Case reports: acetabular damage after mild slipped capital femoral epiphysis

Abstract

Background: Slipped capital femoral epiphysis (SCFE) is a common hip problem in adolescents that results in a cam-type femoroacetabular impingement (FAI) deformity. Although the treatment for mild (slip angle of 0°-30°) and moderate (slip angle of 31°-60°) SCFE has historically been in situ fixation, recent studies have demonstrated impingement-related articular damage, irrespective of slip severity. Our series confirms previous reports that acetabular chondral injury occurs in mild to low-moderate (slip angle of ≤ 40°) SCFE.

Case description: We retrospectively reviewed five patients who underwent arthroscopy and femoral osteoplasty within 18 months after in situ stabilization. All had labral and/or acetabular damage.

Literature review: Osteoarthritis rates after SCFE range from 24% to 92% at 11 to 28 years, depending on how osteoarthritis is defined. Long-term followup suggests patients have acceptable outcomes, but these studies are limited by heterogeneity and a ceiling effect from the instruments used to assess function. Although the femoral deformity remodels, it is unclear what secondary changes occur in the acetabulum. Recent investigations suggest patients are functionally limited after SCFE owing to FAI compared with controls. MRI findings and surgical reports document impingement-related joint damage after SCFE, even in the absence of symptoms. Based on this, some advocate timely correction of the cam deformity inherent in SCFE.

Purposes and clinical relevance: Further study is warranted to determine whether immediate osteoplasty after in situ fixation of mild SCFE is beneficial to limit articular damage and improve long-term outcomes.

Fig. 1A–F

(A) In an AP pelvis radiograph of Patient 1, the right lateral center-edge angle is 37°, the Tönnis acetabular roof angle is 0°, and the anterior center-edge angle on false-profile view (not shown) is 45°. (B) In the frog leg lateral image, the right hip slip angle is 28° and the alpha angle is 70°. Note the slip angle is reported as head-shaft angle on the involved side, rather than as a difference between head-shaft angles between the two sides as described by Southwick [33]. (C) Synovitis and labral hyperemia are evident at arthroscopy 5 months after in situ stabilization of the SCFE. (D) There is disruption at the anterior labrochondral junction and (E) an acetabular chondral fissure with a small, unstable flap. (F) A frog leg lateral image after right anterior arthrotomy shows improvement in the femoral head-neck offset.

Fig. 2A–D

(A) A right frog leg lateral view of Patient 2 shows an alpha angle of 87° before osteoplasty. (B) At arthroscopy, there was anterior synovitis and labral fraying with (C) a partial thickness chondral fissure. (D) An intraoperative fluoroscopic image shows an alpha angle of 47° after osteoplasty.

Fig. 3A–G

In (A) AP and (B) 45° Dunn lateral images of Patient 3 on presentation to our institution 16 months after right and 26 months after left in situ fixation of SCFE, the right slip angle is 39° and the alpha angle is 82°. The alpha angle is created from a line drawn through the center of the femoral head and a line parallel to the femoral neck, rather than through the femoral neck itself, due to posterior translation of the femoral head [23, 31]. (C) A second screw was placed to augment epiphyseal fixation. (D) At arthroscopy, there was hyperemia with anterior labral and labrochondral fraying. (E) A broader view demonstrates labral fraying, disruption of the labrochondral junction, and diffuse fibrillation of the cartilage in the anterosuperior quadrant of the acetabulum. (F) After femoral osteoplasty, the alpha angle is 42°. (G) A 45° Dunn lateral view shows maintenance of offset correction at 6 months after right femoral osteoplasty. The patient was pain-free and had returned to competitive sports.

Fig. 4A–E

(A) Irregularity of the left femoral physis is evident on the AP pelvis radiograph of Patient 4. (B) The frog leg lateral image demonstrates a slip angle of 31° and an alpha angle of 85°. (C) An intraoperative fluoroscopic 45° Dunn lateral view shows prominence of the anterior metaphysis with an alpha angle of 60° before osteoplasty. (D) Diffuse labral hyperemia and fraying are seen at arthroscopy, which was performed immediately after in situ fixation. (E) After osteoplasty, the alpha angle is 45°.

Fig. 5A–C

(A) An arthroscopic image shows anterior labral hyperemia and a radial tear (arrow) in Patient 5. The slip angle on the frog leg lateral view (not shown) measures 29°. Intraoperative fluoroscopic 45° Dunn lateral views show (B) an alpha angle of 60° before osteoplasty and (C) an alpha angle of 43° after osteoplasty.

Fig. 6A–D

(A) AP and (B) lateral views show the hip of a 14-year-old boy 3 weeks after in situ fixation of a mild SCFE. (C) AP and (D) lateral views show the hip 17 months later at age 16 years. There is flattening of the lateral acetabular margin at the acetabular epiphysis and sclerosis of the sourcil. Remodeling of the metaphyseal step-off adjacent to the epiphysis (solid arrows) is evident, but a prominence persists distally on the anterior femoral neck. There is lateral extension of the femoral epiphysis (open arrow) [31].