Is Rocker Bottom Reconstruction A Viable Option For Limb Preservation?

Author(s): 
By Scott Neville, DPM, Peter Blume, DPM, and Jonathan Key, DPM

   Although amputations have their place in the treatment of the Charcot foot, reconstruction is an attractive alternative for limb salvage. Rocker bottom feet can be classified into two groups based on the motion available at the midtarsal joint: stable or unstable. Stable forefeet that have failed conservative care may be candidates for exostectomy with plastic surgery closure. As a rule, lateral rocker bottom ulcerations are the result of a stable deformity. In the event that an exostectomy will allow for relief of the deforming forces, one should consider this the treatment of choice.

   One must also address the associated biomechanical flaws if long-term closure is to be successful. The unstable rocker bottom foot will not allow the forefoot to function as a rigid lever during the propulsive phase of gait. The rocker bottom collapse allows excess force to be distributed to the midfoot, leading to progressive midtarsal joint destruction.

   When it comes to ulcerations that result from an unstable forefoot, clinicians will often locate these at the medial midfoot. If one performs a simple exostectomy on this unstable foot, further forefoot collapse will result in reulceration. Although we must evaluate every surgical candidate individually, a reconstructive midfoot osteotomy is often indicated for the unstable rocker bottom foot.

Why Internal Fixation Should Be Avoided With Chronic Midfoot Ulcerations

   Several procedures have been proposed to correct the osseous etiology that causes midfoot ulcerations. Several authors have discussed the use of internal fixation for Charcot reconstruction. However, there are many complications associated with this approach. The severe osteopenia associated with the Charcot disease process makes screw purchase problematic. According to AO principles, poor bone stock is a relative contraindication for the use of internal fixation. This osteopenic bone often leads to internal fixation failure.

   The typical chronic Charcot ulceration that has been present for several months is often colonized with deleterious bacteria. Even meticulous debridement cannot remove all bacterial contaminants. This colonization leads to an increased risk for postoperative infection. This risk is compounded by utilizing internal fixation, which may act as a nidus for infection. Therefore, our contention is that an integument breakdown is a relative contraindication to using internal fixation. This argument is made even stronger by the availability of a viable, if not superior, alternative method of fixation.

Assessing The Benefits Of External Fixation

   External fixation provides several advantages over the previously mentioned options. The Ilizarov fine wire methodology avoids the need for screw thread purchase because the fixation is based on non-threaded fine wires under tension. These tensioned fine wires provide multiple points of fixation oriented in multiple planes. When these wires are bowed prior to tensioning, they also provide compression. External fixation avoids the need for retained hardware, which may be a source of infection.

   Another advantage of external fixation is related to the relative noninvasive nature of the fixation. Since external fixation is done percutaneously, there is no need for excessive dissection. Plastic reconstruction of ulcerations, whether it is flap closure and/or a split thickness skin graft, requires immobilization for proper healing. External fixation acts as a pseudo cast, providing immobilization for a superior wound healing environment. Since there is no need for a cast with external fixation, it becomes possible to visualize and access the plastic surgery closure daily if necessary. Unlike internal fixation, external fixation is accessible at all times. Therefore, the surgeon has the ability to make postoperative adjustments to optimize the fixation.

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