Wolfgang Fitz

Structure of the haemagglutinin-esterase-fusion glycoprotein of influenza C virus

The spike glycoproteins of the lipid-enveloped orthomyxoviruses and paramyxoviruses have three functions: to recognize the receptor on the cell surface, to mediate viral fusion with the cell membrane, and to destroy the receptor. In influenza C virus, a single glycoprotein, the haemagglutinin-esterase-fusion (HEF) protein, possesses all three functions (reviewed in ref. 1). In influenza A and B, the first two activities are mediated by haemagglutinin and the third by a second glycoprotein, neuraminidase. Here we report the crystal structure of the HEF envelope glycoprotein of influenza C virus. We have identified the receptor-binding site and the receptor-destroying enzyme (9-O -acetylesterase) sites, by using receptor analogues. The receptor-binding domain is structurally similar to the sialic acid-binding domain of influenza A haemagglutinin, but binds 9-O -acetylsialic acid. The esterase domain has a structure similar to the esterase from Streptomyces scabies and a brain acetylhydrolase,. The receptor domain is inserted into a surface loop of the esterase domain and the esterase domain is inserted into a surface loop of the stem. The stem domain is similar to that of influenza A haemagglutinin, except that the triple-stranded, α-helical bundle diverges at both of its ends, and the amino terminus of HEF2, the fusion peptide, is partially exposed. The segregation of HEFs three functions into structurally distinct domains suggests that the entire stem region, including sequences at the amino and carboxy termini of HEF1 which precede the post-translational cleavage site between HEF1 and HEF2, forms an independent fusion domain which is probably derived from an ancestral membrane fusion protein.

Patient satisfaction after primary total and unicompartmental knee arthroplasty: An age-dependent analysis

BACKGROUND Patient-related outcomes have become the focus of increased attention when assessing knee arthroplasty. METHODS We retrieved questionnaires from 485 (584 knees) patients at a minimum of 3years after undergoing primary knee arthroplasty. We excluded bilateral knee arthroplasty, leaving 141 UKA and 245 TKA who rated their satisfaction and expectation regarding pain, range of motion (ROM), daily living function (DLF), return to recreational activity (RRA) and ability to kneel (ATK) on a scale of 0 (worst) to 10 (best). We further collected data on pain level and the modified Cincinnati rating scale. Range of motion was documented pre- and postoperatively at a minimum of six months. The cohort was subdivided into three age groups and compared with each other (Group 1: <55, n=113; Group 2: 55-64, n=117; Group 3: 65+, n=155). RESULTS Average satisfaction with pain, ROM and ATK for patients under 55 was higher for UKA than for TKA. Patients>65 with TKA were on average more satisfied than patients with UKA in these three items. However, patients under 55 with UKA were up to 2.9 times more likely to have their expectations met when compared to patients receiving TKA. Patients with UKA under 55 rated their joint as good/excellent in 96.0% versus patients in the same age group with TKA in 81.0%. CONCLUSIONS We found that overall, younger patients who were treated with UKA demonstrated higher satisfaction scores in most subsets when compared with the patients of the same age group who received TKA.

Unicompartmental Knee Arthroplasty with Use of Novel Patient-Specific Resurfacing Implants and Personalized Jigs

This paper describes the surgical technique with a patient-specific resurfacing unicompartmental knee arthroplasty. The patient-specific implant is currently designed on the basis of data from preoperative computed tomography. The implant is provided with a set of patient-specific, disposable cutting jigs. Biomechanical and anatomic axes are factored into jigs from a scan obtained through the hip, knee, and ankle, effectively achieving pre-navigation of the cut planes without the need for a navigation system. The surgical technique is reduced to five simple, reproducible steps. After removing the articular cartilage, the knee is balanced to determine the correct amount of tibial resection; this is followed by femoral preparation, verification of balancing and tibial preparation, and trial and cementing of the implant. The introduction of personalized three-dimensional image-derived resurfacing implants, as well as personalized single-use instrumentation, has the potential to change the common surgical practice of unicompartmental knee arthroplasty. Patient-specific resurfacing implants enable a femoral bone-preserving approach and enhance cortical bone support on the tibia, overcoming critical design limitations of commercial off-the-shelf implants. Patient-specific resurfacing implants can restore normal anatomy, the position of the joint line, and normal joint function, with the potential to result in more normal knee kinematics.

Nanoparticulate fillers improve the mechanical strength of bone cement

Background and purpose Polymethylmethacrylate (PMMA-) based bone cement contains micrometer‐size barium sulfate or zirconium oxide particles to radiopacify the cement for radiographic monitoring during follow‐up. Considerable effort has been expended to improve the mechanical qualities of cements, largely through substitution of PMMA with new chemical structures. The introduction of these materials into clinical practice has been complicated by concerns over the unknown long‐term risk profile of these new structures in vivo. We investigated a new composite with the well characterized chemical composition of current cements, but with nanoparticles instead of the conventional, micrometer‐size barium sulfate radiopacifier. Methods In this study, we replaced the barium sulfate microparticles that are usually present in commercial PMMA cements with barium sulfate nanoparticles. The resultant “microcomposite” and “nanocomposite” cements were then characterized through morphological investigations such as ultra‐small angle X‐ray scattering (USAXS) and scanning electron microscopy (SEM). Mechanical characterization included compression, tensile, compact tension, and fatigue testing. Results SEM and USAXS showed excellent dispersion of nanoparticles. Substitution of nanoparticles for microparticles resulted in a 41% increase in tensile strain‐to‐failure (p = 0.002) and a 70% increase in tensile work‐of‐fracture (p = 0.005). The nanocomposite cement also showed a two‐fold increase in fatigue life compared to the conventional, microcomposite cement. Interpretation In summary, nanoparticulate substitution of radiopacifiers substantially improved the in vitro mechanical properties of PMMA bone cement without changing the known chemical composition.

Does a Modified Gap-balancing Technique Result in Medial-pivot Knee Kinematics in Cruciate-retaining Total Knee Arthroplasty?: A Pilot Study

BackgroundNormal knee kinematics is characterized by posterior femorotibial rollback with tibial internal rotation and medial-pivot rotation in flexion. Cruciate-retaining TKAs (CR-TKAs) do not reproduce normal knee kinematics.Questions/purposesWe hypothesized a more anatomic reconstruction of the medial femoral condyle, simultaneously preserving the tension of the PCL and medial collateral ligament, resulted in (1) medial-pivot rotation and tibial internal rotation, (2) lateral femoral rollback, and (3) reduced liftoff.Patients and MethodsWe compared 10 patients who underwent CR-TKA using the new technique at their 1-year followup to a matched control group of nine patients using a traditional gap-balancing technique at their 2- to 4-year followup. All patients received lateral radiographs in extension and flexion, which we utilized for three-dimensional implant matching to calculate tibial internal rotation, lateral rollback, and lateral liftoff in extension and flexion.ResultsThe new gap-balancing technique resulted in a median of 3.5° tibial internal rotation with 2.7-mm rollback of the lateral femoral condyle relative to the medial condyle in flexion, which was different from the control group. We found no differences in liftoff between the groups.ConclusionsThe new technique resulted in tibial internal rotation with flexion and lateral rollback comparing the lateral to the medial condyle in flexion, but no differences in condylar liftoff. These preliminary results were comparable to published kinematic results of an asymmetric CR-TKA or medial-pivot CR-TKA but not to symmetric CR-TKA.Level of Evidence Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Enzymatic synthesis of 7-deoxy-N-acetylneuraminic acid and 7-O-methyl-N-acetylneuraminic acid

Abstract 7-Deoxy- N -acetylneuraminic Acid and 7- O -methyl- N -acetylneuraminic acid were synthesized through the sialic acid aldolase-catalyzed aldol addition reactions of 4-deoxy- N -acetyl-D-mannosamine and 4- O -methyl- N -acetyl-D-mannosamine, respectively, with pyruvate. The obtained sialic acids will be used as probes for the investigation of the unusual mechanism of a novel sialidase from leech.

CT-Based Preoperative Analysis of Scapula Morphology and Glenohumeral Joint Geometry

Objective: To investigate the geometry of the glenohumeral joint using three-dimensional (3D) models; define landmarks, planes, angles and regions of interest; and analyze the exact morphology of the scapula. Materials and Methods: We reconstructed 3D scapula models based on computed tomography (CT) data sets of 12 healthy controls. Three-dimensional models were reconstructed using the 3D Slicer2® (Surgical Planning Lab, Boston, MA), which provides interactive measurement. The 3D model and measuring tools can be freely shifted and rotated in all planes. Results: The average length of the scapulas was 209.58 ± 26.72 mm (left) and 223.68 ± 47.74 mm (right); width was 124.03 ± 13.28 mm (left) and 141.44 ± 27.78 mm (right); and volume was 121.38 ± 12.02 ml (left) and 130.24 ± 20.86 ml (right). The glenoid dimensions were 34.34 ± 5.62 mm (left) and 36.44 ± 7.36 mm (right) (anteroposterior); and 49.16 ± 7.68 mm (left), 51.46 ± 10.07 mm (right) (superoinferior). For all average values, scapulas from male controls were significantly larger than those from females, and right sides were larger than left sides (p < 0.05). The glenoid version was nearly the same for male/female and left/right (left=9.02 ± 3.89± retroversion; right=8.26 ± 3.72° retroversion) (p ≥ 0.05). Conclusion: The 3D measurement of scapula morphology compared with geometry of the glenohumeral joint leads to a more precise planning of shoulder surgery. As new shoulder prostheses are intended to reconstruct the normal anatomy as closely as possible, such exact 3D measurements may be used for optimization.

Synthesis and inhibitory properties of a thiomethylmercuric sialic acid with application to the X-ray structure determination of 9-O-acetylsialic acid esterase from influenza C virus

Abstract 2-α-Thiomethylmercuryl 9-acetamido-9-deoxy-sialoside was prepared and found to inhibit the 9-O-acetylsialic acid esterase from influenza C virus in a competitive manner with a K i of 4.2±0.5 mM. The inhibitor is being used in the X-ray determination of the crystal structure of the esterase.

Design rationale for customized TKA: a new idea or revisiting the past?

Today’s most basic and important total knee replacement design concepts arose out of an earlier era in which 2 distinct approaches emerged, functional and anatomic. Functional approaches simplified knee kinetics, were easier to implant, and gained widespread popularity, in part, from their inventory control. Anatomic approaches were an attempt to recreate normal knee motion with low prosthetic contact stress. Historically, however, they became impractical to produce because of the cost of maintaining a wide variety of anatomic knee implants. New customized designs may return the anatomic design to favor due to several key features that borrow anatomic principles developed in the past, and improved with new ideas.

X-ray crystallographic determination of the ­structure of the influenza C virus haemagglutinin-esterase-fusion glycoprotein

The structure of the haemagglutinin‐esterase‐fusion (HEF) glycoprotein from influenza C virus has been determined to 3.2 Å resolution by X‐ray crystallography. A synthetic mercury‐containing esterase inhibitor and receptor analogue, 9‐acetamidosialic acid α‐thiomethylmercuryglycoside, was designed as the single isomorphous heavy‐atom derivative. The asymmetric unit of one crystal form (form I; P4322, a = b = 155.4, c = 414.4 Å) contained an HEF trimer. Six mercury sites identifying the three haemagglutination and three esterase sites were located by difference Patterson map analysis of a 6.5 Å resolution derivative data set. These positions defined the molecular threefold‐symmetry axis of the HEF trimer. A molecular envelope was defined by averaging a 7.0 Å resolution electron‐density map, phased by single isomorphous replacement (SIR), about the non‐crystallographic threefold‐symmetry axis. Iterative non‐crystallographic symmetry averaging in real space, solvent flattening and histogram matching were used to extend the phases to 3.5 Å resolution. Molecular replacement of the model into a second crystal form (form II; P43212, a = b = 217.4, c = 421.4 Å) containing two HEF trimers per asymmetric unit permitted iterative ninefold averaging of the electron density. The 3.5 Å electron‐density map allowed an unambiguous tracing of the polypeptide chain and identification of N‐linked carbohydrates. The model has been refined by least squares to 3.2 Å resolution (R free = 26.7%).