An Investigation of Pressure Profiles and Wearer Comfort During Walking With a Transtibial Hydrocast Socket.

OBJECTIVE: The aims of the study were to conduct an investigation of the transtibial hydrocast socket interface pressures during walking and to explore potential relationships between pressures experienced and resultant wearer comfort. DESIGN: In this cross-sectional study, pressure data at the limb and hydrocast socket interface during walking were collected from 16 users of hydrocast sockets. The pressures at this interface were described by location, magnitude, and duration for all participants and were compared between the most and least comfortable participants. RESULTS: High pressures were found about the bony prominences of the residual limb, especially the tibial crest of the anterior distal region. Factors identified as potentially causing discomfort (P < 0.1, d > 0.80) were high peak pressures at the anterior proximal region and longer durations of submaximal loading at the lateral proximal region and the anterior and medial distal regions. High pressure variability at the anterior proximal region may also contribute to discomfort (P = 0.106, d = 0.88). CONCLUSIONS: The hydrocast socket interface pressures have been described for a cohort of users. A number of differences were found in the pressure profiles of the most and least comfortable participants. These differences suggest trends between the identified pressure parameters and resultant wearer comfort. Future studies should confirm these exploratory results.

The functional, spatio-temporal and satisfaction outcomes of transtibial amputees with a hydrocast socket following an extended usage period in an under-resourced environment.

BACKGROUND: Transtibial hydrocast sockets have been shown to be a potential alternative to hand-cast patella-tendon bearing sockets, the use of which would have particular benefits in under-resourced environments. However, data concerning wearer outcomes of hard hydrocast sockets (i.e. those without silicone liners), especially over long-term usage periods, is scarce in the literature. RESEARCH QUESTIONS: Are there any changes in wearer functional, spatio-temporal or satisfaction outcomes over a long usage period with a hydrocast socket? And how do the post-usage period outcomes compare with those from the wearers original prostheses? METHODS: In this pre-post interventional study, the clinical outcomes of twenty-one experienced transtibial prostheses users were evaluated using widely-accepted and employed methods to assess wearer functional capacity, mobility, gait and satisfaction. The participants were fit with a hard hydrocast socket and the outcomes after an extensive usage period of 5 months were compared to the pre-usage period data following initial fitting and the data collected from the participants' original prosthetic limb. RESULTS: Significant differences were found in the temporal parameters of gait, all indicating decreased reliance on the intact limb and an increased loading of the prosthetic limb with the post-usage period hydrocast socket compared to both the pre-usage period socket and the participants' original limbs. No differences in the functional capacity, mobility, spatial gait parameters or satisfaction were found between the socket conditions. SIGNIFICANCE: This is the largest study to date of functional, spatio-temporal and satisfaction outcomes of hydrocast sockets following an extended usage period in an under-resourced environment.

Transtibial Prosthetic Socket Shape in a Developing Country: A study to compare initial outcomes in Pressure Cast hydrostatic and Patella Tendon Bearing designs.

This study compared the physical function and comfort level of patients with unilateral transtibial amputation after being fitted with a hand-cast Patella Tendon Bearing (PTB) socket and a pressure-cast (PCAST) hydrocast socket. The latter technique aims to reduce the skill dependency currently required for socket manufacture and fit. The study was conducted at the Vietnamese Training Centre for Orthopaedic Technologies and involved seventeen Vietnamese participants with unilateral transtibial amputation, all of whom were long term users of prosthetics. All participants were fitted with two sockets manufactured using both hand-cast and PCAST techniques with International Committee of the Red Cross components. Walking tests (timed up and go test and six-minute-walk-test), spatio-temporal gait analyses and subjective comfort assessments were completed after a short acclimatisation period with each socket. The participant-preferred socket was also noted. No significant differences were found for the measures of mobility, functional capacity, spatio-temporal gait parameters, gait symmetry, perceived comfort or participant socket preference. The results show the initial patient outcomes are similar when participants are fitted with a hand-cast PTB socket and a PCAST hydrocast sockets. Future work should confirm these findings in a longer trial.

Evaluation of military helmets and roof padding on head injury potential from vertical impacts.

OBJECTIVE: Soldiers in military vehicles subjected to underbelly blasts can sustain traumatic head and neck injuries due to a head impact with the roof. The severity of head and neck trauma can be influenced by the amount of head clearance available to the occupant as well as factors such as wearing a military helmet or the presence of padding on the interior roof. The aim of the current study was to examine the interaction between a Hybrid III headform, the helmet system, and the interior roof of the vehicle under vertical loading. METHODS: Using a head impact machine and a Hybrid III headform, tests were conducted on a rigid steel plate in a number of different configurations and velocities to assess helmet shell and padding performance, to evaluate different vehicle roof padding materials, and to determine the relative injury mitigating contributions of both the helmet and the roof padding. The resultant translational head acceleration was measured and the head injury criterion (HIC) was calculated for each impact. RESULTS: For impacts with a helmeted headform hitting the steel plate only, which represented a common scenario in an underbelly blast event, velocities of ≤6 m/s resulted in HIC values below the FMVSS 201U threshold of 1,000, and a velocity of 7 m/s resulted in HIC values well over the threshold. Roof padding was found to reduce the peak translational head acceleration and the HIC, with rigid IMPAXX foams performing better than semirigid ethylene vinyl acetate (EVA) foam. However, the head injury potential was reduced considerably more by wearing a helmet than by the addition of roof padding. CONCLUSIONS: The results of this study provide initial quantitative findings that provide a better understanding of helmet-roof interactions in vertical impacts and the contributions of the military helmet and roof padding to mitigating head injury potential. Findings from this study will be used to inform further testing with the future aim of developing a new minimum head clearance standard for occupants of light armored vehicles.

Pressure casting technique for transtibial prosthetic socket fit in developing countries.

This study investigated a low-cost and low-skill dependent pressure casting technique (PCAST) to fabricate and fit transtibial (TT) prosthetic sockets in a developing country. Thirteen adult volunteers (average age 47 yr) with unilateral TT amputation participated. After fitting, five participants were lost to follow-up (four rejected the prosthesis and one died). The eight remaining participants used the prosthesis for an average of 167 +/- 1 d and indicated regular use throughout this period. Success was evaluated by measures of satisfaction (Satisfaction with Prosthesis Questionnaire [SATPRO]), physical function, and gait recorded after fitting and following the usage period. SATPRO results showed high levels of satisfaction on both occasions. After the usage period, the timed up-and-go and six-minute walk performances increased by 1.7 +/- 2.0 s and 60 +/- 29 m (p = 0.001), respectively, whereas gait speed, cadence, step and stride length, support base, and percent gait cycle times remained unchanged. The results show that a TT PCAST socket (with some minor modifications) was successfully fitted to eight of the participants (success rate of 62%). It is reasonable to conclude that this technique may assist people with TT amputation in a developing country where there is a lack of trained personnel. Importantly, this technique may reduce TT prosthetic costs and increase fitting opportunity in a developing country.

Engineering a trans-tibial prosthetic socket for the lower limb amputee.

INTRODUCTION: This review addresses the different prosthetic socket designs for trans-tibial amputees, the biomechanics behind the designs and the current state of the field. Of particular focus is the classic patella-tendon bearing (PTB) socket and the more recent sockets manufactured using pressure casting techniques and the theory, biomechanics and clinical implications of the two designs. Methods to examine and compare these designs are also addressed. MATERIALS AND METHODS: Journal papers by various investigators which have clinical significance/impact on the field of trans-tibial socket design were chosen for this review. Articles were chosen over a period of over 50 years to demonstrate the evolution of knowledge. RESULTS: The engineering of the trans-tibial socket has been largely subjected to empirical derivations and biomechanical theory that remains, for the most part, unproven. The fundamental principles of the PTB socket have been widely refuted. Hydrostatic theory based on pressure casting techniques, on the other hand, provides an optimal scenario to produce a more uniform stump/socket interface pressure. CONCLUSION: Preliminary studies indicate the pressure casting technique has the potential to produce comfortable sockets, providing an alternative to the PTB design. Various studies have been attempted to quantitatively compare the 2 types of socket designs. However, further quantitative biomechanical studies are needed to explain the fundamental theory surrounding the pressure cast technique. Methods that could help further understand the pressure cast concept include amputee gait analysis, stump/socket interface pressure measurements, computer aided socket design and finite element modelling techniques.