Posterior stabilized component increased femoral bone loss after total knee replacement. 5-year follow-up of 47 knees using dual energy X-ray absorptiometry.

After total knee replacement (TKR) bone mineral density (BMD) commonly decreases behind the anterior flange of the femoral component, which may increase the risk for supracondylar fracture. Our aim was to evaluate if changes in femoral design and joint area constraint had any effect on the postoperative bone remodeling in the distal femur. We used dual-energy X-ray absorptiometry in 47 knees up to 5 years after operation with the AMK (DePuy, Johnson and Johnson Leeds, UK) TKR. The knees had been randomly allocated to receive a flat or a concave tibial insert with retention of the posterior cruciate ligament when preoperative deformity was less severe, and either a concave or a posterior-stabilized (PS) insert with resection of the posterior cruciate ligament when deformity was more pronounced. The most pronounced relative reduction (15-38%) in bone mineral density (BMD) was seen posterior to the anterior flange. There were no significant differences in relative change in BMD between flat and concave inserts. Knees operated with PS inserts had more reduction posterior to the flange than knees with concave inserts in the subgroup with more advanced preoperative deformity (23% and 38% respectively). Use of posterior stabilized insert may increase the risk of supracondylar fracture compared to concave insert in knees with advanced preoperative deformity.

Influence of polyethylene constraint on tibial component fixation in total knee arthroplasty: follow-up report after 5 years.

The influence of articulating surface design of AMK total knee prosthesis (DePuy, Johnson & Johnson) on migration and radiographic outcome at 5 years was evaluated. The knees were randomly allocated to receive a flat or a concave insert with retention of the posterior cruciate ligament when preoperative deformity was less severe and either a concave or a posterior-stabilized insert with resection of the posterior cruciate ligament when deformity was more pronounced. In 64 knees, migration was measured with radiostereometry. The posterior-stabilized component displayed more varus-valgus tilting than the concave insert. Other statistically significant differences in migration were not seen. Radiolucent lines were frequently seen without differences between prosthesis groups.

Stepwise introduction of a bone-conserving osseointegrated hip arthroplasty using RSA and a randomized study: I. Preliminary investigations--52 patients followed for 3 years.

BACKGROUND: We developed a total hip system using osseointegration guidelines, a metaphyseal-loading proximal femoral replacement in the retained neck and a dual-geometry titanium shell in the acetabulum. PATIENTS AND METHODS: A randomized controlled clinical trial was undertaken in 52 patients (53 hips), using the cemented Spectron stem and cementless Harris-Galante II cup as control implants (24 patients in experimental group, 29 control patients). Clinical measures of Harris Hip Score (HHS), pain score and radiostereometric analysis (RSA) at regular intervals for up to three years were used to monitor progress. RESULTS: No statistically significant differences were found in HHS and pain score; the stability of the cementless experimental implant was also comparable to that of the cemented controls by RSA. 3 revisions were required for migration in the experimental group and 1 was required for component dislocation in the control group. INTERPRETATION: Our findings indicate the practicality of osseointegration of titanium implants, but suggest that current performance is inadequate for clinical introduction. However, the stable fixation achieved in the retained neck in the majority of patients is indicative of osseointegration. This finding will encourage technical and design improvements for enhancement of clinical osseointegration and should also encourage further study. Periprosthetic osteolysis might be avoided by the establishment and maintenance of direct implant-bone connection: "osseointegration".

Stepwise introduction of a bone-conserving osseointegrated hip arthroplasty using RSA and a randomized study: II. Clinical proof of concept--40 patients followed for 2 years.

BACKGROUND: We have developed a bone-conserving commercially pure titanium hip replacement system using osseointegration principles: a metaphyseal loading proximal femoral component affixing into the retained neck and metaphysis only, leaving the femoral canal untouched. The acetabular cup closely fits a dual-geometry cavity, avoiding stress protection at the dome. PATIENTS AND METHODS: After extensive laboratory and clinical pilot trial investigations, the surface-engineered implants were submitted to a prospective randomized controlled clinical trial involving 40 patients (40 hips), in which they were compared to the cemented Spectron femoral component and cementless Trilogy cup as control implant. The following clinical measures were used to monitor progress at regular intervals for the first 2 postoperative years: radiostereometric analysis (RSA), Harris Hip Score, pain score, WOMAC, and SF-36. RESULTS: After 2 years of follow-up, no statistically significant differences were seen between the groups concerning rotation or translation along the cardinal axes. The patients receiving the Gothenburg osseointegrated titanium (GOT) system had significantly higher Harris Hip Score at 6 months, suggesting more rapid recovery. WOMAC, SF-36 and pain analysis were similar for the first 2 postoperative years. INTERPRETATION: Our RSA data suggest that osseointegration was achieved for all patients receiving the GOT hip system. This bone-conserving prosthesis may provide a good alternative, especially for young and active patients.

Minimally invasive surgery vs conventional exposure using the Miller-Galante unicompartmental knee arthroplasty: a randomized radiostereometric study.

Forty-one patients were randomized to a cemented Miller-Galante unicompartmental (Zimmer, Warsaw, Ind) knee arthroplasty inserted with either minimally invasive surgery or with a standard exposure. Clinical data and conventional radiographs were recorded and patients were followed with radiostereometric analysis to measure migration rate of the tibial component. The rehabilitation of patients operated through a small incision was faster, and there was a significant difference in days of hospitalization (P = .03). No statistical significant difference was found between the 2 groups regarding clinical or radiographic data. The Hospital for Special Surgery score was 96 and 92, respectively, for the minimally invasive surgery and conventional group at 2 years. The limb alignment was equal in both groups with a mean femorotibial axis of 182 degrees after surgery. The rate of migration for tibial components was very small, with a maximal total point motion of 0.8 mm for both groups after 2 years follow-up.

All-polyethylene vs. metal-backed tibial component in total knee arthroplasty-a randomized RSA study comparing early fixation of horizontally and completely cemented tibial components: part 1. Horizontally cemented components: AP better fixated than MB.

BACKGROUND: Controversy still exists as to whether to mount the tibial bearing on a metal baseplate or not. Furthermore, the tibial component can be either horizontally or completely cemented. We evaluated metal backing versus all-polyethylene using horizontal cementing technique. PATIENTS AND METHODS: We randomized 40 patients with knee arthrosis (40 knees) to 2 groups: cemented total knee arthroplasty (AGC, Biomet) using either all-polyethylene (AP) or metal-backed (MB) tibial components (n = 20 for each group). All tibial implants had a total thickness of 8 mm. We used proximal cement-ing, including only the horizontal part of the tibia with avoidance of the stem-bone interface. RESULTS: The positioning of the implants, as judged by the HKA angle, showed an average neutral alignment in both groups. Preoperatively and after 2 years, there was no statistically significant difference between the HSS scores in both groups (p = 0.6 and 0.4). After 2 years, the metal-backed components had rotated more around the longitudinal axis, median 0.5 degrees vs. 0.2 degrees (internal or external rotation, p = 0.002), and showed increased maximum total point motion, median 1.0 vs. 0.4 mm (maximum migration or MTPM, p = 0.003). INTERPRETATION: Our study indicates that better fixation can be obtained with the all-polyethylene design if proximally cemented thin components are used.

All-polyethylene vs. metal-backed tibial component in total knee arthroplasty-a randomized RSA study comparing early fixation of horizontally and completely cemented tibial components: part 2. Completely cemented components: MB not superior to AP components.

BACKGROUND: Uncertainty exists as to whether metal backing (MB) of the tibial component is better than an all-polyethylene component (AP). This is valid for both horizontally and completely cemented components. We evaluated completely cemented MB vs. AP (Part 2). PATIENTS AND METHODS: In a randomized study, 39 patients (40 knees) with knee arthrosis were operated with cemented low-conforming total knee arthroplasty (AGC, Biomet) with a tibial component of uniform thickness (8 mm), cemented both beneath the tibial tray and around the stem. 20 patients had an all-polyethylene (AP) tibial component and 20 patients had an identical but metal-backed (MB) tibial component. We used clinical examination and radiostereometric analysis (RSA) to evaluate the hypothesis that MB improves component fixation. Fixation was evaluated using RSA up to 2 years after surgery. Clinical assessment was performed preoperatively and after 2 years using the Hospital for Special Surgeons (HSS) score. RESULTS: We found no differences in micromotion, and no differences in clinical scores could be detected between the groups at any time point. INTERPRETATION: Our findings indicate that there was equal initial fixation of the AP and MB stemmed monobloc components when they were cemented beneath the tibial plateau and around the stem.

Long-term results of a cementless knee prosthesis with a metal-backed patellar component: clinical and radiological follow-up with histology from retrieved components.

Aseptic loosening of cemented knee arthroplasties has encouraged development of uncemented fixation. The Miller-Galante I (MG I) prosthesis was designed to achieve permanent stability through ingrowth into a titanium fiber mesh. Thirty-five knees in 30 patients with MG I knee replacements have been followed clinically and radiologically with a mean follow-up of 12 years. Twenty knees were revised with a mean follow-up of 5 years. Patellofemoral problems, especially avulsion of the polyethylene from the metal-backed patella and in some cases severe metallosis, have been the main reason for revision. Metal-backed patellar component should be avoided. In addition, instability has been a problem. However, the fixation of the components has been excellent, with a high degree of osseous ingrowth displayed at histological analysis of retrieved components. The clinical and radiological results after revision are in most cases good, despite the femoral component having been left in situ.

Kinematics of three variations of the Freeman-Samuelson total knee prosthesis.

The effect of changes in the articulating surfaces on the kinematics of the Freeman-Samuelson total knee replacement was evaluated. Twenty-two patients (22 knees) (median age, 69 years) were randomized to a standard design with a fixed polyethylene bearing, a design with a mobile bearing, or a new design with a spherical medial femoral condyle with a fixed bearing. The patients were studied with radiostereometry and film-exchangers at 0 degrees nonweightbearing and during active weightbearing extension from 45 degrees to 15 degrees. The center of the tibial tray with a mobile-bearing prosthesis occupied a more anterior position than observed in the designs with a fixed bearing. The medial femoral condyle center had a more posterior position in the standard design than in the design with a spherical medial condyle. From a distally displaced position at 45 degrees, the medial condylar center displaced a mean of 1.8 mm proximally during extension in the standard design and had a constant position in the meniscal design. In the spherical design the medial condyle was displaced proximally at 45 degrees and displaced a mean of 1.6 mm distally during extension. The reduced anteroposterior and proximodistal translations in the meniscal design are compatible with improved congruency between the components. The design with a spherical medial condyle stabilized anteroposterior motions, but showed more pronounced proximodistal displacement medially than did the other two designs.