Magnetic tracking: a novel method of assessing anterior cruciate ligament deficiency.
BACKGROUND
The Lachman test is commonly performed as part of the routine assessment of patients with suspected anterior cruciate ligament (ACL) deficiency. A major drawback is its reliance on the clinician's subjective judgement of movement. The aim of this study was to quantify Lachman movement using a magnetic tracking device thereby providing a more accurate objective measure of movement.


METHODS
Ten patients aged 21-51 years were assessed as having unilateral ACL deficiency with conventional clinical tests. These patients were then re-assessed using a Polhemus Fastrak magnetic tracking device.


RESULTS
The mean anterior tibial displacement was 5.6 mm (SD = 2.5) for the normal knees and 10.2 mm (SD = 4.2) for the ACL-deficient knees. This gave an 82% increase in anterior tibial displacement for the ACL deficient knees. This was shown to be highly significant with P = 0.005.


CONCLUSIONS
The magnetic tracking system offers an objective quantification of displacements during the Lachman test. It is convenient, non-invasive and comfortable for the patient and is, therefore, ideally suited for use as an investigative tool.
Kundra
R K
RK
Department of Orthopaedic Surgery, University Hospital Aintree, Liverpool, UK.
Moorehead
J D
JD
Barton-Hanson
N
N
Montgomery
S C
SC
D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D006801:Humans; D007593:Joint Instability / Q000175:diagnosis*; D007718:Knee Injuries / Q000175:diagnosis*; D008280:Magnetics; D008875:Middle Aged; D009068:Movement; D016059:Range of Motion, Articular