Ceramic coating improves tibial component fixation in total knee arthroplasty

Forty uncemented total knee arthroplasties (36 patients) were randomly allocated to a Miller-Galante II prosthesis with or without hydroxyapatite/tricalcium phosphate (HA/TCP) coating on the titanium fiber mesh on the undersurface of the tibial component. The patients were followed for 2 years with repeated radiostereometric examinations. After 2 years, the HA/TCP tibial components displayed smaller anterior-posterior tilt and less subsidence. The mean value of maximal total point motion was small: 0.5 mm in both groups. At 24 months, there were more radiolucent lines under the tibial tray and around the stem in the uncoated group, but the clinical results did not differ. HA/TCP coating on the undersurface of the tibial component improved the stability and seemed to improve the quality of the interface between the tibial component and the bone.     

Tibial component fixation in total knee arthroplasty: a comparison of pegged and stemmed designs

This study compares midterm radiographic, functional, and quality-of-life outcomes in patients receiving a cemented tibial component that has either a short intramedullary stem or one that has a pegged tibial component. A cohort of 181 patients received 225 NexGen cruciate-retaining implants (84 stemmed, 141 pegged) during total knee arthroplasty, with annual follow-up examinations for up to 7 years. Both types of tibial components were associated with excellent radiographic and clinical results with no radiographic evidence of implant loosening or osteolysis. Clinical outcomes included improvement in joint function and patient function, as well as quality of life. Survival analysis showed 98% survival at 7 years with both implants. Pegged tibial components offered comparable midterm radiographic, functional, and quality-of-life results to stemmed components.     

Wear measurements with use of radiostereometric analysis in total hip arthroplasty with obscured femoral head

Radiostereometric analysis (RSA) has evolved as gold standard in the evaluation of wear and especially as regards novel hip implant materials. However, several cup shell materials and articulation types used in total hip arthroplasty (THA) cannot be studied due to poor radiographic visibility of the femoral head (FH). We addressed this problem with use of a point transfer function in the RSA software to indirectly measure FH translations with use of stem markers. In a base examination, the stem marker segment and cup center, as an approximation for the FH center position, were mathematically coupled. Thereafter, in subsequent examinations, we used the point transfer function to calculate FH positions from stem marker positions. To determine the variance of the difference of directly and indirectly measured FH positions, four stem marker configurations were studied in THAs with radiographically visible FHs. For the axis with least variance we also compared directly and indirectly measured translation up to 7 years. Finally, we applied the method in a ceramic-on-ceramic (COC) articulation and measured proximal translation up to 7 years and also estimated precision. Vertical translations had the smallest variation between measured and calculated FH position. Directly and indirectly measured vertical FH translation correlated well but indirect measurements had increased variance. Proximal steady-state penetration rate in uncemented COC THA was −0.003 (SD 0.021) mm/year with 99% precision along the vertical axis measuring 0.34 mm. The point transfer function can be used to measure proximal FH penetration, but with less precision than direct RSA.     

Enhancing femoral cement fixation in total knee arthroplasty

Several factors have been shown to be associated with early development of radiolucent lines at the bone-cement interface in total knee arthroplasty (TKA). The posterior condylar surfaces, in particular, seem subject to poor cement technique, which could lead to early loosening. This study compares two cementation techniques in TKA, with respect to depth of cement penetration and radiolucency in the posterior condyles. All penetration depths were greater in group I (injected) versus group II (noninjected). Sixty-seven percent of group I showed penetration depths >1.5 mm compared with 23% of group II. No specimen in group I had gaps in the cement mantle on visual inspection or radiolucency on radiographic evaluation. No statistical differences, however, could be demonstrated between the two groups.     

Radiological evaluation of the femoral component fixed with interface bioactive bone cement in revision total hip arthroplasty

Thirty cases whose femoral side was operated with interface bioactive bone cement technique in revision total hip arthroplasty for aseptic loosening and followed for more than 6 years were evaluated. The present study includes 2 men and 28 women with an average age at operation of 60 years. Mean postoperative follow-up period was 9 years. Rerevision of femoral component was not found. Possible loosening was observed in 1 case, using the criteria of Harris. Among 21 cases whose cementing grade was assessed as B or C in postoperative x-ray, radiolucent line at bone-cement interface has disappeared before last follow-up in 11 cases. The present study revealed that the good result was obtained using the interface bioactive bone cement technique for reconstruction of aseptic femoral loosening.     

Tibial component in total knee arthroplasty: To cement or not to cement?

Loosening of the tibial component is a major cause of failure in total knee arthroplasty. Implant stability is a key element for achieving long term successful results and relies on the interplay of several factors which include the method of fixation, prosthesis design, surgical technique, bone quality and patient characteristics. The analysis of these aspects may provide some guidelines for the choice of fixation, but an ultimate solution of the problem can not be found in the past experience with total knee replacement. A better understanding of the biological and mechanical changes induced in bone tissue by the joint disease as well as by the prosthesis, will probably allow us to adopt the most appropriate solution for every patient.      

In vivo determination of total knee arthroplasty kinematics: a multicenter analysis of an asymmetrical posterior cruciate retaining total knee arthroplasty

The objective of this study was to determine if consistent posterior femoral rollback of an asymmetrical posterior cruciate retaining (PCR) total knee arthroplasty was mostly influenced by the implant design, surgical technique, or presence of a well-functioning posterior cruciate ligament (PCL). Three-dimensional femorotibial kinematics was determined for 80 subjects implanted by 3 surgeons, and each subject was evaluated under fluoroscopic surveillance during a deep knee bend. All subjects in this present study having an intact PCL had a well-functioning PCR knee and experienced normal kinematic patterns, although less in magnitude than the normal knee. In addition, a surprising finding was that, on average, subjects without a PCL still achieved posterior femoral rollback from full extension to maximum knee flexion. The findings in this study revealed that implant design did contribute to the normal kinematics demonstrated by subjects having this asymmetrical PCR total knee arthroplasty.     

Tibial tubercle osteotomy in total knee arthroplasty surgery

Tibial tubercle osteotomy (TTO) is a recognized technique for improving exposure when performing total knee arthroplasty surgery. Forty-two patients were reviewed at a mean of 8 years after TTO. Preoperatively, mean extension was 8 degrees +/- 14 degrees , mean flexion 74 degrees +/- 30 degrees , and Knee Society score 73 +/- 37. At latest follow-up, mean extension was 4 degrees +/- 15 degrees , mean flexion 91 degrees +/- 22 degrees , and Knee Society score 124 +/- 42.6 (P < or = .0001). Seventy-three percent of patients had an excellent/good score at latest follow-up. Twenty-five percent of patients experienced no extensor lag, and 66% of extensor lags had resolved within 6 months. Mean time for osteotomy union was 14 weeks. In this series, TTO performed to enhance surgical exposure did not adversely affect the outcome after total knee arthroplasty but resulted in serious complications in 5% of patients.     

A prospective outcomes analysis of femoral component fixation in revision total hip arthroplasty

A prospective, surgeon-allocated, matched cohort analysis of patient outcomes compared cementless, modular metaphyseal and cemented femoral fixation used for revision total hip arthroplasty. First-time femoral revision operations (with and without acetabular revision) with Paprosky types I and II femoral bone stock were included. This series of 86 patients was matched for age, weight, diagnosis, Charnley class, Demand category, femoral bone stock, and outcome measures. At 8-year average follow-up (range, 4-13 years), there were no significant differences in visual analog pain scores (VAPS), Harris Hip Scores (HSS), and SF-36 Physical Function and Bodily Pain scores. One femoral rerevision (2.3%) occurred in the cementless group, and 2 (4.6%) occurred in the cemented group (P = .557). Five-year survivorship for femoral rerevision was 94% for patients with cementless, modular metaphyseal fixation and 92% for patients with cemented fixation. In this study, cementless, modular metaphyseal fixation and cemented femoral fixation were both successful at intermediate-term follow-up in Paprosky types I and II femoral bone (level of evidence: therapeutic study; level II, prospective comparative study).     

Tourniquet application only during cement fixation in total knee arthroplasty: a double-blind, randomized controlled trial

Background: The functional benefits of tourniquet application for short periods compared with standard duration applications during total knee arthroplasty surgery have not been well explored. We aimed to compare functional outcomes between tourniquet application of short duration (during cement fixation only) and tourniquet application of longer duration (from skin incision to just after cement fixation). Methods: We planned to randomize 230 patients to short and long duration groups. The primary outcome was Oxford Knee Score at 10 weeks post‐surgery. In‐hospital blood transfusion rate was also a primary safety measure. Serial measures of knee function were taken together with knee range, quadriceps lag and timed stair tests. Results: The trial was discontinued after randomization of 65 patients. Interim analysis indicated a higher risk of transfusion (odds ratio 7.38, P= 0.015) in the short duration group. No significant difference was observed in Oxford Knee Score at 10 weeks. There were no between‐group differences in rate of recovery up to 52 weeks for any outcome. Conclusions: Restricting tourniquet application to the period of cementing is associated with a significantly higher risk of transfusion. This approach is impractical if it is not offset by gains in functional recovery.     

Financial impact of a capitation matrix system on total knee and total hip arthroplasty

Total hip and total knee arthroplasty are high-volume surgical procedures that have a substantial economic impact for the healthcare system. This study analyzes the financial effect of a capitation matrix system on total knee and total hip implant costs over a 1-year period at a community hospital system. The matrix implant levels were based on implant characteristics, correlating increased technological sophistication of the various implants with increased but capitated payment to vendors. In the first year after the implementation of the matrix system, implant costs for the hospital decreased by 26.1% per implant for 369 total hip procedures and also by 26.1% per implant for 934 total knee procedures.     

Assessment of thermal damage in total knee arthroplasty using an osteocyte injury model

Polymethylmethacrylate bone cement has been widely used for the anchorage of artificial implants in various orthopedic surgeries. Although it is one of the most successful biomaterials in use, excess heat generation intrinsically causes thermal damage to bone cells adjacent to the bone cement. To estimate a risk of thermal injury, a response of bone cells to cement polymerization must be elucidated because of the occurrence of thermal damage. Thermal damage is affected not only by maximal temperature but also by exposure time, temperature history, and cell type. This study aimed at quantifying the thermal tolerance of bone cells for the development of a thermal injury model, and applying this model for the estimation of thermal damage during cement polymerization in total knee arthroplasty. Osteocytes, osteoblasts, and fibroblasts were respectively subjected to steady supraphysiological temperatures ranging from 45 to 50°C. Survival curves of each cell and temperatures were used to formulate the Arrhenius model. A three‐dimensional heat conduction analysis for total knee arthroplasty was conducted using the finite element model based on serial CT images of human knee. A maximal temperature rise of 50°C was observed at the interface between the 3‐mm thick cement and the tissue immediately beneath the tibial tray of the prosthesis. The probability of thermal damage to the osteocyte, which was calculated using the Arrhenius model, was negligible at a distance of at least 1 mm away from the cement–bone interface. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2799–2807, 2017.

     

Hybrid component fixation in total knee arthroplasty: minimum of 10-year follow-up study

Hybrid total knee arthroplasty (TKA) (uncemented femur with cemented tibia and patella) was introduced in the late 1980s to gain the theoretical advantage of durable cementless femoral fixation while avoiding the problems noted with cementless tibial fixation. From December 1992 to July 2000, 215 patients (235 knees) who underwent hybrid TKA were enrolled in this study. Five types of prosthesis (AGC, Maxim, LCS-M, LCS-APG, and Scorpio) were used. Revision rate for aseptic loosening was 16 (6.8%) of 235 knees. At 10 and 15 years, survivorship with tibial or femoral revision as the end point was 0.95 and 0.92, respectively. Hybrid TKA provides durable fixation with clinical and radiographic performance at minimum 10 years comparable with cemented series.     

Total knee arthroplasty component templating: a predictive model

Preoperative planning is essential to total knee arthroplasty (TKA); however, TKA templating is historically inaccurate. To improve on templating accuracy and streamline preoperative planning, we set out to predict component sizes based on patient characteristics without radiographs. A total of 123 consecutive patients undergoing unilateral TKA were identified and included in the model study. Input variables consisted of age, gender (as a binary number), height, weight, and body mass index. A linear regression model was created. The models predicted component size exactly in 74% of femurs and 85% of tibias. All model predictions were within a ±1 size of the actual components implanted. Our models were more accurate than any previous model for TKA reported.     

Effects of simvastatin on osseointegration in a canine total hip arthroplasty model: an experimental study

Simvastatin was recently demonstrated to stimulate bone morphogenetic protein-2 expression, leading to bone formation. The present study was designed to evaluate whether simvastatin administered by injection could promote osseointegration in a canine total hip arthroplasty model. Fifteen dogs were divided into 3 groups of 5 dogs each: group 1 (high-dosage simvastatin, 6.0 mg/[kg d]), group 2 (low-dosage simvastatin, 3.0 mg/[kg d]), and a control group (isotonic saline, 3.0 mg/[kg d]). Osseointegration was assessed by using the push-out test, scanning electron microscopy, energy-dispersive spectrometer microanalysis, and histomorphometric examination. The results showed higher mechanical strength, greater area of bone covering the femoral component, and higher bone-implant contact in group 1 than in the other 2 groups. Our findings indicate that simvastatin administered by injection could contribute significantly to osseointegration in a canine total hip arthroplasty model.     

Hypersensitivity to benzoyl peroxide in a cemented total knee arthroplasty: cement allergy

A small but significant proportion of cemented total knee arthroplasties develop aseptic loosening. Polyethylene debris is unlikely to be the cause in the small subgroup that experiences early loosening. Allergy to polymethylmethacrylate bone cement or its constituents has been reported in several different industries and in dentistry, dermatology, and joint arthroplasty. Although allergy to polymethylmethacrylate bone cement or its constituents is unusual, the possibility of a systemic inflammatory response and consequent pain and loosening must be considered. We report a case history of a patient who developed a systemic reaction and intractable pain after a total knee arthroplasty who was subsequently shown to be hypersensitive to the benzoyl peroxide component of bone cement.     

Osteoarthritis knee with patellar fracture in the elderly: single-stage fixation and total knee arthroplasty

Periarticular fractures that occur in a previously osteoarthritic knee, especially in an elderly patient, will be associated with other comorbidities and is a treatment challenge. Early mobilization is a key treatment principle in the geriatric population. We present a case report of an elderly diabetic patient with osteoarthritis of the knee joint who sustained a patellar fracture and was treated with single-stage primary total knee arthroplasty and fixation of the patellar fracture.     

An articulated antibiotic spacer used for infected total knee arthroplasty: a comparative in vitro elution study of Simplex and Palacos bone cements.

For the staged management of infected total knee arthroplasty (TKA), antibiotic laden polymethylmethacrylate (PMMA) spacers have been recommended. Antibiotic-impregnated PMMA spacers target drug delivery, achieving high local levels while limiting the potential for host toxicity associated with parenteral antimicrobial therapy. This study examined the elution characteristics of an articulating PMMA TKA spacer that has been useful clinically. Tobramycin and vancomycin are both active against many organisms leading to joint infections. We used various combined antibiotic concentrations (maintaining a relative ratio of 55% tobramycin to 45% vancomycin w/w), and then assayed the elution profile of the TKA spacer in vitro. Additionally, the elution qualities of two brands of bone cement, Simplex and Palacos, were compared. Briefly, three groups of PMMA spacers, impregnated with different antibiotic loads, were fashioned from a mold replicating a femoral TKA component. The entire spacer surface area was immersed in sterile phosphate buffered saline (PBS) in a 1:6 ratio of grams of cement to milliliters of PBS and incubated at 37 degrees C for 24 h. After 24 h, aliquot eluates were taken, the PBS discarded, and replaced with fresh, sterile PBS. PBS was changed daily and an aliquot was taken at least weekly for nine weeks. Eluate samples were stored at -70 degrees C until assayed. Each spacer eluate sample's antibiotic concentration was determined by disc diffusion bioassay against Bacillus subtilis. Mean zone inhibition diameters were extrapolated from the standard curve to yield micrograms per milliliter of antibiotic in PBS. In all groups the Palacos spacers demonstrated higher elution levels, above the MIC for the organism used, for a longer period of time than those made with Simplex. Based on the observed elution profiles, antibiotic-impregnated Palacos bone cement may offer a more effective vehicle for local drug delivery during staged treatment of infected TKA.     

Fracture of the femoral component in unicompartmental total knee arthroplasty

A fracture of the anterior flange of a femoral component in a unicompartmental knee has been seen. This was thought to be due to lack of bony support leading to cantilever bend. The solution would seem to be to add a metal web to strengthen that area of the femoral component.     

Effect of bioactive coating of the tibial component on migration pattern in uncemented total knee arthroplasty: a randomized RSA study of 14 knees presented according to new RSA-guidelines

Background  Bioactive coating of uncemented total knee arthroplasty (TKA) is believed to increase bone ingrowth and enhance early fixation of the TKA. In a prospective randomized study using radiostereometric analysis (RSA) we examined migrations of the tibial implant, in an uncemented TKA with and without bioactive coating. The study was performed according to new RSA guidelines, and focus was put on some important methodological issues. Materials and methods  Twenty-three patients with osteoarthrosis of the knee received an uncemented Duracon TKA either with bioactive (hydroxyapatite or periapatite) coating (+HA) or without bioactive coating (−HA). Patients had RSA examinations postoperatively and at 3, 6 and 12 months. Nine patients were excluded during the study resulting in 14 knees for final analysis. Results  At 12 months follow-up we found no significant differences in migrations between the two groups. However, in general the −HA group migrated more than the +HA group, and we found a significant larger variation in migration pattern in the −HA group. In the +HA group the tibia component stabilized after 6 months, whereas the −HA group showed continuous migration. Subsidence and posterior tilt were the main migration patterns in both groups. Conclusions  Bioactive coating of TKA seems to enhance early stabilization of the tibia component. Similar results are found in previous studies.