Measurement of safe acetabular medial wall defect size in revision hip arthroplasty with a porous cup.

INTRODUCTION: The majority of acetabular revisions can be performed with an uncemented, porous acetabular component with or without bone grafting. These are contained acetabular defects, with an intact acetabular rim (Paprosky type I and II). As defects of the medial wall of the acetabulum are a challenge situation revision surgery, we performed this biomechanical study on a pig pelvis model with contained acetabular defects to determine the size of medial wall defect at which the acetabular cup will have sufficient primary stability. MATERIALS AND METHODS: In 24 pig pelvis models, different diameter of medial wall defects were created, followed by acetabular component placement. The acetabulum externally loaded, and the force at a level in which the acetabular component remains stable for each diameter of defect, or at which point the acetabular cup moves into the pelvis for >2 mm. RESULTS: In the models with acetabular medial wall defects of 10 and 20 mm, 2 mm acetabular displacement occurred under a force between 1000 and 1500 N. In those with a medial wall defect of 25 mm, the force that caused acetabular instability was between 700 and 1000 N. In the models with 30 mm of medial wall defect all acetabular components were unstable under a force of 700 N. CONCLUSIONS: According to our results, acetabular component should be stable if the defect of the medial wall of the acetabulum is less than 68% of the diameter of the acetabular component or if the uncovered surface area of the acetabular component is not greater than 27%, and the force <700 N. For a load of 1000 N, the medial wall defect should not exceed 45% of acetabular component diameter or 18% of uncovered acetabular component surface.

Revision of Acetabular Component with a Debonded Porous Coating in an Elderly Patient.

Debonding of the porous coating from the acetabular component of a total hip endoprosthesis is a rare complication. Revision total hip arthroplasty for an unstable acetabular component with a debonded porous coating strongly fixed to the bone can be challenging, especially in elderly patients of poor overall health. In such patients, revision procedures should be as simple and safe as possible. We present our technique of solving that problem in a case of an 82-year-old female with bad general condition and unstable acetabular component of hip endoprosthesis. Because of extremely deficient bone stock, a well-fixed porous coating was left in acetabulum to serve as a "cage", allowing cemented acetabular component placement. This procedure can reduce the risk of intraoperative bone fracture, blood loss, and duration of surgery, which is important in elderly patients with poor overall health.

Endoscopic treatment of the external snapping hip syndrome: surgical technique and report of two cases.

Snapping hip or coxa saltans is a condition characterized by an audible and/or palpable snapping during hip movement and can be associated with pain around the hip. There are various causes of this condition and can be divided into two types: extra-articular and intra-articular. The most common type is the external extra-articular, where the snapping is due to thickened posterior part of the iliotibial band or anterior part of the gluteus maximus muscle sliding over the greater trochanter during hip movement. Two patients with external snapping hip are presented, who were treated with our original endoscopic iliotibial band release and greater trochanteric bursectomy. There were no surgical complications and the patients did not experience snapping or pain in the hip during 24-month follow-up period. Results of various open techniques and one endoscopic technique in the treatment of external snapping hip are also reported.