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This study investigated the healing potential of allograft from bisphosphonate-treated animals in anterior lumbar spine interbody fusion. Three levels of anterior lumbar interbody fusion with Brantigan cages were performed in two groups of five landrace pigs. Empty Brantigan cages or cages filled with either autograft or allograft were located randomly at different levels. The allograft materials for the treatment group were taken from the pigs that had been fed with alendronate, 10 mg daily for 3 months. The histological fusion rate was 2/5 in alendronate-treated allograft and 3/5 in non-treated allograft. The mean bone volume was 39% and 37.2% in alendronate-treated or non-treated allograft (NS), respectively. No statistical difference was found between the same grafted cage comparing two groups. The histological fusion rate was 7/10 in all autograft cage levels and 5/10 in combined allograft cage levels. No fusion was found at all in empty cage levels. With the numbers available, no statistically significant difference was found in histological fusion between autograft and allograft applications. There was a significant difference of mean bone volume between autograft (49.2%) and empty cage (27.5%) (P<0.01). In conclusion, this study did not demonstrate different healing properties of alendronate-treated and non-treated allograft for anterior lumbar interbody fusion in pigs. [ABSTRACT FROM AUTHOR]

Background Impaction grafting can be achieved inside the spinal fusion cages, but its effect on bone graft incorporation and spinal fusion has not been studied. Animals and methods We investigated the effect of impaction grafting on the bone graft healing and fusion potential of ß-tricalcium phosphate (ß-TCP) inside the carbon fiber reinforced spinal fusion device (Brantigan cage) in 10 Danish landrace pigs. Lumbar spine interbody fusion of L2/3, L4/5 and L6/7 using carbon fiber cages was performed on each pig. Cages filled with either loosely-packed autologous iliac bone graft, rod-impacted autologous bone graft or ß-TCP were randomly distributed to the three fusion levels. Half of the animals were followed for 8 weeks, and the other half for 16 weeks. Results Radiographs and CT evaluations showed that autograft levels had significantly better results than ß-TCP levels (p<0.001 Fisher's Exact Test). However, the difference between impacted and loosely-packed levels was not significant. Histomorphometric analysis showed no difference between the loosely-packed and impacted cages with regard to bone volume, bone marrow volume, cartilage and fibrous tissue volume, while both of the autograft levels differed from the ß-TCP levels in all of the aforementioned parameters. Fluorochrome studies demonstrated that bone mineral apposition rate was significantly higher in the impacted cages than in the loosely-packed cages at 16 weeks. Interpretation Manual impaction of autologous bone graft into the carbon fiber cages resulted in a faster mineral apposition rate by 16 weeks. Bone ingrowth and spinal fusion were not influenced by impaction grafting. [ABSTRACT FROM AUTHOR]

Comments on the measurement assessments of femoral neck anteversion (FNA) by conventional radiography and computed tomography. Definition of systematical measurement error; Accuracy of the proposed method for measuring the FNA; Parameters used in the description of the reproducibility and accuracy of the FNA measurement.

Background: Distal radius fractures can adversely affect wrist function; for men with this fracture, the role played by fracture severity, age and osteoporosis on fracture outcome has not been sufficiently studied.Objective: To describe patient-reported outcome and the association with bone integrity, fracture severity and future fracture risk among young and older men with distal radius fracture.Methods: This prospective study includes 133 men with acute distal radius fracture, mean age 54 (range 21-88), who were followed for 12 months. They were categorized as younger (< 65) and older (65+). Main outcome was DASH (Disability of the Arm, Shoulder and Hand) at 12 months; DASH > 15 was defined as poor outcome. Fractures were classified and radiographic displacement identified at initial presentation and follow-up. BMD was measured and FRAX 10-year probability of fracture calculated.Results: Disability was higher in older men (DASHmedian 10 vs 2; p = 0.002); a clinically meaningful difference (ΔDASH = 10, p = 0.017) remained after adjustment for displacement, fracture classification and treatment method. Almost 50% of older men vs 14% in younger had poor outcome, p < 0.001. Bone mineral density did not independently predict outcome. Older men with a displaced fracture at initial presentation had greater disability (DASHmedian, IQR 45, 14;73) and risk of fracture (FRAXmajor osteoporotic 14, 8;21).Conclusion: Men over the age of 65 with a distal radius fracture are more likely to have post-fracture disability regardless of radiographic appearance. Fracture displacement, indicating impaired bone strength, is also more common and associated with an increased risk of fracture within 10-years. Secondary fracture prevention should therefore be considered in men presenting with distal radius fracture. [ABSTRACT FROM AUTHOR]

Objective: To estimate the prevalence of degenerative and spondyloarthritis (SpA)-related magnetic resonance imaging (MRI) findings in the spine and sacroiliac joints (SIJs) and analyse their association with gender and age in persistent low back pain (LBP) patients.Methods: Degenerative and SpA-related MRI findings in the whole spine and SIJs were evaluated in Spine Centre patients aged 18-40 years with LBP.Results: Among the 1,037 patients, the prevalence of disc degeneration, disc contour changes and vertebral endplate signal (Modic) changes were 87 % (±SEM 1.1), 82 % (±1.2) and 48 % (±1.6). All degenerative spinal findings were most frequent in men and patients aged 30-40 years. Spinal SpA-related MRI findings were rare. In the SIJs, 28 % (±1.4) had at least one MRI finding, with bone marrow oedema being the most common (21 % (±1.3)). SIJ erosions were most prevalent in patients aged 18-29 years and bone marrow oedema in patients aged 30-40 years. SIJ sclerosis and fatty marrow deposition were most common in women. SIJ bone marrow oedema, sclerosis and erosions were most frequent in women indicating pregnancy-related LBP.Conclusion: The high prevalence of SIJ MRI findings associated with age, gender, and pregnancy-related LBP need further investigation of their clinical importance in LBP patients.Key Points: • The location of vertebral endplate signal changes supports a mechanical aetiology. • Several sacroiliac joint findings were associated with female gender and pregnancy-related back pain. • Sacroiliac joint bone marrow oedema was frequent and age-associated, indicating a possible degenerative aetiology. • More knowledge of the clinical importance of sacroiliac joint MRI findings is needed. [ABSTRACT FROM AUTHOR]

“Spinal instrumentation without fusion” techniques, which do not interfere with spinal growth, have been used extensively in the treatment of progressive spinal scoliosis in very young children. Due to subperiosteal exposure, the process of spinal instrumentation may induce spontaneous bony fusion. Instrumentation and surgical techniques have been modified in order to prevent spontaneous posterior fusion from occurring in children. An absorbable ADCON-L gel has been shown to inhibit scar and epidural adhesions following spinal surgeries. However, little is known about its influence on spinal fusion. In the present study, a single-level intertransverse arthrodesis at L4-5 on both sides was performed on each of nine pigs. Each side was randomly designed to receive autogenous bone graft with or without ADCON-L gel. The animals were followed for 10 weeks postoperatively. A fusion rate of 78% (7/9) was obtained in the autograft treatment by plain X-ray and CT evaluation, while the autograft/ADCON-L treatment yielded a 0% (0/9) fusion rate (p=0.001). Histomorphometric evaluation revealed that the addition of ADCON-L gel to bone graft decreased bone and bone marrow formation and significantly increased fibrous tissue formation. No statistical difference between the two treatments was found in cartilage, bone surface density, osteoid surfaces or osteoclast-covered surfaces in any zone. We conclude that ADCON-L gel mixed into autogenous bone graft can delay or decrease bone formation at spinal arthrodesis sites, thus influencing the extent of spinal fusion. This accords with our hypothesis that the use of ADCON-L gel can prevent not only the occurrence of spontaneous fusion in very young scoliosis patients after instrumentation without fusion, but also re-ossification of a decompressed spinal canal. [ABSTRACT FROM AUTHOR]

Due to the increasing number of spinal procedures performed worldwide, adjacent degenerative disease has become a new focus area. Whether adjacent segment disease is a matter of normal degenerative development in the disc over time or a result of increased stiffness and stress due to the fusion is still debated. Nowadays TLIF is the most widely used interbody fusion method. The use of interbody fusion has been claimed to reduce degenerative changes in the spared free disc over time due to better sagittal balance and restoration of the lost lumbar lordosis. To compare degenerative changes on MRI between PLF and TLIF 10 years postsurgery in an RCT cohort. Randomized clinical trial (RCT). Long-term follow-up. Out of a primary cohort of 100 patients included in a prospective RCT between inter-body fusion and instrumented posterolateral fusion, 79 were available for follow-up 10 years after inclusion in the RCT. Patients were seen in the outpatient clinic and offered MRI at long-term follow-up. Changes over time in Modic, Pfirmann, Schizas, and Fardon and Milette. All MRI were classified according to degree of Modic changes, Pfirmann classification, Schizas classification, and Fardon and Milette classification in order to show the degree of degeneration of the discs above and below the fusion. The grading was done by independent observers without any contact to the patient. In patients who underwent secondary surgery, the immediately previous MRI was used and the degenerative changes measured according to the above-mentioned classifications. The groups were equal regarding sex, age, diagnosis and number operated levels. The follow-up was 9.6 years. The Modic change found at the first upper level was none in (85%/68%), mostly grade 2 (12%TLIF/26%PLF). There was no significant difference between the two groups p=0.274. Nearly all patients did not show any sign of treatment needs regarding spinal stenosis according to Schizas classification 92%/92%; only 8/8% had type C and D at the first proximal level 9.6 years after surgery. Interestingly, the amount of spinal stenosis grade C and D was higher at second proximal disc. No difference between groups could be detected p = 0.930 & p = 0.500. The Pfirmann grading at the first proximal level did not show any difference between groups p = 0.952. In an RCT, the use of interbody fusion (TLIF) does not reduce the degenerative changes in the first proximal disc next to the fusion in a long-term observational study period in comparison to a normal posterolateral instrumented fusion (PLF). Thus, degenerative changes in the first proximal level are not influenced by intercorporal devices. The incidence of spinal stenosis grade C and D, 10 years after lumbar fusion surgery are 8% at first proximal disc, 13 % at second proximal disc and 8% at first distal level. This abstract does not discuss or include any applicable devices or drugs. [ABSTRACT FROM AUTHOR]

This article presents the recommendations of the European Society of Musculoskeletal Radiology Arthritis Subcommittee regarding the standards of the use of MRI in the diagnosis of musculoskeletal rheumatic diseases. The recommendations discuss (1) the role of MRI in current classification criteria of musculoskeletal rheumatic diseases (including early diagnosis of inflammation, disease follow-up, and identification of disease complications); (2) the impact of MRI on the diagnosis of axial and peripheral spondyloarthritis, rheumatoid arthritis, and juvenile spondyloarthritis; (3) MRI protocols for the axial and peripheral joints; (4) MRI interpretation and reporting for axial and peripheral joints; and finally, (5) methods for assessing MR images including quantitative, semiquantitative, and dynamic contrast-enhanced MRI studies. [ABSTRACT FROM AUTHOR]

Older people are at increased risk of non-union after spinal fusion, but little is known about the factors determining the quality of the fusion mass in this patient group. The aim of this study was to investigate fusion mass bone quality after uninstrumented spinal fusion and to evaluate if it could be improved by additional direct current (DC) electrical stimulation. A multicenter RCT compared 40 and 100 μA DC stimulation with a control group of uninstrumented posterolateral fusion in patients older than 60 years. This report comprised 80 patients who underwent DEXA scanning at the 1 year follow-up. The study population consisted of 29 men with a mean age of 72 years (range 62-85) and 51 women with a mean age of 72 years (range 61-84). All patients underwent DEXA scanning of their fusion mass. Fusion rate was assessed at the 2 year follow-up using thin slice CT scanning. DC electrical stimulation did not improve fusion mass bone quality. Smokers had lower fusion mass BMD (0.447 g/cm) compared to non-smokers (0.517 g/cm) ( P = 0.086). Women had lower fusion mass BMD (0.460 g/cm) compared to men (0.552 g/cm) ( P = 0.057). Using linear regression, fusion mass bone quality, measured as BMD, was significantly influenced by gender, age of the patient, bone density of the remaining part of the lumbar spine, amount of bone graft applied and smoking. Fusion rates in this cohort was 34% in the control group and 33 and 43% in the 40 and 100 μA groups, respectively (not significant). Patients classified as fused after 2 years had significant higher fusion mass BMD at 1 year (0.592 vs. 0.466 g/cm, P = 0.0001). Fusion mass bone quality in older patients depends on several factors. Special attention should be given to women with manifest or borderline osteoporosis. Furthermore, bone graft materials with inductive potential might be considered for this patient population. [ABSTRACT FROM AUTHOR]

Platelet-rich plasma (PRP) is an autogenous source of growth factor and has been shown to enhance bone healing both in clinical and experimental studies. PRP in combination with porous hydroxyapatite has been shown to increase the bone ingrowth in a bone chamber rat model. The present study investigated whether the combination of beta tricalcium phosphate (β-TCP) and PRP may enhance spinal fusion in a controlled animal study. Ten Danish Landrace pigs were used as a spinal fusion model. Immediately prior to the surgery, 55 ml blood was collected from each pig for processing PRP. Three-level anterior lumbar interbody fusion was performed with carbon fiber cages and staples on each pig. Autogenous bone graft, β-TCP, and β-TCP loaded with PRP were randomly assigned to each level. Pigs were killed at the end of the third month. Fusion was evaluated by radiographs, CT scanning, and histomorphometric analysis. All ten pigs survived the surgery. Platelet concentration increased 4.4-fold after processing. Radiograph examination showed 70% (7/10) fusion rate in the autograft level. All the levels with β-TCP+PRP showed partial fusion, while β-TCP alone levels had six partial fusions and four non-fusions (P=0.08). CT evaluation of fusion rate demonstrated fusion in 50% (5/10) of the autograft levels. Only partial fusion was seen at β-TCP levels and β-TCP+PRP levels. Histomorphometric evaluation found no difference between β-TCP and β-TCP+PRP levels on new bone volume, remaining β-TCP particles, and bone marrow and fibrous tissue volume, while the same parameters differ significantly when compared with autogenous bone graft levels. We concluded from our results in pigs that the PRP of the concentration we used did not improve the bone-forming capacity of β-TCP biomaterial in anterior spine fusion. Both β-TCP and β-TCP+PRP had poorer radiological and histological outcomes than that of autograft after 3 months. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the treatment response in lateral epicondylitis (tennis elbow) by MRI. Magnetic resonance imaging was obtained in 30 patients with clinical symptoms of lateral epicondylitis of the elbow using T1-, T2- and T2-weighted fat-saturated (FS) sequences. The patients were randomised to either i.m. corticosteroid injection ( n=16) or immobilisation in a wrist splint ( n=14). Magnetic resonance imaging of the elbow was performed on a 1.5-T MR system at baseline and after 6 weeks. The extensor carpi radialis (ECRB) tendon, the radial collateral ligament, lateral humerus epicondyle at tendon insertion site, joint fluid and signal intensity changes within brachio-radialis and anconeus muscles were evaluated on the MR unit's workstation before and after 6 weeks of treatment. The MRI was performed once in 22 healthy controls for comparison and all images evaluated by an investigator blinded to the clinical status of the subjects. The MR images showed thickening with separation of the ECRB tendon from the radial collateral ligament and abnormal signal change in 25 of the 30 patients on the T1-weighted sequences at inclusion. The signal intensity of the ECRB tendon was increased in 24 of the 30 patients with lateral epicondylitis of the elbow on the T2-weighted FS sequences. In the patients there were no associations between pathologically signal intensity within the ECRB tendon on T1- and T2-weighted sequences and the degree of self-reported pain (Dumbells test) at inclusion. In general, the MRI changes persisted in the patients at follow-up after 6 weeks despite clinical remission. The increased signal intensity within the extensor tendon is indicative of lateral epicondylitis humeri. The changes in signal intensity and morphology of ECRB tendon seem to be chronic and may persist despite clinical improvement. [ABSTRACT FROM AUTHOR]

Objective: To present results of optimising scoliosis examination by changing from a conventional film/grid (F/G) to air-gap technique using computed radiography (CR), and to evaluate different methods for estimating effective radiation doses.Materials and Methods: Forty-nine children and adolescents were examined with an F/G technique, and 21 with air-gap and CR techniques. Entrance surface doses (ESD) were determined with lithium fluoride thermoluminescence dosimeters. For all patients, the effective radiation doses were determined using a hermaphrodite PCXMC computer program. For all F/G radiographs, the effective doses were also determined according to the NRPB-R279 report, and for 22 children (>9 years and/or >40 kg) also with the ODS-60 program, which allows separate gender calculations. Accumulated doses for 37 children examined more than once with F/G examinations were assessed.Results: For F/G techniques, the ESDs for both frontal and lateral views varied with age and were significantly correlated to the patients' thickness. The calculated effective doses using the PCXMC program and the NRPB-R279 did not differ significantly for all frontal and lateral radiographs, respectively, but ODS-60 gave significantly higher values in female subjects. With air-gap and CR techniques, the mean effective doses were reduced by a factor over 10. The mean accumulated effective dose for 37 children with a mean of seven F/G examinations was 6.1 mSv, implying a risk of death of about 1:2,000 for boys and at least 1:1,000 for girls.Conclusions: Paediatric scoliosis radiography should be considered a specialised procedure, which has to be optimised using a non-grid technique. [ABSTRACT FROM AUTHOR]

Background: Bone marrow lesions (BMLs) in knee osteoarthritis (OA) have been assessed histopathologically and by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI); however, a direct comparison of the results has not been reported., Purpose: To evaluate and compare the findings by DCE-MRI and histopathology of subchondral BMLs in knee OA., Material and Methods: In total, 19 patients with medial tibiofemoral knee OA undergoing total knee arthroplasty were analyzed. Preoperative MRI, including a DCE sequence, was performed, and bone biopsies were obtained from the resected specimens corresponding to BML areas. The contrast enhancement by DCE-MRI was analyzed using semi-quantitative (area under the curve [AUC]), peak enhancement [PE]), and quantitative (Ktrans, Kep) methods. Enhancement in the medial OA compartment was compared with similar areas in a normal lateral compartment, and the DCE characteristics of BMLs were correlated with semi-quantitatively graded histopathological features., Results: AUC and PE were significantly higher in medial tibial and femoral BMLs compared with the values in the lateral condyles; Ktrans and Kep were only significantly higher in the tibial plateau. In the tibia, AUC and PE were significantly correlated with the grade of vascular proliferation, and PE also with the degree of marrow fibrosis. There was no significant correlation between AUC/PE and histopathological findings in the femur and no correlation between quantitative DCE parameters and histopathological findings., Conclusion: BML characteristics by semi-quantitative DCE in the form of AUC and PE may be used as parameters for the degree of histopathological vascularization in the bone marrow whereas quantitative DCE data were less conclusive., Competing Interests: Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Objective: The tibial tuberosity-trochlear groove (TTTG) distance varies with the position of the knee in the MR or CT scanner. We present and assess a simple method for adjustment of adduction or abduction of the knee., Materials and Methods: MRI of the knee encompassing a three-dimensional (3D) sagittal sequence including ≥ 8 cm of the proximal tibia was analyzed (29 females, 17 males; median age 45 years). Using 3D visualization software, the central longitudinal axis of the proximal tibia (TA) was constructed, and the TTTG distance was measured before and after alignment of the TA. Observer reliability was assessed with inter- and intra-class correlation coefficient (ICC) and Bland-Altman plots., Results: Adduction of the knee occurred in 26 examinations, mean 2.7° (range 0.0° to 9.4°), and abduction in 20 examinations, mean 2.6° (range 0.0° to 7.2°). Following adjustment, the mean TTTG distance increased 2.4 mm (range 0.0 to 6.7 mm) in the knees positioned in adduction and decreased 2.3 mm when in abduction (range 0.0 to 5.5 mm). The correlation coefficient (r 2 ) between the deviation in adduction and abduction and the difference between TTTG unadjusted and adjusted was r 2  = 0.96. ICCs were excellent, but limits of agreement were close to ± 3 mm., Conclusion: Measurement of the TTTG distance by MRI is influenced by a systematic technique-dependent error caused by knee positioning in adduction or abduction. We suggest a simple method for adjusting the positioning.

Objective: To introduce and evaluate computed tomography (CT)-guided transarticular needle biopsy of the cartilaginous sacroiliac joint (SIJ) and to assess the biopsy results microscopically., Materials and Methods: The new CT-guided transarticular biopsy of the SIJ was performed in a young corpse and ten patients, two males and eight females aged 18-81 years. All patients had abnormal findings by magnetic resonance imaging (MRI) of the SIJs, including bone marrow edema, related to different types of joint disorders. The biopsies were focused on areas with bone marrow edema. The quality of the specimens obtained, using two different types of biopsy needles, was assessed microscopically., Results: Biopsies containing cartilage, subchondral plate, and bone marrow from the iliac and sacral sides were obtained from the corpse and three patients and from the iliac bone only in two patients. In three patients, the biopsy needles could not penetrate the bone marrow to the joint facet due to pronounced subchondral sclerosis, but adequate marrow biopsies were obtained. Two biopsies were inadequate, one due to technical problems and one was crushed during preparation. Histological assessment of eight adequate specimens revealed inflammatory bone marrow changes, except in two specimens from females with pronounced sclerosis conforming to osteitis condensans ilii., Conclusions: Transarticular SIJ biopsies are obtainable and can be directed towards areas with MRI abnormalities. They can be used to confirm inflammatory changes histologically. With the biopsy needles used, severe bone marrow sclerosis may hinder penetration to the cartilage, but bone marrow specimens can be obtained.

In this review about perfusion magnetic resonance imaging (pMRI), we consider it to give detailed insight into the distribution of the infarction in the femoral head in the early phase of Perthes disease. The degree of head involvement is closely related to the long-term prognosis, and as early surgical treatment of children with severe head involvement may be beneficial, pMRI is suggested as an examination in older children with early stages of Perthes disease. The use of gadolinium as contrast medium in otherwise healthy children seems safe, but long-term effects are unknown.

Background Diagnosis and treatment of patellofemoral disorders including osteoarthritis are currently often based on imaging and clinical assessment with patients in the supine position. Purpose To evaluate differences in patellar position in the trochlear groove and to assess the detection of medial and lateral patellofemoral (PF) osteoarthritis (OA) on axial radiographs in supine and standing positions, respectively. Material and Methods Thirty-five women and 23 men (mean age, 56 years; age range, 18-87 years) referred for routine radiographic examinations of the knees were included. Axial radiographs of the PF joint in both supine non-weight-bearing and standing weight-bearing position in 30° knee flexion were obtained of 111 knees. Measurements performed on the radiographs: patellar tilt, patellar displacement, joint space width, and grade of OA according to Ahlbäck. Results From supine to standing position the patella moved medially and medial joint space width and lateral patellar tilt angle decreased ( P < 0.0001 for the three measured parameters). In the standing position, medial PF OA was observed in 19 knees compared to three knees in the supine position. Fourteen knees had lateral PF OA with almost unchanged grade of OA irrespective of position. Conclusion In weight-bearing positions, the patella is positioned medially in the trochlear groove compared to supine non-weight-bearing positions. Therefore, this study suggests that the common occurrence of medial PF OA can generally not be detected on axial radiographs in supine non-weight-bearing positions and confirms the importance of imaging the PF joint in standing weight-bearing positions.

The anatomy of joints provides an important basis for understanding the nature and imaging of pathologic lesions and their imaging appearance. This applies especially to the sacroiliac (SI) joints, which play a major role in the diagnosis of spondyloarthritis. They are composed of two different joint portions, a cartilage-covered portion ventrally and a ligamentous portion dorsally, and thus rather complex anatomically. Knowledge of anatomy and the corresponding normal imaging findings are important in the imaging diagnosis of sacroiliitis, especially by MR imaging. A certain distinction between the two joint portions by MR imaging is only obtainable by axial slice orientation. Together with a perpendicular coronal slice orientation, it provides adequate anatomical information and thereby a possibility for detecting the anatomical site of disease-specific characteristics and normal variants simulating disease. This overview describes current knowledge about the normal macroscopic and microscopic anatomy of the SI joints., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

Objective: To examine the long-term efficacy and safety of five intra-articular injections with hyaluronan in knee osteoarthritis., Methods: A multicentre, randomised, placebo-controlled double-blind study of 337 patients fulfilling the American College of Rheumatology (ACR) criteria for knee osteoarthritis (clinical and laboratory) and with a Lequesne algofunctional index score (LFI) of 10 or greater. Patients received a hyaluronan product (sodium hyaluronate; Hyalgan) (n=167) or saline (n=170) intra-articularly weekly for 5 weeks and were followed up to 1 year. Time to recurrence was the primary efficacy parameter. LFI, pain on walking 50 m based on visual analogue scale (VAS pain 50 m), paracetamol consumption, patients' global assessment, Nottingham health profile, joint effusion and number of responders were secondary efficacy parameters. The efficacy parameters were analysed by intention to treat (ITT) and per protocol (PP). All adverse events (AE) were recorded as safety parameters., Results: Time to recurrence showed no significant treatment effect (ITT analysis, p=0.26). Change from baseline in LFI and VAS pain 50 m for the ITT population showed no treatment effect. Paracetamol consumption, patients' global assessment, responder rates and AE displayed no significant difference between treatment groups, analysed by both ITT and PP. Treatment compliance was 95% in the hyaluronan group and 99% in the placebo group. No safety problems were registered., Conclusion: In patients fulfilling the ACR criteria for osteoarthritis of the knee with moderate to severe disease activity (LFI > or = 10), five intra-articular injections of hyaluronan did not improve pain, function, paracetamol consumption or other efficacy parameters 3, 6, 9 and 12 months after the treatment.