Danish survey of acetabular component positioning practice during primary total hip arthroplasty

The Lewinnek and Callanan "safe zones" have been widely used to minimise the dislocation fre-quency in total hip arthroplasty (THA), but recent studies have questioned the association between "safe zones" and lower dislocation rates. The purpose of this study was to investigate: 1) if hip surgeons agree on a specific "safe zone" for cup positioning and 2) surgeons' surgical practice patterns regarding recurring instability in primary THA.

A survey was performed among hip surgeons during the 2015 Annual Meeting of the Danish Orthopaedic Society. The survey contained questions on optimal component positioning, surgical practice patterns in primary THA, indications and surgical techniques used in revision THA.

A total of 42 questionnaires were collected, two were excluded, leaving 40 for analyses. 97% of the surgeons reported an optimum cup anteversion within the Lewinnek and Callanan "safe zones", whereas 97% and 83% reported optimum cup inclination within the Lewinnek and Callanan "safe zones", respectively. The reported range for optimal cup positioning varied from 30-55 degrees of inclination and 15-30 degrees of anteversion. The minimum and max-imum accepted cup inclination and anteversion within the Lewinnek "safe zone" was 68% and 67%, respectively.

Hip surgeons agree that optimum cup po-sitioning should lie within the Lewinnek "safe zone", but they do not agree on the exact optimal cup positioning with respect to inclination and anteversion. This is in accordance with current evidence that strict usage of the Lewinnek "safe zone" cannot be justified.

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