20-year follow-up finds FAI and poor hip scores common after in situ pinning
Slipped capital femoral epiphysis (SCFE) is often treated using in situ fixation with no attempt to reduce the slip. However, long-term follow-up shows that such an approach can result in clinical femoroacetabular impingement (FAI) in nearly one third of hips, leading to a large number of patients with poor function at a relatively young age, according to “Femoroacetabular impingement at 20 years follow-up of in-situ fixation for slipped capital femoral epiphysis,” a paper presented by Daniel J. Sucato, MD, MS, at the 2010 AAOS Annual Meeting.
“SCFE occurs when you’re very young (Fig. 1),” explained Dr. Sucato. “In general, we put a screw in the femur and stabilize it just so it doesn’t slip further. Many of those patients do very well in the short term, but in the long term, they may experience early osteoarthritis (OA) and pain. And the reason they get these symptoms and pain is because of the FAI.”
FAI as an outcome of SCFE
To investigate the likelihood of FAI, the research team reviewed the records of all patients who underwent in situ pinning for SCFE at a single institution prior to 1995. Overall, 66 patients (93 hips) met inclusion criteria and returned for clinical and radiographic evaluation. At final evaluation, the research team excluded an additional 3 hips—two that had received total hip arthroplasties and one that had undergone hip joint fusion due to osteonecrosis of the femoral head.
“What sets this study apart,” said Dr. Sucato, “is that it has a long-term follow-up on a fairly large number of patients and puts this newer concept of FAI into perspective in relation to outcomes for SCFE.”
The average age of patients at the time of surgery was 12.6 (±1.7) years, and patients had an average body mass index (BMI) of 27.02 (±5.46). Clinically, 26 hips were unstable and 67 were stable, with 15 slips classified as acute, 35 as acute-on-chronic, and 43 as chronic. Radiographically, 52 patients had mild slips, 38 had moderate slips, and 3 had severe slips.
Poor scores at follow-up
At 20.0 (±4.2) years follow-up, 29 hips (32.2 percent) had positive anterior impingement tests, and the Trendelenburg test was positive in 23 hips (25.5 percent) on the affected side. Additionally, 31 hips (34.4 percent) had shortening of the affected limb compared to the contralateral side.
Range of motion was also limited. Average flexion was 91.9 degrees (±18.4 degrees), with 24 hips having less than 90 degrees of flexion. Average internal rotation was 4.6 degrees (±13.6 degrees), with 44 hips having internal rotation of 0 degrees or less.
Of 89 hips that were evaluated radiographically, 53 displayed some degree of OA changes in the joint. Using the Tonnis OA grading system, 41 were classified as grade 1 (increased sclerosis, slight joint space narrowing, no or slight loss of head sphericity), 11 as grade 2 (small cysts, moderate joint space narrowing, moderate loss of head sphericity), and 1 as grade 3 (large cysts, severe joint space narrowing, severe deformity of the head).
Furthermore, the mean Modified Harris Hip Score across all patients was 84.41 (±14.78), with 26 hips scoring less than 80—representing an unsatisfactory outcome.
“We were a little bit surprised that, at around 30 years of age, 30 percent of the patients didn’t show very good results,” said Dr. Sucato. “Almost 70 percent had radiographic impingement, and 30 percent had suboptimal Harris Hip Scores. I knew that we would see FAI and bad functional scores, but not in almost one third of the patients. Many of these patients are probably limiting their activities, which is not very good for their overall general health.”
A more aggressive approach
Dr. Sucato pointed out that, at the time of the study, none of the patients was seeking treatment for lack of internal rotation or FAI. He postulated that most of the patients have made lifestyle adaptations to compensate for their limited range of motion. Yet the relatively high number of unsatisfactory outcomes led him to conclude that taking a wait-and-see approach to young patients with SCFE may not be the best approach.
“I think the data suggest a few things,” said Dr. Sucato. “One is that perhaps we need to be more aggressive in realigning these patients when their symptoms start, as opposed to waiting. At some point, it becomes too late to realign them, and the next step is arthroplasty.
“The second is that maybe we should be studying them with more advanced imaging techniques such as magnetic resonance imaging arthrogram before adulthood. Maybe we should be identifying the FAI a little bit earlier, so that we can be more aggressive in aligning the femoral heads better.
“Finally, we need to continue to pursue the concept of immediate reduction of moderate and severe SCFE using the surgical hip dislocation approach and make this a safe procedure to restore normal alignment.”
Dr. Sucato’s coauthors include Dinesh Thawrani, MD; Tara Kristof, BA; and Adriana Hernandez, BS. Dr. Sucato reports receiving royalties and research or institutional support from Medtronic.
Peter Pollack is a staff writer for AAOS Now. He can be reached at firstname.lastname@example.org