[Air permeable diaphyseal obturators: efficacity of femoral cementing and prevention of associated cardiovascular disorders].

PURPOSE OF THE STUDY

Insertion of cement plugs into the femoral shaft has become an essential part of total hip arthroplasty procedures. The goal is to achieve secure cementing of the femoral component, but the pressure induced can cause serious problems. The purpose of this study was to determine the effect of a flexible bioabsorbable cement restrictor with decompression valves on cementing efficacy and to determine the effect of inserting the restrictor then the cement plug into the femoral shaft on respiratory functions.

MATERIAL AND METHODS

The restrictor was implanted in 108 patients undergoing first-intention total hip arthroplasty. The canal was prepared and calibrated before inserting the restrictor at a depth estimated at preoperative planning to be 10 to 20 mm below the tip of the femoral stem. The efficacy of the restrictor was assessed using radiographic criteria for the quality of the cement sheath and its position relative to the femoral stem. Oxygen saturation of arterial blood and end-expiration PCO2 were measured at first incision, at insertion of the restrictor, at insertion of the cement plug, and at insertion of the femoral stem.

RESULTS

The relative position of the restrictor was measured on postoperative x-rays at less than 20 mm in 75% of the patients, at 20-40 mm in 13% and at more than 40 mm in 12%. No cement leakage through the restrictor was identified on postoperative x-rays. The quality of the cement sheath was satisfactory in 71% of the patients (77 procedures), fair in 20% (22 procedures) and poor in 8% (9 procedures). For a first group of patients operated on under spinal anesthesia and optional oxygen delivered with a face mask, there was no significant difference in arterial blood oxygen saturation before the procedure and during the four explored operative times. Conversely, in a second group of patients who had general anesthesia without oxygen enrichment of the initial oxygen-nitrogen protoxide gas mixture, arterial blood oxygen saturation during the four operative times was statistically different from the preoperative value. The same observation was made for end-expiratory PCO2.

DISCUSSION

The retrictor's decompression valves did not allow cement leakage beyond the restrictor. The risk of restrictor migration after insertion and after the increased pressure due to cement plug insertion was not increased and was found to be less than rates reported in the literature. In the patients who had general anesthesia, blood gases showed a minimal, but significant, decrease during the operative times susceptible to induce increased intramedullary pressure. In patients who had a non-cemented acetabular insert, use of the pressure-valve cement restrictor appeared to stabilize these parameters.