Understanding The Osseous Contribution To Chronic Wounds

Structural deformities often contribute to the development of chronic wounds in the lower extremity but post-op offloading protocols with traditional surgical techniques can be difficult in high-risk populations. Accordingly, this author offers a closer look at soft tissue and osseous techniques that can address global forefoot deformities associated with chronic wounds, and allow early, guarded weightbearing.

The costs of chronic foot ulceration, secondary infection and subsequent amputation as a result of diabetes are staggering.1-4 Despite advances in limb salvage techniques and medical management, diabetes will continue to rise as the world’s population continues to become more obese and less active.5-9 It is understood that the primary event preceding amputation is infection.10-15

   It therefore is intuitive that preventing ulcerations from becoming chronic will limit the potential for infection to develop. This should logically lower the incidence of amputations. There continues to be an emphasis on relieving pressure and shear about forefoot ulcerations through conservative measures such as the use of various offloading devices.16-18 While literature does support this approach as an effective means of healing acute forefoot ulcerations, it does not support the continued use of these techniques for chronic forefoot ulcerations. Accordingly, their role in the treatment of chronic ulcerations is unclear at best.19-23

   This stands to reason as the most likely cause for developing the ulcer in the first place is a structural foot deformity, which is most commonly rigid in nature and may be combined with varying degrees of peripheral sensory neuropathy.20-27 Studies have demonstrated that realignment of the mechanical forefoot deformities associated with patients with diabetes decreases the need for chronic wound care and improves outcomes.20,28-33 Unfortunately, the application of traditional surgical approaches and techniques including periods of non-weightbearing can be difficult in this patient population as the potential for complications is inherently high.33,34

   Therefore, it intuitively makes sense that one would desire either to minimize the extent of surgical intervention through the use of minimum incision surgical techniques or, if traditional open procedures are required, utilize fixation techniques that permit early protected weightbearing. I have previously discussed the application of various minimum incision surgical techniques for limb salvage surgery in detail.35-38 Accordingly, I will focus this discussion on structural realignment of global forefoot deformities associated with chronic ulceration and the use of soft tissue and osseous techniques that permit early, guarded weightbearing.

How To Address Flexion Contracture Of The Toes And Concurrent Chronic Wounds

Flexion contracture of the hallux and lesser toes is a common occurrence in patients with chronic ulcerations at the toe level. This is especially true of the plantar hallux interphalangeal joint ulceration and distal tuft ulcerations of the lesser toes.39-47

   In these situations, there is an effective method that can correct the global structural deformities responsible for development of the chronic ulceration yet allow early protected weightbearing. This method consists of percutaneous tenotomy of the long flexor tendons to the hallux and each lesser toe followed by manipulation of the toes in a dorsal direction (a.k.a. phalangeal set procedure). This is accompanied by debridement and coverage of the ulceration.46,47 I have found that an acellular dermal matrix (MemoDerm™, Memometal), which employs a sterile sheet of pre-fenestrated cadaveric skin, is capable of providing durable coverage to chronic ulcerations.

   One usually performs the surgical technique in an in-office surgical suite and begins with the patient in a supine position. A tourniquet is not required as blood loss is minimal. Patients with dense peripheral neuropathy will not require anesthesia. However, for sensate patients, one may perform a regional infiltration of local anesthesia.
The specific surgical approach involves covering the chronic ulceration with an impermeable sterile incision barrier followed by percutaneous flexor tenotomy of the flexor hallucis longus and the flexor digitorum longus to each lesser toe.35,47

   Place a 3 mm incision on the plantar aspect of the toe at the apex of the deformity, which is usually at the level of the proximal or distal interphalangeal joint. The incision should be parallel with the longitudinal axis of the toe (i.e., perpendicular to the course of the tendon). Carry the incision deep to the underlying long flexor tendon. Proceed to transect this tendon under tension. You can create this tension by simultaneously extending the tip of the toe with the index finger on your non-dominant hand and extending the proximal interphalangeal joint with your thumb.

   Alternatively, one can make the incision at the plantar aspect of the base of the proximal phalanx. Doing so will release both the flexor digitorum longus and brevis tendons. Surgeons should reserve this technique for severe contractures as it will result in a non-functional, albeit straightened toe.

   Following the transection of the long flexor tendon, forcefully manipulate the toe in a dorsal direction. This facilitates the release of any remaining tendon fibers and disrupts the plantar plates to the proximal and distal interphalangeal joints (i.e., phalangeal set procedure).46 After achieving correction, close the surgical site with a single metallic staple or nylon suture if appropriate. Otherwise, one can leave the site open to heal via secondary intention.

   Following completion of the percutaneous flexor tenotomies, direct attention to the chronic ulceration. One should perform surgical debridement until there is a clean and well perfused vascular bed, and the chronic ulceration has been converted into a clean, acute wound. The surgeon can cover the ulceration with the acellular dermal matrix, which provides a collagen scaffold for vascular ingrowth and eventual epithelialization.

   MemoDerm is provided sterile and freeze-dried. Upon removing the product from the manufacturer’s packaging, you will find that MemoDerm is firmly adherent to a blue mesh that is in contact with the dermal or deep side of the cadaveric skin. One will ultimately place this surface in direct contact with the wound bed. I prefer to use a hemostat to clamp one corner of the product so the mesh does not separate during the rehydration process. After clamping the product, place it into a basin filled with sterile saline for approximately 10 minutes to allow for rehydration. The manufacturer has placed a small “nick” in one corner of the product. The product is properly oriented when one positions this nick in the upper right hand corner of the wound bed with the blue mesh in contact with the wound bed.

   Following rehydration, separate the MemoDerm from the blue mesh backing. Transfer the matrix to the wound bed and secure it to the surrounding tissues using sutures, metallic skin staples or adhesive backed Steri-Strips. One should make certain the product is in direct contact with the wound bed. Also ensure the product is secure enough to prevent excessive motion during use of the limb, which would shear off the product and obviously lead to failure of MemoDerm. I prefer to apply an antibiotic impregnated ointment over the product and further cover the wound with a non-adherent dressing.

   Then apply a well padded dressing from the toes to the knee. One may allow protected full-weightbearing in a postoperative shoe with patients avoiding push-off on their forefoot.15 Remove the initial surgical dressings in three to five days and then change the dressing every seven to 10 days thereafter until full healing has occurred.48 Once healing has occurred, the patient with diabetes may return to extra-depth shoe gear with accommodative multi-density insoles.

When There Are Rigid Global Toe Deformities With Chronic Ulceration

When it comes to patients with rigid global toe deformities or neuromuscular contractures, soft tissue procedures alone are not likely to lead to long-term stabilization. Instead, osseous surgical treatment is indicated with surgeons most commonly employing arthrodesis of the hallux interphalangeal joint and proximal interphalangeal joints of the lesser toes.

   Traditionally, surgeons have employed screw fixation for the hallux interphalangeal joint and smooth Kirschner wire fixation for the lesser toes.49,50 However, these forms of fixation do not allow early mobilization. This is due to the potential of screws to:
• loosen;
• provide a portal for entry of bacteria at the pin/screw entry site that can lead to infection; and
• delay the ability to return to shoe gear until one has removed the fixation.50

   To counter these limitations, I have employed a one-piece shape memory intramedullary implant fixation for both hallux interphalangeal joint (X-Fuse® Hallux Interphalangeal Arthrodesis Implant, Memometal) and lesser toe interphalangeal joints (Smart Toe® Intramedullary Memory Implant, Memometal).

   By definition, these implants are intramedullary and therefore eliminate the risk of pin tract infection associated with external axial smooth Kirschner wire fixation. Since they do not consist of degradable material, the implants will not produce sinus tract formation with the potential for secondary bacterial infection. As these implants are one piece, one can achieve easy insertion and mitigate the presence of a failure point. The design of the implants produces compression between the resected surfaces of the interphalangeal joint and resists rotation. Finally, for the lesser toes, the implants only cross the proximal interphalangeal joint, thereby sparing the distal interphalangeal joint.50

   The surgical technique begins with a dorsal transverse, converging, semi-elliptical incision centered over the proximal phalanx head with excision of the ellipse of skin. Proceed to deepen the incision through the underlying extensor tendon apparatus to expose the proximal interphalangeal joint. Free the head of the proximal phalanx from surrounding soft tissue attachments and follow this with resection at the metaphyseal-diaphyseal junction. Resect the base of the adjacent phalanx with a rotary burr or hand reamer instrumentation. Follow this by utilizing specialized broaches to create guide holes within the medullary canals to accept the implants delivered with specific forceps. Apply manual compression across the arthrodesis site to ensure proper seating of the implant and verify this with intraoperative image intensification. Then reapproximate the extensor tendon complex with a figure-of-eight suture using absorbable sutures and proceed to skin closure according to your preference.

   Apply a bulky, well-padded dressing from the toes to the knee. Allow full weightbearing in a postoperative shoe and change the dressings as I discussed above for soft tissue surgical treatment.15,48 As I noted above, once full healing has occurred, the patient can wear an extra-depth shoe with accommodative multidensity orthoses.

Pertinent Pearls On Osseous Surgery For Global MPJ Deformities With Chronic Ulceration

For patients with global metatarsophalangeal joint (MPJ) deformities and plantar metatarsal head chronic ulceration, osseous surgical treatment is indicated via first MPJ arthrodesis, resection arthroplasty of the central metatarsal heads with excision of the ulceration, and interphalangeal joint arthrodesis of the lesser toes.

   While a myriad of fixation options exist for arthrodesis of the first MPJ, the two most commonly reported techniques involve the use of crossed compression screws or a construct consisting of a compression screw and dorsal plate. The literature is not clear regarding the ability to permit early weightbearing with these techniques.51-53 The Ti-Fuse™ (Memometal) is a novel implant, which employs ridged elastic nails of varying lengths with a “T” peg at the distal end and allows for immediate protected weightbearing.

   Following preparation of the joint surfaces using your technique of choice, align the first MPJ according to the patient’s particular anatomy. Penetrate the plantar-medial aspect of the base of the proximal phalanx with a 1.5 mm drill and load the appropriate length Ti-Fuse onto the specially designed implant driver pliers. Tamp the implant into place until the “T” portion of the implant contacts the phalangeal cortex. For proper alignment, the implant should enter the phalanx in a similar fashion as one would do for crossed compression screw fixation. However, instead of penetrating the lateral cortex of the first metatarsal, the implant will deflect off the lateral cortical wall and into the medullary canal of the first metatarsal.

   Then perform the same process, starting at the dorsomedial aspect of the first metatarsal head and angling distally into the base of the proximal phalanx. Add a static metallic staple dorsally across the first MPJ to limit the potential for rotation during the consolidation process.

   I conducted a recent unpublished study involving 95 feet in 83 patients, who underwent first MPJ arthrodesis with the aforementioned technique and immediate weightbearing in a postoperative shoe. The results revealed a non-union rate of only 3.2 percent (three patients). The presence of osteopenic bone warrants the use of one or two supplemental Ti-Fuse implants to enhance stability.

   Surgeons most commonly perform resection of the lesser metatarsal heads with a plantar incision that includes excision of the chronic ulceration and permits relocation of the distally migrated plantar fat padding. This is similar to the technique surgeons would employ with rheumatoid arthritic forefoot reconstruction.54,55

   The key component to understand is that one carries the incision through the plantar skin and adipose tissue to the level of the deep fascia. After incising the skin, place the remaining linear incisions at the central aspect of the MPJs. One would subsequently excise the plantar plates, thereby allowing visualization and subsequent resection of the metatarsal heads in a proper weightbearing parabola.

   I address any associated toe deformities with SmartToe intramedullary implants as described above.56-58 Then reapproximate deep tissues with absorbable suture followed by skin closure according to the surgeon’s preference.

   Apply a bulky, well-padded dressing from the toes to the knee and allow full weightbearing in a postoperative shoe. Change the dressings as described above for soft tissue surgical treatment.15,48 As I noted above, once full healing has occurred, the patient can wear an extra-depth shoe with accommodative multi-density orthoses.

In Conclusion

When it comes to structural realignment of global toe and metatarsophalangeal joint deformities associated with chronic ulceration, utilizing specialized implants and cadaveric tissues can be beneficial in performing soft tissue and osseous techniques that permit early, protected weightbearing.

   The benefits of these approaches include the ability to simultaneously correct the structural deformities responsible for the development of ulceration, as well as achieve prompt coverage of the chronic ulceration with a sterile cadaveric acellular dermal matrix or excision and primary closure. Additionally, early or immediate protected weightbearing is possible and potential complications are minimal.

   Dr. Roukis is affiliated with the Department of Orthopaedics, Podiatry and Sports Medicine at Gundersen Lutheran Medical Center in La Crosse, Wis. He is a Member of the Board of Directors and a Fellow of the American College of Foot and Ankle Surgeons.

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   For further reading, see “Minimal Incision Surgery: Can It Have An Impact In Diabetic Limb Salvage?” in the March 2009 issue of Podiatry Today.