Fifth metacarpal instability and its effect on hamatometacarpal arthritis patterns-a cadaver study.

Osteoarthritis (OA) of the fifth carpometacarpal joint is a rare diagnosis with most cases occurring post-traumatically. The joint's ligamentous supports have not been described extensively; however we know that the volar and intermetacarpal ligaments acts as the primary stabilizers. The major deforming forces on this joint are the extensor carpi ulnaris (ECU) dorsally and the flexor carpi ulnaris volarly, via the pisimetacarpal ligament. The aim of this study was to determine how the different joint stabilizers contribute to fifth carpometacarpal joint stability and biomechanics. We also sought to describe the OA patterns affecting the fifth carpometacarpal joint. A study was performed on 10 embalmed cadavers. The fifth carpometacarpal joint was evaluated biomechanically through ECU traction and sequential transection of the joint stabilizers. Gross macroscopic evaluation of degenerative changes in the articular surface was conducted and graded on a scale of 0-3 (with 0 representing normal cartilage with no visible lesions). Biomechanical data were available from 18 specimens (10 right; 8 left) and arthritic patterns were available from all 20 specimens (10 right; 10 left). Based on the biomechanical data, the proximal and distal intermetacarpal ligaments were found to be major contributors to stability. The volar stabilizer was a minor contributor to stability and the dorsal stabilizer was a minimal contributor to stability. OA was present in 16/20 specimens (80%) with an average arthritis grade of 1.6 on the right hand and 1.0 on the left hand. The most common site of OA was the dorso-ulnar quadrant.

First results on angular distributions of thermal dileptons in nuclear collisions.

The NA60 experiment at the CERN Super Proton Synchrotron has studied dimuon production in 158A GeV In-In collisions. The strong excess of pairs above the known sources found in the complete mass region 0.2

Evidence for radial flow of thermal dileptons in high-energy nuclear collisions.

The NA60 experiment at the CERN SPS has studied low-mass dimuon production in 158A GeV In-In collisions. An excess of pairs above the known meson decays has been reported before. We now present precision results on the associated transverse momentum spectra. The slope parameter Teff extracted from the spectra rises with dimuon mass up to the rho, followed by a sudden decline above. While the initial rise is consistent with the expectations for radial flow of a hadronic decay source, the decline signals a transition to an emission source with much smaller flow. This may well represent the first direct evidence for thermal radiation of partonic origin in nuclear collisions.

J/psi production in Indium-Indium collisions at 158 GeV/nucleon.

The NA60 experiment studies muon pair production at the CERN Super Proton Synchrotron. In this Letter we report on a precision measurement of J/psi in In-In collisions. We have studied the J/psi centrality distribution, and we have compared it with the one expected if absorption in cold nuclear matter were the only active suppression mechanism. For collisions involving more than approximately 80 participant nucleons, we find that an extra suppression is present. This result is in qualitative agreement with previous Pb-Pb measurements by the NA50 experiment, but no theoretical explanation is presently able to coherently describe both results.

First measurement of the rho spectral function in high-energy nuclear collisions.

We report on a precision measurement of low-mass muon pairs in 158 AGeV indium-indium collisions at the CERN SPS. A significant excess of pairs is observed above the yield expected from neutral meson decays. The unprecedented sample size of 360,000 dimuons and the good mass resolution of about 2% allow us to isolate the excess by subtraction of the decay sources. The shape of the resulting mass spectrum is consistent with a dominant contribution from pi+pi- -->rho -->mu+mu- annihilation. The associated space-time averaged spectral function shows a strong broadening, but essentially no shift in mass. This may rule out theoretical models linking hadron masses directly to the chiral condensate.