title: Intradiscal pressure measurements: A challenge or a routine?
abstract: Intradiscal pressure (IDP) is an essential biomechanical parameter and has been the subject of numerous in vivo and in vitro investigations. Although currently available sensors differ in size and measurement principles, no data exist regarding inter-sensor reliability in measuring IDP. Moreover, although discs of various species vary significantly in size and mechanics, the possible effects of sensor insertion on the IDP have never been investigated. The present in vitro study aimed to address these issues. The synchronized signals of two differently sized pressure transducers (Ø1.33 and Ø0.36 mm) obtained during the measurements in two species (bovine and caprine) and their influence on the measured pressure were compared. First, the discs were subjected to three loading periods, and the pressure was measured simultaneously to assess the inter-sensor reliability. In the second test, the effect of the sensor size was evaluated by alternatingly inserting one transducer into the disc while recording the resulting pressure change with the second transducer. Although both sensors yielded similar pressure values (ICC: consistency: 0.964-0.999; absolute agreement: 0.845-0.996) when used simultaneously, the sensor size was determined to influence the measured pressure during the insertion tests. The magnitude of the effect differed between species; it was insignificant in the bovine specimens but significant in the caprine specimens, with a pressure increase of 0.31-0.64 MPa (median: 0.43 MPa) obtained when the larger sensor was inserted. The results suggest that sensor selection for IDP measurements requires special attention and can be crucial for species with smaller disc sizes.
authors.affiliation: Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Maxim
authors.initials: M
authors.lastname: Bashkuev
authors.affiliation: Department of Orthopedic Surgery, MOVE Research Institute Amsterdam, VU University Medical Center, Netherlands.
authors.forename: Pieter-Paul A
authors.initials: PA
authors.lastname: Vergroesen
authors.affiliation: Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Marcel
authors.initials: M
authors.lastname: Dreischarf
authors.affiliation: Aesculap AG, Research & Development, Tuttlingen, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Schilling
authors.affiliation: Department of Orthopedic Surgery, MOVE Research Institute Amsterdam, VU University Medical Center, Netherlands.
authors.forename: Albert J
authors.initials: AJ
authors.lastname: van der Veen
authors.affiliation: Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Berlin, Germany. Electronic address: hendrik.schmidt@charite.de.
authors.forename: Hendrik
authors.initials: H
authors.lastname: Schmidt
authors.affiliation: Faculty of Human Movement Sciences, MOVE Research Institute Amsterdam, VU University Amsterdam, Netherlands.
authors.forename: Idsart
authors.initials: I
authors.lastname: Kingma
mesh_terms: D000818:Animals; D002417:Cattle; D006041:Goats; D007403:Intervertebral Disc / Q000502:physiology*; D008159:Lumbar Vertebrae / Q000502:physiology*; D011312:Pressure; D015203:Reproducibility of Results; D014160:Transducers, Pressure; D016474:Weight-Bearing / Q000502:physiology*
keywords: In vitro; Intervertebral disc; Intradiscal pressure measurement; Pressure transducers