In the search for factors that predict recurrence after use of the Ponseti method for successful treatment of idiopathic clubfoot, conclusive evidence is in short supply. However, the one factor that is consistently associated with the risk of recurrence is compliance with brace wear.
By Rachel Y. Goldstein, MD, MPH
Idiopathic clubfoot is a common congenital anomaly, affecting .5 to 2 infants per 1000 live births.1,2 Throughout the 1970s and 1980s, the pervasive thought was that the rigid clubfoot deformity was not amenable to conservative treatment and that large posteromedial release was required.3 Surgical treatment was bolstered by initially promising results.4-10 However, it soon became apparent that extensive surgical releases resulted in stiff, painful, and arthritic feet that considerably impaired quality of life.9-13 Additionally, these patients suffered from multiple postoperative complications, including skin necrosis, infection, deformity recurrence, pain, stiffness, overcorrection, and undercorrection.9,10
In 1963, Ponseti initially presented his technique for manipulation and serial casting in the Journal of Bone and Joint Surgery;14 however, it did not generate much interest among orthopedists at that time. It was not until 1980, when Ponseti’s group reported their long-term results with serial casting,15 that some surgeons began to adopt his technique. This trend was bolstered by the unsatisfactory long-term results associated with surgically treated clubfeet being reported around the same time.9-12 Later, the establishment of support group websites by parents of children with clubfeet treated by Ponseti furthered the popularity of this treatment method.16
In a 2003 survey of Pediatric Orthopaedic Society of North America (POSNA) members, 99% of respondents indicated they initially treat clubfoot with serial cast applications, and 65% use the Ponseti technique.17 In the US between 1996 and 2006, the rate of extensive surgery to treat idiopathic clubfoot in patients younger than 12 months decreased substantially, from just over 70% in 1996 to just over 10% in 2006.2
While initial correction rates with the Ponseti method are greater than 90%,18-23 researchers have reported recurrence rates of nearly 30%.20,24,25 Predicting which patients are likely to experience recurrence, and will therefore require more diligent follow-up, is an important area of focus in the treatment of idiopathic clubfoot.
Ponseti postulated that other conservative techniques fail because attempts to correct the severe supination of the typical clubfoot by forcefully pronating the forefoot causes an increase in the cavus posture and a break in the midfoot.26 This also leads to jamming of the anterior tuberosity of the adducted calcaneus against the undersurface of the head of the talus.26
Ponseti’s technique differs from the previous conservative treatment methods in that the completely supinated foot is abducted under the talus.16,26-29 The talus is secured against rotation in the ankle mortise by applying counter pressure with the thumb against the lateral aspect of the head of the talus. This manipulates the foot without holding the hindfoot fixed, allowing the calcaneus to rotate in relation to the talus.
Serial casting to correct clubfoot deformity begins as soon after birth as possible. The technique involves a choreographed series of manipulations maintained with a long leg plaster cast. 16,27,30 The initial step involves correction of the cavus through elevation of the first ray of the forefoot and supination of the forefoot to recreate a normal appearing arch. Subsequent casts gradually abduct the foot underneath the stabilized talar head. After at least 60° of abduction, the equinus is corrected. If at least 15° of dorsiflexion cannot be achieved with manipulation, a percutaneous heel cord tenotomy is performed.
Once the final correction is obtained, it is maintained with a cast for three weeks. The foot is then held with a foot abduction orthosis (FAO). The FAO is usually worn 23 hours per day for the first three months, followed by nighttime and naptime wear for three to four years,20,27 though some investigators have found it is difficult to get a child to wear the brace after three years.18 Also, to date, no studies have determined how long the FAO actually needs to be worn.
Initial correction rates of idiopathic clubfoot with the Ponseti technique have been reported to be between 90% and 100%.18-23 The Ponseti technique provides excellent early results and may limit the necessity of extensive surgical procedures in young children.31
At two years after initiating the FAO, one midterm analysis found that clubfoot correction was well maintained: 86% of patients required no further treatment, 13% required recasting, and only 1% of patients required extensive surgery.18 In a randomized study of idiopathic clubfeet comparing the Ponseti technique with extensive clubfoot releases, Zwick and colleagues found that at three years the mean score for the Functional Rating System of Laaveg and Ponseti was higher in the Ponseti group.32 They also found that passive dorsiflexion and passive inversion-eversion were greater in the Ponseti group. PODCI (Pediatric Outcomes Data Collection Instrument) scores and radiographic outcome measures were similar for the two groups.
In a long-term study of patients treated with the Ponseti technique, 74% demonstrated good to excellent results at 30-year follow-up.15 In addition, more than half of the feet followed long term did not require any further treatment beyond additional casting and percutaneous Achilles tendon lengthening.15 A different study noted good to excellent results at 25-year follow-up in 78% of patients.33
Predicting clubfoot recurrence
As mentioned earlier, while initial correction rates are greater than 90%,18-23 authors have also reported recurrence rates of nearly 30%.20,24,25 Ponseti considered recurrence of the deformity as part of the initial pathology, rather than a sign of undercorrection. He recommended recasting, repeat Achilles tendon lengthening, and, if there was marked supination, tibialis anterior tendon transfer.14 Multiple studies13,20,23,25,34-37 have attempted to determine which clubfeet will respond to manipulation and casting and which will not.18 Numerous potential risk factors for clubfoot recurrence have been studied.
Atypical deformity. In 2005, Morcuende and colleagues described a new subset of clubfoot they termed the “atypical clubfoot.”34 These feet are characterized by a volar crease, a small bean-shaped foot, a shortened big toe, and a stiff foot. The group reported that these atypical clubfeet may be more resistant to manipulation and therefore at increased risk of failing conservative treatment.
In 1987, Bensahel and colleagues reported their results for a single stage posteromedial release in patients with clubfoot resistant to aggressive physical therapy.35 They categorized the feet into idiopathic, neurologic, and “malformative,” which they defined as clubfeet associated with other congenital deformities, such as arthrogryposis. The results varied with etiology, and the researchers reported that idiopathic feet had a “good” outcome 88% of the time but the malformative feet had a “good” outcome only 25% of the time.
Several demographic characteristics, including sex, race and ethnicity, and age at initial visit, also have been postulated to contribute to the risk of recurrence.
Sex. Most studies report a higher prevalence of idiopathic clubfoot deformity in male patients, with male-to-female ratios ranging between 2.5:1 and 6:1.1.1,38,39 And, in a study of nonidiopathic clubfoot, the predilection for male patients was also found across a diverse array of neuromuscular and genetic causes of clubfoot.40 Kruse et al suggested that, given the higher prevalence of clubfoot in male patients, female patients may require a greater number of genes, or more potent genes, to inherit clubfoot.41 They found that affected female patients were 5.5 times more likely than male patients to transmit idiopathic clubfoot to their children and suggested this finding indicates the less commonly affected sex carries a higher genetic load.41
Several studies have reported no significant relationship between sex and risk of clubfoot recurrence.23,25 However, in a 2014 study, Goldstein and colleagues found in a logistic regression analysis that female patients were 5.3 times more likely than male patients to need surgery for clubfoot recuurence.36
Race/ethnicity. There is clear variability in the prevalence of idiopathic clubfoot with respect to race/ethnicity. The prevalence of clubfoot in whites is 1 to 2 per 1000 live births, but there is a lower prevalence in Chinese of .39 per 1000 live births, and a higher prevalence in Pacific Islanders of 6.5 to 7 per 1000 live births.38 However, Dobbs and colleagues, looking at whites versus nonwhites, found no relationship between race and risk of recurrence.25 And, in a 2006 study of clubfoot patients in New Zealand, Haft found the high recurrence rate of 41% found in their study could not be attributed to the high proportion of clubfeet seen in patients of Polynesian descent.42
Age at initial visit. Although Ponseti recommended that manipulation be started as soon as possible after birth,27,30 various recommendations have been made regarding the upper limit of age at treatment initiation. Several authors have reported the Ponseti technique can be effective in treatment of idiopathic clubfoot in patients aged up to 9 years.43-45 And Morcuende et al reported no increased difficulty in obtaining correction of the deformity with the use of the Ponseti technique in children aged up to 2 years.20
Despite these reports, there is some controversy over whether older age at initiation of treatment is associated with an increased risk of deformity recurrence. Lehman and colleagues reported that patients whose treatments were initiated when they were older than 7 months appeared to have an increased probability of poor results.31 Abdelgawad similarly described that initiating treatment in infants older than 6 months was associated with a higher rate of early failure.18 However, multiple authors have described no significant association between age at initial visit and risk of recurrence.20,23,25,36,46
In a 2009 study, Alves and colleagues looked at 102 clubfeet and compared those beginning Ponseti treatment when older than 6 months with those younger than 6 months.46 They found no significant difference between the groups in the number of casts needed to achieve the initial correction, the rate of relapse, the need for posteromedial release, and the need for tibialis anterior tendon transfer during the follow-up period. In both groups, correction was achieved in all patients using the Ponseti method.
Previous treatment. Multiple studies have reported that idiopathic clubfoot deformities previously treated with nonoperative interventions respond well to Ponseti manipulation and casting.20,43,46 Similarly, no association has been found between previous nonoperative treatment and risk of recurrence after Ponseti treatment.25,36,47
Parental factors. A 2004 study by Dobbs et al examining risk factors for recurrence found that parental education at the high school level or below carried a tenfold increased risk of clubfoot recurrence after Ponseti treatment.25 However, they found no significant relationship between parental marital status or parental income and risk of relapse.25 Similarly, researchers haven’t found an association between the source of medical insurance and the risk of relapse.25,36
Initial classification. Numerous classification systems have been proposed to predict treatment course and outcomes of clubfoot deformity. Two of the more commonly used classification systems include the Catterall/Pirani system48,49 and the Dimeglio/ Bensahel system.50,51 Both systems identify key components of the deformity and assign a numerical score, and in both systems a higher score indicates more severe deformity. Both classification systems demonstrate excellent interobserver reliability after a short learning curve.52
Catterall’s system initially identified a group of feet in which a “limited posterior release” performed early was sufficient for complete correction of an idiopathic clubfoot, and the authors explained that “assessment of the fixed deformity may define indications for limited and radical releases.”48
Modifications by Pirani altered the classification system. In the system of Catterall/Pirani, the components of posterior crease, empty heel, rigid equinus, curvature of the lateral border, medial crease, and reducibility of the lateral head of the talus are each scored 0, .5, or 1. The first three components are summed to calculate a hindfoot contracture score and the other three components comprise the midfoot contracture score. Later studies found that the Catterall/Pirani score could be used to estimate the number of weekly casts required,53 and that the hindfoot score could be used to predict the need for tenotomy.53,54
Dimeglio described his classification system as allowing a better understanding of the type of feet that require extensive posteromedial release, conventional posteromedial release, or limited posterior release.51 He reported that the classification allows one to predict the impact of functional treatment, follow its progress, and establish the most beneficial surgical treatment.51 In the Dimeglio/ Bensahel scoring system, the components of dorsiflexion, hindfoot varus, midfoot rotation, and forefoot adduction are scored from 0 to 4. The components of posterior crease, medial crease, cavus, and abnormal underlying musculature are scored as present (1) or absent (0). In a comparison of the classification systems of Ponseti and Smoley, Harrold and Walker, and Catterall and Dimeglio, the Dimelgio system had the greatest reliability in clubfoot categorization.55
Multiple studies have attempted to utilize these scoring systems to predict outcomes and risk of recurrence.20,25,36,37,47,53,54 Most of these studies have found the initial severity classification is not related to treatment success, which may be because different feet respond differently to manipulation.20,30 Additionally, these studies have found that no correlation between initial severity and the number of casts needed for correction37 or the need for surgical intervention.47
Number of casts. Several authors have attempted to link the number of casts required for correction with the risk of recurrence after successful Ponseti treatment.20,25,37,42,47,54 While Dobbs found the more severe the initial deformity, the greater the number of casts required for correction,25 Morcuende reported the number of casts required for full correction was not a long-term prognostic factor for recurrence after treatment.20 However, other authors have found a significant difference in the number of casts required for those who eventually required a surgical intervention for clubfoot recurrence compared with those who did not.36,42,47
Brace wear. The one factor the literature consistently and inarguably demonstrates is associated with the risk of recurrence after successful treatment of idiopathic clubfoot is compliance with the FAO.18,20,23-25,36,42,46,47 In a study of risk factors for recurrence, Morcuende and colleagues found that noncompliance with the FAO was associated with a 17 times greater odds of relapse and that FAO noncompliance was the only studied parameter independently associated with recurrence.20 In patients who had completed serial casting, Dobbs found a 31% relapse rate when they were aged 6 months, and determined all of them had been noncompliant with the FAO.25 The risk of recurrence in FAO-noncompliant patients has been reported to be anywhere from six to 183 times that of FAO-compliant patients.20,25,36
Several authors have pointed out that FAO noncompliance may actually be brace intolerance.25,42 Parents not using the FAO in the prescribed manner may reflect a gradual inability to comfortably brace the foot as clubfoot recurrence is taking place. Despite this, currently available clubfoot scoring systems have failed to demonstrate a link between increased severity scores at initiation of FAO use and brace noncompliance.36,42 In studies of FAO compliance, parental education at a high school level or below was the only risk factor associated with FAO noncompliance.25 No significant relationships were noted between FAO noncompliance and source of medical insurance, parental income, parental marital status, family history, or ethnicity.25,42,56
While introduction of the Ponseti method has substantially reduced the number of surgical interventions required for treatment of idiopathic clubfoot, recurrence after successful treatment remains an issue. Numerous studies have explored factors that contribute to recurrence.
Ideally, factors that could identify patients at increased risk for recurrence at presentation would be beneficial in counseling parents about the expected course of treatment. However, at this time, FAO noncompliance or intolerance is the only reliable indicator of increased risk for recurrence. Parents need to be counseled about the importance of continuing with prescribed brace wear.
Rachel Y. Goldstein, MD, MPH, is an assistant professor of pediatric orthopaedics at Children’s Hospital Los Angeles in California.
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