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Biomedical subjects

E Gómez-Barrena

Publications and source records attributed to E Gómez-Barrena.

14 recordsLinked to original sources
PubMed2006

Proprioception in the ACL-ruptured knee: the contribution of the medial collateral ligament and patellar ligament. An in vivo experimental study in the cat.

In the absence of anterior cruciate ligament (ACL), secondary restraints such as menisci, ligaments, and tendons restrict anterior knee laxity. Strain detection at these sites could define the contribution of this alternative signalling system to knee proprioception after ACL injury. The hypothesis in this study questions if measurements of anterior tibial translation (ATT) from surface strain gauges on the insertions of the medial collateral ligament (MCL) and the patellar tendon (PT) are sufficiently sensitive and specific to differentiate normal, stable knees from acutely unstable knees due to ACL section. Twelve cats received miniaturized strain gauges on the surface of MCL and PT distal insertions. A purpose-made receiver transformed into measurements any voltage variation obtained during passive knee flexion-extension and anterior tibial translation manoeuvres. Variables under evaluation included first peak latency, normalized amplitude, and slope of voltage along time. Femorotibial displacements were video recorded, digitized, and used as the ATT reference. The proposed system detected significant changes in the slope of the voltage/time signal, with higher specificity and sensitivity during ATT after experimental ACL section. Changes were not significant during flexion or extension. It was found that a pattern of earlier and more intense strain in MCL and PT distal insertions was found during ATT in the ACL deficient knee. Enhanced pattern recognition learning from these structures could be a future target for proprioceptive training after ACL injury.

Animals↗
PubMed2004

Comparative cyclic stress-strain and fatigue resistance behavior of electron-beam- and gamma-irradiated ultrahigh molecular weight polyethylene.

Fatigue-related damage in UHMWPE is one of the main causes of long-term failure in total joint replacements. Crosslinking ultrahigh molecular weight polyethylene (UHMWPE) by gamma or electron-beam irradiation, in combination with prior or further thermal treatment, enhances its wear resistance against metallic components in total hip replacements, and eventually in knees. However, little information is available on the fatigue response of this modified UHMWPE. The objective of this study was to compare electron-beam-irradiated UHMWPE at 50, 100, and 150 kGy, with the well-known 25 kGy gamma-irradiated UHMWPE. Two different cyclic tests were performed under tensile stress, with a zero load ratio, R = 0. First, specimens were subjected to a sinusoidal load cycle at 1 Hz, which provided stress-life curves with the use of a failure criterion based on 12% yield strain. Second, specimens were tested under 50 load cycles at a displacement rate of 15 mm/min, which provided information about the evolution of secant modulus and plastic strain. The incubation period was also analyzed. DSC measurements were carried out to check the crystallization effect of irradiation. According to the results of fatigue resistance there was a crossover behavior between gamma- and electron-beam-irradiated UHMWPE regarding the applied stress. When the stress was higher than the crossover value, the fatigue resistance of gamma-irradiated samples was higher than electron-beam-irradiated ones. When the stress was lower, the fatigue behavior was the opposite. The crossover stress depended on the electron-beam-irradiation dose. The clinical relevance of this study lies in an improved knowledge of electron-beam-irradiated material under extreme mechanical circumstances, such as fatigue.

Biocompatible Materials↗
PubMed2004

Fractography evolution in accelerated aging of UHMWPE after gamma irradiation in air.

We studied the fracture surface evolution of ultra high molecular weight polyethylene (UHMWPE) specimens, manufactured from GUR 1050 compression moulded sheets, after gamma sterilisation in air followed by different aging times after thermal treatment at 120 degrees C. Degradation profiles were obtained by FTIR and DSC measurements after 0, 7, 14, 24 and 36h aging. We observed by SEM the morphology patterns at these aging times, in surface fractographies after uniaxial tensile test of standardised samples. The results pointed out clear differences between short and long aging times. At shorter times, 7h, the behaviour was similar to non-degraded UHMWPE, exhibiting ductile behaviour. At longer times, 24-36h, this thermal protocol provided a highly degraded zone in the subsurface, similar to the white band found after gamma irradiation in air followed by natural aging, although closer to the surface, at 150-200mum. The microstructure of this oxidation zone, similarly found in gamma irradiated samples shelf-aged for 6-7 years, although with different distribution of microvoids, was formed by fibrils, associated with embrittlement of the oxidised UHMWPE. In addition, the evolution of the oxidation index, the enthalpy content, the mechanical parameters, and the depth of the oxidation front deduced from the fractographies versus aging time showed that a changing behaviour in the degradation rate appeared at intermediate aging times.

Air↗
PubMed2004

Sequential changes of parathyroid hormone related protein (PTHrP) in articular cartilage during progression of inflammatory and degenerative arthritis.

OBJECTIVE: To investigate immunolocalisation of parathyroid hormone related protein (PTHrP) in two sequential models of experimental cartilage damage (inflammatory and degenerative) in order to elucidate differences in chondrocyte response to the disease. METHODS: Immunohistochemistry with a polyclonal rabbit antiserum to the N-terminal domain of PTHrP was used to detect this protein in two different rabbit models sharing progressive cartilage damage: antigen induced arthritis (AIA) and osteoarthritis (OA) secondary to partial medial meniscectomy. Cartilage specimens from early (2 days in AIA; 8 weeks in experimental OA) and late (3 weeks in AIA; 52 weeks in OA) disease were compared. RESULTS: Cell and matrix PTHrP staining in early AIA and OA was similar to that in controls. Late AIA cartilage showed a significant decrease in PTHrP positive cells and in the cartilage matrix. In contrast, at late OA stages, distinct PTHrP positivity was detected in proliferating cell clones, as assessed by proliferating cell nuclear antigen staining around cartilage damaged areas. CONCLUSION: PTHrP staining of hyaline articular cartilage shows a different pattern during progression of each type of arthritis: an overall decrease associated with the inflammatory disease, and an increase in the proliferating chondrocyte clones with degenerative arthritis.

Animals↗
PubMed2001

Fracture behavior of UHMWPE in non-implanted, shelf-aged knee prostheses after gamma irradiation in air.

We studied non-implanted ultra-high molecular weight polyethylene (UHMWPE) knee components, that were gamma-sterilized in air and shelf-aged during 6 and 7 years, to explore fracture mechanisms in the degraded material. Prior to the fractography study, we assessed degradation through FTIR and optical density measurements in microtome sections. Then, we morphologically compared the surface fractography of degraded, oxidized UHMWPE with that of non-degraded material in specimens from the same implants, fractured after uniaxial tensile tests in standardized samples. Fractography surface analysis clearly differentiated the behavior of non-degraded and degraded UHMWPE. Failure in non-degraded samples occurred through craze formation, followed by fast crack propagation. Quantitative fracture analysis suggested a ductile behavior. This was supported by the identified local plasticity in the region close to the initial flaw. In the fractography surface analysis of degraded material, a fibrillar behavior was observed. A heterogeneous domain structure appeared, showing different coarseness with multiple void sizes. Our results, based on mechanical measurements and fracture morphology in the subsurface region, confirmed the embrittlement of oxidized UHMWPE.

Biocompatible Materials↗
PubMed1999

Gold chloride technique to study articular innervation. A protocol validated through computer-assisted colorimetry.

We studied variations in gold chloride techniques to elicit neural elements within articular samples, after "in toto" staining. These techniques attempt the differentiation of neural and vascular structures. Major changes in differential staining were observed when the gold chloride concentration was empirically modified. After the rest of the technique was standardized, we selected three gold chloride solutions to perform quantitative color experiments: 1%, 0.75%, and 0.5%. Significant sections of the same thickness were acquired with a digital camera to perform computer-assisted colorimetry. Color was measured through RGB (red-green-blue) channels in vessels, nerves, and background connective tissue as an internal control. By means of multivariate regression analysis, we compared differences in color measurements after 1%, 0.75% and 0.5% gold chloride preparation. Statistically significant coefficients confirmed that red color signals in vessels after the 0.75% and the 0.5% solution were both less intense than after the 1% preparation. Green and blue signals in vessels were also significantly less intense after the 0.5% protocol than after using the 1% solution. Red color signals in nerves between the 1% and the 0.75% preparation protocols were more intense and not significantly different, while the 0.5% preparation produced significantly less intense red signals in nerves. Non-significant differences were observed in green or blue signals from nerves after any protocol. We concluded that the 0.75% gold chloride solution protocol produced more intense red signals in nerves and less intense red signals in vessels. This was the most discriminant protocol in our series, based on color signals.

Adolescent↗
PubMed1999

Anterior cruciate ligament reconstruction affects proprioception in the cat's knee.

To study the cat's knee after anterior cruciate ligament reconstruction, we compared its neural and muscular activity with that in the normal and the unstable knee. We recorded the electric activity in the articular nerves (posterior -PAN and medial -MAN) and periarticular muscles (quadriceps and hamstring) while performing passive flexion, extension, external and internal rotation, and also anterior translation of the tibia at 30 degrees and 90 degrees of flexion. The same series of maneuvers was performed in the same knees after surgical section of the anterior cruciate ligament and then after anterior cruciate reconstruction. The electric activity recorded in the reconstructed knee was compared to that in the same knee before surgery and in the same unstable knee after anterior cruciate section. We observed that the reconstructed knee, compared to the injured knee, showed a decrease in articular nerves and quadriceps activity while it regained stability. This decrease converged to the recordings in the normal knee. However, differences in MAN, PAN and hamstring activity were still present in the reconstructed knee. This suggests that, although anterior cruciate reconstruction seems beneficial for restoring articular nerve and periarticular muscle activities to a certain degree, proprioception in the reconstructed knee does not match that in the normal knee.

Action Potentials↗
PubMed1999

Studies of host response to orthopedic implants and biomaterials.

The use of implanted biomaterials in orthopedic surgery has increased rapidly during the past two decades. Total joint replacement of the hip or knee joint has become common treatment; at the same time, an increasing number of fractures are treated with osteosynthesis. The original Charnley low-friction arthroplasty of the hip is still widely used and gives in large series excellent results. Aseptic loosening of this arthroplasty has been thought to be due to wear debris of the methylmethacrylate used for fixation of the implants, or to debris generated from wear of the polyethylene socket. To date, many different materials have been tried in order to reduce wear and generation of macrophage irritating submicron sized particles, or to provide more biocompatible components. However, trials to improve the methylmethacrylate cement or to invent better polyethylenes have often failed. Diamond coating of the metallic components seems promising: there is less wear and diamond is very biocompatible in bulk and small particulate form. Biodegradable implants have also been found useful in treating fractures. Bioactive bioabsorbable materials may also make possible a tissue engineering approach and can be used as carriers for selected drugs and cytokines. Because many promising materials and designs have failed in clinical use, extensive theoretical and experimental testing is mandatory before introducing new materials and implants in a clinical setting.

Biocompatible Materials↗
PubMed1998

Role of polyethylene oxidation and consolidation defects in cup performance.

Quality factors such as particle consolidation and oxidation have been claimed to impair the performance of ultrahigh molecular weight polyethylene implants, but no definite data estimate their real effect. To assess the influence of these quality determinants in wear, wear rate, and time in service at a single, well proven design, the percentage area of polyethylene sections occupied by nonconsolidated polyethylene particles, the presence of a white band, and the amount of polyethylene oxidation (through density curves) were evaluated in 92 retrieved Charnley acetabular components with available clinical data. The average percentage area of nonconsolidated polyethylene particles in cup sections was 3.1%. There were 11 cups showing a subsurface white band. The authors observed an average density in the deep polyethylene of 0.9420 g/cc after an average in vivo use of 9.8 years (range, 0.08-20.3 years). Banded cups showed significantly higher subsurface densities. When studying the relationship among clinical and material factors with performance variables, wear measurements (obtained through radiographic methods and direct measurements of polyethylene thickness in the collected implants) correlated with age at implantation, activity, and time in service. Weight was a determinant of the wear rate. None of the studied polyethylene quality factors showed a definite association with wear performance or time to failure in this series. Implant survivorship was not significantly impaired in the 22.225-mm Charnley low friction replacement by a subsurface white band or by a higher area occupied by nonconsolidated particles. Fewer nonconsolidated particles were not associated with longer survivorship. This design proved tolerance to polyethylene quality variations, in the signaled ranges, without a significant effect in the system performance.

Arthroplasty, Replacement, Hip↗
PubMed1997

Neural and muscular electric activity in the cat's knee. Changes when the anterior cruciate ligament is transected.

We studied the response of the normal and unstable knee to passive motion and anterior tibial displacement in the cat. 6 cats were anesthetized and the deep level of anesthesia was controlled by electroencephalograms. We recorded electric activity in the articular nerves (posterior PAN and medial MAN) and periarticular muscles (quadriceps and hamstring), while performing passive flexion, extension, internal and external rotation. We then produced anterior displacement of the tibia at 30 degrees and 90 degrees of flexion, as in the Lachman and the anterior drawer maneuvers. The anterior cruciate ligament was surgically sectioned and the same series of passive displacements was performed. We observed statistically significant increased activity in the MAN, the PAN and the quadriceps muscle during knee flexion, in the MAN during extension, and in the PAN and hamstring during external rotation with the knee 90 degrees flexed. Anterior cruciate transection caused anterior displacement of the tibia during stress. This produced a significant increase in the MAN activity and a significant decrease in the hamstring electric activity at 30 degrees and 90 degrees of flexion, as in Lachman and anterior drawer maneuvers. We conclude that electric activity in the articular nerves and periarticular muscles, in response to passive motion and anterior tibial displacement, is altered in the cat's knee after anterior cruciate transection. This suggests that various patterns of periarticular muscle reaction in the anterior cruciate-deficient knee may be related to the unconscious perception of abnormal motion.

Animals↗
PubMed1996

Segmental sensory innervation of the anterior cruciate ligament and the patellar tendon of the cat's knee.

We performed a study in cats to describe and quantify the segmental sensory innervation of the anterior cruciate ligament of the knee. We also studied the patellar tendon to show that transport occurs from an extraarticular, dense connective tissue structure and to obtain comparable quantitative information. We injected a tracer (horseradish peroxidase HRP, coupled to wheat germ agglutinin WGA) in the anterior cruciate ligament and observed the reaction product in the articular nerves of the injected knee and in the cell bodies of ipsilateral dorsal root ganglia. In these experiments, we found an average of 26 (13-52) labeled neurons, mostly large, after injecting the anterior cruciate. More than half of the labeled neurons were found in the dorsal root ganglion of L7 (last lumbar segment in the cat). We counted an average of 204 (17-426) labeled neurons, mostly small, after injecting the patellar tendon. More than half of these labeled neurons were found in the L5 spinal ganglion. No product was observed in contralateral spinal ganglia. Surgical ablation of the medial and lateral articular nerves (MAN and LAN) before injecting HRP-WGA in the anterior cruciate ligament, showed that the remaining afferents in the posterior articular nerve (PAN) projected mainly to L7. After excision of PAN, the projection was maintained through MAN and LAN, mostly to L5. Our quantitative data show that the anterior cruciate ligament is poorly innervated, if compared to the patellar tendon. The anterior cruciate segmental sensory innervation is directed to L7 (corresponding to the main ventral root forming the sciatic nerve in the cat), but also to L5 and L6 (main femoral nerve ventral roots). These segmental data indicate that anterior cruciate innervation influences muscle tone regulation, not only of the hamstrings (neuromuscular system of the sciatic nerve), but also of the quadriceps muscle (neuromuscular system of the femoral nerve).

Animals↗
PubMed1995

Traumatic dislocation of the tibialis posterior tendon: a new surgical procedure to obtain a strong reconstruction.

Traumatic dislocation of the tibialis posterior tendon (TPT) is an uncommon condition. The diagnosis is difficult and may be delayed, impairing the activity level. The authors present a case, wherein the diagnosis was clinical, supported by magnetic resonance imaging. Treatment was surgical; reconstruction of the retinaculum was performed with a medial slip of the Achilles tendon that was detached proximally and attached to the medial malleolus. A full functional recovery to a highly competitive activity was obtained after 12 weeks.

Adult↗
PubMedDate not supplied

Interleukin-6 in aseptic loosening of total hip replacement prostheses.

OBJECTIVE: To investigate the level of interleukin-6 (IL-6) expression in the synovial-like interface membrane (SLIM) and in the pseudosynovial tissue surrounding the artificial hip joints, as well as in the pseudosynovial fluid from aseptically loosened total hip replacement (THR) prostheses. METHODS: A series of methods were used in this study including immunohistochemical staining, double immunofluorescence labeling, enzyme-linked immunosorbent assay (ELISA), and reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: IL-6 was found in all SLIM and the pseudosynovial tissue samples from aseptic loosening of THR. Semi-quantitative morphometry showed that IL-6 containing cells were more numerous in the SLIM (911 +/- 197; p < 0.01) and the pseudosynovial tissue samples (883 +/- 310; p < 0.01) than in the control synovial tissue (291 +/- 184). Double labeling confirmed that macrophages and fibroblasts were the predominant cell types expressing IL-6. These findings were confirmed by RT-PCR. ELISA revealed no difference in the IL-6 concentration between the pseudosynovial fluid and the control synovial fluid obtained from the patients undergoing hip arthroscopy. CONCLUSIONS: IL-6 locally produced in SLIM may in a paracrine manner contribute to periprosthetic osteolysis of the nearby bone. In contrast, fluid phase IL-6 does not seem to contribute to this end.

Adult↗