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Review of Morton's neuroma
The Foot (1995) 5,165-166 0 1995 Pearson Professional
REVIEW
Ltd
ARTICLE
Review of Morton’s neuroma M. Nashi, A. K Venkatachalam,
B. N. Muddu
Department of Orthopaedics, Tameside General Hospital, Fountain Street, Ashton under Lyne, UK
DEFINITION
AND ANATOMY
HISTOPATHOLOGY
In the early sta.ges there is venous congestion, endoneural and neural oedema, progressing to perineural, epineural and endoneural fibrosis and hypertrophy in late stages. Although these findings may be seen in normal digital nerves, axon demyelination is characteristic of Morton’s neuroma.13 A neuroma does not have to b’e particularly large or be present for a long time to cause painful symptoms. In long standing cases, the epineural thickening is more marked with partial replacement of nerve fibres by amorphous substance.‘”
Morton’s neuroma is an entrapment neuropathy of the plantar digital nerve which itself is a branch of the medial plantar nerve. The word neuroma is a misnomer as it suggests a benign tumour. It should be ideally called a peri-neural fibroma. The nerve passes plantar to the deep transverse intermetatarsal ligament. It is separated from the sole by the subcutaneous fat, plantar fascia and connective tissue compartments. A bursa is frequently found in association with the fibroma. Pacinian corpuscles are normally found in the subcutaneous tissue in this area1 and it is common to find multiple sensory branches diving plantarly from the nerve trunk.
AETIOLOGY
DIAGNOSIS
Intermetatarsal neuroma are classically found in females in the third intermetatarsal space. They are also seen frequently in the second but rarely in the first or fourth intermetatarsal space. The patient is usually between 40 and 60 years and is more likely to be overweight. Symptoms may be present from a few weeks to several years. Initially the patient may describe an odd sensation or lump in the toe. Later the pain may be sharp, dull but classically present as a paroxysmal burning sensation, like walking on a hot pebble. The pain is most often localized to the region of the third and fourth metatarsal heads and may radiate distally to the toes or proximally up the leg to the knee. Numbness in the third or fourth toes may be the presenting complaint but rarely is there any objective sensory deficit. In many cases, symptoms are triggered by some sort of trauma. The intermetatarsal spaces are often tender to direct plantar palpation. The thickened nerve can be rolled between the thumb and adjacent metatarsal heads when the toes are dorsiflexed. This may evoke pain. Dorsoplantar palpation of the affected intermetatarsal space with simultaneous side to side compression heads can reproduce the pain by directly trapping the neuroma.
AND BIOMECHANICS
Review of the literature leaves little doubt that this condition is an entrapment neuropathy.2-5 Degenerative changes occur as a result of compression and stress forces. The majority of neuromas occur in the pronated foot.6-8 Forces in this type of foot are not only due to excessive stretch of the interdigital nerves but also result from adjacent hypermobile metatarsal heads. During mid stance pronation, the foot is everted, abducted and dorsiflexed. This places a stretch on the nerve. This tension is increased as the nerve passes across the unyielding deep transverse intermetatarsal ligament. Further tension and compression will occur at this ligament when the toes dorsiflex at the metatarso-phalangeal joint.4,9m12
Correspondence to M. Nashi FRCS, Associate specialist, A. K. Venkatachalam, MS DNB, FRCS, Registrar B. N. Muddu FRCS(Ed), FRCS Orth(Ed), Mch Orth, Consultant, Tameside General Hospital Fountain Street. Ashton under Lyne OL6 9RW, UK. 165
166 The Foot Mulder’s click is a palpable and sometimes painful click elicited by compression of the metatarsal heads. Electra-physiological studies are in an early stage of development and may be clinically applicable in the near future.15 The differential diagnosis includes intermetatarsal bursitis, rheumatoid arthritis, osteochondritis dissecans of metatarsal heads, ischaemic pain, metabolic peripheral neuropathy, tarsal tunnel syndrome and metatarsal stress fractures.
TREATMENT Initial measures should be directed to reduce irritation of the neuroma. Wider shoes with good arch support and adequate toe room are advised. High heels should be avoided. Metatarsal pads may help. Injecting the painful neuroma with steroid or dilute alcohol in combination with a local anaesthetic also is useful. Conservative measures succeed in only 29-30% of symptomatic patients. With surgical intervention S-13% will have unsatisfactory results. SURGICAL
MANAGEMENT
There are four approaches described for access. Plantar longitudinal,10J6J7 plantar transverse, 16,17web splitting, 11,18and dorsal.igJO The two most commonly used techniques are the plantar longitudinal and the dorsal. Dorsal approach - the advantages are early ambulation since the incision is in a non-weightbearing surface. The disadvantages are those of difficulty in deep disection and necessity to sever the intermetatarsal ligament. There is greater potential for dead space and damage to neurovascular structure and lumbricals. Plantar approach - this is the second most common. The incision should be in the intermetatarsal space. It provides the best access to the neuroma and leaves the transverse intermetatarsal ligament intact. The disadvantage is a painful scar on the weightbearing surface. Both the digital branches and proximal nerve trunk and accessory branches should be severed to excise the neuroma. Dead space should be obliterated. Other measures include, neurolysiszl with division of the intermetatarsal ligament, release of intrinsic fibrosis and opening of the epineurium. The necessity of interdigital neurectomy has been questioned. In our prospective studyz2 55 neuromas in 52 patients were studied in two groups. Twenty-eight underwent excision by dorsal approach and 26 by
plantar. The average follow up was 3.1 years. Histology confirmed a neuroma in 51 patients. Results showed that in the dorsal group, weightbearing and return to work was faster and the duration of hospital stay was shorter than in the plantar group. There were five painful scars in the plantar group and two in the dorsal group.
REFERENCES
1. Goldman, F and Gardner, R. Pacinian corpuscles as a cause for metatarsalgia. J Am Podiatry Assoc 1982; 72: 135-141. 2. Ochoa, J. The primary nerve fibropathology of plantar neuromas. J Neuropathol Exp Neurol 1980; 70: 561. 3. Guilof, R J, Scadding J W. and Klenerman, L Morton’s metatarsalgia: clinical electrophysiological, and histological observations. J Bone Joint Sum 1984: 66B(4): 586-591. 4. Graham, C E and Graham, D-M. Morton’s’neuroma: A microscopic evaluation. Foot Ankle 1984; 5(2): 150-153. 5. Alexander I J, Johnson, K A and Parr, J W. Morton’s neuroma: A review of recent concepts. Orthopaedics, 1987; 10(l): 102-106. 6. Pincus, A. Intractable Morton’s toe (neuroma). Review of the literature and report of cases.J Am Podiatry Assoc 1950; 40: 19-35. 7. Tate, R 0 and Rusin, J J. Morton’s neuroma: Its ultrastructural anatomy and biomechanical etiology. J Am Podiatry Assoc 1978; 68: 797. 8. Bartolomei, F J and Wertheimer, S J. Intermetarsal neuromas: distribution and etiologic factors. J Foot Surg 1983; 22: 279-292. 9. Kravette, M A. Peripheral nerve entrapment syndromes in the foot. J Am Podiatry Assoc 1971; 61: 451472. 10. Bickel, V H and Dockerty, M B. Plantar neuromas, Morton’s toe. Surg Gynecol Obstets 1947; 84: 111. 11. McElvenny, R T. The etiology and surgical treatment of intractable pain about the fourth metatarsophalangeal joint (Morton’s toe). J Bone Joint Surg 1943; 25: 675. 12. Wachter S, Nilson R Z and Thul, J R. The relationship between foot structure and intermetarsal neuromas. J Foot Surg 1984; 23(6): 436439. 13. Bourke G, Owen, J and Machet D. Histological comparison of the third interdigital nerve in patients with Morton’s metatarsalgia and control patients. Aust N Z J Surg 1994; 64(6): 421424. 14. De Palma L, Tulli A. La maladie de Morton: observations en microscopic optique et electronique. Acta Orth Belg (Belgium) 1991; 57(3): 285-95. 15. Alexander I J. Johnson K A., Parr J W. Morton’s neuroma: a review of recent concepts. Orthopaedics 1987; 10(l): 103-106. 16. Betts, L 0. Morton’s metatarsalgia. Med J Aust 1940; 1: 514. 17. Kaplan, E B. Surgical approach to the plantar digital nerves. Bull Hosp Joint dis Orthop Inst 1950; l(1): 9697. 18. Joplin R J. Some common foot disorders amenable to surgery. AAOS Instructional course lectures 1958; 15: 144. 19. KcKeever D C. Surgical approach for neuroma of plantar digital nerve (Morton’s metatarsalgia). J Bone Joint Surg 1952; 34: 490. 20. Kitting R W and McGlamry, E D Removal of an intermetarsal neuroma. J Am Podiatry Assoc 1973; 63: 274. 21. Dellon, A L. The tratment of Morton’s neuroma as a nerve compression. The role for neurolysis. J Am Podiatry Med Assoc 1992; 82(8): 3999402. 22. Nashi M, Muddu B N. Review of Morton’s neuroma at 13th annual meeting of British Orthopaedic foot surgeons, l&l 1 Nov 1994.
REVIEW
Ltd
ARTICLE
Review of Morton’s neuroma M. Nashi, A. K Venkatachalam,
B. N. Muddu
Department of Orthopaedics, Tameside General Hospital, Fountain Street, Ashton under Lyne, UK
DEFINITION
AND ANATOMY
HISTOPATHOLOGY
In the early sta.ges there is venous congestion, endoneural and neural oedema, progressing to perineural, epineural and endoneural fibrosis and hypertrophy in late stages. Although these findings may be seen in normal digital nerves, axon demyelination is characteristic of Morton’s neuroma.13 A neuroma does not have to b’e particularly large or be present for a long time to cause painful symptoms. In long standing cases, the epineural thickening is more marked with partial replacement of nerve fibres by amorphous substance.‘”
Morton’s neuroma is an entrapment neuropathy of the plantar digital nerve which itself is a branch of the medial plantar nerve. The word neuroma is a misnomer as it suggests a benign tumour. It should be ideally called a peri-neural fibroma. The nerve passes plantar to the deep transverse intermetatarsal ligament. It is separated from the sole by the subcutaneous fat, plantar fascia and connective tissue compartments. A bursa is frequently found in association with the fibroma. Pacinian corpuscles are normally found in the subcutaneous tissue in this area1 and it is common to find multiple sensory branches diving plantarly from the nerve trunk.
AETIOLOGY
DIAGNOSIS
Intermetatarsal neuroma are classically found in females in the third intermetatarsal space. They are also seen frequently in the second but rarely in the first or fourth intermetatarsal space. The patient is usually between 40 and 60 years and is more likely to be overweight. Symptoms may be present from a few weeks to several years. Initially the patient may describe an odd sensation or lump in the toe. Later the pain may be sharp, dull but classically present as a paroxysmal burning sensation, like walking on a hot pebble. The pain is most often localized to the region of the third and fourth metatarsal heads and may radiate distally to the toes or proximally up the leg to the knee. Numbness in the third or fourth toes may be the presenting complaint but rarely is there any objective sensory deficit. In many cases, symptoms are triggered by some sort of trauma. The intermetatarsal spaces are often tender to direct plantar palpation. The thickened nerve can be rolled between the thumb and adjacent metatarsal heads when the toes are dorsiflexed. This may evoke pain. Dorsoplantar palpation of the affected intermetatarsal space with simultaneous side to side compression heads can reproduce the pain by directly trapping the neuroma.
AND BIOMECHANICS
Review of the literature leaves little doubt that this condition is an entrapment neuropathy.2-5 Degenerative changes occur as a result of compression and stress forces. The majority of neuromas occur in the pronated foot.6-8 Forces in this type of foot are not only due to excessive stretch of the interdigital nerves but also result from adjacent hypermobile metatarsal heads. During mid stance pronation, the foot is everted, abducted and dorsiflexed. This places a stretch on the nerve. This tension is increased as the nerve passes across the unyielding deep transverse intermetatarsal ligament. Further tension and compression will occur at this ligament when the toes dorsiflex at the metatarso-phalangeal joint.4,9m12
Correspondence to M. Nashi FRCS, Associate specialist, A. K. Venkatachalam, MS DNB, FRCS, Registrar B. N. Muddu FRCS(Ed), FRCS Orth(Ed), Mch Orth, Consultant, Tameside General Hospital Fountain Street. Ashton under Lyne OL6 9RW, UK. 165
166 The Foot Mulder’s click is a palpable and sometimes painful click elicited by compression of the metatarsal heads. Electra-physiological studies are in an early stage of development and may be clinically applicable in the near future.15 The differential diagnosis includes intermetatarsal bursitis, rheumatoid arthritis, osteochondritis dissecans of metatarsal heads, ischaemic pain, metabolic peripheral neuropathy, tarsal tunnel syndrome and metatarsal stress fractures.
TREATMENT Initial measures should be directed to reduce irritation of the neuroma. Wider shoes with good arch support and adequate toe room are advised. High heels should be avoided. Metatarsal pads may help. Injecting the painful neuroma with steroid or dilute alcohol in combination with a local anaesthetic also is useful. Conservative measures succeed in only 29-30% of symptomatic patients. With surgical intervention S-13% will have unsatisfactory results. SURGICAL
MANAGEMENT
There are four approaches described for access. Plantar longitudinal,10J6J7 plantar transverse, 16,17web splitting, 11,18and dorsal.igJO The two most commonly used techniques are the plantar longitudinal and the dorsal. Dorsal approach - the advantages are early ambulation since the incision is in a non-weightbearing surface. The disadvantages are those of difficulty in deep disection and necessity to sever the intermetatarsal ligament. There is greater potential for dead space and damage to neurovascular structure and lumbricals. Plantar approach - this is the second most common. The incision should be in the intermetatarsal space. It provides the best access to the neuroma and leaves the transverse intermetatarsal ligament intact. The disadvantage is a painful scar on the weightbearing surface. Both the digital branches and proximal nerve trunk and accessory branches should be severed to excise the neuroma. Dead space should be obliterated. Other measures include, neurolysiszl with division of the intermetatarsal ligament, release of intrinsic fibrosis and opening of the epineurium. The necessity of interdigital neurectomy has been questioned. In our prospective studyz2 55 neuromas in 52 patients were studied in two groups. Twenty-eight underwent excision by dorsal approach and 26 by
plantar. The average follow up was 3.1 years. Histology confirmed a neuroma in 51 patients. Results showed that in the dorsal group, weightbearing and return to work was faster and the duration of hospital stay was shorter than in the plantar group. There were five painful scars in the plantar group and two in the dorsal group.
REFERENCES
1. Goldman, F and Gardner, R. Pacinian corpuscles as a cause for metatarsalgia. J Am Podiatry Assoc 1982; 72: 135-141. 2. Ochoa, J. The primary nerve fibropathology of plantar neuromas. J Neuropathol Exp Neurol 1980; 70: 561. 3. Guilof, R J, Scadding J W. and Klenerman, L Morton’s metatarsalgia: clinical electrophysiological, and histological observations. J Bone Joint Sum 1984: 66B(4): 586-591. 4. Graham, C E and Graham, D-M. Morton’s’neuroma: A microscopic evaluation. Foot Ankle 1984; 5(2): 150-153. 5. Alexander I J, Johnson, K A and Parr, J W. Morton’s neuroma: A review of recent concepts. Orthopaedics, 1987; 10(l): 102-106. 6. Pincus, A. Intractable Morton’s toe (neuroma). Review of the literature and report of cases.J Am Podiatry Assoc 1950; 40: 19-35. 7. Tate, R 0 and Rusin, J J. Morton’s neuroma: Its ultrastructural anatomy and biomechanical etiology. J Am Podiatry Assoc 1978; 68: 797. 8. Bartolomei, F J and Wertheimer, S J. Intermetarsal neuromas: distribution and etiologic factors. J Foot Surg 1983; 22: 279-292. 9. Kravette, M A. Peripheral nerve entrapment syndromes in the foot. J Am Podiatry Assoc 1971; 61: 451472. 10. Bickel, V H and Dockerty, M B. Plantar neuromas, Morton’s toe. Surg Gynecol Obstets 1947; 84: 111. 11. McElvenny, R T. The etiology and surgical treatment of intractable pain about the fourth metatarsophalangeal joint (Morton’s toe). J Bone Joint Surg 1943; 25: 675. 12. Wachter S, Nilson R Z and Thul, J R. The relationship between foot structure and intermetarsal neuromas. J Foot Surg 1984; 23(6): 436439. 13. Bourke G, Owen, J and Machet D. Histological comparison of the third interdigital nerve in patients with Morton’s metatarsalgia and control patients. Aust N Z J Surg 1994; 64(6): 421424. 14. De Palma L, Tulli A. La maladie de Morton: observations en microscopic optique et electronique. Acta Orth Belg (Belgium) 1991; 57(3): 285-95. 15. Alexander I J. Johnson K A., Parr J W. Morton’s neuroma: a review of recent concepts. Orthopaedics 1987; 10(l): 103-106. 16. Betts, L 0. Morton’s metatarsalgia. Med J Aust 1940; 1: 514. 17. Kaplan, E B. Surgical approach to the plantar digital nerves. Bull Hosp Joint dis Orthop Inst 1950; l(1): 9697. 18. Joplin R J. Some common foot disorders amenable to surgery. AAOS Instructional course lectures 1958; 15: 144. 19. KcKeever D C. Surgical approach for neuroma of plantar digital nerve (Morton’s metatarsalgia). J Bone Joint Surg 1952; 34: 490. 20. Kitting R W and McGlamry, E D Removal of an intermetarsal neuroma. J Am Podiatry Assoc 1973; 63: 274. 21. Dellon, A L. The tratment of Morton’s neuroma as a nerve compression. The role for neurolysis. J Am Podiatry Med Assoc 1992; 82(8): 3999402. 22. Nashi M, Muddu B N. Review of Morton’s neuroma at 13th annual meeting of British Orthopaedic foot surgeons, l&l 1 Nov 1994.