Pain reduction after lumbar epidural injections using particulate versus non-particulate steroids: intensity of the baseline pain matters.

OBJECTIVES: To compare pain relief after CT-guided lumbar epidural steroid injections (ESI) using particulate (triamcinolone) and non-particulate (dexamethasone) steroids, and to explore factors affecting the effectiveness of both steroid types. METHODS: This retrospective observational study included 806 patients with lumbar radiculopathy and corresponding MRI or CT abnormalities of the lumbar spine, who were matched using the propensity score method, yielding two cohorts of 209 patients each. Pain intensity was evaluated prior to the procedure using a pain numerical rating scale (NRS) with range 0-10. Reevaluation took place 1 day and 4 weeks post-injection. Logistic regression analysis and cubic splines applied to generalized additive models were implemented to assess the differences in pain reduction after ESI in the analyzed patient groups. RESULTS: Four weeks post-injection, the overall chance of ≥ 50% pain reduction was lower in the dexamethasone group than that in the triamcinolone group (odds ratio [OR] = 0.55; p < 0.012). In the dexamethasone cohort, the intensity of baseline pain and the presence of a herniated intervertebral disc in the infiltrated segment were both significant and independent predictors of ≥ 50% pain relief. Patients with baseline NRS score ≥ 7 points had markedly less chance of ≥ 50% pain relief than patients with NRS score < 7 (OR = 0.53; p < 0.032), whereas disc herniation increased the chances more than twofold (OR = 2.29; p < 0.044). There was no significant correlation between the effectiveness of triamcinolone and any analyzed concomitant variables. CONCLUSIONS: Triamcinolone was superior for lumbar radiculopathy of severe intensity. For mild to moderate pain, no benefit of using triamcinolone over dexamethasone was found. The effectiveness of dexamethasone was lower for stenotic spinal lesions than for disc herniation. KEY POINTS: • Triamcinolone is superior to dexamethasone for epidural treatment of severe lumbar radiculopathy. • For mild to moderate pain, dexamethasone could be equally effective. • Dexamethasone reduces pain caused by disc herniation much better than it does to pain caused by fixed stenotic spinal lesions.

Symptomatic, Magnetic Resonance Imaging-Confirmed Cervical Disk Herniation Patients: A Comparative-Effectiveness Prospective Observational Study of 2 Age- and Sex-Matched Cohorts Treated With Either Imaging-Guided Indirect Cervical Nerve Root Injections or Spinal Manipulative Therapy.

OBJECTIVE: The purpose of this study was to compare the outcomes of overall improvement, pain reduction, and treatment costs in matched patients with symptomatic, magnetic resonance imaging-confirmed cervical disk herniations treated with either spinal manipulative therapy (SMT) or imaging-guided cervical nerve root injection blocks (CNRI). METHODS: This prospective cohort comparative-effectiveness study included 104 patients with magnetic resonance imaging-confirmed symptomatic cervical disk herniation. Fifty-two patients treated with CNRI were age and sex matched with 52 patients treated with SMT. Baseline numerical rating scale (NRS) pain data were collected. Three months after treatment, NRS pain levels were recorded and overall "improvement" was assessed using the Patient Global Impression of Change scale. Only responses "much better" or "better" were considered "improved." The proportion of patients "improved" was calculated for each treatment method and compared using the χ(2) test. The NRS and NRS change scores for the 2 groups were compared at baseline and 3 months using the unpaired t test. Acute and subacute/chronic patients in the 2 groups were compared for "improvement" using the χ(2) test. RESULTS: "Improvement" was reported in 86.5% of SMT patients and 49.0% of CNRI patients (P = .0001). Significantly more CNRI patients were in the subacute/chronic category (77%) compared with SMT patients (46%). A significant difference between the proportion of subacute/chronic CNRI patients (37.5%) and SMT patients (78.3%) reporting "improvement" was noted (P = .002). CONCLUSION: Subacute/chronic patients treated with SMT were significantly more likely to report relevant "improvement" compared with CNRI patients. There was no difference in outcomes when comparing acute patients only.

MR imaging of healthy knees in varying degrees of flexion using a stretchable coil array provides comparable image quality compared to a standard knee coil array.

OBJECTIVE: Stretchable coils allow knee imaging at varying degrees of flexion. Purpose was to compare a new-developed stretchable 8-channel to a standard 8-channel knee coil array by means of quantitative and qualitative image analysis. MATERIAL AND METHODS: IRB approved prospective study. Knee MR imaging in 10 healthy volunteers was performed at 3T using a standard 8-channel and a new-developed stretchable 8-channel coil array at 0°, 45°, and 60° of flexion and at 0° (standard coil). Image parameters were identical. Signal-to-noise ratio (SNR) was determined by combining the images with separately acquired noise data on a pixel-by-pixel basis using MATLAB routines (Natick, MA, USA). Images were qualitatively analysed by two independent radiologists who graded the visibility of several anatomic structures from 1=not visible to 5=excellent. ANOVA, Wilcoxon and kappa statistics were used. RESULTS: Mean SNR±standarddeviation of bone was 54.7±10.4 and of muscle 28.0± 4.4 using the stretchable coil array and 54.6±8.2 and 33.4±4.5, respectively, using the standard knee coil array. No statistically significant SNR differences were found between both arrays (bone, p=0.960; muscle, p=0.132). SNR was not degraded at higher degrees of flexion. The qualitative image analysis did not reveal statistically significant differences between the stretchable and standard coil array with regard to the visibility of anatomic structures (p=0.026-1.000). Overall kappa was 0.714. CONCLUSION: Stretchable 8-channel coil arrays provide similar SNR and visibility of anatomic structures compared to standard 8-channel knee coil arrays. MR imaging with high SNR will now be possible in flexed knees.

Internal Derangements of Joints-Past, Present, and Future.

The past 50 years have transformed imaging of the joints. Whereas musculoskeletal imaging consisted predominantly of conventional radiography when Investigative Radiology was founded as a journal, the arrival of new imaging modalities, and above all, the introduction of magnetic resonance imaging, resulted in a paradigm shift: In addition to visualizing osseous structures, now the detailed depiction of soft tissue structures became part of routine clinical imaging and had a major impact on understanding pathophysiology and patient treatment. This article analyzes the patterns of innovation that were essential for the transformation of musculoskeletal radiology. Furthermore, state-of- the-art joint imaging is described through 9 key concepts, including both cutting-edge clinical applications as well as topics at the forefront of musculoskeletal research. Eventually, emerging trends are outlined that will likely shape musculoskeletal radiology in the next decades.

Are Modic changes related to outcomes in lumbar disc herniation patients treated with imaging-guided lumbar nerve root blocks?

OBJECTIVE: To compare outcomes after imaging-guided transforaminal lumbar nerve root blocks in MRI confirmed symptomatic disc herniation patients with and without Modic changes (MC). METHODS: Consecutive adult patients with MRI confirmed symptomatic lumbar disc herniations and an imaging-guided lumbar nerve root block injection who returned an outcomes questionnaire are included. Numerical rating scale (NRS) pain data was collected prior to injection and 20-30 min after injection. NRS and overall improvement were assessed using the patient's global impression of change (PGIC) scale at 1 day, 1 week and 1 month post injection. The proportion of patients with and without MC on MRI as well as Modic I and Modic II was calculated. These groups were compared for clinically relevant 'improvement' using the Chi-squared test. Baseline and follow-up NRS scores were compared for the groups using the unpaired t-test. RESULTS: 346 patients are included with MC present in 57%. A higher percentage of patients without MC reported 'improvement' and a higher percentage of patients with MC reported 'worsening' but this did not reach statistical significance. The numerical scores on the PGIC and NRS scales showed that patients with MC had significantly higher pain and worse overall improvement scores at 1 month (p=0.048 and p=0.03) and a significantly lower 1 month NRS change score (p=0.04). CONCLUSIONS: Patients with MRI confirmed symptomatic lumbar disc herniations and MC report significantly lower levels of pain reduction after a lumbar nerve root block compared to patients without MC.

The evolution of degenerative marrow (Modic) changes in the cervical spine in neck pain patients.

PURPOSE: To evaluate the natural course of end plate marrow (Modic) changes (MC) in the cervical spine on MRI scans of patients with neck pain. A few longitudinal studies have assessed the development of MC over time in the lumbar spine but only two recent studies evaluated MC in the cervical spine in asymptomatic volunteers and those with whiplash. Thus, this study now reports on the natural course of MC in the cervical spine in symptomatic patients. METHODS: From the cervical MRI scans of 426 neck pain patients (mean age 61.2 years), 64 patients had follow-up MRI studies. The prevalence and types of MC were retrospectively assessed on the follow-up scans and compared to the original MRI findings. RESULTS: With an average of 2.5 years between the two MRI scans, the prevalence of MC type 1 (MC1) noted at baseline (7.4% or 19 motion segments) slightly increased (8.2% or 21 segments) but the prevalence of MC2 (14.5% or 37 segments) increased considerably (22.3% or 57 segments). In addition, 14 new MC1 segments and 8 new MC2 segments were noted. Twelve segments with MC1 at baseline converted to MC2 at follow-up. No conversion from MC2 to MC1 or reverting to a normal image was observed. CONCLUSIONS: MC in the cervical spine are a dynamic phenomenon similar to the lumbar spine.

Lumbar nerve root injections: a prospective cohort outcomes study comparing age- and gender-matched patients who returned an outcomes-based postal questionnaire with patients who did not return the postal questionnaire.

OBJECTIVE: The purpose of this study is to investigate if relying on postal questionnaires returned by patients provides an accurate representation of reported outcomes from patients receiving imaging-guided lumbar nerve root injections (NRIs). MATERIALS AND METHODS: Patients who received imaging-guided transforaminal lumbar NRIs were given short questionnaires inquiring about pain level [numerical rating scale (NRS)] and overall improvement [Patient's Global Impression of Change (PGIC)]. Those who did not return the questionnaires (non-responders) were telephoned and asked about pain level and overall change in condition. Age and gender matching of responders and non-responders resulted in 97 patients in each group. The proportion of patients reporting clinically relevant "improvement" or "worsening" in each group was calculated and the Chi-square test was used to detect differences. NRS and PGIC scores for responders and non-responders were compared using Student's t test and the Mann-Whitney U test, respectively. RESULTS: A higher proportion of non-responders reported clinically relevant improvement (53.6 %) compared to responders (42.6 %) and responders reported significantly higher levels of worsening of condition (p = 0.01). Both responders and non-responders had significant (p ≤ 0.05) improvement on the 20-30-min and 1-month NRS scores compared to their pre-injection baseline scores. Non-responders had significantly higher baseline NRS scores but no significant difference at the 20-30-min and 1-month NRS scores compared to responders. CONCLUSIONS: Patients returning postal questionnaires reported less favorable outcomes compared to those who did not return their questionnaires.

Diffusion tensor imaging of the median nerve at 3.0 T using different MR scanners: agreement of FA and ADC measurements.

OBJECTIVE: To assess the agreement of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values of the median nerve on 3.0 T MR scanners from different vendors. MATERIALS AND METHODS: IRB approved study including 16 healthy volunteers (9 women; mean age 30.6 ± 5.3 years). Diffusion tensor imaging (DTI) of the dominant wrist was performed on three 3.0 T MR scanners (GE, Siemens, Philips) using similar imaging protocols and vendor-proprietary hard- and software. Intra-, inter-reader and inter-vendor agreements were assessed. RESULTS: ICCs for intra-/inter-reader agreements ranged from 0.843-0.970/0.846-0.956 for FA, and 0.840-0.940/0.726-0.929 for ADC, respectively. ANOVA analysis identified significant differences for FA/ADC measurements among vendors (p < 0.001/p < 0.01, respectively). Overall mean values for FA were 0.63 (SD ± 0.1) and 0.999 × 10(-3)mm(2)/s (SD ± 0.134 × 10(-3)) for ADC. A significant negative measurement bias was found for FA values from the GE scanner (-0.05 and -0.07) and for ADC values from the Siemens scanner (-0.053 and -0.063 × 10(-3)mm(2)/s) as compared to the remainder vendors CONCLUSION: FA and ADC values of the median nerve obtained on different 3.0 T MR scanners differ significantly, but are in comparison to the standard deviation of absolute values small enough to not have an impact on larger group studies or when substantial diffusion changes can be expected. However, caution is warranted in an individual patient when interpreting diffusion values from different scanner acquisitions.

Magnetic resonance imaging frequently changes classification of acute traumatic thoracolumbar spine injuries.

OBJECTIVE: To evaluate the influence of additional (MRI) compared with computed tomography (CT) alone for the classification of traumatic spinal injuries using the Arbeitsgemeinshaft für Osteosynthesefragen (AO) system and the Thoraco-Lumbar Injury Classification and Severity (TLICS) scale. MATERIALS AND METHODS: Images from 100 consecutive patients with at least one fracture on CT were evaluated retrospectively by three radiologists with regard to the AO and TLICS classification systems in 2 steps. First, all images from the initial CT examination were analyzed. Second, 6 weeks later, CT and MR images were analyzed together. Descriptive statistics and Wilcoxon tests were performed to identify changes in the number of fractures and ligamentous lesions detected and their corresponding classification. RESULTS: CT and MRI together revealed a total of 196 fractures (CT alone 162 fractures). The AO classification changed in 31 %, the TLICS classification changed in 33 % of the patients compared with CT alone. Based on CT and MRI together, the TLICS value changed from values <5 (indication for conservative therapy) to values ≥ 5 (indication for surgical therapy) in 24 %. CONCLUSION: MRI of patients with thoracolumbar spinal trauma considerably improved the detection of fractures and soft tissue injuries compared with CT alone and significantly changed the overall trauma classification.

Gender differences in pain levels before and after treatment: a prospective outcomes study on 3,900 Swiss patients with musculoskeletal complaints.

BACKGROUND: Current studies comparing musculoskeletal pain levels between the genders focus on a single point in time rather than measuring change over time. The purpose of this study is to compare pain levels between males and females before and after treatment. METHODS: Eleven different patient cohorts (3,900 patients) included in two prospective outcome databases collected pain data at baseline and 1 month after treatment. Treatments were either imaging-guided therapeutic injections or chiropractic therapy. The Mann-Whitney U test was used to calculate differences in numerical rating scale (NRS) median scores between the genders for both time points in all 11 cohorts. RESULTS: Females reported significantly higher baseline pain scores at 4 of the 11 sites evaluated (glenohumeral (p = 0.015), subacromial (p = 0.002), knee (p = 0.023) injections sites and chiropractic low back pain (LBP) patients (p = 0.041)). However, at 1 month after treatment there were no significant gender differences in pain scores at any of the extremity sites. Only the chiropractic LBP patients continued to show higher pain levels in females at 1 month. CONCLUSIONS: In these 11 musculoskeletal sites evaluated before and after treatment, only 3 extremity sites and the chiropractic LBP patients showed significantly higher baseline pain levels in females. At 1 month after treatment only the LBP patients had significant gender differences in pain levels. Gender evaluation of change in pain over time is likely to be more clinically important than an isolated pain measurement for certain anatomical sites.

Computer assisted reconstruction of complex proximal humerus fractures for preoperative planning.

Operative treatment of displaced fractures of the proximal humerus is among the most difficult problems in orthopedic shoulder surgery. An accurate preoperative assessment of fragment displacement is crucial for a successful joint restoration. We present a computer assisted approach to precisely quantify these displacements. The bone is virtually reconstructed by multi-fragment alignment. In case of largely displaced pieces, a reconstruction template based on the contralateral humerus is incorporated in the algorithm to determine the optimal assembly. Cadaver experiments were carried out to evaluate our approach. All cases could be successfully reconstructed with little user interaction, and only requiring a few minutes of processing time. On average, the reassembled bone geometries resulted in a translational displacement error of 1.3±0.4 mm and a rotational error of 3.4±2.2°, respectively.

Are there cervical spine findings at MR imaging that are specific to acute symptomatic whiplash injury? A prospective controlled study with four experienced blinded readers.

PURPOSE: To compare the magnetic resonance (MR) imaging findings in patients with acute whiplash injury with those in matched control subjects. MATERIALS AND METHODS: In a prospective multicenter controlled study, from 2005 to 2008, 100 consecutive patients underwent 1.5-T MR imaging examinations of the cervical spine within 48 hours after a motor vehicle accident. Findings in these patients were compared in a blinded fashion with those in 100 age- and sex-matched healthy control subjects. Four blinded independent readers assessed the presence of occult vertebral body and facet fractures, vertebral body and facet contusions, intervertebral disk herniations, ligamentum nuchae strains, ligamentum nuchae tears, muscle strains or tears, and perimuscular fluid. Accuracy (as compared with clinical findings) and interobserver reliability were calculated. RESULTS: Accuracy of MR imaging and interreader reliability were generally poor (sensitivity, 0.328; specificity, 0.728; positive and negative likelihood ratios, 1.283 and 1.084, respectively). MR imaging findings significantly associated with whiplash injuries were occult fracture (P<.01), bone marrow contusion of the vertebral body (P=.01), muscle strain (P<.01) or tear (P<.01), and the presence of perimuscular fluid (P<.01). While 10 findings thought to be specific for whiplash trauma were significantly (P<.01) more frequent in patients (507 observations), they were also regularly found in healthy control subjects (237 observations). There were no serious occult injuries that required immediate therapy. CONCLUSION: MR imaging at 1.5 T reveals only limited evidence of specific changes to the cervical spine and the surrounding tissues in patients with acute symptomatic whiplash injury compared with healthy control subjects.

Dynamic imaging and function of partial supraspinatus tendon tears.

PURPOSE: It was the purpose of this study to identify and document normal and abnormal supraspinatus tendon function in vivo using real-time ultrasound. METHODS: We defined 4 groups of 20 individuals each: partial tear (group 1), full-thickness tear (group 2), successfully repaired tear (group 3), and healthy asymptomatic controls (group 4). Except for group 4, all patients underwent magnetic resonance arthrography to confirm the diagnosis. All underwent ultrasound imaging of the supraspinatus tendon with the adducted arm at rest and under maximal isometric abduction. Tendon deformation was dynamically assessed and measured with tendon thickness changes at 0.5, 1, 1.5, and 2 cm from the tendon insertion. The clinical assessment consisted of absolute and relative Constant score, subjective shoulder value, and strength measurements. RESULTS: Without muscle contraction, the tendons of the 4 groups were not of significantly different thickness, with the least variation at 1.5 cm from the insertion site. On contraction, the normal tendon thickness significantly increased at a distance of 2 cm, whereas it did not for the full-thickness and partial supraspinatus tears. Thus contraction of the muscle resulted in measurable deformation of the tendon. CONCLUSIONS: Partially torn supraspinatus tendons can be functionally incompetent, leading to a biomechanical deformation of the musculotendinous unit that is not different from that of a unit with a full-thickness tendon tear. The dynamic sonographic finding of a successful repair of a supraspinatus tendon is similar to that of a normal tendon, even though the previously injured muscle appears unable to generate the same strength as a normal muscle. LEVEL OF EVIDENCE: Level III, case-control study.

Synovitis maps for the assessment of inflammatory diseases of the hand.

OBJECTIVES: To compare accuracy and review times of FLASH-MRI-derived synovitis maps (SM) with conventional MR images (cMRI) in the assessment of articular synovitis and tenosynovitis of the hand. METHODS: 80 hands in 40 patients (mean age, 48 years; range, 15-72 years) were assessed for synovitis on cMRI and SM by two readers independently. Reporting times and diagnostic confidence (scale: 1 = least, 5 = most confident) were measured. Results from an assessment of a panel of senior musculoskeletal radiologists served as the standard of reference. RESULTS: Sensitivity and specificity for the detection of articular synovitis were 0.91/1.00 (R1) and 1.00/0.67 (R2) on cMRI and 0.87/0.75 (R1) and 0.91/0.45 (R2) on SM and for the detection of tenosynovitis 0.95/0.63 (R1) and 0.67/0.79 (R2) on cMRI and 0.67/0.89 (R1) and 0.38/1.00 (R2) on SM. Mean review times (cMRI/SM, sec) were 142/37 (R1) and 167/25 (R2). Mean diagnostic confidence (cMRI/SM) was 3.7/3.4 (R1) and 3.2/3.5 (R2) for articular synovitis and 4.0/4.0 (R1), 3.3/3.7 (R2) for tenosynovitis. CONCLUSION: Synovitis maps provide a comparable diagnostic accuracy to conventional MR images in the assessment of articular synovitis and tenosynovitis of the hand. Because of short review times, synovitis maps provide a fast overview of locations with synovial enhancement.

LumbSten: the lumbar spinal stenosis outcome study.

BACKGROUND: Lumbar spinal stenosis is the most frequent reason for spinal surgery in elderly people. For patients with moderate or severe symptoms different conservative and surgical treatment modalities are recommended, but knowledge about the effectiveness, in particular of the conservative treatments, is scarce. There is some evidence that surgery improves outcome in about two thirds of the patients. The aims of this study are to derive and validate a prognostic prediction aid to estimate the probability of clinically relevant improvement after surgery and to gain more knowledge about the future course of patients treated by conservative treatment modalities. METHODS/DESIGN: This is a prospective, multi-centre cohort study within four hospitals of Zurich, Switzerland. We will enroll patients with neurogenic claudication and lumbar spinal stenosis verified by Computer Tomography or Magnetic Resonance Imaging. Participating in the study will have no influence on treatment modality. Clinical data, including relevant prognostic data, will be collected at baseline and the Swiss Spinal Stenosis Questionnaire will be used to quantify severity of symptoms, physical function characteristics, and patient's satisfaction after treatment (primary outcome). Data on outcome will be collected 6 weeks, and 6, 12, 24 and 36 months after inclusion in the study. Applying multivariable statistical methods, a prediction rule to estimate the course after surgery will be derived. DISCUSSION: The ultimate goal of the study is to facilitate optimal, knowledge based and individualized treatment recommendations for patients with symptomatic lumbar spinal stenosis.

Degeneration of the long biceps tendon: comparison of MRI with gross anatomy and histology.

OBJECTIVE: The objective of our study was to relate alterations in biceps tendon diameter and signal on MR images to gross anatomy and histology. MATERIALS AND METHODS: T1-weighted, T2-weighted fat-saturated, and proton density-weighted fat-saturated spin-echo sequences were acquired in 15 cadaveric shoulders. Biceps tendon diameter (normal, flattened, thickened, and partially or completely torn) and signal intensity (compared with bone, fat, muscle, and joint fluid) were graded by two readers independently and in a blinded fashion. The distance of tendon abnormalities from the attachment at the glenoid were noted in millimeters. MRI findings were related to gross anatomic and histologic findings. RESULTS: On the basis of gross anatomy, there were six normal, five flattened, two thickened, and two partially torn tendons. Reader 1 graded nine diameter changes correctly, missed two, and incorrectly graded four. The corresponding values for reader 2 were seven, one, and five, respectively, with kappa = 0.75. Histology showed mucoid degeneration (n = 13), lipoid degeneration (n = 7), and fatty infiltration (n = 6). At least one type of abnormality was found in each single tendon. Mucoid degeneration was hyperintense compared with fatty infiltration on T2-weighted fat-saturated images and hyperintense compared with magic-angle artifacts on proton density-weighted fat-saturated images. MRI-based localization of degeneration agreed well with histologic findings. CONCLUSION: Diameter changes are specific but not sensitive in diagnosing tendinopathy of the biceps tendon. Increased tendon signal is most typical for mucoid degeneration but should be used with care as a sign of tendon degeneration.

Upregulation of alpha-skeletal muscle actin and myosin heavy polypeptide gene products in degenerating rotator cuff muscles.

Impaired function of shoulder muscles, resulting from rotator cuff tears, is associated with abnormal deposition of fat in muscle tissue, but corresponding cellular and molecular mechanisms, likely reflected by altered gene expression profiles, are largely unknown. Here, an analysis of muscle gene expression was carried out by semiquantitative RT-PCR in total RNA extracts of supraspinatus biopsies collected from 60 patients prior to shoulder surgery. A significant increase of alpha-skeletal muscle actin (p = 0.0115) and of myosin heavy polypeptide 1 (p = 0.0147) gene transcripts was observed in parallel with progressive fat deposition in the muscle, assessed on parasagittal T1-weighted turbo-spin-echo magnetic resonance images according to Goutallier. Upregulation of alpha-skeletal muscle actin and of myosin heavy polypeptide-1 has been reported to be associated with increased muscle tissue metabolism and oxidative stress. The findings of the present study, therefore, challenge the hypothesis that increased fat deposition in rotator cuff muscle after injury reflects muscle degeneration.

The clinical consequences of flexion gap asymmetry in total knee arthroplasty.

This study was carried out to compare femoral component rotation of 18 knees from 18 patients who suffered from lateral flexion instability after total knee arthroplasty (Western Ontario and McMaster University Osteoarthritis [WOMAC], 6.4 points; International Knee Society [IKS] score, 119 points) with 10 asymptomatic controls (WOMAC, 0.1 points; IKS score, 182 points) after total knee arthroplasty. The symptomatic patients showed increased lateral joint laxity as determined by fluoroscopic stress radiography. Femoral component rotation was determined by computed tomography scans. The femoral component rotation was more internally rotated in symptomatic patients (5.5 degrees ) than in controls (1.0 degrees ) (P = .04). Varus laxity in flexion was higher in symptomatic patients (11.0 degrees ) than in controls (7.0 degrees ) (P < .001). Increased lateral flexion laxity is associated with increased internal femoral component rotation and a less favorable clinical outcome.

Measuring orthopedic implant wear on standard radiographs with a precision in the 10 microm-range.

The aim of this study has been to explore and verify whether the use of a previously designed Analysis-by-Synthesis algorithm is capable to precisely measuring implant wear. The abrasion of polyethylene particles is seen as the main reason for the loosening of prosthetic components in the hip. It lies in the sub-millimeter range, and precision is a crucial point in wear measurement. In the Analysis-by-Synthesis algorithm, the synthetic X-ray image of the implant is matched to its original X-ray projection. This intensity based approach and the use of X-ray images with their inherent high resolution allow principally precise measurements. Wear has been defined based on the estimated implant parameters and under minimization of the impact of the main sources of error. The latter was theoretically studied in a sensitivity analysis. The use of the algorithm was tested in vitro as well as in vivo. In experimental data, the accuracy and the impact of the pelvic position and orientation were studied. The precision was assessed using dual radiographs of 20 patients with total hip replacement. A standard deviation of 49 microm was found.