PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 7546686

Hydroxyapatite orbital implants. Experience with 100 cases.

A McNab
View original source ↗Export metadata ↓

Abstract

BACKGROUND: The hydroxyapatite (HA) intraorbital implant is a relatively new implant made from the porous skeleton of a coral species which allows fibrovascular ingrowth and therefore tissue integration. After fibrovascular ingrowth, a hole can be drilled in the implant and a motility peg inserted to increase movements of the prosthesis by coupling the implant to the prosthesis. METHOD: The records of the first 100 cases of HA intraorbital implants inserted by the one surgeon were analysed for complications, pain and nausea postoperatively, length of hospital stay, and further surgical procedures required. A series of acrylic implants inserted by the same surgeon was used for comparison. RESULTS: Twenty-five primary and 75 secondary HA implants were performed in patients ranging from six to 74 years of age. All were covered in donor sclera. Follow-up was three to 34 months (mean 16.9, median 17.0). Complications occurred in 15 patients and included too large an implant (seven cases) requiring surgical reduction, scleral exposure in three (repair required in one), an early small exposure of the coral in one case, late thinning of the conjunctiva and later exposure of the implant in one, and shallowing of the inferior fornix requiring mucous membrane grafting in three. No implants migrated, extruded or became infected. Of 80 patients beyond six months follow-up, 28 (35%) had insertion of motility pegs, and six (7.5%) of these suffered minor complications related to the peg. Compared to patients having acrylic implants, the postoperative analgesic requirements and length of hospital stay were significantly greater for the HA patients. CONCLUSIONS: Hydroxyapatite intraorbital implants represent a significant advance over other implants and offer a more stable, safe alternative. They also offer the possibility of improved prosthesis motility. The additional cost of the implant, prolonged hospital stay and postoperative pain, should be considered in recommending such implants to patients either as primary or secondary implants.

Explore related subjects

AcrylatesAdolescentAdultAgedBiocompatible MaterialsChildDurapatiteEye EnucleationFemaleFollow-Up StudiesHumansMaleMiddle AgedOrbitPostoperative ComplicationsProstheses and ImplantsReoperationComparative StudyJournal Article

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

A McNab. 1995. Hydroxyapatite orbital implants. Experience with 100 cases.. https://doi.org/10.1111/j.1442-9071.1995.tb00139.x

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2004

MexAB-OprM specific efflux pump inhibitors in Pseudomonas aeruginosa. Part 4: Addressing the problem of poor stability due to photoisomerization of an acrylic acid moiety.

Exchange of the ethylene tether in a series of pyridopyrimidine-based MexAB-OprM specific efflux pump inhibitors to an amide bond stabilized the olefin of the acrylic acid moiety, preventing facile photoisomerization to the Z-isomer. Furthermore, the activity was drastically improved in the amide tether variants, providing extremely potent acrylic acid and vinyl tetrazole analogues.

Acrylates↗
PubMed2004

The roles of active-site residues in the catalytic mechanism of trans-3-chloroacrylic acid dehalogenase: a kinetic, NMR, and mutational analysis.

trans-3-Chloroacrylic acid dehalogenase (CaaD) converts trans-3-chloroacrylic acid to malonate semialdehyde by the addition of H(2)O to the C-2, C-3 double bond, followed by the loss of HCl from the C-3 position. Sequence similarity between CaaD, an (alphabeta)(3) heterohexamer (molecular weight 47,547), and 4-oxalocrotonate tautomerase (4-OT), an (alpha)(6) homohexamer, distinguishes CaaD from those hydrolytic dehalogenases that form alkyl-enzyme intermediates. The recently solved X-ray structure of CaaD demonstrates that betaPro-1 (i.e., Pro-1 of the beta subunit), alphaArg-8, alphaArg-11, and alphaGlu-52 are at or near the active site, and the >or=10(3.4)-fold decreases in k(cat) on mutating these residues implicate them as mechanistically important. The effect of pH on k(cat)/K(m) indicates a catalytic base with a pK(a) of 7.6 and an acid with a pK(a) of 9.2. NMR titration of (15)N-labeled wild-type CaaD yielded pK(a) values of 9.3 and 11.1 for the N-terminal prolines, while the fully active but unstable alphaP1A mutant showed a pK(a) of 9.7 (for the betaPro-1), implicating betaPro-1 as the acid catalyst, which may protonate C-2 of the substrate. These results provide the first evidence for an amino-terminal proline, conserved in all known tautomerase superfamily members, functioning as a general acid, rather than as a general base as in 4-OT. Hence, a reasonable candidate for the general base in CaaD is the active site residue alphaGlu-52. CaaD has 10 arginine residues, six in the alpha-subunit (Arg-8, Arg-11, Arg-17, Arg-25, Arg-35, and Arg-43), and four in the beta-subunit (Arg-15, Arg-21, Arg-55, and Arg-65). (1)H-(15)N-heteronuclear single quantum coherence (HSQC) spectra of CaaD showed seven to nine Arg-NepsilonH resonances (denoted R(A) to R(I)) depending on the protein concentration and pH. One of these signals (R(D)) disappeared in the spectrum of the largely inactive alphaR11A mutant (deltaH = 7.11 ppm, deltaN = 89.5 ppm), and another one (R(G)) disappeared in the spectrum of the inactive alphaR8A mutant (deltaH = 7.48 ppm, deltaN = 89.6 ppm), thereby assigning these resonances to alphaArg-11NepsilonH, and alphaArg-8NepsilonH, respectively. (1)H-(15)N-HSQC titration of the enzyme with the substrate analogue 3-chloro-2-butenoic acid (3-CBA), a competitive inhibitor (K(I)(slope) = 0.35 +/- 0.06 mM), resulted in progressive downfield shifts of the alphaArg-8Nepsilon resonance yielding a K(D) = 0.77 +/- 0.44 mM, comparable to the (K(I)(slope), suggestive of active site binding. Increasing the pH of free CaaD to 8.9 at 5 degrees C resulted in the disappearance of all nine Arg-NepsilonH resonances due to base-catalyzed NepsilonH exchange. Saturating the enzyme with 3-CBA (16 mM) induced the reappearance of two NepsilonH signals, those of alphaArg-8 and alphaArg-11, indicating that the binding of the substrate analogue 3-CBA selectively slows the NepsilonH exchange rates of these two arginine residues. The kinetic and NMR data thus indicate that betaPro-1 is the acid catalyst, alphaGlu-52 is a reasonable candidate for the general base, and alphaArg-8 and alphaArg-11 participate in substrate binding and in stabilizing the aci-carboxylate intermediate in a Michael addition mechanism.

Acrylates↗
PubMed2004

Structure-based design of potent retinoid X receptor alpha agonists.

A series of tetrahydrobenzofuranyl and tetrahydrobenzothienyl propenoic acids that showed potent agonist activity against RXRalpha were synthesized via a structure-based design approach. Among the compounds studied, 46a,b showed not only very good potency against RXRalpha (K(i) = 6 nM) but was also found to be greater than 167-fold selective vs RARalpha (K(i) > 1000 nM). This compound profiled out as a full agonist in a cell-based transient transfection assay (EC(50) = 3 nM). The two antipodes were separated via chiral chromatography, and 46b was found to be 40-fold more potent than 46a. Interestingly, cocrystallization of 46a,b with the RXRalpha protein generated a liganded structure whereby the (S)-antipode was found in the binding pocket. Given orally in db/db mice or ZDF rats, 46a,b showed a significant glucose-lowering effect and an increase in liver mass. Triglycerides decreased significantly in db/db mice but increased in the ZDF rats. A dose-dependent decrease of nonesterified free fatty acids was seen in ZDF rats but not in db/db mice. These differences indicate a species specific effect of RXR agonists on lipid metabolism.

Acrylates↗