Journal of NeuroEngineering and Rehabilitation

Conclusions In the Introduction, we posed three methodological and three clinical questions regarding the gait temporal and loading symmetry of lower-limb amputees. Based on the results collected on traumatic, K3-K4, transfemoral (mechanical knees and C-leg users) and transtibial patients successfully fit and trained in using their prosthesis, we can answer as follows. The three methodological questions wanted to establish a minimum set of symmetry indexes to study and if there are limitations in their calculations. First , the first peak of the vertical ground reaction force at loading response cannot be clearly identified in all amputees, and the calculation of its index of symmetry was limited to patients with the typical M-Shaped pattern of the ground reaction force. Second , the analysis of temporal symmetry can be limited to stance, leaving out step symmetry. Third , stance, impulse and first peak symmetries should be separately reported. The three clinical questions wanted to establish if “ typical ” levels of temporal and loading symmetry exist and change with the level of amputation and prosthetic components. First, the symmetries of stance, impulse and first peak are all influenced by the level of amputation. In particular, the time spent on the sound side decreases significantly from transfe- moral mechanical knee users, to C-leg users, to transtibial patients. The impulse on the sound side decreases signifi- cantly from mechanical knee users to C-leg and transtibial patients. Transtibial patients have a higher first peak at load- ing response on their sound side, while most transfemoral patients do not. Second , advanced prosthetic component seem to positively influence the temporal and loading sym- metry. In particular, the C-leg in combination with the Vari- flex foot improves stance, impulse symmetry and for about 60% of patients smooths the first peak at loading response. About 20% of C-leg users have a stance asymmetry which is below the level of perceived impaired gait, compared to 0% of mechanical knee users. For transtibial patients, compari- sons of our results with the literature point toward an improvement of all indexes of symmetry, possibly due to the use of energy-storage-and-return feet instead of SACH feet. Third, it is not always true that amputees overload the sound side. Percentagewise, transfemoral amputees tend to overload the sound side with increased impulse, while TT with increased peak GRF. This might be suggestive of two separate mechanisms for the onset of knee osteoarthritis. We think that our results can be exploited in the clinical routine. First , clinicians can use our results to set reason- able targets for rehabilitation. Specifically, they can compare the level of symmetry of a new patient with the ranges provided, and put the patient ’ s performance and advancements during rehabilitation in perspective. Moreover, technical and healthcare professionals might use our findings to compare the effect of different prosthetic components and potentially the effect of dif- ferent rehabilitation programs. Second , it is often re- quired by payers (e.g. insurances, public healthcare services, or patients), to justify the use of advanced prosthetic components. We think that our results sup- port the use of C-leg and energy-storage-and-return feet on K3-K4 traumatic patients: thanks to the improvement in temporal and loading symmetry compared to mechan- ical knees and SACH foot, these components can poten- tially have a positive effect on the asymmetry-related comorbidities analyzed in the Introduction and de- crease social stigma. Further research is required to ex- tend these results to other groups of patients, such as K2 and non-traumatic amputees. Finally , our results might suggest possible strategies to mitigate knee osteoarthritis of the sound side. Pending further re- search, transfemoral amputees might take advantage of prosthetic components with an improved knee-foot co- ordination to specifically tackle stance time asymmetry. Transtibial patients might benefit from improved socket construction that does not limit knee extension, and pros- thetic feet with improved push-off, roll-over shape and range of motion to reduce the first peak at loading response. Abbreviations GRF: Vertical component of the ground reaction force; IMS: Impulse symmetry index; P1S: Symmetry index of the first peak of the ground reaction force; SNS: Stance duration symmetry index; SPS: Step duration symmetry index; TF: Transfemoral amputees; TFC: Transfemoral amputees using a C-leg knee (Ottobock, D); TFM: Transfemoral amputees using a mechanical knee; TT: Transtibial amputees Funding This research was conducted with internal institutional funds of INAIL. The publication cost of this article was funded by the American Orthotic & Prosthetic Association (AOPA). Availability of data and materials All data generated or analysed during this study are included in this published article. About this supplement This article has been published as part of Journal of NeuroEngineering and Rehabilitation Volume 15 Supplement 1, 2018: Advancements in Prosthetics and Orthotics: Selected articles from the Second World Congress hosted by the American Orthotic & Prosthetic Association (AOPA). The full contents of the supplement are available online at https://jneuroengrehab.biomedcentral.com/ articles/supplements/volume-15-supplement-1 . Authors ’ contributions AGC, MR and GV designed the experiment. MR and AGC collected and processed the data. All Authors contributed to data analysis and manuscript preparation. All authors read and approved the final manuscript. Ethics approval and consent to participate The Centro Protesi institutional scientific committee approved the study. Consent for publication Not applicable. Competing interests The authors declare that they have no competing interests. Cutti et al. Journal of NeuroEngineering and Rehabilitation 2018, 15 (Suppl 1):61 Page 39 of 72