The transpedicular fixation was initially developed by Dr Magerl in 1977. Originally it was used for external fixation of the lower thoracic and lumbar spine. The fixation device, consisting of two transverse bars and three threaded rods with triangular locking plates, provided rigid stability. The system could be applied in distraction, compression, or in a neutral mode. Screws could be placed by either open or closed technique. Magerl found the stability of the system was enhanced by preloading the Schanz screws in distraction and by adding translaminar screws through the facet joints.
How and when was the Dick´s system born?
Following Magerl’s initial description of external fourpoint fixation with Schantz screws, Dick developed in 1985 a similar internal device, which he called the “fixateur
interne”.This system also used 5 mm Schantz screws to create long lever arms to facilitate manual reduction. The screws were connected to the 7 mm threaded longitudinal rods by clamps which were mobile in all directions allowing compression, distraction, kyphosis, lordosis, and rotation. Biomechanical testing with anterior bending moments demonstrated its increased rigidity in comparison to Magerl’s external fixator.
What were its advantages?
The Dick system had several advantages:
1.- Stability: The Fixateur interne was stable by itself. No second point of bony support was required. The instrumentation was restricted to the immediately adjacent vertebra above and below the fracture, and it did not matter if the posterior elements were fractured, or the ligaments were torned.
2.- Controlled reduction:Its second advantage besides it’s shortness, was the long lever-arms of the Schanz screws. These handles allowed a direct and forceful adjustment of a single vertebra in any desired direction. If present, gross luxations of vertebrae were reduced first by hand with the help of the Schanz screws, then the connecting rods were applied. Next, the vertebral body was spreaded up anteriorly by posteriorly compressing together the ends of the lever-arms. With this manoeuvre, the kyphotic deformity was reduced, then the hinges were locked. In the third stage of the technique, the original height of the fractured vertebra could be restored by longitudinal distraction on the threaded rod. With this maneuver, fragments of the posterior wall were reduced if the posterior longitudinal ligament was intact.At the end of the procedure, when the instrumentation has been completed and the nuts were secured, the protruding parts of the Schanz screws were cut with a Harrington cutter.
3.-Indications: It could also be used in all fractures even after laminectomy or if there was a traumatic destruction of all the posterior elements. The position of the Schanz screws in such patients was even easier because the remnants of the pedicles adjacent to the dura could be seen directly.
How did this system evolve?
The Dick system evolved into the USS Fractures which, based on the principles of the AO Foundation, became very popular in the 1990s for the treatment of vertebral fractures.With the advent of MIS systems, Synthes launched a minimally invasive option. However, despite its many advantages, it is rarely used today. It is true that kyphoplasty and the evolution of pedicle systems have made this system somewhat outdated. In any case, the Dick system and the USS Fractures have successfully treated thousands of fractures worldwide. It is without a doubt, a system to remember.
Below I attach the video and the surgical techniques of the USS Fractures:
What do you think about this system? Your comments are welcome!
References: The History of Vertebral Screw and Pedicle Screw Fixation (Mark B. Kabins, M.D.*James N. Weinstein, D.O.). Spine Diagnostic and Treatment Center Department of Orthopaedic Surgery University of Iowa Hospitals and Clinics
I remember Dr. Steffee talking about this early in my training