Introduction: Cementless implantation of acetabular cups is the standard procedure of choice nowadays. We report on a new hemispheric acetabular socket with Trabecular-Metal-Surface made out of tantalum for cement-less implantation that meets all the requirements that are considered essential for direct osseointegration of cementless implants like porosity, surface roughness and biocompatibility. This multi-center study reports on the surgical technique and the early 5-year clinical results with this implant at three orthopaedic institutions.

Material und Methods: Since 1998 a total of 186 of these cups were implanted in three orthopaedic departments. All patients were followed-up prospectively. 32 implantations were performed with computer-assisted navigation, all others were done manually. In 18 cases the ceramic-on-ceramic articulation was used, all the other patients received Ceramic-on-HDPE as the standard articulation. The cup was combined with different stems including cementless Zweymueller stem, the cementless SBG stem and the cemented Weber-Stuehmer stem. A standard lateral or antero-lateral approach was used in all the patients. The first 112 consecutively patients with a minimum follow-up of 5 years were evaluated.

Results: Postoperative Harris-Hip-Score could be improved to median 92. The positions of all the cups implanted with computer navigation were within a +/−3 range with respect to the intended target whereas manual implantation yielded differences of up to 10. Radiographically all cups showed full osseointegration after one year in all zones. Initial gaps in zone II in 7 cases were filled-up completely. There was no migration and no radiolucency. Two well-fixed cups had to be removed because of infection around the stem. We encountered two dislocations within the first six weeks in patients with Ceramic-on-HDPE-articulation. Both of them could be successfully treated by closed reduction. There were no clinical or radiographic signs of aseptic loosening. No other complications like deep vein thrombosis, hematoma or wound infection did occur.

Conclusion: The new tantalum surface showed excellent osseointegration in all patients. Even in those cases of infection the cup was well-fixed. Due to its hemispheric surface it can be positioned quite easily and shows excellent primary stability. This new poro-coating surface ensures firm fixation of the implant and promises an unprecedented long-term stability.

Introduction: The purpose was to present a new osteotomy technique (trochleoplasty) and its preliminary results for the treatment of femoral trochlear dysplasia with recurrent patellar dislocation.

Methods: Between 1990 and 2002, 59 knees of 51 patients (mean age 224 years) with recurrent patellar dislocation due to femoral trochlear dysplasia were treated uniformly at a single institution with a new osteotomy technique developed by the senior author. A distally connected osteochondral flake is released from the dysplastic trochlea and refixed after the osseous trochlear groove has been reconstructed. 44 patients with 50 involved knees returned at a mean follow-up of 37 months (range 6 to 139) for a physical examination, assessment of knee pain and function, radiographic examination of the knee, and in selectived cases for CT scan, MR imaging and follow-up knee arthroscopy.

Results: Postoperative complications were limited to hemarthros-1, arthrofibrosis-1, and sudeck‘s disease-1. Postoperatively, no further patellar dislocations were reported. All patients experienced a sensation of significantly improved knee stability resulting in higher levels of activity. Retropatellar pain as found in 34 knees preoperatively was better-24, unchanged-7, worse-6 (3 additional cases) after surgery. Positive apprehension sign, as preoperatively found in all patients, turned negative in all cases. Radiographically, osseous healing of the reconstructed trochlea was noted without evidence of subsequent arthrosis. MRI and knee arthroscopy including histological analysis of osteochondral biopsies did not provide any evidence for osteonecrosis or chondropathia.

Conclusion: Recurrent patellar dislocation due to femoral trochlear dysplasia can be treated successfully using the presented technique of trochleoplasty.

Introduction: The non-cemented, extramedullary anchored Thrust Plate Prosthesis (TPP) was conceived as an implant for younger people with osteoarthrosis of the hip. The proximal part of the femur is loaded as physiologically as possible by transmitting the hip joint force directly to the cortex of the femoral neck, enabling the bone stock in the proximal femur to be preserved.

Materials and methods: We prospectively followed-up 102 hip replacements radiologically and clinically in 84 patients (63 men and 21 women) with a mean follow-up time of nine years (6–12 years). The mean age at operation was 54 years for the men and 47 years for the women.

Results: Four implants were revised: two because of an infection and two because of aseptic loosening. In 85 implants major contact was maintained between the thrust plate and bone, in ten implants partial contact prevailed, and in only three instances did the bone retract from the thrust plate so that a gap appeared. The average Harris hip score (HHS) increased from 51 points preoperatively to 96 points postoperatively.

Conclusions: Our long-term results with the TPP are similar to those for conventional prostheses of the stem type. The detected radiological changes normally take place in the first two years after implantation. After the prosthesis is osseointegrated aseptic loosening of the prosthesis is very unlikely. Bone remodelling underneath the thrust plate is in 85% of the cases as expected from the biomechanical principles. These long-term results confirm our encouraging medium-term observations. The TPP is a prosthesis of first choice when revision might be expected, as in the case of younger patients.

Introduction: The Thrust Plate Prosthesis (TPP) was conceived with the aim of loading the proximal part of the femur as physiologically as possible by transmitting the hip joint force directly to the cortex of the femoral neck and, as an extramedullary anchored implant, to preserve bone stock in the proximal femur. Materials and methods: We prospectively followed-up 102 hip replacements radiologically and clinically in 84 patients (63 men and 21 women) with a mean follow-up time of 7 years. The mean age at operation was 54 years for the men and 47 years for the women. The indications for surgery were coxarthrosis 72%, idiopathic femoral head necrosis 11%, others 17%. Results: Four implants were revised: two because. Radiolgically in 85 implants major contact was maintained between thrust plate and bone, in 10 implants partial contact prevailed, and in only 3 instances did the bone retract from the thrust plate that a gap appeared. Conclusion: Our medium-term results with the TPP are similar to those for conventional prostheses of the stem type. Technical errors during implantation can lead to early failure of the implant. Bone remodelling in the vicinity of the thrust plate is in 85% of the cases as expected from the biomechanical principles. Occasionally, preferential load transfer through remodelled columns of high density trabeculae to the ribs just below the thrust plate, with corresponding retraction of cortical substance nearby, occurs. Revision of a TPP with replacement through one of conventional design is comparable to a primary intervention. The TPP is a prosthesis of the þrst choice when revision is expected.