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.
In cases in which surgeons noted intraoperative transverse or sagittal plane hypermobility after the standard crossed two-screw fixation, they stabilized the intercuneiform joint by inserting a third screw from the medial base of the first metatarsal to the second cuneiform. For primary Lapidus arthrodesis, Sangeorzan and Hansen used two 3.5 mm cortical screws for fixation.3 A 3.5 mm cortical screw crossed the first metatarsocuneiform joint to provide compression whereas the second screw served as a derotational screw, crossing from the first metatarsal base to the second cuneiform.
In a biomechanical study, Cohen, et al., compared load to failure with a dorsal locking plate design versus standard crossed screw fixation. Screw fixation for first tarsometatarsal arthrodesis created a stronger and stiffer construct than did the dorsal H-locking plate.8 For four patients, surgeons used a single 3.5 mm or 4.0 mm positional screw along with a dorsal or dorsomedial four- or five-hole neutralization plate. Plate designs consisted of a standard 1/3 tubular compression plate or a reconstruction plate.
A Guide To Post-Op Care And Contraindications
In our study, 13 patients (76 percent) undergoing revision received immediate post-op bone stimulation. Twelve patients received external bone stimulation while one received internal bone stiumulation. Four patients received no bone stimulation and all of these went on to solid union. While there are various arguments on bone stimulation technology, a subject for another discussion, this modality is a useful adjunct for revision cases. However, one cannot use this as an alternative to meticulous surgical technique.
In regard to postoperative care, all patients wore a short-leg, non-weightbearing cast for six weeks. If early radiographic consolidation occurred at this time, we had the patients progress to a removable walking boot for four more weeks.
Patients demonstrating incomplete radiographic consolidation at six weeks remained non-weightbearing in a short-leg cast for at least four more weeks. At an average of 10 weeks postoperatively, patients advanced to regular supportive shoes with a gradual return to regular activities as tolerated.
Understanding Key Factors That Affect Bone Healing
We utilized statistical analysis to determine whether gender, fixation, bone stimulation and smoking were predictive of or associated with bone healing. Active smoking in the perioperative period was a predictor of nonunion. None of the other variables demonstrated any statistical association.
The adverse effects of cigarette smoking on bone healing are well documented.2,7,9 Almost 40 percent of patients who had failed primary Lapidus procedures, requiring revision for a symptomatic nonunion, were smokers. All three failed revision procedures occurred in patients who were smokers as well. McInnis and Bouche noted a 12 percent symptomatic nonunion rate in 32 feet. Two of the three cases were cigarette smokers.4 Similarly, Coetzee, et al., noted three cases of nonunion (11.5 percent), all of which occurred in smokers.7 They concluded that smoking should be a relative contraindication to the modified Lapidus procedure.
For this reason, we selectively avoid performing primary Lapidus arthrodesis and revision arthrodesis in active smokers at our institution. Patients who do smoke and require a Lapidus arthrodesis should undergo aggressive preoperative counseling and cessation support. The patient needs to be smoke-free for approximately three months before undergoing surgery. From the data in this report, there is further evidence to view active smoking by a patient as a relative contraindication to performing revision surgery.
Compliance with strict, early non-weightbearing postoperatively is essential in achieving successful union. All three cases, which resulted in nonunion, had repeated documentation in chart review of premature weightbearing in the immediate postoperative period despite disciplined counseling. Other authors have also reported higher rates of nonunion due to earlier weightbearing in the postoperative course.3,5,10
With the emergence of newer surgical techniques and implants, there is a relatively low incidence of nonunion after a primary Lapidus arthrodesis. However, despite these technological advances, nonunions do occur and can be very challenging to remedy. In our analysis of 17 patients revised with autogenous bone graft and internal fixation, we were able to demonstrate a favorable rate of union (82 percent).
Noncompliance in the postoperative course and cigarette smoking were both associated with increased rates of nonunion, with the latter proving statistically significant. Strict patient counseling in the preoperative period to support compliance is strongly recommended. Also, one should view active cigarette smoking as a relative contraindication to revision.
Dr. Hamilton is the Director of Research at the San Francisco Bay Area Foot and Ankle Residency Program. He is a Fellow of the American College of Foot and Ankle Surgeons.
Dr. Burks is a Fellow of the American College of Foot and Ankle Surgeons, and is board certified in foot and ankle surgery. Dr. Burks practices in Little Rock, Ark.
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