Weinstein Lovell and Winters Pediatric Orthopaedics 7e

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CHAPTER 30  |  The Child with a Limb Deficiency

Fixation at the fusion site is often a rigid intramedullary rod inserted from the proximal femur across the fusion site into the distal segment, with an additional K-wire across the fusion site to give the construct rotational stability. The patella may or may not be excised during fusion. If it is excised, the bone can be used as graft at the fusion site. There have been a few cases reported of late-onset patellofemoral pain and arthritis on radiographs in PFFD patients with knee fusions and retained patellae (172). After surgery, limb stability is enhanced with a spica cast. The patient is usually ready for prosthetic fitting in 6 weeks and for ambulation as soon as the prosthesis is ready. Amputation of the Foot.  With the knee fused, ablation of the foot is desirable in most situations. One reason is to ensure the residual limb will be short enough to accommodate an internal knee joint when the child is older. The other reason is that it becomes increasingly difficult to fit the growing foot in a cosmetically acceptable socket. Whether or not a Boyd or Syme amputation is performed is largely surgeon dependent, and the relative merits of each procedure have been previously discussed. Van Nes Rotationplasty.  In the Van Nes rotationplasty, the limb is rotated 180 degrees, predominantly through the knee arthrodesis, with some additional rotation through the tibia if necessary. The goal is to have the ankle/hindfoot complex of the short limb at the level of the knee on the long limb at maturity. The foot now functions like the residual tibia in a below-knee ­amputation, thereby allowing the patient to func- tion more like a BK amputee than one with a knee disarticula- tion (Figs. 30-35A–D). Sufficient ankle and hindfoot flexion and extension, as well as ankle stability and alignment, are nec- essary for this type of treatment. The rotationplasty was first described in 1930 by Borggreve (173), for acquired traumatic limb-length discrep- ancy. Van Nes (174) later used the procedure for three cases of congenital deficiency of the femur. Initial reports of rota- tionplasty for treatment of PFFD by Kostuik et al. (175) and Torode and Gillespie (176) have been followed by more recent reports by Friscia et al. (177) and Alman et al. (178). The main complication of the procedure is either failure to achieve sufficient rotation at surgery or subsequent derota- tion with growth. Kostuik et al. (175) recommended waiting to perform the surgery until the child was older. However, this prevents the child from deriving the gait benefits for several years. Subsequent reports have not found this to be so great a problem. Also, derotation can be treated with revision surgery. Even though the functional results of the surgery are superior to that of an above-knee prosthesis wearer, parents and physicians are sometimes reluctant to perform it because of the cosmetic appearance of the foot pointing backward. It appears, however, that this problem is overrated by ­medical staff, ­compared to the patients themselves. Alman et al. (178) found no difference in the perceived physical ­appearance of children treated with rotationplasty, compared to knee

FIGURE 30-34.  An AP standing lower extremity radiograph of a patient with PFFD after knee fusion. Neither the distal femoral or prox- imal tibial epiphyses were removed at the time of fusion, resulting in a residual limb that falls below the contralateral knee. Coupled with the length required to fit a prosthetic knee joint (typically >7.5 cm), this will result in a residual limb that is significantly too long for the patient. Removal of the distal femoral epiphysis and physis at the time of knee fusion is indicated except when the residual femur is extremely short and the tibia is significantly short as well. usually give enough limb length for successful prosthetic fit- ting. Any additional length contributed by the femur is unnec- essary and interferes with accommodating the knee joint in the prosthesis. The author’s experience is that, in considering patients with PFFD with or without fibular hemimelia, 90% of children had at least 90% of the normal length of the tibial segment. In the children where this was true, patients at the time of knee fusion underwent excision of both distal femoral and proximal tibial epiphyses and physes, and no residual limb was too short to successfully fit with an above-knee prosthesis. In some cases, with more ­pronounced tibial and femoral short- ening, it may be advisable to remove neither or one epiphysis and physis (171). Calculation of the anticipated length of both limbs at maturity by means of the Green-Anderson growth charts (Tables 30.2 and 30.3), as described earlier, will help with the answer.