Review Question - QID 218578

In cases of congenital femoral shortening (CFS), a thorough knee examination must be done preoperatively, as cruciate deficiency may place patient's at risk for knee subluxation/dislocation during the femoral lengthening process.

Congenital femoral shortening can create significant leg length discrepancy (LLD) for patients and create difficult with daily activities. Based on the degree of shortening shoe lifts, epiphysiodesis of the contralateral limb, physeal bar excision, or limb lengthening may be performed. Limb lengthening of long bones is typically recommended in cases of LLD >5 cm. Lengthening requires a stable joint above and below the long bone being lengthened. In cases of femoral lengthening, hip subluxation/dislocation may be noted if markers of preoperative dysplasia are not recognized. Similarly, knee subluxation/dislocation has been noted in cases of cruciate deficiency, so a good examination must be done preoperatively.

Sanpera et al. reviewed the role of the knee joint in patients with CFS. They note that as more effective lengthening techniques have evolved, the degree of lengthening has increased. They emphasize the importance of evaluation of the knee because of the described incidence of knee subluxation/dislocation.

Bowen et al. described factors placing patients with CFS at risk for hip subluxation/dislocation. They noted that severe acetabular dysplasia and coxa vara deformity contribute to hip subluxation/dislocation. They recommend correction of the varus femoral deformity and acetabular index prior to lengthening in those severe deformities.

Shabtai et al. review internal lengthening for congenital femoral deficiency and fibular hemimelia. In their study, indication for lengthening was only 2 cm LLD and the mean daily distraction was 1 mm/day. They concluded that this method of internal lengthening achieved accurate, controlled long bone lengthening with low rates of complication.

Figure A shows an AP full-length standing radiograph of the bilateral lower extremities demonstrating leg length discrepancy centered on the right femur.

Incorrect Answers:
Answer 1: Achilles contracture is not uncommon in patients with congenital femoral shortening, but it's presence does not increase the risk for post operative complication.
Answer 3: LLD >5 cm is an indication for femoral lengthening. LLD >20 cm may not be able to be reconstructed, but an 8 cm LLD is not, on its own, a risk factor for postoperative complication.
Answer 4: Hip center edge angle <20º may represent a risk factor for hip subluxation during femoral lengthening.
Answer 5: 1 mm/day is the recommended amount of femoral lengthening in order to promote distraction and new callus formation.