Factors Affecting Outcomes of Slipped Capital Femoral Epiphysis

Abstract

Slipped capital femoral epiphysis (SCFE) is a frequent cause of nontraumatic painful hip of the adolescence. It is the result of the separation of the proximal femoral growth cartilage at the level of the hypertrophic cell zone. The femoral neck metaphysis rotates externally and migrates proximally relative to the femoral head epiphysis, which is stably seated in the acetabulum; early diagnosis and in situ stabilization grants the best long term results. Numerous factors affect treatment outcomes. Not all implants have the same effect on the slipped physis. Application of the traditionally used implants, such as non-threaded pins and cannulated screws, is questioned. Modern implants are available, which stabilize the slip without accelerating physis fusion. This allows femoral head and neck growth and remodeling to limit the post-slip sequellae on hip anatomy and function. Femoroacetabular impingement (FAI) complicates almost all slips. It causes progressive labral and articular cartilage damage and leads to early hip osteoarthritis and total hip replacement, approximately ten years earlier compared to the general population. Avascular necrosis of the femoral head is a dramatic complication, seen almost exclusively in unstable slips. It develops within months after the slip and leads to immediate articular joint degeneration and the need for total hip replacement. Another serious complication of SCFE is chondrolysis, which is a rapid progressive articular cartilage degeneration leading to a narrow joint space and restriction of hip motion. Implant-related complications, such as migration and loosening, may lead to the progression of the slip. Though bilateral disease is quite frequent, there is no consensus about the need for preventive surgery on the healthy contralateral hip. Diagnosis of SCFE is frequently missed or delayed, leading to slips of higher severity. Silent slippage of the capital femoral epiphysis is highly suspected as an underlying cause of cam-type FAI and earlyonset hip osteoarthritis. There is controversy, whether asymptomatic implants should be removed. Novel surgical techniques, such as the modified Dunn procedure and hip arthroscopy, seem to be effective modalities for the prevention of FAI in SCFE.

Causes of Delayed Diagnosis of Slipped Capital Femoral Epiphysis: The Importance of the Frog Lateral Pelvis Projection

“…On microscopy, SCFE is a Salter-Harris type physeal fracture through the hypertrophic cell zone, which is the most vulnerable area (locus minoris resistentiae) of the physis [3][4]. Hormonal factors, mainly hypothyroidism (up to 40%), render the physis susceptible to shear stresses, especially in cases of concomitant obesity [1,5]. The result is abnormal movement (varus and external rotation) of the femoral neck metaphysis relative to the femoral head epiphysis [1].…”

“…Residual growth and remodeling may only partially restore the post-slip femoral neck deformity and thus may not protect from FAI. [5]. Early hip degeneration and total hip replacement, occurring 10 years earlier than expected for the general population, is the fate of the affected hip [12].…”

“…On the other hand, slip severity correlates strongly with slip chronicity [16][17]. Early diagnosis and treatment is the only effective way to prevent further slippage of the capital femoral epiphysis and to obtain satisfactory long-term results with in-situ stabilization of the slipped physis [2][3]5,[7][8][16][17][18][19][20].…”

“…When the diagnosis is finally set, the slip has usually progressed to a grade of higher severity, implying an increased risk of FAI and less favorable outcomes [5]. Delayed diagnosis of SCFE is universally reported, irrelevant of time and place [2][3]5,[7][8]12,[16][17][18][19][20]. Almost a century ago, Key reported a mean delay of 14.6 months to diagnose SCFE [3].…”

“…Almost a century ago, Key reported a mean delay of 14.6 months to diagnose SCFE [3]. No real progress has been made since then towards a timely diagnosis and treatment of SCFE [2][3]5,[7][8]12,[16][17][18][19][20].…”