Emerging Insights On Fixation For Austin/Chevron Bunionectomies

Author(s): 
Gary M. Lepow, DPM, MS, FACFAS, and Brian D. Lepow, DPM, AACFAS

Step-By-Step Surgical Pearls

The primary indication for an Austin/Chevron bunionectomy is the presence of pain over the medial eminence of the first metatarsal head that is symptomatic while walking or wearing shoes. It is also indicated for patients who also have a mild to moderate deformity with a metatarsal primus adductus angle of 16 degrees or less and no radiographic evidence of metatarsophalangeal arthrosis.

   Create a dorsal medial incision slightly medial to the extensor hallucis longus tendon. Then incise the underlying joint capsule utilizing the indicated capsulotomy depending on the degree of deformity severity. Take care when utilizing a medial “U” shape capsulotomy due to the possibility of overcorrection.

   After resection of the hypertrophied medial eminence, fashion the Austin/Chevron bunionectomy in the metatarsal neck with the use of a saggital saw. The apex of the “V” is distal, usually 1 cm from the articulation.

   Upon completion of the osteotomy and lateral displacement of the metatarsal head, utilize manual compression of the metatarsal head on the shaft in addition to placing a K-wire for the purpose of temporary fixation and stabilization of the osteotomy. Follow this by remodeling all uneven bone surfaces with the use of intraoperative fluoroscopy to confirm appropriate positioning of the osteotomy.

   After achieving a corrected position, utilize a 2.7 mm drill bit to create a pilot hole for the initial point of fixation. The drill bits are laser-etched for ease of use and are provided with 16 mm and 18 mm markings.

   After the utilization of the drill bit, select the corresponding TenFUSE Nail allograft and place it at least two-thirds of the way into the previously created pilot hole. Take caution not to apply excessive bending force to the implant. Once the implant is partially seated, use the bone tamp to fully seat the TenFUSE Nail to the desired depth. Take care to ensure flush placement of the graft at the dorsal surface. Remove the temporary fixation and use a second allograft after redrilling the temporary fixation site. In the situation of “proud” bone on the dorsal surface, utilize a bone cutter and/or burr to shave down the excess graft. It is not recommended to use a cautery on the graft. Finally, utilize intraoperative fluoroscopy for final confirmation of the corrected position.

   Place the patient in a forefoot cast and allow ambulation with the use of a controlled ankle motion (CAM) walker. Encourage first MPJ range of motion exercises on postoperative day one to limit post-op joint stiffness. Change the forefoot cast weekly for wound inspection and postoperative radiographs. The casting typically ends at postoperative week three and the patient utilizes the CAM boot for an additional three weeks.

In Conclusion

There is no argument that the use of rigid internal fixation with metal screws, staples and/or plates has been the gold standard for bone fixation. Having stated this, many foot and ankle surgeons agree anecdotally that due to the more compressible cancellous bone in the distal metaphyseal osteotomy, resorbable fixation may be as successful as metal in the amount of time to healing.

   For over 30 years, the senior author has utilized various absorbable materials for Austin/Chevron bunionectomies. In a review of those cases, we have found no substantial difference in osteotomy healing in patients with resorbable fixation in comparison to those with rigid fixation, given similar variables including age, vascularity, the presence of diabetes and partial immobilization of weightbearing during the first three to six postoperative weeks.

Comments

"There is no argument that the use of rigid internal fixation with metal screws, staples and/or plates has been the gold standard for bone fixation."

Could not agree more.

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