The use of an electromagnetic measurement system for anterior tibial displacement during the Lachman test.

摘要

PURPOSE: The purpose of this study was to assess quantitative anterior/posterior values during the Lachman test by an electromagnetic measurement system and to compare data with KT-1000 arthrometric measurements (MEDmetric, San Diego, CA), as well as the measurement of radiologic laxity by dynamic radiographs. METHODS: We used an electromagnetic device to quantitatively evaluate anterior knee displacements. We tested 82 knees in 41 patients (30 isolated anterior cruciate ligament [ACL]-deficient, 11 ACL-reconstructed, and 41 contralateral ACL-intact knees). Anterior displacements during the Lachman test were calculated by the electromagnetic measurement system and fluoroscopic measurement, and anterior displacements were also measured by the KT-1000 arthrometer. Anterior/posterior displacements measured by these methods were compared, and correlations were assessed. RESULTS: In ACL-deficient knees, mean anterior/posterior displacement (+/-SE) was 22.4 +/- 0.8 mm in electromagnetic measurements, 22.0 +/- 0.7 mm in fluoroscopic measurements, and 15.0 +/- 0.6 mm in KT-1000 measurements. In contralateral ACL-intact knees, it was 15.7 +/- 0.6 mm, 15.6 +/- 0.5 mm, and 9.9 +/- 0.4 mm, respectively. In ACL-reconstructed knees, it was 15.7 +/- 0.7 mm, 16.2 +/- 0.8 mm, and 11.2 +/- 0.6 mm, respectively. In all knee conditions, significant differences between fluoroscopic measurements and KT-1000 measurements were detected (P < .01). Significant differences were also detected between electromagnetic measurements and KT-1000 measurements (P < .01). No significant differences were detected between fluoroscopic measurements and electromagnetic measurements. A strong correlation was obtained between KT-1000 measurements and fluoroscopic measurements (r = 0.62, P < .01) and between electromagnetic measurements and KT-1000 measurements (r = 0.64, P < .01). However, the strongest correlation was observed between electromagnetic measurements and fluoroscopic measurements (r = 0.96, P < .01). CONCLUSIONS: An electromagnetic measurement system to test anterior/posterior tibial translation determined that quantification of the Lachman test could be performed as accurately as fluoroscopic measurements. LEVEL OF EVIDENCE: Level II, development of diagnostic criteria on basis of consecutive patients with universally applied reference gold standard.