Children born with developmental dysplasia of the hip (DDH) are often treated with a special device called the Pavlik harness. This canvas sling holds the child’s hips and knees bent with the legs spread apart. But there can be complications with this treatment. One of those complications is a nerve palsy. The extreme flexed position of the hip can put pressure on the femoral nerve that supplies the muscles along the front of the thigh.
Developmental dysplasia of the hip (DDH), previously known as congenital hip dysplasia is a common disorder affecting infants and young children. The change in name reflects the fact that DDH is a developmental process that occurs over time. It develops either in utero (in the uterus) or during the first year of life. It may or may not be present at birth.
In this condition there is a disruption in the normal relationship between the head of the femur (thigh bone) and the acetabulum (hip socket). DDH can affect one or both hips. It can be mild to severe. In mild cases called unstable hip dysplasia, the hip is in the joint but easily dislocated. More involved cases are partially dislocated or completely dislocated. A partial dislocation is called a subluxation.
The idea of the Pavlik harness is to get the round head of the femur in close contact with the hip socket. This position helps the hip form a deeper socket that is less likely to dislocate. Many studies have been done now to show that this nonoperative approach to the problem is quite successful.
But there are times when problems like nerve palsy develop. In this study from the Texas Scottish Rite Hospital for Children, the surgeons take a look back over records of the 1218 children treated at their clinic. All were treated with a Pavlik harness for developmental dysplasia of the hip. Anyone treated over a period of 17 years from 1992 to 2008 was included.
They found a total of 30 children who developed femoral nerve palsy during this time. By taking a closer look at the factors associated with these children and comparing them to a control group, they were able to gain a better understanding of what’s going on and why this happens. The control group was made up of children with developmental dysplasia of the hip treated with the Pavlik harness who did NOT develop a nerve palsy.
This is the first study to look at femoral nerve palsy linked with the Pavlik harness. Pediatric orthopedic surgeons have been aware of the problem but no one has really studied it to find out why it happens. And there have not been any studies to follow-up and report on the final results for children with this complication.
Data collected from the medical records included 1) how soon the nerve palsy developed after the child started wearing the harness, 2) body-mass index or BMI of the child (an indication of size and weight), 3) number of days until the palsy went away, and 4) success with the harness treatment.
They found that there was a 2.5 per cent incidence of femoral nerve palsy (that’s the 30 children out of the total 1218). Most of those (87 per cent) developed in the first week after starting use of the harness. The palsy group were older, larger (taller and heavier), and had more severe dysplasia.
And to give you some idea of how important this complication is — 97 per cent of the control group (children with dysplasia who did NOT develop nerve palsy) had a successful outcome using the harness. Only 47 per cent of the palsy group had successful results with the harness. Surgery to correct the problem was required instead.
There was one other important predictive factor in the final outcomes. The number of days it took for the nerve function to come back after taking off the harness made a difference. So for example, children who regained normal function in three days had a 70 to 76 per cent chance of success with the Pavlik harness once it was removed or adjusted to take pressure off the nerve.
But the longer it took to resolve the nerve palsy (measured at day seven and again after 10, 14, 21, and 28 days), the less likely the harness would work. In fact, any child who had not recovered within a month’s time had no chance of success with the harness. Fortunately, there were no cases of permanent nerve palsy. Temporary loss of muscle function from pressure on the nerve is called transient nerve palsy.
Findings as a result of information gathered from this study can be summarized as follows:
This study helps us understand why femoral nerve palsy develops with use of the Pavlik harness for developmental dysplasia of the hip. Future studies may be able to show ways to avoid this problem and improve the outcomes with harness use.