Prediction of avascular necrosis of the femoral head by measuring intramedullary oxygen tension after femoral neck fracture.
OBJECTIVE
To measure the intramedullary oxygen tension of the proximal femur after a femoral neck fracture and to evaluate the usefulness of that monitoring for prediction of subsequent avascular necrosis.


METHODS
Prospective case series with comparison group.


METHODS
University hospital.


METHODS
Measurement of intramedullary oxygen tension of the femoral head and neck during internal fixation using the Hansson hook-pin system.


METHODS
Intramedullary oxygen tension was measured directly during surgery in 17 patients with 18 femoral neck fractures treated by internal fixation between October 2000 and February 2002. The intramedullary oxygen tension was measured by using polarographic oxygen electrodes and an oxygen monitor at four points: (A) 1 cm distal from the joint surface; (B) 1 cm proximal from the fracture site; (C) 1 cm distal from the fracture site; and (D) 1 cm proximal from the lateral wall. The presence or absence of avascular necrosis was evaluated by magnetic resonance imaging (MRI) at 2, 6, and 12 months after surgery.


RESULTS
MRI evaluation showed 11 fractures healed without complications, and 7 fractures developed avascular necrosis. We found significant differences in the distribution of intramedullary oxygen tension of the femoral head between points A (1 cm from the joint surface) and B (1 cm proximal from the fracture site) in those patients who developed avascular necrosis (P = 0.039); that is the oxygen tension was lower at point A than at point B. In contrast, in those patients who did not develop avascular necrosis there was no significant differences between point A and B were found (P = 0.059). The sensitivity and specificity for prediction of avascular necrosis were 1.0 and 0.82 (Fischer exact probability test, P = 0.002), respectively, when the cut-off level of oxygen tension differences between points A and B was set at 3.1 mm Hg.


CONCLUSIONS
We believe that this method of measuring intramedullary oxygen tension is simpler and less invasive than other currently used methods and has the possibility for intraoperatively identifying a risk group that can develop a late segmental collapse of the femoral head secondary to avascular necrosis.
Watanabe
Yoshinobu
Y
Department of Orthopaedic Surgery, Teikyo University School of Medicine, Tokyo, Japan. fracture@zad.att.ne.jp
Terashima
Yuichiro
Y
Takenaka
Nobuyuki
N
Kobayashi
Makoto
M
Matsushita
Takashi
T
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D004567:Electrodes, Implanted; D005260:Female; D005265:Femoral Neck Fractures / Q000150:complications* / Q000175:diagnosis / Q000601:surgery; D005270:Femur Head / Q000378:metabolism*; D005271:Femur Head Necrosis / Q000175:diagnosis* / Q000209:etiology / Q000378:metabolism; D005272:Femur Neck / Q000378:metabolism*; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism*; D011048:Polarography / Q000295:instrumentation; D011237:Predictive Value of Tests; D011446:Prospective Studies
D010100:Oxygen