Background: We have noticed while performing total hip arthroplasty, that during skin closure, the anterior edge of the wound tends to migrate proximally in relation to the posterior edge. This result is an inaccurate approximation of the wound, the so-called ‘dogs ear’. The aims of the study were to assess and quantify the degree of migration of the anterior edge relative to the posterior one using an invisible marker and to see whether marking the incision site prior to surgery improved skin closure.

Material and methods: We included forty patients undergoing primary hip arthroplasty in the study. Prior to surgery, the skin was marked with five lines perpendicular to the incision line with an invisible skin marker using the greater trochanter as reference point. The skin was then routinely prepared with betadine and a proprietary adhesive incision drape (Ioban 2) was applied to the incision site. The surgeon performed the operation routinely and intra-operatively, the subcutaneous fat content was measured at three set points and averaged. After the wound had been closed, an ultraviolet light source was used to highlight the invisible lines. The gap between the anterior and posterior edge was measured for each line. One set of patients had their incision site marked with a visible marker on the incision drape while the other set did not.

Results: There was a persistent proximal migration of the anterior edge in relation to the posterior edge. The proximal part of the incision site had a more marked skin migration compared to the distal wound. In the unmarked group, the proximal part of the anterior edge tended to migrate on average by 9.5 mm (from 30 mm to 5 mm) in respect to the posterior edge. In the marked group, this migration was reduced to an average of 1.6 mm (from 2 mm to 0 mm) and there was a statistical difference between the 2 groups with p< 0.0001 using the independent t-test as illustrated by the table. Of note, the degree of migration did not vary with the thickness of the fat content. Also, all the wounds healed with no signs of infection.

Conclusion: From this study, we have been able to quantify objectively the extent of migration of the anterior edge of the wound in a hip incision in relation to the posterior edge. Improved hip closure following total hip replacement was achieved after marking the skin prior to surgery. We therefore recommend marking the skin pre-operatively prior to hip incision in order to achieve accurate skin closure as part of the general principle of proper wound closure.