Review Question - QID 218662

The figure of the ICP monitor demonstrates a monophasic waveform, concerning for femoral head hypoperfusion. The next best step is decompression of the hip joint and, if needed, capsulotomy, with a reassessment of perfusion performed between the two steps (Answer 3).

Slipped capital femoral epiphysis (SCFE) is a common condition of the proximal femoral physis that leads to slippage of the metaphysis relative to the epiphysis. It is most commonly seen in obese adolescent males, and it is the most common disorder affecting adolescent hips. Epidemiologically, SCFE is more common in obese children, males, during periods of rapid growth, and in patients with certain endocrinologic disorders. The diagnosis is made with plain radiographs, and the treatment is surgical, which typically consists of percutaneous in situ fixation with a single screw.

Recently, there has been an investigation into the role of intraoperative epiphyseal perfusion monitoring, in hopes that detecting epiphyseal hypoperfusion could decrease the rates of post-SCFE osteonecrosis. This study is performed by introducing a cerebral intracranial pressure (ICP) monitor down the screw into the epiphysis, with probe position verified by radiographs. The presence of a biphasic (arterial) waveform indicates intact perfusion, while the presence of a monophasic waveform is concerning for epiphyseal hypoperfusion. If detected intraoperatively, the presence of a monophasic waveform is first addressed through decompression of the hip joint, with a reassessment of perfusion. If still monophasic, a capsulotomy is recommended.

Upasani et al. investigated the effect of increased hip intracapsular pressure on femoral epiphyseal perfusion in a porcine model. Their study included seven pigs, divided into four "young" hips and five "old" hips. Overall, the authors found that increased intraarticular hip pressure resulted in tamponade of epiphyseal perfusion in the "young" hips, but not the "older" hips. As a result, the authors postulate that young patients with intra-articular proximal femur fractures may benefit from decompression and capsulotomy, as this intervention may decrease the risk of subsequent avascular necrosis.

Schrader et al. report on the results of intraoperative monitoring of epiphyseal perfusion in the setting of SCFE. After screw placement, an ICP monitor was introduced into the screw, and placed into the epiphyseal bone. This technique was used in 23 patients (29 hips), with 15 hips having an unstable SCFE, 11 having a stable SCFE, and 3 hips undergoing prophylactic pinning. Six patients with an unstable SCFE had no measurable flow on the ICP monitor following screw placement. Following decompression +/- capsulotomy, all six of these hips had evidence of biphasic arterial flow on the ICP monitor and at a mean follow-up of two years, none of the unstable SCFEs had evidence of osteonecrosis, much lower than the classically reported rate of 24-47%. Overall, the authors conclude that in unstable SCFE, utilization of this treatment algorithm could potentially decrease the rate of post-SCFE osteonecrosis.

Figure A demonstrates a left-sided SCFE. Figure B is a well-reduced SCFE fixed with a single screw. Figure C is an ICP monitor demonstrating a monophasic waveform, concerning for epiphyseal hypoperfusion.

Incorrect Answers:
Answer 1: This fracture is well-reduced and well-fixed with a single screw. While some surgeons advocate for two screws, an inverted-triangle three-screw configuration is more commonly used for femoral neck fractures.
Answer 2: This patient has evidence of epiphyseal hypoperfusion. Since an ICP monitor was used, the next best step is decompression +/- capsulotomy.
Answers 4 and 5: This fracture is well-reduced. No change to the hardware or reduction is necessary.