Balancing Digital Arthrodesis With Flexor Tendon Transfers And MPJ Corrections

Hammertoe correction, one of the mainstays of podiatric surgery, is not as simple and straightforward as one would think. A surgeon may schedule a hammertoe surgery and assume an arthroplasty will correct the deformity. The surgeon is thinking this procedure is quick, easy to perform and he or she will be in and out of the operating room in no time.

   Perhaps there is some contracture at the metatarsophalangeal joint (MPJ). The surgeon assumes it will heal well in proper alignment with a K-wire across the joint holding the digit in position with the MPJ. He or she anticipates that the soft tissue structures will heal in a fixed position, thus reducing the contracture.

   Wrong.

   We know now from many years of performing surgical procedures for hammertoe corrections that it is more involved than just a simple arthroplasty (proximal head resection).1 We understand that older techniques usually yielded unsatisfactory results over time. Now let us discuss what we should do to obtain successful hammertoe correction.

   For those who have been in practice long enough, we understand that relying on just a K-wire to maintain alignment is not sufficient unless we are talking about the most mild of cases. Hammertoe surgery does not just involve joint fusions of the lesser toes but also the influential soft tissue structures surrounding the MPJ. These structures include the extensor and flexor tendons, extensor apparatus, MPJ capsule, ligament structures and the metatarsals themselves.1-3

   Although proximal head resection arthroplasty may still have a place for the elderly surgical patient, we have seen over the years that digital fusions provide the greatest long-term success.

Essential Considerations With Hammertoe Surgery

The range of hammertoe deformities includes proximal interphalangeal joint (PIPJ) abnormality involving the PIPJ only, claw toe deformities involving the PIPJ and distal interphalangeal joint (DIPJ), and mallet toe deformities that involve the DIPJ.

   In the majority of PIPJ fusion deformities, there is usually some mallet toe deformity that one should address. Usually, this deformity is positional and one can solve this with soft tissue corrections. Flexor tendon transfer procedures remove this deforming force at the DIPJ.

   However, at times, there are structural deformities that surgeons should address. There are many types of deformities involving the digit and metatarsophalangeal joint. These include predislocation syndrome, crossover deformities with secondary ligament pathology, plantar plate instability, long second metatarsal and neurological entities such as Charcot-Marie-Tooth disease.2

   The main concern for surgical correction is to maintain metatarsophalangeal joint functionality while maintaining digital purchase as opposed to an unappealing, corrected straight toe with no contact of the weightbearing surface and dorsal migration on the metatarsal head. This is a complex problem in that hammertoe surgery involves capsular structures, tendon components and bone abnormalities.

   With digital surgery, one must always be aware of the problems of prolonged swelling, possible deviations, excessively straight toes, lack of ground purchase and an unusual feeling of tightness after tendon transfer.1 Understanding these issues will help reduce the chance of problems. Communication with your patient concerning these issues will make for a more aware and happier patient.

   The extensor tendon and capsular structures are usually not the main cause of hammertoe deformities. One will see this pathology through the flexor tendon apparatus along with plantar plate pathology.2 Therefore, those surgeons who perform just extensor capsular release or extensor tendon lengthening fixed with a K-wire usually will not have corrected the problem long-term at the MPJ. Eventually, there will be a less than satisfactory result and an unhappy patient.

   The second toe usually exhibits the greatest pathology.3 The third toe deformity may not be as significant as the second toe due to lack of influence from the hallux. The fourth toe usually exhibits a distal varus rotation. Arthrodesis and flexor tendon transfers usually accompany correction of the second and third toes. The second digit has associated pathological forces, including long second metatarsals and associated hallux valgus deformity, which contribute to transverse and sagittal plane changes. Very often, associated bunion surgery will help provide the needed space for correct digital positioning.1 Do not hesitate to discuss bunion correction with patients as it may pertain to the overall success of hammertoe corrections.

   The benefits of flexor tendon transfers with arthrodesis include maintaining correction and increasing stability of the MPJ components. This increased stability of the MPJ components assists in plantar plate repair, correction of the transverse and sagittal plane deformities, maintaining toe purchase and eliminating the positional deforming force in mallet toe deformities.4

A Guide To The Slavitt Surgical Classification For MPJ Pathology With Digital Arthrodesis

Accordingly, I would like to present a new classification for determining the appropriate surgical procedure for hammertoe correction, which involves balancing of the total digit in combination with the MPJ structures.2 The main component of this new classification is to determine the amount of capsular intervention, flexor tendon transfer position and the need for associated metatarsal osteotomy.4

Slavitt Type I — Mild Or No MPJ Pathology
Minimal capsular release
Tendon crossover at the distal segment

Slavitt Type II — Advanced MPJ Pathology
Involved capsular work
Tendon crossover at the proximal segment

Slavitt Type III — Severe MPJ Pathology/Dorsal Dislocation
Involved capsular work
Tendon crossover at the proximal segment
Tightening of medial or lateral capsule
Metatarsal osteotomy

A Step-By-Step Guide To Second Toe PIPJ Fusion With A Flexor Tendon Transfer

Once you have determined the type of classification with the corresponding surgical procedure, there is a surgical sequence that one should follow.

   In the following example, I performed a digital arthrodesis with the Digital Compression Screw (BioPro). Slightly altered sequences may be necessary if one uses alternative fixation devices.

   Begin the skin incision proximal to the head of the second metatarsal and progress distally just past the PIPJ. It is advisable to incorporate a slightly curved or lazy S incision across the MPJ to avoid the possibility of skin contracture and avoid adding unwanted deforming forces to the proximal phalanx. Identify the PIPJ and transect and reflect the extensor tendon proximally all the way to the MPJ capsule. Incise the collateral ligaments at the head of the proximal phalanx.

   In the case of fixation with the Digital Compression Screw, remove minimal distal articular cartilage from the head of the proximal phalanx to maintain length along with subchondral bone for maximum thread purchase. Remove the articular surface from the base of the intermediate phalanx. This technique is the same when one is doing an end-to-end arthrodesis with a K-wire.

   Identify the long flexor tendon with the use of a curved hemostat. When isolating the flexor tendon, plantarflex the ankle to reduce tension.5 After identifying the tendon and delivering it into the joint space, clamp the tendon as distally as possible using a straight hemostat. Cut the tendon on the distal side of the clamp and apply two curved hemostats, one on either side of the tendon. Free the plantar hood around the long flexor tendon. Using the central groove along the plantar shaft of the proximal phalanx, slice the tendon through its center to the desired length.5

   Direct your attention dorsally and release the extensor hood apparatus. Incise the capsule at the MPJ dorsally, medially and laterally, and evaluate the joint. Apply a load to the second metatarsal and determine if additional soft tissue dissection is required. If contracture is still present along with dorsal displacement, release plantar structures with a McGlamry elevator. If further digital displacement is present, a metatarsal osteotomy of your choice is required.

   One may also perform plantar plate repair at this time. Once you find the base of the proximal phalanx is articulating well with the head of the metatarsal, address lateral or medial drift. Do this by tightening either the medial or lateral capsular component.

   When it comes to type II and type III deformities, after you have transferred the flexor tendon dorsally to the base, cross and suture the tendon with the appropriate tension and desired resting position. One may use the excess tendon slips medially or laterally as an adjunct ligament to strengthen the correction.2 Suture the MPJ capsular section.

   Now that you have balanced the MPJ pathology, complete the surgery by performing the fixation for the digital arthrodesis. Reapproximate the extensor tendon and perform subsequent skin closure. It is highly recommended to obtain intraoperative C-arm pictures. This will verify exact apposition of the arthrodesis components and provides a legal document prior to patient discharge. Follow appropriate postoperative instructions based on your choice of fixation devices.

In Conclusion

In order to have successful hammertoe surgery, one must also evaluate the MPJ and correct the appropriate pathology. Evaluate the pathology and determine whether you are dealing with Slavitt classification type I, II or III pathology. Then institute the appropriate surgical procedures. Perform all capsular soft tissue releases and corrections, flexor tendon transfer positioning, metatarsal osteotomies and arthrodesis fixation, ensuring complete balance. Select a fixation device with a high rate of success. At the end of the procedure, you will be satisfied and so will your patient.

   Dr. Slavitt is board-certified by the American Board of Podiatric Surgery. He is the Chief of Podiatry in the Department of Orthopedics-Division of Podiatry at the Northwest Hospital Center in Randallstown, Md. Dr. Slavitt is also the Residency Director for the Northwest rotation of the Baltimore Veterans Administration residency program. He is also a consultant and lecturer for BioPro, Inc.

References
1. Fishco WD. Emerging concepts in hammertoe surgery. Podiatry Today. 2009; 22(9):34-38.
2. Baravarian B. Essential insights on flexor tendon transfers. Podiatry Today. 2007; 20(4):66-74.
3. Reber L, Baravarian B. Point-counterpoint: is plantar plate repair more effective than flexor tendon transfers? Podiatry Today. 2006; 19(6):64-73.
4. Olms K, Randt T. Current concepts in treating second MPJ pathology. Podiatry Today. 2008; 21(10):44-48.
5. Chang TJ. Masters Techniques in Podiatric Surgery: The Foot and Ankle. Forefoot surgery. Lippincott Williams &Wilkins, December, 2004.

Additional References
6. Fishco WD, Roth BJ. Digital fracture after a flexor tendon transfer for hammertoe repair: a case report. J Foot Ankle Surg. 2010; 49(2):179-181.
7. DiDomenico L. Essential insights on tendon transfers for digital dysfunction. Podiatry Today. 2010; 23(4):44-51.