Session III - Polytrauma

Functional Outcomes after Lower Extremity Amputations for Trauma: Effects of Amputation Level, Soft Tissue Coverage, and Prosthetic Design

Ellen J. MacKenzie, PhD; Michael J. Bosse, MD; Renan C. Castillo, MS; Douglas G. Smith, MD; and The LEAP Study Group; Center for Injury Research and Policy, The Johns Hopkins University, Bloomberg School of Public Health, Baltimore, Maryland, USA (-NIAMS/NIH Grant)

Purpose: Lower-limb amputations secondary to trauma typically involve young patients without the co-morbidities associated with the nontraumatic amputees. These amputations, however, are often performed in the zone-of-injury, resulting in atypical wound closure, the use of skin grafts or flaps to achieve coverage, and residual limb length less than the ideal. The functional outcomes after amputation are debated. Most surgeons believe that the type and quality of the soft tissue coverage, preservation of the knee joint, residual limb length, and the design of the prosthesis are important factors. We followed and examined a prospectively chosen population of amputees to address these issues with use of four outcome measures: return to work, ability to achieve a walking speed of more than 4 ft per second, a visual pain scale, and the Sickness Impact Profile (SIP), which includes an overall disability score and physical and psychosocial dimensions.

Methods: A prospectively chosen cohort of patients treated at level-I trauma centers by amputation above the ankle within 3 months of injury (N = 161) were followed for this analysis. Detailed information on the injury, amputation level, wound coverage technique, and final stability of the soft tissue coverage was obtained. Complications, including wound breakdown, need for amputation revision, and presence of phantom limb syndrome, were recorded. Participants were followed at 3, 6, 12, and 24 months. Follow-up rates at 12 and 24 months were 86% and 77%, respectively. The goal of the analysis was to compare outcomes among patients treated with amputations below-the-knee (BKA, N = 1 09), through-the-knee (TKA, N =18), and above-the-knee (AKA, N = 34). Multivariate longitudinal regression analysis was used to observe differences over several visits while adjusting for injury severity, treatment variations, and patient characteristics. In addition, a variable was created which described the level of technical sophistication of the patient's prosthetic device as low, medium, or high.

Results: There were no significant differences between AKAs and BKAs in return to work, pain, or the SIP. AKAs were only 30% as likely as BKAs to reach the walking speed threshold, but this difference was not statistically significant (P = 0.1). TKAs had overall SIP scores 40% higher than either BKAs or AKAs (P = 0.05), and physical dimension scores 50% higher (P = 0.01). Psychosocial dimension scores, however, were comparable between all groups, as were return to work rates and pain. The most dramatic difference was in the walking speed test, where TKAs were only 3% as likely as BKAs to achieve the required speed threshold (P = 0.002). Additional functional measures were examined to confirm the walking speed observations, including the ability to walk on a slope and the ability to walk while carrying an object. The results of all these measures were comparable. Surprisingly, there were no differences in outcome resulting from the technical sophistication of the prosthesis.

Discussion: In our population, TKAs report significantly higher levels of disability than BKAs and AKAs, but there are no significant differences between these last two groups. However, it is possible that as AKA patients grow older, their outcome may worsen relative to those of BKA patients. The exact reason why the TKA amputees reported higher disability is not understood, and further investigation and research are needed. Because the data also show that atypical closures, skin grafts, and flaps did not adversely affect outcome, efforts to preserve the knee appear worthwhile. The results also call into question the advisability of fitting patients with the more sophisticated (and expensive) prostheses, given that the low-tech devices appear to yield equivalent outcomes.