als PDF - AGA

27. AGA-Kongress 2010 - Wien
V 25
Can we detect partial ruptures of the anterior cruciate ligament with the GNRB ® Arthrometer?
Robert H. 1 , Nouveau S. 2 , Gageot S. 3 , Gagnière B. 4
1 Centre Hospitalier du Nord Mayenne, Mayenne, France, 2 Centre Hospitalier du Nord Mayenne,
Department d'Orthopédie, Mayenne, France, 3 Ecole Supérieure d'Electronique et d'Informatique
ESIEA, Laval, France, 4 Institut de Biostatistique, Rennes, France
Hypothesis: The diagnosis of single bundle (AM or PL bundle) is clinically difficult. We used the
GNRB ® arthrometer preoperatively to record the elasticity curve of the ACL of each knee. Is it possible
to plan the type of repair, partial or complete, according to the collected data?
Material/method: With the GNRB ® the lower limb is placed on a composite thermoformed support
with the knee at 0° rotation, the patellar pressure being recorded. An electric actuator pushes on the
postero-superior part of the calf with a force of up to 250 Newton (N). This force is only exerted in the
absence of hamstring muscle contraction. A linear position transducer records the translation of the
anterior tibial tuberosity. Each ACL has a specific elasticity curve.
50 unilateral ACL ruptures measured preoperatively were operated on by a reconstruction according
to the TLS technique (Semi tendinosus in 4 strands) between January and June 2009. According to
the clinical tests and the arthroscopic findings, a partial or a complete repair was accomplished.
Information obtained on the side-to-side laxity at 134 N (mm) and the side-to-side slope (mm/N) with
the GNRB ® were compared with the surgery undertaken. ROC curves were used for identifying the
most important thresholds to differentiate the partial from the complete ruptures. In the chosen
thresholds, the sensitivity and specificity were estimated. The predictive values of the combination of
both measurements were estimated.
Results: The differential laxity threshold < 3 mm at 134 N allows the preoperative diagnosis of single
bundle rupture with a sensitivity of 85% and a specificity of 80%. The differential slope threshold < 9
mm/N allows the preoperative diagnosis of single bundle rupture with a sensitivity of 85% and a
specificity of 90%.
The convergence of the two measures in consideration of a partial rupture had a predictive value of
87.5%.
Conclusion: The GNRB ® allows to plan a partial repair with a high level of sensitivity and specificity
from side-to-side laxity or the slope of the elasticity curves. The combination of these two tests
(stretched and slope) allows very good predictive values in the case of convergence.
Level of evidence II b
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