Michael M. Stephens and Ronan McKeown
DEFINITION
Revision first metatarsophalangeal joint (MTPJ) arthrodesis is performed for pain or deformity following failed hallux valgus surgery, excisional arthroplasty, of prosthetic arthroplasty, and for nonunion or malunion following primary first MTPJ arthrodesis, when a trial of conservative treatment has been unsuccessful.
As is the case for a primary arthrodesis, many techniques for preparation of the joint exist, all designed to provide good cancellous apposition. If possible, in revision surgery, it is better not to shorten and reduce the remaining bone stock.
Ball-and-socket preparation with reamers should be considered for failed hallux valgus surgery and nonunion of the first MTPJ as a way to achieve cancellous congruency with a large contact surface area. However this may not be possible: e.g., in the case of malunions, flat cuts should be performed.
In cases of failed Silastic (Dow Corning, Midland, MI) arthroplasty, the defect should be curettaged until normal bone is reached. This creates a defect that will require a ballshaped interposition cancellous graft.
After a previous excisional arthroplasty with a large resection of the proximal phalanx, a tricortical interposition graft can be used to try to regain length.
Many techniques exist for achieving fixation of the MTPJ. The use of a low-profile precontoured titanium plate and, when possible, a compression screw achieves a very stable construct, without the need to traverse the interphalangeal (IP) joint with threaded pins,1–3 which can produce postoperative stiffness in that joint. Such a plate must have the facility to give strong stable fixation to the remaining short proximal phalanx and allow fixation of an interposition graft.
ANATOMY
In revision surgery, normal anatomy may be severely disrupted. The first metatarsal length may be lost, the metatarsal head may be avascular, and the proximal phalanx may be short or have poor bone stock.
The aim in revision arthrodesis is to create a painless and solid medial column, of a length that is appropriate to the foot, that provides a stable medial arch and a plantigrade foot that prevents load transfer to the lesser rays.
Complex foot deformities may have additional problems with the alignment of the lesser toes. These should be corrected first, before the final hallux valgus arthrodesis angle is set.
As in primary arthrodesis, the final position of the arthrodesed first MTPJ must allow for heel rise during the late stance phase of gait. Therefore, the tip of the toe should be clear of the weight-bearing surface with the IP joint in full extension. The tip of the hallux also should be able to touch the ground in midstance, simulated at surgery with the ankle at 90 degrees and a flat surface applied to the sole of the foot. In this position, the tip of the toe should be able to touch the flat surface with the IP joint in 45 to 60 degrees of flexion. In addition, a gap of 3 to 5 mm should be left between the first and second toes.
PATHOGENESIS
Failed hallux valgus surgery may result in recurrent deformity, avascular necrosis of the metatarsal head, or pain and stiffness secondary to accelerated degeneration of the first MTPJ.
Failed resection arthroplasty may result in recurrent valgus deformity, a cock-up deformity, or a flail toe4 (FIGS 1 AND 2).
Failed Silastic arthroplasty may result in an aggressive foreign body reaction with bone loss on one or both sides of the joint, depending on whether a singleor double-stemmed implant was used.
Failed primary arthrodesis can lead to a painful deformity and hardware impingement. A fusion that is too straight leads to a painful callus under the condyles of the proximal phalanx; one that is too dorsiflexed leads to a painful callus on the dorsum of the IP joint.
PATIENT HISTORY AND PHYSICAL FINDINGS
A thorough physical examination of the foot and ankle is necessary before a first MTPJ revision arthrodesis is begun.
Any history of cigarette smoking should be documented and the patient cautioned about nonunion.
Peripheral circulation and sensation must be tested.
The age and site of previous scars should be noted so the safest approach may be planned.
The IP joint, MTP joint, and first tarsometatarsal (TMT) joint should be examined as for primary arthrodesis.
FIG 1 • A failed Keller's resection arthroplasty.
FIG 2 • A. AP radiograph following revision arthrodesis with tricortical iliac crest graft for failed excision arthroplasty. B. Lateral radiograph following revision arthrodesis with tricortical iliac.
IMAGING AND OTHER DIAGNOSTIC STUDIES
If infection is suspected, it should be ruled out before surgery. A differential white cell count, C-reactive protein level, and erythrocyte sedimentation rate should be obtained. An isotope bone scan may be helpful, but it can be hot for nonunion or infection.
Weight-bearing anteroposterior (AP) and lateral radiographs should be obtained for preoperative planning. Particular attention should be paid to the extent of bone loss from the proximal phalanx and metatarsal head, where an oblique radiograph may give more information. The severity of any deformity should be noted and any coexisting forefoot pathology identified and addressed at the time of surgery.
If avascular necrosis is suspected, an MRI may be useful as long as the patient has no metallic implants.
NONOPERATIVE MANAGEMENT
Nonoperative management encompasses activity modification, weight reduction, analgesic and anti-inflammatory medication (oral and intra-articular), physical therapy (e.g., tendo Achilles and hamstring stretching), functional foot orthoses, and customized shoes.
Functional foot orthoses may include a stiffened insole with a Morton's extension to limit dorsiflexion of the hallux, a medial arch support, and a metatarsal dome.
Customized shoes may include an extra-deep toe box, bunion pockets, or a stiffened sole with a metatarsal rocker.
SURGICAL MANAGEMENT
Revision arthrodesis of the first MTPJ does not restore normal anatomy or gait pattern. The risks of nonunion, infection, neuroma formation, and vascular complications are greater than for primary arthrodesis. Time to union increases in proportion to the size of interposition graft required (i.e., a larger graft takes longer to become incorporated). The patient should be counseled toward realistic outcomes.
Absolute contraindications to revision first MTPJ fusion include active infection and peripheral vascular disease.
Relative contraindications to first MTPJ fusion include degeneration of the first TMT and IP joints or peripheral neuropathy.
Preoperative Planning
Following a thorough examination to assess circulation, sensation, the first TMTJ, the IP joint, the lesser toes, and the skin (for previous surgical incisions or callus under the metatarsal heads), weight-bearing AP and lateral radiographs of the forefoot should be obtained.
The extent of bone loss should be noted and the patient prepared and draped for harvesting iliac crest bone graft. We prefer to use the ipsilateral crest to limit postoperative disability to one side only.
Any lesser toe deformity should be addressed before performing the arthrodesis so that the hallux may be set at the correct valgus angle to the neighboring toes and painful transfer lesions alleviated. The lesser toes may be clawed or hammered with subluxation or dislocation of the MTPJs. Provision should be made to perform proximal interphalangeal joint arthrodesis, MPTJ capsulotomy, extensor digitorum longus lengthening, plantar condylectomy, or Weil's osteotomies, as required. A Weil's osteotomy of the second metatarsal head should never be performed in isolation: an osteotomy of the third metatarsal head must accompany it to prevent transfer metatarsalgia to the third metatarsal head.
A rheumatology consultation or preoperative anesthetic assessment should be done if necessary.
Positioning
We prefer to position the patient supine with the heels at the end of the operating table. If bone graft is required, a sandbag is placed under the ipsilateral buttock.
Prophylactic intravenous antibiotics are administered at induction of anesthesia. A thigh tourniquet is put in place after the limb has been exsanguinated. The iliac crest and leg are then prepared and draped in a routine manner.
The end of the table is dropped 20 to 30 degrees, and the surgeon sits at the end of the table.
Approach
A dorsal approach incorporating previous dorsal scars is recommended. The tissues should be handled carefully. Selfretaining retractors should be positioned under low tension for short periods of time only, particularly if the hallux is then held in forced plantarflexion. Excessive retraction with bone levers must be avoided.
Because previous surgery may have caused intense scarring of the tissues, when possible, full-thickness flaps are raised off the metatarsus and proximal phalanx. Care should be taken to protect the dorsal cutaneous nerve and extensor hallucis longus and the terminal branch of the deep peroneal nerve in the first web space.
TECHNIQUES
REVISION ARTHRODESIS OF THE FIRST METATARSOPHALANGEAL JOINT USING A DORSAL TITANIUM CONTOURED PLATE (HALLU-S PLATE; NEWDEAL, SAINT PRIEST, FRANCE)
Ideally, a dorsal, slightly curved incision is made just medial to the extensor hallucis longus tendon and lateral to the dorsal cutaneous nerve, extending from the middle of the shaft of the first metatarsal to the interphalangeal joint.
The extensor hallucis longus tendon is retracted laterally.
A capsulotomy is made in the same plane, and the joint exposed.
Any previous metalwork or implants are removed.
A synovectomy is performed, along with excision of any avascular bone.
The medial and lateral soft tissues are released to allow maximum plantarflexion of the proximal phalanx so as to fully expose both surfaces to be arthrodesed.
PREPARATION OF THE DISTAL FIRST METATARSAL AND PROXIMAL PHALANX
Preparation of the surfaces and graft techniques vary according to the nature of revision.
Revision of nonunion of a primary arthrodesis, failed hallux valgus surgery, or failed excision arthroplasty (where there has been minimal resection of the proximal phalanx)
In these cases, where bone graft is not required, the arthrodesis site can be prepared with balland-socket reamers in a fashion similar to that for a primary arthrodesis. Osteophytes are excised, and the proximal phalanx is sized to determine the correct convex reamer. The proximal phalanx is reamed over a 1.6-mm guidewire. A size-matched concave reamer is used to prepare the metatarsal head in a similar manner (TECH FIG 1).
Revision of malunion of primary arthrodesis
These cases are revised because the hallux is either too dorsiflexed or too plantarflexed. A simple closing wedge with flat cuts can be performed with the apex at the original arthrodesis site (TECH FIG 2).
TECH FIG 1 • A. Reaming the articular surface of the proximal phalanx. B. Reaming the articular surface of the metatarsal head.
TECH FIG 2 • Revision of malunion.
COMPLEX REVISION CASES
When the residual deficit in bone stock is such that the first ray is short and defunctioned, then either a tricortical iliac crest bone graft or a ball-shaped cancellous graft is required.
The aim is to arthrodese the hallux in the best functional position. This position is determined as follows.
The geometry of the hallux is assessed by placing a flat surface against the sole of the foot and bringing the ankle to 90 degrees.
In this position, with the IP joint in full extension, the tip of the hallux should lie about 1 cm from the flat surface.
When the IP joint is flexed to 45 to 60 degrees, its tip comes in contact with the plantar surface. There should be a gap of 3 to 5 mm between the hallux and the second toe.
The rotation of the hallux should be neutral so that the arc of rotation of the IP joint is at 90 degrees to the weight-bearing surface.
Revision for failed excision arthroplasty
Bone from the distal first metatarsal is resected back to vascular cancellous bone with an oscillating saw. A flat surface is placed on the sole of the foot. The osteotomy is performed in the coronal plane and in the sagittal plane, at 90 degrees to the flat surface.
Bone from the proximal phalanx is resected back to vascular cancellous bone with an oscillating saw, perpendicular to its long axis (TECH FIG 3).
The hallux is held in an estimated best position. The gap between the flat surfaces of the proximal phalanx and metatarsal head is measured. An appropriately sized tricortical iliac crest bone graft is harvested from the ipsilateral crest in a standard fashion.
Revision for avascular necrosis following hallux valgus surgery
The distal first metatarsal and distal phalanx are prepared as previously described.
A retrograde 1.6-mm K-wire is passed through the proximal phalanx and retrieved distally. The hallux is held in the estimated correct position and the K-wire driven into the remaining metatarsal shaft.
A trough is cut out of the dorsum of each bone using the underlying K-wire as an alignment guide. The dimensions of the trough are measured, and the K-wire is then removed.
TECH FIG 3 • Revision of failed excision arthroplasty.
TECH FIG 4 • Revision for avascular necrosis.
An appropriately sized tricortical graft is harvested and inserted into the trough in each bone. The remaining defect is packed with cancellous graft (TECH FIG 4).
Revision of failed prosthetic arthroplasty
Following curettage to normal bone, a considerable champagne-glass defect usually is present in each bone.
The defects are impaction grafted to create concave surfaces.
The hallux is again held in an estimated best position. A ball-shaped cancellous graft of sufficient size to fill the defect is prepared (TECH FIG 5).
TECH FIG 5 • Revision for silicone foreign body reaction.
POSITIONING OF THE HALLUX
In simple revision cases, the hallux is positioned as for primary arthrodesis. The correct position of the hallux is confirmed by placing a flat surface against the sole of the foot and bringing the ankle to 90 degrees. In this position, with the IP joint in full extension, the tip of the hallux lies about 1 cm from the flat surface. When the IP joint is flexed to 45 to 60 degrees, its tip comes in contact with the plantar surface. This enables the foot to rock at the MTPJ on heel rise.
If a graft is used, it is positioned in the arthrodesis site and the alignment of the hallux is reassessed using a flat surface against the sole of the foot, as described earlier. The interposition graft is trimmed as required to achieve the correct position of the hallux and the whole construct held with temporary K-wires.
FIXATION OF THE ARTHRODESIS
When bone graft is not required, an oblique 2.7-mm compression screw of appropriate length is inserted from distal medial to proximal lateral across the MTPJ before a dorsal titanium precontoured low profile plate is secured.
When an interposition graft is used, it may be necessary to reposition the temporary K-wire fixation to allow positioning of a trial plate. The plate is available in three side-specific sizes (small, medium, and large). In revision arthrodesis the large size usually is required for men, medium for women, and small if no interposition graft is used.
The dorsum of the MTP joint may require feathering down with the oscillating saw to enable a flush fit, or the plate may need slight adjustment. If the hallux length has not been fully restored, then the plate needs to be straightened.
The plate is now secured on the dorsal aspect of the joint with a K-wire and fixed with six to seven 2.7-mm–diameter self-tapping screws. The interposition graft is secured to the plate with one screw (see Fig 2).
If the bone quality is poor and screw purchase is insufficient, 3-mm–diameter rescue screws can be used.
The wound is closed in layers over a drain.
A compression dressing is applied.
POSTOPERATIVE CARE
We prefer to use a compressive dressing and a postoperative stiff-soled shoe to allow early mobilization with careful heel weight bearing only.
Early stretching of the tendo Achilles and range-of-motion exercises of the IP joint are encouraged.
In revision cases, patients are kept non–weight-bearing for 4 weeks and then encouraged to bear weight by heel-walking for 4 weeks. Radiographs at this stage may show consolidation if bone graft has not been used.
At 8 weeks post surgery, a radiograph is obtained. If there is evidence of consolidation, forefoot weight bearing is commenced in the postoperative shoe. Progression to full forefoot loading, assisted by crutches, follows over the next 4 weeks.
Radiographs are taken 12 weeks post surgery. If these confirm consolidation, flat shoes with cushioned or shockabsorbing soles are worn.
The time to union depends on the size of bone graft. Forefoot loading should commence only when there is some evidence of consolidation. Patients should be informed that the entire process can take up to 6 months, particularly if there has been a large defect filled with graft or there has been avascular necrosis.
OUTCOMES
Time to union varies according to the patient's underlying medical condition and smoking habits, and in direct relationship to the size of graft used.
The precontoured low-profile titanium plate used was originally designed to obtain the maximum possible purchase in a shortened proximal phalanx, following a Keller's procedure. In both the metatarsal and phalangeal ends, the three screws are on three different axes, to maximize pull-out strength. Additional holes are available to purchase the central graft. This fixation strength cannot be equalled with a single-axis dorsal plate.
COMPLICATIONS
Infection
IP joint stiffness
Delayed union or nonunion
Extensor hallucis longus tenodesis
Dorsomedial sensory cutaneous nerve injury
REFERENCES
· Mann RA, Thompson FM. Arthrodesis of the first metatarsophalangeal joint for hallux valgus in rheumatoid arthritis. J Bone Joint Surg Am 1984;66A:687–692.
· Flavin R, Stephens MM. Arthrodesis of the 1st metatarsal phalangeal joint using a dorsal titanium contoured plate. Foot Ankle Int 2004; 25:783–787.
· Stephens MM, ed. An Atlas of Foot and Ankle Surgery, ed 2. London: Martin Dunitz, 2001.
· Machacek F, Easley M, Gruber F, et al. Salvage of the failed Keller resection arthroplasty. J Bone Joint Surg Am 2004;86A:1131–1138.