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One such device, the Intrepid Dynamic Exoskeletal Orthosis (IDEO), was designed to optimize
biomechanics and power after salvage of severely traumatized lower extremities in soldiers [65,66] . A systematic
review of the IDEO device found that it improved agility, power, and speed compared with non-custom
[64]
bracing and brace-less rehabilitation . Dynamic AFOs can potentially change the post-reconstruction
function in pre-morbidly fit patients and provide a rationale for foregoing amputation.

ADVANCEMENTS AND FUTURE DIRECTIONS IN LOWER EXTREMITY PROSTHESIS
Tremendous improvements in the care and rehabilitation of amputee patients have been made in recent
decades. One such advancement is the development of the externally-powered or so-called “bionic” devices.
Activation can be microprocessor-controlled (MPC) or driven by myoelectric inputs, whereas function
is described as either passive or active. All commercially available lower extremity prosthetic joints are
microprocessor-controlled. For these systems, an integrated computer adjusts movement based on real-time
calculations of gait-cycle interpretation. The majority of bionic prostheses function passively by means of
modulating friction through the joint. For instance, MPC knees increase resistance during stance to mimic
eccentric knee extension and decrease resistance during perceived swing to aid toe clearance. MPC knee
components may enhance safety and confidence by rapidly adjusting resistance during perceived falls, and
may decrease reliance on compensatory gait strategies [67-69] .

Myoelectric control systems, which are investigatory for lower extremity prostheses currently, require viable
muscle tissue for electrode placement. Signal noise remains a notable challenge with myoelectric devices,
compounded by that fact that closed chain kinetics may alter the electrode-residuum contact within the
socket. Numerous approaches are being investigated to overcome this, including EMG pattern recognition,
[70]
intramuscular EMG electrodes, and decomposition of EMG signals .
Another limitation of myoelectric devices, especially for lower extremity use, is the unidirectional nature
of control; specifically, these systems lack proprioceptive afferent information critical for reflexive and
volitional control. This issue has been addressed by surgically creating an agonist-antagonist myoneural
interface. This technique involves coaptation of antagonistic lower limb muscle groups within the residual
limb, allowing antagonist stretch receptors to better communicate proprioceptive information to the central
nervous system. Animal models have demonstrated the potential to communicate graded afferent signals
[71]
in a manner similar to native muscle architecture . A subsequent trial of this method in a single human
subject demonstrated objectively improved control over the prosthesis and provided a subjective sense of
[72]
embodiment of the limb .
Notable drawbacks to bionic componentry include increased costs and complexity, as well as the need for
charging. Unreliable durability and increased weight are also problematic with myoelectric upper extremity
componentry. When considering any prosthetic prescription, one must consider the patient’s functional
expectations and goals, in addition to their aptitude for complex technology.

CONCLUSION
Determining whether to pursue amputation or reconstruction of a lower extremity is challenging for
patients and practitioners alike - and is dependent on the patient’s premorbid health and function, functional
goals and preferences in addition to the viability of the limb. The decision to undergo limb reconstruction
or amputation is best made with input from surgeon, physical medicine and rehabilitation specialist, and
patient in order to achieve the best long-term outcomes. Understanding the functional potential that can be
achieved with different levels of amputation and types of and the available prosthetic and orthotic devices
is critical to ensure that patients are well-informed of their options [Table 2]. Recent advances in prosthetic
and orthotic devices have provided a wider range of options to achieve optimal outcomes. Integration of