Fusion of the 1st MTPJ

Johnny T.C. Lau, M.D., FRCSC
Toronto, ON

Patients with severe hallux valgus with or without inflammatory or degenerative arthritis can be successfully treated with 1st MTPJ fusion. Fusion of the 1st MTPJ reliably corrects deformity, and eliminates pain in cases with arthritis. The success of fusion of the 1st MTPJ depends on the approach, preparation of bony surfaces, proper alignment, and stable internal fixation.

Indications

Absolute indications for fusion of the 1st MTPJ are severe hallux valgus associated with degenerative arthritis or rheumatoid arthritis. Severe hallux valgus without arthritis is a relative indication for fusion of the 1st MTPJ since a proximal metatarsal osteotomy can correct the deformity and maintain joint motion.

Approach

The fusion can be performed through a medial or straight dorsal midline. Both approaches provide adequate exposure of the 1st MTPJ for fusion, but the medial approach allows for the exposure of the sesamoids in case excision is required. In some patients with metatarsal-sesamoid arthritis, fusion of the 1st MTPJ alone will not address the pain plantarly, which requires sesamoidectomy.

Preparation of Bony Surfaces

After 1st MTPJ exposure, the osteophytes are removed, and the arthritic joint is identified. The arthritic cartilage is removed until subchondral bone is exposed. The surfaces are prepared with flat cuts or a cup-and-cone configuration. Flat cuts can be made with a small oscillating saw, but once the cuts are made, the position of the fusion is fixed unless the cuts are revised. The cup-and-cone configuration is made using a bur or Marin reamers. This bony preparation provides the greatest contact area, and allows for easy position of the fusion.

Alignment

Alignment of the fusion is the most important factor influencing outcome. Fusions are ideally positioned in 15o of dorsiflexion relative to the floor, 10-20o of valgus, and neutral rotation of the great toe. This allows for smooth toe off during gait, and slows the development of interphalangeal joint (IPJ) arthritis. By correcting the malalignment of the 1st MTPJ, the 1-2 intermetatarsal angle is also corrected.

Internal Fixation

Rigid internal fixation maintains the alignment of the fusion, and compresses the fusion site to promote healing. Appropriate options include: small fragment plate with/without an oblique small fragment screws, or crossed small fragment screws.

Postoperative Protocol

Patients are fitted with a rigid postoperative shoe. Patients are instructed to protect the fusion with the postoperative shoe and weight bearing on the heel for six weeks. If they are unable to comply with this protocol, then they are protected by non-weight bearing for six weeks. Patients are progressed to full weight bearing after six weeks if radiographs demonstrate a solid fusion.

Results

Based on retrospective reviews, the results of successful fusions have been excellent with 77-100% of patients satisfied. The complication rate ranges from 3-33%, and includes: delayed union, nonunion, stress fracture, infection, metatarsalgia, and interphalangeal joint arthritis.

Successful fusion of the 1st MTPJ reliably corrects malalignment, and allows weight transfer to the 1st metatarsal. However, loss of the 1st MTPJ motion can produce IPJ arthritis, which if symptomatic, requires fusion. Further IPJ fusion produces an extremely stiff and unaccommodative medial column of the foot.

Functional limitation following fusion has not been previously reported in the literature. Currently, the literature lacks prospective studies using valid, reliable, and responsive outcome measures, and comparison between different techniques is hindered by the lack of comparable outcome measures.

References

1. Coughlin, M.J.: Arthrodesis of the first metatarsophalangeal joint with mini-fragment plate fixation. Orthopedics, 13(9): 1037-1044, 1990.

2. Coughlin, M.J. and Abdo, R.V.: Arthrodesis of the first metatarsophalangeal joint with Vitallium plate fixation. Foot Ankle Int, 15(1): 18-28, 1994.

3. DeFrino, P.F., Brodsky, J.W., Pollo, F.E., Crenshaw, S.J., and Beischer, A.D.: First metatarsophalangeal arthrodesis: a clinical, pedobarographic and gait analysis study. Foot Ankle Int, 23(6): 496-502, 2002.

4. Johansson, J.E. and Barrington, T.W.: Cone arthrodesis of the first metatarsophalangeal joint. Foot Ankle, 4(5): 244-248, 1984.

5. Mann, R.A. and Katcherian, D.A.: Relationship of metatarsophalangeal joint fusion on the intermetatarsal angle. Foot Ankle, 10(1): 8-11, 1989.

6. Marin, G.A.: Arthrodesis of the metatarsophalangeal joint of the big toe for hallux valgus and hallux rigidus. A new method. Int Surg, 50(2): 175-180, 1968.

7. McKeever, D.C.: Arthrodesis of the first metatarso-phalangeal joint for hallux valgus, hallux rigidus and metatarsus primus varus. J Bone Joint Surg [Am], 34: 129-134, 1952.

8. Mulcahy, D., Daniels, T.R., Lau, J.T., Boyle, E., and Bogoch, E.: Rheumatoid forefoot deformity: a comparison study of 2 functional methods of reconstruction. J Rheumatol, 30(7): 1440-1450, 2003.

9. Wilkinson, J.: Cone arthrodesis of the first metatarsophalangeal joint. Acta Orthop Scand, 49(6): 627-630, 1978.

Figures

laufigure 1alaufigure 1b

Figure 1a and 1b: AP and lateral radiographs of 1st MTPJ fusion fixed with crossed small fragment screws.


laufigure2

Figure 2: AP radiograph of 1st MTPJ fusion fixed with small fragment plate and screw.

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