title: Mobility of the first tarsometatarsal joint in relation to hallux valgus deformity: anatomical and biomechanical aspects.
abstract: Hypermobility of the first tarsometatarsal (TMT 1) joint is suggested to be an important factor in the cause and progression of hallux valgus deformity. Hypermobility of the TMT 1 joint is tested clinically in the sagittal plane, but an important deformation also exists in the transversal plane: metatarsus primus varus. This in vitro study was undertaken to investigate the relation between the mobility of the TMT 1 joint in these two planes and to investigate the correlation of the mobility with morphological variables. A second aim was to study the possible stabilizing effect of the tibialis anterior muscle, flexor hallucis longus muscle, and peroneus longus muscle on the TMT 1 joint. Nine embalmed human specimens were tested under standardized conditions. A 30-N force was applied to the head of the first metatarsal (MT 1) to pull in either the dorsal or medial direction. To simulate muscle force, 21 N was applied to the three tendons: all seven possible combinations of muscle action were tested in each plane of motion. Angular displacements were measured using 2-dimensional LED video registration. TMT 1 mobility is a relevant factor in MT 1 mobility in the sagittal and transversal planes, the peroneus longus has a stabilizing effect on this joint, and the effect of the flexor hallucis longus on this joint is different in both planes. When considering a Lapidus procedure for surgically correcting a hallux valgus, the mobility of MT 1 in the transversal plane should also be assessed, but so far no objective clinical test in this plane has been described.
authors.affiliation: Department of Orthopaedic Surgery, Leyenburg Hospital, The Hague, The Netherlands.
authors.forename: F W
authors.initials: FW
authors.lastname: Faber
authors.forename: G J
authors.initials: GJ
authors.lastname: Kleinrensink
authors.forename: M W
authors.initials: MW
authors.lastname: Verhoog
authors.forename: A H
authors.initials: AH
authors.lastname: Vijn
authors.forename: C J
authors.initials: CJ
authors.lastname: Snijders
authors.forename: P G
authors.initials: PG
authors.lastname: Mulder
authors.forename: J A
authors.initials: JA
authors.lastname: Verhaar
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D006215:Hallux Valgus / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D066298:In Vitro Techniques; D007593:Joint Instability / Q000503:physiopathology*; D008682:Metatarsal Bones / Q000502:physiology / Q000503:physiopathology; D008684:Metatarsus / Q000502:physiology / Q000503:physiopathology; D009068:Movement; D018482:Muscle, Skeletal / Q000502:physiology / Q000503:physiopathology; D013640:Tarsal Joints / Q000502:physiology / Q000503:physiopathology*