A distinct characteristic of juvenile hallux valgus is congruent joints [8]. Piggott in his adult series noted <10% had a congruent metatarsophalangeal joint [41]. However, later studies revealed 47–68% of juveniles with hallux valgus had congruent joints [7, 52]. Hardy and Clapham coined the term “critical angle of hallux valgus” or the point at which the hallux abuts the second toe, pushing the first metatarsal into varus [23]. The intermetatarsal angle was found to be stable until this point, at which the intermetatarsal and hallux abductus angles increased more rapidly [31].

Plain radiography of the deformity will aid in deciding corrective procedures as well as detecting coexisting abnormalities. Dorsoplantar, lateral, and sesamoid axial X-rays will project all three cardinal planes for evaluation. Commonly evaluated are the intermetatarsal, hallux abductus, and distal metatarsal articular angles, sesamoid position, and metatarsal length. An increased distal metatarsal articular angle (DMAA) may be the defining characteristic of juvenile hallux abductovalgus [8, 9]. Early recognition of an increased distal metatarsal articular angle will aid in avoiding excessive lateral tilt after bunion repair [52]. A relatively high distal metatarsal articular angle occurs with concomitant metadductus [20, 52]. Normal values for distal metatarsal articular angle are 8° or less [4, 20, 37, 46]. Interestingly, the literature shows much variability when measuring the distal metatarsal articular angle. Vittetoe et al. observed that 1 out of 20 times measurements of the angle would be off more than 5° [51]. Amarnek et al. found preoperative measurements averaged 7° below the intraoperative value and recommended distal metatarsal articular angle be determined intraoperatively [1]. The distal first metatarsal articular angle is considered to be one of the main intrinsic factors responsible for the early onset, hereditable nature, and severity of the hallux valgus deformities in juveniles [39].

Metatarsus primus adductus is a significant radiographic deformity in hallux valgus and may exaggerate the bunion deformity [2]. The metatarsus adductus angle is the line bisecting the second metatarsal and the longitudinal line bisection of the lesser tarsus on standard weight-bearing dorsoplantar radiographs [14]. Engel determined a metatarsus adductus angle greater than 21° is abnormal [12]. Though some authors believe the increase in intermetatarsal angle is a result and not a cause of hallux valgus, obtaining the true intermetatarsal angle is important in the presence of metatarsus adductus. This is defined as the sum of the intermetatarsal and metatarsus adductus angles and subtracting 15° [11] (Fig. 15.5).

The presence of a long first metatarsal has been indicated in the development of juvenile hallux valgus [37]. Hardy and Clapham observed differences in protrusion distances compared to controls and concluded that subjects with a long first metatarsal are likely to develop hallux valgus [23]. Coughlin noted the preoperative hallux valgus angle averaged 5° more with a long first metatarsal, but it did not directly increase the risk for postoperative recurrence [7]. A hallux abductus angle greater than 15° is considered pathologic [23, 37]. The authors do not believe that long and short first metatarsals exist in cases of feet without previous trauma or surgery except in cases of brachymetatarsals. Often when short and long first metatarsals are discussed, it is the given position of a snapshot view of the first metatarsal. At the time of the radiograph, one needs to ask was the patient full weight bearing, was the patient fully loaded on their foot, was the angle and base of gait accurate, and did the X-ray technician have the appropriate angle at the time of the X-ray? It has been the experience of the authors that when a first metatarsal appears long on an AP X-ray, the metatarsal is elevated or more parallel to the ground (often seen with a flatfoot deformity). When it appears short, the first metatarsal is positioned more in a plantar-flexed position (often seen with a cavus foot) (Fig. 15.6).

In an extensive review by Ferrari et al., a sexual dimorphism was observed, predominantly proving male bones and joints were larger than females [13]. Articular surface measurements suggested high potential for adductory movement in females, which could produce a more adducted first metatarsal than in males [13]. Women also demonstrated greater curvature in the first metatarsal head, which is related significantly to the degree of hallux valgus. This allows for decreased stability at the metatarsophalangeal joint and increased abduction of the proximal phalanx. Ferrari reported that if an abductory force were equal between men and women, the female hallux would buckle more easily than in men. Females are known to be more flexible than males and may lead to greater hallux valgus deformity [14]. This hypermobility is may be due to ligament laxity, but the joint laxity may precede soft tissue influence. The talar head also had larger functional angles in females in which greater motion can occur. Both the first metatarsal head curvature and talar functional angle in females are postulated to increase occurrence of hallux valgus [13]. A full clinical and radiographic assessment including rearfoot deformities or triplanar abnormalities must be considered to determine effective treatment options.

Though controversial , nonsurgical measures may not be helpful in moderate-severe juvenile hallux valgus with progressive deformity. A prospective trial of foot orthoses for juvenile hallux valgus questioned the role of pronation as a causative factor in juvenile hallux valgus [37]. Kilmartin et al. found that orthoses should not be used to treat juvenile hallux valgus as they appear to increase the rate of deformity progression. Interestingly, several of the contralateral normal feet developed hallux valgus despite orthotic use. Hallux valgus increases in children regardless of whether they wear biomechanical orthoses or well-fitting shoes [29]. However, nonsurgical treatment may be amenable in patients with neuromuscular disorders, ligamentous laxity, or inability to remain non-weight bearing (Groiso). Non-operative treatment options that include wider shoe gear, bunion pads, orthotics, and bracing may relieve symptoms of deformities that are mild, minimally painful, and flexible. Although the patient population is generally not compliant with these modalities, they should be attempted given the high rate of recurrence from surgery and are effective in treating other compounding deformities like metatarsus adductus, pesplanovalgus, and equinus [21].

Surgery should be discussed when conservative measures have failed or when these measures are determined to be unlikely to be effective. Additionally rapid progression of the deformity with visible joint adaptation is a reasonable indication for correction in younger patients. The goals of surgery are to relieve pain, restore function, prevent worsening deformity, and improve cosmesis . Value of these factors should be placed in this order. If cosmesis is the main focus, reassessment should be performed and directed toward conservative measures given the high rate of recurrence [53].

Several important factors must be evaluated in the preoperative period . These include the patients’ age, growth plate status, coexisting deformity, progression of deformity, family history, functional impairment, and expectations. Severe impairment with pain and dysfunction and progression of the deformity despite conservative measures are clear indications for surgical correction.

Ideal timing for surgical correction is between the ages of 11 and 15 years as the patient approaches skeletal maturity. It is important that growth plates should be closed to allow procedures that can produce optimum deformity correction.

Surgical correction options are vast and include head procedures, base procedures, soft tissue procedures, epiphysiodesis, and first metatarsocuneiform fusion. The decision as to which procedure or procedures is warranted depends on several factors: the severity of the deformity, correction needed, growth plate status, and patients’ capacity. Frequently, definitive surgical planning doesn’t finish until intraoperative evaluation can be performed of the articular surface of the first metatarsophalangeal joint [41]. Soft tissue procedures are generally insufficient in treating the deformity successfully. It is this authors’ approach to not violate the joint unless completely necessary to avoid potential risks of AVN, arthritis, or adhesions. The exception of any abnormal soft tissue contractures contributing to the deformity should be addressed.

Distal metatarsal osteotomies are typically performed on juveniles with only mild to moderate deformity. The most commonly used are the Austin, Kalish, and Reverdin along with its various modifications [6]. The Reverdin and its modifications are especially useful given its ability to not only correct the IM but also for PASA correction [3]. Given this flexibility, it is often combined with more proximal procedures for patients with severe deformity where there have been adaptive changes to the metatarsal head. In these cases, the proximal osteotomy is performed first, followed by the distal procedure to assure proper alignment of the articular surface and joint function. Relocating the sesamoid apparatus beneath the metatarsal head and aligning the FHL restore normal sagittal plane motion of the first MPJ decreasing long-term arthritis risk [22, 45].