- Email: [email protected]
Transverse Deficiency
5.4 Transverse Deficiency Angelo B. Lipira, Jeffrey B. Friedrich
SYNOPSIS Congenital transverse deficiency of the upper extremity is a rare but disabling condition in which all elements beyond a given level in the extremity are absent. The most common level is the proximal forearm, but it can occur at any level from the humerus to the metacarpals. This chapter describes the disorder, presentation, and an approach to management of patients with this condition. Surgery is not indicated in most transverse deficiencies at the forearm level or more proximal, but there are several surgical techniques that can improve function in patients with hand-level transverse deficiencies including symbrachydactyly. Described in detail is the technique of four-flap Z-plasty for first web space deepening, along with the postoperative care, common complications, and their management.
CLINICAL PROBLEM Congenital transverse deficiency is a rare but severe condition in which the upper extremity is truncated at a given level and all normal elements beyond this are absent. The estimated incidence is between 15 and 60 per 100,000 live births.1 In transverse deficiencies, a portion of the limb is missing, but the proximal supporting structures are intact, although typically hypoplastic. This is in contrast to longitudinal deficiency, wherein the proximal supporting structures are absent or severely deficient.2 Historically, transverse deficiencies were often referred to as “congenital amputations,” but this is etiologically incorrect. As opposed to amniotic bands causing prenatal amputation of a limb that has already formed, transverse deficiency is considered a failure of formation of parts, type IA in the International Federation of Societies for Surgery of the Hand (IFSSH) system for congenital hand differences.3 The disorder is sporadic and is thought to be caused by disruption to the normal proximal-to-distal development of the extremity during embryological development of the upper limb.3 The management of transverse deficiencies requires an individualized approach, taking into account the level of the deficiency, current functional status, and the goals and desires of the child and family. In many cases throughout the world, surgical treatment is not indicated and children can adapt incredibly well to their differences with or without custom prosthetic devices. In particular, when the contralateral hand is unaffected, extensive reconstructive efforts are not usually indicated. In specific clinical situations, surgical interventions may be indicated to improve limb function. Examples include excision of nubbins or skin invaginations if causing secondary problems or interfering with
334
prosthesis fit. In hand-level deficiencies, procedures that increase effective digital length may allow or improve prehensile function. Most commonly, this entails web space deepening with local flaps and tissue rearrangement techniques. Other procedures include skeletal lengthening using distraction osteogenesis, and vascularized or non-vascularized toe transfers. This chapter will provide an overview of transverse deficiency and surgical procedures to improve hand function, with a more in-depth look at web space deepening techniques.
Presentation Patients with transverse deficiency present with congenital truncation of the upper limb, which may occur at any level from the humerus to the metacarpal. This may be detected on prenatal ultrasound examinations, or it may not be discovered until birth. Transverse deficiency can be differentiated from amniotic band syndrome (prenatal amputation), because osseous hypoplasia is a cardinal feature of the former but not the latter.3 The left upper extremity is affected twice as often as the right, and males are affected more commonly than females.4 The most common level of truncation is at the proximal forearm, followed by the transcarpal, distal forearm, and distal humerus levels.2 Rudimentary finger “nubbins” are often present at the distal end of the truncated extremity, regardless of the level of deficiency. These often have nail plates and variably present extrinsic tendinous structures. Skin invaginations may also be present at the terminal end of the limb, which can cause issues with hygiene or infections. Symbrachydactyly, a condition characterized by shortened or absent fingers with various degrees of fusion, is now considered to be a type of transverse deficiency occurring at the level of the hand, although it is still classified as an “undergrowth” abnormality by IFSSH.5 Symbrachydactyly was classified into four types by Blauth and Gekeler.6 Type 1, short finger type, is characterized by four shortened, syndactylized fingers with an essentially normal thumb. Type 2, oligodactylic type, is characterized by central clefting or aplasia. Type 3, monodactylic type, demonstrates absence of all fingers with a normal thumb. Type 4, peromelic type, presents with an absence of all digits at the metacarpal level (Fig. 5.4.1).
Etiology One of the most important roles of the hand surgeon is to convey accurate information to the parents of a child born with congenital limb differences regarding the etiology of a condition, and to help to dispel feelings of guilt or parental responsibility that are commonly present. Culturally appropriate education is critical, especially when working in another country. Transverse deficiency is usually sporadic,
CHAPTER 5.4 Transverse Deficiency
335
5 to 7 of gestation may lead to transverse deficiency. AER disruption is thought to be due to a vascular problem, either ischemia or bleeding, in most cases.2 It is theorized that rudimentary digits, or nubbins, may be a result of a prenatal regenerative response to intrauterine trauma.8 Morphologically, these nubbins are similar to the distal portions of fingers, and can form on the end of limbs that are missing all other terminal structures. They can be found on the distal end of the limb, regardless of the level of truncation. It is theorized that either portions of the AER survive the insult and lead to the generation of the nubbins, or that the AER itself partially regenerates and induces the formation of nubbins.8
Associated Conditions Transverse deficiency usually presents unilaterally in otherwise healthy children without other congenital differences. Symbrachydactyly, however, may be associated with Poland syndrome, in which absence of the sternal head of pectoralis major and other muscles of the shoulder girdle may be absent or deficient.5
PRE-OPERATIVE MANAGEMENT Physical Examination and Key Anatomy FIG. 5.4.1 Transverse deficiency at the level of the metacarpals, with a relatively preserved thumb. Rudimentary digital structures, or “nubbins,” are located at the terminal aspect of the limb and can be found in more proximal transverse deficiencies as well. (Reproduced from Tonkin M, Oberg K. Congenital hand I: Embryology, classification, and principles. In: Neligan P, Chang J, eds. Plastic Surgery, 3rd ed, vol 6. London: Elsevier Saunders; 2013.)
Fgfs (AER)
Stage 13
Stage 15
Stage 17
FIG. 5.4.2 The apical epidermal ridge (AER) is a signaling center covering the distal aspect of the developing limb. Through fibroblast growth factors, the AER orchestrates differentiation of the underlying mesenchymal development along the proximal-to-distal axis. (Reproduced from Tonkin M, Oberg K. Congenital hand I: Embryology, classification, and principles. In: Neligan P, Chang J, eds. Plastic Surgery, 3rd ed, vol 6. London: Elsevier Saunders; 2013.)
and subsequent children are not thought to be at increased risk of limb differences. There is an association with maternal intake of alcohol, tobacco, cocaine, or misoprostol, as well as riboflavin deficiency.2 There is also some evidence for an increased risk associated with chorionic villus sampling if the procedure occurs during the period of limb morphogenesis.7 Nearly all congenital upper limb differences arise between gestational day 26, when the limb bud appears, and day 53, when the fingers are fully separated.2 The longitudinal development of the upper limb is driven by the apical ectodermal ridge (AER), a signaling center on the distal aspect of the limb bud that acts through fibroblast growth factors (FGFs) to render proximal to distal limb development and finally interdigital necrosis (Fig. 5.4.2). The AER signals the differentiation of the underlying mesenchymal components of the limb bud, and is genetically programmed to induce appropriate differentiation through the time course of limb formation.8 A disruption of AER signaling during weeks
Transverse deficiencies should be characterized in terms of the level of truncation, and any associated distal rudimentary structures such as nubbins or invaginations. Furthermore, the function of adjacent joints such as the elbow and shoulder should be assessed and documented. In forearm-level transverse deficiencies, elbow flexion and extension are usually intact, but forearm rotation is commonly impaired by proximal radioulnar abnormalities. In patients with more distal transverse deficiencies at the hand or digit level, including those with symbrachydactyly, the functional usage of the hand should be determined. In particular, pinch and prehensile function should be assessed, because these functions may be restored or improved with surgical interventions. The best way to assess this in young children is to observe them playing with simple toys. The fundamental function of the hand, prehensile function, can be achieved with a mobile thumb able to oppose other parts of the hand. In symbrachydactyly, the central rays are always affected, with variable involvement of the thumb and small finger. Depending on the specific morphology of the patient, web space deepening procedures can significantly improve prehensile function, particularly deepening of the first web space. Procedures requiring highly specialized equipment such as microsurgical instruments or distraction devices may not be possible or advisable in some facilities.
Pre-Operative Testing Needed In forearm-level transverse deficiencies, standard x-rays of the elbow and forearm are generally the only diagnostic investigations required (Fig. 5.4.3). Proximal radioulnar abnormalities are commonly present in forearm-level deficiencies. In patients with hand-level truncation, including symbrachydactyly, x-rays are useful to understand the underlying skeletal abnormalities and to assess whether certain interventions such as distraction osteogenesis may be possible for the patient. No specific pre-operative investigations are needed before web space deepening procedures, but close observation of the patient using the hand to play or manipulate objects will guide the surgeon in choosing the appropriate intervention, if any.
Surgical Indications and Decision-Making Surgery is usually not indicated for transverse deficiencies at the wrist or proximal levels, except in specific cases described below. Often, the most helpful intervention of the hand surgeon is facilitating the
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opportunity to work with other providers including physical and occupational therapists, psychologists, rehabilitation specialists, and a prosthetist, who can equip the patient with a variety of different prostheses over time as the child grows and engages in various specific activities (e.g., swimming or racquet sports). Although some surgeons have offered early excision of rudimentary structures (nubbins or invaginations) from the terminal limb, most now recommend reserving excision for situations in which these cause secondary problems such as infections, nail issues, or interference with prosthetic fit. These structures may be useful for manipulating objects and for sensory feedback. Although parents may request excision of these structures, we recommend waiting until the child is older and has been evaluated by a rehabilitation team and prosthetists so that their input may be considered in the planning of any stump adjustments. Other procedures for forearm-level deficiencies have been described but are very uncommon. Forearm lengthening is associated with a high complication rate, and has not been shown to improve function. The Krukenberg procedure, where the forearm bones are separated to convert
FIG. 5.4.3 Standard x-rays of the elbow in a patient with a very proximal forearm-level transverse deficiency. (Reproduced from Smith G, Smith P. Congenital hand II: Disorders of formation (transverse and longitudinal arrest). In: Neligan P, Chang J, eds. Plastic Surgery, 3rd ed, vol 6. London: Elsevier Saunders; 2013.)
A
the forearm stump to a pincer, is indicated in only very rare circumstances due to the highly unfavorable cosmetic appearance. It is traditionally indicated for bilateral amputees with blindness, because these patients cannot use traditional prostheses due to the lack of visual or tactile feedback.2 In hand-level transverse deficiencies, including symbrachydactyly, surgery is more frequently indicated because deepening web spaces or lengthening digits may improve prehensile function. When the contralateral hand is unaffected, surgery should generally be limited to less complex procedures such as web-deepening procedures and soft tissue release. More complex techniques include free vascularized toe-to-hand transfers, non-vascularized toe phalangeal bone grafts, and distraction osteogenesis for skeletal lengthening. Determining which lengthening procedure is most appropriate depends on what structures are absent and present, available resources, surgeon experience and ability, and the ability of the patient and family to comply with the post-operative course. Free vascularized toe-to-hand transfer may be an option for certain patients with necessary proximal skeletal support and extrinsic tendons, which are variably present in transverse deficiencies.9 Example indications would be an absent thumb or a preserved thumb with an absence of other digits to oppose to (Fig. 5.4.4). Disadvantages of this technique include technical difficulty, lengthy surgery and recovery, donor site morbidity, and the need for microsurgical skills and equipment. Multiple simultaneous toe transfers can be performed to a single hand. In children 15 months or younger, non-vascularized toe phalangeal bone transfers to digits of the hand may be useful to augment length and skeletal support.10 This technique is not advised in older patients, because the grafts typically resorb. Non-vascularized toe phalanx transfers are most useful in patients in whom digital skeletal elements are hypoplastic but the soft tissue envelope is relatively preserved. Reports of growth of the grafts over time have been highly variable, and some authors have even performed later distraction osteogenesis on the grafted bone.11,12 Distraction osteogenesis (also known as callus lengthening or callotasis) for lengthening of hand bones is a technique where a specialized external fixation device is applied to the bone, an osteotomy is made, and the bone and soft tissues are gradually lengthened over time through callus formation and soft tissue creep (Fig. 5.4.5). In symbrachydactyly, modest
B
FIG. 5.4.4 (A) Free vascularized toe-to-hand transfer for reconstruction of index finger in a patient with a relatively preserved thumb. (B) Prehensile function is achieved. (Reproduced from Smith G, Smith P. Congenital hand II: Disorders of formation (transverse and longitudinal arrest). In: Neligan P, Chang J, eds. Plastic Surgery, 3rd ed, vol 6. London: Elsevier Saunders; 2013.)
CHAPTER 5.4 Transverse Deficiency
A
337
D
B
E
FIG. 5.4.5 (A) A 4-year-old male with transverse deficiency at the
C
metacarpal level of the right upper extremity. Note the relatively unaffected thumb. The remaining four fingers are rudimentary, with some development of the index and middle proximal phalanges, and only nubbins for the ring and small digits. (B) Photograph and (C) x-ray after osteotomy of second metacarpal and application of distractor device. (D) Photograph and (E) x-ray after distraction of 25 mm and 7 weeks of consolidation.
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F
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D
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FIG. 5.4.6 Illustration of a four-flap Z-plasty designed to deepen the first web space. (Reproduced from Vedder NB, Friedrich JB. Thumb reconstruction: Nonmicrosurgical techniques. In: Neligan P, Chang J, eds. Plastic Surgery, 3rd ed, vol 6. London: Elsevier Saunders; 2013.)
gains in metacarpal or phalanx length may allow or improve prehension. Examples include lengthening a thumb so that it can reach the other digits, or lengthening a second or third ray so that the digit may reach the thumb. Distraction lengthening is a difficult and time-consuming process for young children and their families to undergo, and it may not be a good option for many, particularly in the developing world. The remainder of this chapter will focus on the technique of web space deepening using local flap techniques. Widening and deepening of the first web space in particular can allow for increased thumb mobility and opposition to other digits. These procedures attempt to create a scar-free web line, and thus place incisions crossing the web space obliquely. Simple Z-plasty may occasionally be adequate, but in most cases it does not create an appropriate contour and may leave a depression at the base of the first web space.13 Simple Z-plasty can be useful for web spaces other than the first, however. The four-flap Z-plasty is a reliable technique for first web space deepening that creates a predictable contour and allows sufficient release (Fig. 5.4.6).14 A five-flap Z-plasty (or “jumping man”) can also be effective, but the flaps are narrower and thus the tips more vulnerable to necrosis (Fig. 5.4.7). More severe web space narrowing may require transfer of larger amounts of tissue, such as with flaps from the dorsal hand (e.g., first dorsal metacarpal artery flap) or from the forearm (posterior interosseous artery or reverse radial forearm flap). These procedures are more technically demanding and have more conspicuous donor sites. Fortunately, local flap procedures are usually sufficient. In terms of surgical timing for web space deepening, there are no published guidelines for symbrachydactyly, but the syndactyly literature suggests waiting until the child is 18 months old, unless the growth disturbance or progressive deformity dictates earlier intervention. Anesthesia becomes safer after 1 year of age, and surgery may be less technically demanding due to growth of the hand. A general goal is completion of surgeries before school age.2
SURGERY Procedure—First Web Space Deepening With Four-Flap Z-Plasty The patient is supine with the arm abducted on a hand table. The procedure is performed under general anesthesia with tourniquet control. Regional anesthesia can be considered for older children or adults.
[ E G D
FIG. 5.4.7 Illustration of the double opposing Z-plasty, or “jumping man” flap, an alternative design for first web space deepening or contracture release. (Reproduced from Vedder NB, Friedrich JB. Thumb reconstruction: Nonmicrosurgical techniques. In: Neligan P, Chang J, eds. Plastic Surgery, 3rd ed, vol 6. London: Elsevier Saunders; 2013.)
With the thumb and index finger maximally abducted, the central limb of the Z-plasty is marked along the edge of the web (Fig. 5.4.8A and B). The length of the central limb determines the length of all of the other limbs. Extension of this limb onto either the ulnar thumb or radial index finger surfaces should be avoided. Next, a perpendicular limb of the same length is drawn, arising at the radial-most aspect of the central limb and running proximally on the dorsal hand, parallel to the first metacarpal. A second perpendicular limb is then drawn, arising at 90 degrees from the ulnar-most aspect of the central limb and running volarly near the thenar crease. The two right angles are then bisected with 45-degree limbs, creating four equal triangular flaps. Two of these flaps are on the dorsum, and two are on the volar, glabrous surface of the hand. The volar flaps should be raised first, because it is easier to make small adjustments to the more mobile dorsal skin flaps. The volar flaps are incised and then raised in the suprafascial plane using careful spreading dissection. The radial digital neurovascular bundle of the index finger and ulnar bundle of the thumb must be identified and protected. Next, the dorsal skin incisions are made, and the flaps are raised suprafascially while protecting the small branches of the radial sensory nerve and any longitudinal veins. If the fascia of the first web is constricting, it should be released as well (Fig. 5.4.8C). A small amount of muscle can be resected to further deepen the web space. When well designed and completely dissected, the Z-plasty flaps should easily transpose to their new positions. Minor flap adjustments are typically required before inset (Fig. 5.4.8D). In children, we typically use absorbable monofilament (5-0 fast- absorbing gut) sutures (Fig. 5.4.8E). The four-flap design should create a natural concave contour in the first web space. Incisions are covered with a non-stick gauze, and a well-padded thumb spica splint or cast is applied with the thumb radially and palmarly abducted and the interphalangeal joint free. In children younger than school age, long arm splints are less likely to be removed by the patient.
POST-OPERATIVE CARE The post-operative splint is removed at 2 weeks so that the surgical site can be examined. A custom thermoplastic web spacer splint
CHAPTER 5.4 Transverse Deficiency
339
E
A
B
C
D
FIG. 5.4.8 Technique of four-flap Z-plasty. (A) Dorsal view of first web space showing tight contracted band. (B) Skin markings for a four-flap Z-plasty, with the central limb marked on the tight web and two 90-degree perpendicular incisions at the ends of this limb. These 90-degree angles are then bisected at 45 degrees to form four triangular flaps. (C) Tight fascial bands may be identified dorsally after raising the skin flaps. If constricting, these must be released as well. (D) Inset of flaps after trimming and minor flap adjustments. The volar flaps are thicker and more rigid, and it is often easier to make adjustments to the more mobile dorsal skin flaps. A standing cone deformity has been removed with the extension at the radial side of the index finger. (E) Postoperative appearance showing the contour provided by the four-flap Z-plasty technique. (Reproduced from Upton III, J, Taghinia A. Congenital hand III: Disorders of formation – thumb hypoplasia. In: Neligan P, Chang J, eds. Plastic Surgery, 3rd ed, vol 6. London: Elsevier Saunders; 2013.)
is then fabricated. The patient is gradually weaned from this over 3 to 4 weeks.
MANAGEMENT OF COMPLICATIONS Complications of first web space deepening include infection, wound healing problems, nerve injury, hematoma, and flap necrosis. Necrosis of the tips of Z-plasty flaps can occur if the flaps are narrow or the angles too acute. The flaps should be raised full thickness in the suprafascial plane to preserve their vascularity. When raising the volar flaps, the radial digital neurovascular bundle of the index finger is within the operative field and must be identified and protected. The surgeon must also be aware of the ulnar neurovascular bundle of the thumb. Dorsally, branches of the radial sensory nerve should also be recognized and preserved. Careful spreading dissection is recommended in these areas.
KEY PRINCIPLES • Transverse deficiency is defined by truncation of the upper extremity at a given level, caused by failure of proximal to distal limb formation due to AER injury (IFSSH class IA: failure of formation). • Symbrachydactyly is considered part of the spectrum of transverse deficiency. • Surgery is rarely indicated for forearm or proximal transverse deficiency. We recommend avoiding excision of rudimentary structures (invaginations and nubbins) unless they cause secondary problems or interfere with prosthesis fitting. • In hand-level transverse deficiency, including symbrachydactyly, surgeries may be indicated to improve prehensile function. In most cases, this should be limited to web space deepening techniques when indicated. Other procedures include vascularized toe-to-hand transfer, non-vascularized toe phalanx grafting, and bone lengthening with distraction osteogenesis.
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KEY REFERENCES 1. Buffart LM, Roebroeck ME, Pesch-Batenburg JMFB, Janssen WGM, Stam HJ. Assessment of arm/hand functioning in children with a congenital transverse or longitudinal reduction deficiency of the upper limb. Disabil Rehabil. 2009;28(2):85–95. 2. Wolfe SW, Pederson WC, Hotchkiss RN, Kozin SH, Cohen MS. Green’s Operative Hand Surgery. 7th ed. Philadelphia: Elsevier Churchill Livingstone; 2016. 3. Ogino T. Clinical features and teratogenic mechanisms of congenital absence of digits. Dev Growth Differ. 2007;49(6):523–531. 4. Neligan P, Chang J, eds. Plastic Surgery. 3rd ed. London: Elsevier Saunders; 2013. 5. Kallemeier PM, Manske PR, Davis B, Goldfarb CA. An assessment of the relationship between congenital transverse deficiency of the forearm and symbrachydactyly. J Hand Surg Am. 2007;32(9):1408–1412. 6. Blauth W, Gekeler J. Morphology and classification of symbrachydactylia. Handchirurgie. 1971;3(4):123–128. 7. Firth H. Chorion villus sampling and limb deficiency—cause or coincidence? Prenat Diagn. 1997;17(13):1313–1330.
8. Gardiner DM, Holmes LB. Hypothesis: terminal transverse limb defects with “nubbins” represent a regenerative process during limb development in human fetuses. Birth Defects Res A Clin Mol Teratol. 2012;94(3):129–133. 9. Jones NF, Kaplan J. Indications for microsurgical reconstruction of congenital hand anomalies by toe-to-hand transfers. Hand. 2013;8(4):367–374. 10. Netscher DT, Lewis EV. Technique of nonvascularized toe phalangeal transfer and distraction lengthening in the treatment of multiple digit symbrachydactyly. Tech Hand Up Extrem Surg. 2008;12(2):114–120. 11. Cavallo AV, Smith PJ, Morley S, Morsi AW. Non-vascularized free toe phalanx transfers in congenital hand deformities—the Great Ormond Street experience. J Hand Surg [Br]. 2003;28(6):520–527. 12. Patterson RW, Seitz WH. Nonvascularized toe phalangeal transfer and distraction lengthening for symbrachydactyly. J Hand Surg Am. 2010;35(4):652–658. 13. Furnas DW, Fischer GW. The Z-plasty: biomechanics and mathematics. Br J Plast Surg. 1971;24(2):144–160. 14. Woolf RM, Broadbent TR. The four-flap Z-plasty. Plast Reconstr Surg. 1972;49(1):48–51.
SYNOPSIS Congenital transverse deficiency of the upper extremity is a rare but disabling condition in which all elements beyond a given level in the extremity are absent. The most common level is the proximal forearm, but it can occur at any level from the humerus to the metacarpals. This chapter describes the disorder, presentation, and an approach to management of patients with this condition. Surgery is not indicated in most transverse deficiencies at the forearm level or more proximal, but there are several surgical techniques that can improve function in patients with hand-level transverse deficiencies including symbrachydactyly. Described in detail is the technique of four-flap Z-plasty for first web space deepening, along with the postoperative care, common complications, and their management.
CLINICAL PROBLEM Congenital transverse deficiency is a rare but severe condition in which the upper extremity is truncated at a given level and all normal elements beyond this are absent. The estimated incidence is between 15 and 60 per 100,000 live births.1 In transverse deficiencies, a portion of the limb is missing, but the proximal supporting structures are intact, although typically hypoplastic. This is in contrast to longitudinal deficiency, wherein the proximal supporting structures are absent or severely deficient.2 Historically, transverse deficiencies were often referred to as “congenital amputations,” but this is etiologically incorrect. As opposed to amniotic bands causing prenatal amputation of a limb that has already formed, transverse deficiency is considered a failure of formation of parts, type IA in the International Federation of Societies for Surgery of the Hand (IFSSH) system for congenital hand differences.3 The disorder is sporadic and is thought to be caused by disruption to the normal proximal-to-distal development of the extremity during embryological development of the upper limb.3 The management of transverse deficiencies requires an individualized approach, taking into account the level of the deficiency, current functional status, and the goals and desires of the child and family. In many cases throughout the world, surgical treatment is not indicated and children can adapt incredibly well to their differences with or without custom prosthetic devices. In particular, when the contralateral hand is unaffected, extensive reconstructive efforts are not usually indicated. In specific clinical situations, surgical interventions may be indicated to improve limb function. Examples include excision of nubbins or skin invaginations if causing secondary problems or interfering with
334
prosthesis fit. In hand-level deficiencies, procedures that increase effective digital length may allow or improve prehensile function. Most commonly, this entails web space deepening with local flaps and tissue rearrangement techniques. Other procedures include skeletal lengthening using distraction osteogenesis, and vascularized or non-vascularized toe transfers. This chapter will provide an overview of transverse deficiency and surgical procedures to improve hand function, with a more in-depth look at web space deepening techniques.
Presentation Patients with transverse deficiency present with congenital truncation of the upper limb, which may occur at any level from the humerus to the metacarpal. This may be detected on prenatal ultrasound examinations, or it may not be discovered until birth. Transverse deficiency can be differentiated from amniotic band syndrome (prenatal amputation), because osseous hypoplasia is a cardinal feature of the former but not the latter.3 The left upper extremity is affected twice as often as the right, and males are affected more commonly than females.4 The most common level of truncation is at the proximal forearm, followed by the transcarpal, distal forearm, and distal humerus levels.2 Rudimentary finger “nubbins” are often present at the distal end of the truncated extremity, regardless of the level of deficiency. These often have nail plates and variably present extrinsic tendinous structures. Skin invaginations may also be present at the terminal end of the limb, which can cause issues with hygiene or infections. Symbrachydactyly, a condition characterized by shortened or absent fingers with various degrees of fusion, is now considered to be a type of transverse deficiency occurring at the level of the hand, although it is still classified as an “undergrowth” abnormality by IFSSH.5 Symbrachydactyly was classified into four types by Blauth and Gekeler.6 Type 1, short finger type, is characterized by four shortened, syndactylized fingers with an essentially normal thumb. Type 2, oligodactylic type, is characterized by central clefting or aplasia. Type 3, monodactylic type, demonstrates absence of all fingers with a normal thumb. Type 4, peromelic type, presents with an absence of all digits at the metacarpal level (Fig. 5.4.1).
Etiology One of the most important roles of the hand surgeon is to convey accurate information to the parents of a child born with congenital limb differences regarding the etiology of a condition, and to help to dispel feelings of guilt or parental responsibility that are commonly present. Culturally appropriate education is critical, especially when working in another country. Transverse deficiency is usually sporadic,
CHAPTER 5.4 Transverse Deficiency
335
5 to 7 of gestation may lead to transverse deficiency. AER disruption is thought to be due to a vascular problem, either ischemia or bleeding, in most cases.2 It is theorized that rudimentary digits, or nubbins, may be a result of a prenatal regenerative response to intrauterine trauma.8 Morphologically, these nubbins are similar to the distal portions of fingers, and can form on the end of limbs that are missing all other terminal structures. They can be found on the distal end of the limb, regardless of the level of truncation. It is theorized that either portions of the AER survive the insult and lead to the generation of the nubbins, or that the AER itself partially regenerates and induces the formation of nubbins.8
Associated Conditions Transverse deficiency usually presents unilaterally in otherwise healthy children without other congenital differences. Symbrachydactyly, however, may be associated with Poland syndrome, in which absence of the sternal head of pectoralis major and other muscles of the shoulder girdle may be absent or deficient.5
PRE-OPERATIVE MANAGEMENT Physical Examination and Key Anatomy FIG. 5.4.1 Transverse deficiency at the level of the metacarpals, with a relatively preserved thumb. Rudimentary digital structures, or “nubbins,” are located at the terminal aspect of the limb and can be found in more proximal transverse deficiencies as well. (Reproduced from Tonkin M, Oberg K. Congenital hand I: Embryology, classification, and principles. In: Neligan P, Chang J, eds. Plastic Surgery, 3rd ed, vol 6. London: Elsevier Saunders; 2013.)
Fgfs (AER)
Stage 13
Stage 15
Stage 17
FIG. 5.4.2 The apical epidermal ridge (AER) is a signaling center covering the distal aspect of the developing limb. Through fibroblast growth factors, the AER orchestrates differentiation of the underlying mesenchymal development along the proximal-to-distal axis. (Reproduced from Tonkin M, Oberg K. Congenital hand I: Embryology, classification, and principles. In: Neligan P, Chang J, eds. Plastic Surgery, 3rd ed, vol 6. London: Elsevier Saunders; 2013.)
and subsequent children are not thought to be at increased risk of limb differences. There is an association with maternal intake of alcohol, tobacco, cocaine, or misoprostol, as well as riboflavin deficiency.2 There is also some evidence for an increased risk associated with chorionic villus sampling if the procedure occurs during the period of limb morphogenesis.7 Nearly all congenital upper limb differences arise between gestational day 26, when the limb bud appears, and day 53, when the fingers are fully separated.2 The longitudinal development of the upper limb is driven by the apical ectodermal ridge (AER), a signaling center on the distal aspect of the limb bud that acts through fibroblast growth factors (FGFs) to render proximal to distal limb development and finally interdigital necrosis (Fig. 5.4.2). The AER signals the differentiation of the underlying mesenchymal components of the limb bud, and is genetically programmed to induce appropriate differentiation through the time course of limb formation.8 A disruption of AER signaling during weeks
Transverse deficiencies should be characterized in terms of the level of truncation, and any associated distal rudimentary structures such as nubbins or invaginations. Furthermore, the function of adjacent joints such as the elbow and shoulder should be assessed and documented. In forearm-level transverse deficiencies, elbow flexion and extension are usually intact, but forearm rotation is commonly impaired by proximal radioulnar abnormalities. In patients with more distal transverse deficiencies at the hand or digit level, including those with symbrachydactyly, the functional usage of the hand should be determined. In particular, pinch and prehensile function should be assessed, because these functions may be restored or improved with surgical interventions. The best way to assess this in young children is to observe them playing with simple toys. The fundamental function of the hand, prehensile function, can be achieved with a mobile thumb able to oppose other parts of the hand. In symbrachydactyly, the central rays are always affected, with variable involvement of the thumb and small finger. Depending on the specific morphology of the patient, web space deepening procedures can significantly improve prehensile function, particularly deepening of the first web space. Procedures requiring highly specialized equipment such as microsurgical instruments or distraction devices may not be possible or advisable in some facilities.
Pre-Operative Testing Needed In forearm-level transverse deficiencies, standard x-rays of the elbow and forearm are generally the only diagnostic investigations required (Fig. 5.4.3). Proximal radioulnar abnormalities are commonly present in forearm-level deficiencies. In patients with hand-level truncation, including symbrachydactyly, x-rays are useful to understand the underlying skeletal abnormalities and to assess whether certain interventions such as distraction osteogenesis may be possible for the patient. No specific pre-operative investigations are needed before web space deepening procedures, but close observation of the patient using the hand to play or manipulate objects will guide the surgeon in choosing the appropriate intervention, if any.
Surgical Indications and Decision-Making Surgery is usually not indicated for transverse deficiencies at the wrist or proximal levels, except in specific cases described below. Often, the most helpful intervention of the hand surgeon is facilitating the
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opportunity to work with other providers including physical and occupational therapists, psychologists, rehabilitation specialists, and a prosthetist, who can equip the patient with a variety of different prostheses over time as the child grows and engages in various specific activities (e.g., swimming or racquet sports). Although some surgeons have offered early excision of rudimentary structures (nubbins or invaginations) from the terminal limb, most now recommend reserving excision for situations in which these cause secondary problems such as infections, nail issues, or interference with prosthetic fit. These structures may be useful for manipulating objects and for sensory feedback. Although parents may request excision of these structures, we recommend waiting until the child is older and has been evaluated by a rehabilitation team and prosthetists so that their input may be considered in the planning of any stump adjustments. Other procedures for forearm-level deficiencies have been described but are very uncommon. Forearm lengthening is associated with a high complication rate, and has not been shown to improve function. The Krukenberg procedure, where the forearm bones are separated to convert
FIG. 5.4.3 Standard x-rays of the elbow in a patient with a very proximal forearm-level transverse deficiency. (Reproduced from Smith G, Smith P. Congenital hand II: Disorders of formation (transverse and longitudinal arrest). In: Neligan P, Chang J, eds. Plastic Surgery, 3rd ed, vol 6. London: Elsevier Saunders; 2013.)
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the forearm stump to a pincer, is indicated in only very rare circumstances due to the highly unfavorable cosmetic appearance. It is traditionally indicated for bilateral amputees with blindness, because these patients cannot use traditional prostheses due to the lack of visual or tactile feedback.2 In hand-level transverse deficiencies, including symbrachydactyly, surgery is more frequently indicated because deepening web spaces or lengthening digits may improve prehensile function. When the contralateral hand is unaffected, surgery should generally be limited to less complex procedures such as web-deepening procedures and soft tissue release. More complex techniques include free vascularized toe-to-hand transfers, non-vascularized toe phalangeal bone grafts, and distraction osteogenesis for skeletal lengthening. Determining which lengthening procedure is most appropriate depends on what structures are absent and present, available resources, surgeon experience and ability, and the ability of the patient and family to comply with the post-operative course. Free vascularized toe-to-hand transfer may be an option for certain patients with necessary proximal skeletal support and extrinsic tendons, which are variably present in transverse deficiencies.9 Example indications would be an absent thumb or a preserved thumb with an absence of other digits to oppose to (Fig. 5.4.4). Disadvantages of this technique include technical difficulty, lengthy surgery and recovery, donor site morbidity, and the need for microsurgical skills and equipment. Multiple simultaneous toe transfers can be performed to a single hand. In children 15 months or younger, non-vascularized toe phalangeal bone transfers to digits of the hand may be useful to augment length and skeletal support.10 This technique is not advised in older patients, because the grafts typically resorb. Non-vascularized toe phalanx transfers are most useful in patients in whom digital skeletal elements are hypoplastic but the soft tissue envelope is relatively preserved. Reports of growth of the grafts over time have been highly variable, and some authors have even performed later distraction osteogenesis on the grafted bone.11,12 Distraction osteogenesis (also known as callus lengthening or callotasis) for lengthening of hand bones is a technique where a specialized external fixation device is applied to the bone, an osteotomy is made, and the bone and soft tissues are gradually lengthened over time through callus formation and soft tissue creep (Fig. 5.4.5). In symbrachydactyly, modest
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FIG. 5.4.4 (A) Free vascularized toe-to-hand transfer for reconstruction of index finger in a patient with a relatively preserved thumb. (B) Prehensile function is achieved. (Reproduced from Smith G, Smith P. Congenital hand II: Disorders of formation (transverse and longitudinal arrest). In: Neligan P, Chang J, eds. Plastic Surgery, 3rd ed, vol 6. London: Elsevier Saunders; 2013.)
CHAPTER 5.4 Transverse Deficiency
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FIG. 5.4.5 (A) A 4-year-old male with transverse deficiency at the
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metacarpal level of the right upper extremity. Note the relatively unaffected thumb. The remaining four fingers are rudimentary, with some development of the index and middle proximal phalanges, and only nubbins for the ring and small digits. (B) Photograph and (C) x-ray after osteotomy of second metacarpal and application of distractor device. (D) Photograph and (E) x-ray after distraction of 25 mm and 7 weeks of consolidation.
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FIG. 5.4.6 Illustration of a four-flap Z-plasty designed to deepen the first web space. (Reproduced from Vedder NB, Friedrich JB. Thumb reconstruction: Nonmicrosurgical techniques. In: Neligan P, Chang J, eds. Plastic Surgery, 3rd ed, vol 6. London: Elsevier Saunders; 2013.)
gains in metacarpal or phalanx length may allow or improve prehension. Examples include lengthening a thumb so that it can reach the other digits, or lengthening a second or third ray so that the digit may reach the thumb. Distraction lengthening is a difficult and time-consuming process for young children and their families to undergo, and it may not be a good option for many, particularly in the developing world. The remainder of this chapter will focus on the technique of web space deepening using local flap techniques. Widening and deepening of the first web space in particular can allow for increased thumb mobility and opposition to other digits. These procedures attempt to create a scar-free web line, and thus place incisions crossing the web space obliquely. Simple Z-plasty may occasionally be adequate, but in most cases it does not create an appropriate contour and may leave a depression at the base of the first web space.13 Simple Z-plasty can be useful for web spaces other than the first, however. The four-flap Z-plasty is a reliable technique for first web space deepening that creates a predictable contour and allows sufficient release (Fig. 5.4.6).14 A five-flap Z-plasty (or “jumping man”) can also be effective, but the flaps are narrower and thus the tips more vulnerable to necrosis (Fig. 5.4.7). More severe web space narrowing may require transfer of larger amounts of tissue, such as with flaps from the dorsal hand (e.g., first dorsal metacarpal artery flap) or from the forearm (posterior interosseous artery or reverse radial forearm flap). These procedures are more technically demanding and have more conspicuous donor sites. Fortunately, local flap procedures are usually sufficient. In terms of surgical timing for web space deepening, there are no published guidelines for symbrachydactyly, but the syndactyly literature suggests waiting until the child is 18 months old, unless the growth disturbance or progressive deformity dictates earlier intervention. Anesthesia becomes safer after 1 year of age, and surgery may be less technically demanding due to growth of the hand. A general goal is completion of surgeries before school age.2
SURGERY Procedure—First Web Space Deepening With Four-Flap Z-Plasty The patient is supine with the arm abducted on a hand table. The procedure is performed under general anesthesia with tourniquet control. Regional anesthesia can be considered for older children or adults.
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FIG. 5.4.7 Illustration of the double opposing Z-plasty, or “jumping man” flap, an alternative design for first web space deepening or contracture release. (Reproduced from Vedder NB, Friedrich JB. Thumb reconstruction: Nonmicrosurgical techniques. In: Neligan P, Chang J, eds. Plastic Surgery, 3rd ed, vol 6. London: Elsevier Saunders; 2013.)
With the thumb and index finger maximally abducted, the central limb of the Z-plasty is marked along the edge of the web (Fig. 5.4.8A and B). The length of the central limb determines the length of all of the other limbs. Extension of this limb onto either the ulnar thumb or radial index finger surfaces should be avoided. Next, a perpendicular limb of the same length is drawn, arising at the radial-most aspect of the central limb and running proximally on the dorsal hand, parallel to the first metacarpal. A second perpendicular limb is then drawn, arising at 90 degrees from the ulnar-most aspect of the central limb and running volarly near the thenar crease. The two right angles are then bisected with 45-degree limbs, creating four equal triangular flaps. Two of these flaps are on the dorsum, and two are on the volar, glabrous surface of the hand. The volar flaps should be raised first, because it is easier to make small adjustments to the more mobile dorsal skin flaps. The volar flaps are incised and then raised in the suprafascial plane using careful spreading dissection. The radial digital neurovascular bundle of the index finger and ulnar bundle of the thumb must be identified and protected. Next, the dorsal skin incisions are made, and the flaps are raised suprafascially while protecting the small branches of the radial sensory nerve and any longitudinal veins. If the fascia of the first web is constricting, it should be released as well (Fig. 5.4.8C). A small amount of muscle can be resected to further deepen the web space. When well designed and completely dissected, the Z-plasty flaps should easily transpose to their new positions. Minor flap adjustments are typically required before inset (Fig. 5.4.8D). In children, we typically use absorbable monofilament (5-0 fast- absorbing gut) sutures (Fig. 5.4.8E). The four-flap design should create a natural concave contour in the first web space. Incisions are covered with a non-stick gauze, and a well-padded thumb spica splint or cast is applied with the thumb radially and palmarly abducted and the interphalangeal joint free. In children younger than school age, long arm splints are less likely to be removed by the patient.
POST-OPERATIVE CARE The post-operative splint is removed at 2 weeks so that the surgical site can be examined. A custom thermoplastic web spacer splint
CHAPTER 5.4 Transverse Deficiency
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FIG. 5.4.8 Technique of four-flap Z-plasty. (A) Dorsal view of first web space showing tight contracted band. (B) Skin markings for a four-flap Z-plasty, with the central limb marked on the tight web and two 90-degree perpendicular incisions at the ends of this limb. These 90-degree angles are then bisected at 45 degrees to form four triangular flaps. (C) Tight fascial bands may be identified dorsally after raising the skin flaps. If constricting, these must be released as well. (D) Inset of flaps after trimming and minor flap adjustments. The volar flaps are thicker and more rigid, and it is often easier to make adjustments to the more mobile dorsal skin flaps. A standing cone deformity has been removed with the extension at the radial side of the index finger. (E) Postoperative appearance showing the contour provided by the four-flap Z-plasty technique. (Reproduced from Upton III, J, Taghinia A. Congenital hand III: Disorders of formation – thumb hypoplasia. In: Neligan P, Chang J, eds. Plastic Surgery, 3rd ed, vol 6. London: Elsevier Saunders; 2013.)
is then fabricated. The patient is gradually weaned from this over 3 to 4 weeks.
MANAGEMENT OF COMPLICATIONS Complications of first web space deepening include infection, wound healing problems, nerve injury, hematoma, and flap necrosis. Necrosis of the tips of Z-plasty flaps can occur if the flaps are narrow or the angles too acute. The flaps should be raised full thickness in the suprafascial plane to preserve their vascularity. When raising the volar flaps, the radial digital neurovascular bundle of the index finger is within the operative field and must be identified and protected. The surgeon must also be aware of the ulnar neurovascular bundle of the thumb. Dorsally, branches of the radial sensory nerve should also be recognized and preserved. Careful spreading dissection is recommended in these areas.
KEY PRINCIPLES • Transverse deficiency is defined by truncation of the upper extremity at a given level, caused by failure of proximal to distal limb formation due to AER injury (IFSSH class IA: failure of formation). • Symbrachydactyly is considered part of the spectrum of transverse deficiency. • Surgery is rarely indicated for forearm or proximal transverse deficiency. We recommend avoiding excision of rudimentary structures (invaginations and nubbins) unless they cause secondary problems or interfere with prosthesis fitting. • In hand-level transverse deficiency, including symbrachydactyly, surgeries may be indicated to improve prehensile function. In most cases, this should be limited to web space deepening techniques when indicated. Other procedures include vascularized toe-to-hand transfer, non-vascularized toe phalanx grafting, and bone lengthening with distraction osteogenesis.
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KEY REFERENCES 1. Buffart LM, Roebroeck ME, Pesch-Batenburg JMFB, Janssen WGM, Stam HJ. Assessment of arm/hand functioning in children with a congenital transverse or longitudinal reduction deficiency of the upper limb. Disabil Rehabil. 2009;28(2):85–95. 2. Wolfe SW, Pederson WC, Hotchkiss RN, Kozin SH, Cohen MS. Green’s Operative Hand Surgery. 7th ed. Philadelphia: Elsevier Churchill Livingstone; 2016. 3. Ogino T. Clinical features and teratogenic mechanisms of congenital absence of digits. Dev Growth Differ. 2007;49(6):523–531. 4. Neligan P, Chang J, eds. Plastic Surgery. 3rd ed. London: Elsevier Saunders; 2013. 5. Kallemeier PM, Manske PR, Davis B, Goldfarb CA. An assessment of the relationship between congenital transverse deficiency of the forearm and symbrachydactyly. J Hand Surg Am. 2007;32(9):1408–1412. 6. Blauth W, Gekeler J. Morphology and classification of symbrachydactylia. Handchirurgie. 1971;3(4):123–128. 7. Firth H. Chorion villus sampling and limb deficiency—cause or coincidence? Prenat Diagn. 1997;17(13):1313–1330.
8. Gardiner DM, Holmes LB. Hypothesis: terminal transverse limb defects with “nubbins” represent a regenerative process during limb development in human fetuses. Birth Defects Res A Clin Mol Teratol. 2012;94(3):129–133. 9. Jones NF, Kaplan J. Indications for microsurgical reconstruction of congenital hand anomalies by toe-to-hand transfers. Hand. 2013;8(4):367–374. 10. Netscher DT, Lewis EV. Technique of nonvascularized toe phalangeal transfer and distraction lengthening in the treatment of multiple digit symbrachydactyly. Tech Hand Up Extrem Surg. 2008;12(2):114–120. 11. Cavallo AV, Smith PJ, Morley S, Morsi AW. Non-vascularized free toe phalanx transfers in congenital hand deformities—the Great Ormond Street experience. J Hand Surg [Br]. 2003;28(6):520–527. 12. Patterson RW, Seitz WH. Nonvascularized toe phalangeal transfer and distraction lengthening for symbrachydactyly. J Hand Surg Am. 2010;35(4):652–658. 13. Furnas DW, Fischer GW. The Z-plasty: biomechanics and mathematics. Br J Plast Surg. 1971;24(2):144–160. 14. Woolf RM, Broadbent TR. The four-flap Z-plasty. Plast Reconstr Surg. 1972;49(1):48–51.