Tibial deficiency is classified into 4 types1-3:
- Type 1: complete lack of the tibia with either a nonfunctional knee (type 1a) or a functional knee (type 1b).
- Type 2: proximal tibia is present.
- Type 3: distal tibia is present.
- Type 4: short tibia with distal tibiofibular diastasis.
Both autosomal dominant and recessive patterns of inheritance have been proposed.2 Bilateral tibial hemimelia has also been associated with CHARGE syndrome and Langer-Giedion syndrome and may be linked to several loci on chromosome 8.4,5
One study of 4 patients with tibial hemimelia whose limbs (5 in total) were dissected showed that although all the limbs had the same external clubfoot-like appearance with marked supination, the internal anatomy differed. 2 Three of the limbs had a flexor hallucis longus, whereas the other 2 lacked a discrete tendon that could be followed back to a discrete muscle belly. None of the dissected limbs had an identifiable anterior tibial and posterior tibial muscle belly. The "posterior tibial" neurovascular bundle and medial tendons were found to act as a tether that kept the foot locked in supination, as seen in this patient. Multiple abnormal combinations and unions of bones were found in the attached feet.2
Because of the differences in presentation and anatomy, there is no agreed-upon treatment method for this deformity. However, knee disarticulation with early prosthetic fitting seems to be the most commonly performed procedure. Some surgeons do not approve of complete knee disarticulation because of stump complications and delays in independent postoperative ambulation. 3 One study reported independent walking in a 5-year-old patient with bilateral tibial deficiency just 15 weeks after he underwent a transtibial amputation with a plantar flap.3 The time to independent ambulation after knee disarticulation can be more than 16 months.
For all children with restricted ambulation, optimal mobility is essential to help them achieve independence and improve their health and quality of life.6