Research Focus 4 – Transfer of New Technology Interventions to Improve Functionality
In the largest study to date of civilian limb-threatening lower extremity trauma, the Lower Extremity Assessment Project (LEAP) found significant physical disability among patients who underwent limb salvage as well as those who underwent primary amputation.Limitations included decreased walking speed, deviations from normal gait to include Trendelenburg gait, truncal asymmetry, circumduction gait, knee hyperextension, lack of heel-strike, toe drag, uneven step length and a limp. They also demonstrated difficulties with reciprocal stair climbing, single-leg balance, decreased ankle range of motion and knee flexion strength. The study excluded active duty military service members from their patient population, thereby the conclusions and findings of the study lack generalizability to our military population. In addition, there is a paucity of literature specific to the military population regarding functional outcomes of combat-related limb salvage patients.
Ankle foot orthoses (AFO) are frequently prescribed for patients with ankle dorsiflexion and plantarflexion weakness due to a variety of etiologies from cerebral palsy in children to stroke in adults. In particular, AFOs are used to counteract both ankle plantarflexion and dorsiflexion weakness by providing support to the ankle joint to prevent excessive activation of the opposing muscle groups (ie to counteract large plantarflexion moment in dorsiflexion weakness, and large dorsiflexion moment with plantarflexion weakness). However, conventional rigid AFOs typically consist of a hard plastic mold extending from the metatarsal heads to the proximal leg. These place the ankle in a neutral position and help to prevent excessive plantarflexion during swing phase that may lead to a “steppage gait,” and ensure that the heel contacts the ground at initial strike (first ankle rocker). These AFOs do not provide any assistance with plantarflexion, and cannot contribute to push-off at terminal stance (third ankle rocker).
Therefore, in an effort to provide more plantarflexion power, an “energy-storing AFO” was designed. The proposed 3-year study will be conducted within the Military Performance Lab (MPL) located in the Center for the Intrepid (CFI) at Fort Sam Houston, Texas. A total of 12 individuals who have sustained lower extremity trauma requiring surgical management and continued AFO use will participate in each round of testing. Each participant will be tested while performing a range of physical tasks while wearing each of four AFOs with differing design. A comprehensive biomechanical analysis will be performed to determine if improvements in stair and slope kinematics, kinetics and temporal spatial parameters differ between the AFO devices for military service members with limb salvage.
Despite the continual improvements to prosthetic limbs, significant differences remain when comparing gait and related functionality between amputees and non-amputees. These differences persist largely because prosthetic knee mechanisms to date have been passive and rely on input from the user to power the device through its functions. To offset this problem the PowerKnee 2 (PK-2) prosthetic knee unit holds the potential to reduce some of these difficulties and provide a benefit to both active duty and veteran service members in everyday activities. It is anticipated that the PK-2 may help to mitigate long term degenerative physical changes and preserve function in associated joints and soft tissues, but to date, this device has not been evaluated for patients with hip disarticulations or high bilateral amputations. This unique and relevant population may significantly benefit from new prosthetic evaluations.
Up to 30 participants without injury will be recruited to serve as controls. Thirty participants with traumatic transferomal amputation to one lower extremity and a traumatic injury to their contralateral lower extremity (transfemoral amputation, transtibial amputation, hip disarticuation, or other neuromusculoskeletal injury), who have received care through the Armed Forces Amputee Patient Care Program (AFAPCP) at Walter Reed National Military Medical Center, will participate in this study.
All participants will undergo an initial testing session wearing their current prosthesis. Following the initial testing, subjects will be fit with the PK-2 prosthetic knee unit(s) and begin training to use the device. A physical therapist and prosthetist specially trained in the functionality of the PK-2 will provide continued training to maximize safety and optimize the user’s utility of the PK-2 capabilities.
Testing sessions will include biomechanical analysis (using a motion capture system) of steady state level ground walking, gait initiation and termination, and rising from and returning to a seated position, functional evaluation of ascending and descending slopes of varying degree, and metabolic analysis of walking at self selected and forced walking paces. Subjects will also be asked to complete subscales of the Prosthetic Evaluation Questionnaire (PEQ).