Several classifications exist for fibular hemimelia. The earliest published classification is the Coventry and Johnson [17] classification from 1952 (Fig. 23.2). They divided patients with FH into three types:

The Achterman and Kalamchi classification, from 1979 [18], is the most commonly used (Fig. 23.3). They divided the patients into two groups with one subdivision:

The Stanitski classification, from 2003 [19] (Fig. 23.4), is a morphologic description that divides FH into four categories based primarily on radiographic presentation:

Birch et al. [20] in 1998 presented a new classification system based on the clinical status of the foot and the magnitude of limb shortening as a percentage of the contralateral limb on radiographs in order to anticipate the extent of deformity at maturity and to recommend the appropriate treatment required (Fig. 23.5). In 2011, Birch later [5, 21] modified the treatment proposed: fewer amputations and more reconstruction procedures. Cases are divided into two categories:

A more recent classification proposed by Paley [16] is surgically oriented (reconstruction, not amputation) (Fig. 23.6). He classified FH into four types, based on the ankle pathology:

For Type 1, tibial lengthening is recommended, along with tendo Achilles lengthening. For Type 2, tibial lengthening is recommended, along with tendo Achilles lengthening and a supramalleolar reorientation osteotomy. For Type 3, soft tissue lengthening (peroneal tendons and tendo Achilles), resection of the fibrous anlage and interosseous membrane, and a reorientation osteotomy is recommended. This has been nicknamed the “Super-ankle procedure” and will be described later in the chapter. The osteotomy site varies according to whether the deformity is classified as Type 3a, 3b, 3c, or 3d. Type 3a needs a supramalleolar osteotomy, type 3b needs a subtalar osteotomy, Type 3c needs both supramalleolar and subtalar osteotomy, and Type 3d, which is very rare, may be treated with an opening wedge osteotomy of the body of the talus. Type 4 (clubfoot type) is treated initially by applying Ponseti casts and performing an Achilles tenotomy followed by a “Super-ankle procedure” at age 12–24 months. The casting treatment typically converts the foot position from equinovarus to equinovalgus, which can then be addressed with the Super-ankle procedure. While the more severe Type 3 cases should also be considered candidates for amputation, Paley’s classification is geared towards reconstruction, with the subtype designation dictating the specific reconstructive procedure.

In our practice, a patient with fibular hemimelia is usually seen during the first year of life. In less than one-third of cases, the diagnosis has already been made using prenatal ultrasonography [22]. During the initial visit, full-length standing anteroposterior (AP) and lateral view radiographs are obtained to evaluate the exact configuration of the skeletal anatomy of the lower legs, to determine the amount of LLD, and to look for concurrent deformities such as congenital femoral deficiency. The child’s height predication based on the long limb should be recorded. Based on the radiographic LLD (or the clinically measured LLD), the ultimate LLD at maturity can be predicted. We use the Multiplier Method [23, 24] to predict the ultimate LLD and ultimate overall height (based on the long leg) at skeletal maturity. This is easily done with the Multiplier mobile app (available for free on the Apple iTunes store for the Apple iOS platform and Google Play for the Android platform).

These two predictions (LLD and height) allow for formulation of a multistage treatment plan for the family. The family should leave the first visit with a clear picture of the pros and cons of the two main treatment arms: amputation versus reconstruction. Knowing the predicted adult height (based on the current length of the long leg) and the predicted LLD at skeletal maturity allows the surgeon to propose various treatment strategies. For example, if the Multiplier Method predicts an adult height for a boy to be 5′7″ (170 cm) with an LLD of 6 cm, then most families would choose limb lengthening as opposed to epiphysiodesis. However, if the same boy had a predicted height of 6′2″ (188 cm) with an LLD of 6 cm, then epiphysiodesis would become a more attractive option. For the reconstruction option, the family needs to be told if it will be necessary to perform foot/ankle reconstruction and how many lengthening procedures are anticipated. External fixation is the mainstay of lengthening in young children with FH [21]. In skeletally mature patients, it is possible to use the newer magnetic telescopic intramedullary (IM) nails for tibial lengthening [25, 26]. Combinations of lengthening and epiphysiodesis can also be done to minimize the number of lengthening procedures required.

The initial clinical exam should include a complete orthopedic examination of the child to look for associated anomalies. In the lower extremity, the number of rays and position of the foot and ankle are noted. Specifically, the ankle is examined to determine if it is mobile and well aligned or contracted into equinovalgus or equinovarus. The range of motion and stability of the hip, knee, and ankle are assessed. The knee joint is often somewhat unstable (ACL or PCL deficiency) and may be in excessive valgus alignment.

If the involvement of the hip and knee is severe (as in combined FH and congenital femoral deficiency), then the overall reconstruction plan is either concurrent hip/knee reconstruction or sequential reconstruction. Most commonly, the significantly involved hip and knee would be addressed first between the ages of 18 and 24 months (this is discussed at length in Chap. 22). The ankle reconstruction would then typically occur 6–12 months after the hip and knee reconstruction, although in some cases, it may be feasible to perform simultaneous hip, knee, and ankle reconstruction (Super-hip, Super-knee, and Super-ankle procedures).

Even if the femur is not involved or minimally involved, there still may be instability of the knee due to an absent ACL. In such cases, the preoperative full-length standing lateral view radiograph shows anterior subluxation of the tibia on the femur (Fig. 23.8). Consideration should be given to perform an intra-articular ACL substitution procedure prior to tibial lengthening. If the PCL is also deficient, then an extra-articular PCL reconstruction should be performed at the same time.

The initial radiographic assessment should include plain films: full-length standing AP view radiograph depicting both legs with a lift under the short leg (Fig. 23.7) and a full-length standing lateral view of the affected leg with the knee in maximum extension (Fig. 23.8). The typical appearance in severe cases is a mild valgus deformity of the knee secondary to a hypoplastic lateral femoral condyle. This creates a mechanical lateral distal femoral angle (mLDFA) of less than 85°. Additional valgus may come from an apex anteromedial bow in the tibia. A dimple on the skin is usually visible over the apex of this bow (Fig. 23.9). A lateral view radiograph of the foot may show overlap of the talus and calcaneus or a talo-calcaneal tarsal coalition. If the talus and calcaneus are on top of one another, the ankle valgus is typically from a tilt in the distal tibial plafond. The talus and calcaneus may be stacked on top of each other on the lateral view, which points toward the ankle as the source of valgus (Fig. 23.10). If the talus and calcaneus are overlapped on the lateral view (Fig. 23.11) or side by side on the AP ankle (Fig. 23.12) view giving the appearance of a “double barrel shot gun,” then the valgus component is more likely subtalar in origin. Most patients with FH have a talo-calcaneal coalition, which may not be evident on the initial radiographs obtained during infancy (Figs. 23.13 and 23.14) but become more obvious as the coalition ossifies with age.

In addition to plain films for cases of Paley Type 3 FH, it can be useful to obtain a magnetic resonance imaging (MRI) evaluation of the foot and ankle just prior to performing the Super-ankle procedure. Since much of the hindfoot and distal tibia is unossified during the first 2 years of life, it can be difficult to accurately classify the exact Paley Type 3 subtype. In such cases, an MRI can help differentiate between Type 3a, b, and c, thus allowing better preoperative planning (Figs. 23.15 and 23.16). Also, during surgery an arthrogram of the ankle joint can help delineate the valgus orientation at the ankle joint (Fig. 23.17).

One must understand that the initial reconstruction is a very complex set of procedures that is unique for each child. The deformity related to fibular hemimelia is the combination of contracted soft tissues and abnormally formed joints of the ankle and foot. The treatment of FH should address several issues such as limb shortening, lower leg deformity, and an abnormally positioned foot with or without absence of lateral rays. The goals of treatment are to create a lower limb with a stable hip, knee, and ankle by:

In many of the more severe cases, it may not be possible to improve the limited ankle mobility. Furthermore, the treatment itself (multiple lengthening procedures or Super-ankle reconstruction plus multiple lengthening procedures) may result in further loss of ankle motion compared to the amount present initially. The success of reconstruction is not necessarily determined by the final ankle motion. The amount of final ankle motion is usually predetermined by the amount of motion initially present at the ankle joint.

The amount of LLD predicted by the end of growth does not necessarily determine whether a successful reconstruction is possible. There are potentially no set limits to the amount of overall lengthening that can be performed, especially when divided into small steps of approximately 5 cm for each treatment. However, the overall predicted LLD does help when estimating the number of lengthening treatments that will be needed to equalize the limb lengths before skeletal maturity. Dividing the amount of lengthening into smaller amounts might be less traumatic for the muscles, nerves, and adjacent joints than trying to perform a heroic lengthening during one treatment. For example, if the predicted discrepancy is 15 cm, this may be better addressed with three 5-cm lengthening treatments instead of two 7.5-cm lengthening treatments. Better yet, two 5-cm lengthening treatments combined with one 5-cm epiphysiodesis may yield the optimum outcome.