Introduction
Severe, intractable pain in the peripheral nervous system is caused by three local pathological entities, viz. end neuromas, neuromas in continuity, and scar-tethered nerves, with the symptoms being similar for all three pathologies. This unpleasant and life-changing condition mostly occurs as a consequence of trauma or surgery, and the treatment is generally considered to be difficult and the outcome unpredictable.
There is little evidence to support choice of different methods of treatment, and current treatment is largely experience-based, or based on level 4 evidence of reported case series. This chapter presents methods of clinical evaluation and treatment and the lead author’s approach to treating this problem, supplemented by the coauthor’s experience.
Clinical assessment
Clinical description
Interpreting the complaints of patients with severe pain and assessing pain severity is difficult for various reasons. Pain has many facets, and the dominant facet varies between patients. Patients may describe the same problem in different ways, and the sheer immensity of the pain may lead a patient to have difficulty rationalizing in a way sensible to the medical practitioner.
We also lack a good language for description of pain. Simply bundling everything together and scoring the total package on a pain scale chart from 0 to 10 may be convenient, but it is not useful in determining how to treat the various categories of pain. Nevertheless, this scale remains a common tool used for clinical documentation.
In discussion with patients and colleagues, it is convenient to consider four common types of pain: “spontaneous pain,” “pressure pain,” “movement pain,” and “hypersensitivity of the skin overlying the involved part of the nerve.” The term hypersensitivity is used to encompass all of the subdivisions of this abnormal and unpleasant skin response to touch described by neurologists, including dysesthesia, hyperalgesia, and allodynia. While not all encompassing, most patients will easily understand these differences and can compartmentalize their pain in this way to our benefit. This will be further explained throughout this chapter.
Pain resulting from pressure on the overlying skin and pain resulting from movement of associated joints and tendons are obvious, as is hypersensitivity of the skin overlying an injured nerve. Although poorly understood, most patients have pain at rest. This spontaneous pain usually has two components: (1) a continuous aching (basal spontaneous pain) punctuated by (2) brief episodes, or spikes, of more intense pain (spiking spontaneous pain) that occur with varying frequency and severity. At worst, these are associated with reflex motor activity, causing the whole limb to jerk. While the patient may be able to relieve the other three modalities of pain by avoiding use of the limb, or part of it, the spontaneous pain can only be relieved with medical help. It is the most wearying feature of the condition for the patient, particularly if it persists through the night and prevents sleep. It may lead to character changes, family disruption, and, even, suicide. In some, the character changes are such that we speculate that there may be a mental predisposition in those presenting with this problem.
Any assessment of pain is inevitably subjective, making the process open to fraudulent claims. However, given the tedious nature of medical processes and treatments for the patient, we advise that most patients be believed in the first instance; automatic assumption that the patient’s claim is false is an unhelpful starting point.
We commonly use pain scoring charts, scoring either from 0 to 10 or 0 to 5, where the lower figure indicates no pain and the upper figure the worst pain the patient can imagine. Some patients find it difficult to understand pain scoring charts, and we have found it quicker in busy clinics to score each pain as “ severe,” “moderate,” “mild,” or “none,” with each of the four modalities of pain described above scored in this way. For comparison among research studies in which pain has been scored using conventional pain charts with five or ten degrees, it may be helpful to include an additional category of “ worst imaginable” so that this verbal scoring also has five components. This would make the two methods easily interchangeable.
Clinical examination and imaging tools
The historical causes of the pain should be explored thoroughly and the site of pain examined carefully. In patients with a surgical history, the region and type of surgery should be included in the history-taking and the previous surgical site evaluated carefully. A positive Tinel sign with significant pain will usually indicate a neuroma or scar tethered nerve. Hypersensitivity overlying a site of nerve transection also suggests neuroma formation or scar tethering of a nerve. Postsurgical scars may be a cause of persistent pain from small nerveends trapped in the scar. However, extensive scarring in the hand or forearm may affect the deeper nerves and cause more severe nerve pain. In these patients, passive and active motion of distal joints should be examined for diagnosis of any other pathologies in the painful area. Generally, movement of tethered tendons and contracted muscles is less painful than the pain of neuromas or scar-tethered nerves. Clinically, it is usually possible to identify the nerve(s) responsible for the pain by local anesthetic injections proximal to the site of pain ( Box 35.1 ).
- 1.
Local causes: end neuromas, neuromas in continuity, and scar-tethered nerves.
- 2.
Consider four clinical aspects: spontaneous pain, pressure pain, movement pain, and hypersensitivity of the skin overlying the involved part of the nerve.
- 3.
Record the pain using a scale of 1–10 or as severe, moderate, mild, or none.
- 4.
Thorough history-taking and clinical examination are necessary, including Tinel’s sign, ultrasound imaging, and, if necessary, magnetic resonance imaging (MRI).
- 5.
Local anesthetic injections proximal to the site of pain can be used to identify the nerve(s) responsible for the pain.
- 6.
Conservative treatments may be helpful (1) for patients awaiting surgery, (2) when local surgery has only been partially successful, and (3) for patients reluctant to accept any surgery.
- 7.
Conservative treatments include neuromodulation (locally* and spinal root stimulation), splinting therapy measures, and medication (such as painkillers).
*Percutaneous needle electrolysis (PNE) is a more recent method.
- 8.
Surgery is indicated in patients who have an identifiable causes of the neurological pain, such as neuromas, neuroma in continuity, or extensive scarring compressing nerve trunks. In many cases, pain relief is at the expense of distal sensory function.
- 9.
The local surgery failure rate is estimated to be around 10–20%.
Ultrasound is particularly useful in patients with scar tethering, as it demonstrates nerve integrity, often edematous, and any immobility of the nerve during active and passive mobilization of the segment. Magnetic resonance imaging (MRI) of the area affected by pain may also identify possible causes, such as extensive scarring, compression of a nerve, and neuroma formation. With these imaging tools, the major nerves are relatively easy to visualize; unfortunately, the terminal branches of cutaneous nerves are not.
Treatment options
Nonsurgical treatment
Current conservative treatments for neurogenic pain are limited, and often, the patient remains tied to a pain management team for life, which is a significant consideration. Painkillers, muscle relaxants, and physical therapy remain common nonsurgical methods of treatment, but their effectiveness is often limited. Prior to surgical referral, most patients will have been treated with drugs without success, or with marginal results, often marred by such unpleasant side effects that the patient stops the drugs.
Neuromodulation, which modulates the transmission of pain by electrical stimulation of the nervous system ( Box 35.1 ) locally, may be trialed before surgery. This modality, at a spinal root level, is also used for cases in which surgery is not indicated or has failed to relieve pain.
The lead author’s unit only has favorable experience of transcutaneous peripheral nerve stimulation (TPNS), a noninvasive neuromodulation that can be used indefinitely. In TPNS, a handheld probe is placed on the skin overlying the nerve(s) proximal to the site that is causing the pain for 10 to 15 minutes. TPNS works at a much lower frequency and higher intensity than transcutaneous electrical nerve stimulation (TENS) and, in the lead author’s experience, is considerably more effective in relieving this problem. Like TENS, it can be easily and safely self-administered by the patient. If drug treatment has failed, TPNS is routinely offered in some units, including the senior author’s unit, before local surgery as surgery is painful, expensive, and not always acceptable to the patient. Patients receive five trials of TPNS. If it works, they may choose to continue coming to the hospital every few weeks or buy their own machine for self-administration. Some patients do purchase this expensive equipment, which allows them to use the device more frequently. In a retrospective study of 72 patients, the lead author’s unit achieved complete cure of the pain in 6 of 72 patients (8%), achieved a useful therapeutic outcome (pain relief ≥1 day) in 29 of 72 (40%), and failed to relieve pain in 37 of 72 (51%). If TPNS does not work, or if a patient tires of coming to the hospital regularly because of the expense or travel time (and does not want to buy a machine), alternative treatments, including local surgery, are discussed further.
Surgical treatments
Surgery is indicated for patients who have an identifiable cause of the neurological pain, such as an end neuroma(s), neuroma in continuity, or extensive scarring around nerve trunks ( Box 35.1 ). Many local surgical methods have been described for the relief of end-neuroma pain. While the ideal goal is to restore distal function and relieve the nerve pain, when pain supervenes in a limb, it limits function so greatly that pain relief becomes the primary goal of treatment. In many cases, pain relief is at the expense of distal sensory function.
Personal experience with more than a few of these many procedures by any one surgeon is unlikely. The learning curve is long and one of trial and rejection until a few personal techniques evolve that achieve an acceptable success rate. Clinically, it is important to explain to the patient the cause of pain, the concept of any treatment, and the reasoning behind the particular choice. Patients should also be warned that more than one operation may be required to achieve maximum benefit from local surgery. An important consideration in management is that these patients are often at the end of their tether; they have often experienced several failures of treatment, sometimes with worsening of their pain, and the option of “trying” an unproven technique, or a plan that could include several alternatives in sequence, is very far from ideal. The ideal for the patient is a single operation that the surgeon knows will “usually” work.
The following methods are often described and used: (1) dividing the nerve just proximal to the painful part, with or without diathermy of the proximal nerve end, (2) wrapping nerve ends in various foreign materials or vascularized or unvascularized fat flaps, (3) splitting the nerve end to allow suture of the two parts as a loop, (4) the “wandering” nerve graft, which hopes that nerve growth along the graft will fall off sufficiently that no end neuroma occurs at the distal end of the graft, (5) wrapping in continuity of painful nerves in continuity in a vein, and (6) relocation to certain sites, which will be discussed later in this chapter ( Box 35.2 ). The lead author has found above methods are unsuccessful in his patients. An important fault of any procedure that involves a nerve suture, e.g., methods (3) and (4), is that the site of nerve suture may become a (painful) neuroma in continuity with or without scar tethering. Below we detail surgical goals, methods, and outcomes of common causes of nerve pain.
- 1.
Dividing the nerve just proximal to the painful part, with or without diathermy of the proximal nerve-end * .
- 2.
Wrapping nerve ends in various foreign materials or flaps * .
- 3.
Splitting the nerve end to allow suture of the two parts as a loop * .
- 4.
The “wandering” nerve graft, so nerve growth along the graft may fall off sufficiently and no end neuroma occurs at the distal end of the graft * .
- 5.
Wrapping in veins the painful nerves in continuity * .
- 6.
Relocating the nerve to certain sites * .
- 7.
The authors’ preferred methods (1) for all end neuromas is relocation of the proximal nerve end to specific proximal and deeper sites; (2) division and relocation of smaller painful nerves in continuity; and (3) tenoneurolysis and vascularized fascial flap wrapping of painful major nerves.
- 8.
Targeted muscle reinnervation and release of potential nerve entrapment sites proximal to the pain area are two recent methods that need further experience.
* all of these methods have found unsatisfactory in the lead author’s experience of earlier use of these methods.
Surgical methods for divided nerves and end neuromas
Treatment goals
The ideal treatment of a recently cut nerve is to reconnect the nerve ends quickly, restoring distal function and containing axonal sprouting as prophylaxis against painful neuroma formation. Various factors, such as the patient’s wishes, age, and delay to presentation, can make it impossible to achieve this goal. Coaptation of divided nerves frequently does not restore distal sensory normality. Most often, distal sensation is reduced, sometimes to nil. Occasionally, the recovering sensation can be painfully hypersensitive without relief with the passage of time.
Some patients will develop a painful end neuroma of the proximal end of a cut nerve that is not repaired. The lead author’s current treatment of all established end neuromas is relocation of the proximal nerve end to very specific proximal and deeper sites ( Box 35.2 ). This usually means proximal relocation to bone or muscle, with only certain muscles, namely the pronator quadratus (PQ) , and brachioradialis (BR), being effective, depending on which nerves are involved. The thenar and hypothenar muscles , and in, or under, the long flexor muscles in the forearm have all been reported as unsatisfactory muscle relocation sites. This treatment was initiated by the senior author in his unit on the premis that an end neuroma placed proximally and deeper than its current anatomical site will be traumatized less by daily use. This has proven true for the lead author in several hundred cases. Fortunately, these relocations, almost invariably, also eliminate, or substantially reduce, spontaneous pain and hypersensitivity.
In the lead author’s experience, reconnection of a proximal nerve end, once painful, usually as a secondary procedure and, sometimes, with graft interposition, often progresses to a painful nerve in continuity and/or advancing sensation that is accompanied by advancing pain. Currently, the lead author advises against reconnection if the proximal nerve end is already painful. This complication of local or advancing pain after nerve suture, arising in the larger median and ulnar nerves, has no local surgical solution. Although distal sensation is generally poor after median or ulnar nerve suture at the wrist when the suture site becomes painful, there are few alternatives to retaining the continuity of these nerves and what distal sensation there is. Concern about continued pain should the repair be divided and the nerve relocated to the forearm is realistic, although forearm amputation stumps only rarely develop such a problem in any of the three major nerves buried therein. If reconnection of a smaller nerve remains painful, the nerve can be divided again and the proximal end relocated, accepting loss of distal sensation in exchange for pain relief. In reality, these nerves have almost always regenerated with poor distal sensation, so this loss is less problematic to the patient.
Where a distal nerve is not available for coaptation, some local flaps and free tissue transfers, particularly of toes, can provide a cut nerve with distal nerve-to-skin connection. However, these procedures risk further nerve pain at the donor site and, done as they are when the proximal nerve end is already painful, are not entirely immune to the problems of reconnection mentioned above. The coauthor uses local flaps to cover involved nerves after excision of extensive scarring in the forearm.
Different sites (zones) of nerve relocation
The distal upper limb can be split into three zones according to the primary site(s) commonly used for relocation ( Fig. 35.1 ). This classification was introduced by the lead author to make discussion of this subject easier among clinicians.
Zone I includes all finger digital nerve injuries beyond the distal palmar crease and the nerves innervating the dorsum of the fingers beyond the metacarpophalangeal (MCP) joints, with the first choice of relocation being a proximal phalanx or metacarpal bone.
Zone II includes the digital nerves of the thumb, the finger digital nerves in the palm, nerves on the flexor aspect of the wrist, and those on the dorsoulnar aspect of the hand, with the first choice of relocation being the pronator quadratus muscle.
Zone III includes the dorsoradial aspect of the hand and wrist, the dorsal aspect of the thumb and the forearm more proximally, with the first choice of relocation being the muscles of the forearm and arm, especially the BR and brachialis.
Preoperative assessment
It is usually possible to identify the nerve(s) responsible for pain by local anesthetic injections proximal to the site of pain. This requires knowledge of the conventional sensory neuroanatomy of the limbs and awareness of anatomical sites (1) where several nerves may be involved and (2) where anatomical variation can occur. Lignocaine blocks with 2% solution act more quickly than weaker solutions and require smaller doses, which can be important to independent blockage of nerves lying close together.
The practice of local anesthetic blocking, which can be done in clinic, is recommended as a routine; operating without this knowledge is more likely to result in missing the involvement of several nerves and failing to relieve the pain. This will be discussed further, particularly in regard to nerve pain in the digits and on the radial side of the wrist, where multiple innervation is most likely to occur. While nerve blocking is difficult in very fat limbs and impossible in patients with needle phobia, it usually provides the information required to identify the nerves involved in the pain. Failure to identify precise feeding nerves preoperatively in long-standing cases and in patients who have already undergone neuroma operations for pain, often elsewhere, should make the surgeon wary of abnormal innervation. In these situations, surgery based on undergraduate knowledge of sensory nerve anatomy of the limbs is unlikely to succeed. Experience and reading beyond the literature on hand surgery would suggest that conventional teaching of peripheral nerve anatomy is simplistic.
Zone I (digital nerves)
The fingers are innervated by two (palmar) digital nerves, their dorsal branches, and the nerves innervating the dorsum of the hand (the superficial radial nerve and the dorsal branch of the ulnar nerve). Contrary to routine teaching, innervation from the dorsum of the hand may variably extend beyond the proximal interphalangeal (PIP) joint to the nail base, particularly to the nail base of the thumb, index, and little finger. It is also recognized that small nerve branches link the palmar and dorsal finger innervations. For these reasons alone, even when it seems obvious that the pain lies within the territory of a single digital nerve, local anesthetic injections are advised in small volumes at the base of the digit on both surfaces. Additionally, the bone of a distal amputation stump is sometimes covered by turnover of a dorsal skin flap, and dorsal innervation, whether from the dorsal branches of the digital nerves or from the nerves innervating the dorsum of the hand, may be the source of pain. In finger amputations at and proximal to the PIP joint, dorsal skin innervation requires particular consideration.
Burying digital nerve ends in the lateral aspect of the phalanges of the involved finger is effective. However, relocating a painful nerve end into the immediately proximal phalanx, often done with the intention of minimizing the numb area distally, is likely to leave the buried nerve too close to the digital tip and still vulnerable to frequent episodes of trauma. The branches of the digital nerves innervating the palmar surface of each phalangeal segment leave the main digital nerve proximal to that segment, usually one phalangeal segment proximal to the segment innervated by that branch. Consequently, the end of the digit may remain innervated by these branches when the main digital nerve has only been relocated proximally by one segment.
Relocation of digital nerve ends injured distal to and in the vicinity of the distal interphalangeal (DIP) joint to the lateral surface of the proximal part of the proximal phalanx, close to the web, obviates these problems ( Fig. 35.2 ). A substantial dorsal branch of each digital nerve is commonly given off in the distal palm; it is important to always relocate this branch as well. In the lead author’s experience, relocating digital nerves to the dorsal surface of the digit, usually over the middle phalanx, simply transfers the painful neuroma to another site frequently bumped in routine use of the hand.
It is advised to drill the bone hole before moving the nerve(s) for relocation, as the spinning drill may catch a free nerve in its vicinity and avulse it proximally. All bone holes are beveled proximally, where the nerve crosses the edge, as a sharp bone edge at the relocation site may be a source of ongoing pain when closing the fingers together. Neuroma bulbs are excised, as the relocated nerve is generally too long, and a smaller bone hole is needed to accommodate a freshly cut nerve. Moreover, pain levels have never been shown to relate to the size of the bulb. The nerve is then cut to an appropriate length to allow the end to sit 2 to 3 mm inside the phalanx while leaving the proximal nerve slightly loose. The nerve is then sutured where it enters the bone hole to the adjacent periosteum with 6-0 nylon sutures. Despite this, a few remain irritated by full extension of the MCP joints ( Fig. 35.3 ). Generally, the neuroma pain settles using this relocation site. However, when there is ongoing pain at the site for one of the two reasons mentioned above, the nerve end is moved to the metacarpal site at a second operation.
Digital nerve injuries giving rise to end neuromas more proximal in the finger than the DIP joint and the distal part of the middle phalanx are taken back into the palm, through the interosseous muscles, and buried in a bone hole in the lateral surface of the metacarpal of the involved finger ( Fig. 35.4 ). This generally requires that the common digital nerve be split to take the involved digital nerve and its dorsal branch back to approximately 1 cm distal to the level of the superficial palmar arch. This is easily and quickly done under loupe magnification. An artery clip is then passed along the side of the metacarpal of the involved finger in a palmar-to-dorsal direction. The dorsal skin is incised onto the point of the clip. This incision is deepened to bone, avoiding any dorsal hand nerve branches. The periosteum is cut longitudinally 2 cm along the edge of the dorsal interosseous muscle. This muscle is retracted to allow a drill-hole of slightly greater diameter than the digital nerve and its dorsal branch to be made as far down the lateral surface of the metacarpal from the dorsum as possible, with the palmar edge beveled. A second artery clip is then passed in the opposite direction, and the nerves are drawn dorsally. There is considerable risk of catching the nerve in the drill and avulsing it if this order of events is reversed.
The nerve is then cut to an appropriate length to allow the end to sit 2 to 3 mm inside the metacarpal, ensuring the nerve is loose at its turning point in the palm. After nerve suture to the adjacent periosteum, the interosseous muscle is lifted over the nerves and sutured to the dorsal periosteum as added protection. In the senior author’s experience, burying these neuromas in any of the small muscles on the palmar side of the hand fails because of repeated pressure on these muscles when the patient returns to power gripping. When there is involvement of the digital branches of the nerves innervating the dorsum of the hand, these also require relocation into a metacarpal ( Fig. 35.5 ). Generally, these nerves are relocated into the same bone hole or one immediately adjacent.
Because there is no fat padding on the dorsum of the hand, the buried nerve ends are never far enough from the dorsal skin surface, and some of these relocations remain tender to direct pressure, sometimes indefinitely. The daily frequency with which the nerve end is traumatized is usually much reduced, except in patients whose work involves passing the hand into narrow spaces and in some who are heavy manual workers. Occasionally, the movements of the extensor tendons stimulate the nerve too much. Rarely, the nerve tethers in scar tissue at the turning point in the palm, preventing tight gripping. Should one of these problems persist, the nerve ends are relocated to the pronator quadratus muscle at a second operation. An occasional complication is scar tethering of the dorsal nerves of the hand when the dorsal dissection down to the metacarpal passes these nerves. The senior author has tried making the bone hole in the lateral aspect of the metacarpal from the palmar side of the hand to avoid the dorsal problems described above ( Fig. 35.6 ); to date, results have been mixed, and there have been too few of these cases to recommend this approach. However, as mentioned, the small muscles on the palmar surface of the hand are not a good alternative relocation site.
The lead author is reluctant to use the pronator quadratus site as the routine site for relocation of all Zone I cases, as the two sites described above usually work well. Dissection to the pronator site takes longer and is more complicated. It involves an intrafascicular dissection from the main trunk of the median or ulnar nerve through the carpal tunnel or Guyon’s canal under loupe magnification, a procedure with a definite learning curve before it becomes safe and quick. It is recommended that this procedure is learned using loupes, not a microscope, as the latter lengthens the task unnecessarily. There is the theoretical possibility of this dissection scarring the main nerve trunk and creating a further cause for pain. To date, this has not occurred with many such dissections of the median nerve through the carpal tunnel. However, this dissection of the ulnar nerve through Guyon’s canal can leave troublesome hypersensitivity of the small nerve branches to the hypothenar eminence that only settles after months ( Fig. 35.7 ) unless the whole of the palmar sensory part of the ulnar nerve is relocated to the pronator quadratus, which is not often performed ( Fig. 35.8 ).
Amputation of digits, for whatever reason, risks neuroma formation, and it is sensible practice to anticipate this possibility. When performing proximal finger and ray amputations, dissecting the digital nerves from as far distally as possible before removing the distal part of the digit provides maximum nerve length for relocation. The nerve ends can be buried in the adjacent metacarpals before closing the gap in the body of the hand in ray amputations of central fingers. While it may be convenient to pass the nerve ends into the end of the metacarpal stump following index and little-finger amputations, the nerves may be pinched against the bone edge when gripping. Relocation into a proximal hole on the blind side of the metacarpal base avoids this. When end neuroma pain presents following previous proximal finger and ray amputations, the nerves may have been cut too short to do the above, and relocation to the pronator quadratus may be necessary.
The thumb is innervated by five nerves, including two digital nerves, two branches of the superficial radial nerve (of approximately the same size as the digital nerves), and the palmar cutaneous branch of the median nerve, with some variation in the territories and overlap of these nerves. Of course, the thumb is shorter than the fingers, so the first relocation described above cannot be used. The digital nerves of the thumb do not settle if buried in the thenar muscles or the thumb metacarpal. For these reasons, these digital nerves are routinely relocated to the pronator quadratus ( Fig. 35.9 ). The other nerves innervating the thumb and thenar eminence are discussed later. In proximal thumb amputations, all five nerves may be sites of end neuroma pain and all five may require relocation to ensure pain relief ( Fig. 35.10 ).
The lead author reported relocation of 104 painful digital nerves in Zone I prior to 2004. Among these were end neuromas and painful nerves in continuity. The latter were divided then the proximal cut ends relocated. Seventy nerves settled after a single relocation, and 34 required a second procedure. As can be seen, it was possible to cure the pain entirely or reduce it to tolerable levels at both the primary and eventual sites of relocation in 80% to 90% of nerves. Ongoing pain when pressure was placed on the relocation site was the commonest ongoing problem. However, the effect of the examiner applying digital pressure directly over the relocation site does not recognize the decrease in frequency of mechanical stimulation at the more proximal relocation sites during normal hand use. We have continued to use these relocation sites routinely since 2004.
With regard to overall hand function, even the handicap of a completely denervated digit has proven to be minimal compared to the enormous benefit of pain relief, and this has been shown to be true for all five digits. Sensation in the other and adjacent fingers protects a numb finger, and patients adapt their pinch and span grip activities to the sensate digits. This is in keeping with the common observation that many digital nerve repairs do not provide useful tip sensation, and some fingertips remain entirely numb after these repairs without major disability. Even a numb thumb will be used as a post against which innervated fingers can pinch, as is recognized in toe-to-hand transfer surgery.
Failure of a first relocation can occur in Zone I when one digital nerve is thought to be the sole cause of pain and only that nerve is relocated, then the other digital nerve or the dorsal innervation proves to also be involved. This can largely be avoided by performing local anesthetic studies in all cases. Occasionally, local anesthetic studies identify involvement of only one digital nerve; this nerve is relocated with pain relief, and the patient returns 6 to 12 months later when the pain returns. Local anesthetic repeat indicates that the second digital nerve is now “involved.” This is quite possible, as interconnections between the digital nerves and those coming from the dorsum of the hand have been described and seen by the senior author on several occasions. The digital nerves may interconnect in a similar fashion. Alternative explanations are that (1) the remaining nerves sprout and extend into the “vacant” territory and (2) chemicals induced by the inflammatory response to tissue damage in an area of trauma are now stimulating the next adjacent nerve. , , This problem is discussed again later. Relocation of the remaining nerve(s) of the digit will relieve this return of pain in most instances.
Zone II
In 1994, Evans and Dellon described relocation of the palmar cutaneous branch of the median nerve to the pronator quadratus muscle to treat end neuromas in this nerve ( Fig. 35.11 ). The senior author adopted this technique for relocation of end neuromas and scar tethering of this nerve, short true and common digital nerves, the digital nerves of the thumb, and the dorsal branch of the ulnar nerve. ,
