Insertion force measurement of cervical traction tongs: a biomechanical study.

OBJECTIVES: To measure the insertion forces for various cervical traction tong pins and the force required to penetrate cadaveric skull specimens. DESIGN: Cadaveric study testing tong pin forces. METHODS: Insertion force and pin indicator displacement were measured in three tongs from each of three manufacturers (PMT, Depuy Ace, Gardner-Wells) after tightening pins per the manufacturer's recommendations and beyond. The force required for skull penetration was measured by driving each pin into cadaveric temporal specimens until the specimen failed or was penetrated. RESULTS: Forces generated at the recommended pin settings were: PMT, 141 +/- 12 newtons; Ace, 0 +/- 0 newtons; Gardner-Wells, 132 +/- 9 newtons. The Ace tong required 1.0-millimeter indicator protrusion beyond manufacturer's recommended setting before generating clinically significant forces (120 +/- 8 newtons). Unlike the PMT and Ace pins, overtightening of the Gardner-Wells pins (by as little as 0.3 mm beyond recommended indicator displacement) resulted in substantially larger pin force (>448 newtons). Average failure loads of the temporal bone specimens were: PMT, 721 +/- 298 newtons; Ace, 636 +/- 351 newtons; Gardner-Wells, 965 +/- 227 newtons. CONCLUSIONS: Although pin forces generated at the recommended end point for PMT and Gardner-Wells tongs appear safe, insufficient force was generated for Ace tongs. Furthermore, overtightening of the Gardner-Wells pins generated loads in excess of those that may be required to penetrate the skull.

Spectinomycin resistant gonococci.

A study was conducted examining the properties of 10 clinical isolates of spectinomycin resistant gonococci from patients attending clinics at St Mary's and St Thomas's Hospitals, London. All of the isolates produced beta-lactamase and contained plasmids of 2.6, 4.4, and 24.5 megadaltons and required proline for growth. None produced aminoglycoside modifying enzymes. Resistance to spectinomycin was transferred from some of the isolates by transformation but at a much lower frequency than resistance to streptomycin. The isolates from St Mary's Hospital were detected after therapy with spectinomycin, whereas those from St Thomas's Hospital were not. Four recent non-beta-lactamase producing gonococci isolated at St Mary's Hospital and two isolated at St Thomas's Hospital also were not related to use of spectinomycin.