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Morton’s Neuroma
CHAPTER 91
Morton’s Neuroma Glenn G. Shi, MD
Synonyms Perineural fibroma Morton’s neuralgia Intermetatarsal neuroma Interdigital neuroma Interdigital nerve compression syndrome
ICD-10 Code G57.90 Mononeuropathy of unspecified lower limb G57.91 Mononeuropathy of right lower limb G57.92 Mononeuropathy of left lower limb G57.60 Lesion of plantar nerve, unspecified limb G57.61 Lesion of plantar nerve, right lower limb G57.62 Lesion of plantar nerve, left lower limb
Definition Morton’s neuroma refers to a compressive neuropathy of the interdigital nerve along the distal edge of the intermetatarsal ligament in the third webspace. Thomas Morton theorized that the interdigital nerve was compressed by the third and fourth metatarsal heads. Further anatomic studies later dispelled that theory, as the nerve is plantar to the intermetatarsal ligament. Regardless, Morton’s neuroma is a popular term that describes the compressive neuropathy that should be more appropriately termed interdigital neuralgia.1 Anatomic and radiologic studies demonstrate that rather than true neuroma, more than likely the symptoms are due to the fibrous tissue proliferation brought on by microvascular and neural microtrauma at the level of the forefoot near the intermetatarsal ligament resulting in scar, perineural fibrotic proliferation, mass effect, and dysvascularity.2–4 These factors predispose the patients to sensitivity and pain. Pain from Morton’s neuroma is most reported to be in the third webspace where the interdigital nerve receives dual supply from both the medial and lateral plantar nerves (Fig. 91.1). Additionally, mobile fourth and fifth metatarsals can cause friction and tethering of the nerve against a relatively immobile third metatarsal, causing traction neuralgia.5 The average age of patient presenting with Morton’s neuroma is 55 years with female sex predominance (ratio 4:1). Although patients are more likely to present with unilateral symptoms, approximately 3% to 15% will have bilateral forefoot pain.6
Symptoms Primary reason for clinical visit in patients with Morton’s neuroma is activity-associated forefoot pain in the third webspace. Patients often report aching, cramping, numbness, and occasional burning sensation that may radiate to the third and fourth toes. Some patients report a retrograde Valleix phenomenon with pain radiating proximally or dorsally through the foot from the epicenter distally at the level of the transverse ligament. At times, patients describe a rolled-up sock sensation under their foot that will not subside. Symptoms tend to worsen with constrictive footwear such as high heels. The majority of patients notice pain resolution with removal of constrictive footwear.
Physical Examination On seated exam, the pain is reproducible with palpa tion of the third interdigital webspace. The digital compression along with medial-lateral squeeze can simulate the pain patients experience in a constrictive shoe (Fig. 91.2). Webspace tenderness is positive in 95% of patients who chose to undergo surgical excision.7 Mulder’s click test is helpful and has been described to be associated with a neuroma. With the patient seated and knee at 90 degrees, the physician then performs dorsoplantar compression of the third webspace while the opposite hand provides medial-lateral pressure. The click sensation is felt when this test is positive and frequently results in pain. It is imperative to examine the forefoot for alternative causes of forefoot pain such as metatarsalgia, synovitis, radiculopathy, tarsal tunnel syndrome, plantar plate tear, and hammertoe deformities. Palpation of the metatarsophalangeal joints (MTPJs) is necessary to evaluate for synovitis or plantar fat pad atrophy. Stability of MTPJs must be examined by stabilizing the metatarsal head and performing a drawer test with the proximal phalanx. Instability of MTPJs causes potential for traction interdigital neuralgia, further traumatizing the already painful condition. Routinely, patients should undergo Silverskiold test for equinus contracture. This test determines whether the contracture stems from the gastrocnemius versus Achilles tendon. In isolated gastrocnemius contractures, the ankle equinus contracture with the knee extended significantly improves up to 10 degrees of ankle dorsiflexion when the knee is flexed to 90 degrees. Clinically significant equinus contracture can cause additional forefoot pressure that tends to accentuate symptomatic neuroma or metatarsalgia. 497
498
PART 1 MSK Disorders
Transverse metatarsal ligament
radiographic bone length or joint angles that correlates with symptomatic Morton’s neuroma.9 Advanced imaging such as ultrasound or magnetic resonance imaging can confirm Morton’s neuroma and be of value in cases where the diagnosis uncertain. They are more useful to rule out differential diagnoses such as plantar plate tears, soft tissue tumors, stress fractures, and ligamentous injuries.10 The size of the neuroma on these imaging modalities has no correlation with severity of clinical symptoms. There is evidence that age and size of the neuroma are predictors of further treatment within 2 years after corticosteroid injection.12 Electromyography and nerve conduction velocity studies have not previously confirmed to be helpful in the diagnosis of Morton’s neuroma. However, these studies may help to exclude alternative diagnoses such as radiculopathy, peripheral neuropathy, or tarsal tunnel syndrome that may mimic a neuroma.
Neuroma
Differential Diagnosis
FIG. 91.1 Interdigital nerves exit underneath the transverse ligament, resulting in potential repetitive microtrauma and fibrosis.
Metatarsal stress fracture Metatarsal head avascular necrosis/Freiberg’s infraction Metatarsophalangeal joints synovitis Plantar plate rupture Tarsal tunnel syndrome Peripheral neuropathy Tumor
Treatment Initial Nonsurgical management should be the first line of treatment. Patient education starts with proper shoe-wear selection and activity modification. Wide toe box and stiff soled shoes should be the main form of shoe wear. A metatarsal pad placed on an insert at the level proximal to the metatarsal heads can reduce the plantar driven force across the metatarsal heads, resulting in less pain. When metatarsal pads improve the patient’s pain level, permanent orthoses with a metatarsal bar can be considered. A prescription for this should be given to the patient for custom orthotics to be made by a licensed orthotist. FIG. 91.2 Physical exam with dorsoplantar pressure about the third webspace with mediolateral compression can reproduce pain.
Functional Limitations Patients with Morton’s neuroma rarely present with gait abnormalities. They often complain of inconvenience with inability to wear fashionable shoes. When symptoms continue to progress, weight-bearing activities may be restricted.
Diagnostic Studies The diagnosis of Morton’s neuroma is classically made clinically based on patient history and physical examination with sensitivity as high as 98%.8 Weight-bearing anteroposterior, oblique, and lateral foot radiographs can be obtained to rule out bony pathology. There is no relationship between
Rehabilitation If equinus contracture is found on exam, then the patient may benefit from a brief course of physical therapy with home stretching routine to reduce the forefoot overload. Postoperative patients are instructed to elevate the foot frequently above the level of the nose to improve swelling control and reduce tension across the incision. Often, the sensation of swelling and fullness persist for up to 6 months after surgery. Physical therapy may be helpful in gait training; however, for most patients, routine activities of daily living are sufficient to regain their strength.
Procedures Diagnostic and also therapeutic injection with 1% lidocaine with corticosteroid into the affected webspace can help isolate the source of pain. The clinician must ensure the proper
CHAPTER 91 Morton’s Neuroma
depth of the injection, as the lidocaine must traverse the transverse intermetatarsal ligament. Use isopropyl alcohol wipes to sanitize the dorsal and the plantar skin (in the event of accidental penetration of the plantar skin) while using a 25-gauge needle for foot and ankle injections to reduce the level of discomfort during the injection. Injections can be done in the clinic, with or without ultrasound, producing equivalent success rate11; 1 mL of 0.5% bupivacaine without epinephrine mixed with corticosteroid can be used. Short-term outcomes after injection are acceptable, while long-term results are highly variable. Although the relief can last for over 1 year in 30% of the patients, it should be used with caution. Several series demonstrated highly variable outcomes with concerns for sclerosing effects of the alcohol agents on local tissues beyond the nerve. Short-term pain relief ranges from 22% to 94% with 64% with recurrence of pain or electing surgical excision within 5 years.13,14 The use of capsaicin injections had been studied in a randomized, double-blind placebo-controlled trial in 58 patients with Morton’s neuroma with significant pain relief in the capsaicin group. No mid- or long-term follow up are available.15 Another study explored extracorporeal shockwave therapy (ESWT) in patients with Morton’s neuroma in a randomized trial. Compared to a sham stimulation procedure, ESWT showed promise in pain relief in the short term.16 One should be cautious when considering injections into the forefoot. Not enough long-term evidence exists to convince patients that benefits outweigh risks for serial alcohol sclerosing injections. Corticosteroid injection can be attempted with or without ultrasound as a diagnostic and therapeutic method and should not be repeated more frequently than every 3 months since they do not correlate with permanent pain resolution.1
Technology There is no specific technology for the treatment or rehabilitation of this condition.
Surgery Operative management of neurolysis versus neurectomy is offered to patients who failed nonoperative measures. Morton’s neuroma excision is the most common procedure (Fig. 91.3). Often surgeons prefer the dorsal approach to avoid development of plantar forefoot pain from scarring. The neuroma can be approached from the dorsal or plantar side of the nerve and is excised proximal to the bifurcation.17–20 Good to excellent results have been reported in 51% to 91% of patients. One study reported 78.8% good to excellent outcomes in 99 consecutive patients in the first prospective study to look at pre- and postsurgical patients who underwent neuroma excision; 63% of the patients reported being pain free at the final follow up.21 Another series of 41 patients who were treated for Morton’s neuroma with neurectomy reported an average follow up of 7.4 years; 76% of the patients had sustained pain relief.20 Another long-term study involving 120 patients who underwent operative neuroma excision showed a good or excellent rating in only 51% of the study population after an average of 66.7 months follow up.22 Neurolysis is another procedure that can be considered in select patients. In 50 patients (69 feet), the interdigital nerve
499
FIG. 91.3 Intraoperative specimen of an interdigital neuroma.
was examined at the time of surgery. If a nerve appeared to be bulbous and fibrotic, the nerve was excised whereas a nerve without macroscopic pseudoneuroma appearance was preserved after neurolysis. Preservation of the nerve and avoiding interdigital numbness can be an option if the nerve appears to be in good condition.23 Neurolysis can be combined with neurectomy in cases where adjacent webspace interdigital neuromas (i.e., second and third webspace neuromas) are suspected. Twenty-three patients with adjacent webspace neuromas were evaluated after excision of one nerve and neurolysis of the other; 95% at the end of their follow up reported satisfaction.24 Several studies looked at minimally invasive decompression procedures in patients with Morton’s neuroma with good short-term success and faster recovery than traditional open procedure. In a small series of 14 patients, 11/14 patients reported no recurrence of symptoms after minimally invasive decompression.25
Potential Disease Complications Potential disease complications include persistent refractory or intractable nerve pain, reduced mobility, functional limitation, and shoe-wear restrictions.
Potential Treatment Complications Steroid injection-associated complications include skin discoloration, infection, fat pad atrophy, and plantar plate and collateral ligament tears. Specific complications related to Morton’s neuroma excision include wound complications, digital vascular disruption, metatarsal stress fracture, crossover or hammertoe after injury to collateral ligaments, and persistent pain with stump neuroma. Some of the complications such as delayed healing and regional soft tissue damage are seen frequently in patients who received multiple corticosteroid and alcohol injections.
500
PART 1 MSK Disorders
References 1. Weinfeld SB, Myerson MS. Interdigital neuritis: diagnosis and treatment. J Am Acad Orthop Surg. 1996;4:328–335. 2. Bossley CJ, Cairney PC. The intermetatarsophalangeal bursa–its significance in Morton’s metatarsalgia. J Bone Joint Surg Br. 1980;62-B:184–187. 3. Ha’Eri GB, Fornasier VL, Schatzker J. Morton’s neuroma–pathogenesis and ultrastructure. Clin Orthop Relat Res. 1979:256–259. 4. Graham CE, Graham DM. Morton’s neuroma: a microscopic evaluation. Foot Ankle. 1984;5:150–153. 5. Ouzounian TJ, Shereff MJ. In vitro determination of midfoot motion. Foot Ankle. 1989;10:140–146. 6. Mann RA, Reynolds JC. Interdigital neuroma–a critical clinical analysis. Foot Ankle. 1983;3:238–243. 7. Owens R, Gougoulias N, Guthrie H, Sakellariou A. Morton’s neuroma: clinical testing and imaging in 76 feet, compared to a control group. Foot Ankle Surg. 2011;17:197–200. 8. Pastides P, El-Sallakh S, Charalambides C. Morton’s neuroma. A clinical versus radiological diagnosis. Foot Ankle Surg. 2012;18:22–24. 9. Naraghi R, Bremner A, Slack-Smith L, Bryant A. Radiographic analysis of feet with and without Morton’s neuroma. Foot Ankle Int. 2017;38(3):310–317. 10. Claassen L, Bock K, Ettinger M, Waizy H, Stukenborg-Colsman C, Plaass C. Role of MRI in detection of Morton’s neuroma. Foot Ankle Int. 2014;35:1002–1005. 11. Mahadevan D, Attwal M, Bhatt R, Bhatia M. Corticosteroid injection for Morton’s neuroma with or without ultrasound guidance: a randomised controlled trial. Bone Joint J. 2016;98-B:498–503. 12. Mahadevan D, Salmasi M, Whybra N, Nanda A, Gaba S, Mangwani J. What factors predict the need for further intervention following corticosteroid injection of morton’s neuroma? Foot Ankle Surg. 2016;22:9–11. 13. Gurdezi S, White T, Ramesh P. Alcohol injection for Morton’s neuroma: a five-year follow-up. Foot Ankle Int. 2013;34:1064–1067. 14. Hughes RJ, Ali K, Jones H, Kendall S, Connell DA. Treatment of Morton’s neuroma with alcohol injection under sonographic guidance: follow-up of 101 cases. AJR Am J Roentgenol. 2007;188:1535–1539.
15. Campbell CM, Diamond E, Schmidt WK, et al. A randomized, doubleblind, placebo-controlled trial of injected capsaicin for pain in Morton’s neuroma. Pain. 2016;157:1297–1304. 16. Seok H, Kim SH, Lee SY, Park SW. Extracorporeal shockwave therapy in patients with Morton’s neuroma a randomized, placebo-controlled trial. J Am Podiatr Med Assoc. 2016;106:93–99. 17. Akermark C, Crone H, Skoog A, Weidenhielm L. A prospective randomized controlled trial of plantar versus dorsal incisions for operative treatment of primary Morton’s neuroma. Foot Ankle Int. 2013;34: 1198–1204. 18. Killen MC, Karpe P, Limaye R. Plantar approach for Morton’s neuroma: an effective technique for primary excision. Foot (Edinb). 2015;25:232–234. 19. Kundert HP, Plaass C, Stukenborg-Colsman C, Waizy H. Excision of Morton’s neuroma using a longitudinal plantar approach: a midterm follow-up study. Foot Ankle Spec. 2016;9:37–42. 20. Reichert P, Zimmer K, Witkowski J, Wnukiewicz W, Kulinski S, Gosk J. Long-term results of neurectomy through a dorsal approach in the treatment of Morton’s neuroma. Adv Clin Exp Med. 2016;25: 295–302. 21. Bucknall V, Rutherford D, MacDonald D, Shalaby H, McKinley J, Breusch SJ. Outcomes following excision of Morton’s interdigital neuroma: a prospective study. Bone Joint J. 2016;98-B:1376–1381. 22. Womack JW, Richardson DR, Murphy GA, Richardson EG, Ishikawa SN. Long-term evaluation of interdigital neuroma treated by surgical excision. Foot Ankle Int. 2008;29:574–577. 23. Villas C, Florez B, Alfonso M. Neurectomy versus neurolysis for Morton’s neuroma. Foot Ankle Int. 2008;29:578–580. 24. Hort KR, DeOrio JK. Adjacent interdigital nerve irritation: single incision surgical treatment. Foot Ankle Int. 2002;23:1026–1030. 25. Zelent ME, Kane RM, Neese DJ, Lockner WB. Minimally invasive Morton’s intermetatarsal neuroma decompression. Foot Ankle Int. 2007;28: 263–265.
Morton’s Neuroma Glenn G. Shi, MD
Synonyms Perineural fibroma Morton’s neuralgia Intermetatarsal neuroma Interdigital neuroma Interdigital nerve compression syndrome
ICD-10 Code G57.90 Mononeuropathy of unspecified lower limb G57.91 Mononeuropathy of right lower limb G57.92 Mononeuropathy of left lower limb G57.60 Lesion of plantar nerve, unspecified limb G57.61 Lesion of plantar nerve, right lower limb G57.62 Lesion of plantar nerve, left lower limb
Definition Morton’s neuroma refers to a compressive neuropathy of the interdigital nerve along the distal edge of the intermetatarsal ligament in the third webspace. Thomas Morton theorized that the interdigital nerve was compressed by the third and fourth metatarsal heads. Further anatomic studies later dispelled that theory, as the nerve is plantar to the intermetatarsal ligament. Regardless, Morton’s neuroma is a popular term that describes the compressive neuropathy that should be more appropriately termed interdigital neuralgia.1 Anatomic and radiologic studies demonstrate that rather than true neuroma, more than likely the symptoms are due to the fibrous tissue proliferation brought on by microvascular and neural microtrauma at the level of the forefoot near the intermetatarsal ligament resulting in scar, perineural fibrotic proliferation, mass effect, and dysvascularity.2–4 These factors predispose the patients to sensitivity and pain. Pain from Morton’s neuroma is most reported to be in the third webspace where the interdigital nerve receives dual supply from both the medial and lateral plantar nerves (Fig. 91.1). Additionally, mobile fourth and fifth metatarsals can cause friction and tethering of the nerve against a relatively immobile third metatarsal, causing traction neuralgia.5 The average age of patient presenting with Morton’s neuroma is 55 years with female sex predominance (ratio 4:1). Although patients are more likely to present with unilateral symptoms, approximately 3% to 15% will have bilateral forefoot pain.6
Symptoms Primary reason for clinical visit in patients with Morton’s neuroma is activity-associated forefoot pain in the third webspace. Patients often report aching, cramping, numbness, and occasional burning sensation that may radiate to the third and fourth toes. Some patients report a retrograde Valleix phenomenon with pain radiating proximally or dorsally through the foot from the epicenter distally at the level of the transverse ligament. At times, patients describe a rolled-up sock sensation under their foot that will not subside. Symptoms tend to worsen with constrictive footwear such as high heels. The majority of patients notice pain resolution with removal of constrictive footwear.
Physical Examination On seated exam, the pain is reproducible with palpa tion of the third interdigital webspace. The digital compression along with medial-lateral squeeze can simulate the pain patients experience in a constrictive shoe (Fig. 91.2). Webspace tenderness is positive in 95% of patients who chose to undergo surgical excision.7 Mulder’s click test is helpful and has been described to be associated with a neuroma. With the patient seated and knee at 90 degrees, the physician then performs dorsoplantar compression of the third webspace while the opposite hand provides medial-lateral pressure. The click sensation is felt when this test is positive and frequently results in pain. It is imperative to examine the forefoot for alternative causes of forefoot pain such as metatarsalgia, synovitis, radiculopathy, tarsal tunnel syndrome, plantar plate tear, and hammertoe deformities. Palpation of the metatarsophalangeal joints (MTPJs) is necessary to evaluate for synovitis or plantar fat pad atrophy. Stability of MTPJs must be examined by stabilizing the metatarsal head and performing a drawer test with the proximal phalanx. Instability of MTPJs causes potential for traction interdigital neuralgia, further traumatizing the already painful condition. Routinely, patients should undergo Silverskiold test for equinus contracture. This test determines whether the contracture stems from the gastrocnemius versus Achilles tendon. In isolated gastrocnemius contractures, the ankle equinus contracture with the knee extended significantly improves up to 10 degrees of ankle dorsiflexion when the knee is flexed to 90 degrees. Clinically significant equinus contracture can cause additional forefoot pressure that tends to accentuate symptomatic neuroma or metatarsalgia. 497
498
PART 1 MSK Disorders
Transverse metatarsal ligament
radiographic bone length or joint angles that correlates with symptomatic Morton’s neuroma.9 Advanced imaging such as ultrasound or magnetic resonance imaging can confirm Morton’s neuroma and be of value in cases where the diagnosis uncertain. They are more useful to rule out differential diagnoses such as plantar plate tears, soft tissue tumors, stress fractures, and ligamentous injuries.10 The size of the neuroma on these imaging modalities has no correlation with severity of clinical symptoms. There is evidence that age and size of the neuroma are predictors of further treatment within 2 years after corticosteroid injection.12 Electromyography and nerve conduction velocity studies have not previously confirmed to be helpful in the diagnosis of Morton’s neuroma. However, these studies may help to exclude alternative diagnoses such as radiculopathy, peripheral neuropathy, or tarsal tunnel syndrome that may mimic a neuroma.
Neuroma
Differential Diagnosis
FIG. 91.1 Interdigital nerves exit underneath the transverse ligament, resulting in potential repetitive microtrauma and fibrosis.
Metatarsal stress fracture Metatarsal head avascular necrosis/Freiberg’s infraction Metatarsophalangeal joints synovitis Plantar plate rupture Tarsal tunnel syndrome Peripheral neuropathy Tumor
Treatment Initial Nonsurgical management should be the first line of treatment. Patient education starts with proper shoe-wear selection and activity modification. Wide toe box and stiff soled shoes should be the main form of shoe wear. A metatarsal pad placed on an insert at the level proximal to the metatarsal heads can reduce the plantar driven force across the metatarsal heads, resulting in less pain. When metatarsal pads improve the patient’s pain level, permanent orthoses with a metatarsal bar can be considered. A prescription for this should be given to the patient for custom orthotics to be made by a licensed orthotist. FIG. 91.2 Physical exam with dorsoplantar pressure about the third webspace with mediolateral compression can reproduce pain.
Functional Limitations Patients with Morton’s neuroma rarely present with gait abnormalities. They often complain of inconvenience with inability to wear fashionable shoes. When symptoms continue to progress, weight-bearing activities may be restricted.
Diagnostic Studies The diagnosis of Morton’s neuroma is classically made clinically based on patient history and physical examination with sensitivity as high as 98%.8 Weight-bearing anteroposterior, oblique, and lateral foot radiographs can be obtained to rule out bony pathology. There is no relationship between
Rehabilitation If equinus contracture is found on exam, then the patient may benefit from a brief course of physical therapy with home stretching routine to reduce the forefoot overload. Postoperative patients are instructed to elevate the foot frequently above the level of the nose to improve swelling control and reduce tension across the incision. Often, the sensation of swelling and fullness persist for up to 6 months after surgery. Physical therapy may be helpful in gait training; however, for most patients, routine activities of daily living are sufficient to regain their strength.
Procedures Diagnostic and also therapeutic injection with 1% lidocaine with corticosteroid into the affected webspace can help isolate the source of pain. The clinician must ensure the proper
CHAPTER 91 Morton’s Neuroma
depth of the injection, as the lidocaine must traverse the transverse intermetatarsal ligament. Use isopropyl alcohol wipes to sanitize the dorsal and the plantar skin (in the event of accidental penetration of the plantar skin) while using a 25-gauge needle for foot and ankle injections to reduce the level of discomfort during the injection. Injections can be done in the clinic, with or without ultrasound, producing equivalent success rate11; 1 mL of 0.5% bupivacaine without epinephrine mixed with corticosteroid can be used. Short-term outcomes after injection are acceptable, while long-term results are highly variable. Although the relief can last for over 1 year in 30% of the patients, it should be used with caution. Several series demonstrated highly variable outcomes with concerns for sclerosing effects of the alcohol agents on local tissues beyond the nerve. Short-term pain relief ranges from 22% to 94% with 64% with recurrence of pain or electing surgical excision within 5 years.13,14 The use of capsaicin injections had been studied in a randomized, double-blind placebo-controlled trial in 58 patients with Morton’s neuroma with significant pain relief in the capsaicin group. No mid- or long-term follow up are available.15 Another study explored extracorporeal shockwave therapy (ESWT) in patients with Morton’s neuroma in a randomized trial. Compared to a sham stimulation procedure, ESWT showed promise in pain relief in the short term.16 One should be cautious when considering injections into the forefoot. Not enough long-term evidence exists to convince patients that benefits outweigh risks for serial alcohol sclerosing injections. Corticosteroid injection can be attempted with or without ultrasound as a diagnostic and therapeutic method and should not be repeated more frequently than every 3 months since they do not correlate with permanent pain resolution.1
Technology There is no specific technology for the treatment or rehabilitation of this condition.
Surgery Operative management of neurolysis versus neurectomy is offered to patients who failed nonoperative measures. Morton’s neuroma excision is the most common procedure (Fig. 91.3). Often surgeons prefer the dorsal approach to avoid development of plantar forefoot pain from scarring. The neuroma can be approached from the dorsal or plantar side of the nerve and is excised proximal to the bifurcation.17–20 Good to excellent results have been reported in 51% to 91% of patients. One study reported 78.8% good to excellent outcomes in 99 consecutive patients in the first prospective study to look at pre- and postsurgical patients who underwent neuroma excision; 63% of the patients reported being pain free at the final follow up.21 Another series of 41 patients who were treated for Morton’s neuroma with neurectomy reported an average follow up of 7.4 years; 76% of the patients had sustained pain relief.20 Another long-term study involving 120 patients who underwent operative neuroma excision showed a good or excellent rating in only 51% of the study population after an average of 66.7 months follow up.22 Neurolysis is another procedure that can be considered in select patients. In 50 patients (69 feet), the interdigital nerve
499
FIG. 91.3 Intraoperative specimen of an interdigital neuroma.
was examined at the time of surgery. If a nerve appeared to be bulbous and fibrotic, the nerve was excised whereas a nerve without macroscopic pseudoneuroma appearance was preserved after neurolysis. Preservation of the nerve and avoiding interdigital numbness can be an option if the nerve appears to be in good condition.23 Neurolysis can be combined with neurectomy in cases where adjacent webspace interdigital neuromas (i.e., second and third webspace neuromas) are suspected. Twenty-three patients with adjacent webspace neuromas were evaluated after excision of one nerve and neurolysis of the other; 95% at the end of their follow up reported satisfaction.24 Several studies looked at minimally invasive decompression procedures in patients with Morton’s neuroma with good short-term success and faster recovery than traditional open procedure. In a small series of 14 patients, 11/14 patients reported no recurrence of symptoms after minimally invasive decompression.25
Potential Disease Complications Potential disease complications include persistent refractory or intractable nerve pain, reduced mobility, functional limitation, and shoe-wear restrictions.
Potential Treatment Complications Steroid injection-associated complications include skin discoloration, infection, fat pad atrophy, and plantar plate and collateral ligament tears. Specific complications related to Morton’s neuroma excision include wound complications, digital vascular disruption, metatarsal stress fracture, crossover or hammertoe after injury to collateral ligaments, and persistent pain with stump neuroma. Some of the complications such as delayed healing and regional soft tissue damage are seen frequently in patients who received multiple corticosteroid and alcohol injections.
500
PART 1 MSK Disorders
References 1. Weinfeld SB, Myerson MS. Interdigital neuritis: diagnosis and treatment. J Am Acad Orthop Surg. 1996;4:328–335. 2. Bossley CJ, Cairney PC. The intermetatarsophalangeal bursa–its significance in Morton’s metatarsalgia. J Bone Joint Surg Br. 1980;62-B:184–187. 3. Ha’Eri GB, Fornasier VL, Schatzker J. Morton’s neuroma–pathogenesis and ultrastructure. Clin Orthop Relat Res. 1979:256–259. 4. Graham CE, Graham DM. Morton’s neuroma: a microscopic evaluation. Foot Ankle. 1984;5:150–153. 5. Ouzounian TJ, Shereff MJ. In vitro determination of midfoot motion. Foot Ankle. 1989;10:140–146. 6. Mann RA, Reynolds JC. Interdigital neuroma–a critical clinical analysis. Foot Ankle. 1983;3:238–243. 7. Owens R, Gougoulias N, Guthrie H, Sakellariou A. Morton’s neuroma: clinical testing and imaging in 76 feet, compared to a control group. Foot Ankle Surg. 2011;17:197–200. 8. Pastides P, El-Sallakh S, Charalambides C. Morton’s neuroma. A clinical versus radiological diagnosis. Foot Ankle Surg. 2012;18:22–24. 9. Naraghi R, Bremner A, Slack-Smith L, Bryant A. Radiographic analysis of feet with and without Morton’s neuroma. Foot Ankle Int. 2017;38(3):310–317. 10. Claassen L, Bock K, Ettinger M, Waizy H, Stukenborg-Colsman C, Plaass C. Role of MRI in detection of Morton’s neuroma. Foot Ankle Int. 2014;35:1002–1005. 11. Mahadevan D, Attwal M, Bhatt R, Bhatia M. Corticosteroid injection for Morton’s neuroma with or without ultrasound guidance: a randomised controlled trial. Bone Joint J. 2016;98-B:498–503. 12. Mahadevan D, Salmasi M, Whybra N, Nanda A, Gaba S, Mangwani J. What factors predict the need for further intervention following corticosteroid injection of morton’s neuroma? Foot Ankle Surg. 2016;22:9–11. 13. Gurdezi S, White T, Ramesh P. Alcohol injection for Morton’s neuroma: a five-year follow-up. Foot Ankle Int. 2013;34:1064–1067. 14. Hughes RJ, Ali K, Jones H, Kendall S, Connell DA. Treatment of Morton’s neuroma with alcohol injection under sonographic guidance: follow-up of 101 cases. AJR Am J Roentgenol. 2007;188:1535–1539.
15. Campbell CM, Diamond E, Schmidt WK, et al. A randomized, doubleblind, placebo-controlled trial of injected capsaicin for pain in Morton’s neuroma. Pain. 2016;157:1297–1304. 16. Seok H, Kim SH, Lee SY, Park SW. Extracorporeal shockwave therapy in patients with Morton’s neuroma a randomized, placebo-controlled trial. J Am Podiatr Med Assoc. 2016;106:93–99. 17. Akermark C, Crone H, Skoog A, Weidenhielm L. A prospective randomized controlled trial of plantar versus dorsal incisions for operative treatment of primary Morton’s neuroma. Foot Ankle Int. 2013;34: 1198–1204. 18. Killen MC, Karpe P, Limaye R. Plantar approach for Morton’s neuroma: an effective technique for primary excision. Foot (Edinb). 2015;25:232–234. 19. Kundert HP, Plaass C, Stukenborg-Colsman C, Waizy H. Excision of Morton’s neuroma using a longitudinal plantar approach: a midterm follow-up study. Foot Ankle Spec. 2016;9:37–42. 20. Reichert P, Zimmer K, Witkowski J, Wnukiewicz W, Kulinski S, Gosk J. Long-term results of neurectomy through a dorsal approach in the treatment of Morton’s neuroma. Adv Clin Exp Med. 2016;25: 295–302. 21. Bucknall V, Rutherford D, MacDonald D, Shalaby H, McKinley J, Breusch SJ. Outcomes following excision of Morton’s interdigital neuroma: a prospective study. Bone Joint J. 2016;98-B:1376–1381. 22. Womack JW, Richardson DR, Murphy GA, Richardson EG, Ishikawa SN. Long-term evaluation of interdigital neuroma treated by surgical excision. Foot Ankle Int. 2008;29:574–577. 23. Villas C, Florez B, Alfonso M. Neurectomy versus neurolysis for Morton’s neuroma. Foot Ankle Int. 2008;29:578–580. 24. Hort KR, DeOrio JK. Adjacent interdigital nerve irritation: single incision surgical treatment. Foot Ankle Int. 2002;23:1026–1030. 25. Zelent ME, Kane RM, Neese DJ, Lockner WB. Minimally invasive Morton’s intermetatarsal neuroma decompression. Foot Ankle Int. 2007;28: 263–265.