Quantitative measurements of adaptive bone remodeling around the cemented Zimmer® segmental stem after tumor resection arthroplasty using dual-energy x-ray absorptiometry.

BACKGROUND: Limb salvage surgery (LSS) is the preferred method for treatment of patients with sarcomas and to a greater extent also to patients with metastatic bone disease. The aim of the present study was to evaluate the adaptive remodeling of the periprosthetic cortical bone after insertion of a tumor prosthesis with cemented stem. METHODS: A prospective study of 21 patients (F/M = 12/9), mean age 55 years (range 15-81) with metastatic bone disease (n = 9), sarcomas (n = 8) or aggressive benign tumors (n = 4) who underwent bone resection due to a tumor, and reconstruction with a tumor-prosthesis (Zimmer® Segmental 130 mm straight fluted cemented stem with trabecular metal (TM) collars) in the proximal femur (n = 10), distal femur (n = 9) or proximal tibia (n = 2). Measurements of bone mineral density (BMD) (g/cm2) were done postoperatively and after 3, 6, and 12 months using dual-energy X-ray absorptiometry. BMD was measured in 4 regions of interest around the cemented stem and in one region of interest 1 cm proximal from the ankle joint of the affected limb and measurement of the contralateral ankle was used as reference. Repeated measures ANOVA and students paired t-test was used to evaluate BMD changes over time. RESULTS: At 1-year follow-up, BMD decreased compared to baseline in all four regions of interest with a statistically significant bone loss of 8-15%. The bone loss was most pronounced (14-15%) in the 2 regions of interest closest to the trabecular metal (TM) collar and lowest (8%) adjacent to the tip of the stem. CONCLUSION: After 1 year the decrease in bone mineral density of the ankle on the affected limb was 9% and the contralateral ankle was close to baseline, thus suggesting that the periprosthetic bone mineral density changes during follow-up, mainly are caused by stress shielding and immobilization. TRIAL REGISTRATION: The study was approved by the Scientific Ethical Committee of the Capital Region of Denmark (J. No. H-2-2014-105) and the Danish Data Protection Agency (J. No.: 2012-58-00004 ).

Preoperative BMD does not influence femoral stem subsidence of uncemented THA when the femoral T-score is > -2.5.

Background and purpose - It is believed that in uncemented primary total hip arthroplasty (THA) the anchorage of the stem is dependent on the level of bone mineral density (BMD) of the femoral bone. This is one of the reasons for the widely accepted agreement that a cemented solution should be selected for people with osteoporosis or age > 75 years. We evaluated whether preoperative BMD of the femur bone is related to femoral stem migration in uncemented THA.Patients and methods - We enrolled 62 patients (mean age 64 years (range 49-74), 34 males) scheduled for an uncemented THA. Before surgery we undertook DEXA scans of the proximal femur including calculation of the T- and Z-scores for the femoral neck. Evaluation of stem migration by radiostereometric analysis (RSA) was performed with 24 months of follow-up. In 56 patients both preoperative DEXA data and RSA data were available with 24 months of follow-up.Results - None of the patients had a T-score below -2.5. We found no statistically significant relationship between preoperative BMD and femoral stem subsidence after 3 or 24 months. When comparing the average femoral stem subsidence between 2 groups with T-score > -1 and T-score ≤ -1, respectively, we found no statistically significant difference after either 3 or 24 months when measured with RSA.Interpretation - In a cohort of people ≤ 75 years of age and with local femur T-score > -2.5 we found no relationship between preoperative BMD and postoperative femoral stem subsidence of a cementless THA.

Evaluation of different coatings of the tibial tray in uncemented total knee arthroplasty. A randomized controlled trial with 5 years follow-up with RSA and DEXA.

BACKGROUND: Regenerex® is a porous titanium construct with a 3D interconnecting pore structure and biomechanical characteristics close to that of normal trabecular bone. This study aimed to compare the Regenerex (VR) to the non-interconnecting pore structure Porous Plasma Spray (VP) on tibial implants for total knee arthroplasty (TKA) at 5 years. METHODS: We enrolled and randomized 61 patients (mean age = 63(49-71) years, Female/Male = 35/26) who were planned for an uncemented Vanguard TKA (Biomet, Warsaw, Indiana, USA) to receive either a VR or a VP coated tibial component (31/29). We performed radiostereometric analysis (RSA) and Dual Energy X-ray Absorptiometry (DEXA) postoperatively, and at three, six, 12, 24 and 60 months with measurements of migration. In total 55 patients attended the 5-year follow-up. RESULTS: One patient died and four were reoperated during the 60-months period; none due to aseptic loosening. All reoperations were in the VR-group. The mean (range) 60-months MTPM was 1.4 mm (0.5-3.7) for the VP-group and 1.8 mm (0.4-4.9) for the VR-group (p = 0.8). The 24 to 60-months mean (range) MTPM was -0.3 mm (-5 to 1.24) in the VP-group and 0.2 mm (-0.4 to 3.5) in the VR-group (p = 0.8). CONCLUSION: We did not find any statistically significant differences between the VP- and VR-group and both groups show recognizable migration. We will continue to follow the groups for years to come.

No difference for changes in BMD between two different cementless hip stem designs 2 years after THA.

This study evaluates how 2 different total hip arthroplasty (THA) stems compares regarding adaptive bone remodelling. The stems are both proximally porous coated, aiming for proximal fixation, but with different dispersal of the coating. They are also differently designed regarding the distal tip of the stem. We aimed to investigate if there is a difference in periprosthetic adaptive bone remodelling between two different designs. From February 2016 to September 2017, we randomised 62 patients, 1:1 (mean age = 64 years, Female/Male = 28/34), scheduled for an uncemented THA to receive either an EBM or a BM THA stem. We performed dual-energy x-ray absorptiometry (DEXA) scans within a week after surgery and at 3, 6, 12 and 24 months with measurements of bone mineral density (BMD) in the 7 Gruen zones (region of interest (ROI) 1-7). Additionally, Oxford Hip Score and Harris Hip Score were collected at 6, 12 and 24 months. We found a decrease in BMD between the postoperative and the 24-months values in all ROIs for both stems. The greatest decrease over time was seen for both groups in the ROI1 (BM = - 8.4%, p = 0.044, and EBM = - 6.5%, p = 0.001) and ROI7 (BM = - 7%, p = 0.005, and EBM = - 8.6%, p < 0.0005). We found a tendency in ROI2-4 of a higher degree of bone loss in the EBM group. However, this difference only continued beyond 6 months in ROI4 (24 months: BM = - 1.2% and EBM = - 2.8%, p = 0.001). The stems show similar adaptive bone remodelling and are clinically performing well.

Migration of the uncemented Echo Bi-Metric and Bi-Metric THA stems: a randomized controlled RSA study involving 62 patients with 24-month follow-up.

Background and purpose - Despite the good results after total hip arthroplasty (THA), new implants are continuously being developed to improve durability. The Echo Bi-Metric (EBM) THA stem is the successor to the Bi-Metric (BM) THA stem. The EBM stem includes many of the features of the BM stem, but minor changes in the design might improve the clinical performance. We compared the migration behavior with radiostereometric analysis (RSA) of the EBM stem and the BM stem at 24 months and evaluated the clinical outcome. Patients and methods - We randomized 62 patients with osteoarthritis (mean age 64 years, female/male 28/34) scheduled for an uncemented THA to receive either an EBM or a BM THA stem. We performed RSA within 1 week after surgery and at 3, 6, 12, and 24 months. The clinical outcome was evaluated using Harris Hip Score (HHS) and Oxford Hip Score (OHS). Results - At 24 months, we found no statistically significant differences in migration between the two implants. During the first 3 months both the EBM and the BM stems showed visible subsidence (2.5 mm and 2.2 mm respectively), and retroversion (2.5° and 2.2° respectively), but after 3 months this stabilized. The expected increase in HHS and OHS was similar between the groups. Interpretation - The EBM stem showed a migration at 24 months not different from the BM stem, and both stems display satisfying clinical results.

Observational study of a new modular femoral revision system.

BACKGROUND: The uncemented ArcosTM Modular Femoral Revision System (ARCOS) is a new comprehensive, press-fit revision design. The modular design offers a wide range of possible combinations to accommodate different variations of anatomy and bone stock. The ARCOS is made by a proximal body and a distal stem. As probably the only ones worldwide we predominantly use a combination of body and stem which supports proximal fixation and load, since this mimics the concept of the primary total hip arthroplasty with proximal weight-bearing, leading to bone stock preservation and no stress shielding or thigh pain. AIM: To evaluate the early results after femoral revision in a consecutive series of patients undergoing surgery over 3 years. METHODS: We included 116 patients in the study. They were operated in the period August 2011 to December 2014 and we got a clinical mean observation time of 4 (0.5-6) years. Clinical and radiographical follow-up included present function of the hip assessed by Harris Hip Score, Oxford Hip Score, and EQ5D (measure of health outcome). Of the 116 patients, 17 died in the interim and were consequently included only in the implant survivorship analysis; 46 patients attended the follow-up control. RESULTS: In total 6 (5%) hips were re-revised due to infection (n = 3), fracture (n = 2) or subsidence (n = 1). No patient was re-revised due to aseptic loosening. The 1-, 2- and 5-year probability of implant survival (95%CI) were 97% (93%-100%), 97% (93%-100%) and 96% (92%-99%), respectively. In this cohort 95 patients received a combination of a proximal broach and a distal curved and slotted stem (BS), aiming for proximal fixation and load bearing; 21 patients received a different combination. When comparing these two groups the BS-group had a 5-year implant survival probability (95%CI) of 97% (93%-100%) compared with the group of other combinations with a 5-year implant survival probability (95%CI) of 90% (78%-100%) (P = 0.3). Our regression analysis showed that periprosthetic fracture as an indication for the ARCOS operation was the only significant negative outcome predictor. The mean Harris Hip Score result (100 points being best) was 83 (range 5-98). The mean Oxford Hip Score result (48 points being best) was 40 (range 19-48). CONCLUSION: The early results of the ARCOS are promising compared with similar studies. We encourage the use of the BS combination whenever the bone stock proximally is adequate.