In this Level-II study, the authors present a very large series of patients with hip subluxation due to cerebral palsy who were treated with soft-tissue releases. The surgery consisted of adductor lengthening, often combined with iliopsoas lengthening and phenol injection around the anterior branch of the obturator nerve. The authors defined failure of the treatment as either the need for further surgery or progression of the migration percentage beyond 50%. In 330 patients with a mean follow-up of 7.1 years, the Gross Motor Function Classification System (GMFCS) and the initial migration percentage were the best predictors of long-term success or failure. Their results are sobering: in the 242 patients who were classified as GMFCS level IV or V, the success rates were only 27% and 14%, respectively.
This appears to be the first large study to examine the GMFCS classification as a predictor of success of soft-tissue hip surgery in patients with cerebral palsy. To be fair, if one considers level-IV and V patients as “quadriplegic,” or nonambulatory, then previous studies have found similarly poor outcomes1. However, those previous studies had a much smaller sample size. The size of this study is impressive. This is one of the largest series ever published to look at the success rate of soft-tissue release in such patients. Only twelve patients failed to meet the criteria for follow-up. The authors’ data make a convincing case that soft-tissue lengthening alone will rarely represent the final procedure in these nonambulatory patients. This is very important information to share with the family when doing preoperative counseling. Parents are often disappointed when soft-tissue procedures “don't work” and the patient ultimately requires a femoral and/or pelvic osteotomy. This paper helps to define more realistic expectations.
The strengths of the paper are the large number of patients, the lengthy follow-up, and the dropout rate of <4%. The mean age at surgery was 4.2 years, when soft-tissue procedures are typically expected to have a good chance of success. The authors acknowledge that the soft-tissue procedures were not performed uniformly. This is not unexpected in a retrospective review, and it should not be considered a major flaw. It reflects what is done in clinical practice: the amount of soft-tissue lengthening reflects the degree of contracture found at the time of surgery.
The role and timing of isolated soft-tissue release in patients with hip subluxation due to cerebral palsy have long been controversial. Some studies have suggested that an age of less than five years at the time of the index procedure is the best predictor of long-term success, regardless of the amount of subluxation2, whereas others have suggested that the initial migration percentage has a better predictive value3. Some studies have shown ambulatory status to have strong predictive value1, whereas others have found it to be less valuable4. It is clear, however, that outcomes tend to decline with longer-term follow-up1,5. Shore et al. also found a progressive deterioration; the longer they followed their patients, the poorer the results were.
After reviewing the data in the paper, the reader must consider whether soft-tissue releases alone should still have an important role in treating hip subluxation in a nonambulatory patient with cerebral palsy. Unfortunately, other surgical options may be limited in a very young patient with hip subluxation, especially since many patients with cerebral palsy are small for their age. Fixation options for a femoral osteotomy may be limited, and patients will typically lose the proximal femoral varus correction with growth, which can lead to recurrent hip subluxation. There is no way to discern from the authors’ data whether the soft-tissue releases delayed progression of the subluxation. In a patient who may be too small to be a good candidate for comprehensive osseous reconstruction, isolated soft-tissue procedures would seem to have a place. On the basis of their results, the authors believe that soft-tissue release should probably be viewed as a “temporizing” method in a patient with a GMFCS classification of IV or V, and they present powerful evidence to support that view.