Proximal Fusions

Alastair S.E. Younger, M.D., FRCSC
Vancouver, BC

Paul Lapidus popularized the first tarsometatarsal (TMT) fusion and distal realignment, although he was not the first to describe this operation. The procedure is therefore also known as a Lapidus procedure1.

Surgeons treating hallux valgus must determine precisely where the foot hurts, and then decide on a logical rationale as to why that part of the foot hurts. Most forefoot pain is due to pressure, and if the pressure point can be reduced - the pain will be resolved. Patients with hallux valgus often complain of pain under the second metatarsal head (metatarasalgia), because of loss of weight bearing through the deformed and possibly elevated first ray. The operation chosen must address the second metatarsal head overload. A Mitchell osteotomy may increase the second metatarsal load as it achieves correction at the expense of metatarsal length2.

With hallux valgus, the first ray deformity is centered at the tarsometatarsal joint in three dimensions with potential rotation and translation in all planes. Hyper mobility of the first ray remains a hotly debated topic3-6. However, regardless of the presence of hyper mobility, the first TMT fusion remains the only procedure centered on the axis of deformity, and correcting it in all planes. The distal procedure remains the same regardless of proximal osteotomy or fusion.

Standing radiographs are required for appropriate assessment as the treatment algorithms are based on standing values7. Non-weight bearing views underestimate these values and may cause the surgeon to perform a distal procedure when a proximal one is merited.

My indications for a Lapidus procedure include:
Patients with a severe bunion deformity requiring a proximal procedure defined by an IM angle greater than 15 or hallux valgus angle greater than 30. I do not perform any proximal osteotomies.
Patients with symptoms localized under the second metatarsal head who otherwise would have a distal osteotomy. In these cases an elevated or hyper mobile first ray may not be addressed by a distal procedure, resulting in ongoing symptoms after surgery.

There is debate over the measurement and significance of the distal metatarsal articular angle (DMAA)8-10. The DMAA can prevent the first metatarsal phalanegeal joint from reducing after the proximal procedure and distal release has been performed. If I identify this intraoperatively, I will perform a distal medial closing wedge osteotomy in conjunction to the proximal fusion10.

During the procedure, a gastrocnemius slide is performed first if indicated, then either two or three foot incisions are used (Figure 2). The two lateral incisions are joined into one if a more extensive exposure is required. The proximal incision is centered dorsally over the first tarsometatarsal joint. The joint is exposed through this incision, avoiding damage to the superficial peroneal nerve, the extensor hallucis longus tendon, or the dorsalis pedis artery. The second incision is based in the first web space, through which the lateral release is performed. The medial incision is based over the first metatarsal phalangeal joint at the junction of the plantar and dorsal skin, and is used for excision of the metatarsal head lateral to the saggital groove and medial capsular plication.

Saw cuts should be avoided as they may shorten the first ray. Instead, all cartilage is removed and the subchondral bone penetrated with a drill and osteotome. Care must be taken to completely debride the plantar side of the first TMT joint. As the joint forms part of a semicircle, the first metatarsal can be corrected in position by translation laterally and plantarly. Pronation of the first ray should be corrected at the same time.

To rigidly control the joint in all planes, two lagged 3.5 screws are used for fixation. The first metatarsal must be notched to prevent fracture. Further correction may be achieved by placing a screw transversely between the first and second metatarsal shaft.

Non-union rates with current techniques are around the 5% range11. Butson, using k-wire fixation, reported on 119 procedures with excellent and good results in 92% of cases12.

Sangeorzan and Hansen reported on 40 feet in 32 patients13. Interposition graft was used in some cases to regain length. Seventy-four percent did well, although there was a 13% revision rate. However, these patients seemed to be more severely affected preoperatively.

Myerson reported on 67 feet, with an 8% failure rate14. The procedure is effective at treating previously failed bunion procedures15. The Lapidus procedure is effective at treating adolescent bunions after the growth plates are closed16.

References

  1. G.A. Horton. Tarsometatarsal Arthrodesis for the treatment of hallux valgus. Foot and ankle clinics. 2(4): 685-98, 1997.
  2. S.K. Fokter, J. Podobnik and V. Vengust. Late results of modified Mitchell
  3. F.W. Faber, P.G. Mulder and J.A. Verhaar. Role of first ray hypermobility in the outcome of the Hohmann and the Lapidus procedure. A prospective, randomized trial involving one hundred and one feet. J Bone Joint Surg Am. 86-A(3): 486-95, 2004.
  4. M.S. Myerson and A. Badekas. Hypermobility of the first ray. Foot Ankle Clin. 5(3): 469-84, 2000.
  5. S.T. Hansen, Jr. Hallux valgus surgery. Morton and Lapidus were right! Clin Podiatr Med Surg. 13(3): 347-54, 1996.
  6. B.R. Grebing and M.J. Coughlin. Evaluation of Morton's theory of second metatarsal hypertrophy. J Bone Joint Surg Am. 86-A(7): 1375-86, 2004.
  7. N.A. Abidi and S.F. Conti. The clinical and radiographic anatomy of hallux valgus and surgical algorithm. Foot and ankle clinics. 2(4): 599-625, 1997.
  8. T.D. Chi, J. Davitt, A. Younger, et al. Intra- and inter-observer reliability of the distal metatarsal articular angle in adult hallux valgus. Foot Ankle Int. 23(8): 722-6, 2002.
  9. J.T. Lau and T.R. Daniels. Effect of increasing distal medial closing wedge metatarsal osteotomies on the distal metatarsal articular angle. Foot Ankle Int. 20(12): 771-6, 1999.
  10. M.J. Coughlin and R.E. Carlson. Treatment of hallux valgus with an increased distal metatarsal articular angle: evaluation of double and triple first ray osteotomies. Foot Ankle Int. 20(12): 762-70, 1999.
  11. S. Patel, L.A. Ford, J. Etcheverry, et al. Modified lapidus arthrodesis: rate of nonunion in 227 cases. J Foot Ankle Surg. 43(1): 37-42, 2004.
  12. A.R. Butson. A modification of the Lapidus operation for hallux valgus. J Bone Joint Surg Br. 62(3): 350-2, 1980.
  13. B.J. Sangeorzan and S.T. Hansen, Jr. Modified Lapidus procedure for hallux valgus. Foot Ankle. 9(6): 262-6, 1989.
  14. M. Myerson, S. Allon and W. McGarvey. Metatarsocuneiform arthrodesis for management of hallux valgus and metatarsus primus varus. Foot Ankle. 13(3): 107-15, 1992.
  15. J.C. Coetzee, S.G. Resig, M. Kuskowski, et al. The Lapidus procedure as salvage after failed surgical treatment of hallux valgus. Surgical technique. J Bone Joint Surg Am. 86-A Suppl 1: 30-6, 2004.
  16. D. Grace, R. Delmonte, A.R. Catanzariti, et al. Modified lapidus arthrodesis for adolescent hallux abducto valgus. J Foot Ankle Surg. 38(1): 8-13, 1999.

 

Figure 1 a.
Patient with second metatarsalgia and hallux valgus.

Figure 1b

Postoperative view of the same patient after a Lapidus procedure and distal osteotomy for a raised DMMA.


Figure 2
The two lateral incisions in the three incision technique.


Figure 3
Case of a failed chevron osteotomy revised to a Lapidus procedure. A 1st to 2nd metatarsal screw was used to increase correction.

 

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