| Author: | Fu, Siu-ngor |
| Title: | Postural disturbance in subjects with multiple ankle sprains : the role of somatosensory and vestibular systems |
| Degree: | Ph.D. |
| Year: | 2003 |
| Subject: | Hong Kong Polytechnic University -- Dissertations Ankle -- Wounds and injuries -- Treatment Sprains -- Treatment Posture disorders Somatosensory evoked potentials Vestibular apparatus |
| Department: | Department of Rehabilitation Sciences |
| Pages: | xvii, 232 leaves : ill. (some col.) ; 30 cm |
| Language: | English |
| Abstract: | Although proprioceptive deficit is postulated as one of the causes of postural instability in stance in basketball players who had sustained multiple ankle sprains, the relationship between the two remains unclear. Bearing in mind the multi-sensory nature of postural control, it is necessary to assess postural control in stance under changing rather than unchanged sensory conditions. In addition, inconsistent findings were reported on reflex muscle responses to platform perturbations in the injured basketball players. If landing is an activity during which most injured players experiences a feeling of instability, there is a strong rationale to re-examine possible changes in reflex muscle response using a drop-and-landing paradigm. It is also worth noting that smooth landing relies on coordinated motor outputs from both proprioceptive and vestibular inputs, in addition to vision. In this connection, damage to the vestibular end-organs may occur as a consequence of high impact shock due to uncoordinated landing from a jump while playing basketball. Postural control in stance and in response to drops could be further affected in the basketball players with defective functioning of two (both vestibular and ankle proprioceptive inputs) rather than one sensory (ankle proprioceptive) input. Thus, a better understanding of the role of the ankle proprioception and its interaction with the vestibular systems in the control of quiet stance under changing sensory conditions and when landing from drops is needed, before a more comprehensive rehabilitation programme could be recommended to basketball players with multiple ankle sprains. This study was a cross-sectional study. The hypotheses were that, in male university basketball players who had a history of bilateral multiple ankle sprains, there was 1) an increase in errors in ankle repositioning, and an increase in body sway in stance, particularly under conditions in which they had to rely more heavily on ankle proprioceptive inputs for balancing. In addition, there was a positive correlation between errors in ankle repositioning and amount of postural sway in stance under different sensory conditions. 2) The lower limb pre-landing electromyography responses was altered and the magnitude of its associated impact force was increased in injured players, when landing from unexpected and self-initiated drops. 3) The presence of semi-circular dysfunction in the injured players could further affect the postural control in stance but not necessarily the response to unexpected drops, when compared with age- and gender matched healthy players. Thirty-nine male basketball players from 7 universities were recruited, and 37 subjects completed all 4 experiments. Twenty of them were healthy subjects, and 19 had experienced bilateral ankle sprains, with the last sprain having occurred an average of 6.0 +- 3.4 months before the tests. Subjects were aged between 19 and 26, and had participated in competition for more than 5 years. Four inter-related studies were conducted at the Hong Kong Polytechnic University and the University of Hong Kong. Experiment 1: Possible deficiency in ankle proprioception was assessed as errors in passive repositioning of the ankle joint. Experiment 2: Postural control was evaluated by measuring body sway with the subject standing on a movable force platform under different visual and support surface conditions. Experiment 3: Sudden and self-initiated drop-evoked responses in the lower limb muscles and its associated impact force on landing were assessed respectively by electromyographic and force platform measurements. Experiment 4: Vestibular function was evaluated by caloric tests using computerized electronystagmography for horizontal semi-circular canal function, and the responses to drops for the otolithic function. Outcome measurements included 4 major batteries of tests: 1) Errors in passive repositioning of the ankle joint at 5o and 10o of ankle plantarflexion, 2) postural sway under 6 sensory conditions using the so-called Sensory Organization Test or SOT. 3) Latencies of the pre-landing electromyography response obtained from the ankle and the hip muscles in response to unexpected and self-initiated drops, together with the co-contraction index of the ankle dorsi- and the plantar-flexor muscles, as well as the peak vertical impact force on landing from unexpected and self-initiated drops, and 4) the total number of subjects with canal paresis in one or both ears, as determined by the caloric test. Results from our study provided concrete evidence that errors in passive joint repositioning of ankle plantarflexion were significantly increased in basketball players who had sustained multiple ankle sprains when compared with healthy players (p<0.05). The averaged percentage increases were respectively 33% and 40% at 5o and 10o of ankle plantarflexion. Furthermore, the equilibrium scores in the SOT were significantly lowered (p<0.05) under conditions in which the control of body sway relied more heavily on the proprioceptive feedback with and without visual inputs (conditions 1 and 2), or predominantly on the vestibular inputs (condition 5). In addition, subjects were able to achieve higher equilibrium scores during stance on a stable platform, when they displayed smaller errors in repositioning of the ankle to 5o of planterflexion in both ankles (p<0.05). The association between the two variables was highest when subjects had to maintain their balance on a stable platform with their eyes closed (condition 2). Under this condition, about 29% of postural sway can be predicted from the total errors in ankle joint repositioning to 5o of ankle planterflexion. When comparing basketball players with and without a history of bilateral multiple ankle sprains, modulation of pre-landing lower limb muscle activity occurred among the injured players with an increase in the associated impact force, on landing from both unexpected and self-initiated drops. Modulation of the pre-landing muscle activity was manifested by an earlier onset of the tibialis anterior EMG response with a delayed onset of the tensor fasia latae EMG response, for controlling ankle, knee and hip movements (P<0.05); also by an increased co-contraction of the ankle dorsi- and plantar-flexors (P=0.001-0.011) in order to stiffen up the injured (ankle) joint in preparation for landing during self-initiated drops. Greater landing impact force was found in the injured players on landing from self-initiated drops with and without visual inputs (p<0.05), as well as from unexpected drops with eyes closed (p<0.05). In addition, about 32% of basketball players had defective canal function at a sub-clinical level. Injured basketball players with defective canal function might feel unstable in stance when sensory inputs from the visual and proprioceptive systems were either reduced or in conflict such that they had to rely more heavily on the vestibular system (conditions 5 and 6 of the SOT). However, their responses to unexpected drops, thought to be mediated by the otolithic receptors were unaffected. The above findings led to 3 main conclusions. 1) There was an increase in errors in ankle repositioning, and an increase in body sway in stance, particularly under conditions in which basketball players with a history of bilateral multiple ankle sprains had to rely more heavily on proprioceptive (ankle) and vestibular inputs for balancing. In addition, a positive correlation existed between errors in passive ankle repositioning to 5o of ankle plantarflexion in both ankles and amount of postural sways in conditions when subjects had to maintain their stance on a stable platform. 2) In the injured players, modulation of pre-landing lower limb muscle activities with an increase in the associated impact force occurred during landing from unexpected and self-initiated drops. 3) About 32% of basketball players had defective canal function at a sub-clinical level. Injured basketball players with defective canal function might feel unstable in stance when sensory inputs from the visual and proprioceptive systems were either reduced or in conflict, such that they had to rely more heavily on the vestibular system. These findings strongly suggested that any rehabilitation programme for subjects with multiple ankle sprains should include both proprioceptive and balance training, and exercises should be targeted at the proper activation of the lower limb muscles on the injured side during functional activities for the basketball players such as landing from jumps. |
| Rights: | All rights reserved |
| Access: | open access |
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