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.