O3273 THE IMPLICATIONS OF SAGITTAL PLANE MALPOSITIONING OF THE STEM IN CEMENTED CHARNLEY TOTAL HIP REPLACEMENT: A RADIOGRAPHIC STUDY

Abstract

Aims: Prosthesis malpositioning and inadequate cement mantles have been shown to adversely affect outcomes in cemented total hip arthroplasty. Although this has been extensively studied and reported for anteroposterior (AP) radiographs, we have found a paucity of literature concerning lateral radiographs which this study addresses. Methods: We analysed radiographs of 100 patients (Group I) with cemented Charnley total hip replacements (52 ßanged, 48 round back) performed through the lateral approach to determine the relationship between stem positioning and cement mantles in both AP and lateral radiographs. The measurements were made by a single observer and the data was analysed using chi squared tests to compare categorical data. Results: The most common stem malpositioning was seen in the lateral radiographs with þfty þve percent of stems directed 4 or more degrees from anterior to posterior (A to P). In contrast on the AP radiographs 18% of stems were directed from medial to lateral (Varus) and 3% of stems were directed from lateral to medial (Valgus) 4 or more degrees. There was no relationship between the different malpositions. Adequate resection of the posterior femoral neck gave better alignment of the stem in the lateral radiograph (p< 0.001). The ßanged stems were signiþcantly more in varus as compared to round back stems (p< 0.01). Cement mantles were most often deþcient in Gruen zone 12. There was a strong association between sagittal malpositioning and deþcient zones 12 and 9 (p< 0.001). Conclusions: This study demonstrates that sagittal mal-positioning of the stem is most important and surgical technique has a signiþcant inßuence on the same.