Chapter 7 - Veterinary Instrumentation

7 TRAUMA IMPLANTS & INSTRUMENTSLocking ScrewsThe angular security of locking plate systems depends on a rigid interfacebetween screw and plate. This is achieved by the use of interlockingthreads.Threaded systems are the most common. The modulus of bone andstainless steel differs greatly and the ideal screw thread for one will not suitthe other. Stainless steel demands fine threads whereas bone needs arelatively coarse thread. If we use a fine thread in the plate and a coarsethread in the bone, when the head of screw engages the plate, the screwmoving faster through the bone than the plate would have the effect ofpulling the plate towards the bone. This is exactly what we do not want.Some systems compromise by using the same thread in both screw headand bone plate.At Veterinary Instrumentation and in the industry Standard Locking Screwthe problem is solved by some ingenious engineering. The threads on thehead of our screws are fine as required but have a twin start. The threadstaper down the head as a double helix. The pitch (the distance betweenthe tips of the threads) of each individual fine thread is the same as thethreads on the bone screw but because of the double helix the number ofthreads per millimeter of locking thread is double that of the bone screwgiving the fine threads required for metal on metal. The screw movesthrough the bone at the same rate as it moves through the platemaintaining the relative positions of both bone fragment and plate.There is an additional benefit of the double helix. As the screw headapproaches the plate a single start thread may have to wait 360 degreerotation before the threads start to engage. In the 3.5 screw this mightmean that the plate is pushed around one millimeter before the head of thescrew engages. With a twin start thread the screw head will engage within180 degrees of contact.Locking Screw SetsAvailable with either Hex (3.5mm only) or Star Drive Head. Setsdiscounted by over 5% from component price.3.5 Set includes 3 x 12-20mm, 4 x 22-26mm, 5x 28-40mm, 4x 42-50mm,3x 52-58mm Locking Screws and 5 Locking Plugs.2.7 Set includes 3 x 6-8mm, 4 x 10-16mm, 5x 18-28mm, 4x 30-32mm,3x 34-40mm Locking Screws and 5 Locking Plugs.2.4 Set includes 3 x 6-8mm, 4 x 10-16mm, 5x 18-28mm, 4x 30-32mm,3x 34-40mm Locking Screws and 5 Locking Plugs.LOCKING SCREW SETSLS35KIT 3.5 Hex Drive Locking Screw Set £1,495.00LS35STARKIT 3.5 Star Drive Locking Screw Set £1,495.00LS27STARKIT 2.7 Star Drive Locking Screw Set £995.00LS24STARKIT 2.4 Star Drive Locking Screw Set £995.00LS20STARKIT 2.0 Star Drive Locking Screw Set £995.00Locking Screws - Hex DriveLocking Screw Hex Drive 3.5mmVI Screws are an exact fit for Standard Locking Plates but utilise theconventional Hex Drive rather than a Star Drive. See overleaf for StarDrive.LOCKING SCREW 3.5mm USE 2.7mm PILOT PLUS DRILL SLEEVELS3510 Locking 3.5 Screw Hex Drive 10mm £12.50LS3512 Locking 3.5 Screw Hex Drive 12mm £12.50LS3514 Locking 3.5 Screw Hex Drive 14mm £13.25LS3516 Locking 3.5 Screw Hex Drive 16mm £13.25LS3518 Locking 3.5 Screw Hex Drive 18mm £13.75LS3520 Locking 3.5 Screw Hex Drive 20mm £13.75LS3522 Locking 3.5 Screw Hex Drive 22mm £14.50LS3524 Locking 3.5 Screw Hex Drive 24mm £14.75LS3526 Locking 3.5 Screw Hex Drive 26mm £15.00LS3528 Locking 3.5 Screw Hex Drive 28mm £15.25LS3530 Locking 3.5 Screw Hex Drive 30mm £15.75LS3532 Locking 3.5 Screw Hex Drive 32mm £16.00LS3534 Locking 3.5 Screw Hex Drive 34mm £16.25LS3536 Locking 3.5 Screw Hex Drive 36mm £16.50LS3538 Locking 3.5 Screw Hex Drive 38mm £16.75LS3540 Locking 3.5 Screw Hex Drive 40mm £17.00LS3542 Locking 3.5 Screw Hex Drive 42mm £17.25LS3544 Locking 3.5 Screw Hex Drive 44mm £17.50LS3545 Locking 3.5 Screw Hex Drive 45mm £17.50LS3546 Locking 3.5 Screw Hex Drive 46mm £17.75LS3548 Locking 3.5 Screw Hex Drive 48mm £18.00LS3550 Locking 3.5 Screw Hex Drive 50mm £18.50LS3552 Locking 3.5 Screw Hex Drive 52mm £19.00LS3554 Locking 3.5 Screw Hex Drive 54mm £19.50LS3555 Locking 3.5 Screw Hex Drive 55mm £19.75LS3556 Locking 3.5 Screw Hex Drive 56mm £20.00LS3558 Locking 3.5 Screw Hex Drive 58mm £21.00LS3560 Locking 3.5 Screw Hex Drive 60mm £22.00LSDG35 3.5 Locking Screw Drill Guide £52.50H090104 2.7mm Pilot Drill £20.50SHLS35 3.5 Locking Screwbox £135.00Locking PlugLOCKING PLUG HEX DRIVE 2.7/3.5mmIMPROVEDDESIGNUse to protect lockingholes during contouring.LSP35 Locking Plug for LS35** and LS2735** Screws £7.50188