Pertinent Insights On Treating Lapidus Nonunions

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By Graham A. Hamilton, DPM

     Nonunion is a well-documented potential complication of the Lapidus arthrodesis. It reportedly occurs anywhere from 3.3 percent to 12 percent of the time, and is a very challenging problem to fix.1-7

     Granted, a strict definition of nonunion and timeline for classifying a nonunion varies from one surgeon to another. However, for the purpose of this discussion, nonunion has both clinical and radiographic definitions. Nonunions involve the failure of bone healing at the fusion site after six months, broken hardware or both. A clinical nonunion is defined as a painful swollen fusion site at the six-month postoperative visit. Failure of bone healing on radiographs is defined as notable lucency or widening, sclerosis, broken hardware or a lack of bridging trabeculation at the fusion site. If broken hardware is not evident but there is notable lucency at the fusion site, one may consider this a nonunion.

     If a patient has a nonunion after a Lapidus arthrodesis, there are different treatment options depending on his or her symptoms. If the patient is asymptomatic with no functional limitations, then no further treatment is required. However, if pain and/or functional impairment are a part of the patient’s life, then revision surgery is necessary. How should the surgeon revise this nonunion in order to obtain a favorable outcome this time around? Strategies for success abound with advocates of internal fixation, external fixation, combination hybrid fixation, allograft techniques, autograft and bone graft substitutes all claiming superiority. So what method does provide the surgeon with successful reproducibility and outcome?

What A Study Revealed About The Lapidus Arthrodesis

     This question has raised a heated debate at foot and ankle conferences. However, many of the touted techniques for revision are at best anecdotal. We conducted a retrospective multicenter review of 17 feet in 15 consecutive patients (mean age, 54.1 years), who underwent revision “bone block” Lapidus arthrodesis for a symptomatic nonunion (Level IV evidence). In all patients but one, we performed the procedure using ipsilateral autogenous bone grafting. All patients had either screw fixation or a combination of screw and plate fixation without any external fixation. We monitored patients for a minimum of six months postoperatively to assess clinical and radiographic union.

     Eighty-two percent of the 17 feet that underwent revision achieved successful union. Three cases demonstrated repeat nonunion. These results supported a favorable revision rate of union using the aforementioned methods.

     Surgeons accessed the nonunion site through the previous incision. For all patients, we removed previous hardware and resected the fibrous nonunion to healthy bleeding bone. The donor graft site involved harvest of a bicortical structural piece of bone from the ipsilateral distal tibia or the superior aspect of the ipsilateral os calcis. Internal fixation varied slightly but we employed only internal fixation for all patients.

     Autogenous bone graft donor site (distal tibia versus calcaneus) did not affect outcome. One patient underwent revision using allograft and had a nonunion. However, this patient failed to adhere to the post-op protocol. The patient continued to smoke despite aggressive counseling.

What You Should Know About Fixation

     In the aforementioned multicenter review, surgeons achieved fixation either with long solid screws or screws and a plate depending on the surgeons’ preference. They used a minimum of two solid screws. In 13 patients (76 percent), surgeons used two solid crossed and stacked, fully-threaded 3.5 mm cortex or 4.0 mm cancellous positional screws. The screws crossed the joint and graft in the sagittal plane, and thereby resist cantilever loads applied to the first metatarsal during the midstance phase of the gait cycle. Orientation of screws in this manner allows one to disperse the force through the length of the screws.

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