Is Rocker Bottom Reconstruction A Viable Option For Limb Preservation?

   Although Charcot neuroarthropathy occurs in a small percentage (5 percent) of the diabetic population, the natural disease course is associated with severe morbidity including chronic ulcerations, infections and amputations.1 The medical necessity of limb preservation is well known to all podiatrists. However, the recent advent of rocker bottom reconstruction provides the podiatric surgeon with another tool in the fight for limb preservation.    Those with ulcerations secondary to Charcot foot deformity are part of a complex subset of patients who require a multidisciplinary approach. The physician who intends to treat Charcot ulcerations successfully must have knowledge of podiatric surgery, plastic surgery and infectious disease, not to mention endocrinology, neurology, cardiology and vascular surgery just to name a few. Over the past decade, the focus of treatment has shifted away from prolonged conservative wound care toward surgical reconstruction with plastic surgery closure of ulcerations.    A plethora of plastic surgery techniques have been described in the literature. A partial list includes rotational, advancement, pedicle and free flaps. Although these plastic techniques may initially accomplish wound closure, when they are used in isolation, they fail to address the underlying etiology of the ulceration. The root cause of the Charcot ulceration is increased pressure secondary to osseous deformity and concomitant biomechanical flaws. If one does not address this underlying etiology, a flawlessly executed plastic surgery closure or conservative wound care is doomed to fail. This logic has led to the advent of both osseous and soft tissue Charcot reconstruction.

Key Treatment Considerations

   The profound neuropathy coupled with hyperemia, which is idiopathic in the Charcot patient, plays havoc on the osseous structures of the foot. As the hyperemia washes out the bone, the profound neuropathy allows the patient to ambulate free of pain while the osseous structure of the foot is destroyed.    Eichenholtz described a radiological staging system whereby patients with Charcot could be classified into three stages. The hallmark of the first stage is hyperemia with rapid fragmentation of joints and multiple fractures. The second stage is marked by coalescence of the fragmented osseous structures. In Stage II, the healing process begins and the inflammation starts to subside. Stage III is marked by resolution of inflammation with mature fracture healing. This healing process may result in significant deformity of the affected limb. If this natural disease course can be interrupted, one may minimize catastrophic osseous destruction if not prevent it entirely.2    The most common deformity resulting from Charcot related osseous destruction is a midfoot collapse, which may result in a rocker bottom deformity.3,4 The midfoot ulcerations that occur secondary to the rocker bottom foot are especially difficult to treat. When conservative care fails to provide closure, the foot is at significant risk for infection and subsequent amputation.    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.

What Constitutes Success With Charcot Reconstruction?

   One should make every attempt to treat the rocker bottom foot with conservative care first. If the Charcot foot is braceable (i.e., the foot is suitable for ambulation without cutaneous breakdown), one should consider bracing the treatment of choice. Pinzur reported that 87 of the 147 (59.2 percent) feet treated for midfoot disease achieved long-term closure without surgical intervention.5 When conservative care fails, podiatric clinicians should consider reconstruction.    Keep in mind that midfoot Charcot reconstruction is a salvage procedure. Therefore, we cannot judge reconstruction with the same criteria as an elective midfoot arthrodesis. A growing body of research describes a change in the way we measure the success of Charcot reconstruction.6 Remember, the goal is limb salvage. We are starting with an unstable, non-braceable, rocker bottom, ulcerative foot that has failed conservative care. Under these criteria, the patient has very few treatment options. A midfoot arthrodesis gives the patient the chance to heal a chronic wound while maintaining a functional limb.    Therefore, the goal of reconstruction is to return the patient to his or her previous level of function by giving the patient a functional, braceable foot with intact integument. Using this definition of success, complications such as osteotomy site pseudoarthrosis may be insignificant. If the patient is able to heal the ulceration and return to his or her previous level of function, the Charcot reconstruction is a success.

What The Research Reveals About Midfoot Reconstruction

   The research on midfoot reconstruction over the past several years has focused on internal fixation for midfoot arthrodesis. Unfortunately, success rates with internal fixation have often been unsatisfactory. Although external fixation for Charcot reconstruction is relatively new, recent literature reports exciting success rates. Again it must be stressed that success represents patients who had functional, braceable feet with intact integument.    Cooper reported on the use of Ilizarov external fixation for midfoot arthrodesis. Fourteen patients underwent midfoot arthrodesis with bone graft. At a mean follow-up of 41 months, 100 percent of these patients went on to function at a level equal to the ability they had prior to the Charcot deformity.1 Farber reported 10 of 11 patents who had undergone midfoot reconstruction with external fixation returned to therapeutic footwear at an average of 24 months.7    Although these results are promising, they are still early results. Further research with long-term follow-up is necessary before the rocker bottom reconstruction becomes the definitive treatment for a collapsed Charcot midfoot. Dr. Blume is a Clinical Assistant Professor in the Department of Orthopaedics and Rehabilitation at the Yale School of Medicine. He is also a Fellow of the American College of Foot and Ankle Surgeons, and is the Director of Limb Preservation at the Yale New Haven Hospital in New Haven, Conn. Dr. Key is an Associate of the American College of Foot and Ankle Surgeons. He is in private practice with Affiliated Foot Surgeons and is an Attending Podiatrist at Yale New Haven Hospital, and the Hospital of Saint Raphael in New Haven, Conn. Dr. Neville is a resident in the Department of Orthopedics and Rehabilitation within the Section of Podiatry at Yale New Haven Hospital in New Haven, Conn. Dr. Steinberg is a faculty member of the Department of Surgery at the Georgetown University School of Medicine in Washington, D.C.
 

References:

1. Cooper PS. Application of external fixators for management of Charcot deformities of the foot and ankle. Foot and Ankle Clinics 2002 March;7(1):207-254.
2. Eichenholtz SN. Charcot Joints. Springfield (IL): Charles C. Thomas; 1996.
3. Myerson MS, Henderson MR, Saxby T, et al. Management of the midfoot diabetic neuroarthropathy. Foot and Ankle International. 1994; 15: 233-41.
4. Early JS, Hanson ST. Surgical reconstruction of the diabetic foot: a salvage approach for midfoot collapse. Foot and Ankle International. 1996; 17: 325-30.
5. Pinzur M. Surgical versus accommodative treatment for Charcot arthropathy of the midfoot. Foot Ankle Int. 2004 Aug;25(8):545-9.
6. Papa JS, Myerson MS, Girard P. Salvage with arthrodesis in intractable diabetic neuropathic arthropathy of the foot an ankle. Journal of Bone and Joint Surgery. 1993; 75A:10056-66.
7. Farber DC, Juliano PJ, Cavanagh PR, Ulbrecht J, Caputo G. Single stage correction with external fixation of the ulcerated foot in individuals with Charcot neuroarthropathy. Foot Ankle Int. 2002 Feb;23(2):130-4.