A spine or body movement sensing device 100 comprises a string of sensor segments 10 each comprising an orientation sensor, for example an accelerometer 14, magnetometer 12 or gyroscope 16. Mechanical couplings 50 may provide minimum separation between segments, giving a neutral position from which the couplings may be compressible or extendible, or pivot and rotate, the neutral position corresponding to the patients vertebrae spacing. One segment may be a master segment 20 having a power supply 18, a local physical interface 32 for communication with the other segments via electrical couplings 55 and a wireless interface 34 for communication with a controller 150. Also disclosed are methods of attaching sensor strings to a body； methods of determining orientation using two sensor signals (including determining an initial orientation and subsequent change)； and a sensor configured to determine orientation via magnetometer when stationary and via accelerometer or gyroscope during movement.L'invention concerne un appareil de détection de mouvement de colonne vertébrale. L'appareil de détection de mouvement de colonne vertébrale comprend une chaîne de segments de capteur, chaque segment de capteur de la chaîne étant conçu pour se fixer de manière adjacente à la colonne vertébrale d'un patient. Chaque segment de capteur comprend au moins un capteur pour détecter une orientation du segment de capteur respectif.
