Essential Insights On Tendon Transfers For Digital Dysfunction
While tendon transfers have traditionally been reserved for flexible digital deformities, these procedures may be effective for semi-rigid and sometimes rigid deformities. Accordingly, this author discusses the initial assessment, reviews potential biomechanical etiologies and offers a step-by-step guide to the modified Girdlestone-Taylor procedure and the modified Hibbs procedure.
Digital deformities are among the most frequent deformities that foot and ankle surgeons see. Toe deformities are common but not always symptomatic. Once symptomatic, the digital deformities may require surgical correction if one has attempted non-operative care and failed.
When it comes to restoration of these deformities, many surgical techniques have been discussed in the literature. In my opinion, arthroplasty and arthrodesis techniques are currently the more commonly utilized procedures for the repair of digital deformities. However, complications such as shortened toes, rotated toes, deviated toes, contracted toes and “sausage toes” have occurred repeatedly following arthroplasties and arthrodesis procedures.
In my experience, these arthroplasties and arthrodesis do not provide as predictable as an outcome and are fraught with more complications than tendon transfers for digital deformities.
How To Differentiate Among Digital Deformities
Over the years, there has been a relaxed depiction among foot and ankle surgeons when it comes to digital deformities. Often surgeons refer to a deformed digit as a “hammertoe,” which can lead to misunderstanding. It is imperative that one uses the appropriate terminology in order to help ensure the proper surgical groundwork.
A mallet toe presents with a flexion contracture at the distal interphalangeal joint. This toe has a normal anatomical position of the proximal interphalangeal joint as well as the metatarsophalangeal joint (MPJ).1
A hammertoe consists of an extended or hyperextended distal interphalangeal joint, a flexion contracture at the proximal interphalangeal joint and mild hyperextension of the MPJ.1
A claw toe entails a flexion contracture at the distal interphalangeal joint and proximal interphalangeal joint along with extension at the metatarsophalangeal joint.1
A deviated toe results from synovitis, a sequela of MPJ instability, which results in a varus or valgus alignment.1 The progressive deviated toe with instability can lead to subluxation and dislocations with a hammertoe deformity.2
A crossover toe typically presents in a varus position at the MPJ as a hammertoe deformity. This typically occurs at the second MPJ and is coupled with a hallux valgus deformity.1
A curly toe deformity, also known as a “cock-up toe,” is typically isolated to the fourth and fifth toes. The toe appears curved but is not angulated in the frontal plane.
A Closer Look At Biomechanical Etiologies
McGlamry described three etiologies for hammertoes: flexor stabilization, flexor substitution and extensor substitution.3
Flexor stabilization typically occurs in a pronated foot and the flexor digitorum longus gains mechanical advantage over the interossei muscles. Hallmark clinical signs include an adductovarus deformity of the fourth and fifth digits.
Flexor substitution typically occurs in a supinated foot in the late stage of gait. This allows for the flexors to gain mechanical advantage over the interossei muscles. In regard to this deformity, it is common to note a weak triceps surae with the deep posterior muscles attempting to accommodate for the weak triceps muscle.
Extensor substitution, sometimes referred to as extensor recruitment, occurs in the swing phase of gait when the long extensors have gained a mechanical advantage over the lumbricali muscles.