Regenerative surgery of the complications with Morton's neuroma surgery: use of platelet rich plasma and hyaluronic acid

Abstract

Morton's neuroma is an entrapment neuropathy of the plantar digital nerve. We treated five patients with wound dehiscence and tendon exposure, after Morton's neuroma surgery excision using a dorsal approach. In this article we describe our technique. From July 2010 to August 2011, at the Department of Plastic and Reconstructive Surgery, University of Rome ‘Tor Vergata’, five patients (four females and one male), with ages ranging between 35 and 52 years, were treated with a combination of PRP (platelet rich plasma) and HA (hyaluronic acid). Thirty days following surgery, all patients showed a complete healing of the wound. The use of this technique for the treatment of postoperative wound dehiscence and tendon exposure has proven as satisfactory.

Introduction

Morton's neuroma is an entrapment neuropathy of the plantar digital nerve 1, 2.^. It is more common in women between 40 and 60 years old. Its aetiology is not understood completely, but often it occurs in pronated foot 1, 2, 3.^. In this type of foot, there is an excessive stretch of the inter‐digital nerves and an adjacent hypermobile metatarsal head. The patient complained of plantar pain exacerbated by wearing restrictive shoes. When symptoms persist for more than 3 months, surgery excision is recommended (4).^. Several approaches are described in literature. The most used are the dorsal and plantar access 5, 6, 7, 8, 9.^. However, there are secondary complications after surgical treatment, such as persistence of pain, failure of skin flap or wound dehiscence. In recent years, new techniques using regenerative surgery with platelet growth factors (platelet rich in plasma) have been achieving successful outcomes. These allow tissue regeneration by stimulating neovascularisation and cell proliferation. The authors treated five patients with wound dehiscence and tendon exposure, after Morton's neuroma surgery excision using a dorsal approach. We describe our technique as follows.

Materials and methods

From July 2010 to August 2011, at the Department of Plastic and Reconstructive Surgery, University of Rome ‘Tor Vergata’, five patients (four females and one male) aged 35 to 52 years were treated with a combination of PRP (platelet rich plasma) and HA (hyaluronic acid). All patients were brought to our attention after Morton's neuroma surgery by dorsal approach. They presented with suffering from skin flap surgery, wound dehiscence and tendon exposure, without tendency to spontaneous healing (10). All patients received a combination of PRP and HA. Our pre‐operative protocol (Figure 1) includes physical examination, blood tests, swab of the wound, systemic antibiotic therapy if needed, a series of advanced dressings for wound bed preparation and elastic compression if needed (Figure 2).

Figure 1.

Pre‐operatory view.

Figure 2.

Pre‐operatory view.

After surgery, all patients underwent systemic antibiotic therapy for 5 days and elastic‐compression bandage was applied. The follow up was performed at 7, 14, 21 and 30 days.

Surgical technique

After patient sedation, we proceeded with disinfection and surgical curettage of the area to be treated.

A self‐contained disposable kit was used to process 10 ml of peripheral venous blood. The kit consisted of one or more sterile, empty blood‐collection tubes, needles and a transfer device. After venous blood collection, it was activated by using CaGl or CaCl₂ autologous thrombin. All tubes were centrifuged at 1500 g (corresponding to 3000 r.p.m.) for 12 minutes in a centrifuge, and PRP was obtained (Figure 3).

Figure 3.

Liquid PRP infiltration.

Through this method, we obtained PRP of a high quality, with platelet and growth factor contents equal to the highest levels obtained in previously published studies. From 10 ml of peripheral blood sample, we obtained 6^.0 ± 1 ml of PRP which has 93% ± 0^·2 of platelet yield, red blood cell contaminations <0^·01, no white blood cell contaminations, platelet concentrations 2–10×, stabile separation, high concentration of platelet growth factors and low expression of P‐selectin.

PRP injections may be intralesional, intratendinous or perilesional.

The wounds were covered with three‐dimensional polymerised HA‐medicated biological dressings. HA can be left in place for 15–20 days. Growth factors have their maximum activity during the first 7 days after injection.

All patients were evaluated with a postoperative follow‐up to assess the status of the wound. Follow up was done at 7, 15, 21 and 30 days.

No patients had complications such as wound infections, edema, persisting pain or wound dehiscence.

Thirty days after surgery, all patients presented with complete wound healing.

After an average period of 2 weeks, all patients recuperated deambulation. None of the patients required further surgical correction.

Discussion

In 1845, Lewis Durlacher (11), the surgeon chiropodist to Queen Victoria, was the first to describe a neuralgic affection that involves plantar nerves between third and fourth metatarsal bones.

In 1876, Thomas G. Morton (12), a Philadelphia surgeon, localised the problem to the fourth metatarsi‐phalangeal joint. However, an Italian doctor from Pisa called Civinini gave the first anatomical description in 1835 (13).

Morton's neuroma is a painful forefoot disorder caused by thickening and fibrosis of an inter‐digital nerve.

The word ‘neuroma’ is a misnomer. An appropriate term would be ‘peri‐neural fibroma’.

Middle‐aged women are prone to this condition more often than men, by a minimum ratio of 5:1. The majority of neuromas occur in the pronated foot, because of the excessive stretch of the inter‐digital nerves and adjacent hypermobile metatarsal heads 1, 2, 3.

Its aetiology and pathogenesis are not entirely understood. We suppose that a combination of peripheral entrapment, ischemia and repetitive traumas is probably responsible for the development of the neuroma (4).

The diagnosis of Morton's neuroma is based on historical and physical examination.

Patients often present with plantar pain, which can radiate to the toes and occasionally to the dorsal aspect of the foot.

Usually, these symptoms appear as the cause of wearing high heeled, tight or restrictive shoes. Symptoms are relieved by removing shoes and resting the foot.

Symptoms may be induced by ‘pinch test' with dorsal and plantar compression of the involved inter‐space or by ‘lateral squeeze test' with medial and lateral compression of the forefoot.

Compression of the metatarsal head may induce a painful click, known as ‘Mulder's click’14, 15.

Radiological investigations are useful in confirming the diagnosis. Ultrasonography and magnetic resonance imaging are the alternative choices 16, 17.

The differential diagnosis includes inter‐metatarsal bursitis, rheumatoid arthritis, metatarsal heads osteochondritis dissecans, ischaemic pain, metabolic peripheral neuropathy, tarsal tunnel syndrome and metatarsal stress fractures.

Therapy can be conservative or surgery.

Conservative treatments include shoe‐wear modification or non‐steroidal anti‐inflammatory medications.

Second‐line therapy includes metatarsal padding, orthotics and steroid injections.

If symptoms persist beyond 3 months, surgery treatment is recommended by excision of the symptomatic portion of the nerve.

Several procedures have been described 18, 19 concerning isolated inter‐digital nerve excision, isolated transverse metatarsal ligament division or combined procedure.

Four approaches have been described for access. ‘Plantar longitudinal’1, 4, 20, 21, 22 and ‘dorsal’1, 4, 6, 23 approaches are the most commonly used techniques. Other approaches described are the ‘plantar transverse’1, 22 and the ‘web splitting’1, 24 approaches.

The choice of surgical approach depends principally on the different beliefs regarding the aetiology (4). The surgeon who chooses a plantar approach does not believe that there is a need to release the deep transverse ligament, because the transverse inter‐metatarsal ligament does not contribute to neuroma formation.

Dorsal incision is recommended as a primary surgery. McElvenny first described it in 1943 (24).^.

The dorsal approach allows the release of the transverse inter‐metatarsal ligament.

It allows early deambulation but there are some disadvantages such as difficulty in deep dissection and the potential risk to damage neurovascular structure and lumbricals.

Plantar approach is recommended for resection of a current stump neuroma. The disadvantage is a residual painful scar.

Several studies showed that dorsal approach allows an earlier deambulation recovery (2 weeks, range 1–6 weeks) than plantar approach (3 weeks, range 2–8 weeks) (25).

The five patients who presented at our department with suffering of the skin flap, wound dehiscence and tendon exposure after surgery excision by a dorsal approach received a combination of PRP and HA.

PRP is developed from autologous blood. It consists of plasma containing platelet, with a concentration that is three times more than normal. When PRP is combined with autologous thrombin and/or batroxobin (gelation‐inducing enzyme) and/or calcium chloride, platelet gel is created (Figure 4) 10, 26, 27, which is rich in growth factors.

Figure 4.

PRP gel application and suture.

Indeed, platelets are able to release cytokines and growth factors [epidermal growth factor (EGF) , vascular endothelial growth factor (VEGF), insulin‐like growth factor (IGF), transforming growth factor beta (TGF‐b), platelet‐derived growth factor (PDGF)] that help in tissue healing (28).

Autologous PRP has been safely used in the treatment of non‐healing wounds, including trophic and vascular ulcers, pressure ulcers, fistulae, burns and dermal‐epidermal dystrophies (29).

PRP has been used as an autologous scaffold for cellular growth, in combination with HA as a temporary dermal substitute.

HA is a linear glycosaminoglycan consisting of repeated units of glucuronic acid and N‐acetyl‐glucosamine, connected by alternated bonds b1‐3 and b1‐4. It is one of the major components of the extracellular matrix (ECM), synovial liquid, embryonic mesenchyme, vitreous humour, skin and other human tissues and organs. It binds several ECM molecules and several cellular receptors.

HA acts as a scaffold for the PRP, promoting remodelling and repairing damaged tissues (Figure 5).

Figure 5.

Hyaluronic acid matrix application and suture.

According to our studies and international literature, the combination of PRP and HA promotes significantly the formation of granulation tissue and reduces the healing times and the need for surgical correction 10, 30.

Conclusion

Our in vivo studies have shown that PRP combined with HA enables a more rapid regeneration of damaged tissues, because PRP property is similar to HA. Furthermore, they allow growth factor recovery, improve their bioavailability and are not immunogenic. They influence cellular and ECM functions, and serve as a scaffold. These reasons show that PRP and HA act as a tissue regenerative system. The use of this technique for the treatment of postoperative wound dehiscence has proven to be satisfactory.

Thirty days following surgery (Figure 6), all patients showed complete healing of their wounds.

Figure 6.

Post‐operatory view at 30 days.

Both aesthetic and functional results were satisfactory. The tissue presented with adequate mobility.

No complications were observed.

Patients showed a recovery of deambulation 2 weeks after surgery.

We believe that the combination of PRP and HA should be used in all cases of wound dehiscence with tendon exposure. Additionally, PRP has anti‐inflammatory and analgesic properties. It can be stated that the PRP is useful in a pre‐operative phase.