title: Comparative reproducibility of TELOS™ and GNRB® for instrumental measurement of anterior tibial translation in normal knees.
abstract: 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.
  
  
  OBJECTIVE
  The GRNB(®) offers better reproducibility than TELOS™ for measuring anterior tibial translation without rotation in normal knees.
  
  
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Clinique chirurgicale traumatologique et orthopédique, CHU de Nantes, 1, place Alexis-Ricordeau, 44000 Nantes, France. Electronic address: nbouguennec@gmail.com.
authors.forename: N
authors.initials: N
authors.lastname: Bouguennec
authors.affiliation: Service de chirurgie orthopédique, CHR Orléans, 1, rue Porte-Madeleine, 45000 Orléans, France.
authors.forename: G A
authors.initials: GA
authors.lastname: Odri
authors.affiliation: Clinique du sport de Bordeaux-Mérignac, 9, rue Jean-Moulin, 33700 Mérignac, France.
authors.forename: N
authors.initials: N
authors.lastname: Graveleau
authors.affiliation: Clinique du sport de Bordeaux-Mérignac, 9, rue Jean-Moulin, 33700 Mérignac, France.
authors.forename: P
authors.initials: P
authors.lastname: Colombet
mesh_terms: D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D053587:Arthrometry, Articular / Q000295:instrumentation; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000502:physiology*; D008297:Male; D010329:Patella / Q000502:physiology; D011312:Pressure; D052097:Quadriceps Muscle / Q000502:physiology; D011859:Radiography; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012399:Rotation; D013977:Tibia / Q000502:physiology*; D055815:Young Adult
keywords: Anterior cruciate ligament; Anterior tibial translation; GNRB(®); Laximetry; TELOS™