Quality-Adjusted Life Years Gained by Hip and Knee Replacement Surgery and Its Aftercare.

OBJECTIVES: To determine the lifetime quality-adjusted life years (QALYs) gained by total joint arthroplasty (TJA), and assess the QALYs attributed to specific postoperative rehabilitation interventions. DESIGN: Secondary analysis of 2 multicenter, randomized controlled trials (RCTs) with 3-, 6-, 12-, and 24-month follow-up. SETTING: Two university hospitals, 2 municipal hospitals, and 1 rural hospital. PARTICIPANTS: Patients (N=827) who underwent total hip arthroplasty (THA) or total knee arthroplasty (TKA). INTERVENTIONS: RCT A: 465 patients were randomly assigned to receive aquatic therapy (pool exercises aimed at training of proprioception, coordination, and strengthening) 6 versus 14 days after THA or TKA. RCT B: 362 patients were randomly assigned to either perform or not perform ergometer cycling beginning 2 weeks after THA or TKA. MAIN OUTCOME MEASURE: QALYs, based on the Short Form-6 Dimensions utility, measured at baseline and 3, 6, 12, and 24 months' follow-up. RESULTS: After hip arthroplasty, the lifetime QALYs increased by 2.35 years in the nonergometer group, and by 2.30 years in the early aquatic therapy group. However, after knee arthroplasty, the lifetime QALYs increased by 1.81 years in the nonergometer group, and by 1.60 years in the early aquatic therapy group. By ergometer cycling, .55 additional QALYs could be gained after hip and .10 additional QALYs after knee arthroplasty, while the additional QALYs attributed to the timing of aquatic therapy were .12 years after hip and .01 years after knee arthroplasty. CONCLUSIONS: This analysis provides a sound estimate for the determination of the lifetime QALYs gained by THA and TKA. In addition, this analysis demonstrates that specific postoperative rehabilitation can result in an additional mean QALY gain of .55 years, which represents one fourth of the effect of surgery. Even if this is interpreted as a small effect at an individual level, it is important when extrapolated to all patients undergoing TJA. At a national level, these improvements appear to have a similar magnitude of QALY gain when compared with published data regarding medications to lower blood pressure in all persons with arterial hypertension.

Is a Revision a Revision? An Analysis of National Arthroplasty Registries' Definitions of Revision.

BACKGROUND: The reported survival of implants depends on the definition used for the endpoint, usually revision. When screening through registry reports from different countries, it appears that revision is defined quite differently. QUESTIONS/PURPOSES: The purposes of this study were to compare the definitions of revision among registry reports and to apply common clinical scenarios to these definitions. METHODS: We downloaded or requested reports of all available national joint registries. Of the 23 registries we identified, 13 had published reports that were available in English and were beyond the pilot phase. We searched these registries' reports for the definitions of the endpoint, mostly revision. We then applied the following scenarios to the definition of revision and analyzed if those scenarios were regarded as a revision: (A) wound revision without any addition or removal of implant components (such as hematoma evacuation); (B) exchange of head and/or liner (like for infection); (C) isolated secondary patella resurfacing; and (D) secondary patella resurfacing with a routine liner exchange. RESULTS: All registries looked separately at the characteristic of primary implantation without a revision and 11 of 13 registers reported on the characteristics of revisions. Regarding the definition of revision, there were considerable differences across the reports. In 11 of 13 reports, the primary outcome was revision of the implant. In one registry the primary endpoint was "reintervention/revision" while another registry reported separately on "failure" and "reoperations". In three registries, the definition of the outcome was not provided, however in one report a results list gave an indication for the definition of the outcome. Wound revision without any addition or removal of implant components (scenario A) was considered a revision in three of nine reports that provided a clear definition on this question, whereas two others did not provide enough information to allow this determination. Exchange of the head and/or liner (like for infection; scenario B) was considered a revision in 11 of 11; isolated secondary patella resurfacing (scenario C) in six of eight; and secondary patella resurfacing with routine liner exchange (scenario D) was considered a revision in nine of nine reports. CONCLUSIONS: Revision, which is the most common main endpoint used by arthroplasty registries, is not universally defined. This implies that some reoperations that are considered a revision in one registry are not considered a revision in another registry. Therefore, comparisons of implant performance using data from different registries have to be performed with caution. We suggest that registries work to harmonize their definitions of revision to help facilitate comparisons of results across the world's arthroplasty registries.

A new universal, standardized implant database for product identification: a unique tool for arthroplasty registries.

INTRODUCTION: Every joint registry aims to improve patient care by identifying implants that have an inferior performance. For this reason, each registry records the implant name that has been used in the individual patient. In most registries, a paper-based approach has been utilized for this purpose. However, in addition to being time-consuming, this approach does not account for the fact that failure patterns are not necessarily implant specific but can be associated with design features that are used in a number of implants. Therefore, we aimed to develop and evaluate an implant product library that allows both time saving barcode scanning on site in the hospital for the registration of the implant components and a detailed description of implant specifications. MATERIALS AND METHODS: A task force consisting of representatives of the German Arthroplasty Registry, industry, and computer specialists agreed on a solution that allows barcode scanning of implant components and that also uses a detailed standardized classification describing arthroplasty components. The manufacturers classified all their components that are sold in Germany according to this classification. The implant database was analyzed regarding the completeness of components by algorithms and real-time data. RESULTS: The implant library could be set up successfully. At this point, the implant database includes more than 38,000 items, of which all were classified by the manufacturers according to the predefined scheme. Using patient data from the German Arthroplasty Registry, several errors in the database were detected, all of which were corrected by the respective implant manufacturers. CONCLUSIONS: The implant library that was developed for the German Arthroplasty Registry allows not only on-site barcode scanning for the registration of the implant components but also its classification tree allows a sophisticated analysis regarding implant characteristics, regardless of brand or manufacturer. The database is maintained by the implant manufacturers, thereby allowing registries to focus their resources on other areas of research. The database might represent a possible global model, which might encourage harmonization between joint replacement registries enabling comparisons between joint replacement registries.

[Registries as a tool for optimizing safety of endoprostheses. Experiences from other countries and the setup of the German arthroplasty register]. / Register als Werkzeug für mehr Endoprothesensicherheit. Erfahrungen aus anderen Ländern und dem Aufbau des Endoprothesenregisters Deutschland.

There has previously been no structured long-term documentation of the results of hip and knee prosthesis operations in Germany. This article presents the objectives, structure and data flow of the newly established German arthroplasty registry (EPRD). The EPRD is run as a subdivision of the German Society for Orthopedics and Orthopedic Surgery (Deutsche Gesellschaft für Orthopädie und orthopädische Chirurgie, DGOOC). It is dedicated to scientific principles and guarantees independency and immediate feedback to surgeons. The cooperation between insurance funds, hospitals, industry and scientific society is the key to success. Additional data acquisition and bureaucratic formalities are limited to a minimum and in particular there is no use of paper. Involving the health insurance funds provides access to relevant routine data. The implant documentation is facilitated by means of an implant library and barcode scanning in the operating room. The EPRD documents the survival of implants including the reasons for revision. Although the highest level of patient data protection is guaranteed, individual patients can be identified in case of implant recalls.

Multicenter randomized controlled trial comparing early versus late aquatic therapy after total hip or knee arthroplasty.

OBJECTIVE: To evaluate if the timing of aquatic therapy influences clinical outcomes after total knee arthroplasty (TKA) or total hip arthroplasty (THA). DESIGN: Multicenter randomized controlled trial with 3-, 6-, 12-, and 24-month follow-up. SETTING: Two university hospitals, 1 municipal hospital, and 1 rural hospital. PARTICIPANTS: Patients (N=465) undergoing primary THA (n=280) or TKA (n=185): 156 men, 309 women. INTERVENTION: Patients were randomly assigned to receive aquatic therapy (pool exercises aimed at training of proprioception, coordination, and strengthening) after 6 versus 14 days after THA or TKA. MAIN OUTCOME MEASURES: Primary outcome was self-reported physical function as measured by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at 3-, 6-, 12-, and 24-months postoperatively. Results were compared with published thresholds for minimal clinically important improvements. Secondary outcomes included the Medical Outcomes Study 36-Item Short-Form Health Survey, Lequesne-Hip/Knee-Score, WOMAC-pain and stiffness scores, and patient satisfaction. RESULTS: Baseline characteristics of the 2 groups were similar. Analyzing the total study population did not result in statistically significant differences at all follow-ups. However, when performing subanalysis for THA and TKA, opposite effects of early aquatic therapy were seen between TKA and THA. After TKA all WOMAC subscales were superior in the early aquatic therapy group, with effect sizes of WOMAC physical function ranging from .22 to .39. After THA, however, all outcomes were superior in the late aquatic therapy group, with WOMAC effect sizes ranging from .01 to .19. However, the differences between treatment groups of these subanalyses were not statistically significant. CONCLUSIONS: Early start of aquatic therapy had contrary effects after TKA when compared with THA and it influenced clinical outcomes after TKA. Although the treatment differences did not achieve statistically significance, the effect size for early aquatic therapy after TKA had the same magnitude as the effect size of nonsteroidal anti-inflammatory drugs in the treatment of osteoarthritis of the knee. However, the results of this study do not support the use of early aquatic therapy after THA. The timing of physiotherapeutic interventions has to be clearly defined when conducting studies to evaluate the effect of physiotherapeutic interventions after TKA and THA.

Role of oxidative stress in rheumatoid arthritis: insights from the Nrf2-knockout mice.

OBJECTIVES: Increasing evidence suggests that oxidative stress may play a key role in joint destruction due to rheumatoid arthritis (RA). The aim of this study was to elucidate the role of nuclear factor erythroid 2-related factor 2 (Nrf2), a transcription factor that maintains the cellular defence against oxidative stress, in RA. METHODS: The activation status of Nrf2 was assessed in synovial tissue from patients with RA using immunohistochemistry. Antibody-induced arthritis (AIA) was induced in Nrf2-knockout and Nrf2-wild-type control mice. The severity of cartilage destruction was evaluated using a damage score. The extent of oxidative stress, the activation state of Nrf2 and the expression level of Nrf2 target genes were analysed by immunhistological staining. The expression of vascular endothelial growth factor (VEGF)-A was examined on mRNA and protein using the Luminex technique. A Xenogen imaging system was used to measure Nrf2 activity in an antioxidant response element-luciferase transgenic mouse during AIA. RESULTS: Nrf2 was activated in the joints of arthritic mice and of patients with RA. Nrf2-knockout mice had more severe cartilage injuries and more oxidative damage, and the expression of Nrf2 target genes was enhanced in Nrf2-wild-type but not in knockout mice during AIA. Both VEGF-A mRNA and protein expression was upregulated in Nrf2-knockout mice during AIA. An unexpected finding was the number of spontaneously fractured bones in Nrf2-knockout mice with AIA. CONCLUSION: These results provide strong evidence that oxidative stress is significantly involved in cartilage degradation in experimental arthritis, and indicate that the presence of a functional Nrf2 gene is a major requirement for limiting cartilage destruction.

Women recover faster than men after standard knee arthroplasty.

BACKGROUND: Specific anatomic differences are believed to account for gender-specific function and health-related quality of life after TKA. However, there are conflicting data in the literature regarding these gender-specific outcomes, especially as woman appear to have surgery later in the course of the disease compared with men. QUESTIONS/PURPOSES: We asked whether (1) women had worse knee function and health-related quality of life after TKA compared with men, (2) lower improvements in scores, and (3) slower recovery after surgery. METHODS: Using a cohort study design, we retrospectively analyzed prospectively collected data from three multicenter randomized controlled trials evaluating rehabilitation measures after standard unisex knee arthroplasty in 494 patients (141 men and 353 women). The primary outcome was self-reported physical function as measured by the WOMAC at 3, 6, 12, and 24 months after surgery. Secondary outcomes included the pain and stiffness scales of the WOMAC and the physical and mental component summaries of the SF-36. At the time of surgery, the women were on average older (70.8 versus 67.8 years), had lower mean physical function (55 versus 47), higher mean pain scores (54 versus 48), and greater stiffness (54 versus 46) as measured by the WOMAC. RESULTS: At the 3-, 6-, 12-, and 24-month followups, men and women had similar WOMAC scores. Improvements were greater for women compared with men for WOMAC function and pain subscale scores at the 3-month (function, 28 versus 23; pain, 32 versus 25) and 6-month followups (function, 32 versus 27; pain, 36 versus 31). At the 12- and 24-month followups we noted no differences in improvement between men and women. CONCLUSION: Although women had greater functional limitations at the time of surgery than men, they recover faster early after standard TKA although function is similar at 12 and 24 months. Women also had greater improvement of WOMAC scores after standard TKA than men. LEVEL OF EVIDENCE: Level II, prognostic study. See the guidelines for authors for a complete description of levels of evidence.

17ß-estradiol reduces expression of MMP-1, -3, and -13 in human primary articular chondrocytes from female patients cultured in a three dimensional alginate system.

Clinical observations have suggested a relationship between osteoarthritis and a changed sex-hormone metabolism, especially in menopausal women. This study analyzes the effect of 17ß-estradiol on expression of matrix metalloproteinases-1, -3, -13 (MMP-1, -3, -13) and tissue inhibitors of metalloproteinases-1, -2 (TIMP-1, -2) in articular chondrocytes. An imbalance of matrix metalloproteinases (MMPs) specialized on degradation of articular cartilage matrix over the respective inhibitors of these enzymes (TIMPs) that leads to matrix destruction was postulated in the pathogenesis of osteoarthritis. Primary human articular chondrocytes from patients of both genders were cultured in alginate beads at 5% O(2) to which 10(-11)M-10(-5)M 17ß-estradiol had been added and analyzed by means of immunohistochemistry, immunocytochemistry and real-time RT-PCR. Since articular chondrocytes in vivo are adapted to a low oxygen tension, culture was performed at 5% O(2). Immunohistochemical staining in articular cartilage tissue from patients and immunocytochemical staining in articular chondrocytes cultured in alginate beads was positive for type II collagen, estrogen receptor α, MMP-1, and -13. It was negative for type I collagen, MMP-3, TIMP-1 and -2. Using real-time RT-PCR, it was demonstrated that physiological and supraphysiological doses of 17ß-estradiol suppress mRNA levels of MMP-3 and -13 significantly in articular chondrocytes of female patients. A significant suppressing effect was also seen in MMP-1 mRNA after a high dose of 10(-5)M 17ß-estradiol. Furthermore, high doses of this hormone led to tendentially lower TIMP-1 levels whereas the TIMP-2 mRNA level was not influenced. In male patients, only incubations with high doses (10(-5)M) of 17ß-estradiol were followed by a tendency to suppressed MMP-1 and TIMP-1 levels while TIMP-2 mRNA level was decreased significantly. There was no effect on MMP-13 expression of cells from male patients. Taken together, application of 17ß-estradiol in physiological doses will improve the imbalance between the amounts of MMPs and TIMPs in articular chondrocytes from female patients. Downregulation of TIMP-2 by 17ß-estradiol in male patients would not be articular cartilage protective.

Femoral artery constriction by norepinephrine is enhanced by methylprednisolone in a rat model.

BACKGROUND: Corticosteroids are associated with femoral head osteonecrosis and arterial hypertension. The patho-mechanism of femoral head osteonecrosis is often attributed to ischemia. The aim of this study was to investigate if corticosteroids directly constrict the femoral artery or if they have a permissive effect on norepinephrine and endothelin-1-induced vasoconstriction. METHODS: Femoral artery segments were harvested from twenty Wistar rats and mounted as ring preparations on a small-vessel myograph for the purpose of making isometric force measurements. For the norepinephrine study, twenty femoral artery segments from ten rats were stimulated cumulatively with norepinephrine before and after incubation with methylprednisolone (5 mug/mL). For the endothelin-1 study, forty femoral artery segments from ten rats were used. The four artery segments from each animal were randomized by pairs to either a corticosteroid treatment group (5 mug/mL methylprednisolone incubation, n = 20) or a control group (placebo incubation, n = 18, as two of the twenty control-group vessels did not meet protocol requirements). Isometric wall tension was plotted and quantified by the EC(50) (the plasma concentration of endothelin-1 required for obtaining 50% of maximal constriction in vivo). RESULTS: In the norepinephrine-stimulated group, incubation with methylprednisolone did not directly induce any vasoconstriction but did enhance norepinephrine-elicited vasoconstriction. The norepinephrine dose-response curve displayed a shift to the left after incubation with methylprednisolone. This shift was reflected by a significantly lower mean EC50 of 9.5 x 10(-7) M +/- 5.1 x 10(-7) M after methylprednisolone incubation compared with a mean of 2.5 x 10(-6) M +/- 1.1 x 10(-6) M before incubation (p < 0.005). In the endothelin-1-stimulated group, the endothelin-1 dose-response curve displayed a tendency toward stronger contraction in the vessels that were incubated with methylprednisolone, but this tendency did not reach significance. CONCLUSIONS: Incubation with methylprednisolone enhances norepinephrine-mediated contraction of the femoral artery in a rat model. CLINICAL RELEVANCE: Vasoconstriction of the vascular bed supplying the femoral head can diminish femoral head blood flow, and this may be a factor in the early pathogenesis of corticosteroid-associated femoral head osteonecrosis.

Five-Year Survival of 20,946 Unicondylar Knee Replacements and Patient Risk Factors for Failure: An Analysis of German Insurance Data.

BACKGROUND: Improvements in implant design and surgical technique of unicondylar knee arthroplasty have led to reduced revision rates, but patient selection seems to be crucial for success of such arthroplasties. The purpose of the present study was to analyze the 5-year implant survival rate of unicondylar knee replacements in Germany and to identify patient factors associated with an increased risk of revision, including >30 comorbid conditions. METHODS: Using nationwide billing data of the largest German health-care insurance for inpatient hospital treatment, we identified patients who underwent unicondylar knee arthroplasty between 2006 and 2012. Kaplan-Meier survival curves with revision as the end point and log-rank tests were used to evaluate 5-year implant survival. A multivariable Cox regression model was used to determine factors associated with revision. The risk factors of age, sex, diagnosis, comorbidities, type of implant fixation, and hospital volume were analyzed. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) were calculated. RESULTS: During the study period, a total of 20,946 unicondylar knee arthroplasties were included. The number of unicondylar knee arthroplasties per year increased during the study period from 2,527 in 2006 to 4,036 in 2012. The median patient age was 64 years (interquartile range, 56 to 72 years), and 60.4% of patients were female. During the time evaluated, the 1-year revision rate decreased from 14.3% in 2006 to 8.7% in 2011. The 5-year survival rate was 87.8% (95% CI, 87.3% to 88.3%). Significant risk factors (p < 0.05) for unicondylar knee arthroplasty revision were younger age (the HR was 2.93 [95% CI, 2.48 to 3.46] for patient age of <55 years, 1.86 [95% CI, 1.58 to 2.19] for 55 to 64 years, and 1.52 [95% CI, 1.29 to 1.79] for 65 to 74 years; patient age of >74 years was used as the reference); female sex (HR, 1.18 [95% CI, 1.07 to 1.29]); complicated diabetes (HR, 1.47 [95% CI, 1.03 to 2.12]); depression (HR, 1.29 [95% CI, 1.06 to 1.57]); obesity, defined as a body mass index of ≥30 kg/m2 (HR, 1.13 [95% CI, 1.02 to 1.26]); and low-volume hospitals, denoted as an annual hospital volume of ≤10 cases (HR, 1.60 [95% CI, 1.39 to 1.84]), 11 to 20 cases (HR, 1.47 [95% CI, 1.27 to 1.70]), and 21 to 40 cases (HR, 1.31 [95% CI, 1.14 to 1.51]) (>40 cases was used as the reference). CONCLUSIONS: Apart from known risk factors, this study showed a significant negative influence of obesity, depression, and complicated diabetes on the 5-year unicondylar knee replacement survival rate. Surgical indications and preoperative patient counseling should consider these findings. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Primary stability of hamstring graft fixation with biodegradable suspension versus interference screws.

PURPOSE: During the early postoperative period, the stability of the fixation of a hamstring graft to the bone tunnel is the primary factor in limiting rehabilitation. The aim of this study was to evaluate if the initial fixation strength of a new suspension screw is comparable to that of the biodegradable interference screw fixation technique in the hamstring reconstruction of the anterior cruciate ligament (ACL). TYPE OF STUDY: Experimental laboratory study. METHODS: We evaluated the initial fixation strength of a biodegradable poly-L-lactide/tri-calcium phosphate (PLLA/TCP) screw that suspended the graft in the bone tunnel and compared it with the strength of an interference screw for fixation of hamstring grafts in ACL reconstruction using bovine knees. Single-cycle and cyclic loading tests were performed using a materials testing machine. RESULTS: The suspension screw provided a significantly higher yield load and ultimate failure load than the interference screw. There was no significant difference in the stiffness of both techniques. The typical failure mode for the suspension screw was fracture of the screw and for the interference screw it was slippage of the graft past the screw. In cyclic testing, both methods of fixation ran out to 1,000 cycles up to 250 N with a mean displacement of 2.6 mm (range, 1.8 to 3.3 mm) for the suspension screw and 4.1 mm (range, 2.3 to 6.0 mm) for the interference screw. Only the grafts fixed with the suspension screw survived a protocol with 1,000 cycles up to 400 N. CONCLUSIONS: Our biomechanical data suggest that hamstring graft fixation using a biodegradable PLLA/TCP suspension screw provides an alternative to interference screw fixation. CLINICAL RELEVANCE: Hamstring graft fixation using a suspension screw provides a reasonable alternative to interference screw fixation.

Expression and regulation of antimicrobial peptides in articular joints.

Articular joint infection is a surprisingly rare event considering the frequency of joint arthrocentesis and other invasive procedures applied to limb joints. This observation led us to the hypothesis that a local "chemical shield" in the form of antimicrobial proteins provides synovial membrane and articular cartilage with resistance to infection. We subsequently began a systematic analysis of in vitro and in vivo antimicrobially active proteins in healthy articular joints and in disease states such as pyogenic arthritis, rheumatoid arthritis, and osteoarthritis. An anatomical approach with systematic characterization combined with antimicrobial testing revealed expression and production of human antibiotic peptides and proteins. In this review, we focus on the most prominent antimicrobial proteins in articular joints, which we have identified as lysozyme, lactoferrin, secretory phospholipase A2, RNase 7, CAP37, the cathelicidin LL37, and especially the human beta-defensin-2 and -3 (HBD-2/-3). Activation pathways and possible antimicrobial functions are discussed and the involvement in non-antimicrobial processes such as tissue remodelling is also considered.

Minichromosome maintenance protein (MCM6) in low-grade chondrosarcoma: distinction from enchondroma and identification of progressive tumors.

The distinction between chondrosarcoma and enchondroma is difficult, and no reliable immunohistochemical or molecular methods are available. Differentiation is important because the therapeutic consequences range from radiologic followup to radical operation. We studied 17 chondrosarcomas (12 grade 1) and compared them with 14 enchondromas immunohistochemically by using the monoclonal antibodies Ki-MCM6 (minichromosome maintenance protein 6), Ki-S5 (Ki-67), and Ki-S2 (repp86), in addition to the established clinical criteria. In comparison with the other markers, Ki-MCM6 proved more effective at identifying proliferative activity in grade 1 chondrosarcomas. The MCM6 labeling index correlated with tumor grade and was significantly increased in grade 1 chondrosarcomas compared with enchondromas. The 5 cases of progressive chondrosarcoma also had a significantly higher MCM6 labeling index than the nonprogressive cases. Furthermore, by means of the MCM6 labeling index, many cases of progressive disease were recognized among those of uncertain malignant potential, justifying their classification as low-grade chondrosarcomas.

Cyclic strain influences the expression of the vascular endothelial growth factor (VEGF) and the hypoxia inducible factor 1 alpha (HIF-1alpha) in tendon fibroblasts.

Neovascularization is involved in beneficial and detrimental processes of tendon pathology. We investigated the influence of repetitive motion on the expression of the most important angiogenic factor, the vascular endothelial growth factor (VEGF) in the 3T3 NIH fibroblast cell line and in cultures of rat Achilles tendon fibroblasts. Monolayers of subconfluently grown cells were stretched in rectangular silicone dishes with cyclic uniaxial movement. Strain was applied over 24 h varying the frequency (0.5-1 Hz). Fibroblasts (3T3 fibroblasts and rat Achilles tendon cultures) cultivated without the application of cyclic strain released measurable VEGF amounts into their culture supernatants. Cyclic stretching of the cells with a frequency of 1 Hz resulted in an increased expression of VEGF. A low frequency (0.5 Hz) reduced VEGF expression to control levels. RT PCR revealed VEGF 121 and VEGF 165 as the only splice forms that were induced by cyclic stretching. Western blot experiments could further show that cyclic stretching induced activation of the transcription factor HIF-1alpha. These results demonstrate that mechanical factors are involved in the regulation of VEGF expression in tendon tissue.

Initial fixation strength of two bioabsorbable pins for the fixation of hamstring grafts compared to interference screw fixation: single cycle and cyclic loading.

BACKGROUND: During the early postoperative period, the fixation of a hamstring graft to the bone tunnel is the primary factor in limiting rehabilitation. HYPOTHESIS: The initial fixation strength of a double cross pin fixation technique is comparable with the biodegradable interference screw fixation technique. STUDY DESIGN: Experimental laboratory study. METHODS: The authors examined the initial fixation strength of two 3.3-mm bioabsorbable pins compared to interference screws for hamstring grafts in bovine knees. RESULTS: Analysis of yield load, maximum load, and stiffness in the single-cycle loading test showed no statistically significant differences for cross pin and interference fixation (P <.05). For cross pins and interference screws, the mean displacement under 1000 cycles to 250 N was 5.07 ( +/- 1.9) mm and 4.81 ( +/- 2.5) mm, stiffness 252 ( +/- 78) N/mm and 289 ( +/- 148) N/mm. Only grafts fixed with cross pins survived 1000 cycles to 450 N. CONCLUSION: The initial fixation strength of the double cross pin technique is comparable to that of interference screw fixation with a stiffness comparable to that of the native ACL. CLINICAL RELEVANCE: Hamstring graft fixation using two cross pins provides an alternative to bioabsorbable interference screw fixation.

Initial fixation strength of flexible all-inside meniscus suture anchors in comparison to conventional suture technique and rigid anchors: biomechanical evaluation of new meniscus refixation systems.

BACKGROUND: The newest generation of meniscus repair devices is designed to combine the benefits of the all-inside technique with the biomechanical properties of sutures. HYPOTHESIS: New flexible all-inside suture anchors have better fixation strength than rigid anchors, but there is no difference when compared to conventional horizontal and vertical mattress sutures. STUDY DESIGN: Controlled laboratory study. METHODS: In fresh-frozen bovine menisci, initial fixation strength, stiffness, and failure mode of different meniscus fixation techniques (FastT-Fix, RapidLoc, Meniscus Arrow, horizontal and vertical 2.0 Ethibond sutures) were evaluated in a computer-based materials testing machine at a rate of 12.5 mm/sec. RESULTS: The vertical and horizontal FastT-Fix suture anchors were the strongest devices with regard to pullout strength, with no significant difference compared to the vertical 2-0 Ethibond sutures. Horizontal sutures, Meniscus Arrow, and RapidLoc had significantly lower pullout strength. Vertical and horizontal FastT-Fix suture anchors showed significantly higher stiffness than the other devices. CONCLUSIONS: Biomechanical properties of flexible all-inside meniscus anchors (FastT-Fix) are comparable to conventional vertical suture techniques. Characteristics of the flexible RapidLoc are comparable to rigid anchors (Meniscus Arrow). CLINICAL RELEVANCE: From the biomechanical point of view, flexible all-inside meniscus refixation devices are an alternative to conventional suture techniques and rigid meniscus anchors.

Thromboembolic complication after arthroscopic shoulder surgery.

Thromboembolic complications after arthroscopic shoulder surgery are very unusual and need thorough investigation of the possible origin. In this case of venous pulmonary thromboembolism after arthroscopy of the shoulder, neither a hint of coagulopathy nor an anatomic abnormality could be found that explains this complication. Therefore, irritation of the subclavian vein caused by compression by the motor-driven shaver is probably one cause for our thromboembolic complication. Careful attention to positioning, fluid management, and use of traction, as well as an appreciation of shoulder anatomy to select portal placement will help decrease the common complications associated with shoulder arthroscopy. A further option to prevent thrombembolic complications in shoulder arthroscopy patients might be prophylaxis with a low-weight heparin in patients with risk factors. In conclusion, awareness of uncommon complications such as deep venous thrombosis and pulmonary embolism will help the orthpaedic surgeon promptly diagnose and treat these problems.

Arthroscopic treatment of septic arthritis in a patient with posterior stabilized total knee arthroplasty.

We report on a case of arthroscopic treatment of septic arthritis of the knee in a 73-year-old woman with a posterior stabilized knee endoprosthesis. Six months after arthroplasty of the right knee joint because of osteoarthritis, the patient experienced an erysipelas of the right lower leg after a cat bite. Although given intravenous antibiotic therapy, the patient developed septic arthritis of the right knee. Pasteurella multocida could be identified as the causative organism. The joint infection was classified as stage I according to Gächter. Via arthroscopic joint debridement, partial synovialectomy, the use of continuous irrigation-suction drains, and intravenous antibiotic therapy, the empyema could be cured without removal of the total endoprosthesis of the right knee.

Monarthritis of the pediatric knee joint: differential diagnosis after a thorn injury.

Foreign-body injury of the juvenile knee is frequently seen in the outpatient department. Arthroscopy is the most important diagnostic and therapeutic procedure along with radiographic examination in a case of typical history and clinical symptoms. In this case, an intra-articular thorn in a juvenile knee was not diagnosed at arthroscopy despite typical injury. Five months later, the boy developed knee pain and joint swelling. Bacterial infection of the knee and rheumatoid causes were excluded by serologic blood analysis several times at the children's hospital. Magnetic resonance imaging of the knee revealed an intra-articular foreign body. At a second arthroscopy, the thorn was removed and a hypertrophic plica with dependent cartilage damage of the medial femoral condyle was resected. At follow-up after 4 weeks, the boy was free of pain and swelling. After the first arthroscopy, persistent knee swelling and pain had to be taken as a hint of an intra-articular irritation. All arthroscopic surgeons should do a complete diagnostic examination of the affected joint in case of a foreign-body injury.

Primary stability of bone-patellar tendon-bone graft fixation with biodegradable pins.

PURPOSE: We evaluated the initial bone-patellar tendon-bone (BPTB) graft fixation strength of biodegradable pins compared with interference screws in anterior cruciate ligament reconstruction using bovine knees. TYPE OF STUDY: Biomechanical in vitro study. METHODS: Ten BPTB grafts from human donors fixed with 2 biodegradable 2.7-mm pins (Rigid Fix; Ethicon, Mitek Division, Norderstedt, Germany) crossing the bone block perpendicular and 10 BPTB grafts fixed with conventional biodegradable interference screws (Absolute Absorbable Interference Screw; Innovasive Devices, Marlborough, MA) underwent ultimate single-cycle failure loading at a rate of 200 mm/min. The grafts were fixed to bovine tibia to simulate young human femoral bone density. Failure mode, displacement before failure, and ultimate failure load were tested with a testing machine. The pullout force was in line with the bone tunnel to simulate a worst case scenario. RESULTS: The failure mode for cross pins was either fracture of the bone block (5 specimens) or fracture of the articular pin (5 specimens). The failure mode for interference screws was slippage past the screw in all specimens. In the single cycle loading test, the mean yield load for the biodegradable pins was 400.2 (+/- 122.4) N, maximum load, 524.6 (+/- 136.6) N, with a mean stiffness of 155.2 (+/- 32.4) N/mm. The yield load at failure for the interference screw was 402.7 (+/- 143.9) N, maximum load 515.7 (+/- 168.5) N with a mean stiffness of 168 (+/- 42) N/mm. CONCLUSIONS: Fixation of a BPTB graft with 2 biodegradable 2.7-mm pins (Rigid Fix) leads to primary stability that is comparable to fixation with biodegradable interference screws.