Increasing Rates of Arthroplasty for Psoriatic Arthritis in the United Kingdom Between 1995 and 2010.

OBJECTIVE: Arthroplasty requirements among patients with psoriatic arthritis (PsA) are not well known. This information is important to clinical and policy stakeholders for health-system planning and may serve as a surrogate for estimation of the efficacy of disease-modifying therapy. METHODS: We utilized The Health Improvement Network (THIN), a large general practice medical records database in the UK, to assess rates of primary total arthroplasty among patients with PsA and the general population between the years 1995 and 2010. Linear regression was used to estimate arthroplasty rates for the 2 cohorts during the study period, and Poisson regression was used to determine age- and sex-adjusted incidence rate ratios (IRRs) between the PsA and general population cohorts. RESULTS: We identified 5,619 patients with incident PsA and 5,090,814 eligible patients from the general population between 1995 and 2010. In total, 187 primary total arthroplasties were documented in patients with PsA, and 80,163 primary total arthroplasties were documented in the general population. A trend of increasing arthroplasty rates was observed for both the PsA (R2 = 0.809; P < 0.0001) and general population (R2 = 0.890; P < 0.0001) cohorts during the study period. After adjustment for age and sex, patients with PsA had a first arthroplasty incidence rate that was twice that of the general population (IRR 2.01 [95% confidence interval 1.73-2.34]; P < 0.0001), notably beyond the year 2003 when biologic therapies were introduced. CONCLUSION: Both the general population and patients with PsA have experienced increasing rates of first arthroplasty from 1995 to 2010, although the overall incidence rate was significantly higher for those with PsA.

Psoriasis and the risk of foot and ankle tendinopathy or enthesopathy in the absence of psoriatic arthritis: a population-based study.

OBJECTIVES: Imaging studies in patients with cutaneous psoriasis have demonstrated asymptomatic bone and tendon changes, commonly of the foot and ankle. We sought to determine if patients with cutaneous psoriasis have an increased risk of clinically significant foot and ankle tendinopathy or enthesopathy compared with the general population. METHODS: Patients with cutaneous psoriasis and a general population cohort were identified in The Health Improvement Network, a general practice medical records database from the UK. All patients with psoriatic arthritis were excluded. Cox proportional-hazards models (α=0.05) estimated the HR for development of foot and ankle tendinopathy or enthesopathy among patients with psoriasis, with adjustment for numerous covariates. RESULTS: In total, 78 630 patients with cutaneous psoriasis and 5 983 338 persons from the general population were identified. In an unadjusted model, patients with cutaneous psoriasis had a 25% increased risk of developing foot and ankle tendinopathy or enthesopathy compared with the general population (HR 1.25, 95% CI 1.20 to 1.30, p<0.0001). The HR remained unchanged and statistically significant after adjusting for covariates, and in sensitivity analyses. CONCLUSIONS: These data suggest that patients with psoriasis can have foot and ankle tendinopathy or enthesopathy without having psoriatic arthritis, presenting a diagnostic challenge to physicians. Further research is needed to elucidate mechanisms contributing to this increased risk.

Foot structure and knee joint kinetics during walking with and without wedged footwear insoles.

The relationship between static foot structure characteristics and knee joint biomechanics during walking, or the biomechanical response to wedged insoles are currently unknown. In this study, 3D foot scanning, dual X-ray absorptiometry and gait analysis methods were used to determine structural parameters of the foot and assess their relation to knee joint loading and biomechanical response to wedged insoles in 30 patients with knee osteoarthritis. In multiple linear regression models, foot fat content, height of the medial longitudinal arch and static hind foot angle were not associated with the magnitude of the knee adduction moment (R2 = 0.24, p = 0.060), knee adduction angular impulse (R2 = 0.21, p = 0.099) or 3D resultant knee moment (R2 = 0.23, p = 0.073) during gait. Furthermore, these foot structure parameters were not associated with the patients' biomechanical response to medial or lateral wedge footwear insoles (all p < 0.01). These findings suggest that static foot structure is not associated with gait mechanics at the knee, and that static foot structure alone cannot be utilized to predict an individual's biomechanical response to wedged footwear insoles in patients with knee osteoarthritis.

Syndesmotic Injury Assessment With Lateral Imaging During Stress Testing in a Cadaveric Model.

BACKGROUND: External rotation, lateral, and sagittal stress tests are commonly used to diagnose syndesmotic injuries, but their efficacy remains unclear. The purpose of this study was to characterize applied stresses with fibular motion throughout the syndesmotic injury spectrum. We hypothesized that sagittal fibular motion would have greater fidelity in detecting changes in syndesmotic status compared to mortise imaging. METHODS: Syndesmotic instability was characterized using motion analysis during external rotation, lateral, and sagittal stress tests on cadaveric specimens (n = 9). A progressive syndesmotic injury was created by sectioning the tibiofibular and deltoid ligaments. Applied loads and fibular motion were synchronously measured using a force transducer and motion capture, respectively, while mortise and lateral radiographs were acquired to quantify clinical measurements. Fibular motion in response to these 3 stress tests was compared between the intact, complete lateral syndesmotic injury and lateral injury plus a completely sectioned deltoid condition. RESULTS: Stress tests performed under lateral imaging detected syndesmotic injuries with greater sensitivity than the clinical-standard mortise view. Lateral imaging was twice as sensitive to applied loads as mortise view imaging. Specifically, half as much linear force generated 2 mm of detectable syndesmotic motion. In addition, fibular motion increased linearly in response to sagittal stresses (Pearson's r [ρ] = 0.91 ± 0.1) but not lateral stresses (ρ = 0.29 ± 0.66). CONCLUSION: Stress tests using lateral imaging detected syndesmotic injuries with greater sensitivity than a typical mortise view. In addition to greater diagnostic sensitivity, reduced loads were required to detect injuries. CLINICAL RELEVANCE: Syndesmotic injuries may be better diagnosed using stress tests that are assessed using lateral imaging than standard mortise view imaging.

Three-Dimensional Analysis of Fibular Motion After Fixation of Syndesmotic Injuries With a Screw or Suture-Button Construct.

BACKGROUND: Suture-button constructs are an alternative to screw fixation for syndesmotic injuries, and proponents advocate that suture-button constructs may allow physiological motion of the syndesmosis. Recent biomechanical data suggest that fibular instability with syndesmotic injuries is greatest in the sagittal plane, but the design of a suture-button construct, being a rope and 2 retention washers, is most effective along the axis of the rope (in the coronal plane). Some studies report that suture-button constructs are able to constrain fibular motion in the coronal plane, but the ability of a tightrope to constrain sagittal fibular motion is unknown. The purpose of this study was to assess fibular motion in response to an external rotation stress test in a syndesmotic injury model after fixation with a screw or suture-button constructs. METHODS: Eleven fresh-frozen cadaver whole legs with intact tibia-fibula articulations were secured to a custom fixture. Fibular motion (coronal, sagittal, and rotational planes) in response to a 6.5-Nm external rotation moment applied to the foot was recorded with fluoroscopy and a high-resolution motion capture system. Measures were taken for the following syndesmotic conditions: intact, complete lateral injury, complete lateral and deltoid injury, repair with a tetracortical 4.0-mm screw, and repair with a suture button construct (Tightrope; Arthrex, Naples, FL) aimed from the lateral fibula to the anterior medial malleolus. RESULTS: The suture-button construct allowed significantly more sagittal plane motion than the syndesmotic screw. Measurements acquired with mortise imaging did not detect differences between the intact, lateral injury, and 2 repair conditions. External rotation of the fibula was significantly increased in both injury conditions and was not restored to intact levels with the screw or the suture-button construct. CONCLUSION: A single suture-button placed from the lateral fibula to the anterior medial malleolus was unable to replicate the motion observed in the intact specimen when subjected to an external rotation stress test and allowed significantly more posterior motion of the fibula than when fixed with a screw in simulated highly unstable injuries. CLINICAL RELEVANCE: Fixation of a syndesmotic injury with a single suture-button construct did not restore physiological fibular motion, which may have implications for postoperative care and clinical outcomes.

Intraoperative skull-femoral traction in posterior spinal arthrodesis for adolescent idiopathic scoliosis: the impact on perioperative outcomes and health resource utilization.

STUDY DESIGN: Retrospective, single-center cohort study. OBJECTIVE: To study how the systematic use of intraoperative skull-femoral traction (IOSFT) in posterior arthrodesis for adolescent idiopathic scoliosis impacts perioperative outcomes and health resource utilization. SUMMARY OF BACKGROUND DATA: Large scoliosis curves have been associated with increased morbidity and utilization of health resources. When used with reliable neurophysiological monitoring, IOSFT has shown to be safe and to reduce curve magnitude intraoperatively. Thus, we hypothesized that the systematic use of IOSFT may contribute to reducing health resource utilization by reducing curve magnitudes intraoperatively. METHODS: Seventy-three consecutive patients with adolescent idiopathic scoliosis who underwent single-stage posterior spinal arthrodesis from 2008 to 2012 at a tertiary children's hospital were identified. Forty-five patients were operated with IOSFT (traction group) and 28 patients were operated without IOSFT (nontraction group). Outcome measures included operative time, calculated blood loss, blood transfusion requirement, traction-related complications, and cost comparisons. RESULTS: Operative time was 375.6 minutes for the traction group (P=0.0001) and 447.6 minutes for the nontraction group. Calculated blood loss was significantly less in the traction group (P=0.027). Thirty-three percent of patients in the traction group required blood transfusion compared with 64% of patients in the nontraction group (P=0.01, absolute risk reduction of 31%). There was no significant difference in curve magnitude correction (P=0.49). There were no significant complications with the use of traction. There was a significant reduction in cost per surgical procedure in the traction group (P=0.0003). CONCLUSION: The systematic use of IOSFT in posterior spinal arthrodesis for adolescent idiopathic scoliosis contributed to significant reductions in health resource utilization, with no added morbidity. Further research is warranted to investigate the generalizability of these findings. LEVEL OF EVIDENCE: 4.

Reconstruction of the medial talonavicular joint in simulated flatfoot deformity.

BACKGROUND: Reconstructing the ligamentous constraints of the medial arch associated with adult acquired flatfoot deformity remains a challenge. The purpose of this study was to test the efficacy of several reconstruction techniques of the medial arch. We hypothesized that an anatomic reconstruction of the spring ligament complex would correct the deformity better than other techniques tested. METHODS: Three reconstructions of the medial support structures were performed on each specimen to recreate the different lines of action and insertions of the medial ligamentous complex in 12 specimens with a simulated flatfoot deformity. Talonavicular and tibiocalcaneal (hindfoot) orientations were measured in the axial, sagittal, and coronal planes in the intact, flatfoot, and reconstructed conditions. RESULTS: While each reconstruction technique corrected the deformity (P < .05), proximal fixation of the graft corrected the greatest amount of talonavicular deformity while also correcting hindfoot valgus (P < .05). CONCLUSION: The fixation points and lines of action of a medial arch reconstruction have important implications on deformity correction in a flatfoot model. Despite its fidelity to the native structure, the anatomic spring ligament reconstruction provided the least amount of correction. These findings suggest that other ligamentous structures of the medial arch are critical in supporting the midfoot. CLINICAL RELEVANCE: Reconstruction of the ligamentous supports of the medial arch might be able to correct substantial amounts of deformity without osseous procedures like calcaneal osteotomies or midfoot fusions.

Leptin Deficiency and Its Effects on Tibial and Vertebral Bone Mechanical Properties in Mature Genetically Lean and Obese JCR:LA-Corpulent Rats.

Leptin signaling deficient rodents have emerged as models of obesity/insulin resistance syndrome. Altered leptin signaling, however, can affect axial and appendicular bone geometrical properties differently, and, thus, we hypothesized that leptin-deficiency would differentially influence mechanical properties of vertebrae and tibiae compared to lean rats. Mature (9 mo) leptin receptor deficient obese (cp/cp; n = 8) and lean (+/?; n = 7) male JCR:LA-corpulent rats were used to test that hypothesis. Tibiae and the sixth lumbar vertebrae (L(6)) were scanned with micro-CT and were broken in three point-bending (tibiae) or axial loading (L(6)). Supporting the hypothesis, vertebrae and tibiae were differentially affected by leptin signaling deficiency. Tibiae, but not vertebrae, were significantly shorter in obese rats and achieved a significantly greater load (>18%), displacement (>15%), and stress (>18%) at the proportional limit, relative to the lean rats. Conversely, L(6) in obese rats had significantly reduced displacement (>25%) and strain (>32%) at proportional limit, relative to the lean rats. Those combined results suggest that the etiology and duration of obesity may be important determinants of bone mechanical properties, and axial and appendicular bones may be affected differently.

Strain rate influences periosteal adaptation in mature bone.

Mechanical forces influence bone form and function. Although the adaptive capabilities of bone are well known, the nuances of the mechanical stimuli regulating adaptation remain elusive. Recently, it was suggested that strain rate influences bone adaptation, and impact exercises with high strain rates during growth may be more osteogenic than low impact aerobic exercises. Building on those findings, we hypothesized that higher rates of mechanical loading would evoke greater adaptive responses than lower rates of loading in mature bone. To test that hypothesis, skeletally mature (16 weeks) female C57BL/6 mice underwent non-invasive exogenous cantilever bending of the right tibia with a 1 Hz trapezoidal waveform for 60 s, 5 days per week, for 4 weeks. Loading was calibrated (strain gauge) to induce peak magnitudes of 1000 microepsilon on the lateral tibial middiaphysis. Mice were randomly assigned to three groups based on strain rate of the applied load: low (0.004 s(-1); n = 14), medium (0.020 s(-1); n = 15), and high (0.100 s(-1); n = 14). Calcein injections (i.p., 10 mg kg(-1)) permitted histomorphometric analyses of bone formation. Loading significantly enhanced periosteal mineral apposition rate (MAR), mineralizing surface (MS), and bone formation rate (BFR BS(-1)) in all three strain rate groups, relative to control tibiae. Furthermore, a graded dose-response relation was observed between the applied strain rate and periosteal BFR BS(-1). These increases in MAR, MS, and BFR BS(-1) were not seen on the endosteal surface. Endosteal adaptation was not statistically different between loaded and control tibiae in most endosteal indices of bone adaptation. Moreover, endosteal adaptation did not increase with strain rate. Understanding the nature of the stimuli to which bone cells respond to may underpin the development of non-pharmacological treatments devised to enhance bone mass.

Dietary restriction does not adversely affect bone geometry and mechanics in rapidly growing male wistar rats.

The present study assessed the effects of dietary restriction on tibial and vertebral mechanical and geometrical properties in 2-mo-old male Wistar rats. Two-month-old male Wistar rats were randomized to the ad libitum (n=8) or the 35% diet-restricted (DR) feeding group (n=9) for 5 mo. Tibiae and L6 vertebrae were dissected out for microcomputed tomography (microCT) scanning and subsequently fractured in biomechanical testing to determine geometrical and mechanical properties. The DR group had significantly lower mean tibial length, mass, area, and cross-sectional moment of inertia, as well as vertebral energy to maximal load. After adjustment for body mass, however, DR tibial mean maximal load and stiffness, and DR vertebral area, height, volume, and maximal load were significantly greater, relative to ad libitum means. No significant differences were found between the DR and ad libitum mineral ash fractions. Because the material properties of the tibiae between the two groups were not significantly different, presumably the material integrity of the bones was not adversely affected as a consequence of DR. The similar material characteristics were consistent with mineral ash fractions that were not different between the two groups. Vertebral maximal load and stiffness were not significant between the DR and ad libitum animals. Importantly, we show that a level of dietary restriction (35%) that is less severe than many studies (40%), and without micronutrient compensation does not adversely affect tibial and vertebral mechanical properties in young growing male rats when normalized for body mass.

Rest insertion combined with high-frequency loading enhances osteogenesis.

Mechanical loading can significantly affect skeletal adaptation. High-frequency loading can be a potent osteogenic stimulus. Additionally, insertion of rest periods between consecutive loading bouts can be a potent osteogenic stimulus. Thus we investigated whether the insertion of rest-periods between short-term high-frequency loading bouts would augment adaptation in the mature murine skeleton. Right tibiae of skeletally mature (16 wk) female C57BL/6 mice were loaded in cantilever bending at peak of 800 microepsilon, 30 Hz, 5 days/wk for 3 wk. Left tibiae were the contralateral control condition. Mice were randomly assigned into one of two groups: continuous high-frequency (CT) stimulation for 100 s (n = 9), or 1-s pulses of high-frequency stimuli followed by 10 s of rest (RI) for 100 s (n = 9). Calcein labels were administered on days 1 and 21; label incorporation was used to histomorphometrically assess periosteal and endosteal indexes of adaptation. Periosteal surface referent bone formation rate (pBFR/BS) was significantly enhanced in CT (>88%) and RI (>126%) loaded tibiae, relative to control tibiae. Furthermore, RI tibiae had significantly greater pBFR/BS, relative to CT tibiae (>72%). The endosteal surface was not as sensitive to mechanical loading as the periosteal surface. Thus short-term high-frequency loading significantly elevated pBFR/BS, relative to control tibiae. Furthermore, despite the 10-fold reduction in cycle number, the insertion of rest periods between bouts of high-frequency stimuli significantly augmented pBFR/BS, relative to tibiae loaded continually. Optimization of osteogenesis in response to mechanical loading may underpin the development of nonpharmacological regiments designed to increase bone strength in individuals with compromised bone structures.

Selected contribution: Bone adaptation with aging and long-term caloric restriction in Fischer 344 x Brown-Norway F1-hybrid rats.

Rodents are commonly used as models for human aging because of their relatively short life span, the ease of obtaining age-specific tissue samples, and lower cost. However, age-associated disease may confound inbred animal studies. For example, numerous physiologically significant lesions, such as chronic nephropathy, are more common in aged Fischer 344 (F344) rats than in other strains (Bronson RT, Genetic Effects of Aging, 1990). Conversely, F344 x Brown-Norway F1-hybrid (F344BN) rats, developed by the National Institute on Aging for aging research, live considerably longer and have fewer pathologies at any given age vs. inbred strains (Lipman RD, Chrisp CE, Hazzard DG, and Bronson RT, J Gerontol A Biol Sci Med Sci 51: 54-59, 1996). To our knowledge, there are no data regarding the effect of age on bone geometry and mechanics in this strain of rat. Furthermore, caloric restriction (CR) extends the mean and maximal life span of animals and significantly reduces age-associated disease but may have adverse consequences for bone growth and mechanics. Thus we investigated the effects of age and CR on bone geometry and mechanics in the axial and appendicular skeleton of F344 Brown-Norway rats. Ad libitum fed rats were assessed at 8 mo (young adult; n = 6), 28 mo (late middle age; n = 5), and 36 mo (senescence; n = 6). CR rats were assessed at 28 mo (n = 6). Tibiae and the sixth lumbar vertebrae (L6) were dissected, scanned (micro-computed tomography) to determine geometry, and tested mechanically. From 8 to 36 mo, there were no significant changes in L6 geometry, and only the cross-sectional moment of inertia changed (increased) with the tibia. CR-induced body mass reductions accounted for changes in L6 load at proportional limit, maximal load, and stiffness (structural properties), but altered tibial structural properties were independent of body mass. In tibiae, geometric changes dominated alterations in structural properties. Those data demonstrated that, whereas aging in ad libitum-fed animals induced minor changes in bone mechanics, axial and appendicular bones were adversely influenced by CR in late-middle-aged animals in different manners.