Swiss study finds even mild SCFE with in situ pinning can produce early damage

“Data have shown that slipped capital femoral epiphysis (SCFE) treated with pinning in situ can develop into symptomatic femoroacetabular impingement (FAI) over time,” said Harish S. Hosalkar, MD.

“Even mild cases of SCFE can cause intra-articular damage to the labrum and acetabular cartilage,” he said.

Dr. Hosalkar and his colleagues verified the connection between SCFE and symptomatic FAI by conducting a retrospective review at the department of orthopaedic surgery, Inselspital, University of Berne, Switzerland.

They reported their findings at the recent annual meeting of the Pediatric Orthopaedic Society of North America.

SCFE, FAI connection validated
Researchers reviewed the records of 850 consecutive patients who were diagnosed with symptomatic FAI between 1997 and 2008 and underwent open surgical dislocation. They identified 55 patients who had pinning in situ for mild SCFE, 28 (33 hips) of whom later had open surgical hip dislocation for FAI.

Of the 55 hips, 23 had advanced changes of osteoarthritis and needed total hip arthroplasty (THA) and 4 refused surgery.

The mean age of patients at in situ pinning was 12.6 years (range: 11 to 14 years); the mean duration between pinning and open surgical dislocation for FAI was 11.6 years (range: 2 to 30 years). At the time of surgery, patients had a mean age of 24.3 years (range: 16 to 43 years old).

The investigators found 20 hips with cam-type impingements and 13 with mixed-type impingement. (For more information, see “Types of FAI impingements.”)

Important correlations identified
Dr. Hosalker and his colleagues also reviewed the intraoperative reports for each patient to determine the extent and location of damage to the labrum or articular cartilage. They then graded labral damage as L1, L2, or L3, and cartilage damage as C1, C2, or C3, depending on the degree of severity (Table 1).

“In the case of mixed lesions, the highest number was considered,” Dr. Hosalkar said.

The investigators also wanted to determine whether this damage was progressive over time. “That’s the question that patients ask their orthopaedic surgeons. They want to know if they are causing further harm to their hips once they are diagnosed with symptomatic FAI and choose to wait longer without intervention,” he said.

They found a strong correlation between the severity of damage and time duration. “Interestingly, we found a correlation, even if patients who eventually had THA were included as an end point. A pattern of progressive damage was evident,” Dr. Hosalker stated.

“In addition, we found a significant difference (P < 0.01) between the groups in terms of the degree of damage and the years after pinning in situ,” he explained.

“Over time, symptomatic FAI can develop in a subset of SCFE patients with even mild slips who undergo pinning in situ, due to abnormal morphology,” he said.

Dr. Hosalkar emphasized that though this study raised more questions than it answered, it did suggest that “mild SCFE with pinning in situ can develop symptomatic FAI with time. Intra-articular damage does occur and seems to worsen with time (Fig. 1).”

Co-authors for “Symptomatic femoroacetabular impingement following mild slipped capital femoral epiphysis after pinning in situ” are Timo Schmid, MD; Lorenz Buchler, MD; Moritz Tannast, MD; Teddy Slongo, MD and Klaus Siebenrock, MD.

Dr. Hosalker did not report any conflicts of interest. Dr. Siebenrock’s institution receives support from Mathys Ltd., Synthes, and Zimmer. Disclosures were not available for any of the other authors.

Annie Hayashi is the senior science writer for AAOS Now. She can be reached at hayashi@aaos.org

Types of FAI impingement
Reinhold Ganz, MD, who defined the concept of femoroacetabular impingement (FAI), classified impingements into three types—pincer, cam, and mixed. According to Dr. Ganz, a cam-type impingement is caused by “an offset pathomorphology between the head and neck and produces an outside-in delamination of the acetabulum.”

“The pincer-type FAI...is produced by a more linear impact between a local (retroversion of the acetabulum) or general overcoverage (coxa profunda/protrusio) of the acetabulum. The damage pattern is more restricted to the rim and the process of joint degeneration is slower.”

According to Dr. Ganz, most hips show a mixed-type of FAI with a predominance of the cam-type.

References:

1. Ganz R, Leunig M, Leunig-Ganz, et. al. The etiology of osteoarthritis of the hip: An integrated mechanical concept. Clin Orthop Relat Res. 2008;466;264-72.