In his 1966 discussion of the condition that would later bear his name, Walter P. Blount describes osteochondrosis deformans tibiae, an epiphyseal and metaphyseal lesion of the proximal tibia, “similar to infantile coxa vara that appears soon after 1 year of age (occasionally shortly before adolescence) and causes internal torsion and angulation into bowleg.”1 After discussing potential etiology, radiographic findings, relevant differential diagnoses, and distinction of infantile from adolescent disease, Blount provides guidelines for treatment, based on Langenskiold’s staging system.2 Blount advises: “Slight overcorrection by efficient bracing in stages I and II of the forces that exaggerate the deformity or by operation in stages I to IV will completely cure the patient … Extreme deformity at any age requires immediate osteotomy to correct the angular and rotational elements … When there is an arrest of growth of the proximal tibial epiphysis medially, do a simultaneous epiphysiodesis of the lateral tibial and proximal fibular epiphyses, and a similar procedure, arrest of the proximal tibial and fibular epiphyses, on the opposite leg.”1
In the 50 years that have since passed, our treatment approach has evolved from this essential foundation. Here, we present an update to the management of infantile Blount disease, focusing on the last decade of literature.
Consensus has yet to be reached regarding the efficacy of bracing. Previously described factors predisposing to failure of conservative treatment include obesity (with weight>90th percentile), varus thrust, age (>3 y at treatment initiation), bilateral involvement, and severe disease (≥Langenskiold III).3 The most conservative approach—expectant management, entailing routine clinical and radiographic examination—may be just as viable an option for patients with mild disease.3 Studies4,5 have demonstrated considerable rates of spontaneous resolution of disease staged ≤Langenskiold III, indicating that patients successfully treated with orthoses may have had similar outcomes without bracing.
In 2012, Alsancak et al6 found that single medial metal upright knee-ankle-foot orthoses (KAFOs) with drop lock hinges at the knee provide effective treatment to patients, up to 38 months old, presenting with Langenskiold stage II disease. In a retrospective case comparison of different types of KAFO, a style incorporating a medial discus “pressure pad” and rigid column (n=6) provided the most rapid correction (10.6±2.3 wk).6 Patient satisfaction, encompassing parameters such as usage rate, ease of wear and removal, and comfort, was highest among patients treated with plastic KAFO.6 Given the limitations of small, uncontrolled, retrospective case series, set atop the background of high rates of spontaneous resolution, the jury is still out on nonoperative treatment of infantile Blount disease.
Application of lateral tibial hemiepiphysiodesis to guide the growth of adolescents afflicted with Blount disease was previously described in a 1992 case series.7 Stevens reported success in growth modulation using a nonlocking 2-hole plate and screws placed extraperiosteally, a technique relying on the tension band principle, in a prospective series of 34 consecutive patients afflicted with angular deformities secondary to a variety of etiologies, including Blount disease.8 A later retrospective chart and radiographic review found an 89% (16 of 18 limbs, in 12 children) rate of success, defined as “full mechanical axis normalization,” in manipulating the growth of infantile Blount patients by lateral proximal tibial tension band plates (TBPs).9 Of note, follow-up ranged from 0 to 37 months after plate removal; a third (6/18) of the operated limbs underwent additional plating of the lateral distal femoral physis; and, based on the age at surgery, none of the patients had achieved skeletal maturity. Given the absence of presented data on joint orientation angles (eg, lateral distal femoral angle), possibility of physiological varus and the rare occurrence of distal femoral varus in children with infantile Blount disease10, the role of guided growth in the distal femur for these young patients remains questionable.
A notable complication in guided growth with TBP, screw breakage, contributes to cases of delayed and failed correction.9 Scott9 implies that these cannulated screws may also predispose to hematoma formation and subsequent wound dehiscence and infection. Stitgen et al11 found that failure of the TBP construct occurs at the screw shaft. This finding resonates in vivo, as demonstrated by a 2007 survey of 841 POSNA members; cannulated screws accounted for every case of mechanical failure of guided growth (65 in total), never the plate itself.12 Blount patients with higher body weight may exhibit higher rates of mechanical failure.12,13 Schroerlucke et al13 observed a 44% failure rate among Blount patients undergoing guided growth, with mean time to failure of 13.6 months postimplantation; all failures occurred due to break of the tibial metaphyseal screw.
In Stitgen et al’s11 biomechanical study, they found solid, stainless-steel screws were significantly stronger than cannulated titanium screws in both devices tested (Orthofix 8-plate and Biomet Peanut plate). Herzenberg and colleagues elaborate on the replacement of cannulated screws with solid screws in TBPs in a case series that includes 4 patients with Blount disease.14 By using a cannulated screw to tap the solid screw’s trajectory over a guidewire (as opposed to drilling the full trajectory with a 3.2 mm drill bit), they claim to create a clear channel without compromising screw purchase into cancellous bone.
Considering the association of obesity with precocious puberty, the 26-month mean advancement in bone age found among patients with infantile Blount disease must be taken into account during preoperative planning, as premature physeal closure may cause undercorrection.15 In contrast, given the tendency for “rebound” growth to cause recurrent varus deformity after plate removal (for patients in reversible stages of disease), we typically remove the TBP after slight overcorrection into valgus (zone 2)3,16 (Fig. 1). If varus deformity does recur in a patient with remaining growth potential in the proximal medial tibial physis, the lateral TBP may be reinserted. Alternatively, one may remove the metaphyseal screw only (leaving behind a “sleeper” plate), reinserting the metaphyseal screw percutaneously if varus deformity recurs.17 Given the unpredictability of growth in the “sick” physis of the proximal tibia, it is critical to follow these patients to skeletal maturity.18 Looking forward, clinicians should study the efficacy of anterior TBP placement across the proximal lateral tibial physis to also address the sagittal (procurvatum) and axial plane (internal tibial torsion) components of this complex oblique plane deformity.
Metaphyseal osteotomy remains a foundational treatment option for children over 3 years old, with disease severity≥Langenskiold III. In the last decade, there is scant literature regarding proximal tibial osteotomies for infantile Blount disease. Although there is no consensus as to whether acute versus gradual deformity correction is superior19, decision-making should be individualized, based on patient and physician factors including magnitude of ipsilateral limb shortening, ability of the patient and caretakers to handle an external fixator, and experience of the surgeon (Fig. 2). As demonstrated in a systematic review of the literature21, 122 of the 18 case series included provided evidence in the favor of gradual correction with a circular external fixator, on the basis of accuracy of deformity correction, whereas the other studies were inconclusive. However, accuracy of correction is only one of several variables, including patient comfort, risk of neurovascular injury and compartment syndrome, and the ability to simultaneously address limb shortening, that the surgeon should consider when deciding between correction modalities.
In his discussion of osteotomy, Blount states, “overcorrection … into physiologic knock-knee will usually result in a cure; incomplete correction tends to progressive recurrence.”1 Although often true, surgeons should heed the mantra of valgus overcorrection with caution, especially in older children with infantile Blount disease, given the finding of advanced bone age in children with Blount disease.15
A variant of the osteotomy, medial hemiplateau elevation addresses the proximal medial tibial “depression”—often attributable to a hypertrophic meniscus (the magnitude of which correlates with patient body mass index23) and unossified epiphysis. The structures resulting from compensatory intra-articular morphometric changes may lack the necessary mechanical strength to withstand the forces encountered at the proximal tibia, especially in the older child. In addition, these children may have iatrogenic translational deformity in the proximal tibial metaphysis from previous proximal tibial osteotomies. Preoperatively, the surgeon must aggregate physical findings (such as presence of a varus thrust during walking) and radiographic analysis (including preoperative advanced imaging and intraoperative arthrography) to determine the contribution of epiphyseal versus metaphyseal deformity to the varus malorientation of the tibia. The epiphyseal deformity in these children, usually above 7 years old, may be corrected by a crescentic epimetaphyseal osteotomy of the medial proximal tibia extending into the intercondylar notch, followed by structural graft placement in the space created beneath the elevated articular fragment, and fixation (either internal or external)24,25 (Fig. 3). Surgeons may elect to augment this procedure with a second osteotomy, distal to the tibial tubercle, if metaphyseal-diaphyseal varus deformity warrants correction.24
McCarthy et al26 describe a 1-stage acute medial plateau elevation with concurrent gradual tibial metaphyseal osteotomy for patients with severe Blount disease, finding overall satisfactory correction, apart from 5 cases of undercorrection at the metaphyseal level. Fitoussi et al27 present a similar combined technique. During the medial plateau elevation, a proximal lateral tibial hemiepiphysiodesis should be performed concurrently, to avoid recurrent varus deformity. These complex procedures are not without complications, including premature consolidation, peroneal nerve palsy, infection (superficial and deep), and pain.26,27 The risk of postoperative compartment syndrome can be diminished by performing a prophylactic anterior compartment fasciotomy.3 As we strive to progress in treatment efficacy and reduce complications, standardized classification schema, such as the one Cherkashin presents for external fixator-mediated gradual correction in children with Blount disease, may provide better comparability across studies.28
Although we have begun to demarcate the characteristics of infantile Blount patients from those of their adolescent counterparts,29 work remains to be done in optimizing their treatment. Much of the extant literature lacks granularity. By providing more comprehensive information on a patient level, future investigators may better facilitate pooled analyses. This includes consistent presentation of clinically pertinent data, such as patients’ chronologic and skeletal age at treatment, intra-articular findings on advanced imaging, such as magnetic resonance imaging,23 and comprehensive multiplanar deformity analysis10—preoperatively, and in early and late follow-up. We should strive to follow patients to skeletal maturity,18 at least providing their status at last follow-up, and address specific complications encountered along the course of their treatment28 (Fig. 3).
The definition of “success” when treating a child with infantile Blount disease remains subjective and requires consensus building. For instance, if a child achieved satisfactory limb alignment following guided growth treatment, and subsequently required reimplantation of the TBP for recurrent deformity, while avoiding the need for an osteotomy, is that a success or a failure? Professional societies, such as the Pediatric Orthopaedic Society of North America (POSNA), European Pediatric Orthopaedic Society (EPOS), and the Limb Lengthening and Reconstruction Society (LLRS), may provide a collaborative platform to facilitate multicenter studies, standardize data collection, and, ultimately, address these open questions in the realm of Blount disease treatment.
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