Comparative Reproducibility of TELOS™ and GNRB® for Instrumental Measurement of Anterior Tibial Translation in Normal Knees

Orthop Traumatol Surg Res. 2015 May;101(3):301-5. doi: 10.1016/j.otsr.2015.01.007. Epub 2015 Mar 6.


Background: TELOS™ is among the reference tools for the instrumental measurement of anterior tibial translation during the initial work-up and follow-up of patients with injuries to the anterior cruciate ligament (ACL). GRNB(®) is a non-irradiating but recently developed tool for which only limited data are available.

Hypothesis: The GRNB(®) offers better reproducibility than TELOS™ for measuring anterior tibial translation without rotation in normal knees.

Material and methods: We retrospectively evaluated instrumental laxity measurements in normal knees. Data were available for 60 TELOS™ measurements (9kg load) and 57 GNRB(®) measurements (89N and 134N loads). For each instrument, we compared the absolute variation in anterior tibial translation between two measurements performed 6 months apart. For each GNRB(®) measurement, patellar pressure was recorded.

Results: No significant differences were found between mean (± SD) variations in translation between the two instruments. A greater than 2.5mm variation between the two measurements was significantly more common with TELOS™ than with GRNB(®) (P<0.05, Chi(2) test). GRNB(®) translation values did not correlate with patellar pressure.

Discussion: The GNRB(®) device offers greater reproducibility than TELOS™ when used to quantitate anterior tibial translation. The limited sample size may have prevented the detection of a significant difference between mean values. In addition, disadvantages of the TELOS™ include radiation exposure of the patient, operator-dependency of measurements made on the radiographs, and absence of a biofeedback system to limit hamstring contraction. GNRB(®) does have hamstring contraction biofeedback control but uses another parameter, namely, patellar pressure, for which the optimal value is unknown. Quadriceps and hamstring co-contraction induced by excessive patellar pressure may influence anterior tibial translation. The optimal patellar pressure value needs to be determined.

Keywords: Anterior cruciate ligament; Anterior tibial translation; GNRB(®); Laximetry; TELOS™.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Anterior Cruciate Ligament Injuries
  • Arthrometry, Articular* / instrumentation
  • Female
  • Humans
  • Joint Instability / diagnostic imaging*
  • Joint Instability / physiopathology*
  • Knee Joint / diagnostic imaging*
  • Knee Joint / physiology*
  • Male
  • Patella / physiology
  • Pressure
  • Quadriceps Muscle / physiology
  • Radiography
  • Reproducibility of Results
  • Retrospective Studies
  • Rotation
  • Tibia / physiology*
  • Young Adult