dos.4. Delivery regarding HVLA-SM
The device was comprised of an electronic feedback control system, a motor, and a lever arm attached to the motor’s shaft (Aurora Scientific, Lever System Model 310)puter-controlled rotation of the motor’s shaft rotated the lever arm. The lever arm was attached to a custom built rotary-to-linear converter which in turn was attached to a manipulandum (see Figure 1) that contacted the back of the cat. The rotary-to-linear converter consisted of a polycarbonate block machined with a narrow slot that received the end of the motor’s lever arm and held two parallel guide posts passing through linear bearings in an adjacent fixed bearing block. The manipulandum consisted of a thin titanium rod (0.2 cm diameter ? 12 cm long) secured at one end into the rotary-to-linear converter and inserted at the other end into a small plexiglass tip. The tip made direct contact with skin overlying the Lsix spinous process. The converter transformed the lever arm’s rotary motion to linear motion of the manipulandum.
With the cat lying prone, HVLA-SMs were applied at the L6 spinous process in a vertical direction, that is, toward ventralward from the back of the cat. The electronic feedback control system allowed the motor to control either the force applied at the end of the lever arm (force control) or the distance traveled by the end of the lever arm (displacement control). Forces and displacements during the HVLA-SM were simultaneously measured at outputs from the control system.
The fresh physical reputation (amplitude instead of go out) of a medically delivered HVLA-SM is going to be roughly portrayed from the shape of a right up-front side down page “V” [24–26]. Brand new HVLA-SM’s push stage is illustrated of the rising arm of one’s “?” (find HVLA-Text messages when you look at the Contour dos). Given that found within the Contour dos, the fresh new straight level signifies push amplitude (mentioned because used force or displacement) and its own horizontal duration is short for push years (mentioned within the milliseconds). Achieving the thrust amplitude is actually always managed linearly that’s, in force handle the fresh new pushy push increased within a steady rate, and also in displacement manage the brand new pushy displacement enhanced within a steady speed.
An essential objective for the fresh options would be to keeps bodily contact amongst the cat’s as well as the fresh new manipulandum become exactly like the fresh real get in touch with between a beneficial clinician’s hands together with lumbar lower back regarding an individual
One way we did this was to have the manipulandum’s tip make direct contact with the intact skin overlying the L6 spinous process as previously described. This improved upon earlier studies where the skin had been cut and toothed forceps clamped directly onto the spinous process [10, 11]. The second way was to customize the manipulandum’s plexiglass tip by scaling its contact area with the skin to that used clinically in the lumbar spine. In the human, peak thrust forces are distributed over a relatively circular area between 350 and 1480 mm 2 when the pisiform bone is used to apply an HVLA-SM. We scaled this area but not its shape to the cat using a ratio of eris heights (from caudal to cranial tip of the articular processes) between the cat and human lumbar vertebra. We took direct measurements from cat and human lumbar specimens. The cat L6 vertebra is 23 mm in height and the comparable human vertebra (L4) is 43 mm. The 0.53 ratio was slightly reduced to 0.45. The final scaled surface area was 70 mm 2 . The tip’s shape was rectangular (7 mm ? 10 mm) with a narrow channel (5 mm wide ? 2 mm deep) designed to cradle the sides of the spinous process and help prevent lateral slippage during the HVLA-SM.
