Abstract SFA 2011

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Reliability of the GNRB for measuring anterior knee laxity: comparison with Telos in 114 knees

N LEFEVRE, Y BOHU, JF NAOURI, S HERMAN. Paris

Introdcution:

Clinical diagnosis of anterior cruciate ligament (ACL) tears by the Lachman Test or Pivot shift test are reliable. Nevertheless, the quantitative assessment of the anterior tibial translation (KT-1000 arthrometer or radiologic Telos) is necessary to evaluated each patient. During the past year, we have been using the GNRB system, an alternative anterior knee laxity measurement device. We hypothesize that this knee laxity measurement device is more reliable and reproducible than other currently available arthrometers.
Materiel and methods:
A prospective study has been realized in order to evaluate the reliability and the sensibility of the GNRB measures before arthroscopic reconstruction of the ACL. Between the beginning of 2011 and end of June, 114 patients have been operated for a ACL tear by patellar graft tendon or hamstring graft tendon technique. For each patient, GNRB comparatives measures have been done before the operation. The GNRB was compared to the radiologic telos. Only were included patients with a contralateral healthy knee. All patients had an intra-articular reconstruction either complete (92 cases) or partial (22cases).

Results :
Variance analyses were carried out at 250 N. For all series, the mean difference laxities pre-operative was of 5.9mm +/- 3,7mm for the telos and 4.3mm +/- 2.4mm for the GNRB. When differential laxity threshold value was 5mm for telos, sensitivity was 70% and was 3mm for the GNRB, sensitivity was 84%.
We also analyzed patients in two groups: complete ACL tear (81%) versus partial ACL tear (19%).
The measures for the ACL complete group were 6.8 mm+/- 3.6mm (télos) and 4.7mm +/- 2.4mm (GNRB). When differential laxity threshold in complete ACL tears value was 5mm for telos, sensitivity was 72% and was 3mm for the GNRB, sensitivity was 81%.
The measures for the ACL partial group were 2.7 mm+/- 2.2mm (télos) and 2.5mm +/- 1.7mm (GNRB). When differential laxity threshold value in partial ACL tears was 3mm for telos, sensitivity was 46% and was 1.5 mm for the GNRB, sensitivity was 74%.

Discussion:
The distribution of the obtain values with both systems were quite similar but the dispersion was higher with the telos. The sensitivity of the laximetry measures was significatively higher with the GNRB than with the radiological telos with a lower dispersion for preoperative measures. The GNRB measure is more sensitive for the diagnosis of ACL rupture and it also seems to be helpful with the diagnostic of the partial ACL ruptures.

Conclusion:

These results confirm the reliability of the instrumental measurement of the laxity in the knee (GNRB method), for the complete ruptures of the ACL as well as for the partial ruptures. The GNRB might be used for diagnosis of partial and complete ACL tears and during follow-up of reconstructed or not ACL tears.