CORR Insights®: Do Gait and Functional Parameters Change After Transtibial Amputation Following Attempted Limb Preservation in a Military Population?

Where Are We Now?

Gait analysis studies commonly investigate velocity, cadence, stride length, and gait cycle duration [5]. Although these are parameters that all orthopaedic surgeons understand, many surgeons still find these studies difficult to read; in fairness, some are more clinically relevant than others, and all are performed under controlled conditions that may differ from our patients’ real-world experiences. Even so, these studies are an invaluable tool when comparing prostheses for our patients who have undergone amputations. Comparisons of orthoses and prostheses for parameters like energy storage and return, and whether they can help our patients walk with greater ease and higher pace are especially useful.

Speed generally decreases, and energy costs increase when an amputee ambulates [6]. Energy costs, as frequently measured by maximal oxygen consumption (VO2max), continue to increase incrementally for each higher level of amputation, which poses a challenge for our aging population (particularly those with high BMI) who might undergo transtibial amputations. Most of the decline of VO2max begins at 55 years of age and is the direct result of a loss in muscle mass. A decline in VO2max from a hypothetical 30-year-old man to a 70-year-old man is 18% to 39%; for a hypothetical woman, the decline is 14% to 30% [1]. As long as oxygen demands remain below 50% of VO2max, an individual may walk for hours. Anaerobic metabolism is initiated above 50% of VO2max, and thereafter endurance rapidly decreases. The slower walking speed developed by the amputee keeps the oxygen demand below the 50% VO2max threshold. Their endurance decreases dramatically should they increase speed above this threshold.

The study by Spahn and colleges [4] evaluated a group of young, male military servicemembers both before and after transtibial amputation, and that in this select group of motivated patients, the amputation resulted in decreased pain, considerably increased walking endurance (from 1.1 to 7 miles) and reduced usage of assistive devices for ambulation, and restoration of the ability to run in most of the patients; gait lab parameters, including velocity, cadence, and stride width also improved. Because of the highly selected and fit patient population, these results may not generalize to community-based populations other than perhaps those with Syme amputations, in whom gait, and energy usage is comparable that of individuals without amputations. Even so, translating these key gait parameters to the other populations seems possible with improved prosthetic design.

Where Do We Need To Go?

We know transtibial amputations can lead to abnormal, inefficient gait patterns and increased energy costs, but gaps in our knowledge remain. Some of these questions are quite basic; for example, what kinds of studies—gait studies, energy studies, patient-reported outcomes studies, studies of prosthesis usage, or other designs—are most informative to the clinicians who care for these patients? Which prosthesis and/or joint, and in which population, are the most effective for improving gait and decreasing energy cost? Energy storage and return will increase velocity but still have a different gait pattern compared to an able-bodied person; the real question will be how much was the energy cost of this increased velocity?

The amount of energy a prosthesis stores and returns during the stance phase is directly influenced by the loading methodology and training. In normal gait, the end of stance is the “roll off” not “push off” as often described [2]; the inertia of the body is powering the body forward and the plantar flexors are silent. Recently developed prostheses truly “push off” (that is, provide power) at the end of stance [3]. This is a game-changer for active patients; suddenly the transtibial amputee has a potential advantage over the able-bodied individual if endurance is discounted.

Patient selection or device selection will become more important in the future. The more sophisticated store and return device may not be applicable to the frail, thin, or weak patient with a high BMI. Energy must be put into the device in order to get energy back. This, of course, would be determined during physical therapy where a temporary prosthesis could be provided. The team would then decide which permanent device is best suited for the patient.

How Do We Get There?

Current prostheses have incorporated walking velocity and decreased energy costs into their designs, which benefits the transtibial amputee. Still, healthcare providers will need to work as multidisciplinary teams to truly benefit their patients. Prosthetists should discuss with the orthopaedic surgeon various prosthetic feet options that best suits the patients’ physical abilities. There is no need to purchase an expensive prosthesis for a patient with limited ambulation. Physical therapists should build their patients’ cardiac rehabilitation programs around the type of prosthesis the patient wears. A cardiac rehabilitation program, with perhaps a longer duration, may be necessary to take advantage of the prothesis work system. Some of this “guess work” will eventually be eliminated by a patient entering his or her age, height, weight, amputation level, and cardiac status into a website that subsequently recommends a type of prosthesis and rehabilitation program. We are just beginning to utilize these programs for joint replacement.

There are new gait analyzers currently available that do not require a laboratory but are suitable for orthopaedic offices and physical therapy departments. These relatively inexpensive gait-analysis systems utilize surface electrodes and a portable power pack-recorder that can record data for several days. The unit analyzes gait (similar to the data in this study), activities of daily living, energy expenditure, and posture. Data analysis is included in the print out with additional interpretation available for further scientific investigations. With tools like this, it is feasible that gait analysis could be part of a routine physical therapy evaluation in the future.