Treatment options for CFD are individualized for each patient. The principles include assessment of final leg length discrepancy at skeletal maturity, equalization of leg length, either by epiphysiodesis of the contralateral leg or lengthening via distraction osteogenesis or ablation. Important factors to consider prior to lengthening include decisions on whether to treat acetabular dysplasia, if present, whether to reconstruct the hip and proximal femur and whether surgery to address knee instability and patella mal-tracking is indicated.

Hip subluxation or dislocation is one of the most serious complications associated with femoral lengthening. The direction of dislocation is often posterior [6] Closed reduction under muscle relaxation may fail due to excessive soft tissue tension. Soft tissue releases alone may be unsuccessful and femoral shortening as well as acetabular procedures such as a Dega or Shelf may be required. Therefore it is better to identify those patients in whom there is an increased risk of dislocation in order to perform preparatory surgery to protect the hip from deterioration and allow adequate lengthening to be achieved. Suzuki et al. [7] reported no hip deterioration in patients with a centre edge angle of >20 degrees in a series of patients undergoing femoral lengthening for both acquired and congenital causes compared to a 25 % rate of deterioration in hip congruency in those patients with a CEA of 20 degrees or less. Bowen et al. [8] recommends an acetabular index of 25 degrees or less as well as correction of a neck shaft angle (NSA) to 120 degrees prior to lengthening of Kalamchi Type 3a femora [9].

The choice of osteotomy type to address acetabular dysplasia should take into consideration the location of the deficiency in CFD. Suzuki et al. [7] recommended an innominate osteotomy. Millis and Hall have described a trans-iliac lengthening which is a modification of the innominate osteotomy by use of a trapezoidal wedge which both re-orientates the acetabulum and can generate between 2 and 3 cm of length [10]. However the deficiency in the acetabulum is posterior and lateral. There is relative acetabular retroversion combined with decreased femoral anteversion. This may result in posterior uncoverage if an innominate osteotomy is performed, therefore theoretically promoting rather than preventing a posterior dislocation during lengthening or increase the probability of developing femoro-acetabular impingement [11]. Paley recommends performing a Dega osteotomy in such a way to reduce the superolateral deficiency whilst also providing approximately 1 cm of length. In those patients with a closed triradiate cartilage a reorientating osteotomy such as a Ganz periacetabular osteotomy can be performed however, care should be taken to correct lateral coverage and not anterolateral coverage.

Distal osteotomy sites allow for simultaneous correction of distal valgus deformity and lengthening from the same level. It also results in improved regenerate formation as the osteotomy is in the broad metaphyseal area of the bone. In addition it reduces the pressure on the hip, whilst increasing pressure on the knee joint. This can be counteracted by spanning the external fixator across the knee joint. In contrast proximal osteotomies exert less tension on the knee, but more on the hip [3]. There is a reduction in bone regenerate healing in proximal osteotomies as compared to distal osteotomies [12]. Aston et al. [13] reported improved range of knee movement in proximal osteotomies as compared to distal osteotomies with no statistically significant difference in the healing index. The fracture rate reported in their series is reviewed later in this chapter.

The knee in CFD is at risk of subluxation or dislocation during the lengthening phase due to the absence of either both cruciates or the anterior cruciate ligament alone [14]. During lengthening increased tension across the knee from the soft tissue structures can result in sagittal translation. Grill et al. [12] reported a 57 % incidence of knee dislocation or dislocation in patients with knee dysplasia. Gillespie and Torode [15] reported a maximum of 15–20 % increase in length of the femur before posterior subluxation of the knee occurred. Jones and Moseley [16] reported an incidence of posterior subluxation of 33 % when lengthening using the Wagner technique. In order to address this, extension of the external fixation across the knee joint can be performed. Aston et al. [13] spanned the knee in 26 out of 30 patients at the time of initial procedure and found it necessary to extend the frame across the knee in 2 of the remaining 4 patients. With careful identification of the centre of rotation of the knee joint a hinged extension can be extended across the knee, allowing for knee flexion and extension during physiotherapy. This may avoid the pitfalls associated with knee subluxation in lengthening. In a recent series one of 30 patients developed posterior subluxation only [17]. However it is difficult to determine whether knee stability in this series was conferred by a hinged external fixator, a preceding “Paley SUPERknee” procedure or more likely a combination of both.

Chomiak et al. [4] reported a level 1 diagnostic study of their arthroscopic findings of 21 patients with CFD. Only 1 patient in their series had normal cruciate ligaments. Ninety percent of patients had either an absent or hypoplastic ACL. The PCL was absent or hypoplastic in 61 % of patients. In 57 % of patients both the ACL and PCL were hypoplastic.

Prince et al. [17] reported a series of 30 cases of CFD, 24 of which (80 %) had undergone a SUPERhip procedure and 15 (63 %) had undergone a SUPERknee; however this paper was focused on outcomes following external fixation. No other series of SUPERhip or SUPERknee procedures could be identified in the literature.

Fracture of the femur following removal of an external fixation device poses a significant management problem. They can occur through bone regenerate, the junction between host bone and regenerate bone, though a half pin or at a site unrelated to the previous surgery [18]. They are difficult to treat because of tight soft tissue structures due to lengthening leading to a tendency for progressive angulation, an absence of an intramedullary canal at the osteotomy site, the pin sites may produce sclerotic areas which are a block to the passage of an intramedullary nail and there is a risk of sepsis or deep infection from prior pin sites. Prince et al. [17] reported a 7 % fracture rate of the regenerate after Rusch rodding after surgery. Aston et al. [13] performed rodding at the time of the index procedure and reported an overall 30 % rate of femur fracture. There was no difference in fracture rate between proximal and distal osteotomy sites in their study when comparing proximal osteotomy and simultaneous rodding with distal osteotomy and no rodding. The addition of rodding reduced their fracture rate in proximal osteotomies from 100 % without a nail to 0 % with a nail in their small subseries of 13 patients.

In patients in whom reconstructive surgery is not possible prosthetic fitting is required to resolve postural imbalance. Non surgical treatment involves the use of an extension prosthesis. However, these can be bulky due to the contour of the foot and an alternative surgical procedure is ablation of the foot by either a Syme’s amputation or a Boyd’s amputation with or without a knee fusion. Kant [19, 20] et al. compared Locomotor Index and overall satisfaction between 2 groups; those that had undergone Syme’s amputation and those that had an extension prosthesis and found higher levels of function and satisfaction in the non-surgical group 21. Rotationplasty as described by Van Ness and several modifications of the procedure involves a rotational osteotomy which replaces the knee with the ankle joint that has been externally rotated by 180° [21–24]. This allows for fitting of a below knee type prosthesis. Alman et al. [25] compared the results of Syme’s amputation with knee arthrodesis with rotationplasty and found no difference in gross motor function or perceived appearance, but increased energy efficiency in patients with a rotationplasty. Fowler et al. [26, 27] also found improved energy efficiency in rotationplasty patients compared to Syme’s patients, with more normal knee kinematics and enhanced prosthetic knee function in rotationplasty patients, provided the tibia had not derotated. Ackman et al. [28] examined the long term effects of rotationplasty to normal controls and found significant differences in gait and posture but no differences in health and well being.