Upper limb kinematics after cervical spinal cord injury

While a number of upper limb kinematic studies have been conducted, there is no review actually addressing the key-features of open-chain upper limb movements following cervical spinal cord injury (SCI). The objective of this literature review is to provide a clear understanding of motor control and kinematic changes during open-chain upper limb reaching, reach-to-grasp, overhead movements, and fast elbow flexion movements after tetraplegia. Using data from MEDLINE between 1966 and December 2014, temporal and spatial kinematic measures and when available electromyographic recording were examined. Included were fifteen control case and three series case studies with a total of 164 SCI participants and 131 healthy control participants. SCI participants efficiently performed a broad range of tasks with their upper limb and movements were planned and executed with strong kinematic invariants like movement endpoint accuracy and minimal cost. The review revealed that elbow extension without triceps brachii relies on greater scapulothoracic and glenohumeral movements providing a dynamic coupling between shoulder and elbow. In addition, contrary to normal grasping patterns where grasping is prepared during the transport phase, reaching and grasping are performed successively following SCI. The prolonged transport phase ensures correct hand placement while the grasping relies on wrist extension eliciting either whole hand or lateral grip. One of the primary kinematic characteristics observed after tetraplegia is motor slowing attested by increased movement time. This could be caused by (i) decreased strength, (ii) triceps brachii paralysis which disrupts normal agonist-antagonist co-contractions, (iii) accuracy preservation at movement endpoint, and/or (iv) grasping relying on tenodesis. Another feature is a reduction of maximal superior reaching during overhead movements which could be caused by i) strength deficit in agonist muscles like pectoralis major, ii) strength deficit in proximal synergic muscles responsible for scapulothoracic and glenohumeral joint stability, iii) strength deficit in distal synergic muscles preventing the maintenance of elbow extension by shoulder elbow dynamic coupling, iv) shoulder joint ankyloses, and/or v) shoulder pain. Further studies on open chain movements are required to identify the contribution of each of these factors in order to tailor upper limb rehabilitation programs for SCI individuals.