Which risk factors determine cartilage thickness and composition change in radiographically normal knees? - Data from the Osteoarthritis Initiative

Objective

Therapy for osteoarthritis ideally aims at preserving structure before radiographic change occurs. This study tests: a) whether longitudinal deterioration in cartilage thickness and composition (transverse relaxation-time T2) are greater in radiographically normal knees "at risk" of incident osteoarthritis than in those without risk factors; and b) which risk factors may be associated with these deteriorations.

Design

755 knees from the Osteoarthritis Initiative were studied; all were bilaterally Kellgren Lawrence grade [KLG] 0 initially, and had magnetic resonance images available at 12- and 48-month follow-up. 678 knees were "at risk", whereas 77 were not (i.e., non-exposed reference). Cartilage thickness and composition change was determined in 16 femorotibial subregions, with deep and superficial T2 being analyzed in a subset (n ​= ​59/52). Subregion values were used to compute location-independent change scores.

Results

In KLG0 knees "at risk", the femorotibial cartilage thinning score (-634 ​± ​516 ​μm) over 3 years exceeded the thickening score by approximately 20%, and was 27% greater (p ​< ​0.01; Cohen D -0.27) than the thinning score in "non-exposed" knees (-501 ​± ​319 ​μm). Superficial and deep cartilage T2 change, however, did not differ significantly between both groups (p ​≥ ​0.38). Age, sex, body mass index, knee trauma/surgery history, family history of joint replacement, presence of Heberden's nodes, repetitive knee bending were not significantly associated with cartilage thinning (r²<1%), with only knee pain reaching statistical significance.

Conclusions

Knees "at risk" of incident knee OA displayed greater cartilage thinning scores than those "non-exposed". Except for knee pain, the greater cartilage loss was not significantly associated with demographic or clinical risk factors.

OP0183 DO CARTILAGE LAMINAR COMPOSITIONAL CHANGES AS ASSESSED BY T2 RELAXOMETRY PREDICT INCIDENT AND WORSENING OF STRUCTURAL MORPHOLOGIC DAMAGE IN THE SAME PLATE 3 YEARS LATER?

Background:

To address the question whether laminar changes in knee cartilage T2 are relevant for prediction of lesion onset or progression in the same articular plate we included two different samples from the Osteoarthritis Initiative (OAI) study without radiographic osteoarthritis (ROA), i.e. so-called “healthy controls” with no ROA in either knee and being free of risk factors, and those with K-L 0 in one knee and ROA in the contralateral knee. Given the concept of the osteochondral unit, we hypothesize that superficial T2 is elevated in cartilage plates with subsequent surface damage development or worsening and deep layer T2 is elevated for those with subsequent bone marrow lesion (BML) development or worsening.

Objectives:

To analyze whether knees with subsequent morphologic cartilage and BML development or worsening exhibit elevated cartilage T2 compared to those that do not develop such structural damage in the same plate 3 years later.

Methods:

We included 63 knees from the OAI without ROA (K-L 0), but with definite ROA (K-L ≥2) in the contralateral knee, and 78 participants from the OAI healthy reference cohort.

Cartilage integrity or damage and subchondral bone marrow lesions (BMLs) were assessed for year 1 (i.e. baseline (BL) in this analysis) and year 4 (Y4) in chronological order using the semi-quantitative MOAKS scoring system.

BL deep and superficial layer cartilage T2 was computed from sagittal multi-echo spin echo MR images. Because cartilage T2 is known to display spatial variation with tissue depth, the segmented cartilages were computationally divided into superficial and deep 50%, based on the distance between the segmented cartilage surface and bone interface. Statistical analyses were performed for the femoro-tibial (FT) joint on a plate level, i.e. medial femur (MF), medial tibia (MT), lateral femur (LF) and lateral tibia (LT), using UNIANOVA with adjustment for age, body mass index, sex, and sample.

Results:

141 participants were included. Of these 79 (56%) were women, had a mean age of 59.4 ± 9.1 years and a mean body mass index of 25.8 ± 4.1 m/kg2.

52 (37%) had prevalent cartilage lesions in the medial FT joint and 67 (48%) in the lateral FT joint. For BMLs these numbers were 15 (11%) medially and 14 (10%) laterally. Worsening of FT cartilage lesions from BL to Y4 were seen in 10 (7%) medially and 21 (15%) in the lateral FT compartment. Incident FT cartilage lesions were seen in 11 (11.5%) medially and 8 knees laterally. No worsening BMLs were seen medially and 2 knees showed worsening BMLs laterally. 10 (7%) knees showed incident BMLs medially and 8 (6%) knees in the lateral FT compartment.

Deep layer T2 showed prolongation in the LT in knees with incident LT cartilage lesions (n=8, 34.5 vs. 32.7 ms, p=0.02) and for MF in knees with MF cartilage lesion worsening (n=9, 47.6 vs. 41.4 ms, p=0.01) and MF BML incidence (n=6, 45.4 vs.41.6 ms, p=0.000). Superficial T2 showed prolongation in the MT only in those knees with MT cartilage lesion worsening (n=2, 47.3 vs. 43.4 ms, p=0.03). No additional associations were seen for the superficial layer.

Conclusion:

For knees without ROA, BL deep layer T2 prolongation was seen for those who developed incident cartilage damage in the LT, and those with worsening cartilage damage and incident BMLs in the MF, respectively. Superficial T2 showed prolongation only in the MT for those with MT cartilage lesion worsening.

In summary and contrary to our hypothesis the deep cartilage layer seems to be more relevant for cartilage damage development or worsening in the same FT plate than the superficial layer.

Acknowledgment:

German Bundesministerium für Bildung und Forschung (BMBF – 01EC1408D -OVERLOAD-PREVOP)

Disclosure of Interests:

Frank Roemer: None declared, Felix Eckstein Grant/research support from: Merck, Orthotrphix, Servier, Galapagos, Kolon Tissuegene, Samumed, Novartis, Consultant of: Merck, Bioclinica, Servier, Samumed, Roche, Kolon Tissuegene, Galapagos and Novartis, Employee of: co-owner and employment with Chondrometrics, Georg Duda: None declared, Susanne Maschek Shareholder of: Stock/stock options at Condrometrics GmbH, Employee of: Employment at Condrometrics GmbH, Ali Guermazi Consultant of: AventisGalapagos, Pfizer, Roche, AstraZeneca, Merck Serono, and TissuGene, Wolfgang Wirth: None declared

Rapid detection of periprosthetic joint infection using a combination of 16s rDNA polymerase chain reaction and lateral flow immunoassay: A Pilot Study

OBJECTIVES

The objective of this study was to develop a test for the rapid (within 25 minutes) intraoperative detection of bacteria from synovial fluid to diagnose periprosthetic joint infection (PJI).

METHODS

The 16s rDNA test combines a polymerase chain reaction (PCR) for amplification of 16s rDNA with a lateral flow immunoassay in one fully automated system. The synovial fluid of 77 patients undergoing joint aspiration or primary or revision total hip or knee surgery was prospectively collected. The cohort was divided into a proof-of-principle cohort (n = 17) and a validation cohort (n = 60). Using the proof-of-principle cohort, an optimal cut-off for the discrimination between PJI and non-PJI samples was determined. PJI was defined as detection of the same bacterial species in a minimum of two microbiological samples, positive histology, and presence of a sinus tract or intra-articular pus.

RESULTS

The 16s rDNA test proved to be very robust and was able to provide a result in 97% of all samples within 25 minutes. The 16s rDNA test was able to diagnose PJI with a sensitivity of 87.5% and 82%, and a specificity of 100% and 89%, in the proof-of-principle and validation cohorts, respectively. The microbiological culture of synovial fluid achieved a sensitivity of 80% and a specificity of 93% in the validation cohort.

CONCLUSION

The 16s rDNA test offers reliable intraoperative detection of all bacterial species within 25 minutes with a sensitivity and specificity comparable with those of conventional microbiological culture of synovial fluid for the detection of PJI. The 16s rDNA test performance is independent of possible blood contamination, culture time and bacterial species.Cite this article: V. Janz, J. Schoon, C. Morgenstern, B. Preininger, S. Reinke, G. Duda, A. Breitbach, C. F. Perka, S. Geissler. Rapid detection of periprosthetic joint infection using a combination of 16s rDNA polymerase chain reaction and lateral flow immunoassay: A Pilot Study. Bone Joint Res 2018;7:12-19. DOI: 10.1302/2046-3758.71.BJR-2017-0103.R2.

Mediolateral force distribution at the knee joint shifts across activities and is driven by tibiofemoral alignment

AIMS

Tibiofemoral alignment is important to determine the rate of progression of osteoarthritis and implant survival after total knee arthroplasty (TKA). Normally, surgeons aim for neutral tibiofemoral alignment following TKA, but this has been questioned in recent years. The aim of this study was to evaluate whether varus or valgus alignment indeed leads to increased medial or lateral tibiofemoral forces during static and dynamic weight-bearing activities.

PATIENTS AND METHODS

Tibiofemoral contact forces and moments were measured in nine patients with instrumented knee implants. Medial force ratios were analysed during nine daily activities, including activities with single-limb support (e.g. walking) and double-limb support (e.g. knee bend). Hip-knee-ankle angles in the frontal plane were analysed using full-leg coronal radiographs.

RESULTS

The medial force ratio strongly correlated with the tibiofemoral alignment in the static condition of one-legged stance (R² = 0.88) and dynamic single-limb loading (R² = 0.59) with varus malalignment leading to increased medial force ratios of up to 88%. In contrast, the correlation between leg alignment and magnitude of medial compartment force was much less pronounced. A lateral shift of force occurred during activities with double-limb support and higher knee flexion angles.

CONCLUSION

The medial force ratio depends on both the tibiofemoral alignment and the nature of the activity involved. It cannot be generalised to a single value. Higher medial ratios during single-limb loading are associated with varus malalignment in TKA. The current trend towards a 'constitutional varus' after joint replacement, in terms of overall tibiofemoral alignment, should be considered carefully with respect to the increased medial force ratio. Cite this article: Bone Joint J 2017;99-B:779-87.

In vivo hip joint loads and pedal forces during ergometer cycling

The rising prevalence of osteoarthritis and an increase in total hip replacements calls for attention to potential therapeutic activities. Cycling is considered as a low impact exercise for the hip joint and hence recommended. However, there are limited data about hip joint loading to support this claim. The aim of this study was to measure synchronously the in vivo hip joint loads and pedal forces during cycling. The in vivo hip joint loads were measured in 5 patients with instrumented hip implants. Data were collected at several combinations of power and cadence, at two saddle heights. Joint loads and pedal forces showed strong linear correlation with power. So the relationship between the external pedal forces and internal joint forces was shown. While cycling at different cadences the minimum joint loads were acquired at 60RPM. The lower saddle height configuration results in an approximately 15% increase compared to normal saddle height. The results offered new insights into the actual effects of cycling on the hip joint and can serve as useful tools while developing an optimum cycling regimen for individuals with coxarthrosis or following total hip arthroplasty. Due to the relatively low contact forces, cycling at a moderate power level of 90W at a normal saddle height is suitable for patients.

Impaired fracture healing with high non-union rates remains irreversible after traumatic brain injury in leptin-deficient mice

Patients with traumatic brain injury (TBI) and long-bone fractures can show increased callus formation. This effect has already been reproduced in wild-type (wt) mice. However, the mechanisms remain poorly understood. Leptin is significantly increased following TBI, while its role in bone healing remains unclear. The aim of this study was to evaluate fracture healing in leptin-deficient ob/ob mice and to measure any possible impact of TBI on callus formation. 138 female, 12 weeks old, ob/ob mice were divided into four groups: Control, fracture, TBI and combined trauma. Osteotomies were stabilized with an external fixator; TBI was induced with Controlled Cortical Impact Injury. Callus bridging was weekly evaluated with in vivo micro-CT. Biomechanical testing was performed ex vivo. Micro-CT showed high non-union rates after three and four weeks in the fracture and combined trauma group. No differences were observed in callus volume, density and biomechanical properties at any time point. This study shows that bony bridging is impaired in the present leptin-deficient trauma model. Furthermore, the phenomenon of increased callus formation after TBI could not be reproduced in ob/ob mice, as in wt mice. Our findings suggest that the increased callus formation after TBI may be dependent on leptin signaling.

Longitudinal bone, muscle and adipose tissue changes in physically active subjects - sex differences during adolescence and maturity

OBJECTIVES

To explore changes in bone, muscle and adipose tissue composition in athletes with high physical activity levels at different stages of life.

METHODS

Thigh MRIs were acquired at baseline and 2-year follow-up for 20 young (16±1 years) and 20 mature (46±5 years) athletes (10 males, 10 females, respectively). Longitudinal changes in cross-sectional areas (CSAs) of femoral bone, quadriceps muscle, and thigh subcutaneous (SCF) and intermuscular (IMF) adipose tissue were evaluated.

RESULTS

Adolescent males displayed significant muscle (+5.0%, 95%CI: 0.8, 9.2) and bone growth (+2.9%, 95%CI: 1.3, 4.5), whereas adolescent females did not (muscle: +0.8%, 95%CI: -2.2, 3.8; bone: +1.9%, 95%CI: -2.1, 5.6). Adolescent and mature females showed significant SCF increases (+11.0%, 95%CI: 0.9, 21.1 and +6.0%, 95%CI: 0.6, 11.4, respectively), whereas adolescent and mature males did not (+7.2%, 95%CI: -8.0, 22.5 and +1.5%, 95%CI: -9.7, 11.8, respectively). Muscle and bone changes were highly correlated in adolescent males (r=0.66), mature males (r=0.75) and mature females (r=0.68) but not in adolescent females (r=-0.11).

CONCLUSIONS

The results suggest sex-specific patterns of age-related change in bone, muscle and adipose tissue, and tight coupling of bone and muscle growth. Sex-specific bone-muscle-adipose tissue relationships may have implications for understanding sex differences in fracture risk.

Do post-operative changes of neck-shaft angle and femoral component anteversion have an effect on clinical outcome following uncemented total hip arthroplasty?

The accurate reconstruction of hip anatomy and biomechanics is thought to be important in achieveing good clinical outcomes following total hip arthroplasty (THA). To this end some newer hip designs have introduced further modularity into the design of the femoral component such that neck-shaft angle and anteversion, which can be adjusted intra-operatively. The clinical effect of this increased modularity is unknown. We have investigated the changes in these anatomical parameters following conventional THA with a prosthesis of predetermined neck-shaft angle and assessed the effect of changes in the hip anatomy on clinical outcomes. In total, 44 patients (mean age 65.3 years (standard deviation (SD) 7); 17 male/27 female; mean body mass index 26.9 (kg/m²) (SD 3.1)) underwent a pre- and post-operative three-dimensional CT scanning of the hip. The pre- and post-operative neck-shaft angle, offset, hip centre of rotation, femoral anteversion, and stem alignment were measured. Additionally, a functional assessment and pain score were evaluated before surgery and at one year post-operatively and related to the post-operative anatomical changes. The mean pre-operative neck-shaft angle was significantly increased by 2.8° from 128° (SD 6.2; 119° to 147°) to 131° (SD 2.1; 127° to 136°) (p = 0.009). The mean pre-operative anteversion was 24.9° (SD 8; 7.9 to 39.1) and reduced to 7.4° (SD 7.3; -11.6° to 25.9°) post-operatively (p < 0.001). The post-operative changes had no influence on function and pain. Using a standard uncemented femoral component, high pre- and post-operative variability of femoral anteversion and neck-shaft angles was found with a significant decrease of the post-operative anteversion and slight increase of the neck-shaft angles, but without any impact on clinical outcome.

Traumatic brain injury and bone healing: radiographic and biomechanical analyses of bone formation and stability in a combined murine trauma model

INTRODUCTION

The combination of traumatic brain injury (TBI) and long-bone fractures has previously been reported to lead to exuberant callus formation. The aim of this experimental study was to radiographically and biomechanically study the effect of TBI on bone healing in a mouse model.

MATERIALS AND METHODS

138 female C57/Black6N mice were assigned to four groups (fracture (Fx) / TBI / combined trauma (Fx/TBI) / controls). Femoral osteotomy and TBI served as variables: osteotomies were stabilized with external fixators, TBI was induced with controlled cortical impact injury. During an observation period of four weeks, in vivo micro-CT scans of femora were performed on a weekly basis. Biomechanical testing of femora was performed ex vivo.

RESULTS

The combined-trauma group showed increased bone volume, higher mineral density, and a higher rate of gap bridging compared to the fracture group. The combined-trauma group showed increased torsional strength at four weeks.

DISCUSSION

TBI results in an increased formation of callus and mineral density compared to normal bone healing in mice. This fact combined with a tendency towards accelerated gap bridging leads to increased torsional strength. The present study underscores the empirical clinical evidence that TBI stimulates bone healing. Identification of underlying pathways could lead to new strategies for bone-stimulating approaches in fracture care.

BMP delivery complements the guiding effect of scaffold architecture without altering bone microstructure in critical-sized long bone defects: A multiscale analysis

Scaffold architecture guides bone formation. However, in critical-sized long bone defects additional BMP-mediated osteogenic stimulation is needed to form clinically relevant volumes of new bone. The hierarchical structure of bone determines its mechanical properties. Yet, the micro- and nanostructure of BMP-mediated fast-forming bone has not been compared with slower regenerating bone without BMP. We investigated the combined effects of scaffold architecture (physical cue) and BMP stimulation (biological cue) on bone regeneration. It was hypothesized that a structured scaffold directs tissue organization through structural guidance and load transfer, while BMP stimulation accelerates bone formation without altering the microstructure at different length scales. BMP-loaded medical grade polycaprolactone-tricalcium phosphate scaffolds were implanted in 30mm tibial defects in sheep. BMP-mediated bone formation after 3 and 12 months was compared with slower bone formation with a scaffold alone after 12 months. A multiscale analysis based on microcomputed tomography, histology, polarized light microscopy, backscattered electron microscopy, small angle X-ray scattering and nanoindentation was used to characterize bone volume, collagen fiber orientation, mineral particle thickness and orientation, and local mechanical properties. Despite different observed kinetics in bone formation, similar structural properties on a microscopic and sub-micron level seem to emerge in both BMP-treated and scaffold only groups. The guiding effect of the scaffold architecture is illustrated through structural differences in bone across different regions. In the vicinity of the scaffold increased tissue organization is observed at 3 months. Loading along the long bone axis transferred through the scaffold defines bone micro- and nanostructure after 12 months.

Experimentelle Spondylodese der Schafshalswirbelsäule Teil 1: Der Effekt des Cage-Designs auf die intervertebrale Fusion

INTRODUCTION

There has been a rapid increase in the use of interbody fusion cages as an adjunct to spondylodesis, although experimental data are lacking. A sheep cervical spine interbody fusion model was used to determine the effect of different cage design parameters (endplate-implant contact area, maximum contiguous pore) on interbody fusion.

MATERIAL AND METHOD

IN VITRO EVALUATION: 24 sheep cadaver specimens (C2-C5) were tested in flexion, extension, axial rotation, and lateral bending with a nondestructive flexibility method using a nonconstrained testing apparatus. Four different groups were examined: (1) control group (intact) ( n=24), (2) autologous tricortical iliac crest bone graft ( n=8), (3) Harms cage ( n=8), and (4) SynCage-C ( n=8). IN VIVO EVALUATION: 24 sheep underwent C3/4 discectomy and fusion: group 1: autologous tricortical iliac crest bone graft ( n=8), group 2: Harms cage filled with autologous cancellous iliac crest bone grafts ( n=8), and group 3: SynCage-C filled with autologous cancellous iliac crest bone grafts ( n=8). Radiographic scans were performed pre- and postoperatively and after 1, 2, 4, 8, and 12 weeks, respectively. At the same time points, disc space height (DSH), height index (HI), intervertebral angle (IVA), and endplate angle (EA) were measured. After 12 weeks the animals were killed and fusion sites were evaluated using biomechanical testing in flexion, extension, axial rotation, and lateral bending. Additionally, histomorphological and histomorphometrical analyses were performed.

RESULTS

Over a 12-week period the cage groups showed significantly higher values for DSH, HI, IVA, and EA compared to the bone graft. In vivo stiffness was significantly higher for the tricortical iliac crest bone graft and Harms cage than in vitro stiffness. However, there was no difference between in vitro and in vivo stiffness of the SynCage-C. Histomorphometrical evaluation showed a more progressed bone matrix formation in the Harms cage group than in both other groups.

CONCLUSION

The parameter endplate-implant contact area was not able to determine subsidence of cages. In contrast, the maximum contiguous pore of a cage significantly correlates with interbody bone matrix formation inside the cage. Additionally, there was no correlation between in vitro and in vivo stiffness of interbody fusion cages. Therefore, biomechanical in vitro studies are not able to determine in vivo outcome of fusion cages. Animal experimental evaluations of interbody fusion cages are essential prior to clinical use.

Evidence of imbalanced adaptation between muscle and tendon in adolescent athletes

Adolescence may be regarded as a critical phase of tissue plasticity in young growing athletes, as the adaptation process of muscle-tendon unit is affected by both environmental mechanical stimuli and maturation. The present study investigated potential imbalances of knee extensor muscle strength and patellar tendon properties in adolescent compared with middle-aged athletes featuring long-term musculotendinous adaptations. Nineteen adolescent elite volleyball athletes [(A), 15.9 ± 0.6 years] and 18 middle-aged competitively active former elite volleyball athletes [(MA), 46.9 ± 0.6 years] participated in magnetic resonance imaging and ultrasound-dynamometry sessions to determine quadriceps femoris muscle strength, vastus lateralis morphology and patellar tendon mechanical and morphological properties. There was no significant age effect on the physiological cross-sectional area of the vastus lateralis and maximum knee extension moment (P > 0.05) during voluntary isometric contractions. However, the patellar tendon cross-sectional area was significantly smaller (A: 107.4 ± 27.5 mm(2) ; MA: 121.7 ± 39.8 mm(2) ) and the tendon stress during the maximal contractions was significantly higher in adolescent compared with the middle-aged athletes (A: 50.0 ± 10.1 MPa; MA: 40.0 ± 9.5 MPa). These findings provide evidence of an imbalanced development of muscle strength and tendon mechanical and morphological properties in adolescent athletes, which may have implications for the risk of tendon overuse injuries.

Rodent animal models of delayed bone healing and non-union formation: a comprehensive review

Despite the growing knowledge on the mechanisms of fracture healing, delayed healing and non-union formation remain a major clinical challenge. Animal models are needed to study the complex process of normal and impaired fracture healing and to develop new therapeutic strategies. Whereas in the past mainly large animals have been used to study normal and impaired fracture healing, nowadays rodent models are of increasing interest. New osteosynthesis techniques for rat and mice have been developed during the last years, which allowed for the first time stable osteosynthesis in these animals comparable to the standards in large animals and humans. Based on these new implants, different models in rat and mice have been established to study delayed healing and non-union formation. Although in humans the terms delayed union and non-union are well defined, in rodents definitions are lacking. However, especially in scientific studies clear definitions are necessary to develop a uniform scientific language and allow comparison of the results between different studies. In this consensus report, we define the basic terms "union", "delayed healing" and "non-union" in rodent animal models. Based on a review of the literature and our own experience, we further provide an overview on available models of delayed healing and non-union formation in rats and mice. We further summarise the value of different approaches to study normal and delayed fracture healing as well as non-union formation, and discuss different methods of data evaluation.

An experimental setup to evaluate innovative therapy options for the enhancement of bone healing using BMP as a benchmark--a pilot study

Critical or delayed bone healing in rat osteotomy (OT) models is mostly achieved through large defects or instability. We aimed to design a rat OT model for impaired bone healing based on age, gender and parity. The outcome should be controllable through variations of the haematoma in the OT including a bone morphogenetic protein (BMP) 2 guided positive control. Using external fixation to stabilise femoral a 2 mm double OT in 12 month old, female Sprague Dawley rats after a minimum of 3 litters healing was characterised following in situ haematoma formation (ISH-group)), transplantation of a BMP charged autologous blood clot (BMP-group) and the artificial blood clot only (ABC-group) into the OT-gap. In vivo micro-computer tomography (µCT) scans were performed after 2, 4 and 6 weeks. After 6 weeks specimens underwent histological analyses. In µCT examinations and histological analyses no bony bridging was observed in all but one animal in the ISH-group. In the BMP group complete bridging was achieved in all animals. The ABC-group showed less mineralised tissue formation and smaller bridging scores during the course of healing than the ISH-group. In this pilot study we introduce a model for impaired bone healing taking the major biological risk factors into account. We could show that the in situ fracture haematoma is essential for bone regeneration. Using BMP as a positive control the presented experimental setup can serve to evaluate innovative therapeutical concepts in long bone application.

Structural Dependence of the Elastic Constants of Polymeric Langmuir-Blodgett Films Studied Using Brillouin Scattering

We have used Brillouin scattering to study the dependence of the elastic constants of uniaxial polymeric Langmuir-Blodgett thin films on the thickness of the polymeric molecule monolayers. With increasing monolayer thickness, an overall decrease in the elastic constants and an increase in the refractive index n33 was observed.

[Perspectives of clinical stem cell therapy in the treatment of musculoskeletal diseases in Germany]

AIM

The treatment of large bone defects remains a challenge for the orthopaedic surgeon. Regenerative therapies with the use of mesenchymal stem cells (MSC) may provide an alternative to autogenous bone transplantation, callus distraction or the use of allografts.

MATERIAL AND METHODS

On the occasion of an expert workshop of the German Society for Orthopaedic and Trauma Surgery, a literature search regarding studies with the use of MSC was performed to evaluate its potential for future clinical studies. Furthermore, the legislative requirements were examined.

RESULTS

Various in vitro and animal studies showed the benefit of MSC in bone regeneration. However, there are sparse data from clinical studies. Due to recent legislative changes there are several regulatory demands to meet if clinical studies are performed with MSC.

CONCLUSIONS

For further evaluation of the role of MSC in the treatment of bone defects there is a need for clinical trials. The current paper provides some assistance for the successful application for clinical trials with MSC. Planning and performance of these studies may require early consultation with the regulatory authorities and cooperation of research centres in order to obtain authorisation for the evaluation of MSC. Preclinical data have to be obtained according to good laboratory practice with equivalent protocols that will be used in the clinical trials. In the latter the implementation of the guidelines for good clinical practice are mandatory.

Antioxidant capacity in renal transplant patients

The aim of the study was to analyse the relation between total antioxidant capacity and immunosuppressive therapies, renal function and hematocrit in kidney transplant patients. The study included 46 adult patients during the maintenance period (>1 year) following renal transplantation, treated with different combinations of immunosuppressive agents--most commonly with cyclosporine (n = 23) or tacrolimus (n = 15). The total antioxidant capacity (TAOC) of plasma was measured using Trolox-equivalent antioxidant capacity (TEAC) assay. Patients treated with cyclosporine had significantly greater TAOC compared with those treated with tacrolimus (1.16 +/- 0.46 mmol/L vs. 0.80 +/- 0.37 mmol/L, p = 0.018, respectively). There was a significantly negative correlation between TAOC and plasma creatinine (rs = -0.551, p = 0.033) and a positive correlation between TAOC and creatinine clearance or hematocrit in patients treated with tacrolimus but not with cyclosporine (r = 0.525, p = 0.045 or rs = 0.629, p = 0.012, respectively). Immunosuppressive therapy with cyclosporine was associated with higher TAOC. Anemia can be an independent risk factor for an increase of oxidative stress. Although subject numbers werelimited, TAOC was positively associated with renal function in patients treated with tacrolimus.

Effect of mechanical stimulation on osteoblast- and osteoclast-like cells in vitro

Bone-forming osteoblasts and bone-resorbing osteoclasts play an important role during maintenance, adaptation and healing of bone, and both cell types are influenced by physical activity. The aim of the present study was to investigate the effect of a narrow mechanical stimulation window on osteoblast- and osteoclast-like cells. Primary human cells were cultured on a bone-like structure (dentine) and three-point bending with approximately 1,100 microstrain was applied to the dentine at varying frequencies (0.1 and 0.3 Hz) and duration (1, 3 and 5 min daily over 5 days) resulting in different patterns of mechanical stimulation of osteoblast- and osteoclast-like cells. The longest stimulation (5 min at 0.1 Hz) induced a significant increase in osteoblast alkaline phosphatase activity and a significant decrease in osteoprotegerin (OPG) production, and resulted in a significant increase in the soluble receptor activator of NF-kappaB ligand (sRANKL)/OPG ratio towards sRANKL in comparison to the unstimulated osteoblast-like cells. All stimulations caused a significant decrease in collagen type 1 synthesis. Stimulation for 1 min at 0.3 Hz decreased the fusion and resorption activity of the osteoclast-like cells. These results demonstrate a direct effect of mechanical stimuli on osteoblast-like cells as well as on osteoclast formation and activity in vitro. The change in the sRANKL/OPG ratio towards the stimulation of osteoclastogenesis stresses the necessity to investigate the effect of the same stimulation parameter on the co-culture of both cell types.

Effects of dexamethasone and celecoxib on calcium homeostasis and expression of cyclooxygenase-2 mRNA in MG-63 human osteosarcoma cells

OBJECTIVE

Glucocorticoids and selective COX-2 inhibitors are potent anti-inflammatory agents. They are also suggested to influence bone physiology and remodeling. Here we searched for effects of dexamethasone and celecoxib on crucial parameters of bone physiology that could be therapeutically relevant.

METHODS

The human osteosarcoma cell line MG-63 was used to measure effects of these drugs on (i) intracellular calcium concentration ([Ca2+]i) using a microfluorometric technique, (ii) alkaline phosphatase and osteocalcin levels (EIA) and (iii) the expression of cox-2 mRNA (quantitative real time PCR). Measurements were performed in Vitamine D-incubated quiescent cells and in cells stimulated with TNF-alpha and IL-1beta.

RESULTS

We found the cytokine-stimulation to increase [Ca2+]i which was prevented by dexamethasone already after 30 min and still after 48 h. Dexamethasone was without any effect on [Ca2+]i in quiescent cells. Celecoxib had no measurable short-term or long-term effects neither in quiescent nor in stimulated cells. Vitamin D stimulated the expression of cox-2 mRNA which was further enhanced by TNF-alpha/IL-1beta. Dexamethasone did not have any measurable effects on COX-2 expression after 30 min, but a pronounced inhibition was seen after 48 h. In contrast, celecoxib had no effect on COX-2 expression. Neither of the drugs had any effect on the secretion of alkaline phosphatase and osteocalcin.

CONCLUSION

We found dexamethasone to inhibit the [Ca2+]i increase in MG-63 cells following stimulation and to reduce considerably COX-2 expression via the genomic pathway. In contrast, celecoxib did not show any measurable short-term or long-term effects on the parameters of bone physiology measured.

Temporal profile of microvascular disturbances in rat tibial periosteum following closed soft tissue trauma

BACKGROUND AND AIMS

Bone devascularization due to impaired periosteal perfusion following fracture with severe soft tissue trauma has been proposed to precede and underlie perturbed bone healing. The extent and temporal relationship of periosteal microcirculatory deteriorations after severe closed soft tissue injury (CSTI) are not known. We hypothesized that periosteal microcirculation is adversely affected and the manifestation of trauma-initiated microvascular impairment in periosteum is substantially prolonged following CSTI.

MATERIAL AND METHODS

Using the controlled-impact injury device, we induced standardized CSTI in the tibial compartment of 35 isoflurane-anesthetized rats. Following the trauma the rats were assigned to five groups, differing in time of analysis (2 h, 24 h, 48 h, 1 and 6 weeks). Non-injured rats served as controls. Before the metaphyseal/diaphyseal periosteum was surgically exposed, intramuscular pressure within tibial compartment was measured. Using intravital fluorescence microscopy (IVM) we studied the microcirculation of the tibial periosteum. We calculated the edema index (EI) by measuring the skeletal muscle wet-to-dry weight ratio (EI = injured limb/contralateral limb).

RESULTS

Microvascular deteriorations of periosteal microhemodynamics caused by isolated CSTI were reflected by persistent decrease in nutritive perfusion, markedly prolonged increase in microvascular permeability associated with increasingly sustained leukocyte rolling and adherence throughout the entire study period, mostly pronounced 48 h after the trauma. Peak level in capillary leakage coincided with the maximum leukocyte adherence, tissue pressure, and edema. Microcirculation of tibial periosteum in control rats demonstrated a homogeneous perfusion with no capillary or endothelial dysfunction.

CONCLUSION

Isolated CSTI in absence of a fracture exerts long-lasting disturbances in periosteal microcirculation, suggesting a delayed temporal profile in manifestation of CSTI-induced periosteal microvascular dysfunction and inflammation. These observations may have therapeutic implications in terms of preserving periosteal integrity and considering the interaction of skeletal muscle damage and periosteal microvascular injury during management of musculoskeletal trauma.

Dose-dependent effects of combined IGF-I and TGF-beta1 application in a sheep cervical spine fusion model

Combined IGF-I and TGF-beta1 application by a poly-(D,L-lactide) (PDLLA) coated interbody cage has proven to promote spine fusion. The purpose of this study was to determine whether there is a dose-dependent effect of combined IGF-I and TGF-beta1 application on intervertebral bone matrix formation in a sheep cervical spine fusion model. Thirty-two sheep underwent C3/4 discectomy and fusion. Stabilisation was performed using a titanium cage coated with a PDLLA carrier including no growth factors in group 1 ( n=8), 75 micro g IGF-I plus 15 micro g TGF-beta1 in group 2 ( n=8), 150 micro g IGF-I plus 30 micro g TGF-beta1 in group 3 ( n=8) and 300 micro g IGF-I plus 60 micro g TGF-beta1 in group 4 ( n=8). Blood samples, body weight and temperature were analysed. Radiographic scans were performed pre- and postoperatively and after 1, 2, 4, 8, and 12 weeks. At the same time points, disc space height and intervertebral angle were measured. After 12 weeks, the animals were killed and fusion sites were evaluated using quantitative computed tomographic (CT) scans to assess bone mineral density, bone mineral content and bony callus volume. Biomechanical testing was performed and range of motion, and neutral and elastic zones were determined. Histomorphological and histomorphometrical analysis were carried out and polychrome sequential labelling was used to determine the time frame of new bone formation. In comparison to the group without growth factors (group 1), the medium- and high-dose growth factor groups (groups 3 and 4) demonstrated a significantly higher bony callus volume on CT scans, a higher biomechanical stability, an advanced interbody bone matrix formation in histomorphometrical analysis, and an earlier bone matrix formation on fluorochrome sequence labelling. Additionally, the medium- and high-dose growth factor groups (groups 3 and 4) demonstrated a significantly higher bony callus volume, a higher biomechanical stability in rotation, and an advanced interbody bone matrix formation in comparison to the low-dose growth factor group (group 2). No significant difference could be determined between the medium- and the high-dose growth factor groups (groups 3 and 4, respectively). The local application of IGF-I and TGF-beta1 by a PDLLA-coated cage significantly improved results of interbody bone matrix formation in a dose-dependent manner. The best dose-response relationship was achieved with the medium growth factor dose (150 micro g IGF-I and 30 micro g TGF-beta1). With an increasing dose of these growth factors, no further stimulation of bone matrix formation was observed. Although these results are encouraging, safety issues of combined IGF-I and TGF-beta1 application for spinal fusion still have to be addressed.

[Experimental fusion of the sheep cervical spine. Part II: Effect of growth factors and carrier systems on interbody fusion]

INTRODUCTION

A sheep cervical spine interbody fusion model was used to determine the effect of different carriers and growth factors on interbody bone matrix formation. The purpose of this study was to compare the efficacy and safety of combined IGF-I and TGF-beta1 application with BMP-2 application in spinal fusion. Additionally, a new poly (D, L-lactide) carrier system was compared to a collagen sponge carrier.

METHOD

Forty sheep underwent C3/4 discectomy and fusion: group 1: titanium cage ( n=8), group 2: titanium cage coated with a PDLLA carrier (n=8), group 3: titanium cage coated with a PDLLA carrier including BMP-2 ( n=8), group 4: titanium cage with a collagen carrier including BMP-2 ( n=8), and group 5: titanium cage coated with a PDLLA carrier including IGF-I and TGF-beta1 ( n=8). Blood samples, body weight, and temperature were analyzed. Radiographic scans were performed pre- and postoperatively and after 1, 2, 4, 8, and 12 weeks, respectively. At the same time points, disc space height (DSH) and intervertebral angle (IVA) were measured. After 12 weeks the animals were killed and fusion sites were evaluated using functional radiographic views in flexion and extension. Quantitative computed tomographic scans (QCT) were performed to assess bone mineral density (BMD), bone mineral content (BMC), and bony callus volume (BCV). Biomechanical testing was carried out in flexion, extension, axial rotation, and lateral bending. Range of motion (ROM), neutral zone (NZ), and elastic zone (EZ) were determined. Histomorphological and histomorphometrical analyses were performed and polychrome sequential labeling was used to determine the time frame of new bone formation.

RESULTS

In comparison to the non-coated cages, all PDLLA-coated cages showed significantly higher values for BMD of the callus and bone volume/total volume ratio. In comparison to the cage groups (groups 1 and 2), the cage plus BMP-2 (groups 3 and 4) and the cage plus IGF-I and TGF-beta1 group (group 5) demonstrated a significantly higher fusion rate in radiographic findings, a higher biomechanical stability, an advanced interbody fusion in histomorphometric analysis, and an accelerated interbody fusion on fluorochrome sequence labeling. BMP-2 application by the PDLLA carrier system (group 3) demonstrated significantly higher bony callus volume than BMP-2 application by a collagen sponge carrier (group 4). The BMP-2 group (group 3) showed significantly lower residual motion on functional radiographic evaluation and higher intervertebral bone matrix formation on fluorochrome sequence labeling at 9 weeks in comparison to the IGF-I/TGF-beta1 group (group 5). In contrast, the IGF-I/TGF-beta1 group (group 5) showed a significantly higher bone mineral density of the callus than the BMP-2 group (group 3).

CONCLUSION

PDLLA coating of cervical spine interbody fusion cages as a delivery system for growth factors was effective and safe. In comparison to the collagen sponge carrier, the new PDLLA carrier system was able to improve results of interbody bone matrix formation. Both growth factors (BMP-2 and combined IGF-I and TGF-beta1) significantly accelerated results of interbody fusion. Based on these preliminary results, the combined IGF-I/TGF-beta1 application yields results equivalent to BMP-2 application at an early time in anterior sheep cervical spine fusion.

Comparison of BMP-2 and combined IGF-I/TGF-ss1 application in a sheep cervical spine fusion model

Growth factors have proven to promote spine fusion. However, no comparative evaluation of growth factors in spinal fusion has yet been performed. The purpose of this study was to compare the efficacy and safety of combined IGF-I and TGF-ss1 application with BMP-2 application and autologous cancellous bone graft at an early time point in a sheep cervical spine fusion model. Thirty-two sheep underwent C3/4 discectomy and fusion. They were divided into four groups, according to their treatment: group 1, titanium cage ( n=8); group 2, titanium cage filled with autologous cancellous iliac crest bone grafts ( n=8); group 3, titanium cage coated with a poly-(D,L-lactide) (PDLLA) carrier including BMP-2 (5% w/w) ( n=8); group 4, titanium cage coated with a PDLLA carrier including IGF-I (5% w/w) and TGF-ss1 (1% w/w) ( n=8). Blood samples, body weight and temperature were analysed. Radiographic scans were performed pre- and postoperatively and after 1, 2, 4, 8 and 12 weeks. At the same time points, disc space height and intervertebral angle were measured. After 12 weeks, the animals were killed and fusion sites were evaluated using functional radiographic views in flexion and extension. Quantitative computed tomographic scans were performed to assess bone mineral density, bone mineral content and bony callus volume. Biomechanical testing was carried out and the values for range of motion, and neutral and elastic zone were determined. Histomorphological and histomorphometrical analysis were performed and polychrome sequential labelling was used to determine the time frame of new bone formation. The results showed that, in comparison to the group treated with the cage alone (group 1), the cage plus BMP-2 group (group 3) and the cage plus IGF-I and TGF-ss1 group (group 4) demonstrated a significantly higher fusion rate in radiographic findings, a higher biomechanical stability, a more advanced interbody fusion in histomorphometrical analysis, and an accelerated interbody fusion on fluorochrome sequence labelling. In comparison to the bone graft group (group 2), the BMP-2 (group 3) and IGF-I/TGF-ss1 group (group 4) showed significantly less residual motion on functional radiographic evaluation, higher bone mineral density of the callus and higher biomechanical stability in extension, rotation and bending. The BMP-2 group showed significantly less residual motion on functional radiographic evaluation and higher intervertebral bone matrix formation on fluorochrome sequence labelling at 9 weeks in comparison to the IGF-I/TGF-ss1 group. In contrast, the IGF-I/TGF-ss1 group showed a significantly higher bone mineral density of the callus than the BMP-2 group. In comparison to the autologous cancellous bone graft group, both growth factors (BMP-2 and combined IGF-I and TGF-ss1) significantly improved the biomechanical results of interbody fusion. No systemic side effects were observed for either growth factor. On the basis of these preliminary results, it would appear that combined IGF-I/TGF-ss1 application yields equivalent results to BMP-2 application at an early time point in anterior sheep cervical spine fusion.

Biomechanical comparison of cervical spine interbody fusion cages

STUDY DESIGN

An in vitro biomechanical study of cervical spine interbody fusion cages using a sheep model was conducted.

OBJECTIVES

To evaluate the biomechanical effects of cervical spine interbody fusion cages, and to compare three different cage design groups.

SUMMARY AND BACKGROUND DATA

Recently, there has been a rapid increase in the use of cervical spine interbody fusion cages as an adjunct to spondylodesis. These cages can be classified into three design groups: screw, box, or cylinder designs. Although several comparative biomechanical studies of lumbar interbody fusion cages are available, biomechanical data for cervical spine constructs are lacking. Additionally, only limited data are available concerning comparative evaluation of different cage designs.

METHODS

In this study, 80 sheep cervical spines (C2-C5) were tested in flexion, extension, axial rotation, and lateral bending with a nondestructive stiffness method using a nonconstrained testing apparatus. Three-dimensional displacement was measured using an optical measurement system (Qualysis). Complete discectomy (C3-C4) was performed. Cervical spine interbody fusion cages were implanted according to manufacturers' information. Eight spines in each of the the following groups were tested: intact, autologous iliac bone graft, two titanium screws (Novus CTTi; Sofamor Danek, Koln, Germany), two titanium screws (BAK-C 8 mm; Sulzer Orthopedics, Baar, Switzerland), one titanium screw (BAK-C 12 mm; Sulzer Orthopedics), carbon box (Novus CSRC; Sofamor Danek), titanium box (Syncage; Synthes, Bochum, Germany), titanium mesh cylinder (Harms; DePuy Acromed, Sulzbach, Germany), titanium cylinder (MSD; Ulrich, Ulm, Germany), and titanium cylinder (Kaden; BiometMerck, Berlin, Germany). The mean apparent stiffness values were calculated from the corresponding load-displacement curves. Additionally, cage volume and volume-related stiffness was determined.

RESULTS

After cervical spine interbody fusion cage implantation, flexion stiffness increased, as compared with that of the intact motion segment. On the contrary, rotation stiffness decreased after implantation of a cervical spine interbody fusion cage, except for the Novus CSRC, Syncage, and Kaden-Cage. If two screws were inserted (Novus CTTi and BAK-C 8 mm), there was no significant difference in flexion stiffness between screw and cylinder design groups. If one screw was inserted (BAK-C 12 mm), flexion stiffness was higher for cylinder designs (P < 0.05). Extension and bending stiffness were always higher with cylinder designs (P < 0.05). Volume-related stiffness for flexion extension and bending was highest for the Harms cage (P < 0.05). There was no difference for rotation volume-related stiffness between Harms and Syncage.

CONCLUSIONS

The biomechanical results indicate that design variations in screw and cylinder design groups are of little importance. In this study, however, cages with a cylinder design were able to control extension and bending more effectively than cages with a screw design.

[Dorsal oblique pelvic fixator: development and biomechanical testing]

In haemodynamically unstable patients with an unstable pelvic ring injury the primary stabilisation of the pelvis and thus reduction of pelvic volume is important for the success of the treatment. The pelvic C-clamp is an approved emergency device for these unstable pelvic ring injuries. A secondary procedure though is necessary in most of the cases with a hig rate of wound problems in already traumatized soft tissue areas. The ventrally placed external fixator is a simple and quick procedure with little soft tissue damage. Though primary stability is sufficient even for C-type injuries, biomechanic stability of the posterior pelvic ring is often insufficient for mobilization. Based on biomechanic considerations, a new dorsal oblique pelvic external fixator was developed for pelvic C-type injuries. With the advantages of the supraacetabular fixator and two additional Schanz screws the ventral fixator should stabilize the posterior pelvic ring with comparable stability to the pelvic C-clamp. A primary and already definitive minimal invasive stabilization of the posterior pelvic ring was the aim. In the first series several variations of this asymmetric fixator with two different Schanz screw applications were tested biomechanically. In a second series the favorite version was tested versus the supraacetabular fixator and the pelvic C-clamp. Both of the biomechanic test series were performed with artificial pelves in the one leg stance model in the material testing machine. SI disruption and sacral fracture were the posterior instability types in 6 pelves each. There was no statistically significant difference between the dorsal oblique fixator and the pelvic C-clamp. But the new fixator was significantly more stable than the supraacetabular fixator or the new fixator without pretension.

Comparison of three different plating techniques for the dorsum of the distal radius: a biomechanical study

Three different plating techniques were used on experimentally produced dorsally displaced distal radius fractures in cadavers and were tested in 4-point bending: a AO 3.5-mm T plate (group 1), two 2. 0-mm titanium plates 60 degrees to each other (group 2), and the AO pi plate (group 3). A metaphyseal defect was simulated by a dorsally open wedge osteotomy. The tests show that the 2-mm double-plating technique has superior stiffness and statistically equivalent bending and bone gap to failure compared with the AO 3.5-mm T plate or the pi plate when applied to the unstable distal radius fracture model. (J Hand Surg 2000; 25A:29-33.

novel Award Second Prize Paper. Functional monitoring during rehabilitation following anterior cruciate ligament reconstruction

OBJECTIVE

It was hypothesized that testing of ambulatory function and more demanding activities were more appropriate predictors of dynamic knee function before and after reconstruction of the anterior cruciate ligament than conventional measures of functional evaluation. It was assumed that assessment of dynamic plantar pressure distribution would represent a practical tool for guidance of the rehabilitation process after anterior cruciate ligament reconstruction.

DESIGN

In a prospective study, 10 patients with isolated anterior cruciate deficiency were examined before and after replacement of the anterior cruciate (6, 12, 24 weeks) in a standardized technique.

BACKGROUND

Today, functional assessment following anterior cruciate ligament reconstruction relies on clinical examination supplemented by instrumented testing of knee laxity and on isokinetic evaluation of muscle performance. Gait analysis has not been used as a quantitative measure of rehabilitation progress after surgery.

METHODS

All patients were subjected to the same physiotherapy protocol. The clinical results were documented using the International Knee Documentation Committee (IKDC) protocol and the degree of knee laxity by an instrumented anterior drawer test. Muscular performance was evaluated by isokinetic testing. Dynamic pedography (EMED-SF 4) was performed to compare the non-injured and the operated leg during level walking and while descending stairs.

RESULTS

Gait performance six weeks after surgery tended to be inferior to preoperative and late postoperative values. While the slight increase of maximum knee extensor torque in the operated leg and the improvement of the IKDC score during the rehabilitation period were not statistically significant, a significantly decreased gait asymmetry could be observed 12 weeks after surgery. The descending stairs test revealed functional deficits better than level walking. The latter test exhibited a strong correlation with the preoperative IKDC level and the maximum knee extensor deficit at 60 degrees /s.

CONCLUSIONS

Dynamic pedography during level walking and while descending stairs is a valuable tool for monitoring the rehabilitation process after anterior cruciate ligament reconstruction.

RELEVANCE

Due to the better resolution of functional deficits compared with indirect measures of function (isokinetic testing) assessment of the plantar pressure distribution may provide a more individualized adaptation for the rehabilitation program.