Less early subsidence of cemented Exeter short stems compared with cemented Exeter standard stems in Dorr type A femurs.

Aims: The Exeter short stem was designed for patients with Dorr type A femora and short-term results are promising. The aim of this study was to evaluate the minimum five-year stem migration pattern of Exeter short stems in comparison with Exeter standard stems. Methods: In this case-control study, 25 patients (22 female) at mean age of 78 years (70 to 89) received cemented Exeter short stem (case group). Cases were selected based on Dorr type A femora and matched first by Dorr type A and then age to a control cohort of 21 patients (11 female) at mean age of 74 years (70 to 89) who received with cemented Exeter standard stems (control group). Preoperatively, all patients had primary hip osteoarthritis and no osteoporosis as confirmed by dual X-ray absorptiometry scanning. Patients were followed with radiostereometry for evaluation of stem migration (primary endpoint), evaluation of cement quality, and Oxford Hip Score. Measurements were taken preoperatively, and at three, 12, and 24 months and a minimum five-year follow-up. Results: At three months, subsidence of the short stem -0.87 mm (95% confidence interval (CI) -1.07 to -0.67) was lower compared to the standard stem -1.59 mm (95% CI -1.82 to -1.36; p < 0.001). Both stems continued a similar pattern of subsidence until five-year follow-up. At five-year follow-up, the short stem had subsided mean -1.67 mm (95% CI -1.98 to -1.36) compared to mean -2.67 mm (95% CI -3.03 to -2.32) for the standard stem (p < 0.001). Subsidence was not influenced by preoperative bone quality (osteopenia vs normal) or cement mantle thickness. Conclusion: The standard Exeter stem had more early subsidence compared with the short Exeter stem in patients with Dorr type A femora, but thereafter a similar migration pattern of subsidence until minimum five years follow-up. Both the standard and the short Exeter stems subside. The standard stem subsides more compared to the short stem in Dorr type A femurs. Subsidence of the Exeter stems was not affected by cement mantle thickness.

Five-year polyethylene cup migration and PE wear of the Anatomic Dual Mobility acetabular construct.

INTRODUCTION: Dual mobility implants have been successful in reducing postoperative hip dislocation but mid-term results of cup migration and polyethylene wear are missing in the literature. Therefore, we measured migration and wear at 5-year follow-up using radiostereometric analysis (RSA). MATERIALS AND METHODS: A cohort of 44 patients (mean age 73, 36 female) with heterogeneous indications for hip arthroplasty but all with a high risk of hip dislocation received total hip replacement (THA) with The Anatomic Dual Mobility X3 monoblock acetabular construct and a highly crosslinked polyethylene liner. RSA images and Oxford Hip Scores were obtained perioperatively and 1, 2, and 5 years postoperatively. Cup migration and polyethylene wear were calculated using RSA. RESULTS: Mean 2-year proximal cup translation was 0.26 mm (95% CI 0.17; 0.36). Proximal cup translation was stable from 1- to 5-year follow-up. Mean 2-year cup inclination (z-rotation) was 0.23° (95% CI - 0.22; 0.68) and was greater in patients with osteoporosis compared to patients without osteoporosis (p = 0.04). Using 1-year follow-up as baseline, the 3D polyethylene wear rate was 0.07 mm/year (0.05; 0.10). Oxford hip scores improved 19 (95% CI 14; 24) points from mean 21 (range 4; 39) at baseline, to 40 (9; 48) 2 years postoperatively. There were no progressive radiolucent lines > 1 mm. There was 1 revision for offset correction. CONCLUSIONS: Anatomic Dual Mobility monoblock cups were well-fixed, the polyethylene wear rate was low, and the clinical outcomes were good until 5-year follow-up suggesting good implant survival in patients of different age groups and with heterogeneous indications for THA.

Feasibility and acceptability of a six-month exercise and patient education intervention for patients with hip dysplasia: A mixed methods study.

BACKGROUND AND OBJECTIVES: To evaluate the feasibility and acceptability of exercise and patient education for patients with hip dysplasia not receiving surgery. DESIGN: Feasibility study. METHODS: The participants received exercise instruction and patient education over six months. Feasibility covered recruitment, retention, and mechanisms of change (MC). MC were measured with Hip and Groin Outcome Score (HAGOS), muscle strength tests, Y-balance test, and hop for distance test (HDT) over six months. Acceptability covered adherence, expectations, perceptions, benefits, and harms. RESULTS: Thirty of 32 were recruited (median age: 30 years); six were lost to follow-up. Twenty-four participants improved by a mean of 11 (95%CI: 5-17) HAGOS pain points, improvements in all subscales were 1-11 points. Mean hip abduction strength improved 0.2 (95%CI: 0.04-0.4) Nm/kg, similar to flexion and extension. Median Y-balance test improvements: anterior: 70 (IQR: 64-74) to 75 (IQR: 72-80) centimetres; posteromedial: 104 (IQR: 94-112) to 119 (IQR: 112-122) centimetres and posterolateral: 98 (IQR: 89-109) to 116 (IQR: 108-121) centimetres (p < .001). Median improvement in HDT was: 37 (IQR: 30-44) to 52 (IQR: 45-58) centimetres (p < .001). Participants adhered to 84% of scheduled sessions (1,581:1,872), expectations were met, and perceptions were characterized by high self-efficacy for exercise. Benefits were reported with no serious harms. CONCLUSION: Patients with hip dysplasia are willing to be recruited for exercise and patient education, with acceptable retention. MC were observed through improvements in pain, strength and function with high acceptance of the exercise and patient education intervention. Thus, it seems feasible to conduct a full-scale randomised controlled trial.

Electrochemically applied hydroxyapatite on the cementless porous surface of Bi-Metric stems reduces early migration and has a lasting effect : an efficacy trial of a randomized five-year follow-up radiostereometric study.

AIMS: BoneMaster is a thin electrochemically applied hydroxyapatite (HA) coating for orthopaedic implants that is quickly resorbed during osseointegration. Early stabilization is a surrogacy marker of good survival of femoral stems. The hypothesis of this study was that a BoneMaster coating yields a fast early and lasting fixation of stems. METHODS: A total of 53 patients were randomized to be treated using Bi-Metric cementless femoral stems with either only a porous titanium plasma-sprayed coating (P group) or a porous titanium plasma-sprayed coating with an additional BoneMaster coating (PBM group). The patients were examined with radiostereometry until five years after surgery. RESULTS: At three months, the mean total translation (TT) was 0.95 mm (95% confidence interval (CI) 0.68 to 1.22) in the P group and 0.57 mm (95% CI 0.31 to 0.83) in the PBM group (p = 0.047). From two to five years, the TT increased by a mean of 0.14 mm (95% CI 0.03 to 0.25) more in the P group than in the PBM group (p = 0.021). In osteopenic patients (n = 20), the mean TT after three months was 1.61 mm (95% CI 1.03 to 2.20) in the P group and 0.73 mm (95% CI 0.25 to 1.21) in the PBM group (p = 0.023). After 60 months, the mean TT in osteopenic patients was 1.87 mm (95% CI 1.24 to 2.50) in the P group and 0.82 mm (95% CI 0.30 to 1.33) in the PBM group (p = 0.011). CONCLUSION: There was less early and midterm migration of cementless stems with BoneMaster coating compared with those with only a porous titanium plasma-sprayed coating. Although a BoneMaster coating seems to be important for stem fixation, especially in osteopenic patients, further research is warranted. Cite this article: Bone Joint J 2022;104-B(6):647-656.

Polyethylene liner motion in dual-mobility hip prostheses: static and dynamic radiostereometry in 16 patients 1 year after operation.

BACKGROUND AND PURPOSE: Dual-mobility hip arthroplasty utilizes a freely rotating polyethylene acetabular liner to protect against dislocation. As liner motion has not been confirmed in vivo, we undertook this using dynamic radiostereometry (RSA). PATIENTS AND METHODS: 6 patients with Anatomical Dual Mobility acetabular components were included. Markers were implanted in the liners using a drill guide. Static RSA recordings and patient-reported outcome measures were obtained postoperatively and at 1-year follow-up. Dynamic RSA recordings were obtained at 1-year follow-up during passive hip movement: abduction/external rotation, adduction/internal rotation (modified FABER-FADIR), to end-range and at 45° hip flexion. Liner and neck movements were described as anteversion, inclination, and rotation. RESULTS: Liner movement during modified FABER-FADIR was detected in 12 of 16 patients. Median (range) absolute liner movements were: anteversion 10° (5-20), inclination 6° (2-12), and rotation 11° (5-48) relative to the cup. Median absolute change in the resulting liner/neck angle (small articulation) was 28° (12-46) and in liner/cup angle (larger articulation) was 6° (4-21). Static RSA showed changes in median liner anteversion from 7° (-12 to 23) postoperatively to 10° (-3 to 16) at 1-year follow-up and inclination from 42° (35-66) postoperatively to 59° (46-80) at 1-year follow-up. Liner/neck contact was associated with high initial liner anteversion (p = 0.01). INTERPRETATION: The polyethylene liner moves over time. 1 year after surgery the liner can move with or without liner/neck contact. The majority of movement is in the smaller articulation between head and liner.

Combined and hybrid marker models for radiostereometry assessment of polyethylene liner motion in dual mobility hip prosthesis: a proof-of-concept study.

BACKGROUND: Investigation of polyethylene liner movement in total hip arthroplasty requires bead-marking for radiographic visibility of the liner. However, occlusion of markers poses a challenge for marker registration in radiographs. METHODS: The polyethylene of a dual mobility acetabular system was marked with twelve 1-mm tantalum markers (four groups of three markers) using a custom-made drill guide. Liner motion in a phantom and a patient was investigated with dynamic radiostereometry analysis (dRSA) at 1-year follow-up and static radiostereometry analysis (sRSA) postoperatively and at 1- and 2-year follow-up. A combined marker configuration (CMC) model was calculated from the registered positions of the liner markers and the femoral head in several images. Furthermore, the CMC model and the theoretic marker positions from computer-assisted models of the drill guide were combined in a hybrid model. RESULTS: The CMC model included eleven markers in the phantom and nine markers in the patient, which was sufficient for dRSA. Liner movement in the phantom followed liner contact with the femoral neck, while liner movement in the patient was independent. The hybrid model was necessary to determine liner orientation in sRSA recordings, which clearly changed from postoperative to 1- and 2-year follow-up even though the patient was positioned similarly. CONCLUSION: Polyethylene liner motion in dual mobility hip prosthesis can be assessed with CMC models in dRSA recordings. In sRSA, the liner position between follow-ups is unpredictable and analysis requires inclusion of all markers in the model, accomplished with a hybrid marker model. TRIAL REGISTRATION: ClinicalTrials.gov [ NCT02301182 ], 25 October 2015.

High relative reliability and responsiveness of the forgotten joint score-12 in patients with femoroacetabular impingement undergoing hip arthroscopic treatment. A prospective survey-based study.

The forgotten joint score-12 (FJS-12) may be an advantageous questionnaire in young patients with high hip function and a low level of pain. We investigated the reliability and the responsiveness of the FJS-12 in patients with femoroacetabular impingement undergoing hip arthroscopic treatment. Fifty patients were included in the reliability study and 34 patients were included in the responsiveness study. Test-retest reliability was assessed with intraclass correlation coefficient (ICC), standard error of measurement (SEM) and minimal detectable change (MDC). Responsiveness was assessed from testing correlations between the FJS-12 and the Copenhagen Hip and Groin Outcome Score (HAGOS) of the change score, effect size (ES) and standardized response mean (SRM). Floor and ceiling effect were defined as present if the number of patients obtaining the maximum (100) and minimum score (0) exceeded 15%. The relative reliability was high (ICC = 0.9, 95% CI: 0.8-0.9) and the absolute reliability was low (SEM = 11, MDCindividual = 32, MDCgroup = 4.5). The responsiveness was high, and the change score was highly correlated with the subscale 'pain' from the HAGOS and moderately correlated with the subscale 'ADL'. Furthermore, the FJS-12 exceeded or equalled the HAGOS subscales in ES and SRM. Below 15% of the patients scored the maximum or minimum score. The FJS-12 has high reliability, high responsiveness to change and shows no floor or ceiling effect.

Cytokine Profile in Patients with Aseptic Loosening of Total Hip Replacements and Its Relation to Metal Release and Metal Allergy.

Metal release from total hip replacements (THRs) is associated with aseptic loosening (AL). It has been proposed that the underlying immunological response is caused by a delayed type IV hypersensitivity-like reaction to metals, i.e., metal allergy. The purpose of this study was to investigate the immunological response in patients with AL in relation to metal release and the prevalence of metal allergy. THR patients undergoing revision surgery due to AL or mechanical implant failures were included in the study along with a control group consisting of primary THR patients. Comprehensive cytokine analyses were performed on serum and periimplant tissue samples along with metal analysis using inductive coupled plasma mass spectrometry (ICP-MS). Patient patch testing was done with a series of metals related to orthopedic implant. A distinct cytokine profile was found in the periimplant tissue of patients with AL. Significantly increased levels of the proinflammatory cytokines IL-1ß, IL-2, IL-8, IFN-γ and TNF-α, but also the anti-inflammatory IL-10 were detected. A general increase of metal concentrations in the periimplant tissue was observed in both revision groups, while Cr was significantly increased in patient serum with AL. No difference in the prevalence of metal sensitivity was established by patch testing. Increased levels of IL-1ß, IL-8, and TNF-α point to an innate immune response. However, the presence of IL-2 and IFN-γ indicates additional involvement of T cell-mediated response in patients with AL, although this could not be detected by patch testing.

High frequency of labral pathology in symptomatic borderline dysplasia: a prospective magnetic resonance arthrography study of 99 patients.

Labral pathology is seen in both dysplastic and borderline dysplastic hips. Periacetabular osteotomy (PAO) is the treatment of choice for dysplasia. However, some authors have suggested that borderline dysplastic hips with concurrent labral pathology should be treated arthroscopically. The purpose of this study was to investigate the frequency of labral pathology between dysplastic and borderline dysplastic hips, whether centre-edge (CE) angle is associated with labral pathology, and finally if pain and labral pathology are associated. Ninety-nine symptomatic patients (104 hips) scheduled for PAO were examined. Five patients were excluded due to complaints from multiple joints and four failed to show at 2-year follow-up. Five patients did not fill out questionnaires preoperatively. Hips were characterized as dysplastic (CE angle <20°) and borderline dysplastic (CE angle 20° ≤ 25°). A magnetic resonance arthrography was performed, and labral pathology was classified according to the Czerny classification. Association with the CE angle, the acetabular index (AI) and preoperative WOMAC pain score was tested by multiple linear regression. There was no significant difference in frequency of labral pathology when comparing the two groups. Across the cohort, 86 of 99 patients had labral pathology. The CE angle was associated with increasing severity of labral pathology, whereas the AI angle and preoperative pain were not associated with labral pathology. Decreased lateral coverage adversely loads the labrum, predisposing it to tears. We advocate reorienting the biomechanical forces through PAO, not arthroscopic treatment. Level of pain was not associated with labral pathology, suggesting that labral pathology may not alone explain the dysplastic pain complex.

Progressive resistance training in patients with hip dysplasia: A feasibility study.

OBJECTIVES: To examine whether progressive resistance training is feasible in patients with symptomatic hip dysplasia scheduled for periacetabular osteotomy. A secondary objective was to investigate patient-reported outcomes, functional performance and hip muscle strength. DESIGN: Feasibility study. PATIENTS AND METHODS: Seventeen patients (median age 28 years, range 22-40 years) performed 8 weeks (20 sessions) of supervised sessions of progressive resistance training. Training-adherence, number of dropouts and adverse events, and visual analogue scale scores on pain were registered. Patients completed the Hip and Groin Outcome Score, performed 2 hop-tests, and hip peak torque was assessed by isokinetic dynamometry. RESULTS: Training-adherence was 90.3±9%. Few and minor adverse events were observed, one patient dropped out and acceptable pain levels were reported during the intervention. Scores on 4 out of 6 subscales on patient-reported outcome improved (p <0.05), as did standing distance jump (12.2%, 95% confidence interval (CI) [1.3, 23.0]), countermovement jump (25.1%, 95% CI [1.3, 48.8]). Isokinetic concentric hip flexion peak torque showed significant improvements (16.6%, 95% CI [4.6, 28.6]) on the affected side while isometric hip flexion (10.9%, 95% CI [0.3, 21.6]) improved on the non-affected side. CONCLUSION: Supervised progressive resistance training is feasible in patients with hip dysplasia. The intervention may improve pain levels, patient-reported outcomes, functional performance and hip flexion muscle strength.

Physical Activity Is Associated With the Level of Chromium but Not With Changes in Pseudotumor Size in Patients With Metal-on-Metal Hip Arthroplasty.

BACKGROUND: Metal-on-metal (MoM) total hip arthroplasty (THA) and resurfacing hip arthroplasty (RHA) were previously considered an excellent option for young and physically active patients. However, the relationship between MoM THA/RHA patients' daily physical activity (PA), metal ion measurements of chromium and cobalt, and pseudotumor dynamic is insufficiently explored. METHODS: One hundred eleven patients with 148 hip articulations, 77 MoM THA/RHA and 71 MoP THA, participated in a prospective cohort study, with 5 cross-sectional analyses during a 1-year follow-up. Baseline follow-up was at mean 7.1 (range: 0.2-21.5) years postoperative. At baseline and every 3 months thereafter, patients' daily PA was monitored during a 2-week period using a triaxial accelerometer, and next metal artifact reducing sequence magnetic resonance imaging scans, metal ion measurements of chromium and cobalt, and the Copenhagen Hip and Groin Outcome Score questionnaire were completed. RESULTS: We found a statistically significant relationship between daily PA and metal ion measurements of chromium at all follow-ups in MoM THA/RHA patients (P ≤ .03) but not in MoP THA patients (P > .35). Patients' daily PA was not related to changes in pseudotumor size at any follow-up (P > .30). Ten of 26 (38%) pseudotumors in MoM THA/RHA and 8 of 29 (28%) pseudotumors in MoP THA changed classification according to the Anderson grading. No pseudotumors transformed in appearance or changed anatomical location. CONCLUSION: The daily PA of MoM THA/RHA patients is associated with metal ion measurements of chromium but not with changes in pseudotumor size. This is new and important knowledge, which may be useful for hip surgeons in recommendation and monitoration of the consequences of PA in active patients with MoM THA/RHA.

Equal Primary Fixation of Resurfacing Stem, but Inferior Cup Fixation With Anterolateral vs Posterior Surgical Approach. A 2-Year Blinded Randomized Radiostereometric and Dual-energy X-Ray Absorptiometry Study of Metal-on-Metal Hip Resurfacing Arthroplasty.

BACKGROUND: The anterolateral (AntLat) surgical approach may spare the blood supply to the femoral head and improve the accuracy of cup positioning in metal-on-metal hip resurfacing arthroplasty. Thereby, potentially lessen complications such as avascular head necrosis, femoral neck narrowing and fracture, improve implant fixation, and lessen periprosthetic bone mineral density (BMD) loss. METHODS: Between November 2008 and January 2012, a randomized clinical trial was performed at Aarhus University Hospital. A total of 49 patients (28 males) were allocated to metal-on-metal hip resurfacing arthroplasty by the AntLat (n = 25) or the posterior (Post; n = 24) surgical approach. Patients were followed with radiostereometric analysis, measurements of periprosthetic BMD, clinical outcome scores of Harris hip score and visual analogue scale, serum metal ions, and conventional radiographs. RESULTS: At 3 months, cups in the AntLat group had higher total translations of mean 1.00 ± 0.70 mm vs mean 0.64 ± 0.45 mm in the post group (P = .04), and higher total rotations of mean 2.44° ± 1.36° vs mean 1.39° ± 1.17° in the Post group (P = .002). All migrations of cup and stem were similar at 1 and 2 years postoperative (P > .07). At 1 year, periprosthetic BMD since postoperative at the medial side of the stem was reduced to mean 98.45% ± 8.57% in the AntLat group, and increased to mean 105.57% ± 11.07% in the Post group (P = .02), but measurements were comparable at 2 years (P = .05). CONCLUSION: Cups inserted by the AntLat approach migrated more until 3 months postoperative. This illustrates a less good primary cup fixation with the AntLat approach; however, all cups were well-fixed after 3 months' follow-up indicating a good secondary fixation.

Titanium: a review on exposure, release, penetration, allergy, epidemiology, and clinical reactivity.

Exposure to titanium (Ti) from implants and from personal care products as nanoparticles (NPs) is common. This article reviews exposure sources, ion release, skin penetration, allergenic effects, and diagnostic possibilities. We conclude that human exposure to Ti mainly derives from dental and medical implants, personal care products, and foods. Despite being considered to be highly biocompatible relative to other metals, Ti is released in the presence of biological fluids and tissue, especially under certain circumstances, which seem to be more likely with regard to dental implants. Although most of the studies reviewed have important limitations, Ti seems not to penetrate a competent skin barrier, either as pure Ti, alloy, or as Ti oxide NPs. However, there are some indications of Ti penetration through the oral mucosa. We conclude that patch testing with the available Ti preparations for detection of type IV hypersensitivity is currently inadequate for Ti. Although several other methods for contact allergy detection have been suggested, including lymphocyte stimulation tests, none has yet been generally accepted, and the diagnosis of Ti allergy is therefore still based primarily on clinical evaluation. Reports on clinical allergy and adverse events have rarely been published. Whether this is because of unawareness of possible adverse reactions to this specific metal, difficulties in detection methods, or the metal actually being relatively safe to use, is still unresolved.

Failure of total hip implants: metals and metal release in 52 cases.

BACKGROUND: The pathogenesis of total joint replacement failure is multifactorial. One hypothesis suggests that corrosion and wear of alloys result in metal ion release, which may then cause sensitization and even implant failure, owing to the acquired immune reactivity. OBJECTIVES: To assess cobalt, nickel and chromium(VI) release from, and the metal composition of, failed metal-on-ethylene total hip replacements. MATERIALS/METHODS: Implant components from 52 revision cases were evaluated with spot tests for free nickel, cobalt, and chromium (VI) ions. Implant composition was determined with X-ray fluorescence spectroscopy, and information on the reason for revision and complications in relation to surgery was collected from the medical charts when possible (72%). For 10 implants, corrosion was further characterized with scanning electron microscopy. RESULTS: We detected cobalt release from three of 38 removed femoral heads and from one of 24 femoral stems. Nickel release was detected from one of 24 femoral stems. No chromium(VI) release was detected. CONCLUSIONS: We found that cobalt and nickel were released from some failed total hip arthroplasties, and corrosion was frequently observed. Metal ions and particles corroded from metal-on-polyethylene may play a role in the complex aetiopathology of implant failure.

Metal release and metal allergy after total hip replacement with resurfacing versus conventional hybrid prosthesis.

BACKGROUND: Metal-on-metal (MOM) total hip arthroplasties were reintroduced because of the problems with osteolysis and aseptic loosening related to polyethylene wear of early metal-on-polyethylene (MOP) arthroplasties. The volumetric wear rate has been greatly reduced with MOM arthroplasties; however, because of nano-size wear particles, the absolute number has been greatly increased. Thus, a source of metal ion exposure with the potential to sensitize patients is present. We hypothesized that higher amounts of wear particles result in increased release of metal ions and ultimately lead to an increased incidence of metal allergy. METHODS: 52 hips in 52 patients (median age 60 (51-64) years, 30 women) were randomized to either a MOM hip resurfacing system (ReCap) or a standard MOP total hip arthoplasty (Mallory Head/Exeter). Spot urine samples were collected preoperatively, postoperatively, after 3 months, and after 1, 2, and 5 years and tested with inductively coupled plasma-sector field mass spectrometry. After 5 years, hypersensitivity to metals was evaluated by patch testing and lymphocyte transformation assay. In addition, the patients answered a questionnaire about hypersensitivity. RESULTS: A statistically significant 10- to 20-fold increase in urinary levels of cobalt and chromium was observed throughout the entire follow-up in the MOM group. The prevalence of metal allergy was similar between groups. INTERPRETATION: While we observed significantly increased levels of metal ions in the urine during the entire follow-up period, no difference in prevalence of metal allergy was observed in the MOM group. However, the effect of long-term metal exposure remains uncertain.

Acid etching and plasma sterilization fail to improve osseointegration of grit blasted titanium implants.

Interaction between implant surface and surrounding bone influences implant fixation. We attempted to improve the bone-implant interaction by 1) adding surface micro scale topography by acid etching, and 2) removing surface-adherent pro-inflammatory agents by plasma cleaning. Implant fixation was evaluated by implant osseointegration and biomechanical fixation.The study consisted of two paired animal sub-studies where 10 skeletally mature Labrador dogs were used. Grit blasted titanium alloy implants were inserted press fit in each proximal tibia. In the first study grit blasted implants were compared with acid etched grit blasted implants. In the second study grit blasted implants were compared with acid etched grit blasted implants that were further treated with plasma sterilization. Implant performance was evaluated by histomorphometrical investigation (tissue-to-implant contact, peri-implant tissue density) and mechanical push-out testing after four weeks observation time.Neither acid etching nor plasma sterilization of the grit blasted implants enhanced osseointegration or mechanical fixation in this press-fit canine implant model in a statistically significant manner.

Cobalt release from implants and consumer items and characteristics of cobalt sensitized patients with dermatitis.

BACKGROUND: Cobalt allergy is prevalent in dermatitis patients. Very little documentation exists about current sources of cobalt exposure. OBJECTIVES: To investigate and discuss putative sources of cobalt exposure and to present selected epidemiological data on cobalt allergy from patch-tested dermatitis patients in an attempt to better understand cobalt allergy. MATERIALS AND METHODS: 19,780 dermatitis patients aged 4-99 years were patch tested with nickel, chromium or cobalt between 1985 and 2010. The cobalt spot test was used to test for cobalt ion release from mobile phones as well as cobalt-containing dental alloys and revised hip implant components. RESULTS: Six of eight dental alloys and 10 of 98 revised hip implant components released cobalt in the cobalt spot test, whereas none of 50 mobile phones gave positive reactions. The clinical relevance of positive cobalt test reactions was difficult to determine in the majority of patients. Isolated patch test reactivity to cobalt was less associated with occupational dermatitis and hand eczema than patch test reactivity to cobalt in combination with other contact allergies. CONCLUSIONS: It is often difficult to interpret the relevance of a positive patch test reaction to cobalt, and there is a need for further studies to determine sources of cobalt exposure.

Acid etching does not improve CoCrMo implant osseointegration in a canine implant model.

Induction of bone ingrowth by topographical changes to implant surfaces is an attractive concept. Topographical modifications achieved by acid etching are potentially applicable to complex 3D surfaces. Using clinically relevant implant models, we explored the effect of wet etching porous bead-coated CoCrMo. The study was designed as two paired animal experiments with 10 dogs. Each dog received four implants; one in each medial femoral condyle (loaded 0.75-mm-gap model) and one in each proximal tibia (press-fit). The implants were observed for 6 weeks and were evaluated by biomechanical pushout tests and histomorphometry. We found that wet etching porous bead-coated CoCrMo implants failed to improve implant performance. Moreover, a tendency towards increased fibrous tissue formation, decreased new bone formation, and decreased mechanical fixation was observed. Surface topography on implants is able to stimulate bone-forming cells, but the clinical performance of an implant surface perhaps relies more on 3D geometrical structure and biocompatibility. Caution should be exercised regarding the results of wet etching of porous bead-coated CoCrMo and there is a need for more preclinical trials.

Biomechanical implant fixation of CoCrMo coating inferior to titanium coating in a canine implant model.

The use of CoCrMo in orthopedic surgery is not new, and CoCrMo (cobalt-chromium-molybdenum) is well tolerated. Nevertheless, the alloy is still considered less biocompatible than titanium. We therefore wanted to explore the biocompatibility of CoCrMo by investigating the biomechanical implant fixation and implant osseointegration of CoCrMo (ASTM F-75) porous bead-coated and titanium (ASTM F-136) porous bead-coated implants. In 10 dogs, the two implant types were inserted into the proximal part of the humerus. Implant sites were overdrilled, leaving an empty 0.75-mm gap between implant and surrounding bone. The implants were observed for 6 weeks and were evaluated by biomechanical push-out test and histomorphometry. We found a statistically significant 40% decrease in the biomechanical fixation of CoCrMo porous bead-coated implants compared with titanium porous bead-coated implants. Implant osseointegration was comparable between the two implants; however, a slight decrease in bone volume density around CoCrMo implants was observed. Insertions of CoCrMo implants are associated with a disturbance of the delicate peri-implant milieu. Even from implants not subjected to any mechanical forces, metal ions are liberated and result in intra- and extracellular accumulation in the immediate implant vicinity, presenting a likely explanation for our findings. A 40% reduction of initial implant fixation could prove to be serious because initial implant fixation is critical for long-term performance. The choice between titanium alloy and CoCrMo should, however, ultimately be governed by a comprehensive review of all factors influencing clinical implant survival. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.