27 Congenital hand III
Disorders of formation – thumb hypoplasia
Although new procedures have expanded options for reconstruction, standard procedures such as first web space deepening, tendon transfers, and collateral ligament reconstruction remain predictable and reliable.
The hypoplastic thumb represents a wide spectrum of functional and aesthetic differences. Before classification and management of the deficient thumb, a careful surgeon must assess its: (1) size; (2) position; (3) relation to other fingers of the hand; (4) osseous components; (5) joint integrity and stability; (6) intrinsic and extrinsic musculotendinous units; (7) first web space depth and width; (8) associated malformations of the hand and elsewhere, and (9) functional consequences for the child. A thumb should be considered hypoplastic when there is a deficiency of any one or all structures that contribute to the “normal” thumb. In the past, all definitions were restricted to the radiographic appearance alone; however, presently, we understand that soft tissue deficiencies also contribute to the overall diagnosis.
For the first 3 months of life, the thumb is adducted and flexed within the palm and serves primarily as a pacifier. By 9 months of age, though, this first ray gains its independence and mobility from the palm, and at a year of age, it has become a crucial portion of the hand.1 In the normal hand, the strength and mobility needed for a wide variety of pinch and grasp functions rapidly develop, and by the time the baby is ambulatory, the thumb is used creatively and independently to manipulate the environment.
As relied upon in the past, a complete evaluation of the osteoarticular column will require plain radiographs. Normal primary ossification centers of the phalanges and metacarpal of the thumb appear in the second to fourth fetal months, but abnormalities of the skeleton of the thumb (e.g., triangular bones) may not be seen radiographically until well into the first or second year of life. Secondary ossification centers within the epiphyses of the thumb normally appear between 13 months to 4 years of age.2 The delayed appearance of both primary and secondary ossification centers in the hypoplastic thumb is highly relevant to the diagnostic process because their appearance is often delayed in proportion to the degree of hypoplasia.
The history of thumb reconstruction mirrors the development of hand surgery as a subspecialty. As such, advances in diagnosis, classification, and treatment of these conditions are relatively new – having occurred in the past 5–6 decades. Because many children with thumb anomalies have more serious conditions, advances in anesthesia also had to take place in order to make surgery safer and more predictable.
In terms of diagnosis and classification, Flatt stressed function potential and designated the digits as “adequate” or “inadequate”3; Bayne relied upon localized positions or deficiencies4; and three generations of German authors referred to the degree of skeletal hypoplasia.5–7 The latter of these three systems recognizes the progressive degree of hypoplasia from a slight size discrepancy, with all normal structures present, to total aplasia of the thumb. In time, this system has been amended by others,8,9 who subdivided type III (severe hypoplasia) into two groups – those with an intact CMC joint (IIIA) and those without (IIIB) – and is very important in terms of management.
Progress in the treatment of thumb hypoplasia mirrored advances in diagnosis and classification. Working independently in Europe, Gosset10 and Hilgenfeldt11 developed the procedure of digital transposition for post-traumatic thumb losses. In the decades following World War II, Bunnell described similar digital transpositions.12 Littler13 refined their techniques and applied them to congenital differences. Following the thalidomide crisis in Europe, Buck-Gramcko14 amassed a large clinical experience and set present day standards for pollicization.
The true incidence of thumb hypoplasia is difficult to determine due to the large number of congenital malformations within which a hypoplastic thumb is a component part. All reported reviews are subject to study of the genetic composition of the patient population as well as any discrepancies of nomenclature and sampling. Entin15,16 reported a 16% incidence of thumb hypoplasia in his Canadian patients, while Flatt published an 11.2% incidence of thumb abnormalities and a 3.6% incidence of thumb hypoplasia or aplasia.3 We have seen a 37% incidence within our entire registry, which includes many additional categories.17 The majority of the children treated surgically are those with radial dysplasia – with and without a partial or complete absence of the radius. We have also seen a large incidence in syndromic patients, such as those with the Apert syndrome, who are commonly referred to large children’s hospitals for treatment of their multiple malformations.
Because radial or preaxial longitudinal deficiencies occur in many conditions with a wide variety of etiologies, the causes for these malformations span the entire spectrum of genetic, environmental, teratogenic and other factors (Table 27.1). Therefore, consultation with a genetic specialist is strongly recommended, and referral to standard genetic textbooks or the OMIM website18 is a must for any responsible hand surgeon.
|Frequent in||Occasional in|
|Metacarpal hypoplasia – firstc, alld|
The a,b,c,d refers to the hypoplasia/aplasia associations of the listed syndromes. For example, Aase syndrome has both thumb and radial hypoplasia but Nager syndrome has just thumb hypoplasia.
Modified from Jones KL. Smith’s recognizable patterns of human malformations, 5th edn. Philadelphia: WB Saunders; 1997.
The many potential associations with thumb and radial hypoplasias and aplasia may involve any organ system within the body. Most significant are those with the cardiovascular, gastrointestinal and genitourinary involvement. Associated hematologic problems, specifically Fanconi anemia, can be detected early but usually become clinically apparent later in childhood. The most common of these associated conditions is outlined herein.
These children may have a wide spectrum of anomalies, including: Vertebral malformations; Anal atresia or hypoplasias; Cardiovascular anomalies; all degrees of Tracheoesophageal fistuli; Esophageal atresia; Renal malformations, and Limb abnormalities – which in the upper extremity involve all degrees of radial dysplasia. A patient does not need to fulfill every category on this list to be considered VACTERL.
Fanconi (FA) children develop all degrees of a pancytopenia, which can be life-threatening.20,21 Most are small with slow growth. Although many other organ systems may be abnormal, deficiencies of the thumb and, to a lesser extent, the entire radial ray are the most common and are present at birth in over half of these cases. Although in the past FA children were rarely diagnosed early in life, this condition can now be diagnosed at birth with a DEB test.20,22 However, because this test involves an unstable gas, butane, it is not available in all medical centers. Other types of treatable childhood anemias, such as the Blackfan type, may occur in the later childhood years and are easily distinguished by routine hematologic tests including the DEB.21 Treatment of FA children with oxymetholone and prednisone therapy has a 70% response rate, and nonresponders can be treated with bone marrow transplantation.20
Two pediatricians, Dr Holt in Philadelphia and Dr Oram in London, independently described the association of congenital heart disease and radial longitudinal defects of the upper limb, and their names have subsequently been associated with all degrees of congenital cardiovascular malformations and radial dysplasias. Interestingly, there is no correlation between the severities of the anatomic deficiency in one system relative to the other. Common to the upper limbs are a stiff hypoplastic thumb joined to a stiff index digit by a complete simple syndactyly, radial deficiencies, and proximal radioulnar synostoses. Often, hypoplasia of the glenohumeral joint is not diagnosed until adolescence when shoulder abduction is diminished.
This unique group of children may be born with normal hematologic parameters, but they usually have a low platelet count, which may decrease rapidly during the first year of life. They are easily distinguished from other types of radial dysplasia due to the presence of a thumb despite all degrees of radial deficiencies. The thumb is hypoplastic, and extrinsic flexion and extension vary tremendously. Thenar intrinsic muscles are usually present and provide some palmar abduction by age 2 years of age. The low platelet count commonly reaches normal levels by ages 4–5 years, and the clinical results from centralization are among the best.
The varying degrees of differences between hypoplastic thumbs have been classified in a number of ways that have few common characteristics.23 Nevertheless, a well-accepted classification system has emerged that guides treatment. The five designated types of thumb hypoplasia-aplasia are shown in Figure 27.1. These anomalies are commonly associated with radial (preaxial) dysplasia, and the majority of congenital hand surgeons consider most types of thumb with a normal radius as part of this spectrum. It is well recognized that there are concomitant soft tissue anomalies that accompany the skeletal abnormalities. Since the correlation of soft tissue and skeletal deficiencies has been so well defined, this refined system works very well for clinical decision-making.
Fig. 27.1 Thumb hypoplasia. Molds of the right hand in six children with the five classic types of thumb hypoplasia are displayed. Type III has been subclassified into two categories: one with (IIIA) and intact CMC joint and one without (IIIB) an intact CMC joint. The type IV is often called the pouce flottant or floating thumb.
Hypoplasia of the thumb is associated with many other congenital differences, specifically central and transverse deficiencies. Because the anatomical make-up of the thumb does not always allow for easy categorization under the current system, we have included five additional categories,17 which include the constriction ring syndrome, central deficiencies, radial duplication, the five-fingered hand, and short skeletal rays. In these conditions, the thumb ray usually has characteristic deficiencies that would fall into the German type II and III hypoplasia categories24 and the anatomical abnormalities relevant to clinical decision-making will be presented here.
In the past, routine radiographs were the sole tool used for diagnosis of the hypoplastic thumb. However, this mode of assessment did not reveal any detail about the normal and abnormal soft tissue structures of individual hands. Therefore, surgeons today use a more complete analysis of intrinsic muscles, web space size, intrinsic muscles, extrinsic tendons, joint stability, and function – all of which impact directly upon treatment.
In this most mild type of hypoplasia, the thumb is slender and slightly shorter than a normally configured first ray (Fig. 27.2). The phalanges and metacarpal can be slightly thinner than usual, but the trapezium and scaphoid are present and the distal radius and styloid process are not affected. The interphalangeal (IP), metacarpophalangeal (MP), and carpometacarpal (CMC) joints are stable and exhibit normal passive and active motion. While there may be a slight hypoplasia and weakness of the abductor pollicis brevis (AbPB), opponens pollicis (OP) and lateral head of the flexor pollicis brevis (FPB) muscles, all intrinsic muscles are present.24 The joints, ligament and capsules, tendons, nerves, and vascular structures are all normal, and there may be minimal narrowing of the first web space.
Fig. 27.2 Type I thumb hypoplasia-mild. (A) The skeletal ray is well segmented and may be short. All intrinsic muscles and extrinsic tendons are intact. First web space narrowing is minimal to moderate. (B) Clinical appearance and (C) radiograph of a child who did not require any surgical correction. Although his thenar muscles are weak, there were no significant functional problems.
The metacarpal and phalanges are all present but small, and the trapezium, trapezoid, scaphoid, and – to a lesser extent – lunate may be hypoplastic. The first web space is short with the thumb adducted, the ulnar collateral ligament at the MP joint lax, and median innervated thenar muscles underdeveloped or occasionally absent (Fig. 27.3).25 Normally, the flexor pollicis brevis (FPB) and opponens pollicis (OP) are innervated by the median nerve, but the FPB varies, reported to be 40% median, 48% ulnar, and 12% both median and ulnar.26 The ulnar innervated intrinsics, particularly the adductor pollicis (AddP), pull the metacarpal into adduction and narrow the first web space, which when explored surgically has tight fibrous bands between muscle groups. Type II thumbs contain two neurovascular bundles, and the recurrent motor branch of the median nerve is consistently found.
Fig. 27.3 Type II thumb hypoplasia-moderate. (A) There is minimal to moderate shortening of the skeletal ray. All bones are present and ligaments at the MP joint may be lax. The ulnar innervated intrinsic muscles, AddP and first DI (second metacarpal origin) are strong, and the median innervated intrinsics are very weak. Anomalous anatomy is common. Adduction contractures from fibrous structures and MP joint instability accompany a deficient first web space. (B) Clinical appearance and radiograph of a child with a type II hypoplasia of the right hand. The thenar intrinsic muscles are hypoplastic, the first web space tight, and the thumb much narrower than normal. Key pinch was weak, and the patient could not hold heavy objects between the thumb and digits. In addition, the ulnar collateral ligament was weak at the MP joint.
Many different muscle and tendon anomalies seen on the radial side of the hand have been identified in conjunction with the type II and IIIA thumbs. In fact, the clinical designation of a given thumb may vary greatly due to this large spectrum of soft tissue abnormalities. Obviously, the absence of interphalangeal (IP) or metacarpophalangeal (MP) flexion or extension creases in a slender thumb is the best clinical indicator of flexor and/or extensor abnormalities. Within this designation, many variations of the long flexor to the thumb (FPL) may be found. Both the tendon and the muscle belly of the FPL may be abnormal,27 may have proximal duplications,28–32 and may have a more radial distal insertion.30 In some patients, one can observe this muscle originating from the index profundus tendon,29 the transverse carpal ligament, or the fascia of the thenar intrinsics and inserting into the flexor sheath28 and/or the extensor mechanism.33 In other cases, this muscle may be absent entirely.9,34–38 Some of these anomalies may represent abnormal radial wrist extensors or short thumb abductors instead of malformed or malpositioned terminal thumb flexors.39 Occasionally, a small abnormal “musculus lumbricalis pollicis” muscle may extend from the thumb origin across the first web space and attach to the flexor system of the index finger.40 We have seen this peculiar (atavistic) muscle extending across the first web space in children with the Freeman–Sheldon syndrome and in complex thumb duplications at the metacarpal level.
In addition, the extrinsic extensors may have abnormal insertions,41,42 extend over the MP joint in a noncentralized position, and reveal abnormal connections with the extrinsic flexor.31,33,40,43 These abnormal insertions of both flexor and extensors, combined with their deviated course, conspire to make both tendons act primarily as radial deviators and not primary flexors or extensors. In addition, the lax ulnar collateral ligament at the MP joint results in an abduction of the phalangeal portion of the thumb. Tupper has called this “pollex abductus” and noted that when these muscles contract, there is no IP flexion or extension, only abduction or radial deviation of the thumb. Many anatomical variations of this structure exist, but the functional result is the same (Fig. 27.4). A recent paper by Graham et al. has summarized the large list of muscle and tendon abnormalities, which often originate in the forearm.31 Although type II thumbs may present with these intra-tendinous connections, the abducted posture and wide degree of muscle and tendon anomalies are primarily seen with type IIIA thumbs (Fig. 27.4). When followed proximally to the wrist and forearm level, many of these tendons have abnormal origins and long muscle bellies that extend well beyond the wrist into the metacarpal region.
Fig. 27.4 Pollex abductus. (A) In severe type II and many type III thumbs, there may be very little, if any, IP joint flexion and there may be a radial deviation of the thumb at the MP joint. This is due to the abduction force created by the combined action of the extrinsic flexor and extensor tendons joined by intertendinous connections, the “pollex abductus.” (B-E) Within types II and III thumb hypoplasias (and proximal thumb polydactylies), a very wide spectrum of intra-tendinous connections may vary between a wide, loose, almost areolar band (top) to a complete coalition the flexor and extensor into a single tendon. With excursion from either the flexor or extensor side, the resultant movement in all these thumbs is abduction of the MP joint.
In these cases, the degree of skeletal shortening and narrowing is much more pronounced, particularly at the metacarpal level (Figs 27.5, 27.6). The hand and wrist may be radially deviated due to hypoplastic/aplastic carpal bones. The trapezium is usually very small, and frequently the scaphoid is absent. The distal radius is smaller in size and the styloid process absent, giving the radius a blunted appearance.44 The extreme amount of anatomic variation within this group prompted Manske and colleagues to subdivide this group into type III-A with a full-length metacarpal and an intact CMC joint and type III-B with a tapered first metacarpal and no CMC joint.45 Buck-Gramcko has included an additional variation which we shall call type III-C thumb which possesses only the metacarpal.46 There are no tendons or muscles in this variant, and the skin bridge is much wider than that seen in type IV. In the B and C variants, a fibrous band may connect the hypoplastic metacarpal to a cartilaginous nubbin that represents either a trapezium or metacarpal base. Often, a small abductor pollicis tendon attaches to this remnant.
Fig. 27.5 Type IIIA thumb hypoplasia-severe. (A) These thumbs exhibit more severe skeletal hypoplasia, including the carpal bones. Median nerve innervated thumb intrinsic muscles are severely hypoplastic or absent, and the ulnar-innervated muscles are present but weak. Extrinsic tendons are abnormal, the “pollex abductus” deformity is frequent, the first web space is small, and the MP joint is unstable (more on the ulnar than the radial sides). The CMC joint and thumb metacarpal are intact in IIIA thumbs. (B-E) The clinical appearance and radiograph show a short slender metacarpal, an intact CMC joint, severe hypoplasia of the thenar eminence and a lax MP joint. The absent IP flexion crease is indicative of a deficient or absent FPL.
Fig. 27.6 Type IIIB thumb hypoplasia-severe. (A) The median- innervated thenar intrinsic muscles are absent entirely. There is severe hypoplasia of the AddP, FPB-lateral head, and the ulnar origin of the first DI. The CMC joint articulation of the proximal metacarpal is absent. The MP joint is very lax or absent on both radial and ulnar sides. Flexor and extensor extrinsic tendons are severely hypoplastic or absent. (B, D) Clinical appearance and (C) radiograph shows a 4-year-old patient with a well formed but functionless floppy thumb. There is no skeletal stability or extrinsic flexion or extension. Very small flexor or extensor tendons may be present and can result in some movement.
Median innervated intrinsic muscles are either severely hypoplastic or absent entirely; however, if they are present, they may actively flex the MP joint. The ulnar innervated adductor pollicis (AddP) pulls the metacarpal medially. The MP joint is lax on both radial and ulnar sides and anatomically either collateral ligament and the volar plate may be severely hypoplastic or missing. The small thumb with a short web space is abducted at the MP joint due to the frequent pollex abductus deformity. The radial origin of the first dorsal interosseous from the thumb metacarpal is more severely affected than that from the index metacarpal. In the forearm, radial head is usually hypoplastic and commonly subluxed, occasionally dislocated.
Abnormal anatomy is the rule. The many intrinsic and extrinsic anatomical variations described within the type II group may exist with greater degrees of hypoplasia. Usually, the extrinsic flexor and extensor are present and weak, but in some cases they may be missing.34,38,41 The flexor retinaculum is poorly developed with either attenuation or absence of the major pulleys. In some patients, the motor branch of the median nerve is absent, and there may only be one neurovascular bundle.29 The radial origin of the first dorsal interosseous to the index finger is severely hypoplastic, and the first web space is severely restricted. Pollex abductus anomalies are common and must be recognized if IP flexion and/or extension is to be achieved.
These thumbs (pouce flottant, French; pendeldaumen, German) arise distally from the palm and usually lie along the radial midaxial border (Fig. 27.7). They are attached only by a soft tissue pedicle, which has been described by Littler as “Nature’s own neurovascular pedicle,” due to the presence of a digital artery, two vena comitantes, and one or two nerves within the skin bridge.47 There may be anomalous vascular or neural rings, involving neurovascular structures1,5 that could affect the outcome of a pollicization. There is no metacarpal, and two small phalanges tend to be present within the soft tissue envelope, which contains a nail. It is important to note that a diminutive nail represents the presence of a distal phalanx. Intrinsic muscles do not insert onto these bones. A first dorsal interosseous muscle (abductor indicis) may be detected by abduction of the index finger. At the carpal level, the trapezium and less often the scaphoid are missing. The radial styloid may be absent, but the distal end of the radius is normal in most of these children.
Fig. 27.7 Type IV thumb hypoplasia-floating thumb. (A) The hypoplastic thumb is attached to the hand only by a soft tissue bridge, which contains neurovascular structures and rarely hypoplastic tendons and fascia. There is no skeletal connection. (B, C) The attached thumb is small with diminutive phalanges and a nail. There is no active flexion or extension. The radial deviation of the wrist and hand is due to hypoplasia of the trapezium, scaphoid and lunate.
The thumb is completely absent in this category (Fig. 27.8). In half of our patients48 and half those reported by Flatt,49 there is an associated deficiency of the radius. When the radius is normal, the index digit is normal and has strong abduction at the MP joint due to the presence of a strong first dorsal interosseous muscle (e.g., abductor indicis). Many of these children with a normal radius will demonstrate “auto pollicization.” The pulp of the index finger widens and the digit pronates and sits in a more abducted position resulting in a widening of the intermetacarpal space and attenuation of the intermetacarpal ligament. At best, this posture is a poor substitute for normal key pinch. In the case of a deficient radius, the index ray is stiffer, shorter, and often joined by a simple syndactyly to the long digit. There is a direct correlation between the degree of radial hypoplasia and the index finger deficiencies; the index ray is never normal when there are significant associated radial deficiencies. In these hands, the degree of stiffness decreases from the radial to the ulnar digits and the fifth finger is always the best on the hand.
Fig. 27.8 Type V thumb hypoplasia-aplasia. (A-C) With complete aplasia, no thumb structures are present. In approximately half of these patients, the radius is normal. The trapezium, trapezoid, and scaphoid are often hypoplastic and a strong 1st DI (abductor indicis) pulls the index digit in abduction and in as much pronation as the intermetacarpal ligament will allow. (D-F) Index digits, which are not abducted, are often stiff at the interphalangeal joints and are commonly associated with some degree of radial hypoplasia or aplasia. The amount of stiffness decreases from radial to ulnar digits. Accordingly, the ring and small fingers are always the most functional components of these hands.
Cleft hand is characterized by hypoplasia or aplasia of the central ray(s) of the hand thus forming a “V” or funnel-shaped cleft (Fig. 27.9). All degrees of simple syndactyly of the first web are seen, resulting in moderate to severe deficiencies of the first web space. In addition, all degrees of hypoplasia, extending to aplasia of the central two rays, may exist.9 The ulnar two digits in the ring and fifth positions are commonly webbed with simple syndactylies. The thumb in the cleft hand anomaly is usually slightly small with all components of the osteoarticular skeleton present. A Blauth type II thumb classification would be appropriate for the strict constructionist.24 The wrist and forearm bones are normal, and the median innervated thenar intrinsics are present. The major deficiency of the thumb in this form of hypoplasia is that the ulnar innervated intrinsic muscles are severely hypoplastic or absent. In particular, the ulnar innervated adductor pollicis is usually severely hypoplastic or absent, and the first dorsal interosseous is moderately hypoplastic and contracted. The presence or absence of the third metacarpal is often an excellent indicator of the status of the adductor pollicis muscle. Finally, the extrinsic flexor and extensor musculotendinous units to the thumb tend to be unaffected.
Fig. 27.9 Thumb in typical cleft hand. (A) Three layers of median innervated intrinsic muscles are present in most typical cleft hands. Commonly, the index ray is joined to the thumb by a simple syndactyly. All degrees of absence of the long rays may present. The first dorsal interosseous is present and tight, and the degree of adductor pollicis hypoplasia is proportional to the amount of the third metacarpal present. A very small adductor pollicis is illustrated here. (B) A sampling of molds shows the wide variation in the size and depth of the central clefting. The thumbs are smaller than normal, and the longer thumbs with flexion contractures are triphalangeal.
In another variation of typical cleft hand, thumb polydactylies at all levels may be observed. The more distal type I and II polydactylies50 are often associated with the absence of index phalanges that have an intact metacarpal. Super digits and transversely oriented tubular bones at the distal metacarpal level with complete absence of the index (and long) digits are often seen in this variation51 With more proximal type III, IV and V polydactylies, the central (third) ray is often severely hypoplastic or absent.52,53 Triphalangeal rays may also be encountered with the proximal duplications at the metacarpal level.
We refer to these atypical cleft hands as symbrachydactyly (Fig. 27.10). This form of deficiency is always unilateral, with varying degrees of hypoplasia of the central three rays of the hand. Nubbins with minute nail complexes may be present on the distal border of the palm, representing the index, long and ring fingers, but commonly these central three digits are completely absent with varying degrees of hypoplasia of the central three metacarpals.
Fig. 27.10 Symbrachydactyly thumb (atypical cleft). (A) The border thumb and fifth rays are the most complete in the hand. Thenar and hypothenar muscles are present and often small. Central digits are represented by hypoplastic nubbins. There are all degrees of metacarpal hypoplasia within the central three rays of the hand. Extrinsic flexors and extensors are present but abnormal. (B) A very wide range of variation is present in these hands.
All degrees of variation exist, and no two hands are identical. The thumb in this condition is invariably smaller with severe hypoplasia or aplasia of the phalangeal components. Occasionally, a metacarpal and distal phalanx are present with a flail thumb at the MP joint level. With an intact third metacarpal, a functional adductor pollicis muscle is often present. Most of these thumbs have very weak adduction power. Usually, the median innervated thenar intrinsic muscles are intact and range from small to normal in size. The thumb CMC joint is well segmented and mobile, and the IP joint of the thumb may exhibit decreased passive and active motion due to weak extrinsic flexor and extensors. Upon exploration, the FPL tendon often courses to a hypoplastic or absent muscle belly in the distal forearm. In the severely hypoplastic thumb, there is marked limitation of MP and CMC motion, an absent IP flexion crease, and only a rudimentary FPL tendon. The anomalies seen with the extrinsic flexors and extensors are similar to those described for the types II and IIIA hypoplastic thumbs. The fifth ray is usually the best in the hand with intact intrinsic and extrinsic musculotendinous units. Frequently, this digit has a radial clinodactyly and a completely unstable MP joint, and the entire hand is hypoplastic. Radius and ulna are present and of equal length but may be small in comparison to the opposite limb.
Amniotic band sequence (constriction ring syndrome, Streeter’s dysplasia) is a condition that can affect one or all limbs and less commonly the face. As defined by Patterson,54 limb involvement can result in any of the following deformities: (1) simple constriction rings, which may be partial or circumferential; (2) constriction rings with distal deformity, with or without concomitant lymphedema; (3) acrosyndactyly (distal fusion, fenestrated syndactyly); or (5) amputation(s) (Fig. 27.11).
Fig. 27.11 Constriction ring syndrome thumbs. (A) The thumb in these hands may present with a shallow or deep constriction ring or an amputation at any level along the skeletal ray. The phalanges at the level of loss are characteristically narrow and taper to the distal stump. (B) The intrinsic muscles are all present up to the level of the amputation. The proximal anatomy in this condition is normal. (C) The thumb is absent on the left and shows increasing length in these molds. No two hands are identical. There is great variation in the depth and location of constriction rings along the digits.
Hypoplasia of the thumb is seen in this condition when there is a deficiency in the length of the thumb, which may have a transverse failure of formation at any level. Occasionally, the existing skeletal and soft tissue components of the first ray may be hypoplastic. The hallmark of the amniotic band sequence is that the anatomy proximal to the level of amputation or level of congenital amputation is normal. Either superficial or deep constriction rings around the thumb can be associated with hypoplasia or lymphedema of the distal segment of the digit with hypoplastic nail remnants and slender, truncated phalanges present. Acrosyndactyly is usually seen to involve the central three rays of the hand but can also involve the thumb and fifth finger. Amputation of the thumb in this condition is the major cause of partial aplasia of the thumb and can occur at any position along its length. The most practical way to analyze the amputation is to place it at one of three levels: (1) distal to IP joint; (2) proximal phalanx, and (3) metacarpal (Fig. 27.11). Motion of the IP joint is usually severely affected – even with amputations or deep constriction rings distal to it.
In this type of hypoplasia, the thumb is smaller in width and longer in length and has the characteristics of a finger. As the radial border digit, it lies in the same plane as the ulnar four digits and is nonopposable. It is usually the same length as the adjacent index finger. The digit is slender and may be joined to the index finger in an incomplete simple syndactyly. A severe deficiency or nonexistent first web is often present, and some type of transverse metacarpal ligament is also present. The skeletal anatomy is similar to that of the index ray: a metacarpal with a distal growth center and three phalanges with proximal growth centers. The scaphoid is usually absent or hypoplastic. The thenar musculature (AbPB, FPB, OP muscles) are also absent as is the adductor pollicis (AddP). Instead, the usual digital intrinsics are present – namely, a lumbrical, palmar, and dorsal interosseous (Fig. 27.12). The extrinsic flexors and extensors mimic those of the normal fingers. Because the radial digit lies in the same plane as the other fingers in the hand, manipulation of objects is usually performed by utilizing lateral scissoring between the first two digits – or between the second and third if a first web syndactyly is present. Left untreated, those patients without a first web syndactyly tend to attenuate the transverse metacarpal ligament and “autopollicize” into an abducted and slightly pronated posture.
Fig. 27.12 Five fingered hand. (A) In the five fingered hand, the normal complement of median innervated thenar intrinsic muscles are absent. First dorsal interosseous, volar interosseous and lumbrical muscles are present in this ray, which anatomically is a finger, not a thumb. (B) The clinical appearance (preoperative) on the left shows that the patient has tried to flex and autopronate this ray to become a thumb.
Despite the level of arborization, each partner thumb is hypoplastic to varying degrees, with the radial duplicate usually being the most severely affected. The complexity of the deformity and, therefore, the surgical correction increases as the level of the duplication progresses proximally. Associated triphalangia of the ulnar partner further complicates any surgical reconstruction. Specific abnormalities in each thumb are seen in the nail plate, the osteoarticular column, and both the intrinsic and extrinsic musculotendinous units. The nail plate of each duplicate is always more narrow than that of the unaffected thumb, and the entire skeletal ray is hypoplastic in polydactylies proximal to the MP joint.
Musculotendinous abnormalities are common with the extrinsic extensor almost universally shared. Indeed, nearly half of the patients presented in papers on pollex abductus involve duplicate thumbs.40,43 Deviation of the partners toward each other indicates abnormal insertions of the extrinsic tendons into the distal phalanges, and connections between the extrinsic flexors and extensors are not unusual. These tendinous interconnections will limit function and cause digital angulations. The first web is usually unaffected in polydactylies involving the distal phalanx, but as the level of arborization lies more proximally, the first web space becomes increasingly deficient and tight.
Deficiencies of the osteoarticular column of the thumb may result in a short, hypoplastic thumb (Fig. 27.13). Bony abnormalities can occur as isolated bone (brachymetacarpia, brachyphalangia), all bones in combination, or as part of a generalized syndrome, such as the acrocephalosyndactyly (e.g., Apert, Pfeiffer, Carpenter, etc.) syndromes or the Rubinstein–Tabyi syndrome. Joint function is usually impaired on either side of the abnormal bone(s). In patients with anomalies of a single bone, brachymetacarpia or brachyphalangia, the remaining components of the thumb tend to be unaffected, and in patients with generalized syndromes, other abnormalities of the thumb components are common. In the acrocephalosyndactyly (ACS) syndromes, delta phalanges are common. They usually involve the proximal phalanx with a longitudinal epiphyseal bracket on the radial side. This abnormal growth plate checks growth on the radial side and results in a radial clinodactyly of the thumb, which becomes more severe over time. The metacarpal is usually short and the distal phalanx is short and broad. Incidentally, many feel that the abnormal proximal phalanx and broad distal phalanx are variations of a polydactyly. Musculotendinous anomalies are associated with poor joint function but are not as common as those with type IIIA thumbs. Deficiencies of the first web are most common, occurring along a spectrum of mild adduction contracture to complex syndactyly involving the first two rays.
Fig. 27.13 Type X-short skeletal ray. (A) A short thumb with or without radial clinodactyly is seen in many syndromes. The primary osseous abnormalities are usually seen at the proximal phalangeal joint level. The median and ulnar innervated intrinsic muscles are all present and very hypertrophied. Extrinsic and intrinsic flexors and extensors are normal up to the phalangeal level. (B) The left thumbs of children with four different syndromes all look similar. I: Rubinstein-Tabyii; II: Pfeiffer; III: Greig cephalopolysyndactyly, and IV: Apert acrocephalosyndactyly.
The whole spectrum of patients with metabolic bone diseases, skeletal dysplasias, benign skeletal tumors and many syndromes may include thumb hypoplasia. In general, very little surgical correction is required for these youngsters. The need for surgical improvement is determined by very critical observation of these children at play.
The child with thumb hypoplasia may present many unique problems with both pinch (precision, pulp, key) and grasp (precision, span, power), despite his/her ability to adapt remarkably to the functional deficiency.23 The ideal prerequisites for reconstruction of a functional thumb include55:
As researchers and clinicians struggle with the possibilities of fetal surgery, many surgeons wonder if they should wait rather than performing reconstructive procedures of the congenitally different hand as soon as possible (Fig. 27.14). Early reconstruction of the hypoplastic or absent thumb is certainly attractive in an effort to allow the infant to adapt more rapidly with optimal cortical representation. This ideal needs to be tempered with the knowledge that a congenital hand difference is, in itself, not a life-threatening condition (but may be associated with one), and the surgeon can use time to allow the affected part to grow, to observe development, and to assess the functional needs. The construction of the thumb with a stable osteoarticular column of adequate length, mobile joints, growth potential, scar-free first web, and gliding muscle tendon units is not easily accomplished in very small hands – despite our refined microvascular instruments and skills.
Fig. 27.14 Timing. Plaster molds made of patients with type V hypoplasia made at ages (left to right): 32 weeks’ gestation, 12 months and 8 years of age demonstrate the tremendous growth difference. Despite their discrepant sizes, the anatomy of these hands was remarkably similar with normal index active and passive range of motion. Any surgery on the hand on the left would be quite challenging.
However, the arguments that are forwarded by the proponents of the early surgery persist. Among the most powerful points include anatomic, cognitive, and psychological factors. Anatomically, the release of tethered musculotendinous units and joint contractures will allow unrestricted growth, and physiological adaptation of the reconstructed thumb will occur secondary to growth and functional use.55 On a cognitive level, early surgery will allow the development of the child with a reconstructed thumb to occur prior to thumb corticalization, which takes place at around 18 months of age. Psychologically, correction will alleviate anxiety in the parents and, therefore, in the child.
These purported advantages should be weighed against risks which include: (1) growth-related complications; (2) functional need assessment, and (3) patient cooperation. In slightly older patients, the affected thumb is larger so potential problems with osteotomies, alteration of growth, skeletal fixation, joint reconstruction and potential for compromise of blood supply are reduced. Also with an older patient, the surgeon is better able to accurately assess the functional needs of the child according to his or her interests, current adaptations, and lifestyle. Finally, and perhaps most importantly, an older child is potentially a more cooperative patient.
In the absence of other organ system complications, we try to reconstruct these problems when the child is between 10 and 18 months of age. Pollicization at 1 year is often preceded by centralization of the hand and wrist between 5 and 8 months of age in those with radial deficiency. The timing for correction of type IIIB deformities may be problematic. Though pollicization is the procedure of choice, some parents and families simply will not allow it. We agree with other surgeons that the alternatives involve difficult reconstructions, often including one or more stages, and are wisely deferred until the child is aged 4–5 years, a time when the hand is larger and the patient may be more cooperative with the postoperative therapy regimen.5,23,31
Surgical correction of the hypoplastic or absent thumb must be individualized. As these children may have other congenital anomalies, an early assessment of the upper limb deficiencies and a coordinated management plan can be formulated and instituted. Perhaps the most important and least emphasized variables are the confidence, surgical skill and experience of the surgeon and his/her team.
This section on treatment is divided into two parts: in the first part, treatment considerations will be outlined for each type of thumb hypoplasia, and in the second part, surgical techniques will be outlined in detail for each particular clinical problem.
These children are not usually functionally impaired (Fig. 27.2). In fact, many type I thumb hypoplasia patients, along with their parents, do not recognize anything abnormal about these hands. These thumbs are commonly found in patients who have a more severe radial dysplasia in the opposite upper limb. However, in this stronger limb, they have very little or no difficulty with key pinch, pulp to pulp pinch, opposition and grasping activities. Since functional problems are rare, surgical correction is not often needed. Occasionally, a child with a type I hypoplastic thumb will require a release of a mildly contracted web (see Type II management). All web releases involve more than simple skin incisions. Careful56 attention must be directed to tight fascial bands within the web space, anomalous tendon and muscle anatomy and joint ankylosis. Of all the methods available, the 4-flap Z-plasty provides the best contour and appearance (Fig. 27.15). Dorsal transposition flaps from the index finger34 and rotation flaps56,57 are effective but require skin grafting on the visible dorsal surface of the hand. Of course, any method must be carefully individualized to the patient.
Fig. 27.15 1st web space release. (A) The skin markings have been made for a four-flap Z-plasty, which include two 90° incisions perpendicular to the tight web between the thumb and index finger. Each is then bisected at a 45° angle. (B) After the four separate flaps have been mobilized, reflected dense septal bands may be identified between the skin and muscle fascia, and larger fascial bands between the intrinsic muscle groups. (C) Incision and excision of these bands may require dissection to the CMC joint level. (D) Trimming and minor flap adjustments are always needed with the proper inset of the more mobile dorsal flaps with the more rigid palmar flaps. A skin redundancy on the radial side of the index finger has been eliminated with a straight extension. (E) The preoperative appearance is seen with a dorsal view. (F) The postoperative contour is shown from the palmar surface. This technique provides the best contour of all available methods of first web release.
Five specific problems in the type II thumbs must be addressed individually: (1) narrowed first web space; (2) instability of the MP joint; (3) poor palmar abduction (opposition) for pinching and grasping; (4) lack of IP joint flexion, and (5) abduction posturing of the thumb (“pollex abductus”) (Figs 27.3, 27.4). Usually, all that is needed to correct these thumbs is a release of the first web space and stabilization of the MP joint, with or without a transfer for palmar abduction or opposition. When the surgeon encounters a pollex abductus deformity, she/he should next look for abnormalities of the flexor pollicis longus (FPL) muscle. A more detailed description of treatment options is presented later in this chapter.
Most hand surgeons agree that this variation should be reconstructed surgically (Fig. 27.5). The five individual problems are the same as listed in type II, and the options and preferred solutions are listed below. Most authors opt to complete all necessary procedures including widening of the first web space, stabilization of the MP joint, and some type of opposition transfer at one time. The major variable becomes the status of the flexor mechanism, which may require a staged approach. After 35 years of experience, our preference has been to replace the very anomalous flexor mechanism with a tendon transfer in the presence of at least one good pulley at the level of the metacarpal head. The treatment of the more deficient type IIIB and IIIC varieties constitutes one of the more interesting ongoing controversies in hand surgery.
For most hand surgeons in Europe, North America and South America, pollicization is the treatment of choice because a well-performed pollicization provides a much better and more predictable outcome than any alternative types of staged reconstruction (Fig. 27.6).
However, cultural and parental beliefs may demand one of two alternatives – staged reconstructions with58–61 and without62 a microvascular joint transfer, which have both become popular in the Asian countries. Osteoplastic thumb reconstruction has a long history.6,63–65 The osteoarticular column is connected with an intercalated bone graft between the index and hypoplastic thumb metacarpal (Fig. 27.16). Multiple stages are then needed to first stabilize MP and IP joints and construct pulleys. At that point, tendon transfers are performed for opposition as well as IP flexion and extension. The major disadvantages of this procedure include the lack of CMC mobility, lack of growth, poor motion and the multiple stages required. Insensate abdominal pedicle flaps have been used to provide tissue for an adequate first web space.
Fig. 27.16 Spectrum of metacarpal hypoplasia. (A-D) There is no arbitrary distinction between specific categories of thumb hypoplasia based on the skeletal appearance alone. These thumbs, which show varying degrees of hypoplasia with a presumably intact CMC joint, would be classified as type IIIA. (E-H) The smaller metacarpals in these examples would signify type IIIB thumbs. (I-L) These thumbs, with no skeletal connection, would be classified as “floating thumbs,” type IV. When a syndactyly exists between the thumb and index digit, an associated congenital heart defect (the Holt–Oram syndrome) may be present.
Another alternative is to transfer either the second62,66–69 or third70 or first metatarsophalangeal joint in a hyperextended position to create a new CMC joint and proximal metacarpal. This composite joint must be harvested with a large dorsalis pedis pedicle, which provides venous drainage and adds bulk to the deficient thenar region. Tendon transfers are then performed to provide motion at either the MP or IP joints.