[Cementless femoral neck prosthesis CUT--clinical and radiological results after 5 years]. / Die zementfreie Schenkelhalsprothese CUT--klinisch-radiologische Ergebnisse nach 5 Jahren.

AIM: With regard to total replacement of the hip, revision arthroplasty poses a challenge especially for younger patients. In spite of substantial improvements, new materials and operation techniques are still not able to prevent a shorter running life of prostheses in this group. The present work aims at evaluating clinical and radiological mid-term results of the femoral neck prosthesis CUT (ESKA Orthodynamics Lübeck) to answer the question of whether this implant is recommendable for younger patients. METHOD: Between 2001 and 2005 a consecutive series of 99 CUT prostheses was performed in 86 patients (50 female, 36 male) with a mean age of 50 (17-72) years and again evaluated clinically and radiologically after 5.4 (1.7-6.5) years. 84 cases were operated using a posterior approach and 15 cases were operated according to the anterolateral Watson-Jones approach. For clinical evaluation the Harris hip score and the visual analogue scale (VAS) for pain measurement were applied. Standard anteroposterior radiographs of the pelvis and lateral radiographs of the operated hip were compared to radiographs taken in the recovery room by two independent observers. Interobserver measurement discrepancy of the implant angle was 2.6 +/- 1.4 degrees. With 4 degrees being the maximum discrepancy, it was defined as the threshold of the normal range of 145 degrees (141-149 degrees). Additionally, the amount of femoral neck resection, the contact of the medial corticalis with the proximal stem, and the contact of the lateral corticalis with the distal part of the stem, periarticular ossifications and stable fixation by bone ingrowth according to Engh et al. were evaluated. Five delineated sections around the femoral component for evaluation of looseness or progressive loosening were used according to Gruen et al. Radiological evaluation of the cup was performed according to Charnley and DeLee. RESULTS: The survival rate according to Kaplan-Meier was 98 % after on average 6.6 years. The Harris hip score significantly improved from 50 (16-83) points preoperatively to 98 (40-100) points at the time of follow-up (p < or = 0.05). 82 % achieved an excellent result (91-100 points), 10% a good (91-90 points), 4% had a moderate (71-80 points) and 4% had a bad (< 70 points) result. Six prostheses had to be revised. One of them had to be changed to a cementless standard stem after 5 years because of aseptic loosening. Another one had to be revised after 2.7 years because of chronic thigh pain. Two painful hips had a capsular revision. In one case the liner had to be changed and one case had an exchange of the femoral ball for a better femoral offset. The VAS revealed a significant reduction of pain in rest and under load (p < or = 0.05). 92% had a correct subcapital neck resection. The recommended implant angle of 145 degrees was seen in 72% while a valgus alignment in 18% and a varus alignment in 10% was measured. Undersizing of the CUT-prosthesis was seen in 27 cases. Nine of these cases developed a varus alignment. Osseous integration of the cup and stem was seen in 100% and in 95%, respectively. CONCLUSION: This study demonstrates the CUT prosthesis as a bone-preserving prosthesis with good functional and radiological results and therefore as an alternative joint replacement in younger patients.

[The bipolar cup Avantage in hip revision surgery]. / Die bipolare Pfanne Avantage in der Hüftrevisionschirurgie.

BACKGROUND: Luxations in revision arthroplasty are a serious complication with an incidence of up to 30 percent. In particular in patients with previous operation and resection of bone and soft tissue, the instability increases significantly. The use of the bipolar revision cup Avantage has to be proven valuable to avoid recurrent luxation. METHODS AND PATIENTS: 27 consecutive revisions of the bipolar acetabular component were performed. The mean age at the time of revision was 67 years (range 40-91 years). The mean rate of previous operations was 5.1 cases (range 1-14). In 11 hips (40.7%) the acetabular cup was revised, in 16 hips (59.3%) an additional stem revision was performed. In 10 cases the revision was performed by a proximal femur reconstruction, in one patient by a total femur reconstruction. The follow-up was short-term, at a mean of 20 months (range 13-29 months). The clinical results were evaluated prospectively by the Harris hip score (HHS) and the activity score according to Sutherland (aSL). The migration of the cup and the change of the inclination angle were calculated radiographically. RESULTS: There has been one dislocation of the polyethylene liner in the recent follow-up, which could be treated conservatively by closed reduction. No patients required reoperation because of technical errors or loosening of the bipolar acetabular implant. The HHS improved from a mean of 40.5 (range 7-77.4) to 66.8 points (range 17.4-89.9). The modified Sutherland score improved to 5.9 (range 3-9) of 10 possible points. Radiographic follow-up revealed neither evidence of component loosening nor migration or polyethylene wear. CONCLUSION: Use of this bipolar unconstrained component was successful in restoring stability in hip revision arthroplasty, e.g., in patients with severely unstable hips. It has to be observed carefully if there are any disadvantages of these devices because of higher polyethylene wear in the mid- or long-term follow-up. The possible disadvantages of dissociations between the inner liner from the outer liner or damage of the polyethylene liner limits the indication of this device to serious revision cases.

Bone remodeling in proximal HA-coated versus uncoated cementless SL-Plus((R)) femoral components: a 5-year follow-up study.

BACKGROUND AND PURPOSE: Bone resorption at the femoral stem due to stress shielding has been particularly observed secondary to cementless hip replacement. This prospective study of 126 total-hip replacements was performed to examine clinical outcomes and changes in peri-prosthetic bone density after implantation of a double-tapered cementless femoral component manufactured with versus without hydroxyapatite (HA) coating. METHODS: Sixty-seven femoral components with and 59 femoral components without proximal HA coating were implanted and examined after a mean follow-up of 5.8 (SD 1.1, 2.8-7.8) years. The Harris hip score (HHS) and plain radiographs were used for clinical and radiological follow-up evaluations. Possible changes in peri-prosthetic bone mineral density (BMD) were measured by dual-energy X-ray absorptiometry (DEXA). RESULTS: Clinical outcome, measured by HHS, was similar in both groups. On plain radiographs, significantly less radiolucent lines were observed for the coated implants. DEXA revealed a significant increase in BMD at the proximal zones, along the medial side, and at the stem tips in the coated compared with the non-coated implants. INTERPRETATION: Hydroxyapatite-coated implants yield favorable radiographic characteristics, but no greater clinical benefit after 5 years' implantation.

Clinical and radiological mid-term results of the thrust plate prosthesis.

The purpose of this study was to perform an objective clinical and radiological assessment of the thrust plate prosthesis (TPP). Fifty-three prostheses were evaluated clinically using the Harris hip score (HHS), visual analog scale (VAS), and radiographically before surgery, at the time of discharge, and postoperatively after on average of 8.09 (range 4.61-9.93) years. The average HHS significantly (p < or = 0.05) improved from 48 (range 18-77) points to 95 (range 46-100) points. The VAS revealed significant (p < or = 0.05) reduction of pain at rest and under load. Radiographic analysis showed a considerable potential for osteolysis under the thrust plate. Sixteen prostheses revealed signs of radiolucent zones. In general, there was a good clinical outcome with no major limitations in function. Radiographic changes under the thrust plate indicate an adaptation processes resulting from changed biomechanics. This study suggests that the TPP could be a good alternative in total hip replacement in younger patients.

[The influence of reduced bone density on primary stability of cementless femoral stems. A biomechanical in vitro study]. / Der Einfluss der Knochendichte auf die Primärstabilität von zementfreien Femurschaftprothesen--Eine biomechanische In-vitro-Studie.

OBJECTIVE: The aim of the present in vitro study is to examine the influence of bone density on the primary stability of cementless femoral stems in nine pairs of human cadaveric femurs. METHOD: The human proximal femurs were evaluated with regard to their bone density by dual-energy X-ray absorptiometry. Two pairs of human cadaveric femurs had an osteoporotic and two pairs an osteopenic bone stock. After implantation of the cementless femoral stems, the prostheses were loaded in a physiological position. Subsidence, rotation and interface motion of the stems were measured with load cycles up to 2000 Newton. RESULTS: There was no significant correlation between the bone density of the proximal femur and the primary stability of the femoral stem in subsidence (p=0.23) and rotation (p=0.79). Reduced bone density in the osteoporotic and osteopenic human femora did not increase the interface motion at the proximal or distal part of the prosthesis (p>0.05). CONCLUSION: The initial stability of cementless femoral stems was not influenced by the bone density, at least in this biomechanical in vitro study. Thus, theoretical conditions exist that allow secondary osseointegration of femoral stems also in cases of reduced bone density.

[Chronic cobalt poisoning in endoprosthetic replacement]. / Chronische Kobaltvergiftung in der Endoprothetik. Ein Fallbericht.

This article outlines symptoms and therapeutic options in chronic cobalt poisoning including a case report in which metallosis caused by a ceramic-metal articular pairing led to almost complete loss of sight and hearing after revision of a total hip prosthesis. At primary revision the firmly incorporated stem was left in place. For a better offset only the head was exchanged from a ceramic to a metal model which articulated with a socket containing a ceramic inlay. Postoperatively, movement of the hip joint became increasingly uncomfortable and painful. After 2 years, the patient started complaining about increasing impairment of his eyesight followed by a gradual loss of hearing. In a second revision, examination of the explanted material showed almost complete deterioration of the metal femoral head and a partially fractured ceramic inlay with extensive contamination of the bone and surrounding soft tissue by metal debris. At the time of revision increasing concentrations of the alloy elements cobalt, chromium, and molybdenum were measured in the serum and liquor. The concentration of cobalt, in particular, was remarkably high. Treatment options in cases with chronic cobalt poisoning include chelation therapy with EDTA or BAL/DMPS.

Clinical and functional outcome of the Thrust Plate Prosthesis: short- and medium-term results.

OBJECTIVES: The purpose of this study was to objectively assess the functional outcome after implantation of a Thrust Plate Prosthesis. DESIGN: This retrospective study compared the gait patterns of 33 patients to a control group. BACKGROUND: Few studies have been published about this type of prosthesis describing clinical and radiographic outcome. Even though the evaluation of the functional outcome is a commonly accepted way to measure the success of an implant it has not been reported in previous studies. METHODS: Beside clinical (SF-36, and Harris Hip Score) and radiographic evaluation subjects were examined by three dimensional gait analysis and surface electromyography from seven leg and trunk muscles bilaterally. RESULTS: The average Harris Hip Score was 85.7 points, and the SF-36 only differed significantly from controls regarding physical functioning. The radiography showed considerable radiolucencies under the Thrust Plate. Kinematic parameters indicated a slight impairment of the operated limb. The analysis revealed a decreased hip (28.2%) and knee (51.2%) range of motion during gait. The joint moments on the operated side were reduced in hip (72%) and knee abduction (59%) in comparison to controls. The average electromyographic parameters indicated a significantly higher mean and peak amplitude of the tensor fasciae latae (mean 56%, peak 54%), and gluteus medius (mean 33%, peak 21%) and a lower peak activity of the gluteus maximus (19%). CONCLUSIONS: The results indicate a generally good functional outcome even though a slightly asymmetrical loading was observed. No major limitations in physical functioning and health-related quality of life was seen. The radiographic signs of loosening might indicate difficulties in achieving the proximal load transfer of this implant. RELEVANCE: The data provided in this study may serve to establish the Thrust Plate Prosthesis as an alternative procedure in total hip replacement in younger patients.