Pedicle digital pad transfer and negative pressure wound therapy for reconstruction of the weight-bearing surface after complete digital loss in a dog

© Schattauer 2015 Vet Comp Orthop Traumatol 1/2015

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Pedicle digital pad transfer and negative pressure wound therapy for reconstruction of the weight-bearing surface after complete digital loss in a dogM. Or1; B. Van Goethem1; I. Polis1; A. Spillebeen1,4; P. Vandekerckhove2; J. Saunders3; H. de Rooster1

1Department of Small Animal Medicine and Clinical Biology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium; 2DAC Malpertuus, Heusden, Belgium; 3Department of Medical Imaging of Domestic Animals and Small Animal Orthopedics, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium; 4Current Institution: Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands

KeywordsDigit amputation, digital pad transfer, NPWT, negative pressure wound therapy, wound healing

Summary A young Labrador Retriever was presented for treatment of severe distal hindlimb necro-sis caused by bandage ischemia. During digit amputation at the metatarsophalangeal joints, the third and fourth digital pads were salvaged and transferred to the metatarsal stump to create a weight-bearing surface. Negative pressure wound therapy (NPWT) was utilized for flap immobilization and to promote granulation tissue in the remaining wound defect. Sturdy adherence of the digi-

tal pads was achieved after only four days. The skin defect healed completely by second intention and the stump was epithelialized with a thin pad after three months. At the nine month follow-up examination, the stump had a thick hyperkeratinized pad. The dog walked and ran without any apparent signs of discomfort and compensated for the loss of limb length by extending the stifle and tarsocrural joints. Despite a challenging wound in a difficult anatomical location, digital pad flap transfer and NPWT proved successful in restoring long-term ambulation in an active large breed dog.

Correspondence to:Matan Or, DVMDepartment of Small Animal Medicine and Clinical BiologyFaculty of Veterinary Medicine, Ghent UniversitySalisburylaan 133, Merelbeke, B-9820BelgiumPhone: +329 264 77 00Fax: +329 264 77 91E-mail: [email protected]

Vet Comp Orthop Traumatol 2015; 28: ■■■http://dx.doi.org/10.3415/VCOT-14-04-0056Received: April 9, 2014Accepted: November 4, 2014Epub ahead of print: December 2, 2014

Case Report

Introduction Footpads are well designed to withstand the rigors of weight bearing (1-3). Injuries are commonly caused by physical, chemi-cal, or thermal trauma (1, 4-6). Such insults

can give rise to avascular damage resulting in skin and footpad abrasions or loss, ten-dinous, muscular or ligamentous injuries, and joint luxations (7).

Damage or loss of footpads can cause the limb to become non-functional. Hence,

creating a new weight-bearing surface is necessary to salvage the limb (1, 4, 8). Several procedures have been described to restore limb function when some or all digits or the associated pads are lost (1, 5, 8, 9). The phal-angeal fillet technique, a specific digital pad transfer technique, can be used to replace or fill defects in footpads (8). During this pro-cedure, the phalanges of a non-primary weight-bearing digit (2nd or 5th) are excised, and the digital pad is retained on a pedicle of skin and advanced towards the defect (5, 8). In case all digits are lost, but the metacarpal or metatarsal pad is still intact, the latter can be rotated and sutured over the metacarpal or metatarsal stump (1, 8). Another option is to transplant digital pad grafts harvested from unaffected limbs into recessed sites in the granulation tissue on the metacarpal or meta-tarsal stump (1, 8). Other salvage procedures for dogs with complete digital loss include the use of prosthetics or orthotics (9, 10).

Superficial and full thickness injuries to pads generally heal in a fashion similar to other skin surfaces, however, pads heal more slowly (3). Footpad reconstructions are exposed to contaminated surfaces, ex-cessive motion, and self-trauma during the process of healing; therefore, they need to be protected with a padded bandage and with external support (3).

When digital pad transposition is per-formed, most patients with localized dis-ease regain limb function within two to four months. However, patients with exten-sive trauma may face a long hospitalization

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2 M. Or et al.: Negative pressure wound therapy and digital pad transfer in a dog

after surgery, problems to regain consistent limb function, and failure to achieve com-plete healing because of recurrent ulcer-ation or drainage (11).

Negative pressure wound therapy (NPWT) has gained popularity in veterin-ary medicine (12-16). One case series and one experimental controlled study demon-strated the positive effects of NPWT in dis-tal extremity wounds in dogs (12, 17). An-other experimental controlled study and the aforementioned case series reported the ap-plication of NPWT on skin grafts at distal extremities. Both showed successful results with low incidence of graft failure (12, 16).

To the authors’ knowledge, the use of NPWT in managing a pedicle digital pad transfer following metatarsophalangeal amputation has not been previously re-

ported. This report documents the clinical course and successful treatment of a dog with bandage ischemia that underwent footpad reconstruction.

Case history

A two-year-old, 24 kg, female spayed La-brador Retriever was referred for severe distal hindlimb necrosis due to bandage ischemia. On admission the dog was alert and had a non-weight-bearing (5/5) (18) right hindlimb lameness. The affected paw had intact deep pain sensation. The results of haematology and serum biochemistry analyses were within normal range. The patient was anaesthetized (propofola [5 mg/kg IV], midazolamb [0.5 mg/kg IV]) and

maintained with 1.5–2% isofluranec in oxygen for proper evaluation of the wound. Pinching of the skin was seen at the level of the tarsometatarsal junction (▶ Figure 1 A). Partial loss of the tarsal pad was apparent as well as extensive vascular compromise to the first and second digit. Both digits were amputated at the metatarso-phalangeal joint. Since the owner insisted on preserva-tion of the limb, and the remaining digits appeared less severely affected, debride-ment during the first two days was limited to removal of necrotic skin (▶ Figure 1 B, ▶ Appendix Figure 1 B-D [available online at www.vcot-online.com]). Negative press-ure wound therapy was selected to enhance vascularization of the compromised tissues and formation of healthy granulation tissue to allow future reconstructive procedures. The skin adjacent to the wound was de-greased with a liquid medical solventd, after which an adhesive skin spraye was applied. A polyurethane open-pore black foamf was contoured to the shape of the wound and strips of adhesive drapesg were applied (▶ Appendix Figure 1F – available online at www.vcot-online.com). A 2.5 x 2.5 cm hole was cut in the drapes and a suction padh was applied and connected to the NPWT uniti. Continuous negative suction pressure of 125 mmHg was applied. A light protective bandage (orthopaedic soft pad-dingj and cohesive bandagek) was placed over the NPWT dressing and an Eliza-bethan collar was applied. Because of the dog’s excited nature, acepromazinel (1 mg/kg TID) was administered. Tolerance of the

Figure 1 Right hindlimb paw of a two-year-old Labrador Retriever after bandage ischaemia. Images taken at day 0 before (A) and immediately after debridement (B). Open arrow heads in (A) indicate and area which is suggestive of deep tissue necrosis. Note the peripheral detachment of the metatarsal pad (white arrow heads), abrasion of the digital pads (white arrows), and the loss of soft tissue after debridement. Images taken on day 2 (C) and 4 (D) of the negative pressure wound therapy. See also Online Supplementary material for more images.

a Propovet Multidose: Abbott Laboratories Ltd, Maidenhead, UK

b Dormicum: nv Roche sa (Pharmaceuticals), Brus-sels, Belgium

c Isoflo: Abbott Laboratories Ltd, Maidenhead, UKd Ether: Sasol, Hamburg, Germanye Skin Adhesive spray for animals: Henry Schein,

Melville, NY, USAf V.A.C. GranuFoam™: KCI Medical Products, Gat-

wick, West Sussex, UKg V.A.C. Drape: KCI Medical Products, Gatwick,

West Sussex, UKh T.R.A.C. Pad: KCI Medical Products, Gatwick,

West Sussex, UKi V.A.C. ATS Therapy System: KCI Medical Prod-

ucts, Gatwick, West Sussex, UKj Orthoband: Millpledge Veterinary, Clarborough,

Nottinghamshire, UKk Rinkilastic cohesive: Karl Otto Braun GmbH & Co.

KG, Wolfstein, Germany




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tures were no longer functional and were removed. The wound was covered with a self-adhesive polyurethane dressingr that was changed twice, with a weekly interval, after which healthy epithelialization tissue could be seen bridging the flap to the stump. The Elizabethan collar was no long-er used. A bolsterj,k,s dressing with extra padding added to the distal part was ap-plied to prevent excessive pressure and shearing movement during weight bearing. In addition, a limb protection sockt and oral treatment with gabapentinu (5 mg/kg BID) combined with acepromazine (1 mg/kg BID, whenever needed) was initiated to reduce sensory stimulation at the healing stump and to control the excited behaviour of the dog respectively. Weekly bandage changes were performed until seven weeks after the initial treatment. Thereafter, for the next month, rechecks and bandage changes were carried out every other week.

At three months, a light soft bandage and the protective sock were still utilized, and gabapentin and acepromazine were still administered by the owner. Full skin

edges circumferentially (▶ Figure 2 A, ▶ Appendix Figure 2 A, B [available online at www.vcot-online.com]).

To accelerate adherence of the flap and to induce further granulation and bridging of the uncovered wound bed, NPWT was again applied. A polyvinyl alcohol open pore white foamq was used and a lower set-ting of negative pressure (80 mmHg) was selected. A non-weight-bearing bandage (modified Robinson sling) was placed to prevent disruptive forces during the heal-ing process (▶ Appendix Figure 3 A-D [available online at www.vcot-online.com]).

After a cycle of 48 hours, the transferred digital pads’ colour had faded, resulting in a smooth white surface covering the ventral aspect of the stump. Healthy granulation tissue had begun to bridge the flap and the skin edges of the metatarsal stump (▶ Fig-ure 2 B, ▶ Appendix Figure 2C [available online at www.vcot-online.com]). A new NPWT bandage in combination with the (modified Robinson sling) bandage was applied for another cycle of 48 hours. This resulted in a firmly attached flap and com-plete filling of the remaining defect with healthy granulation tissue. The nylon su-

M. Or et al.: Negative pressure wound therapy and digital pad transfer in a dog

system was excellent and the patient dem-onstrated immediate weight bearing (2/5) on the bandaged limb. Further medication consisted of tramadol hydrochloridem (3 mg/kg TID, 10 days) and carprofenn (2.2 mg/kg BID, 15 days) and clavulanic acid-potentiated amoxicillino (12.5 mg/kg BID, 15 days).

The first bandage change was perform-ed after a NPWT cycle of 48 hours. The pa-tient was anesthetized as previously de-scribed. Healthy granulation tissue had formed (▶ Figure 1 C). However, further sloughing of tissue was also noted: the rem-nant of the tarsal pad and the fifth digital pad were necrotic. Both were removed and the wound was flushed with sterile saline at body temperature before a new NWPT bandage was applied. A second cycle was started for another 48 hours.

After this, the entire fifth digit was de-vitalized. In contrast, a healthy granulation bed was noticed overlying the third and fourth digits and both digital pads appear-ed to be viable. Both weight-bearing digits were severely luxated at the metatarsophal-angeal level and therefore deemed func-tionally lost (▶ Figure 1 D). It was con-cluded that further delay of amputation was pointless. Transfer of the two remain-ing vital digital pads to the distal metatarsal region as a pedicle digital pad flap was planned. After complete amputation of the fifth digit, the phalangeal bones of the third and fourth digits were removed. By doing so, both digital pads remained attached by a common thin strand of new granulation tissue. The articular surfaces of the distal metatarsal bones were curetted and the plantar sesamoid bones were removed. The cranial division between both digital pads was partially extended by a midline inci-sion to better accommodate the wound bed. The digital pads were transferred pro-ximally, covering the ventral aspect of the metatarsal stump surface (▶ Figure 2 A). Simple interrupted sutures (2–0 nylonp) were used to appose the skin and wound

l Kalmivet: Vetoquinol S.A. – N.V., Aartselaar , Bel-gium

m Tramadol EG: Eurogenerics, Brussels, Belgiumn Norocarp: Norbrook Laboratories (GB) Ltd.,

Northamptonshire, UKo Kesium: Sogeval Laboratories, Laval Cedex, France

p Ethilon Nylon Suture: Johnson & Johnson Medical N.V/S.A., Ethicon Endo-Surgery, Diegem, Belgium

q V.A.C. WhiteFoam: KCI Medical Products, Gat-wick, West Sussex, UK

r Allevyn Thin: Smith & Nephew NV/SA, Zaventem, Belgium

s Bolster dressing: Melolin, Smith & Nephew NV/SA, Zaventem, Belgium

t Medipaw: Millpledge Veterinary, Clarborough, Nottinghamshire, UK

u Neurontin: Pfizer SA/NV, Elsene, Belgium

Figure 2 Surgical reconstruction of a weight-bearing surface. Intra-operative images (A) of the pedi-cal digital pad flap over the distal end of the metatarsal bones to provide a weight-bearing surface, digi-tal pad marked with an asterisk. Note the minimal amount of sutures connecting the island digital pad flap to the skin surrounding the metatarsal bones to better allow fluid removal during negative pressure wound therapy. Images taken 48 hours after the reconstruction surgery (B). Note the fast granulation tissue formation and the flap take after only one cycle of negative pressure wound therapy.





coverage of the stump was noticed but the skin was still fragile.

At the six-month follow-up, the flap was thick enough (▶ Figure 3 A) to allow weight bearing during walking and running. At the nine-month follow-up, the dog was func-tionally weight bearing on the limb (lame-ness score 1/5) without the need for any protective measures. The sites of the trans-ferred digital flap pad had become thick-ened and hyperkeratinized (▶ Figure 3 B, ▶ Appendix Figure 4 A-E [available online at www.vcot-online.com]). Radiographic evaluation of the stump demonstrated thick soft tissue coverage of the distal metatarsal bones at the amputation site (▶ Appendix Figure 5 A-B [available online at www.vcot-online.com]). The dog walked and ran with-out signs of discomfort or pain and com-pensated for the loss of limb length by ex-tending the stifle and the tarsocrural joints (▶ Appendix Films – available online at www.vcot-online.com). Goniometric meas-urements showed standing angles for the stifle joint of 156° in the affected leg and 130° in the contralateral leg (▶ Appendix Figure 6, A-B [available online at www.vcot-online.com]).

Discussion

The initial treatment goal was to salvage the affected limb by preserving the func-tion of the weight-bearing digits. However, severe joint luxation at both digits dictated

complete metatarsophalangeal amputation and preservation of a functionally weight-bearing limb became the adjusted goal. Negative pressure wound therapy was deemed the most suitable technique to achieve complete wound debridement, and to reduce the time needed to produce a healthy granulation bed (19). Although NPWT is not described as a common treatment for wounds involving the digits in small animals, this technique achieved a healthy granulation bed suitable for wound reconstruction in only four days.

In most dogs, normal skin cannot be used as a walking surface since its epithelial layers will fail to undergo metaplasia to form thick keratinized pad epithelium (1, 4, 5). After complete metatarsophalangeal amputation, a functional weight-bearing limb can be provided by transplanting the metatarsal pad to the weight-bearing sur-face (1, 8). However, in the present case the metatarsal pad was lost. Since the dog still had two digital pads that appeared viable, it was decided to use these as a pedicle digital pad transfer. The technique in this case dif-fered from the traditional phalangeal fillet, as there was no actual pedicle of skin (5, 8). The digital pads were only maintained on a thin granulated soft tissue pedicle, achiev-ed from the first stage of the NPWT. Me-ticulous care was taken not to compromise the vessels in the soft tissue connection thereby creating a pedicle digital pad flap.

A balanced weight-bearing surface, ob-tained by proper positioning of the trans-

ferred pad, is one of the most important factors to avoid development of ulceration or abrasion of the pads (4, 20). Neverthe-less, sensory innervation is also considered important in weight-bearing tissue replace-ment. Potentially, the innervation was par-tially preserved in the dog described, as is the case after free tissue transfer (20, 21). Reinnervation is also possible by collateral ingrowth of nerve fibres (22). During this process of reinnervation, discomfort and irritation from the wound site can be noted. The patient received gabapentin, which is known to control potential allody-nia much better than other analgesics (23, 24).

According to the manufacturer's in-structions, NPWT dressings should be changed every 48 to 72 hours, except for infected wounds that need more frequent bandage changes (25-27). Still, dressing in-tervals should be based on a continued evaluation of wound condition rather than on a fixed schedule. Foam embedment in granulation tissue, local foreign body reac-tion and skin necrosis are some of the com-plications that can occur when the NPWT is left on for too long (19, 28). After the digital pad flap was transferred, the authors chose a 48 hour cycle, in line with recent veterinary studies (12, 16).

In companion animals, the recom-mended negative pressure is 75 to 125 mmHg for meshed grafts and 125 to 150 mmHg for flap management (26). Lower settings, ranging from 40 to 80 mmHg, were used in two recent studies evaluating NPWT after meshed skin grafting in dogs (12, 16). Good acceptance of the grafts with quick formation of healthy granulation tis-sue in the mesh holes was observed. Since there are currently no reports describing NPWT for flaps in the veterinary literature, the authors chose a negative pressure of 80 mmHg, in order to avoid the potentially deleterious effect of too high negative pressures on the flap take. Rapid filling of defects with healthy granulation tissue after only four days (2 NPWT cycles) are effects consistent with those documented with grafts and open wound reports treated with NPWT (12, 14–17, 29-31).

While the polyurethane foam dressing is commonly used in veterinary NPWT, the authors elected to use a polyvinyl alcohol

Figure 3 Progressive epithelialization and hyperkeratinization of the weight-bearing surface. Images taken at six (A) and nine (B) months after the reconstructive surgery. Note the epithelialization and hy-perkeratinization resulting in a normally appearing digital pad.




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Acknowledgements

We wish to thank the students and the staff for their compassion and care during hos-pitalization and Filip Clompen and Ad-riaan Kitshoff for their assistance in composing the images. This case report was presented in part at the 23rd ECVS An-nual Scientific Meeting, July 3–4, 2014, Co-penhagen, Denmark.

Conflict of interest

None declared

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M. Or et al.: Negative pressure wound therapy and digital pad transfer in a dog

foam dressing after the digital pad transfer. This material is specifically designed for use in skin grafts (32). Its characteristics (hydrophilic, higher tensile strength, and increased density compared to polyure-thane foam) help to reduce the likelihood of adherence to the wound bed and the in-growth of granulation tissue. Had the tradi-tional polyurethane foam been used for similar purposes, an additional interposing material such as a semi-occlusive barrier dressing, or a vapour-permeable adhesive film dressing, would have been needed to protect the intact epidermis on top of the flap and on the opposite side of the suture line. The suture line would have had to be covered by a wide-meshed, non-adherent dressing such as a petroleum-impregnated gauze before placement of the polyure-thane foam (12, 27).

For patients with extensive trauma, the prognosis is reserved, since it takes a long time to achieve a thick hyperkeratinized epithelium on the transplanted digital pads (3, 11, 33). Incomplete resolution of ulcer-ation and drainage or problems to regain consistent weight bearing in the limb may be encountered (7, 11).

The dog in this report compensated for the loss of limb length by extending the stifle and tarsocrural joints. Although these changes seemed clinically insignificant, it should be noted that these biomechanical changes, especially in the Labrador Re-triever, could act as a stress riser on the stifle joint and the cranial cruciate ligament in particular, thus predisposing the dog to future cruciate ligament disease (34).

In conclusion, NPWT was used success-fully, both before and after island digital pad flap transfer, resulting in a quick and complete acceptance of the flap. Gradually, the newly formed footpad became thick and hyperkeratinized, providing a durable surface for weight bearing. The loss of length was compensated by extending the ipsilateral stifle and tarsocrural joints. The dog regained functional weight bearing of the limb.





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