Surgeons changing the approach for total hip arthroplasty from posterior to direct anterior with fluoroscopy should consider potential excessive cup anteversion and flexion implantation of the stem in their early experience

Many reports outline the benefits derived from using the direct anterior approach (DAA) in primary total hip arthroplasty (THA); however, the learning curve for the DAA has not been well documented, and the complications associated with the DAA during this learning curve seem relatively high. The aim of this study was to investigate implant positioning in primary THA, when the surgeon was a novice at the DAA, and had previously used the standard posterior approach (PA). We investigated implant positioning in the first 80 consecutive THA cases performed by two senior surgeons using the DAA (with fluoroscopic assistance), and compared them to the same two surgeons' previous 80 respective THA cases performed using their previous standard posterior approach. Cup positioning accuracy was higher for the DAA (p < 0.001) but greater cup anteversion (19.3A degrees +/- 11.0 using the PA vs 27.6A degrees +/- 6.3 using DAA, p < 0.0001) was also demonstrated. A total of 69.3 % of cups in the DAA group were positioned with an anteversion angle greater than their target angle. In the DAA group the stem was more frequently positioned in flexion and less frequently in neutral than for the PA group. Although fluoroscopic assistance seemed to decrease complications such as femoral fracture, surgeons changing from PA to DAA for THA should consider potential excessive cup anteversion and flexion implantation of the stem in their early experience with DAA.