Individualized metal implants for focal cartilage lesions in the knee can be cost-effective: A simulation on 47-year-old in a Swedish setting.

OBJECTIVES: In the aging population, the knee is the joint most commonly causing impaired function and incapacity. While definite treatment by prosthetic replacement is often performed late, symptomatic knee cartilage lesions cause much suffering also in younger ages. Early intervention could, therefore, be instituted at an early stage to the benefit of both patients and society. Small, metal surface, resurfacing implants have been tested with promising results. A system that features patient-specific implants and surgical instruments shows good clinical results and favorable survival rates. This study aims to assess the cost utility of this metal device compared with microfracture (MFX), being the standard procedure in Sweden. METHODS: We constructed a simulation model in Excel. In the model, a cohort of 47-year-old patients (which is the mean age of patients treated with the metal implant) with symptomatic knee cartilage lesions received either MFX or metal implantation. Outcomes for the cohort were simulated over 40 years, such as in a previously published model based on MFX, and sensitivity analyses (deterministic and probabilistic) of the results were undertaken. Data on transition probabilities, costs, and quality of life were taken from clinical data, published literature, and official price lists. Only direct medical costs were included. RESULTS: Results from the analysis showed that the metal device is a cost-effective treatment strategy compared with MFX. The incremental cost-effectiveness ratio (ICER) reached acceptable levels at ∼5 years postoperatively. Over the full-time horizon of 40 years, the metal device was cost saving with concomitant gains in quality-adjusted life years (QALYs), translating to a dominant treatment strategy. Results were robust according to sensitivity analysis with the initial success rate of up to three years for both metal and MFX having the largest impact. CONCLUSIONS: A metal implant may be a cost-effective treatment alternative for patients in their 40's when compared to MFX in a Swedish setting. LEVEL OF EVIDENCE: 5 [1].

Patient-Specific Implants for Focal Cartilage Lesions in The Knee: Implant Survivorship Analysis up to Seven Years Post-Implantation.

In the quest for increased surgical precision and improved joint kinematics, Computer-Assisted Orthopedic Surgery (CAOS) shows promising results for both total and partial joint replacement. In the knee, computer-assisted joint design can now be applied to the treatment of younger patients suffering pain and restriction of activity due to focal defects in their femoral articular cartilage. By taking MRI scans of the affected knee and digitally segmenting these scans, we can identify and map focal defects in cartilage and bone. Metallic implants matched to the defect can be fabricated, and guide instrumentation to ensure proper implant alignment and depth of recession in the surrounding cartilage can be designed from segmented MRI scans. Beginning in 2012, a series of 682 patient-specific implants were designed based on MRI analysis of femoral cartilage focal defects, and implanted in 612 knees. A Kaplan-Meier analysis found a cumulative survivorship of 96% at 7-year follow-up from the first implantation. Fourteen (2.3%) of these implants required revision due to disease progression, incorrect implant positioning, and inadequate lesion coverage at the time of surgery. These survivorship data compare favorably with all other modes of treatment for femoral focal cartilage lesions and support the use of patient-specific implants designed from segmented MRI scans in these cases.

Treatment of osteochondral defects: chondrointegration of metal implants improves after hydroxyapatite coating.

PURPOSE: The treatment of osteochondral defects in joint cartilage remains challenging due to its limited repair capacity. This study presents a metallic osteochondral plug with hydroxyapatite (HA)-coated cap edges for improved implant-tissue contact. The hypothesis was that improved attachment prevents from synovial fluid-influx and thereby avoids osteolysis and resulting implant instability. METHODS: In total, 24 female, adult sheep were randomized into three groups. All animals received an Episealer®-implant in the medial condyle of the right knee. The implants were coated with two different HA versions or uncoated (control group). After 12 weeks, the implant-tissue connections were analysed radiologically and histologically. RESULTS: In general, the groups with the coated cap edges showed a better quality of tissue connection to the implant. The occurrence of gaps between tissue and implant was more seldom, the binding of calcified and hyaline cartilage to the cap was significantly better than in the uncoated group. A histomorphometrically measured lower amount of void space in these groups compared to the group with the uncoated edges confirmed that. CONCLUSIONS: The hypothesis of a tighter cartilage bone contact was confirmed. The HA coating of the implant's cap edges resulted in better adherence of cartilage to the implant, which was not previously reported. In conclusion, this led to a better contact between implant and cartilage as well as neighbouring bone. In clinical routine, joint fluid is aggressive, penetrates through cartilage rifts, and promotes osteolysis and loosening of implants. The observed sealing effect will act to prevent joint fluid to get access to the implant-tissue interfaces. Joint fluid is aggressive, can cause osteolysis, and can, clinically cause pain. These effects are liable to decrease with these findings and will further the longevity of these osteochondral implants.

No implant migration and good subjective outcome of a novel customized femoral resurfacing metal implant for focal chondral lesions.

PURPOSE: Managing focal cartilage injuries in the middle-aged patient poses a challenge. Focal prosthetic inlay resurfacing has been proposed to be a bridge between biologics and conventional joint arthroplasty. Patient selection and accurate implant positioning is crucial to avoid increased contact pressure to the opposite cartilage surface. A customized femoral condyle implant for focal cartilage injuries was designed to precisely fit each patient's individual size and location of damage. The primary objective was to assess implant safety profile, surgical usability of the implant and instruments, and implant migration with radiostereometric analysis (RSA). METHODS: Ten patients 36-56 years with focal chondral defects, ICRS 3-4 of the femoral cartilage and failed earlier conservative or surgical interventions with VAS pain > 40. The patients were followed for 2 years with subjective outcome measures (VAS, EQ5D, KOOS) and RSA. The customized implant and guide instruments were manufactured by computer-aided design/computer-aided manufacturing (CAD/CAM) techniques using MRI data. RESULTS: VAS, EQ5D and KOOS showed improvements that reached significance for VAS (p ≤ 0.001), Tegner (p = 0.034) and the KOOS subscores ADL (p = 0.0048), sport and recreation (p = 0.034) and quality of life (p = 0.037). VAS and KOOS scores improved gradually at 3, 6 and 12 months. The improvements in EQ5D, KOOS pain and KOOS symptoms did not reach statistical significance. No infections, deep venous thrombosis or other complications occured in the postoperative period. No radiographic signs of damage to the opposing tibial cartilage was noted. The surgical usability of implants and instruments were good. RSA did not show any implant migration. CONCLUSION: This is the first clinical report of a new customized, focal knee resurfacing system. The short-term implant safety and patient-related outcome measures showed good-to-excellent results. LEVEL OF EVIDENCE: Prospective case series, Level 4.

Changing caring behaviours in rehabilitation after a hip fracture - A tool for empowerment?

Different rehabilitation programs after surgery have been presented to improve the outcome for patients with a hip fracture. Empowerment has been suggested as useful, but requires a change in the caring behaviours of health professionals. The aim with this study was to evaluate if training and supervision of the nursing staff could alter caring behaviours. A case-control study of nursing staff treating hip fracture patients was performed at a hospital with two sites. Training and supervision was given to the nursing staff at the intervention site. The intervention focused on creating positive care interaction by using eight guidelines. The evaluation was performed with recordings of a constructed caring situation before training, and observations of care situations at the ward before and after intervention. The results showed no differences at baseline between the two sites in the caring behaviours. After intervention, significant effects of caring behaviours were seen in seven out of eight guidelines, the effect sizes ranged from medium to large. The findings indicate that the nursing staff can change caring behaviours and facilitate the empowerment of patients with a hip fracture.

A randomized RSA study concentrating especially on continuous migration.

Background and purpose - There is a general call for phased introduction of new implants, and one step in the introduction is an early evaluation of micromotion. We compared the micromotion in the Triathlon and its predecessor, the Duracon total knee prosthesis, concentrating especially on continuous migration over 5 years of follow-up. Patients and methods - 60 patients were randomized to receive either a cemented Triathlon total knee prosthesis or a cemented Duracon total knee prosthesis. 3-D tibial component migration was measured by radiostereometric analysis (RSA) at 3 months and at 1, 2, and 5 years. Results - There was no statistically significant difference in maximum total point motion (MTPM) between the 2 groups (p = 0.1). The mean MTPM at 5 years for the Duracon was 1.10 (SD 1.21) mm and for the Triathlon it was 0.66 (SD 0.38) mm. The numbers of continuously migrating prostheses were similar in the groups at the fifth year of follow-up; 6 of 21 prostheses in the Duracon group and 3 of 21 in the Triathlon group had migrated more than 0.3 mm between the second year and the fifth year of follow-up (p = 0.2). Interpretation - The Triathlon has a micromotion pattern similar to that of the Duracon total knee system at both short-term and medium-term follow-up, and may therefore, over time, show the same good long-term mechanical stability.

Pre-Osteoarthritis: Definition and Diagnosis of an Elusive Clinical Entity.

OBJECTIVE: An attempt to define pre-osteoarthritis (OA) versus early OA and definitive osteoarthritis. METHODS: A group of specialists in the field of cartilage science and treatment was formed to consider the nature of OA onset and its possible diagnosis. RESULTS: Late-stage OA, necessitating total joint replacement, is the end stage of a biological process, with many previous earlier stages. Early-stage OA has been defined and involves structural changes identified by arthroscopy or radiography. The group argued that before the "early-stage OA" there must exist a stage where cellular processes, due to the presence of risk factors, have kicked into action but have not yet resulted in structural changes. The group suggested that this stage could be called "pre-osteoarthritis" (pre-OA). CONCLUSIONS: The group suggests that defining points of initiation for OA in the knee could be defined, for example, by traumatic episodes or surgical meniscectomy. Such events may set in motion metabolic processes that could be diagnosed by modern MRI protocols or arthroscopy including probing techniques before structural changes of early OA have developed. Preventive measures should preferably be applied at this pre-OA stage in order to stop the projected OA "epidemic."

Power to the patient: care tracks and empowerment a recipe for improving rehabilitation for hip fracture patients.

BACKGROUND/AIM: New surgical procedures, early operation and medical optimisation in patients with hip fracture have shown positive results on length of hospital stay. Our aims were to investigate whether patient empowerment along with an individually designed, postoperative rehabilitation programme could reduce length of hospital stay and whether the patients would have better chances to return to their previous living. DESIGN/METHOD: Patients were recruited during a 12-month period 2009-2010, with an intervention group treated with an individually designed, postoperative rehabilitation programme and a control group treated in a traditional way according to the hospitals routines. Final assessment was performed 4 month after surgery. The postoperative programme for the intervention group consisted of four standardised care tracks adapted individually for the patients. Assessments of Activity of Daily Living, American Society of Anesthesiologists classification of medical disease status and Short Portable Mental Status Questionnaire and living conditions were used to determine which care track was most appropriate. The patients were cared for with focus of empowerment in their rehabilitation. RESULTS: The study involved 503 hip fracture patients, 285 patients in the intervention group and 218 patients in the control group. The mean length of stay was 4 days shorter in the intervention group than in the control group (p = 0.04). Varied only to a small extent between the age groups in the intervention group and was greater between the age groups in the control. Patients in the intervention group returned to their previous living in 90% compared with 80% in the control group (p < 0.05). There were no significant differences between the age groups. CONCLUSION: Patient empowerment administrated by specially trained nursing staff and with specialised, tailor-made rehabilitation programme may be of benefit in helping patients to a shorter hospital stay and to return to their previous living.

Measurement of the migration of a focal knee resurfacing implant with radiostereometry.

BACKGROUND AND PURPOSE: Articular resurfacing metal implants have been developed to treat full-thickness localized articular cartilage defects. Evaluation of the fixation of these devices is mandatory. Standard radiostereometry (RSA) is a validated method for evaluation of prosthetic migration, but it requires that tantalum beads are inserted into the implant. For technical reasons, this is not possible for focal articular resurfacing components. In this study, we therefore modified the tip of an articular knee implant and used it as a marker for RSA, and then validated the method. MATERIAL AND METHODS: We modified the tip of a resurfacing component into a hemisphere with a radius of 3 mm, marked it with a 1.0-mm tantalum marker, and implanted it into a sawbone marked with 6 tantalum beads. Point-motion RSA of the "hemisphere bead" using standard automated RSA as the gold standard was compared to manual measurement of the tip hemisphere. 20 repeated stereograms with gradual shifts of position of the specimen between each double exposure were used for the analysis. The tip motion was compared to the point motion of the hemisphere bead to determine the accuracy and precision. RESULTS: The accuracy of the manual tip hemisphere method was 0.08-0.19 mm and the precision ranged from 0.12 mm to 0.33 mm. INTERPRETATION: The accuracy and precision for translations is acceptable when using a small hemisphere at the tip of a focal articular knee resurfacing implant instead of tantalum marker beads. Rotations of the implant cannot be evaluated. The method is accurate and precise enough to allow detection of relevant migration, and it will be used for future clinical trials with the new implant.

Finite element simulations of a focal knee resurfacing implant applied to localized cartilage defects in a sheep model.

Articular resurfacing metal implants have recently been tested in animal models to treat full thickness localized articular cartilage defects, showing promising results. However, the mechanical behavior of cartilage surrounding the metal implant has not been studied yet as it is technically challenging to measure in vivo contact areas, pressures, stresses and deformations from the metal implant. Therefore, we implemented a detailed numerical finite element model by approximating one of the condyles of the sheep tibiofemoral joint and created a defect of specific size to accommodate the implant. Using this model, the mechanical behavior of the surrounding of metal implant was studied. The model showed that the metal implant plays a significant role in the force transmission. Two types of profiles were investigated for metal implant. An implant with a double-curved profile, i.e., a profile fully congruent with the articular surfaces in the knee, gives lower contact pressures and stresses at the rim of the defect than the implant with unicurved spherical profile. The implant should be placed at a certain distance into the cartilage to avoid damage to opposing biological surface. Too deep positions, however, lead to high shear stresses in the cartilage edges around the implant. Mechanical sealing was achieved with a wedge shape of the implant, also useful for biochemical sealing of cartilage edges at the defect.

Once-weekly oral medication with alendronate does not prevent migration of knee prostheses: A double-blind randomized RSA study.

BACKGROUND AND PURPOSE: Early migration of joint replacements is an effect of poor fixation and can predict late loosening. By reducing the bone resorption after implantation of a joint replacement, it should be possible to enhance the initial fixation of the implant. We studied the effect of once-weekly treatment with alendronate after knee replacement. PATIENTS AND METHODS: We recruited 60 patients (60 knees) with gonarthrosis who were scheduled for a total knee replacement. They were operated on with identical implants and uncemented fixation. 30 patients were treated with a bisphosphonate (alendronate) and 30 patients underwent placebo treatment. The treatment started postoperatively and continued on a weekly basis for 6 months. The fixation of the implants was measured with repeated radiostereometry for 2 years. RESULTS: There was no difference in migration of implants between the two groups. CONCLUSION: With uncemented fixation of knee implants, no benefit of once-weekly treatment with alendronate, starting postoperatively, could be seen during a 2-year follow-up period.

A randomised RSA study of Peri-Apatite HA coating of a total knee prosthesis.

BACKGROUND: In total knee replacement, sound early fixation of the prosthesis is crucial for achieving a good long-term result and for minimising the risk of loosening. Various types of prosthetic material, different surface textures and shapes and the incorporation of screws or pegs have been used to achieve good fixation, particularly in the uncemented knee. Hydroxyapatite (HA) coating of prosthetic joint components is another technique used to enhance early stability and so to improve the longevity of the prosthesis-bone fixation. HA ceramic coatings are mostly plasma sprayed onto the fixation surface of the implant. Plasma spraying is largely a 'line of sight' technique and as such there are difficulties involved when covering three-dimensional planes, such as porous beaded fixation surfaces typically found on several knee prostheses. The objective of this study was to assess the clinical performance of the solution-deposited HA coating, Peri-Apatite , with regard to its ability to stimulate an endurable and stable implant fixation. PATIENTS AND METHODS: We randomised 60 patients into two groups; one group received the porous coated prosthesis with solution-deposited HA, and the other group received a prosthesis without HA. Radiostereometric examination was used as the primary tool for measuring migration in the prosthetic components. RESULTS: There was a lower incidence of early subsidence in the Peri-Apatite group. At 24 months there were no differences in clinical scorings or maximal total point motion. CONCLUSION: Addition of solution-deposited HA coating appears to provide better early stable fixation in a porous coated knee prosthesis.

Is removal of subchondral bone plate advantageous in cemented cup fixation? A randomized RSA study.

UNLABELLED: There is uncertainty regarding whether and how the subchondral bone plate should be treated during acetabular preparation for cemented cup fixation in a total hip arthroplasty. We hypothesized that removing the bone plate would improve the cement-bone interface without jeopardizing the initial cup stability, and therefore, be advantageous to long-term cup survival. We randomized 50 patients with primary osteoarthritis into two groups, one for removal and one for retention of the subchondral bone plate. The patients were evaluated during 2 years followup using repeated radiostereometric examinations, analyses of radiolucent lines, and clinical followups. Patient scoring was done using the Western Ontario and McMaster Universities Osteoarthritis Index, the Short Form-12, and the Harris hip score. Removal of the subchondral bone plate resulted in a superior cement-bone interface with less development of radiolucent lines. The radiostereometry results showed small migrations in both groups. We found no differences in cup stability between groups, although a difference was observed in rotational behavior with the removal group stabilizing in a slightly vertical position whereas the retention group showed slight but progressive rotation into a more horizontal position. No differences were found during clinical followups. Removing the subchondral bone plate, where possible, improves the cement-bone interface without jeopardizing the stability, implying better long-term cup survival. However, it is a more demanding surgical technique. LEVEL OF EVIDENCE: Therapeutic study, Level I (high quality randomized controlled trial with statistically significant difference or no statistically significant difference but narrow confidence intervals). See the Guidelines for Authors for a complete description of levels of evidence.

Guidelines for standardization of radiostereometry (RSA) of implants.

There is a need for standardization of radiostereometric (RSA) investigations to facilitate comparison of outcome reported from different research groups. In this document, 6 research centers have agreed upon standards for terminology, description and use of RSA arrangement including radiographic set-up and techniques. Consensus regarding minimum requirements for marker stability and scatter, choice of coordinate systems, and preferred way of describing prosthetic micromotion is of special interest. Some notes on data interpretation are also presented. Validation of RSA should be standardized by preparation of protocols for assessment of accuracy and precision. Practical issues related to loading of the joint by weight bearing or other conditions, follow-up intervals, length of follow-up, radiation dose, and the exclusion of patients due to technical errors are considered. Finally, we present a checklist of standardized output that should be included in any clinical RSA paper.This document will form the basis of a detailed standardization protocol under supervision of ISO and the European Standards Working Group on Joint Replacement Implants (CEN/TC 285/WG4). This protocol will facilitate inclusion of RSA in a standard protocol for implant testing before it is released for general use. Such a protocol-also including other recognized clinical outcome parameters-will reduce the risk of implanting potentially inferior prostheses on a large scale.

Mobile vs. fixed meniscal bearing in total knee replacement: a randomised radiostereometric study.

52 knees scheduled for a total knee arthroplasty were randomised to either a fixed or a mobile polyethylene bearing. The design was identical in all parts. The knee systems used were the Rotaglide Total Knee System (RTK) and the Nuffield Total Knee System (NTK), both from the same manufacturer (Corin Medical Ltd., UK). All knees implanted were uncemented. The patients were followed for 2 years clinically and with radiostereometric analyses to assess migration over time and inducible displacement of the tibial component. Separate analysis of the mobility of the tibial insert in the knees with a mobile bearing was also made. The migration measured with RSA between the 1st and 2nd year expressed as maximum total point motion (MTPM) might predict the risk of loosening of the implant. There were no differences between the groups regarding clinical outcome (HSS Knee score), migration or inducible displacement during the 2 years follow-up. The movement between the tibial tray and the mobile meniscal insert expressed as maximum total point motion (MTPM) was 6.8+/-3.3 mm at the 1st year follow-up.

Migration of the acetabular component: effect of cement pressurization and significance of early radiolucency: a randomized 5-year study using radiostereometry.

BACKGROUND: Cementing technique is a crucial factor in prosthesis fixation. No randomized studies have been published, however, comparing the outcome of conventional fingerpacking with the outcome of pressurization of the cement prior to cup insertion. PATIENTS AND METHODS: We randomized 50 THAs to either fingerpacking or sequential pressurization (including individual pressurization of each anchorage hole) and followed the patients with RSA for 5 years. The penetration of cement into the anchorage holes was measured on digital radiographs. Postoperative radiolucent lines around the cup were correlated to later RSA results. For clinical evaluation, we used SF-36 and HHS. RESULTS: The pressurized group of THAs was more stable regarding changes in inclination. We found no other difference in the migratory behavior. The cement penetration into the anchorage holes was deeper with the pressurization technique than with fingerpacking. For the whole group taken together, there was a strong relation between the presence of radiolucent lines as measured on the postoperative radiograph and later migration observed by RSA at 2 and 5 years. INTERPRETATION: Pressurization of the cement produced better cement penetration and increased the cup stability in terms of changes in inclination. Early findings of radiolucent lines can predict later unfavorable cup migration.

Implant migration after early weightbearing in cementless hip replacement.

UNLABELLED: Twenty-nine patients (five women and 24 men) with an average age of 47 years (range, 24-59 years) had 37 total hip arthroplasties using a hydroxyapatite-coated double-wedge press-fit femoral component. All patients had a Type A bone quality. Patients were either mobilized with weightbearing as tolerated or toe-touch weightbearing for 6 weeks postoperatively. After 6 weeks all patients were advanced to weightbearing as tolerated. Radiostereometric analysis radiographs were taken at 3 days, 6 weeks, and 6 months postoperatively to measure migration of the femoral component. Radiostereometric analysis revealed no difference in stem migration between the two groups as defined by maximal total point migration. There was a difference in the vertical (proximal-distal) migration within the first 6 weeks between groups (0.81 mm versus 0.13 mm), but not afterwards (0.17 mm versus 0.18 mm). Continuous migration after 6 weeks was observed in three patients from each group. There was no loosening in either group within a 2-year followup. Weightbearing as tolerated is recommended for young patients with excellent bone quality after cementless total hip arthroplasty with a double-wedge press-fit femoral component. LEVEL OF EVIDENCE: Diagnostic study, Level I (testing of previously developed diagnostic criteria in series of consecutive patients--with previously applied reference gold standard). See the Guidelines for Authors for a complete description of levels of evidence.

Improved acetabular pressurization gives better cement penetration: in vivo measurements during total hip arthroplasty.

During total hip arthroplasty, the intraoperative cementation pressure was measured inside one of the acetabular anchorage holes. Patients were randomized to pressurization of cement with either a conventional pressurizer or a sequential method including individual pressurization of each anchorage hole. The pressure was correlated to the cement penetration measured on digital radiographs. The early peak pressures were higher for the sequential method, resulting in a significantly better penetration of 2.8 mm compared with 0.7 mm with the conventional pressurizer. We found a strong correlation between early peak cementation pressures and cement penetration into the cancellous bone of the anchoring holes, indicating a cause-effect relationship at this early stage. The highest peak pressures were achieved during the later cup insertion, but these pressures did not correlate with the cement penetration. We conclude that conventional methods for cement pressurization in the acetabulum may not be optimal.