gms | German Medical Science

Objectives: Impingement of the psoas muscle in total hip replacement can occur in six situations, which can be potentiated among themselves: 1) When oversize acetabulum are placed than the anatomical acetabulum; 2) when there is an excessive ante version of the component and the edge of the same rose against the muscle; 3) Lack of anterior wall as in hip dysplasia, where the muscle comes into contact with the acetabular component; 4) Cement protrusion on the anterior face of the acetabular component; 5) Screws that protrude through the anterior column and contact the psoas muscle; 6) An excess of the off set in the femoral component, which elongates the psoas muscle.

The objective of this work is to show the relationship between the oversized socket and the impingement of the psoas iliac muscle in primary THR in cadaveric study and clinical series.

Methods: Five cadavers were studied 3 men and 2 women, the mean height was 1.15 cm and the mean weight was 78 kg. In all three men, an acetabule oversized 4 mm larger than the corresponding anatomically. In the two women, the anterior acetabular column was milled, simulating a hip dysplasia, and then a prosthetic acetabulum of the same size as the anatomic was placed.

Between 2011 to 2016, 52 oversized acetabulum were performed in our centre, 15 were compatible with psoitis, diagnosed by ultrasound as an anechoic area in the psoas muscle, in close relation to the acetabular component.

They mean age was 50 years old (35 - 73). Mean follow-up was 41 months (25 56). Six were men and seven hips were on the right side. Eleven cases were posterior-lateral and 4 anterior-lateral approach.

The diagnosis was in 8 cases of hip dysplasia, 5 of aseptic necrosis and 2 of coxarthrosis. The mean onset of pain was 31 weeks (7- 54).

Results: In the cadaver study the close relationship between psoas m.-iliac and the largest acetabulum and the possibility of irritation of the muscle is greater in the absence of anterior wall. The onset of symptoms was at 16 months after surgery, in the dysplastic patients was earlier. In tomographic images it is evident in all symptomatic patients that the acetabulum exceeds the anterior brow limit by more than 0.8 mm.

Conclusion: Psoitis is possible after THR, especially in oversized socket and dysplastic hip.