This article deals with the classification, assessment, and management of painful nerves of the distal upper limb. The author’s preferred surgical and rehabilitation techniques in managing these conditions are discussed in detail and include (1) relocation of end-neuromas to specific sites, (2) division and relocation of painful nerves in continuity (neuromas-in-continuity and scar-tethered nerves) involving small nerves to the same sites, and (3) fascial wrapping of painful nerves in continuity involving larger nerves such as the median and ulnar nerves. The results of these treatments are presented as justification for current use of these techniques.
Key points
- •
Common causes of peripheral nerve pain include end-neuromas, neuromas-in-continuity, and scar-tethered nerves.
- •
In the author’s practice, nerve relocations to appropriate proximal bone or muscle sites relieve pain in 80% to 90% of end-neuroma cases.
- •
Painful small peripheral nerves in continuity (neuromas-in-continuity and scar-tethered nerves) are best treated by division of the nerve and relocation to bones or muscles. The loss of distal sensation is of minimal consequence.
- •
Many painful median and ulnar nerves in continuity can be given useful pain relief by wrapping them in local vascularized fascial flaps from the forearm. Division of these nerves is not recommended for obvious reasons.
- •
Neuromas-in-continuity of the large nerves such as the median nerve at the wrist can be helped by coverage with distant flaps from the groin, abdomen, or buttock containing thick subcutaneous fat. Distant muscle flaps should not be used, because the muscle atrophies and shrinks.
Introduction
It is said that there are more than 150 surgical methods of relieving end-neuroma pain described in the literature. Achieving personal experience of more than a few of these methods is unlikely for any single surgeon, because end-neuroma pain is an uncommon complication in most surgical practices. To summarize one’s experience of a few is also difficult and, to some extent pointless, because the process of learning in this field is long and is usually one of trial and rejection until a technique evolves that achieves a modicum of success. Therefore, in this review, the author has chosen to provide a summary of his current, and most successful, surgical means of dealing with the pathology of neuroma pain.
Except for the nerve compression syndromes, severe pain in the peripheral nervous system is caused by 3 pathologic entities, namely:
- 1.
End-neuromas
- 2.
Neuromas-in-continuity
- 3.
Scar-tethered nerves
The cause of the pain in scar-tethered nerves is the most elusive. These patients have only had an injury adjacent to a nerve, which has then become incorporated in the scar tissue formed in the area as part of the healing process.
Distal sensation is the end point of most of our treatments of the sensory nerves. However, when nerve pain supervenes after injury, it can become the function-limiting problem, and pain relief may have to take priority over restoration, or maintenance, of distal sensory function. This treatment may even require sacrifice of distal sensation for pain control.
Introduction
It is said that there are more than 150 surgical methods of relieving end-neuroma pain described in the literature. Achieving personal experience of more than a few of these methods is unlikely for any single surgeon, because end-neuroma pain is an uncommon complication in most surgical practices. To summarize one’s experience of a few is also difficult and, to some extent pointless, because the process of learning in this field is long and is usually one of trial and rejection until a technique evolves that achieves a modicum of success. Therefore, in this review, the author has chosen to provide a summary of his current, and most successful, surgical means of dealing with the pathology of neuroma pain.
Except for the nerve compression syndromes, severe pain in the peripheral nervous system is caused by 3 pathologic entities, namely:
- 1.
End-neuromas
- 2.
Neuromas-in-continuity
- 3.
Scar-tethered nerves
The cause of the pain in scar-tethered nerves is the most elusive. These patients have only had an injury adjacent to a nerve, which has then become incorporated in the scar tissue formed in the area as part of the healing process.
Distal sensation is the end point of most of our treatments of the sensory nerves. However, when nerve pain supervenes after injury, it can become the function-limiting problem, and pain relief may have to take priority over restoration, or maintenance, of distal sensory function. This treatment may even require sacrifice of distal sensation for pain control.
A language to discuss nerve pain
Description of Pain
For the patient, pain is usually a complex of unpleasant symptoms, for which we do not have a simple language whereby we can communicate with patients, or among ourselves, and record our treatments. It has been our experience that patients complain of variable degrees of 4 problems, namely:
- 1.
Spontaneous pain
- 2.
Pressure pain
- 3.
Movement pain
- 4.
Hypersensitivity or unpleasant skin sensation to light touch
The latter may give rise to considerable morbidity. It embraces hyperesthesia, hyperpathia and allodynia, all of which have slightly different meanings.
The association of cause and effect is most obvious for pressure pain, or tenderness, and movement pain, elicited by movement of adjacent tendons and joints. When present, hypersensitivity usually affects the skin directly overlying the involved part of the nerve. The most poorly understood and unpleasant of all these pains is that of spontaneous pain, which is almost invariably present. This pain is most often a continuous aching, or basal spontaneous pain, punctuated by spikes of increased intensity of pain, or spiking spontaneous pain, which are often severe, occur with variable frequency, and may be associated with reflex motor activity, causing the whole upper limb to jerk. It wears down the resolve of the patient and cannot be avoided without medical help. In itself, it is probably enough to create the character changes that make us speculate whether nerve pain problems occur in those who are mentally predisposed.
Documentation of the Degree of Pain
Any assessment of pain is inevitably subjective. Although pain charts scoring pain from 0 to 10, or 0 to 5, create an impression of science, these remain based on the patient’s opinion. Patients often find it difficult to understand this scoring, and we have found it quicker in busy clinics to score each pain as severe, moderate, mild, or none. If required, this scoring can be translated into numbers for research purposes.
The symptomatic end point of the 3 nerve pathologies is surprisingly similar, allowing for use of the same system of recording and assessing the degree to which each of the types of pain is present. A table can be created to assess the initial problem and the achievement of treatment ( Table 1 ).
| Primary Site | Secondary Site | |||
|---|---|---|---|---|
| Preoperative | Postoperative | Preoperative | Postoperative | |
| Spontaneous Pain | ||||
| Baseline | Moderate | Nil | — | Nil |
| Spikes | Severe 4 times a day | Nil | — | Nil |
| Pressure Pain | Severe | Nil | — | Nil |
| Movement Pain | Severe a | Nil | — | Mild b |
| Hyperesthesia | Moderate | Nil | — | Nil |
a Severe pain on any movement of the wrist and on any movement of the long extensor tendons of the little finger.
b Mild pain at the extremes of wrist extension and supination only.
Preoperative discussion and local anesthetic assessment
It is important to explain the cause of the pain, the concept of relocation of the nerve end, and the reasoning behind the particular choice of relocation site to the patient. This strategy requires the surgeon to know the basic nerve anatomy of all of the cutaneous nerves in the locality of the neuroma pain and to be aware where several nerves may be involved and where anatomic variation can occur. Patients should be warned that it may be necessary to perform more than 1 operation to achieve maximum benefit from local surgery.
Excepting those patients with needle phobia, it is usually possible to identify the nerve(s) innervating a site of pain by local anesthetic injections. For a variety of reasons, including the operator’s knowledge of nerve anatomy, their skill in placing the needle exactly beside the nerve to be blocked, the thickness of the subcutaneous fat, and anatomic variations, this is an imprecise activity and the results should be interpreted with caution. We use 2% lignocaine for these blocks, because it is more rapid in its onset and requires smaller doses, making independent blocking of individual nerves that are anatomically close more likely.
Decision on proper surgical methods
The ideal treatment of a cut nerve is to reconnect the nerve ends in the hope of restoring function and to contain axonal sprouting, so avoiding end-neuroma pain. Only occasionally after nerve reconnection does a neuroma-in-continuity or sufficient scar tethering of the nerve repair occur, causing pain. This situation most commonly follows repair of the superficial radial nerve in the distal forearm or of the radial digital nerve of the index finger at the radial end of the distal palmar crease. When a nerve division is first seen many weeks or months after injury, the nerve ends have retracted. Any end-neuroma bulb must be resected, and the nerve gap is sometimes greater than can be bridged by advancing the 2 nerve ends. For short nerve gaps in nerves in which distal sensory recovery is not essential, a short segment of vein graft is often a convenient compromise.
However, we sometimes have to make a decision not to reconnect a divided nerve. This is usually a complex and multifactorial decision. Local anatomic reasons may make reconnection of the nerve impossible or likely to achieve neither improvement of distal function nor relief of the end-neuroma nerve pain. Other factors, such as the patient’s wishes, their age, and so forth, bear on the decision. Relocation of the proximal nerve end is often advisable if the nerve end is already painful or the area is already densely scarred. Nerve reconnection is not advisable under these circumstances, because it may progress to nerve tethering and further pain. We consider the latter the worse of the 2 problems to treat. For most nerves other than the median or ulnar nerves, we wound convert the scarred nerve to a cut nerve and then relocate it proximally. After nerve reconnection of a painful proximal nerve end, advancing sensation may be accompanied by advancing nerve pain. This rare complication has no local surgical solution when it occurs after median and ulnar nerve repair. However, for smaller nerves, it can be reversed by division of the nerve again and relocation of the proximal end.
Free tissue transfers and some local hand flaps can provide a cut peripheral nerve with a distal segment of nerve and its nerve to skin connections. This factor is particularly useful as treatment of proximal amputations that have developed end-neuroma pain. The problem of advancing pain as the recovering nerve grows distally can occur under these circumstances, even if rarely.
Surgical treatment of end-neuromas
Relocation: Indications and Procedures
We have tried several of the many treatments for end-neuromas in the literature, many of which are included in Sunderland’s book Nerves and Nerve Injuries . Treatments that we have not found successful include (1) wrapping nerve ends in foreign materials, (2) wrapping nerve ends in vascularized fat flaps, and (3) splitting the nerve to allow suture of the 2 parts as a loop and relocation to certain sites. There is surprisingly little in the literature about nerve relocation of end-neuromas of the peripheral nerves of the upper limb, but what has been written is specific with regard to the usefulness of different relocation sites for the nerves more commonly affected. Simply relocating the nerve end a little way proximally into fat also sometimes relieves the problem, but, often, it does not move the end-neuroma far enough from the repeated minor trauma of daily hand use.
Our current treatment of all end-neuromas (and many painful nerves in continuity), with an experience of more than 350 patients, is relocation of all cut nerve ends to specific proximal and deeper sites. This particular treatment is based on the premise that, even if the end-neuroma is to remain with the patient forever, it can usually be placed somewhere where it is traumatized less and, so, be a less significant source of pain. We have found that proximal relocation of nerve ends, almost invariably, also reduces, or eliminates, spontaneous pain and hypersensitivity. The physical act of moving the nerve end, by releasing the nerve end from tension at the site of the original injury, by environmental change or, even, by biochemical changes may explain the reduction of spontaneous pain.
- •
The distal part of the upper limb, which is most likely to sustain nerve injury, can be usefully split into 3 zones ( Fig. 1 ), based in part on the anatomic sites at which the nerves have been divided and partly on the appropriate site for relocation of the particular nerve ends.
Fig. 1
Zones of the hand as a guide to relocation of end-neuromas of the hand and wrist.
- •
Zone I includes all the digital nerve injuries beyond the distal palmar crease.
- •
Zone II includes nerves in the proximal palm, the dorsum of the hand, and the wrist.
- •
Zone III includes the forearm cutaneous nerves.
Zone I (Digital Nerves)
The digital nerve involved in nerve pain may be obvious. If not, local anesthetic injection in small volumes at the base of the finger indicates the relative involvement of the 2 nerves.
The innervation of the dorsal skin of a digit may also contribute to end-neuroma pain in the digit, particularly at an amputation stump. When the bone of a distal amputation stump has been covered by the dorsal skin, this may be the only source of pain at the stump. The dorsal innervation from the hand may extend to the nail base of, particularly, the thumb, index, and little fingers. This innervation demands particular consideration when dealing with finger amputations at, and proximal to, the proximal interphalangeal joint, with injury to the dorsum of the thumb at any level and after index finger ray amputations. In these cases, neuroma pain may develop on the dorsum of the first web space. The contribution of branches of the dorsal hand innervation can be assessed by dorsal local anesthetic block at the metacarpophalangeal (MCP) joint level, or on the dorsum of the hand, according to the level of injury.
Relocation of digital nerves
We have relocated the main digital nerves on a few occasions and found the finger to be only partially relieved of pain. Further attention to the dorsal nerves at the base of the finger has relieved the remaining problem of pain in the digit. On 2 such occasions, we have found very small branches of the dorsal nerves at the base of the proximal phalanx running around the lateral surface of the proximal phalanx and, presumably, contributing to the innervation of the palmar surface of the finger. Having already scarred the finger by previously relocating the main digital nerves, we were not in a position to determine whether these very small nerve branches connected with the main digital nerves or their dorsal branches, as previously shown anatomically.
Burying nerve ends in bone
The concept of burying nerve ends in bone is not new. Two good studies have shown that burying digital nerve ends in either the lateral surface of the phalangeal bones or in the metacarpal bones dorsolaterally is effective, and this has been our experience. Burying the nerve ends 1 phalanx back from the site of amputation, or nerve injury, to minimize the numb area distally is often ineffective. The possibility of branches of the dorsal skin of the amputation stump being the source of the end-neuromas has already been mentioned. The relocated digital nerve end may also continue to be traumatized, because it is still too close to the end of the digit. The digital tip, or stump, may remain innervated and painful, because the small nerve branches innervating the skin of the palmar surface of each phalangeal segment leave the main digital nerve proximal to that segment, and moving the main trunk of the digital nerve back by only 1 phalangeal segment may not relocate these branches. Therefore, we relocate the main digital nerve ends 2 phalangeal segments proximally. End-neuromas of the digital nerves injured around, or distal to, the distal interphalangeal joint are relocated into bone holes in the lateral surface of the proximal part of the proximal phalanx, as close to the web space as possible ( Fig. 2 ). More proximal end-neuromas, in shortened digits, are taken back into the palm, through the interosseous muscles, and relocated into drill holes in the dorsolateral surfaces of the metacarpal bones ( Fig. 3 ).
Nerve tenderness after nerve relocation
Several relocations into the lateral aspect of the proximal phalanx remain tender. A few are uncomfortable where the nerve crosses the edge of the drill hole into the bone on closing the fingers together. We now routinely bevel the edge of all bone holes where the nerve crosses, but this problem still occurs occasionally. A few cases also remain irritated by full extension of the MCP joints as if tethered too tightly to accommodate this movement. Nevertheless, we are reluctant to carry out the degree of proximal dissection necessary for a metacarpal relocation, with the potential problems of this relocation site, in cases with very distal nerve injury or amputation. When a problem arises after proximal phalangeal relocation, we re-relocate the nerve end to the metacarpal site at a subsequent operation.
Surgical procedure
Relocation of nerves into dorsolateral metacarpal site
- •
To relocate the digital nerves into the dorsolateral metacarpal site, the nerve is dissected back to the midpalm, if necessary splitting the nerve from its companion in the common digital nerve.
- •
About 1 cm distal to the superficial palmar arch, an artery clip is then passed through the interosseous muscles, alongside the bone of the metacarpal of the finger to which the digital nerve belongs, in a palmar to dorsal direction.
- •
The dorsal skin is incised where the point of the artery clip is palpated.
- •
The dorsal incision is deepened past the extensor tendons.
- •
The periosteum is cut longitudinally for approximately 2 cm along the edge of the dorsal interosseous muscle attachment and the muscle separated from the bone.
- •
A drill hole of slightly greater diameter than the digital nerve is made as far as possible down the lateral surface of the metacarpal bone ( Fig. 4 ), and the palmar edge of this hole is beveled.
Fig. 4
The typical shape of bone hole ( red ) made in the side wall of the metacarpal (in this instance, on the ulnar side of the left ring finger metacarpal) to allow the nerve to move in a palmar direction and away from the dorsum of the hand. The palmar edge of the hole ( green ), is beveled so the nerve does not cross a sharp edge.
- •
After drilling the bone hole, a second artery clip is passed in the opposite direction, from dorsal to palmar, to draw the nerve through to the relocation site.
Surgical Note: There is a risk of catching the nerve in the drill and avulsing it if the nerve is lying adjacent to the drill when making the bone hole.
- •
The nerve is then cut to an appropriate length to allow the end to sit about 3 to 4 mm inside the metacarpal. Care is taken to leave the nerve loose at the point in the palm at which it turns dorsally into the interosseous muscle.
- •
The nerve is sutured to the periosteum of the bone with 2 6/0 nylon sutures and the interosseous muscle lifted over the nerve onto the dorsal surface of the metacarpal and sutured to the dorsal periosteum, to provide added protection.
Outcomes of digital nerve relocation
Our experience of relocating 104 digital nerves in zone I using these techniques has been reported, and the final pain scores are shown in Table 2 . Seventy of the neuromas settled after a single relocation, whereas the remainder required a second relocation. After either of these relocations, the spontaneous pain usually also diminishes, and frequently, disappears. This process often occurs quickly but, occasionally, needs drug treatment of a few weeks or months to reduce spikes of pain.
| Type of Pain | Original Site | Relocation Site | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Preoperative | Postoperative | Postoperative | ||||||||||
| Severe | Mod | Mild | None | Severe | Mod | Mild | None | Severe | Mod | Mild | None | |
| 12 | 45 | 9 | 38 | 0 | 0 | 0 | 104 | 0 | 0 | 12 | 92 |
| 56 | 8 | 2 | 38 | 0 | 0 | 0 | 104 | 0 | 2 | 4 | 88 |
| Pressure | 92 | 10 | 0 | 2 | 0 | 0 | 2 | 102 | 4 a | 13 | 26 | 61 |
| Movement | 28 | 40 | 0 | 36 | 0 | 0 | 0 | 104 | 2 b | 2 | 9 | 91 |
| Hypersensitivity | 29 | 35 | 12 | 28 | 0 | 0 | 0 | 104 | 0 | 5 | 7 | 92 |
a On applying pressure at the relocation site in 2 patients with 2 relocations each to pronator quadratus.
b One patient with 2 relocations to pronator quadratus at extremes of supination and wrist extension only.
Although the nerve end is inside bone, it is never possible to place the nerve far enough from the dorsal surface of the metacarpal. It is common for the relocated nerve end at this site to remain tender to direct pressure from an examining finger for many months and, sometimes, indefinitely (see Table 2 ). However, the degree of pain experienced is considerably reduced for most patients, because the daily frequency with which a nerve end on the dorsum of the hand is traumatized is less than on the digits.
In a few patients whose work involves passing the hand into narrow spaces, and in some other heavy manual workers, this relocation site is not satisfactory in achieving a reduction of pressure pain, because they traumatize the site of relocation too often each day. In such patients, the nerve ends are better relocated to the pronator quadratus muscle. This is the second option for those nerve ends that do not settle in the dorsal metacarpal site. At the metacarpal site, the nerve end is only occasionally stimulated by movement of the extensor tendons to a degree that it remains a problem (see Table 2 ). Relocation to the pronator quadratus site is, again, the most satisfactory option of treatment in these circumstances. An occasional problem of the metacarpal relocation site has been scar tethering, with pain, at the site in the palm at which the nerve turns to pass through to the dorsum of the hand. This situation prevents tight gripping into the palm, even if the nerve end is comfortable on the dorsum of the hand. We have also treated this condition by secondary relocation to the pronator quadratus muscle. An occasional complication is scar tethering of the dorsal nerves, where the dorsal dissection down to the metacarpals must pass between their branches.
As a result of the problems related to the dorsolateral metacarpal relocation site, and to reduce the dissection, we have recently been trialing relocation into the lateral aspect of the metacarpal from the palmar side. The preliminary results have been encouraging, but this procedure needs further validation before advising a change to this new technique. This is not a return to the earlier practice of burying the nerve end in the small muscles on the palmar surface of the hand, including the thenar and hypothenar eminences, which is unsuccessful, because gripping onto the nerve ends in these sites during routine hand function activates the nerves too often and causes pain.
We are reluctant to use the pronator quadratus site as the routine relocation site for zone I cases because the dissection is longer and more complicated, and the other sites have mostly served us well. Relocation to the pronator quadratus requires an intrafascicular dissection of the involved fascicles from the main trunk of the median or ulnar nerve where they pass through the carpal tunnel or Guyon canal. We remain nervous that this procedure may cause scarring of the main trunk and may give rise to further pain problems. This outcome has not occurred with this dissection of the median nerve, but dissection of fascicles through the body of the ulnar nerve occasionally leaves troublesome hypersensitivity of the hypothenar eminence.
Although we have no experience of placing digital end-neuromas subcutaneously on the dorsal surface of the digits, we have had several of these relocations from the tip of the finger onto the dorsal surface of the middle phalanx referred to us with ongoing pain. These patients have commented that the relocated nerve ends are traumatized as often at the new site as on the palmar side of the tip of the digit, and the finger still remains sufficiently painful to preclude normal use of the hand. We, also, have no experience of placing end-neuromas in the soft tissues on the dorsal surface of the web spaces or in the soft tissues between the metacarpals.
Zone I (Dorsal Innervation of the Digits)
Any problems resulting from the dorsal branches of the digital nerves can be eliminated by relocating these with the main digital nerves as a routine. As one dissects the main digital nerve proximally in the finger, the dorsal branch is also taken proximally, the junction of the 2 being obvious, although variably situated between the palm and the midproximal phalangeal level, in the finger.
When appropriate, branches of the dorsal hand innervation running into any digit ( Fig. 5 ) can be relocated to a bone hole in the dorsolateral aspect of one of the metacarpals, or to the pronator quadratus (for branches of the dorsal branch of ulnar nerve), or to the brachioradialis muscle (for branches of the superficial radial nerve) ( Fig. 6 ).
Zone I (Ray Amputations)
When performing proximal finger and ray amputations, it is useful to dissect the digital nerves from as far distally as possible before removing the finger, to provide sufficient nerve length for relocation to the chosen site. Although classic teaching is to pass the digital nerves into the end of the metacarpal bone stump of ray amputations of the index and little fingers, this may cause pain on gripping if the nerves are pinched against the edge of the metacarpal. We now, routinely, relocate the digital nerves during these ray amputations into a drill hole in the blind side of the metacarpal remnant as far back as possible from the cut end of the bone. It is our custom to remove the whole of the metacarpal in ray amputations of the middle and ring fingers. In these cases, we bury the digital nerves in bone holes in the adjacent metacarpal bones.
Successful treatment of digital end-neuromas requires decisions concerning both the nerves that are in need of relocation and the appropriate site(s) for relocation. The initial operation may not be wholly successful, and the goal (of eliminating pain) may not be achieved by a single operation. It is a good maxim to believe the patient when the first operation fails, or only partly relieves the pain at the primary site. Local injection studies usually confirm that the patient is telling the truth. A second relocation often relieves the problem completely. With perseverance and awareness of the local neuroanatomy and by variable use of the 3 sites of relocation described earlier, it is possible to either cure the pain entirely or reduce the pain to tolerable levels, in 80% to 90% of digital nerve end-neuromas (see Table 2 ). When some pain remains, most patients tolerate this, rather than continue drug treatment on a long-term basis.
The problems of even a completely denervated finger are minimal, while the benefits of complete, or near complete, pain relief are enormous in restoring function of the whole hand.
Zone II
Successful relocation to the pronator quadratus site, deep on the flexor aspect of the distal forearm, was first used by Evans and Dellon to treat 13 end-neuromas of the palmar cutaneous branch of the median nerve. We adopted the technique for relocation of end-neuromas of short true digital and common digital nerves ( Fig. 7 ) and of the dorsal branch of the ulnar nerve. Our experience of relocating 33 nerves in zone II in 33 patients with an 80% to 90% success rate has been reported, and the results are shown in Table 3 . This procedure remains our first treatment option for zone II nerves. In our classification of the zones of nerve injury, we conceived the boundary of zones I and II as that point proximal to which the true digital nerves became too short to allow relocation to the dorsolateral surface of the metacarpals. This definition may have to be revisited if relocation into the lateral aspect of the metacarpals from the palmar side proves successful.
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