9.1 Historical reflections
The processing of bone tissue is as old as mankind itself. Initially, there was a need to process bones of captured animals with the aid of stone tools, such as hand wedges, to enable cutting and subsequent consumption. In the Paleolithic period, the bones of hunted prey animals were processed and used as material for the manufacture of tools and weapons.
The first references to the processing of human bone tissue with therapeutic intent date back to the 7th millennium BC. Archaeological finds prove that skull openings comparable to a borehole trepanation were made at this time. Since various found skull bones show clear signs of bone healing, it must be assumed that these procedures were regularly survived by the “patients” even then.1 As causes for these trepanations, medical-therapeutic indications (eg, in case of trauma or tumor for the treatment of a cerebral pressure symptomatology), magic-therapeutic actions for the improvement of a cerebral symptomatology (eg, epilepsy), which was understood as a supernatural phenomenon, or magic-ritual reasons come into consideration. However, magical-ritual acts were mostly performed post-mortem (Fig 9-1).2
Figs 9-1a and 9-1b Skull with healed trepanation wound and tools for performing trepanations.
Later, the processing of bone as part of therapeutic and surgical measures became the domain of field scissors, which were used to treat injuries from warlike actions. The oldest instruments used for this purpose date back to Roman times.3 Tools that had proven themselves in other fields, such as the saw known from woodworking, were adapted, and found use in performing amputations and similar procedures. In addition, there were various drills, scrapers, knives, and chisels that were used to process bone tissue.
After surgery emerged as an independent medical discipline in the 18th century, a variety of new surgical instruments quickly developed. The discovery of new materials and the invention of new drive systems led to constant further development, so that today surgeons have a wide range of reliable and powerful instruments at their disposal for working on bone tissue. There is now the possibility of sawing, drilling, or fracturing the bone in a controlled manner using a hammer and chisel. However, the mechanical principles involved have not fundamentally changed over the past nearly 9,000 years: the surgeon induces biomechanical forces on the surface of the bone that exceed the hardness of the tissue, allowing the instrument to penetrate the bone. By destroying the tissue, bone fragments can be separated from each other.
9.2 Instruments for working the bone in dysgnathic surgery procedures
In surgery to correct positional anomalies of the jaw bones, rotating drills or milling cutters, oscillating saws, and chisels are classically used (Fig 9-2). Usually, the first step is to create predetermined breaking points in the bone with saws or burs and then to fracture the bone in a controlled manner with chisels and hammers.4
Fig 9-2 Mechanical tools for bone surgery: reciprocating saw (1), rose burr (2), and piezoelectric osteotome (3).
Piezoelectrically operated devices have been used for some years, especially in craniomaxillofacial surgery. The advantage of this technology is the selective cutting of bone tissue while sparing adjacent soft tissue.5 Some studies have shown that the use of piezoelectric osteotomes can reduce damage to sensitive anatomical structures, such as the mandibular nerve.6–8
Piezoelectric osteotomy is also regularly used to perform osteotomies in the maxillary region (Fig 9-3
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