Biomedical subjects

Per Wretenberg

Publications and source records attributed to Per Wretenberg.

6 recordsLinked to original sources

PubMed2007

In vivo knee kinematics during gait reveals new rotation profiles and smaller translations.

In order to identify abnormal or pathological motions associated with clinically relevant questions such as injury mechanisms or factors leading to joint degeneration, it is essential to determine the range of normal tibiofemoral motion of the healthy knee. In this study we measured in vivo 3D tibiofemoral motion of the knee during gait and characterized the nonsagittal plane rotations and translations in a group of six healthy young adults. The subjects were instrumented with markers placed on intracortical pins inserted into the tibia and femur as well as marker clusters placed on the skin of the thigh and shank. The secondary rotations and translation excursions of the knee were much smaller than those derived from skin markers and previously described in the literature. Also, for a given knee flexion angle, multiple combinations of transverse and frontal plane knee translation or rotation positions were found. This represents normal knee joint motions and ensemble averaging of gait data may mask this important subject-specific information.

Adult↗

PubMed2006

Radial head prosthesis after fracture of radial head with associated elbow instability.

INTRODUCTION: Fractures of the radial head and associated elbow instability can be treated with operation with radial head prosthesis. In this study, we evaluate function 1-7 years after implantation and also function after removal of five prostheses. MATERIAL AND METHODS: Eighteen patients with radial head fracture and associated elbow instability were evaluated 3.7 years (1-7) after implantation of a radial head prosthesis. Pain at rest and during activity was measured with a visual analogue scale (VAS). Test of stability and neurological examination was done manually as well as measurement of the range of motion, using a goniometer. Activity of daily living (ADL) was estimated using five questions where the answers were graded between 1 and 3. The patients were asked to grade their general satisfaction according to the following scale; very satisfied, satisfied, not satisfied, disappointed. Plain X-rays were taken and 14 patients agreed to have their elbow strength evaluated using the validated BTE work simulator. RESULTS: Five prostheses had been extracted due to poor range of motion. All these patients improved after extraction. All elbows were stable. No patient with extracted prosthesis had VAS score >2. The mean extension defect for this group was 15 degrees (5-25) compared to the mean extension defect for the 13 patients with the prosthesis still in place 15 degrees (0-40). The highest VAS score for the patients with prosthesis was five but the mean as low as 0.8. In the whole group, 13 patients were pain free. ADL function was good in general. The X-rays of the prostheses, still in place, showed radiolucent lines in 7 of the 13 patients. In the whole group, there was a significant decrease in supination, flexion and extension strength (P<0.01, P<0.01, P<0.05). DISCUSSION: Radial head prosthesis works as a spacer after fracture of the radial head and associated instability. If range of motion is much restricted post-operatively, the prosthesis can be removed with improved function as result.

Adult↗

PubMed2005

Effect of skin movement artifact on knee kinematics during gait and cutting motions measured in vivo.

Eight healthy male subjects had intra-cortical bone-pins inserted into the proximal tibia and distal femur. Three reflective markers were attached to each bone-pin and four reflective markers were mounted on the skin of the tibia and thigh, respectively. Roentgen-stereophotogrammetric analysis (RSA) was used to determine the anatomical reference frame of the tibia and femur. Knee joint motion was recorded during walking and cutting using infrared cameras sampling at 120Hz. The kinematics derived from the bone-pin markers were compared with that of the skin-markers. Average rotational errors of up to 4.4 degrees and 13.1 degrees and translational errors of up to 13.0 and 16.1mm were noted for the walk and cut, respectively. Although skin-marker derived kinematics could provide repeatable results this was not representative of the motion of the underlying bones. A standard error of measurement is proposed for the reporting of 3D knee joint kinematics.

Adult↗

PubMed2005

Direct activation of glucose transport in primary human myotubes after activation of peroxisome proliferator-activated receptor delta.

Activators of peroxisome proliferator-activated receptor (PPAR)gamma have been studied intensively for their insulin-sensitizing properties and antidiabetic effects. Recently, a specific PPARdelta activator (GW501516) was reported to attenuate plasma glucose and insulin levels when administered to genetically obese ob/ob mice. This study was performed to determine whether specific activation of PPARdelta has direct effects on insulin action in skeletal muscle. Specific activation of PPARdelta using two pharmacological agonists (GW501516 and GW0742) increased glucose uptake independently of insulin in differentiated C2C12 myotubes. In cultured primary human skeletal myotubes, GW501516 increased glucose uptake independently of insulin and enhanced subsequent insulin stimulation. PPARdelta agonists increased the respective phosphorylation and expression of AMP-activated protein kinase 1.9-fold (P < 0.05) and 1.8-fold (P < 0.05), of extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase (MAPK) 2.2-fold (P < 0.05) and 1.7-fold (P < 0.05), and of p38 MAPK 1.2-fold (P < 0.05) and 1.4-fold (P < 0.05). Basal and insulin-stimulated protein kinase B/Akt was unaltered in cells preexposed to PPARdelta agonists. Preincubation of myotubes with the p38 MAPK inhibitor SB203580 reduced insulin- and PPARdelta-mediated increase in glucose uptake, whereas the mitogen-activated protein kinase kinase inhibitor PD98059 was without effect. PPARdelta agonists reduced mRNA expression of PPARdelta, sterol regulatory element binding protein (SREBP)-1a, and SREBP-1c (P < 0.05). In contrast, mRNA expression of PPARgamma, PPARgamma coactivator 1, GLUT1, and GLUT4 was unaltered. Our results provide evidence to suggest that PPARdelta agonists increase glucose metabolism and promote gene regulatory responses in cultured human skeletal muscle. Moreover, we provide biological validation of PPARdelta as a potential target for antidiabetic therapy.

Adipocytes↗

PubMed2002

Tibiofemoral contact points relative to flexion angle measured with MRI.

OBJECTIVE: To determine whether knee flexion influenced bony contact movements during flexion. DESIGN: Accurate three-dimensional (3D) measurements of tibiofemoral bony contact points in vivo was performed using magnetic resonance imaging technology at 0 degrees, 30 degrees and 60 degrees of flexion. BACKGROUND: Magnetic resonance imaging is an accurate non-invasive tool for visualizing muscles, tendons, and bone, and provides precise 3D co-ordinates. METHODS: Magnetic resonance imaging recordings were made from the right knee of 16 subjects with no history of knee dysfunction at 0 degrees, 30 degrees and 60 degrees of flexion. Joint contact movements were reported as changes of the contact point's position on the medial and lateral tibial condyle with respect to a fixed reference point for each flexion angle. RESULTS: The dominant motion of the centroid of the contact area was posterior with a concomitant inferior and lateral displacement when flexing from 0-30 degrees. Increased flexion to 60 degrees the contact points moved slightly anterior, superior and continued laterally. Comparing movements between the medial and lateral compartments, larger displacement magnitudes were observed laterally. Additionally, tibial rotations of 3-5 degrees were noted relative to the femur. CONCLUSION: Based on magnetic resonance imaging co-ordinates and the rotated anatomical reference frame, the geometric equations to derive the contact point between the tibiofemoral articulating surfaces is a viable means to investigate tibiofemoral bony contact movement. RELEVANCE: Contact areas and pressure distributions have been reported using cadaveric specimens but interpretation of the results is limited. Other investigations have been restricted to sagittal plane movement. Using kinematic magnetic resonance imaging, accurate non-invasive 3D recordings of the normal knee at increments of flexion are possible. The normative baseline date can be compared against that of the pathological knee, such as cruciate ligament injury or the status of post-operative meniscectomy in order to examine skeletal joint motion and stability.

Adult↗

PubMed2002

Broken wings--common with the Hardinger plug.

We used the Hardinger occluder plug in 51 consecutive total hip arthroplasties. In 34 hips, 1 or more of the 12 polyethylene wings fractured and could be washed out from the canal. As many as 7 wings were loose in 2 arthroplasties. Although numerous wings were broken, no failure occurred in occlusion. The placement of loose wings in the femoral canal was studied by cementing a Charnley prosthesis in a saw-bone prepared with loose wings. The model was cut into slices. We found that the plastic wings could come into contact with both the bone and prosthesis.

Hip Prosthesis↗