[Revision surgery for inlay, neck and head failure of hip endoprostheses with fixed metal components].

Abstract

Objective: The aim of this technique is to minimize the extent of revision surgery in cases of inlay and/or head failure and fixed metal components of hip endoprostheses by replacing only the modular components, while still effectively solving the problem. In some cases, it may be justified to insert a nonprosthetic polyethylene inlay or a smaller polyethylene cup cemented into the fixed metal cup.

Indications: Revision surgery for hip endoprostheses with inlay wear and fixed metal components, damage to a ceramic inlay or ceramic head, necessary head replacement due to instability, early infection or mismatch. Cementing a polyethylene inlay or polyethylene cup into the metal cup can be indicated in cases where the inlay is no longer available and the metal cup is firmly integrated and undamaged or only slightly damaged, in order to avoid major surgery and risk reduction in ill or very old patients.

Contraindications: The general contraindications for planned surgery apply. Local infections, bone tumors near the joint, periprosthetic fractures, cup and/or stem loosening, late infections and uncontrollable instability are also contraindications for isolated replacement of the inlay and head.

Surgical technique: The joint is usually surgically exposed via the pre-existing access. After removing the prosthesis head the socket is exposed. The polyethylene or ceramic inlay is removed as gently as possible. If no compatible inlay for the existing prosthesis is available, a nonmatching inlay or a polyethylene cup can be cemented in place; in this case, the inner surface of the metal cup is roughened to ensure adequate cement bonding. With respect to head replacement, the extent of cone damage must be taken into account. In any case, revision head systems with metal sleeves are required to prevent fracture of the ceramic head due to incongruity.

Postoperative management: After isolated inlay or head replacement, early functional physiotherapy with mobilization under full weight bearing on forearm crutches can usually be started on the first postoperative day.

Results: Good results can be achieved through revision surgery with isolated replacement of the prosthesis head in combination with the cementing of a polyethylene inlay into fixed metal cups. Even after 10 years there are significant increases in the scores and in 80-93% of cases, no further revision surgery is necessary. The rate of construct failure in the contact area between the inlay, cement and metal cup is less than 5%.