Several approaches have been used to devise a model of the human tibiofemoral joint for embedment in lower limb musculoskeletal models. However, no study has considered the use of cadaveric 6,6 compliance (or stiffness) matrices to model the tibiofemoral joint under normal or pathological conditions. The aim of this paper is to present a method to determine the compliance matrix of an ex vivo tibiofemoral joint for any given equilibrium pose. Experiments were carried out on a single ex vivo knee, first intact and, then, with the anterior cruciate ligament (ACL) transected. Controlled linear and angular displacements were imposed in single degree-of-freedom (DoF) tests to the specimen, and the resulting forces and moments were measured using an instrumented robotic arm. This was done starting from seven equilibrium poses characterized by the following flexion angles: 0 deg, 15 deg, 30 deg, 45 deg, 60 deg, 75 deg, and 90 deg. A compliance matrix for each of the selected equilibrium poses and for both the intact and ACL-deficient specimen was calculated. The matrix, embedding the experimental load-displacement relationship of the examined DoFs, was calculated using a linear least squares inversion based on a QR decomposition, assuming symmetric and positive-defined matrices. Single compliance matrix terms were in agreement with the literature. Results showed an overall increase of the compliance matrix terms due to the ACL transection (2.6 ratio for rotational terms at full extension) confirming its role in the joint stabilization. Validation experiments were carried out by performing a Lachman test (the tibia is pulled forward) under load control on both the intact and ACL-deficient knee and assessing the difference (error) between measured linear and angular displacements and those estimated using the appropriate compliance matrix. This error increased nonlinearly with respect to the values of the load. In particular, when an incremental posterior-anterior force up to 6N was applied to the tibia of the intact specimen, the errors on the estimated linear and angular displacements were up to 0.6mm and 1.5 deg, while for a force up to 18 N, the errors were 1.5mm and 10.5 deg, respectively. In conclusion, the method used in this study may be a viable alternative to characterize the tibiofemoral load-dependent behavior in several applications.

Lamberto, G., Richard, V., Dumas, R., Valentini, P.p., Pennestri, E., Lu, T., et al. (2016). Modeling the Human Tibiofemoral Joint Using Ex Vivo Determined Compliance Matrices. JOURNAL OF BIOMECHANICAL ENGINEERING, 138(6), 061010 [10.1115/1.4033480].

Modeling the Human Tibiofemoral Joint Using Ex Vivo Determined Compliance Matrices

VALENTINI, PIER PAOLO;PENNESTRI', ETTORE;
2016

Abstract

Several approaches have been used to devise a model of the human tibiofemoral joint for embedment in lower limb musculoskeletal models. However, no study has considered the use of cadaveric 6,6 compliance (or stiffness) matrices to model the tibiofemoral joint under normal or pathological conditions. The aim of this paper is to present a method to determine the compliance matrix of an ex vivo tibiofemoral joint for any given equilibrium pose. Experiments were carried out on a single ex vivo knee, first intact and, then, with the anterior cruciate ligament (ACL) transected. Controlled linear and angular displacements were imposed in single degree-of-freedom (DoF) tests to the specimen, and the resulting forces and moments were measured using an instrumented robotic arm. This was done starting from seven equilibrium poses characterized by the following flexion angles: 0 deg, 15 deg, 30 deg, 45 deg, 60 deg, 75 deg, and 90 deg. A compliance matrix for each of the selected equilibrium poses and for both the intact and ACL-deficient specimen was calculated. The matrix, embedding the experimental load-displacement relationship of the examined DoFs, was calculated using a linear least squares inversion based on a QR decomposition, assuming symmetric and positive-defined matrices. Single compliance matrix terms were in agreement with the literature. Results showed an overall increase of the compliance matrix terms due to the ACL transection (2.6 ratio for rotational terms at full extension) confirming its role in the joint stabilization. Validation experiments were carried out by performing a Lachman test (the tibia is pulled forward) under load control on both the intact and ACL-deficient knee and assessing the difference (error) between measured linear and angular displacements and those estimated using the appropriate compliance matrix. This error increased nonlinearly with respect to the values of the load. In particular, when an incremental posterior-anterior force up to 6N was applied to the tibia of the intact specimen, the errors on the estimated linear and angular displacements were up to 0.6mm and 1.5 deg, while for a force up to 18 N, the errors were 1.5mm and 10.5 deg, respectively. In conclusion, the method used in this study may be a viable alternative to characterize the tibiofemoral load-dependent behavior in several applications.
Pubblicato
Rilevanza internazionale
Articolo
Esperti anonimi
Settore ING-IND/13 - Meccanica Applicata alle Macchine
English
Biomedical Engineering; Physiology (medical)
http://asmedl.aip.org/Biomechanical
Lamberto, G., Richard, V., Dumas, R., Valentini, P.p., Pennestri, E., Lu, T., et al. (2016). Modeling the Human Tibiofemoral Joint Using Ex Vivo Determined Compliance Matrices. JOURNAL OF BIOMECHANICAL ENGINEERING, 138(6), 061010 [10.1115/1.4033480].
Lamberto, G; Richard, V; Dumas, R; Valentini, Pp; Pennestri', E; Lu, T; Camomilla, V; Cappozzo, A
Articolo su rivista
File in questo prodotto:
File Dimensione Formato  
ASME_CompliantKnee.pdf

non disponibili

Licenza: Copyright dell'editore
Dimensione 1.16 MB
Formato Adobe PDF
1.16 MB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2108/155127
Citazioni
  • ???jsp.display-item.citation.pmc??? 1
  • Scopus 3
  • ???jsp.display-item.citation.isi??? 3
social impact