Calcaneal Autograft: Can It Facilitate Salvage Of A Failed First MPJ Implant?

   Surgical revision of a failed silicone prosthesis in the first metatarsophalangeal joint (MPJ) is a difficult dilemma that many foot and ankle surgeons increasingly encounter. While advocates of silicone and similar implants have alluded to their preliminary benefits, there is a scarcity of literature on how to salvage these failures, especially when they occur in younger, active patients.

   Revision options include implant removal with synovectomy, implant removal with re-insertion of an alternate implant, or bone block distraction arthrodesis.1,2

   To date, only one study (14 patients) has reported functional outcomes of distraction arthrodesis after a failed implant.1 The authors of that study stipulated that this technically demanding procedure provides long-term stability to the hallux, restores weightbearing and allows patients to maintain a propulsive gait.

   Hamilton additionally noted that the bone block distraction arthrodesis remains the most biomechanically sound option for salvage of the first metatarsophalangeal joint.2 This procedure reportedly accomplishes subjective improvement of the patient’s level of pain and walking tolerance. It also facilitates objective restoration of first ray stability, thus alleviating symptoms of lesser metatarsophalangeal joint overload. The procedure also restores great toe alignment and length, and usually enables one to correct lesser digital malalignment after restoring the hallux position.2

   Traditionally, this bone graft has been harvested from the posterior iliac crest as this site tolerates removal of large block graft. However, the logistics of patient positioning, the need for a higher level of anesthesia, possible previous use of the site for spinal fusion, potential donor site irritation and the presence of a thick layer of soft tissue makes this site less desirable.2,3 When the size of the block graft needed is less than 1.0 cm wide and 2.0 cm deep, the surgeon may harvest the bone from the dorsolateral aspect of the calcaneus.3

A Step-By-Step Guide To The Procedure

   Most of the calcaneal bone graft procedures occur with the patient under general anesthesia. Infiltrate a postoperative block consisting of 0.5% marcaine and dexamethasone phosphate 19:1 mixture about the surgical site.

   Ensure the patient is in the supine position with a small sandbag under the ipsilateral hip. Apply a tourniquet at the thigh and provide sterile prep and draping of the foot up to the knee. I prefer to make a dorsal longitudinal incision medial to the extensor hallucis longus and center it over the first MPJ. This usually encompasses an existing scar.4,5 Carry the incision to bone and into the joint.

   Remove the implant and debride the synovitis. Using a combination of a sagittal saw, high-speed burr or curette, resect the sclerotic bone interfaces and eroded medullary canals until you have achieved healthy bleeding bone. One can fill intermedullary defects with contoured allogenic cancellous cubes.

   Remove the calcaneal bone graft through a vertical posterior lateral incision anterior to the tendo-Achilles and directly posterior to the sural nerve and peroneal tendons. One must carefully protect these structures during the procedure. Denude the soft tissue from the dorsal and lateral surfaces of the calcaneus between the Achilles bursa, and the posterior of the subtalar joint.

   Use a sagittal saw or osteotome to cut the outline of the graft. Take care to ensure accuracy with the space between the parallel cuts. Also remember the depth should be no greater than half the width of the calcaneus. Make the inferior transverse cut last. The resulting block graft is approximately 2 cm tall by 1 cm wide. Insert a curved 1 cm osteotome at the midline of the calcaneus from the superior aspect and drive it plantarly to separate the block of bone from its bed. One may insert allogenic cancellous cubes or another bone substitute into the defect to encourage union prior to weightbearing.

   Additionally, surgeons may insert a 7.3 mm screw across the harvest site to discourage a potential postoperative fracture. In most cases, full weightbearing is contraindicated for six to eight weeks.

   Cut and contour the bicortical calcaneal bone graft to fill the defect and restore a plantigrade hallux with normal parabolic length and alignment. When the calcaneal bone graft is in the desired corrected position, insert one 0.062-inch Kirschner wire obliquely from the medial aspect of the metatarsal neck across the graft and into the lateral aspect of the proximal phalanx to stabilize the graft temporarily. The surgeon can later utilize this hole as a guide for a 3.5 mm compression screw if he or she desires.

   However, in most circumstances, a low-profile locking plate is preferrable. Contour one or two small fragment, low-profile locking plates and place the plate(s) dorsally, overlying the midline of the first MPJ. Generally, one would place two to four screws in the metatarsal, one in the graft and two in the proximal phalanx in a polyaxial configuration.

   Often it is necessary to lengthen the extensor hallucis tendon of the first MPJ through a Z-step tendon lengthening and stitch it with a non-absorbable 4-0 suture at the end of the procedure if you see considerable clawing.6 Additionally, one may perform concurrent surgery to the forefoot if desired.

   Surgeons may utilize intraoperative C-arm fluoroscopy prior to closure to reaffirm the position of the hallux and the placement and fixation of the calcaneal bone graft. Compare the restoration of the length of the first metatarsal to that of the lesser metatarsals. Ideally the center of the first and second metatarsal heads should be on the same line. Proceed to close the extensor tendon over the plate and close the remaining layers.

Keys To The Postoperative Protocol

   Postoperatively, have the patient use a modified Jones compression splint for 10 to 14 days. At this time, remove the sutures. One should subsequently ensure non-weightbearing for two weeks. Once you see radiographic consolidation, gradually promote the patient to full weightbearing in a walking boot and finally into regular shoe gear.

   Schedule quarterly follow-up visits with accompanying weightbearing radiographs for the first year postoperatively. Be advised that radiographic healing with complete incorporation of the graft can take up to a year. External bone stimulators are routinely recommended given the high risk of delayed union or nonunion. Researchers have also recommended that physicians routinely give a low molecular weight heparin such as enoxaparin 40 mg (Lovenox, Sanofi Aventis) for four to six weeks in patients who are at a higher risk of deep venous thrombosis.4,6

In Conclusion

   Historically, foot and ankle surgeons have had to rely upon peripheral resources to obtain bone graft to re-establish the length of a failed double-stemmed silicone prosthesis of the first MPJ. The prospect of obtaining a graft from the foot will enable podiatric surgeons, who were previously limited to iliac crest or allogenic graft sources, to perform reconstruction of these potentially disabling deformities with less difficulty and higher rates of union. Surgeons have successfully demonstrated that, in most circumstances, the calcaneus has ample amounts of graft available to obtain proper functional length and a cosmetically pleasing effect.

   Additionally, with the advent of low-profile locking plates, surgeons can achieve rigid internal fixation without hardware irritation or failure. While debate regarding the functionality of an arthrodesis is inevitable, this surgical technique continues to be a viable salvage procedure for foot and ankle surgeons across the country.2

Dr. Seiter is an Associate of the American College of Foot and Ankle Surgeons. He is in a multispecialty practice and serves as Co-Chair of Podiatric Surgery at Sparks Regional Medical Center in Fort Smith, Ark. Dr. Seiter was a previous Reconstructive Surgery Fellow at American Health Network in Indianapolis.

References:

1. Hecht PJ. Arthrodesis of the first metatarsophalangeal joint to salvage failed silicone implant arthroplasty. Foot Ankle Int 1997; 18(7):383-390. 2. Hamilton GA. How to salvage a failed first MPJ implant. Podiatry Today 2005; 18(5):36-42. 3. Hansen ST. Functional Reconstruction of the Foot and Ankle. Lippincott Williams & Wilkins, Philadelphia, 2000, chapter 23, pp. 492-3. 4. Coughlin MJ. Arthrodesis of the first metatarsophalangeal joint with mini-fragment plate fixation. Orthopedics 1990; 13(9):1037-1044. 5. Myerson MS, Schon LC, McGuigan FX, Oznur A. Results of arthrodesis of the hallux metatarsophalangeal joint using bone graft for restoration of length. Foot Ankle Int 2000; 21(4):297-307. 6. Mulier T, Dereymaeker G. Revision of failed Keller arthroplasty with intercalary bone graft. Techniques Foot Ankle Surg 2007; 6(2):130-135.