Abstract
Thumb hypoplasia may occur in isolation or as part of a broader spectrum of radial deficiencies. The classification of thumb hypoplasia is fairly straightforward and the treatment algorithm is well defined. In addition, the surgical outcome is predictable as long as the tenets of management are followed. In contrast, the treatment of forearm radial deficiency remains challenging, and obtaining a consistently favorable outcome is elusive, as detailed in the chapter on forearm deficiencies. This chapter will concentrate entirely on the “thumb,” with a focus on diagnosis, classification, and treatment for maximizing use of the most essential digit of the hand. As humans, we can function extremely well with a “thumb” and an adjacent “post” for prehension. Without a thumb, we are left with a primitive hand that lacks an opposable digit and therefore has diminished function.
Key Terms
Thumb hypoplasia, opposition transfer, metacarpophalangeal instability, pollicization, flexor digitorum superficialis, abductor digiti minimi
Thumb Hypoplasia
Thumb hypoplasia is considered part of radial deficiency even with normal forearm architecture. Hence, associated anomalies need to be considered during the initial evaluation. The workup must include entities such as VACTERL association, thrombocytopenia–absent radius syndrome, Holt-Oram syndrome, CHARGE ( c oloboma of the eye, h eart defects, a tresia of the choanae, r etardation of growth and/or development, g enital and/or urinary abnormalities, and e ar abnormalities and deafness) syndrome, and Fanconi anemia ( Table 37.1 and Figure 37.1 ). An evaluation of all possibly affected organ systems can be life-saving. The workup should include renal ultrasound, echocardiography, spine radiographs, a complete blood count, and a chromosomal challenge test.
| Syndrome or Association | Characteristics |
|---|---|
| Holt-Oram syndrome | Heart defects, most commonly cardiac septal defects |
| Thrombocytopenia–absent radius syndrome | Thrombocytopenia present at birth (may require transfusions) but improves over time |
| VACTERL association | Vertebral abnormalities, anal atresia, cardiac abnormalities, tracheoesophageal fistula, esophageal atresia, renal defects, radial dysplasia, lower limb abnormalities |
| Fanconi anemia | Aplastic anemia not present at birth; develops at about 6 years of age |
| CHARGE syndrome | Coloboma of the eye, heart defects, atresia of the nasal choanae, retardation of growth and/or development, genital and/or urinary abnormalities, and ear abnormalities and deafness |
Failure to ascertain the diagnosis of an associated syndrome will have lifelong ramifications for the child, family, and physician. This consequence is particularly evident in children with Fanconi anemia that can be diagnosed early with a chromosomal challenge test before the onset of bone marrow failure. Timely diagnosis allows for years of searching for an appropriate bone marrow match that may prevent the child from dying from aplastic anemia. Patients with thumb hypoplasia and other physical findings, specifically café-au-lait spots and short stature, have an increased risk of having Fanconi anemia. Innovative techniques, such as preimplantation genetic determination, allow the parents to have another child with matching blood characteristics and without Fanconi anemia. At birth, the cord blood can be harvested and used as donor blood for the affected Fanconi anemia child. Numerous hand surgeons and pediatricians fail to consider the diagnosis of Fanconi anemia in children with thumb hypoplasia, leaving the child and the family to suffer the consequences of a painful terminal illness that could otherwise have been treated.
General Considerations in Thumb Hypoplasia
Diagnosis
The diagnosis of thumb hypoplasia is dependent on the degree of deficiency and the presence or absence of any associated anomalies. The combination of thumb hypoplasia and profound radial deficiency is typically diagnosed shortly after birth because the infant’s forearm is foreshortened and the hand deviated in a radial direction. Substantial thumb hypoplasia is also recognized early in infancy because there is marked asymmetry between the thumbs. In contrast, mild thumb hypoplasia may go unidentified for years, and the patient may not present to the physician until adolescence. This late presentation is often perplexing to the patient and disconcerting to the parents. The parents cannot understand how they failed to recognize the child’s hypoplasia before adolescence. They often relate the thumb hypoplasia to some form of recent trauma and question the diagnosis. Our explanation is quite simple: “As one gets older, the activities of daily of life become more complicated, and therefore subtle differences are not recognizable until the child is older.” For example, buttoning, keyboarding, and tying shoes are tasks performed as the child becomes older and are not completed during infancy and early childhood. This explanation removes any feeling of fault and allows the family to focus on the treatment to correct the problem.
The diagnosis is based on the physical examination findings and corresponding x-rays. The length, girth, motion, and stability are important parts of the examination. If there is unilateral involvement, the length and girth are usually compared with the thumb on the contralateral side. A thumb of normal length reaches the point just proximal to the proximal interphalangeal (PIP) joint of the adjacent index finger. On x-ray, a normal thumb is approximately 70% as long as the proximal phalanx of the adjacent index finger. The thumb girth and nail width are approximately 133% and 105%, respectively, of the index finger girth and nail width. The overall thumb motion is assessed along with specific movement at the carpometacarpal (CMC), metacarpophalangeal (MCP), and interphalangeal (IP) joints. Similarly, the stability of each of these joints is assessed by clinical examination and stress testing. Instability of the MCP and/or CMC joints is commonly associated with thumb hypoplasia and directly influences the surgical treatment algorithm. An account of present and absent intrinsic and extrinsic muscles is necessary in order to formulate a surgical plan.
Classification
The Blauth classification of thumb hypoplasia truly guides management ( Table 37.2 ). Type I hypoplasia is minor generalized hypoplasia usually affecting the thenar muscles. As stated beforehand, this slight degree of hypoplasia may present later in life as hand function becomes more intricate and demanding. Type I thumb hypoplasia may or may not warrant treatment, depending on the functional impact. If the lack of opposition is causing functional difficulties, a tendon transfer is recommended.
| Type | Findings | Treatment |
|---|---|---|
| I | Minor generalized hypoplasia | No treatment |
| II | Absence of intrinsic thenar muscles First web space narrowing Ulnar collateral ligament (UCL) insufficiency | Opponensplasty First-web release UCL reconstruction |
| III | Similar findings as type II plus: Extrinsic muscle and tendon abnormalities Skeletal deficiency A: Stable carpometacarpal joint B: Unstable carpometacarpal joint | A: Reconstruction B: Pollicization |
| IV | Pouce flottant, or floating thumb | Pollicization |
| V | Absence | Pollicization |
Type II hypoplasia has distinct findings that guide treatment ( Figure 37.2 and Case Study 37.1 ). There is absence of the thenar muscles innervated by the recurrent branch of the median nerve (the abductor pollicis brevis, opponens pollicis, and superficial head of the flexor pollicis brevis) (see Figure 37.2, A ). The deep head of the flexor pollicis brevis, innervated by the ulnar nerve, is usually present, and it provides MCP joint flexion. The MCP is usually unstable, with laxity or incompetency of the ulnar collateral ligament (UCL) (see Figure 37.2, B ). The MCP joint can also be globally unstable, with incompetency of both the ulnar and radial collateral ligaments. The thumb/index finger or first web space is narrowed and the intervening skin is taut (see Figure 37.2, C ). The web space can appear to be less narrow because the unstable MCP joint drifts into valgus, masking the narrow web space.
Andres was a 9-year-old with type II thumb hypoplasia ( eFigure 37.1 ). Thumb reconstruction was planned, using the present CMC and thumb of adequate girth.
The surgical technique is displayed in eFigure 37.2 and . The long-term outcome is shown in eFigure 37.3 and and .
Type III hypoplasia has the same characteristics as type II hypoplasia with the addition of extrinsic muscle and tendon deficiencies. Absence or hypoplasia of the extrinsic extensors (extensor pollicis longus and extensor pollicis brevis) or flexors (flexor pollicis longus) requires an observant examination of the active movement at the MCP and IP joints. Type III hypoplasia is subdivided into types IIIA and IIIB, which is a crucial differentiation in the treatment paradigm. A type IIIA thumb has a stable CMC joint that is worthy of reconstruction and can provide a worthwhile prehensile thumb. A type IIIB thumb has an unstable CMC joint that requires ablation and pollicization. The unstable CMC joint precludes successful reconstruction because the surgery cannot overcome the basal joint instability. A simple explanation to parents is that this effort would be similar to “trying to build a house without a stable foundation.” Multiple valiant surgical attempts to reconstruct the CMC joint have yielded inferior results (outcome and function) compared with a successful index finger pollicization.
Differentiating between a type IIIA (stable) and a type IIIB (unstable) thumb can be difficult in some cases, but it is fundamental to formulation of a treatment plan. The first metacarpal base and the trapezium do not ossify until about 6 years of age. Therefore, plain radiographs are often unreliable for evaluation of the CMC joint architecture. In a grossly hypoplastic CMC joint, the metacarpal base tapers to a point and the proximal metacarpal is absent ( Figure 37.3 ). However, this plain x-ray finding is not present in milder type III hypoplasia. Advanced imaging studies, such as ultrasound or magnetic resonance imaging (MRI), can be helpful to visualize and evaluate the integrity of the cartilaginous metacarpal base and the trapezium. Repeat examinations, however, may be equally as reliable to detect a thumb unworthy of reconstruction. A child with an unstable CMC joint usually completely ignores the thumb and uses the index finger and long finger for scissor pinch. In addition, the index finger pronates and the long finger/index finger web space widens. In these circumstances, thumb reconstruction is contraindicated and index pollicization is preferred.
Type IV hypoplasia represents a profound deficiency known as a pouce flottant , or floating thumb ( Figure 37.4 ). The thumb remnant is attached to the hand solely by a narrow bridge of skin containing a single neurovascular element. The thumb is floppy and is entirely ignored.
Type V hypoplasia is complete absence of the thumb. On occasion, there will be a small skin nubbin present.
Thumb hypoplasia can also be found in children with ulnar deficiency ( Figure 37.5 ). The treatment for thumb hypoplasia in ulnar deficiency and radial deficiency is the same. Pollicization is indicated for marked thumb hypoplasia. The surgical technique for pollicization is similar, with minor modifications, such as skin design.
The standard indications for pollicization can be expanded to include a thumb smaller than a small finger. This decision to ablate the thumb and pollicize the index finger requires a prolonged conversation with the parents about the rationale for this recommendation. Parents generally come to understand that “function trumps form” and that thumb ablation and index finger pollicization will result in a thumb that is more functional than the small, scrawny thumb that may be formed by reconstruction. When in doubt, parents are given a list of other parents who have made a similar difficult decision regarding thumb ablation. This parent-to-parent communication is invaluable.
Treatment for Thumb Hypoplasia
An experienced hand therapist is invaluable in the evaluation of the child with a hypoplastic thumb. Although there is little need for nonoperative management, the hand therapist’s input is essential and can provide support for the family and facilitate the decision-making process. Following surgery, the therapist becomes a primary care provider who directly affects the success of the procedure.
The classification schema guides treatment. Type I hypoplasia usually does not warrant surgical intervention, because the functional impairment is negligible. Type II or IIIA hypoplasia diminishes function and often requires surgery to provide stability, improve motion, and enhance function. Type IV or V hypoplasia requires index finger pollicization if the index finger is “suitable” for becoming a thumb. A stiff index finger will be a stiff thumb and may not enhance hand function. Therefore, determining the risk/benefit ratio of pollicization requires ample thought and consideration. The operation should follow the Peter Carter 2-4 rule: For some children, surgery can indeed be done “to” them, but it may not necessarily be “for” them. We have slightly modified the 2-4 rule to state that the operation should be done “to” the patient and “for” the patient.
Thumb Reconstruction
Thumb reconstruction for type II and IIA hypoplasia requires addressing all the deficient elements. The narrowed thumb/index finger web space, MCP instability, and thenar muscle absence all require treatment. Thumb/index finger web space narrowing is treated with skin rearrangement and soft tissue release. A four-flap “Z”-plasty lengthens the tight skin and provides a rounded contour to the web space. The theoretical increase in length is 150%. The deeper soft tissue release includes the investing fascia around the adductor pollicis. The princeps pollicis artery and its branches must be identified and protected before division of the fascia. An extremely tight web space may also require partial release of the adductor muscle and/or first dorsal interosseous muscle to obtain adequate breadth.
MCP instability necessitates stabilization. Unidirectional instability with an incompetent UCL is the most common finding. Ligament reconstruction can be performed with local tissue or preferably the residual length of donor tendon from the opposition transfer. Bidirectional or global instability is more challenging to manage. Reconstruction of both the radial and ulnar collateral ligaments with a tendon graft is an option. MCP joint chondrodesis is preferred, however, to achieve firm stability and provide a stable platform for the opposition transfer to function. The details of MCP joint chondrodesis are discussed in Chapter 39 . UCL insufficiency can be secondary to an anomalous connection between the flexor pollicis longus and extensor pollicis longus muscles (i.e., pollex abductus ). The pollex abductus attenuates the UCL over time and prevents active thumb IP joint motion. The key to determining its presence is the physical examination prior to surgery. During attempted thumb IP flexion, the MCP joint deviates into valgus rather than bending the IP joint. Surgery must release the pollex abductus when UCL reconstruction is performed.
Thenar absence requires a tendon transfer to provide thumb opposition. There are a variety of donor muscle-tendon units to choose from, including the flexor digitorum superficialis (FDS) (long or ring finger), abductor digiti minimi, extensor carpi ulnaris, and extensor indicis proprius. Each donor muscle-tendon unit has its advocates and its advantages and disadvantages. The long or ring finger FDS is preferred because of its length, power, expendability, and synergism and the technical ease with which it can be used. If the FDS is unavailable, the other donor options are considered.
Flexor Digitorum Superficialis Opponensplasty With Ulnar Collateral Ligament Reconstruction.
The patient is placed supine on the operating room table ( Box 37.1 and see and ). The procedure is usually performed under general anesthesia. A single dose of intravenous preoperative antibiotics is administered. The limb is prepped and draped in sterile fashion. Chlorhexidine gluconate and alcohol prep (ChloraPrep, CareFusion, Leawood, KS) is preferred and may be more effective than Betadine prep in eliminating bacteria. In addition, when chlorhexidine is used, iodine, which can migrate beneath the tourniquet and cause burns, need not be used.
Limb is exsanguinated and the tourniquet is inflated
Four-flap “Z”-plasty of thumb/index finger web space with release of tight fascia
Ring finger FDS tendon is isolated at base of finger and in distal forearm
Thoracodorsal neurovascular pedicle is isolated
Ring finger FDS tendon pulled through carpal tunnel and into forearm
Radial one half of the distal 2 to 3 cm of FCU tendon made into a loop for the FDS tendon
Ring finger FDS tendon passed through the FCU loop
Skin incision along the radial side of thumb MCP joint
Subcutaneous tunnel is made between the radial side of thumb and the volar forearm FCU loop
FDS tendon is passed under the skin to the radial side of the thumb
Metacarpal head is isolated and a 0.045-inch Kirschner wire drilled across the metacarpal head parallel to the joint surface
Hole is enlarged with a drill bit to allow passage of the FDS tendon
MCP joint is reduced and stabilized with a longitudinal 0.045-inch Kirschner wire drilled antegrade from the tip of the thumb across the MCP joint
FDS tendon is passed through the drill hole to ulnar side of thumb for ligament reconstruction
FDS tendon is sutured to the surrounding bone and periosteum along the radial side of the thumb while setting the appropriate tension in the tendon transfer
FDS tendon is directed to the base of the proximal phalanx and sutured directly into the bone to reconstruct the UCL
Skin is closed with absorbable suture and the limb is immobilized in a long-arm thumb spica cast for 3 weeks
FCU , Flexor carpi ulnaris; FDS , flexor digitorum superficialis; MCP , metacarpophalangeal; UCL , ulnar collateral ligament.
The limb is exsanguinated and the tourniquet is inflated. The incisions are carefully drawn ( Figure 37.6 ). The narrowed thumb/index finger web space is widened via a four-flap “Z”-plasty. Each limb of the “Z”-plasty should be equal in length. The radial limb can be extended in a proximal direction to expose the UCL and the MCP joint. The ring finger FDS tendon is isolated at the base of the finger and in the distal forearm. A short oblique incision is made at the base of the ring finger, and a zigzag or oblique incision is made along the volar ulnar forearm. The flexor carpi ulnaris (FCU) tendon is also isolated. An additional skin incision is made along the radial side of thumb MCP joint to expose the ultimate site for FDS tendon attachment. The FDS tendon is identified at the base of the ring finger and separated from the flexor digitorum profundus (FDP) tendon. The FDS tendon is also isolated in the forearm ( Figure 37.7 ). The FDS tendon is tagged with a suture and cut at the base of the ring finger while the underlying FDP tendon is guarded. An Allis tissue forceps (Jarit, Hawthorne, NY) is placed around the ring finger FDS tendon in the forearm and used to roll the tendon through the carpal tunnel ( Figure 37.8 ). If the FDS tendon fails to roll into the forearm, it must be retrieved into the hand using tag suture. An assessment for FDP and FDS attachments and/or entrapment within the Camper chiasm is performed.
An FCU tendon loop is constructed as a pulley for the FDS tendon. The distal 2 to 3 cm of FCU tendon is isolated. The radial half of the FCU tendon is harvested, preserving its distal attachment into the pisiform ( Figure 37.9 ). The radial half of the tendon is passed through the retained FCU at the pisiform and sutured to form a loop. The ring finger FDS tendon is passed through the FCU loop prior to transfer across the palm ( Figure 37.10 ).
A subcutaneous tunnel is made between the radial side of thumb and the volar forearm incision for channeling the ring finger FDS tendon. The FDS tendon is passed under the skin to the radial side of the thumb ( Figure 37.11 ). The metacarpal head is isolated and a 0.045-inch Kirschner wire drilled across the metacarpal head parallel to the joint surface ( Figure 37.12 ). Minifluoroscopy ensures appropriate Kirschner wire positioning. The hole is enlarged with a drill bit to allow passage of the FDS tendon. The MCP joint is reduced and stabilized with a longitudinal 0.045-inch Kirschner wire drilled antegrade from the tip of the thumb across the MCP joint. The wire is cut short and a Jurgan pin ball (Jurgan Development and Manufacturing, Madison, WI) applied. The FDS tendon is passed through the drill hole to the ulnar side of the thumb for ligament reconstruction ( Figure 37.13 ). If the diameter of the tendon is too large, one slip of the FDS can be removed.
At this point, the wrist is placed into slight extension and the FDS tendon tensioned until the thumb is positioned in opposition. Tenodesis is used to assess tension, and after correct tension is achieved, the FDS tendon is sutured to the surrounding bone and periosteum along the radial side of the thumb. This maneuver sets the tension in the opposition tendon transfer. Typically, the tendon can be seen tenting the skin when the wrist is placed into extension. The remaining FDS tendon that had been passed through the metacarpal head is used to reconstruct the UCL. The FDS tendon is directed to the base of the proximal phalanx and sutured directly into the bone. Usually, the FDS tendon is long enough that it can be passed back onto itself to complete a double-stranded repair ( Figure 37.14 ).
The skin is closed with absorbable suture and the limb is immobilized in a long-arm thumb spica cast for 3 weeks. The Kirschner wire is removed and a short-arm thumb spica splint is fabricated. Active motion and therapy are initiated. Protective splinting of the thumb is continued until 3 months after surgery.
Pollicization
Pollicization is indicated for types IIIB, IV, or V hypoplasia. The technique is similar for each type, with subtle variations depending upon whether a hypoplastic thumb is present or absent. In type IIIB hypoplasia, vascularized fat from the ablated thumb can be used to augment the first web space or thenar eminence. In type IV or V hypoplasia, this option is unavailable.
Pollicization Procedure.
The current technique of pollicization represents a consolidation of contributions from surgeons over the past 100 years ( Box 37.2 , Case Study 37.2 , and see ). Following general anesthesia, the child is placed in the supine position. Preoperative antibiotics are routinely administered. The extremity is prepped and draped in sterile fashion. A sterile pediatric tourniquet (Delfi Medical Innovations, Vancouver, Canada) is placed on the upper arm. Exsanguination should be gentle so that some filling of the digital vessels can be maintained in order to facilitate visualization.
Limb is gently exsanguinated and the tourniquet is inflated
Skin incision proposed by Ezaki and Carter
Palmar skin is incised and the radial neurovascular bundle is isolated
Dissection proceeds in an ulnar direction to identify the common digital vessels to the index finger/long finger web space
Proper digital nerves to the ulnar side of the index finger and the radial side of the long finger are isolated
Proper digital artery to the long finger is ligated with a ligature clip
First annular pulley of the index finger is incised
Divide intermetacarpal ligament between index finger and long finger
Dorsal skin incision is sharply elevated with preservation of dorsal veins
The first dorsal and palmar interossei muscles are released with a portion of the hood
Metacarpal index finger is shortened by a saw cut at the metaphyseal flare and a knife cut through the physis leading to an epiphysiodesis
Index metacarpophalangeal joint is fixed into hyperextension using nonabsorbable suture material passed through the epiphysis and dorsal capsule
Kirschner wire drilled antegrade through the metacarpal epiphysis, into the proximal phalanx, and out the proximal interphalangeal joint
Kirschner wire used as a joystick to align the index metacarpal into 45 degrees of abduction and 100 to 120 degrees of pronation
Kirschner wire is drilled retrograde across the metacarpal base into the carpus
Transfer the first dorsal interosseous to the radial lateral band and the first palmar interosseous to the ulnar lateral band about the PIP joint
Skin is closed with absorbable suture with resection of any redundant skin and Kirschner wire is cut short
Emma is a 4-year-old with ulnar deficiency and marked left thumb hypoplasia ( eFigure 37.4 ). Treatment included bone and joint reorganization and muscle reorganization:
Bone and joint reorganization:
- •
DIP joint → IP joint
- •
PIP joint → MCP joint
- •
MCP joint → CMC joint
- •
Metacarpal → Trapezium
Muscle reorganization:
- •
First PI → adductor pollicis
- •
First DI → abductor pollicis brevis
- •
Extensor indicis proprius → extensor pollicis longus
- •
Extensor digitorum communis → abductor pollicis longus
The surgical procedure is demonstrated in and eFigure 37.5 .
The challenging rehabilitation required communication and experience ( eFigure 37.6 ), but a successful outcome was achieved ( eFigure 37.7 and ).
The skin incision must allow index finger transposition and reconstruction of an abundant thumb/index finger web space. The skin incision proposed by Marybeth Ezaki and Peter Carter is used because it allows more glabrous skin to be placed along the palmar aspect of the index finger ( Figure 37.15 ). The palmar skin is incised first, and the radial neurovascular bundle is isolated, although the artery can be extremely small. In children with type IIIB or IV hypoplasia, the single vessel to the hypoplastic thumb can be traced to the radial neurovascular bundle of the index finger to ease identification ( Figure 37.16 ). The dissection next proceeds in an ulnar direction to identify the common digital vessels to the index finger/long finger web space ( Figure 37.17 ). The proper digital nerves to the ulnar side of the index finger and the radial side of the long finger are isolated. Proximal nerve microdissection is required to further separate the proper digital nerves prior to pollicization. On occasion, as the dissection of the digital nerve proceeds in a proximal direction, one will encounter a neural loop that encircles the artery. This loop must be addressed to prevent constriction of the artery during index finger transposition. The loop can be widened to avoid arterial compression or the smaller of the two nooses can be cut. The proper digital artery to the long finger is ligated with a ligature clip ( Figure 37.18 ). This allows tension-free index finger pollicization vascularized by the radial digital artery and the common digital artery to the index finger/long finger web space. The ligature clip acts as a visual reminder of the location of the proper digital artery.
The first annular pulley of the index finger is incised to prevent buckling of the flexor tendons after index finger shortening ( Figure 37.19 ). The intermetacarpal ligament is also divided ( Figure 37.20 ). The dorsal skin incision is sharply elevated with preservation of as many dorsal veins as possible. The extensor or flexor tendons are not shortened, because these musculotendinous structures adapt over time.
The first dorsal and palmar interosseous muscles are dissected to their attachments into the extensor hood ( Figures 37.21 and 37.22 ). The interosseous muscles and tendons are released with a portion of the hood in expectation of transfer. The tendons must be carefully dissected from the MCP joint collateral ligaments to avoid entering the joint. The neurovascular bundles must also be shielded during elevation of the interossei. Prior to cutting the metacarpal, the eventual insertion sites for the tendon transfers are identified and tagged within the extensor mechanism over the PIP joint. This facilitates later transfer of the first dorsal and first palmar tendons into the radial and ulnar lateral bands, respectively.
The index finger must be shortened. The distal cut is made directly through the physis using a knife ( Figure 37.23 ). This physeal cut leads to growth plate ablation (epiphysiodesis) to prevent unwanted growth of the index metacarpal. A fine-bladed saw is used to cut the metacarpal base through the metaphyseal flare in the plane of the intended thumb ( Figure 37.24 ). The index metacarpal bone is removed from its base to the epiphysis ( Figure 37.25 ). A rongeur is used to widen the base by opening or pedaling the surrounding cortex to promote healing ( Figure 37.26 ).
The normal index MCP joint hyperextends and the normal thumb CMC joint does not hyperextend. To correct this discrepancy, the index MCP joint is fixed into hyperextension, placing the remaining metacarpal head into flexion ( Figure 37.27 ). This is achieved by suturing the MCP joint into hyperextension using a suture material passed through the epiphysis and dorsal capsule. Subsequently, a Kirschner wire is placed through the metacarpal epiphysis or the base of the proximal phalanx ( Figure 37.28 ). The Kirschner wire is drilled through the proximal phalanx and out the PIP joint ( Figure 37.29 ). This Kirschner wire is used as a joystick to facilitate index finger positioning ( Figure 37.30 ). Interosseous sutures are rarely used to augment fixation. The index finger metacarpal epiphysis is aligned anterior to its metaphyseal base with meticulous positioning into 45 degrees of abduction and 100 to 120 degrees of pronation ( Figure 37.31 ). Once the position is deemed satisfactory, the Kirschner wire is drilled retrograde across the metacarpal base into the carpus. The Kirschner wire is cut short and a Jurgan pin ball is applied. Further stability is achieved via tendon transfer of the first dorsal interosseous to the radial lateral band and the first palmar interosseous to the ulnar lateral band about the PIP joint ( Figure 37.32 ). The skin is judiciously inset with absorbable suture. Any redundant skin is excised ( Figure 37.33 ). Whenever possible, the first web space suture line is advanced dorsally to minimize any suture line within the commissure ( Figure 37.34 ). The tourniquet is deflated and the “thumb” observed for 5 minutes. The arterial circulation typically returns rapidly, although vasospasm can result. Time, warm soaks, and patience routinely lead to resolution. Persistent lack of blood inflow requires exploration for arterial spasm that can resolve with lidocaine, arterial kinking, or iatrogenic injury. Venous congestion is a more common problem that requires reapplication of a looser dressing and/or release of any taut sutures.
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