsional angles and length measurements was 7 degrees and 7 mm. The m aximum standard deviation for reproducibility in length measurement: was 1. 6 mm and 1.5 degrees for angular torsion. The new 3-D US technique was supe rior to CT in terms of reliabilty and reproducibilty. Clinical advantages o f the 3-D US technique include rapidity, independence from patient motion o r postioning and the-avoidance of ionizing radiation. Indications for 3-D t orsional and length determinations include follow-up evaluation of adult an d pediatric tibial and femoral fractures, pediatric limb and gait evaluatio ns, and osteotomy planning.