Children's Orthopaedics
Even today with different types of screening there are patients with developmental dysplasia of the hip (DDH) being diagnosed in walking ages of three or four years or even older. The oldest patient in my control group was a girl aged seven years and ten months.
Late diagnosis can be explained by the presence of only minimal clinical symptoms like no or a very mild limp, no limitation of range of movement or no pain. These patients are usually diagnosed by radiograph because of minor trauma or pain after exercise.
On radiograph there is usually acetabular dysplasia with subluxation of the femoral head and because of the long duration of subluxation, a deformity of the acetabulum called the bipartite acetabulum can be seen. This is a recently described deformity. The original acetabulum is divided into an inner and outer part, separated by border-like edge. The inner part is not in contact with the femoral head and is usually filled with fat tissue. The outer part is in contact with the femoral head providing it with stability, therefore there is negative Trendelenburg sign and no or mild limp. The outer part has an upper border labrum, very often deformed, and a reflected head of rectus muscle. This is the main difference between the bipartite acetabulum and the false acetabulum, which is located above the labrum and the reflected head of rectus muscle.
To acknowledge the existence of this deformity is very important for the surgeon. In the literature, there is a 30% rate of failure for all types of conventional pelvic and femoral osteotomies. There are two possible causes for this failure. First, the surgeon considers the outer part as the whole acetabulum and misinterprets the border-like edge as the incisura acetabuli. The white colour of hyaline cartilage of the outer part is in contrast with the dark colour of the inner part, which is usually filled with soft tissue. Secondly, failure to reshape the bipartite acetabulum leads to slipping of the reduced head back to the outer part of the acetabulum, resulting in persistent subluxation.
For reshaping of the bipartite acetabulum and correction of the dysplasia at the same time, a new type of combined pelvic osteotomy was developed1, in which Lance acetabuloplasty is combined with a Salter or Pemberton procedure, depending on the AC angle of the inner part of the acetabulum, later being indicated in severe dysplasia.
Dr Milan Rejholec, Consultant Orthopaedic Surgeon, Ministry of Health, Kuwait and Associate Professor, 1st Medical Faculty, Prague, Czech Republic
Reference
1. Rejholec M. Combined pelvic osteotomy for the bipartite acetabulum in late developmental dysplasia of the hip: a ten-year prospective study. J Bone Joint Surg [Br] 2011;93-B:257-261.
