Ossification of the Posterior Longitudinal Ligament (OPLL) of the spine may induce motor impairment due to compressive myelopathy. Despite surgical decompression, some patients have residual motor disturbances; after surgery, there is no available intervention for this population. We propose the use of Hybrid Assistive Limb (HAL) robot to promote gait recovery in OPLL patients after decompression surgery.

Five acute and 7 chronic patients underwent 10 sessions of HAL therapy. Before the first and after the last session, walking performance was evaluated using the 10 meters walk test. To record segmental kinematics, a motion capture system (VICON MX, 100Hz) was used. Data was analyzed regarding the elevation angles described for thigh, shank and foot. Kinematic data from 8 healthy volunteers was used for comparison.

HAL therapy improved the waling performance by increasing the speed and stride length in acute and chronic groups (Fig. 1). Kinematics evaluation showed improvement in plane fitting for acute group (PV3 mean; pre: 0.03±0.01, post: 0.02±0.007. P-value: 0.02) but not for chronic group after HAL therapy. When compared to healthy, tendency of PV3 recovery was observed for acute group only (PV3 mean; healthy: 0.009±0.002. P-values; pre-acute Vs healthy:<0.01; post-acute Vs healthy:<0.01). Comparisons between chronic and healthy did not show significant difference (Fig. 2).

HAL therapy improved the walking performance of acute and chronic patients. Interestingly, improvement of loop planarity was only found for acute patients suggesting gait coordination recovery. Chronic patients may have achieved a functional level of coordination through previous rehabilitation and daily life activities.