Evaluation of proprioception in subjects before and after total knee arthroplasty

INTRODUCTION: Proprioception is one of the most significant factors in balance, joint stability, coordination and injury prevention. It includes a wide set of neural input that bring information from peripheral mechanoreceptors, located within joints, muscles and tendons, to central nervous system. Generally, proprioception is defined as the ability to sense position of a joint in the space. Total knee arthroplasty (TKA) is the gold standard procedure to treatments of severe gonarthrosis, which aims to alleviate the pain, restore the locomotor function and increase patient satisfaction. Even if osteoarthritis has already altered proprioception abilities, the TKA procedure can furtherly affect proprioceptors. Some studies demonstrated that TKA slightly improved the kinaesthesia and balance. Other researchers, differently, did not observe any improvement. The aim of this study is to evaluate proprioception and postural control in subject with TKA, before and after the surgery, using Delos Postural Proprioceptive System (DPPS; Delos, Turin, Italy). METHODS: A cohort of 8 subjects (5 women and 3 men) were involved in the study. Subjects were aged 66.5±4.9, had primary knee osteoarthritis, and were scheduled for TKA. DPPS was used to assess proprioception and postural control before and after the surgery. The two tests considered to evaluate postural and proprioceptive control were stabilometric test and static Riva test. The parameters taken into account for these tests were the Stability Index (SI; percentage score where 100% is a theorical task performed with maximum stability), Autonomy (AU; percentage score based on hands support during tasks) and Postural Instability (PI; score in degree based on movement of trunk). RESULTS: The SI measured during the single stance test improved from 56.1%±27.5 to 73.3%±15.7 with opened eyes and decreased from 37.7%±10.2 to 34.5%±13.1 with closed eyes in the operated limb. PI measured during the double stance test increased of 0.07° with opened eyes and decreased of 0.13° with closed eyes. AU improved from 66.6% to 86.6% with open eyes and has maintained almost the same value with closed eyes (from 47.08% to 47.12%). CONCLUSION: In TKA, mechanoceptors of the knee are sacrificed, this should result in a drop of the proprioceptive information with respect to healthy knee, and consequently there is a decreased of balance and increased of risk of falls. The proprioceptive system are more stimulate during instability situation, for example in poorly lighting places or in restricted movement condition. The reduction of pain and the restoration of limb alignment are probably the main reason of the several improvement of SI and AU during open eyes task, whereas the lack or ineffectiveness of the proprioceptive system, could be the cause of failure improvement of closed eyes task too. Double stance task did not show relevant variations between pre and post surgery, due to influences of non-operated limbs and low numbers of subjects.