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scratching effect against the femoral canal due to the rougher surface of the plasma-sprayporous-coating works advantageously for initial mechanical stability.Thursday, October 7, 2010, 11:10-11:50Session A4: Hip ResurfacingThe Fate of Initial Gaps Between the Cup and Acetabular Floor inResurfacing Hip ArthroplastyIntroduction*Satoshi Nakasone - Osaka University Graduate School of Medicine - Suita, JapanMasaki Takao - Osaka University Graduate School of Medicine - Suita, JapanTakashi Nishii - Osaka University Graduate School of Medicine - Suita, JapanTakashi Sakai - Osaka University Graduate School of Medicine - Suita, JapanNobuo Nakamura - Kyowakai Hospital - Suita, JapanNobuhiko Sugano - Osaka University Graduate School of Medicine - Suita, Japan*Email: satoshi_nakasone@hotmail.comCurrent standard cups of metal on metal resurfacing hip arthroplasty (RHA) have no dome holesand it is very difficult for surgeons to confirm full seating of these cups. This sometimes resultsin gap formation between the cup and acetabular floor. Although the incidence of initial gapsusing modular press-fit cups with dome screw holes has been reported to range from 20 to35%, few studies have reported the incidence of gap formation with monoblock metal cups andits clinical consequences in RHA. The purpose of this study was to investigate retrospectivelythe incidence of initial gap formation and whether the initial gap influences the clinical resultsin RHA.Material and MethodRHA was performed on 166 hips of 146 patients using the Birmingham Hip Resurfacing (BHR)(MMT, UK) between 1998 and 2007. Mean age at operation was 48.7 years (range, 19-85years). Mean duration of follow-up was 6.9 years (2.0-10.6). Acetabular reaming wasperformed with the use of hemispherical reamers and the reamer size was increased up to anodd number diameter which provided tight rim fit in the antero-posterior direction. The samesize hemispherical provisional cup with dome holes and slits was used to check the cavity forcomplete seating. If the provisional cup could not be seated on the floor, reaming was repeatedwith the same reamer to remove the rim bump until full seating was achieved. Acetabular cupsof 1mm larger diameter were impacted into the acetabulum by a press-fit technique. Afterpress-fit fixation, the stability of the cups was confirmed with a synchronized movement of thepelvis and the cup inserter by applying a gentle torque. Clinical evaluation was performed usingWOMAC at the latest follow-up. Radiographic assessments were performed using radiographsimmediately after the surgery, at 3 weeks, 3 months, 1 year, and then annually thereafter. Weevaluated the height of the gap between the cup and acetabular surface, cup inclination angle,cup migration and the time to gap filling. To investigate the relationship between the magnitudeof the gap and the radiographic results, the patients were divided into two groups according tothe height of the initial gap; the cases with a gap of less than 3 mm on the initial radiographfile:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]