Severe damage of the femoral head after dislocation and difficult reduction maneuvers after total hip arthroplasty.

INTRODUCTION: Aseptic loosening associated with osteolysis and release of wear particles is the main reason for revision of total hip arthroplasty (THA). Damage of femoral heads is well known to increase the wear rate at the articulating surface. Instability and dislocation are serious complications and are the second most frequent reason for revision surgery after THA. In the present work the possible damaging of the femoral head as a result of difficult reduction maneuvers of dislocated THA should be investigated. PATIENTS AND METHODS: In three cases of total hip dislocation an open reduction was performed after dislocation of primary THA. Thereby one metal and two ceramic femoral heads were retrieved. Each head was analyzed macroscopically and by scanning electron microscopy (SEM) subsequently. RESULTS: In the first case the SEM analysis revealed severe titanium deposits on the retrieved ceramic head in the case of repeated unsuccessful closed reduction maneuvers. In the second case the retrieved ceramic head showed multiple scratches and a spalling of the surface structure. In the third case the retrieved metal head presented a roughened surface and severe scratches at the articulating area. DISCUSSION: Difficult reduction maneuvers following total hip dislocation can lead to severe damaging of the femoral head associated with an increase of the surface roughness. While repeated reduction maneuvers can lead to metallic deposits and spalling of the surface of ceramic heads, severe scratches can occur at metal heads. The damaging of the femoral head at the articulating surface can lead to increased wear and subsequent aseptic implant loosening. Therefore, open joint reduction has to be considered in cases of difficult or unsuccessful closed reduction maneuvers to prevent severe femoral head damage which may cause an increased release of wear particles.

Pitfalls in the use of acetabular reinforcement rings in total hip revision.

INTRODUCTION: For the reconstruction of acetabular bone defects different types of acetabular reinforcement rings are being used. In clinical practice, these implants showed to some extent good long-term results. In the present work pitfalls and complications after the implantation of acetabular reinforcement rings as well as possible solutions are being discussed. MATERIAL AND METHODS: In the first case recurrent dislocation was caused by the malposition of the acetabular component with an impingement of the protruding bone cement and the anterior edge of the acetabular ring as well as muscle insufficiency as a result of the shortening of the leg length. The second case revealed an impingement of the iliopsoas tendon due to a protruding acetabular reinforcement ring. During revision, bone cement was used to smoothen the protruding anterior edge of the acetabular reconstruction ring in order to obtain a relieved sliding of the tendon. Furthermore, we report on the case of a delayed neuropathy of the sciatic nerve after reconstruction of the acetabulum with an acetabular reinforcement ring. RESULTS: Intraoperatively an impingement of the sciatic nerve at the protruding dorsal edge of the acetabular reinforcement ring and the surrounding scar tissue was found. In a further case an aseptic loosening of an acetabular reinforcement ring caused the formation of an excessive granuloma with a large intrapelvic portion. The granuloma led to persisting senso-motoric deficits of the femoral nerve. In summary, based on these clinical cases possible pitfalls, associated with the use of acetabular reinforcement rings, are shown. The mal-positioning and the intra-operative re-shaping of the implant by the surgeon are pointed out as the substantial factors for the occurrence of an impingement phenomenon and total hip instability. Furthermore, in case of an adequate orientation of the cemented polyethylene insert an improper position of the acetabular ring which results in protruding edges has to be considered as a cause of a prosthetic impingement. CONCLUSION: The cases presented emphasize the necessity of prevention of such pitfalls intra-operatively as well as accurate analysis of implant failures. Furthermore, they suggest explicit preoperative planning before deciding on the strategy of revision surgery of acetabular reinforcement rings.