Clinodactyly is defined as an angular deviation of a digit in the coronal plane distal to the metacarpophalangeal joint. It originates from Greek klinen, “to bend” and dactylos, “a finger.”1 Clinodactyly is a physical sign, not a disease.1 Deviation of the digit can occur as an isolated anomaly, in association with several syndromes or as a result of physical or thermal trauma (ie, frostbite).2 Smith is credited with the first description of clinodactyly in 1896 when he reported on the radiographic findings of clinodactyly and the association with Down syndrome.3 The current article will concentrate on isolated/familial clinodactyly and those in association with syndromes. Most authors agree that ≥10 degrees of angulation defines clinodactyly.4 Asymmetric longitudinal growth of ≥1 of the phalanges results in a trapezoidal or triangular bone shape that leads to deviation of the digit.
The radially deviated small finger is the most commonly involved and the finding is often present bilaterally5–7 (Fig. 1). The incidence of clinodactyly has been reported to range between 1% and 19.5%,4,8–10 with a higher incidence in syndromic populations compared with nonsyndromic populations.9,11 There are 2 explanations for the wide range of incidence. First, there was previously no consensus on what degree of angulation justified the diagnosis, and second, mild deviation often goes unrecognized. Dr Flatt evaluated over 3000 children during his illustrious career, and abnormalities of the small finger were the third most common congenital hand abnormality seen in his practice.8,11 Marden and colleagues reported on 4412 infants born over a 2-year period in Madison, Wisconsin and found 1% of the healthy babies demonstrated moderate to severe curvature of the small finger, whereas 12.2% of the infants with other major anomalies had clinodactyly.12 Similarly, Hersh et al13 reported an incidence of 1 in 1000 based on population studies from Northern Ohio.
Deviation of the thumb is the next most common and can occur due to the presence of an extra phalanx (triphalangeal thumb)7 (Fig. 2). The extra bone can be triangular or trapezoidal in shape, and the malalignment can lead to difficulty with pinch14 (Fig. 3). A triphalangeal thumb shows autosomal dominant inheritance.
Index finger clinodactyly is relatively uncommon, with incidence at 0.2% to 2% in population studies.4,7,10,15 It presents at birth, is unilateral, and with a male predominance.14 The index finger will most commonly deviate radially.15 Index clinodactyly is known to occur in sporadic, familial, and syndromic forms, such as in the association with Trevor disease.16
Clinodactyly is typically an isolated anomaly and exhibits autosomal dominant inheritance17–19 with incomplete (50% to 60%) penetrance.13 This form of clinodactyly is referred to as “Familial clinodactyly.” There can be variable expression among family members, and an affected individual may demonstrate slight differences in the degree of curvature when comparing hands. Males are more likely to express the phenotype.4,20 There are at least 60 syndromic associations including Down syndrome, Rubinstein-Taybi syndrome, Apert syndrome, Turner syndrome, Poland syndrome, Russell-Silver syndrome, and oculodentaldigital dysplasia.2,6,8,19 Down syndrome is the most common syndromic association with 35% to 79% of people with Down syndrome displaying small finger clinodactyly.11 Clinodactyly can be associated with syndactyly, polydactyly, cleft hand, triphalangeal thumb, and symphalangism, and in these cases, clinodactyly is generally of minimal significance11 (Fig. 4).
Early literature indicated that clinodactyly was the result of developmental arrest of the ossification center of the middle phalanx of the small finger.13 However, the pathophysiologic understanding of the deformity has been expanded, and it is now understood that an abnormal growth plate leads to a progressive deformity as the child grows.20 The middle phalanges are the most commonly involved because they are the last bones of the hand to ossify.11 Deviation of the distal phalanx at the distal interphalangeal (DIP) joint occurs because the middle phalanx is shorter on one side than the other. In 1964, Jones21 first described the pathology in severe clinodactyly, as the result of a small triangular bone or “delta phalanx.” Theander and Carstam, however, introduced the term “longitudinally bracketed diaphysis” as they noted the deformity not only involved the phalanges, but also the metacarpals.22,23 In 1981, Light and Ogden24 reported that the distortion in longitudinal growth was due to the presence of a “longitudinal epiphyseal bracket” of the middle phalanx that results in angulation of the digit. The pathology was correctly attributed to the epiphysis, not the diaphysis. The primary ossification center fails to completely develop, with a portion of the bone collar remaining as cartilage. The proximal epiphyseal ossification center (secondary) can extend distally and ultimately coalesce with an abnormal persistent distal epiphyseal ossification center. Thus, a C-shaped cartilage epiphysis develops on the shorter side of the phalanx that does not contain cortical bone or periosteum. The proximal and distal joint surface lose parallelism,25 and the distortion of growth leads to a shortened middle phalanx (brachymesophalangism) that is often triangular or trapezoidal in shape. The ultimate shape of the abnormal phalanx depends upon the presence of a complete or incomplete bracket as well as the age of the child (Fig. 5). If the longitudinal epiphyseal bracket has ossified early in development, a triangular bone will result. Thus, the term “delta phalanx” or “delta bone.” If the bracket is incomplete or partially ossified, then some longitudinal growth will occur, and the metaphyseal/diaphyseal segment will be trapezoidal in shape26,27 (Figs. 6–8).
Important aspects of evaluation include assessing for functional limitations and history of progression, family history, and any other associated anomalies or syndromes. Patient satisfaction with finger appearance should be understood, as this may be the primary factor leading to presentation.
Measurement of the radial deviation of the digit can be done with the finger in full extension. A technique for obtaining the degree of angulation4 involves centering a goniometer on the dorsal aspect of the DIP joint. One limb is aligned parallel to the middle phalanx and the other limb parallel to the distal phalanx. Children should also demonstrate a composite fist that will allow for evaluation of finger scissoring (Fig. 9).
Clinodactyly is a deformity that is rarely limiting with regard to activities of daily living and overall hand function. In the small finger, the deformity may not cause impairment of movement13 because compensatory finger abduction will prevent interference with finger flexion. Patients more commonly present due to the esthetic difference. Mild radial curvature may be an incidental finding by a hand surgeon during the evaluation of an unrelated issue. In pedigree studies, many family members were unaware of the radial curvature until evaluation by the investigator and were not impaired by the physical finding.18
A single posteroanterior (PA) view of the hand is often adequate for evaluation of clinodactyly. Because of the high incidence of bilateral involvement, a bilateral PA view of the hands on a single flat plate is most beneficial (Fig. 10). Even when there is unilateral involvement, the bilateral PA view may be helpful for comparison purposes. In discussions with parents, the unaffected side can help to show the radiologic difference between the 2 hands, or perhaps subtle radiologic anomalies will be identified that are not clinically apparent.
Skvarilova and Smahel10 first discussed radiologic measurement of the deformity by measuring the angle created when drawing a line along the axis of the distal and middle phalanges.
Cooney28 proposed a classification scheme for clinodactyly (Table 1). However, the classification has not been extensively utilized in published literature.
Most cases of clinodactyly do not require surgical intervention. Observation of the deformity is indicated when there are no functional limitations. Up to 10 degrees of deviation of the thumb and small finger is considered normal.4,7,10,11 However, as the degree of deformity increases functional impairments may arise such as difficulty with playing the piano or other musical instruments, keyboarding, or fine manipulation.10,29 This is especially true of thumb or central digit involvement, as increasing angulation will lead to impaired pinch or altered flexion of the digits.20
Treating physicians should not only note the angle of deformity, but also functional limitations, the progression of the disease, and patient satisfaction when developing a treatment plan. Splinting and therapy have not proven to be effective forms of treatment.14,24,27 However, there may be a role for preoperative or postoperative splinting to help with soft tissue stretching or protection, respectively.14,28
Increasing angulation can lead to scissoring of the digits, usually of the small and ring finger. Dr Flatt8 comments, “I rarely operate on overlapping fingers, despite parents’ desires, unless the finger overlaps on fist making. This overlap deprives the hand of the valuable ulnar border locking of grasp provided by the most ulnar digit.” Several different operative treatments have been proposed including closing-wedge osteotomy,28,30 opening-wedge osteotomy with or without bone graft,29,31 reverse closing-wedge osteotomy, distraction osteogenesis32 and epiphyseal bar resection.5,33 The indications for these procedures have varied by author, with differences attributable to the definition of abnormal degree of deviation.15,33 Some authors have proposed surgical intervention may be appropriate for deviation >20 degrees,5,6,11,26,31,33 and others have suggested >25 degrees with functional impairment.30 However, there are no standards or published guidelines advising surgeons on the degree of angular progression that would warrant surgical intervention.
Epiphyseal Bar Resection
Jones first described division of the continuous epiphyseal bracket in 1964. The procedure involves removing cartilage at the midpoint of the maximal concavity until bleeding bone is exposed. They reported return of longitudinal growth following this procedure, but correction of angular deformity often required a second osteotomy at an older age.21,23,24 The addition of fat interposition was termed physiolysis.
Vickers was the first to describe this procedure in 1987. He reported on 12 digits in which he resected the mid-portion of the abnormal continuous epiphysis with the underlying physis and interposed fat graft. Several authors have described the surgical technique of excising the longitudinal epiphyseal bar.5,26,29,33 The key is to identify the proximal interphalangeal and DIP joints utilizing needle localization and fluoroscopy (Fig. 11). The epiphyseal bar should be removed along the concave side of the phalanx midway between the 2 joints to avoid injury to the joint or physis. The terminal portions of the epiphysis (proximal and distal) will still be able to grow longitudinally. Fat can be obtained locally or through a separate donor site and placed in the resulting defect. The goal of the procedure is to allow continued longitudinal growth from the proximal and distal portions of the epiphysis with hope for correction of the deviation.
Caouette-Leberge and colleagues retrospectively reviewed 35 fingers in 23 children who underwent physiolysis for lateral deviation of the digit ≥20 degrees (mean, 34.4 degrees). The average age at the time of surgery was 6.6 years. Children with greater deformity (>40 degrees) and children below the age of 6 obtained statistically higher corrections in angulation at 1 year. Children with >40-degree angulation had a mean correction of 20 degrees, whereas children with <40-degree angulation had an average improvement of 7.5 degrees. This finding remained true even after adjusting for a confounding effect with younger children having greater angulation.5
Medina and colleagues reported on a minimum 6-year follow-up after early physiolysis of 27 delta phalanges in 27 fingers with mean deviation of 38 degrees. All of the children were below age 6 at the time of surgery, and the average mean angle was 8 degrees at final follow-up. No secondary surgeries were necessary in this population.33
Complications of this procedure include typical surgical risks, incomplete correction of angulation, and premature physeal closure. These complications must be considered and discussed with parents preoperatively. Surgeons and parents must understand that postoperative correction of the deviation will occur slowly over many years, but generally can be first seen on radiographs at 1 year after surgery.33 Incomplete resection of the epiphyseal bar can lead to failure of deformity correction,5 and Medina et al33 comments on the importance of removing the white epiphysis until healthy red, cancellous bone is visualized. In addition, the procedure should not be performed on children with a small triangular phalanx because the epiphyseal bracket has completely ossified and there is no longitudinal growth potential remaining.5,26 There have been 2 studies that reported early physeal closure in a total of 3 patients.5,34 Two patients developed physeal closure after having the procedure performed twice on the same digit.5 To minimize the risk of complications, the procedure should be performed before the age of 6 and revision surgeries should be avoided.5,26
The procedure is usually performed for simple clinodactyly in older children or adolescents.11 A small bone wedge is removed from the convex side of the middle phalanx, the digit is then aligned, closing the defect, and a Kirschner wire is used to stabilize the osteotomy (Fig. 12). The downside to this approach is that the already short middle phalanx is further shortened. In 1 case series, 25 digits with >25-degree angulation, in 17 patients were evaluated at a mean follow-up of 6 years after closing-wedge osteotomy and demonstrated an average improvement of 24 degrees in clinical and radiographic angulation. Range of motion was maintained. One patient had residual deformity of 10 degrees after surgery, but had a severe deformity preoperatively.30 Despite inclusion criteria of >25-degree angulation in this study, the authors suggest consideration of closing-wedge osteotomy in patients with >15-degree angulation.
Early case series found that osteotomy in young children had poorer results with persistent deformity being the most common complication.7 In large corrections, a secondary mallet deformity can occur due to shortening and subsequent laxity of the extensor tendon.28 Shortening of the extensor tendon should occur at the time of osteotomy to help prevent this complication.11 Variations in closing-wedge osteotomy have been reported, such as the partial excision greenstick osteotomy described by Tansley and Pickford.35 In their technique, a wedge of bone that is 75% of the width is removed from the convex side of the phalanx. Following removal of the bone wedge, a greenstick fracture is created to allow closure of the defect and correction of the deformity. The osteotomy site is secured with interosseous wire. They performed this procedure on 2 patients and reported good outcomes in range of motion and alignment at 6 months.35
Several authors have described opening-wedge osteotomy for treatment of clinodactyly6,29,31 (Fig. 13). With this osteotomy technique the length of the digit is preserved and the longer cortical surface is left intact. However, soft tissue rearrangement may be necessary and relative lengthening may lead to joint stiffness.27 Management of the soft tissue has included simple Z-plasty to more complex neurovascular flaps.36 The procedure is generally indicated in older children and adolescents to avoid the technical challenges associated with osteotomy of a small phalanx. Some have advocated for the use of bone graft,28,31 yet others have suggested that bone graft is not necessary due to the reliable healing potential of children to consolidate the void.29
In the series by Piper and colleagues, 13 small fingers in 9 patients with >20-degree angulation were treated with opening-wedge osteotomy at an average age of 11 years. At follow-up of 24 months there was significant clinical and radiographic angular improvement of 32 and 29 degrees, respectively. Three digits in 2 patients lost DIP joint motion and 1 patient had a recurrence.
Complications of this procedure include infection, nonunion, joint stiffness, and recurrence. Recurrence can occur if the bone graft resorbs during the healing period or the stabilizing pins are removed before complete consolidation. Piper et al31 recommend using distal radius autograft when there is a visible defect following opening of the osteotomy, thus, indicating that autograft should be considered in all cases. However, longitudinal studies evaluating incomplete correction and recurrence after opening-wedge osteotomy are lacking.
Reversed Wedge Osteotomy
With this osteotomy technique a wedge of bone is removed from the convex side of the phalanx, reversed, and inserted on the concave side of the digit22,23 (Fig. 14). It is then transfixed with a K-wire. This technique is technically demanding, as it requires precise judgment to remove an appropriate sized wedge of bone.11 Preoperative planning should include measuring the desired degree of angular correction and determining the width of diaphyseal bone that would provide that degree of correction. An osteotome or sharp bone cutter should be used to create the osteotomy, as power saws will remove bone length.8 In the small series by Carstam and Theander, 3 patients with 4 digits were treated with this procedure with report that the angulation was eliminated or markedly reduced in all cases. All of these children were older than 8.23 Others have cited concerns for early growth arrest. The wedge of bone removed is diaphyseal, and when it is reversed the diaphyseal bone will bridge the epiphysis with the potential for early consolidation and growth arrest.24
Distraction osteogenesis has been proposed as a treatment for clinodactyly in older children or teenagers who can comply with fixator cares. An opening-wedge osteotomy is performed and a fixator is applied to maintain correction of angulation and length while complete bony consolidation occurs. However, the current literature reports on only 3 patients with no quantifiable data on degree of correction or subsequent finger range of motion.32 No complications were reported in that small series.
The literature available to surgeons regarding the treatment of clinodactyly is composed of small, retrospective case series with heterogenous populations. Thus, subsequent treatment recommendations are limited by the lack of robust evidence. However, with an incidence of 1% in healthy newborns and mild phenotypic expression in many children, large case series or randomized controlled trials are not likely. A multicenter collaboration of pediatric hand surgeons has led to a prospective enrollment database of child with congenital upper limb deformities (COULD). With this approach, children with clinodactyly will be longitudinally evaluated, and as the follow-up time period increases, the information gathered will help guide future treatment recommendations.
On the basis of the available evidence, a thorough history and physical examination should be performed. Functional implications and cosmetic concerns should be understood, both from the patient (if able) and the parents. The family should be asked about any possible progression. A PA radiograph of the bilateral hands should be obtained to evaluate the bone morphology.
At any age, if there is <30 degrees of angulation and no functional limitation, counseling and reassurance are the mainstay of treatment. A younger child warrants repeat evaluation. A second clinical evaluation is offered in 6 months to determine whether there has been any angular progression, or the parents are advised to schedule a follow-up appointment if they are concerned by a change in appearance.
In children below age 6, with >30 degrees of angulation, and a trapezoidal-shaped bone, physiolysis should be considered. It may also be reasonable to allow a short period of observation followed by reevaluation to assess for progression during that time period. Before proceeding with physiolysis parents should be counseled on the risks, as well as the expected timeframe for correction.
Children older than age 6 with >30 degrees of angulation are best served with an osteotomy. There is not 1 osteotomy proven better. For smaller corrections, closing-wedge osteotomy is reasonable and technically easier. In larger deformities, an opening-wedge or reverse opening-wedge will help maintain length.
Regardless of intervention chosen, counseling and reassurance remains the mainstay of treatment in children with clinodactyly.
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