[Biomechanical parameters and clinical outcomes of the Oxford Phase III unicompartmental knee replacement]

PURPOSE OF THE STUDY

The kinematics of an intact knee joint and that of a knee replacement have been studied in many research centres. In the 1987 radiographic study, Bradley, Goodfellow and O'Connor reported the movement of a polyethylene insert in patients with unicompartmental Oxford knee replacement. Views with the knee at full extension and 90° of flexion were obtained and the movement of the meniscal bearings over this range of flexion was measured. The bearings were found to move backwards on the tibia through an average distance of 4.4 mm in all 16 patients. This measurement was in agreement with the then valid concept of knee biomechanics and a roll-back phenomenon. However, our observations had not always agreed with the results of these authors, but gave an impetus for a detailed evaluation of our own patient group. The aim of the study was to evaluate the dynamic relationship between the components of a unicompartmental Oxford knee replacement and elucidate it with the use of recent information from the field of biomechanics. A relationship of the obtained kinematic values to clinical outcomes was also investigated. Answers to the following hypotheses were sought: Would our results be in agreement with the British authors' findings? Would clinical outcomes depend on the kinematic properties of knee replacements?

MATERIAL AND METHODS

The group comprised 33 patients, 23 women and 10 men. They all had replacement of the medial compartment of the knee. The construction of the unicompartmental Oxford Phase III knee replacement enabled us to locate the centre of rotation of the medial femoral condyle in relation to the tibial component at flexion and extension of the knee, using radiography. The patients were examined in a supine position with the knee at full extension, and subsequently views of the knee were obtained at 80°-90° flexion in accordance with the method used by the British authors. The clinical findings of knee joints were assessed using the American Knee Society (AKS) scoring system (Insall et al.). Pain was rated on the Visual Analogue Scale (VAS). The results were statistically evaluated with the t-test and Chi-square test.

RESULTS

On moving the knee from extension to flexion, movement of the polyethylene insert ventrally by an average of 3.4 mm in relation to the tibia was recorded, i.e., "paradoxical" ventral translocation. In the patients with insert movement less than or equal to 3 mm, the average AKS score was 89 points, in those with movement over 3 mm it was 87 points. The average functional scores were 87 and 83 points in the patients with movement less than 3 mm and more than 3 mm, respectively. The average VAS score was 1.55 in the former and 1.18 in the latter.

DISCUSSION

The unicompartmental Oxford Phase III knee replacement substitutes a flexion femoral facet and eliminates the role of an extension femoral facet. This is the reason why, at knee extension between -5° and +20°, the centre of rotation of the medial femoral condyle is in the centre of the flexion facet and not in that of the extension facet. When the stabilising functions of the extension tibial facet in the ventral direction and of the dorsal part of the insert in the dorsal direction are missing, the position of the contact surface centre becomes much dependent also on the strength and direction of external forces acting in the knee joint vicinity.

CONCLUSIONS

The kinematic parameters of the unicompartmental Oxford Phase III knee replacement investigated in our group differed from the findings of the British authors. However, neither the magnitude nor the direction of movement had any effect on the clinical outcome of knee arthroplasty.

Fluorescent polyurethane nanofabrics: a source of singlet oxygen and oxygen sensing

Polyurethane (PUR) nanofabrics based on nanofibers of average diameters in the range of 250-110 nm with different meso-tetraphenylporphyrin (TPP) loading (0.01-5 wt %) were prepared by an electrospinning process. The oxygen quenching of excited states and singlet oxygen-sensitized delayed fluorescence (SODF) of TPP were studied at different oxygen pressures. We found that TPP in PUR matrix is present in monomeric state, and it is easily accessed by oxygen. Analysis of the kinetics of the TPP triplet, singlet oxygen, and SODF indicates that repopulation of TPP fluorescent state includes reaction of singlet oxygen with TPP triplets. The integrated SODF achieved more than 20% of the prompt fluorescence for nanofabric loaded with 5 wt % TPP. The dependence of SODF intensity on the TPP concentration in nanofibers is nearly quadratic.

Self-assemblies of cationic porphyrins with functionalized water-soluble single-walled carbon nanotubes

5,10,15,20-tetrakis(4-N-methylpyridyl)porphyrin, 5,10,15,20-tetrakis(2-N-methylpyridyl)porphyrin, and 5,10,15,20-tetrakis(4-trimethylammoniophenyl)porphyrin form self-assemblies with single-walled carbon nanotubes (SWNT) functionalized by polyaminobenzene sulfonic acid. Both steady-state and time-resolved emission studies revealed efficient quenching of the excited singlet states of the porphyrins. Atomic force microscopy, fluorescence confocal microscopy, and fluorescence lifetime imaging allowed the visualization of individual bundles of SWNTs and the differentiation of porphyrin molecules at specific binding sites of SWNT.

Cyclodextrin carriers of positively charged porphyrin sensitizers

The cationic sensitizer 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP) forms supramolecular complexes with native, per-methylated, sulfonated and dimethyl-sulfonated cyclodextrins (CDs). Binding interactions were proved by NMR, mass spectra, capillary zone electrophoresis, UV-Vis and fluorescence spectroscopy. The 2D-NMR experiments on native CDs indicate that the interaction of TMPyP with the external CD surface is the dominant binding mode. The high binding affinity of TMPyP towards sulfonated CDs is due to electrostatic interactions. Binding is accompanied by an increase of the TMPyP basicity. Whereas betaCD does not affect the lifetime of the TMPyP triplet states, binding with sulfonated CDs causes the protonation of the TMPyP triplet states even in neutral solution. The diprotonated anionic sensitizer 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPSH(2)(2+)) forms host-guest complexes with native betaCD and gammaCD, similarly as in its non-protonated state. The positive charge of pyrrole nitrogen atoms does not significantly influence the mode of the interaction. In contrast to TMPyP, the lifetimes of the triplet states of bound TPPSH(2)(2+) to native CDs increase.

Dispersion of light and heavy pollutants in urban scale models: CO(2) laser photoacoustic studies

The distribution of pollutants in two urban scale models (point emission source and street canyon with extensive transport) was investigated by means of CO(2) laser photoacoustic spectroscopy in the region of the atmospheric window (9-10 mum). The experimental results of physical modeling are in a good agreement with the numerical calculations performed in the frame of computational fluid dynamic (CFD) modeling. Methanol, ethanol, and ozone (examples of light pollutants), as well as sulfur hexafluoride and 1,2 dichlorethane (examples of heavy pollutants), were selected on the basis of their high resolution spectra acquired by Fourier transform and laser diode spectroscopy.

Interaction of porphyrins with a dendrimer template: self-aggregation controlled by pH

The interaction between self-aggregated porphyrins such as 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and 5,10,15,20-tetrakis(4-phosphonatophenyl)porphyrin (TPPP), and a generation 5 (G5) PAMAM dendrimer template is governed by minute differences of porphyrin acido-basic properties. While at neutral pH both monomeric TPPS and TPPP form complexes with G5, decreasing pH did not lead to porphyrin ring protonation (pK(a) approximately 5) but rather to the preferential formation of H-aggregates (probably H-dimers), most likely due to protonation of the G5. Upon further acidification of the solution, this face-to-face orientation of the porphyrin units is being converted to edge-to-edge aligned J-aggregates with a tightly defined structure. This process starts by protonation of the porphyrin ring at pH below 2.3 and 2.8 for TPPS and TPPP, respectively. The AFM imaging of porphyrin/G5 nanostructures obtained at pH 0.7 shows the formation of long nanorods of TPPS with partially aggregated G5 and small aggregates of TPPP connected to individual G5 molecules.

Formation of lanthanide(III) texaphyrin complexes with DNA controlled by the size of the central metal cation

Interaction of lanthanide(III) texaphyrins (LnTEX) with calf thymus DNA was studied by UV-Vis, CD, resonance light scattering spectroscopy and by laser flash photolysis. The thermal stability of the LnTEX/DNA complexes decreases with the increasing lanthanide ion radius: LuTEX>DyTEX>GdTEX>EuTEX>CeTEX> or =LaTEX. Texaphyrins LaTEX, LuTEX and GdTEX produce O2(1Deltag) in methanol solutions. In a phosphate buffer, the concentration of O2(1Deltag) produced by these texaphyrins bound to DNA is affected by the formation of aggregates on the DNA backbone.

Modulation of porphyrin binding to serum albumin by pH

In this study, we show that the difference in acidity of functional groups in porphyrin photosensitizers provides a meaningful avenue to achieve differential localization and retention of porphyrins in tissues and cells, and in the end could be a positive factor in the photodynamic treatment of cancer (PDT). We have demonstrated that meso-tetraphenylporphyrin derivative with four phosphonate (bond P(double bond O)(bond OH)(2)) moieties exists in aqueous solutions mainly in four forms that differ by a degree of protonation of the porphyrin ring and ionization of the phosphonate group. It is shown that each porphyrin form has different affinities toward the model protein (bovine serum albumin, BSA). Thus pH of the medium significantly modulates the affinity of the phosphonate porphyrin toward BSA. At lower pH (pH 6.0), the phosphonate porphyrin and BSA form a complex with affinity constant of K(b)=6.9 x 10(5) M(-1), while at pH 7.0 the K(b)=6.1 x 10(5) M(-1). At pH 8.0 the association is significantly lower. Because cancerous cells have generally lower pH (pH approximately 6.9) compared to healthy cells (pH approximately 7.4), the pH of such cells could be a decisive factor for cellular retention of the porphyrin in the form of an associate with intracellular proteins. Moreover, we have also demonstrated that the protonation/deprotonation equilibria do not negatively affect the photophysical properties or ability of phosphonate porphyrin to generate singlet oxygen.

[Long-term results of unicompartmental knee joint replacement]

PURPOSE OF THE STUDY

To evaluate the long-term results of unicompartmental knee joint alloplasty (UKA) in a group of 21 patients. On the basis of their own results and literature data, the authors discuss effective strategies for treatment of unicompartmental osteoarthritis of the knee joint.

MATERIAL

A group of 21 patients, who were implanted a total of 22 unicompartmental knee replacements, type St. Georg, Waldemar Link, between 1986 and 1992, were followed-up till 2002. Since two patients living permanently abroad were excluded, the group at the final evaluation consisted of 19 patients with a total of 20 knee replacements.

METHODS

In 2002, all patients were clinically and radiologically examined. They were interviewed about their subjective evaluation of the knee joint after alloplasty, and clinical and functional findings were assessed. The evaluation of long-term results was based on The Knee Society Clinical Rating System.

RESULTS

The average Knee Score value was 84 points and average Function Score value was 78 points. Out of the 20 knee replacements evaluated, only one failure of UKA was recorded at 9 years after the primary implantation.

DISCUSSION

The authors discuss the current state of treatment in unicompartmental knee arthritis and present several different views based on literature sources. Opinions on indications for specific surgical methods are still controversial. The authors draw attention to comparisons of long-term results between patients with UKA and patients who underwent high tibial valgus osteotomy or total knee replacement. They discuss the advantages and disadvantages of UKA in comparison with the other therapies. They also pay some attention to repeat surgery in failed UKA.

CONCLUSIONS

UKA implantation is a surgical method of managing unicompartmental arthritis of the knee joint. The results presented by the authors and corroborated by many literature data provide evidence that UKA is of great importance in the treatment of unicompartmental knee arthritis. If a consistent selection of patients is maintained, a precise operation technique is used and a reliable implant is chosen, excellent immediate as well as long-term outcomes will be achieved.