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Improving Below Knee Amputation Outcomes with a Vascularized Fibular Graft: A case series.
Benjamin J. Brown, MD.
Georgetown University, Washington, DC, USA.
The below knee amputation (BKA) is performed approximately 100,000 times per year in the U.S., yet there are few evidence based guidelines regarding how a BKA should be performed. Despite being described over 60 years ago, distal tibio-fibular bone bridging (Ertl) has recently become more commonplace with the notion that a more stable bony platform will interface better with a prosthesis. To date, no study has demonstrated improved outcomes as a result of tibio-fibular bone bridging and therefore the Ertl procedure remains somewhat controversial. One study demonstrated an increased complication and re-operation rate in the bone bridge cohort. The purpose of this study was to report our experience with distal tibio-fibular bone bridging using a vascularized fibular bone graft.
We performed an institutional review board-approved, retrospective review of below knee amputations performed by the senior author between 2004 and 2011. Surgical indications, complications and outcomes were recorded. A two-tailed t-Test was performed to compare ambulation rates and revision rates amongst Ertl and non-Ertl subgroups. Additionally, a separate two-tailed t-Test was also performed to compare the subgroup of patients who received bony fixation with a traditional cannulated screw to the subgroup of patients who received bony fixation with a headless compression screw.
294 BKAs were performed on 270 patients, 30 (11%) of which were done with tibio-fibular bone bridging. The mean clinic follow up period among the Ertl subgroup was 11 months (range 1-42 months). The mean clinic follow up period among the non-Ertl subgroup was 17 months (range 23 days-78 months). Ambulation rates among the Ertl and non-Ertl subgroups were 100% (30/30) and 78% (161/207), respectively (p=0.001). We acknowledge the presence of a selection bias as the Ertl procedure was typically performed for the more active patient. The overall rate of operative revision due to any etiology among the Ertl and non-Ertl subgroups was 33% (10/30) and 23% (61/264), respectively (p=0.216).
Of the 15 amputations performed using traditional cannulated screws, 27% (n = 4) required revision for prominent screw heads. Of the 12 amputations performed using the headless positioning and compression screw, 17% (n = 2) required revision for screw related complications but not for prominent screw heads. There was not a statistically significant difference in revision rates for screw related complications between the two different types of screws (p = 0.54).
Our data suggests that tibio-fibular bone bridging with vascularized fibula leads to a significantly higher rate of ambulation without a significantly higher rate of complications. Screw fixation and compression of the vascularized fibular segment with a headless compression screw is an effective and reliable technique to achieve osseous fixation and compression when performing the Ertl amputation osteoplasty. While this case series did not have adequate power to detect a statistically significant reduction in screw related complications between a headless compression screw and traditional cannulated screw, the use of a headless compression screw has absolved all complications surrounding a prominent screw head.
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