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REVIEW ARTICLE
Year : 2011  |  Volume : 44  |  Issue : 2  |  Page : 253-265
 

Surgical reconstruction of congenital thumb hypoplasia


Senior Hand Surgery Consultant, Royal Northshore Hospital, Reserve Road, St. Leonards, NSW 2065, Sydney, Australia

Date of Web Publication24-Sep-2011

Correspondence Address:
Michael Tonkin
Senior Hand Surgery Consultant, Royal North Shore Hospital, Reserve Road, St. Leonards, NSW 2065, Sydney
Australia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-0358.85347

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 » Abstract 

This review article introduces a new classification of congenital hand anomalies. It then considers the classification of congenital thumb hypoplasia and describes the the authors indications for surgery. Specifically, attention is directed towards surgical techniques and problems encountered in the reconstruction of grade 2 hypoplastic thumbs and in pollicisation of the index finger for grades 3, 4 and 5 thumb hypoplasia.


Keywords: Congenital thumb hypoplasia; Surgical reconstruction


How to cite this article:
Tonkin M. Surgical reconstruction of congenital thumb hypoplasia. Indian J Plast Surg 2011;44:253-65

How to cite this URL:
Tonkin M. Surgical reconstruction of congenital thumb hypoplasia. Indian J Plast Surg [serial online] 2011 [cited 2019 Jun 17];44:253-65. Available from: http://www.ijps.org/text.asp?2011/44/2/253/85347



 » Introduction Top


Surgeons working in the field of congenital hand surgery are attracted to the concept of thumb reconstruction as the rewards of obtaining improved function and appearance of an underdeveloped thumb are so significant. Classical thumb hypoplasia is the specific entity to which most surgeons working in the field of congenital hand surgery refer when considering the underdeveloped thumb. However, thumb underdevelopment (hypoplasia) accompanies many congenital conditions, including thumb duplication, transverse deficiencies and symbrachydactyly, brachydactyly, cleft hand complex and ulnar longitudinal deficiency, congenital constriction ring syndrome, and other miscellaneous conditions such as the thumb of an Apert syndrome or Rubinstein-Taybi syndrome. Each condition represents its own specific challenges, but the principles remain the same. An optimal thumb demands appropriate size and shape, stability, and mobility. No matter what the cause, surgery is directed toward the addition or removal of tissue, correction of deformity, stabilization of unstable joints, and the creation of joint mobility. At times, there is a conflict between stability and mobility.

Although generalizations are not necessarily applicable to all individual cases, the achievement of optimal mobility at the carpometacarpal (CMC) joint is perhaps the major determinant of effective thumb mobility, with less importance placed on the metacarpophalangeal (MCP) and interphalangeal (IP) joints. In principle, mobility may be sacrificed for stability at these levels. Since the 1960s, the Swanson/ International Federation of Societies for Surgery of the Hand (IFSSH) classification of congenital hand anomalies has been adopted by most surgeons for classification of these conditions. [1] However, its descriptive basis is unable to cater for our increasing knowledge of the causation of congenital anomalies at a molecular level. [2]

A recently proposed classification of congenital hand anomalies allows the surgeon to consider whether the cause of any particular anomaly is secondary to a malformation, a deformation, or a dysplasia [Table 1]. [2] A malformation is an abnormal formation of tissue resulting from abnormal cell formation. Deformation differs from a malformation as the insult is to cells which have already formed normally. It is a deformation of normal tissue. A dysplasia is a lack of normal organization of cells into tissue. A subclassification of malformations allows one to define the axis of development and differentiation which is involved in any particular condition and which part of the limb is predominantly affected, giving a better indication of timing and site of insult in the developing limb bud.
Table 1: Modified classification of congenital anomalies of the hand and upper limb

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Most causes of thumb underdevelopment are a malformation except that secondary to constriction ring syndrome in which formed tissue is deformed. Classical thumb hypoplasia is a malformation involving abnormal development and differentiation in the longitudinal radial axis. It is often associated with hypoplasia or absence of the radius. Proximal arm and shoulder involvement may be present.

The following review details my approach to the management of classical thumb hypoplasia. Many of the principles may be applied to other causes of thumb underdevelopment.


 » Classification Top


The Blauth classification of grades of thumb hypoplasia (1 to 5) [3],[4] [Figure 1] has undergone a number of modifications. That of Manske is most commonly quoted in the literature, but does involve significant changes to the concepts outlined by Blauth. [5] Blauth viewed the hypoplastic thumb according to grades of severity, with increasing bone and joint hypoplasia accompanied by increasing soft-tissue hypoplasia. He distinguished grade 2 from grade 3 according to the presence or absence of a CMC joint, retaining the thumb in the former case but advising reconstruction of an alternative CMC joint in the latter. Manske moved this distinction into a subclassification of grade 3, in which grade 3A has a CMC joint and grade 3B does not. Buck-Gramcko added grade 3C in which only the distal one-third of the metacarpal remained. The Manske classification distinguishes between grades 2 and 3A by the absence or presence of extrinsic anomalies. Perhaps the Blauth classification would have been better served if such a distinction was created within grade 2, leaving intact the integrity of Blauth's skeletal description. Even so, such a subclassification suggests that extrinsic anomalies develop with more severe grades of hypoplasia but are not present in less severe grades (grades 1 and 2).
Figure 1: Grades of thumb hypoplasia 1-5 according to Blauth

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I favor Blauth's concept of increasing hypoplasia of all thumb elements occurring concurrently, both soft tissues and bone, maintaining the distinction between grades 2 and 3 according to the presence or absence of the proximal metacarpal [Figure 2] and [Figure 3]. The surgeon must assess all components of the grade 2 thumb and decide which anomalies would benefit from reconstruction. In my experience, if surgical reconstruction of thumb intrinsics, MCP joint instability and first web hypoplasia are indicated, there is always some component of extrinsic anomaly. However, this anomaly may or may not deserve reconstruction. Subgroups of Blauth's five grades may be considered according to the structures that are to be reconstructed and the techniques involved, e.g., whether MCP joint instability can be attended to via a soft-tissue reconstruction or requires a fusion. Such subgroups can also cater for extrinsic reconstructions, be they to the flexor or extensor or both, intrinsic muscle reconstructions, types of first web-plasty, etc. This preference or otherwise for such subclassifications will depend upon whether one is a "splitter" or a "lumper." For me, the most pertinent question relates to the adequacy of the CMC joint. Blauth's grade 3 has no proximal metacarpal and the inadequacy of the joint is defined. His grade 2 has a proximal metacarpal. The classification does not comment on whether its CMC joint is adequate: whether it would benefit from stabilization or, in the occasional extreme circumstance when no surgical reconstruction will render it adequate, whether the creation of a new CMC joint by alternative methods such as pollicisation or joint transfer should be considered [Figure 4].
Figure 2: Blauth grade 2 thumb hypoplasia

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Figure 3: Blauth grade 3 thumb hypoplasia

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Figure 4: Blauth grade 2 thumb hypoplasia with an inadequate CMC joint

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Regardless of the classification one prefers, the onus is on the surgeon to assess each individual component of thumb hypoplasia and determine which reconstructions will provide optimal thumb function and appearance.


 » Surgery Top


Indications

Grade 1


The thumb is small, there is some hypoplasia of the thenar musculature, and there may be mild extrinsic anomalies. However, the joints are stable and mobile. No surgery is indicated.

Grade 2

The CMC joint is intact although it may display a degree of instability and/or lack full mobility. Thumb hypoplasia is more severe, requiring reconstruction for optimal function. The MCP joint is unstable, the thenar musculature is hypoplastic, and there is underdevelopment of the first web. Extrinsic anomalies are usually present if the degree of thenar musculature hypoplasia demands reconstruction. These anomalies include abnormal origins and insertions of flexor pollicis longus (FPL), extensor pollicis longus (EPL), extensor pollicis brevis (EPB), and abductor pollicis longus (APL). The pollex abductus anomaly describes a connection between the extensor mechanism and the extrinsic flexor, often at the MCP joint, but connections may be present proximal and distal to this level. [6] Insertions of the long flexor and extensor may be eccentrically placed into the terminal phalanx. Proximal excursion is often limited. Although all intrinsic muscles are involved, it is wasting of the abductor pollicis brevis (APB) and opponens muscles which are more obvious clinically. Ulnar collateral ligament instability of the MCP joint may predominate. However, the joint is hypoplastic and all stabilizing elements may be affected. Underdevelopment of the articular surfaces may be severe with consequent global instability.

Grade 3

The proximal metacarpal is absent. Hypoplasia of the phalanges and distal joints and of all soft tissues is more severe. Pollicisation is the optimal method of creating a satisfactorily functioning thumb, but such a decision is sometimes complicated by concerns about the creation of a four digit hand. More recently, alternative methods of CMC joint reconstruction, through transfer of vascularized and nonvascularized joints, have shown some encouraging results and may be indicated when the need to retain five digits is paramount.

Grade 4

The metacarpal is absent and the terminal elements of the thumb are connected to the hand via a skin bridge with neurovascular bundle(s). The optimal reconstruction is pollicisation but some have extended the indications for reconstruction of the grade 3 thumb to these floating thumbs. The functional results are poor but five digits are retained.

Grade 5

The thumb is absent. Pollicisation is the optimal procedure. Some have transferred vascularized toes to obtain five digits. The absence of proximal musculotendinous units and nerves and the lack of thumb representation within the cerebral cortex render the transferred toe significantly deficient.

Surgical techniques

First web insufficiency


A four-flap web-plasty is the most common technique of first web deepening [Figure 5]. Rotation and advancement of tissue from the dorsum of the hand may be indicated for more severe first web deficiency [Figure 6]. It is very uncommon to require tissue from distant sources, such as a pedicled posterior interosseous artery flap or radial forearm flap, or even a free tissue transfer. I have never required these for reconstruction of a first web in a grade 2 thumb hypoplasia.
Figure 5: (a,b,c) Four-flap first web plasty

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Figure 6: (a,b) V-Y advancement first web plasty

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Metacarpophalangeal joint instability

Assessment of the MCP joint stability in the anesthetized child may reveal more information than that obtained in preoperative assessments. In determining the optimal stabilization procedure, consideration must be given as to whether the instability is predominantly a loss of ulnar collateral ligament integrity or whether the instability is global, requiring a more sophisticated reconstruction or even a chondrodesis or fusion of the joint. There are two main methods of reconstruction of the ulnar collateral ligament. One is to use available local tissue, imbricating capsule, and ligamentous structures, such as they are, on the ulnar side of the joint. The other is to introduce tissue which is extrinsic to the joint, to cater for the deficiencies of the local structures. The terminal part of a flexor digitorum superficialis (FDS) used for an opposition transfer is a popular source.

Whichever reconstruction of the ulnar collateral ligament is performed, it will fail if there is an abnormal abduction force crossing the MCP joint on its radial side, most commonly in association with a pollex abductus anomaly. Attention must be directed to this if the joint forces are to be balanced and the ulnar collateral ligament reconstruction protected.

My preference is to assess the caliber of the MCP joint ulnar soft tissues at the time of surgery [Figure 7]. If they are satisfactory, I proceed to a double-breasting of these structures and protect the joint with a fine k-wire. A strip of palmar plate can supplement this reconstruction. A 2-3 mm width may be mobilized, maintaining its insertion at the proximal phalanx base, transferring its proximal origin dorsally to the metacarpal head-neck junction. A similar technique may be applied for radial collateral ligament instability. The abductor digiti minimi (ADM) is used as an opposition transfer as described below. If the soft tissues are inadequate, then I will proceed to an FDS opposition transfer. One slip of the terminal part of the FDS is passed through a drill hole at the head-neck junction of the metacarpal, from radial to ulnar side, and is sutured to the base of the proximal phalanx and to soft tissues attached to this [Figure 8].
Figure 7: Assessment of ulnar collateral ligament, capsular structures and bone development of MCP joint

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Figure 8: Use of an FDS slip to create an MCP joint ulnar collateral ligament

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Sometimes the lack of development of the articular surfaces of the MCP joint compromises satisfactory soft-tissue reconstruction. There is global instability. The "elephant trunk" sign is indicative [Figure 9]. The condyles of the head of the metacarpal are severely underdeveloped on the palmar aspects, with the shape of the metacarpal head, viewed end-on, triangular in appearance. The base of the proximal phalanx is of small diameter and is planar with no concavity. A formal arthrodesis can be performed but this does shorten the thumb and is only possible if there is epiphyseal ossification. A chondrodesis, fixing the cartilaginous surfaces with one or two fine wires, will stabilize the joint, at least temporarily.

Another alternative for global instability is to use both slips of FDS to reconstruct ulnar and collateral ligaments. For MCP joint hyperextension instability, the whole of the palmar plate is detached proximally and advanced proximally to the head-neck junction of the metacarpal. I prefer this soft-tissue reconstruction to chondrodesis or fusion, unless the underdevelopment of articular surfaces is indeed profound.

Correction of MCP joint instability is vital to the protection of the underdeveloped CMC joint. Radial deviation at the MCP joint results in adduction of the metacarpal and basal subluxation at the CMC joint, a zig-zag deformity. If an MCP joint fusion or chondrodesis is necessary, regrettably this increases the length of the lever arm and places stress across the proximal joint. The result will be less than satisfactory and, in this instance, one must consider the necessity of a soft-tissue stabilization at the CMC joint level, a relatively difficult reconstruction, particularly if joint surfaces are hypoplastic. In circumstances of severe proximal hypoplasia, in spite of the presence of a CMC joint, alternative methods of CMC joint reconstruction, such as pollicisation, may be considered.

Opposition transfers

The main alternatives are an ADM (Huber) transfer and an FDS transfer. There are proponents of both, but there is no clear indication of the superiority of one over the other. The use of the ADM diminishes the power of abduction of the little finger but provides some thenar bulk. It is a better pronator of the thumb ray. The FDS transfer removes a flexor from the usually more mobile ulnar digits (ring finger), perhaps decreasing grip strength, and fails to provide any bulk to the thenar eminence. The FDS is superior in providing palmar abduction but pronates less effectively. When additional tissue is needed to stabilize the MCP joint, the FDS can provide this as described above.
Figure 9: (a,b) The "elephant trunk" sign of global MCP joint instability

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ADM transfer

The incisions are shown in [Figure 10] and [Figure 11]. The ulnar incision at the junction of glabrous and dorsal skin provides a very pleasing cosmetic result [Figure 12]. Proximally, the incision should curve around the wrist crease at the level of the pisiform so that the origin of the ADM may be mobilized, if necessary, for length. Distally, the insertion of the abductor should be incised from the base of the proximal phalanx, but the tendon contribution to the extensor mechanism dorsally should also be harvested to provide adequate length [Figure 13]. I do not transfer the origin of the ADM to the flexor retinaculum as suggested by some for fear of interference with the neurovascular pedicle, although its origin may be mobilized fairly aggressively, maintaining some attachment to both the flexor carpi ulnaris (FCU) and the pisiform proximally. Tunneling of the muscle is a little more difficult with the ulnar incision than with a parahypothenar incision. It is necessary to make certain that no retinacular fibers of the aponeurosis impede its passage and that the neurovascular bundle is not kinked during its transfer. Insertion at the thumb is into the APB remnant if it is present. Otherwise, it is better to attach the transfer to the head-neck junction of the metacarpal rather than to the proximal phalanx, as the latter insertion tends to create a radial deviating force which may challenge the ulnar collateral ligament reconstruction.
Figure 10: Parahypothenar incision for ADM transfer

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Figure 11: Medial incision for ADM transfer

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Figure 12: (a,b) Scar from parahypothenar and medial incisions following ADM transfer

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Figure 13: Dissection for ADM transfer

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FDS transfer

Incisions are shown in [Figure 14]. The FDS transfer is sutured to the periosteum at the head-neck junction with one slip passed through the metacarpal to be used for ulnar collateral ligament reconstruction [Figure 8]. The FDS transfer demands reconstruction of a pulley to allow an optimal direction of pull so that pronation of the thumb ray is possible. This is usually achieved with a distally based slip of FCU [Figure 15]. It is possible to also prolong a radial slip to assist in reconstruction of the radial collateral ligament for global instability, often in association with a proximal advancement of the palmar plate, as described previously. This aggressive soft-tissue reconstruction at the MCP joint reduces the necessity to consider a primary MCP joint chondrodesis or a fusion, or at least allows delay of such a procedure until a later stage if failure of the soft-tissue reconstruction demands a more permanent solution.
Figure 14: Incisions for FDS transfer

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Figure 15: (a,b,c,d) FDS opposition transfer through an FCU pulley

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Extrinsic tendon reconstruction

Failure to correct a pollex abductus anomaly will lead to a recurrence of MCP joint ulnar collateral ligament instability, metacarpal adduction, and possible CMC joint instability. FPL anomalies are common. Traction on the FPL at the level of the MCP joint will alert the surgeon to eccentric distal insertions and abnormal origins. In the former, deviation of the IP joint or lack of full flexion is evident. In the latter, there is minimal excursion of the musculotendinous unit with proximal traction. Any connection between the flexor and extensor mechanism must be divided [Figure 16]. In these instances, the pulley system is often incompetent. This may be reconstructed with a strip of extensor retinaculum or a strip of local tendon [Figure 17]. If there is minimal passive IP joint motion, I do not proceed to sophisticated extrinsic flexor reconstruction. A superficialis transfer to a well-formed FPL tendon without an adequate proximal muscle belly is a possibility when there is a satisfactory passive range of motion. A staged flexor tendon reconstruction with preliminary insertion of a silastic rod, pulley reconstruction, and subsequent superficialis transfer is rarely indicated but may be considered in certain circumstances. Eccentric extensor and flexor insertions should be centralized. An extensor indicis proprius (EIP) transfer may replace EPL function, but is rarely required.
Figure 16: Pollex abduction connection between extrinsic extensors and flexor

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Figure 17: (a,b) Realignment of flexor pollicis longus and pulley reconstruction

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Pollicisation

I believe that pollicisation provides optimal thumb function and a very satisfactory appearance when the CMC joint is absent in grades 3, 4, and 5 hypoplasia. Such a procedure may also be considered, uncommonly, in cases of grade 2 hypoplasia in which, in spite of the presence of a proximal metacarpal, the global hypoplasia is so severe that reconstruction would provide an inferior thumb to that achieved by pollicisation. The necessity to retain five digits for social, racial, or religious reasons must not be underestimated. In these instances, the alternative reconstructions outlined below are considered.

The technique of Buck-Gramcko is that followed by most surgeons. [7] A number of modifications have been offered with alterations in placement of incisions and specific techniques of CMC joint and tendon reconstruction. However, the younger surgeon will find a reliable friend if he/she adheres to Buck-Gramcko's method.

Incisions

The concept of the incisions forming a modified z-plasty may be helpful [Figure 18]. The first limb begins dorsally and distally at the index-middle web and extends proximally and obliquely to the radial border of the hand proximal to the index finger MCP joint. The second limb extends from the proximal point of the first limb onto the palmar aspect of the proximal phalanx to meet the origin of the first limb in the index-middle web space. The third limb extends proximally from the palmar limb, in the line of the index-middle intermetacarpal space. These flaps are transposed when the index finger is rotated and transported proximally. A number of subtleties of modification cater for specific demands. The palmar incision in the digit should be extended to just proximal to the proximal interphalangeal (PIP) joint when the index finger is well-developed and mobile [Figure 18]. A longer thumb is preferable if there is significant index finger stiffness as greater length compensates for lack of mobility. In this instance, the palmar incision is moved proximally toward the basal finger crease. A longitudinal incision extended distally from the dorsal limb incision to the PIP joint allows access to the extensor mechanism and its lateral bands for construction of thumb intrinsic mechanisms and the extrinsics, EPL and APL [Figure 19]. The third palmar limb may be moved radially to incorporate excision of a grade 3 or grade 4 thumb [Figure 20]. Alternatively, the excision of such may be incorporated into the second, more radial limb [Figure 19] and [Figure 21].
Figure 18: (a,b,c) Z concept of pollicisation skin incision

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Figure 19: Dorsal incision for intrinsic reconstruction

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Figure 20: Incorporation of Grade 3 thumb to be excised into third limb of pollicision incisions

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Figure 21: Incorporation of Grade 3 thumb to be excised into second limb of pollicisation incisions

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Technique

Thin dorsal flaps are elevated until the dorsal venous architecture is identified so that one or two veins, along with superficial dorsal nerves, can be mobilized separately from the flaps and the underlying digit. This prevents kinking of vessels, compromising venous return, when the digit is recessed proximally.

Through the palmar incision, the neurovascular bundle of the index-middle web is identified. A radial neurovascular bundle is usually present. However, the radial digital artery to the index finger may be very small, perhaps even absent, in grade 5 hypoplasia which is accompanied by index finger hypoplasia. The neurovascular bundles on either side of the digit are mobilized using microsurgical instruments and magnification. Inspection of the second common digital artery will determine the level of bifurcation into digital arteries to the adjacent sides of the index and middle fingers. The radial digital artery to the middle finger is tied off [Figure 22]. The neurovascular pedicle is dissected proximally. A neural ring is relatively common but can be usually attended to by intraneural dissection of the common digital nerve. An awareness of the possibility of arterial compromise with proximal recession of the digit, either due to a neural ring or fascial structures, should prevent this complication.
Figure 22: The radial digital artery to the middle finger is tied off

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A1 and A2 pulleys are divided [Figure 23]. The A3, A4, and A5 pulleys become the thumb A1, oblique and A2 pulleys. Some routinely shorten the flexor digitorum profundus (FDP), but I have not found this necessary unless pollicisation is performed at greater than five years of age. A z-shortening can be performed proximal to the wrist to avoid increasing the possibility of adhesions within the dissected area of the palm.
Figure 23: Release of A1 and A2 pulleys

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The extensor mechanism is inspected to assess the presence or absence of EIP and the quality of extensor digitorum communis (EDC) [Figure 24]. If both are present, these are divided at the MCP joint. Distally, the extensor mechanism is mobilized to the PIP joint, separating the lateral band contributions to this level, but maintaining continuity with the first dorsal interosseous and the first palmar interosseous muscles on radial and ulnar sides, respectively. Proximal mobilization of these muscles must respect their neural innervation. Release of their attachments at the base of the proximal phalanx must respect the integrity of the capsule and ligaments of what will become the new CMC joint. Although some recommend the ablation of the blood supply to the physis of the metacarpal, others prefer not to interfere with any contribution which may maintain the integrity of the physis of the proximal phalanx. Premature physeal closure and a short first metacarpal in the reconstructed thumb are a consequence of growth plate compromise of the index finger proximal phalanx.

Retractors can be placed around the head-neck junction of the metacarpal, protecting all other structures, particularly the palmar neurovascular bundles, while an osteotomy is performed at the head-neck junction of the metacarpal. In the young child, a Beaver blade or small osteotome is most satisfactory for the purpose. Some bone nibblers can be used to flower the perimeter of the head of the metacarpal by simply breaking bone fragments, which remain attached to the periosteum. The physis is removed using a fine curette and Beaver blade so that the new trapezium will not grow longitudinally. If ossification has occurred in the head of the metacarpal, it is easy to establish that the growth plate has been adequately removed. Care needs to be taken when ossification has not occurred, so that the articular surface of the metacarpal head is not breached.
Figure 24: Intrinsic and extrinsic tendons outlined prior to reconstruction

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The diaphysis of the metacarpal is then dissected in a submuscular, extra-periosteal manner. An osteotomy is performed at the base of the metacarpal, retaining some base. The angle of this osteotomy is vital to the reconstruction of the new CMC joint. Ideally, the new trapezium (head of the metacarpal) should be placed anterior (palmar) to the plane of the second metacarpal base so that the new thumb is on an anterior plane to the remaining three digits. It needs to be angled into both palmar and radial abduction and rotated into pronation. Regrettably, it is not possible to satisfy all of these principles of positioning and maintain contact between the cut surface of the second metacarpal base and the raw surface of the metacarpal head when the metacarpal head has been flexed through 90°. This is done to prevent an hyperextension deformity at the new CMC joint. Buck-Gramcko initially described removal of the whole of the second metacarpal base with suture of the new trapezium to the floor of the index finger CMC joint at its anterior border. He subsequently preferred retention of the metacarpal base, presumably to maintain optimal length of the transposed thumb and to obtain a bony union between the base of the metacarpal and the metacarpal head, preventing instability. An oblique osteotomy leaving the bone longer radially allows a satisfactory compromise in positioning the thumb optimally and maintaining some bone to bone contact [Figure 25]. My preference is to place a fine k-wire antegrade through the flexed metacarpal head and phalanges of the index finger and to then drive this retrograde into the carpus with the thumb in the desired position, removing the wire at five weeks [Figure 26]. Before fixing the thumb to the carpus in this manner, two gauge 2-0 Ticron sutures are placed through the base of the metacarpal and into the metacarpal head, to be tightened following wire fixation of the thumb to the carpus. The final position should aim for 120° of pronation, an anterior lie of the new trapezium in relationship to the metacarpal base (difficult); 30° of radial abduction and 40° of palmar abduction. The less mobile digit may be fixed at lesser angles of radial and palmar abduction. Passive joint motion and the quality of the extrinsic and intrinsic motors play a role in this decision.
Figure 25: Oblique osteotomy at base of index finger metacarpal

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Figure 26: K-wire placement through index finger with metacarpal head flexed

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The EIP, if present, is shortened and resutured to the central extensor mechanism to the PIP joint of the index finger in firm but less than full tension. Too tight a repair will result in retropulsion of the pollicised digit, particularly if a balance is not achieved following the reconstruction of APB. The new EPL also acts as an adductor of the thumb. EDC can help to stabilise the position of the new thumb metacarpal, particularly if its route and positioning are modified to better mimic the function of APL. If EIP is absent, EDC is used for EPL reconstruction.

Although Buck-Gramcko advises dividing the lateral bands, shortening and resuturing them to create an APB and an adductor from the first dorsal interosseous and the first palmar interosseous, respectively, I tend to concertina these tendons without dividing them and suture them together under as firm a tension as is possible. It is necessary to mobilize both lateral bands to beyond the PIP joint of the index finger, particularly that from the first dorsal interosseous, so that its ability to abduct and rotate is optimal. This also decreases a tendency of the lateral bands to hyperextend the new MCP joint of the thumb.

When thumb hypoplasia is accompanied by radial hypoplasia, there is often a camptodactyly of the index finger. My preference is to deal with any significant flexion deformity of the new thumb MCP joint at a second procedure, for fear of interfering with the viability of the pollicised digit.

The tourniquet is released to check the vascularity of the thumb. Flaps are then refashioned so that they may be sutured into position with a pleasing contour. The skin tension within the flaps will assist in maintaining the position of the thumb once the wire is removed. Some prefer not to use a wire at all, obtaining the appropriate position through tension of the intrinsic and extrinsic tendon reconstructions and the skin suture. My practice is to use a wire, aim for a bony union between the new trapezium and the index finger metacarpal base and to rely on positioning at the time of k-wire fixation to obtain optimal thumb position. The tendon reconstructions are then performed to provide balanced tension around the thumb longitudinal axis [Figure 27].
Figure 27: Position of reconstructed thumb

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Reconstruction of Grades 3 and 4 thumb hypoplasia

When pollicisation is unacceptable to parents and/or patient, reconstruction of grades 3 and 4 thumbs is possible. [8],[9],[10],[[11] A vascularized second toe metatarsophalangeal (MTP) joint may be transferred to the carpus or to the base of the shaft of the second metacarpal. The metatarsal head becomes the new trapezium and the proximal phalanx becomes the thumb metacarpal. Nonvascularized transfers are also utilized. An extrinsic extensor can be reconstructed using EIP from the index finger. A superficialis tendon can be transferred as a flexor and an opposition transfer is created in the manner described for grade 2 hypoplasia.

An alternative is to transfer the distal two-thirds of the fourth metatarsal bone (nonvascularized), reversing this and using the metatarsal head as the new joint. The shaft is fixed distally to the remnant of the metacarpal or proximal phalanx of the grade 3 or 4 thumb.

Flaps are necessary to recreate the first web in all such cases.

Multiple surgeries are often necessary to create a stable thumb with some mobility. The patient has five digits. The width of the hand is maintained, which assists grip. However, the problems are many. Scarring is significant; the "new" thumb remains small and may require lengthening; joints are often unstable, requiring fusion subsequently; and mobility is poor.

Full toe transfers have been utilized by some for grade 5 hypoplasia. However, the lack of normal proximal tissues and the lack of cortical representation, render the function of such transfers less than satisfactory.[11]

It is not my practice to apply these reconstructive procedures to young children. If pollicisation is refused, some of the above techniques may be indicated at a later age if the child is using the thumb. Carefully selected surgery may stabilize a joint or even provide a joint through an MTP transfer. An opposition tendon transfer may improve function. Such reconstructions should be limited to those who have not excluded the rudimentary thumb but use it for some activities. The results remain inferior to those obtained from a well-performed pollicisation. However, five digits are retained [Figure 28].
Figure 28: (a,b) Function of right hand pollicisation and unstable left Grade 3 thumb

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 » References Top

1.Swanson AB. A classification for congenital malformations of the hand. Acad Med Bul New Jersey 1964;10:166-9.  Back to cited text no. 1
    
2.Oberg KC, Feenstra JM, Manske PR, Tonkin MA. Developmental biology and classification of congenital anomalies of the hand and upper extremity. J Hand Surg Am 2010;35:2066-76.  Back to cited text no. 2
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3.Blauth W. Der hypoplastische Daumen. Arch Orthop Unfall Chir 1967;62:225-46.  Back to cited text no. 3
    
4.Blauth W, Schneider-Sickert F. Numerical variations. In: Congenital deformities of the hand: An atlas of their surgical treatment. Berlin: Springer-Verlag; 1981. p. 120-1.   Back to cited text no. 4
    
5.Manske PR, McCarroll HR Jr, James M. Type III-A hypoplastic thumb. J Hand Surg Am 1995;20:246-53.   Back to cited text no. 5
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6.Tupper JW. Pollex abductus due to congenital malposition of the flexor pollicis longus. J Bone Joint Surg Am 1969;51:1285-90.  Back to cited text no. 6
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7.Buck-Gramcko D. Pollicization of the index finger. Method and results in aplasia and hypoplasia of the thumb. J Bone Joint Surg Am 1971;53:1605-17.   Back to cited text no. 7
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8.Yamauchi Y, Fujimaki A, Yanagihara Y, Yoshizaki K. Reconstruction of floating thumb. Especially on the use of metatarsophalangeal join grafting. Seikeigeka (Orthop Surg) 1979;30:1645-8.  Back to cited text no. 8
    
9.Foucher G, Medina J, Navarro R. Microsurgical reconstruction of the hypoplastic thumb, type IIIB. J Reconstr Microsurg 2001;17:9-15.   Back to cited text no. 9
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10.Shibata M, Yoshizu T, Seki T, Goto M, Saito H, Tajima T. Reconstruction of a congenital hypoplastic thumb with use of a free vascularized metatarsophalangeal joint. J Bone Joint Surg Am 1998;80:1469-76.   Back to cited text no. 10
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11.Matsuzaki H, Toishi S, Yoshizu T. A Blauth IIIB hypoplastic thumb reconstructed with a vascularised metatarso-phalangeal joint transfer: A case report with 28 years of follow up. Hand Surg 2009;14:63-8.  Back to cited text no. 11
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17], [Figure 18], [Figure 19], [Figure 20], [Figure 21], [Figure 22], [Figure 23], [Figure 24], [Figure 25], [Figure 26], [Figure 27], [Figure 28]
 
 
    Tables

  [Table 1]



 

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