Habitual dislocation of patella in knee disarticulation stump in a patient of congenital type I deficiency of tibia: a case report.

The objective of this case report was to describe a patient who developed habitual dislocation of patella after knee disarticulation. Congenital deficiency of the tibia (tibial hemimelia, aplasia or dysplasia) is very rare, with an incidence of approximately 1 per 1 million live births. Knee disarticulation is preferred over transfemoral amputation for type I tibial deficiency. Most of the surgical techniques describe preservation of the patella and suturing of patellar tendon with cruciate ligaments. We present a case of a 14-year-old girl, who underwent disarticulation through the right knee as a primary procedure at age of 5 months for congenital type I tibia deficiency. At 13 years after the primary procedure, the patient developed painful flicking of the patella, which was diagnosed clinically as habitual (spontaneous) dislocation of the patella. In conclusion, type I tibia deficiency is associated with marked hypoplasia of the distal femur along with retardation of ossification of distal femoral epiphysis. This can later result in patellar dislocation. This could delay the rehabilitation of young amputees with knee disarticulation. It would be debatable and would need further evidence as to whether excision of the patella at the initial amputation may be more appropriate to prevent later incidence of dislocation.