Exploring New Advances In Digital Arthrodesis
Over the years, a multitude of techniques have been described and employed for digital arthrodesis, ranging from arthroplasty and arthrodesis to flexor tendon transfer and lesser digital implants. Each procedure has a place in surgical correction of digital deformities. Digital arthrodesis, in particular, provides permanent and reliable correction of deformities and is considered by the senior author to be a favored technique, especially when it comes to managing digital deformities of a biomechanical etiology.
Two fundamental techniques, the end-to-end arthrodesis and the peg-in-hole arthrodesis, are commonly employed in digital deformity correction. Various modifications to these procedures have been described over the years (see “A Review Of Modifications In Digital Arthrodesis” below).
The end-to-end arthrodesis essentially involves resection of the cartilaginous surfaces of the head of the proximal phalanx and the corresponding base of the middle phalanx. Fixation with a Kirschner wire (K-wire) is commonly employed for a period of five to eight weeks. Surgical correction involves extensive soft tissue dissection about the metatarsophalangeal joint (MPJ) to correct for subluxation or luxation and then crossing the K-wire fixation into the metatarsal segment in some cases. In other cases, fixation to the base of the proximal phalanx has proven to be sufficient and effective.
A peg-in-hole arthrodesis is a more sophisticated and technically more demanding approach to a fusion of the toe. It involves creating a peg or spike and inserting it into the base of the middle phalanx. This creates a secure, stable point of fixation in and of itself.
Unfortunately, using K-wire fixation for the stabilization of either arthrodesis does not maintain or provide any compression to the fusion site. While this is certainly not necessary, it may be desirable when you are treating patients who have a higher risk for bone-healing complications. Fortunately, clinical experience has proven that clinical arthrodesis does not necessarily correlate with radiographic arthrodesis. However, both are certainly desirable.
While the peg-in-hole arthrodesis consistently provides a more reliable and predictable shortening and radiographic fusion as well as clinical arthrodesis, it is a more complex procedure requiring a higher level of surgical proficiency and skill. End-to-end arthrodesis remains the more common technique but clearly has a higher incidence of radiographic nonunion, which may or may not correlate to clinical fusion.
Choosing The Correct Procedure
The selection of the most appropriate procedure for correction of digital deformities is based upon a thorough understanding of the biomechanics and etiology of such deformities. While techniques of resection arthroplasty of the proximal interphalangeal joint (PIPJ) are indicated for static deformities, arthrodesis of the PIPJ is more commonly preferred when an underlying dynamic etiology of the deformity is identified. Potential etiologies include flexor stabilization, flexor substitution and extensor substitution. In addition, varieties of neuromuscular disorders are associated with dynamic imbalance and thus also require a fusion for correction of the deformities.
In some situations, the flexor digitorum longus and/or flexor digitorum brevis tendon transfer techniques may be more beneficial especially in patients with muscle tendon imbalance or when significant compromise of the plantar plate exists. Tendon transfers can be used alone or in conjunction with other techniques of digital arthrodesis. While some patients will benefit from techniques of flexor tendon transfers, others may require transfer of the extensor tendons to the metatarsal bases or lesser tarsus (i.e. Hibbs suspension procedure).
There are situations in which a shortening osteotomy with or without alterations of the sagittal plane alignment is necessary and appropriate for the correction of digital deformities. This is particularly true when one has a structurally elongated second metatarsal segment, which is believed to contribute to the deformity of the second toe in the presence or absence of a concomitant hallux valgus deformity. The need for osteotomy of the third, fourth and fifth metatarsals for the correction of the deformities decreases as one progresses more laterally.