December 12, 2008

ACHEIVEING THE GOAL OF BELOW KNEE AMPUTATION: AN ARGUMENT FOR STRICT CASE SELECTION

Steven C. Agle, MD, MPH, Michael M. McNally, MD, Sheila K. Kori, William F. Curry, Christopher I. Jones, Frank M. Parker, DO, William M. Bogey, Jr., MD, C. Steven Powell, MD, Michael C. Stoner, MD.
Brody School of Medicine, East Carolina University, Greenville, NC, USA.

OBJECTIVES: Below knee amputation (BKA) is often indicated as a means to improve functional status as compared to above knee amputation (AKA). The aim of this study is to investigate a contemporary series of BKA, and identify factors associated with either revision to AKA or failure to achieve ambulatory status.
METHODS: Retrospective review was undertaken of consecutive patients who underwent a BKA over a 3-year period between 2005 and 2007. Records were systematically reviewed with endpoints defined as conversion to a higher level of amputation and postoperative ambulatory status. Endpoint associated variables were analyzed with univariate and multivariate statistics using a P < 0.05 for significance.
RESULTS: A total of 180 BKA operations were undertaken, with a mean age of 62 ± 0.88 years, the most common indication being non-salvageable tissue loss (Rutherford category 6, 48%, n= 87). Of these 180 cases, 22% (n= 39) required secondary conversion to AKA. Multivariate analysis demonstrated absence of popliteal pulse (OR 5.16, CI 2.37 - 11.24, P< 0.01), and history of cerebral vascular accident (OR 2.58, CI 1.04 - 6.44, P= 0.03) were independent predictors for conversion to an AKA. Of those cases which did not require conversion to AKA (78% of total, n= 141), 71% (n= 100) achieved either assisted or independent ambulatory status. Multivariate correlates of failure to achieve ambulatory status were: preoperative non-ambulation (OR 35.13, CI 6.65 - 185.58, P< 0.01), chronic obstructive pulmonary disease (OR 6.43, CI 1.27 - 32.54, P= 0.02), and female gender (OR 3.84, CI 1.46 - 10.10, P< 0.01).
CONCLUSIONS: Although some patients will heal a BKA in the absence of a palpable popliteal artery pulse, it is still recommended to proceed with an AKA due to the significant risk for conversion. Additionally, because of dismal ambulatory results and conversion rates, patients with significant comorbidities should be cautiously evaluated prior to deciding on the level of amputation. Most importantly, preoperative non-ambulatory status is a contraindication to a BKA.

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