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→Clinical use of bone segment navigation: The systems, which were used by Cutting and Watzinger do not meet the criteria of bone segment navigation (see first paragraph), since they still use artificial reference markers instead of natural reference surfaces and achieve only an accuracy of 2 - 4 mm. |
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{{Short description|Surgical method for positioning bone fragments in fractures}}
'''Bone segment navigation''' is a surgical method used to find the anatomical position of displaced bone fragments in fractures, or to position surgically created fragments in craniofacial surgery. Such fragments are later fixed in position by [[osteosynthesis]]. It has been developed for use in [[craniofacial]] and [[oral and maxillofacial surgery]].▼
▲'''Bone segment navigation''' is a surgical method used to find the anatomical position of displaced bone fragments in [[Bone fracture|fractures]], or to position surgically created fragments in [[craniofacial surgery]]. Such fragments are later fixed in position by [[osteosynthesis]]. It has been developed for use in
After an accident or injury, a fracture can be produced and the resulting bony fragments can be displaced. In the oral and maxillofacial area, such a displacement could have a major effect both on facial aesthetics and organ function: a fracture occurring in a bone that delimits the [[orbit (anatomy)|orbit]] can lead to [[diplopia]]; a [[Human mandible|mandibula]]r fracture can induce significant modifications of the [[occlusion (dentistry)|dental occlusion]]; in the same manner, a skull ([[neurocranium]]) fracture can produce an increased [[intracranial pressure]].{{cn}}▼
Bone segment navigation is a patented <ref>Marmulla R (inventor), Carl Zeiss (submitter): System and method for bone segment navigation. United States Patent 6.241.735, 2001.</ref><ref>Marmulla R and Lüth T: Method and device for instrument, bone segment, tissue, and organ navigation, United States Patent 7.079.885, 2006</ref> surgical procedure, using a frameless and markerless registration technique. It uses for the first time natural registration surfaces instead of single artificial x-ray visible markers, in order to achieve a higher precision (1 mm and better).<ref>Marmulla R, Niederdellmann H: Computer-assisted Bone Segment Navigation. In: Journal of Cranio-Maxillo-Facial Surgery. 1998; 26, S. 347–359.</ref> Previous methods of Cutting and Watzinger do not meet the criteria of bone segment navigation.<ref> Marmulla R: Knochensegmentnavigation. Quintessenz-Verlag, Berlin 2000, ISBN 3-87652-869-0.</ref>
▲After an accident or injury, a fracture can be produced and the resulting bony fragments can be displaced. In the oral and maxillofacial area, such a displacement could have a major effect both on facial aesthetics and organ function: a fracture occurring in a bone that delimits the [[orbit (anatomy)|orbit]] can lead to [[diplopia]]; a [[Human mandible|mandibula]]r fracture can induce significant modifications of the [[occlusion (dentistry)|dental occlusion]]; in the same manner, a skull ([[neurocranium]]) fracture can produce an increased [[intracranial pressure]].{{cn|date=January 2022}}
In severe congenital malformations of the facial skeleton surgical creation of usually multiple<ref>{{Cite journal|last=Obwegeser|first=HL|date=1969|title=Surgical correction of small or retrodisplaced maxillae. The "dish-face" deformity.|journal=Plast Reconstr Surg|volume=43|issue=4|pages=351–65|doi=10.1097/00006534-196904000-00003|pmid=5776622|s2cid=41856712}}</ref><ref>{{Cite book|title=Craniofacial Surgery 3|last1=Cutting|first1=C|last2=Grayson|first2=B|last3=Bookstein|first3=F|last4=Kim|first4=H|last5=McCarthy|first5=J|publisher=Monduzzi Editore|year=1991|isbn=9788832300000|editor-last=Caronni|editor-first=EP|___location=Bologna|chapter=The case for multiple cranio-maxillary osteotomies in Crouzon's disease.}}</ref> bone segments is required with precise movement of these segments to produce a more normal face.
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== Materials and devices needed for preoperative planning and simulation ==
The osteotomies performed in [[orthognathic surgery]] are classically planned on cast models of the tooth-bearing jaws, fixed in an [[articulator]]. For [[edentulous]] patients, the surgical planning may be made by using [[stereolithography|stereolithographic models]]. These tridimensional models are then cut along the planned
Since the 1990s, modern techniques of presurgical planning were developed – allowing the surgeon to plan and simulate the osteotomy in a virtual environment, based on a preoperative [[computed tomography|CT]] or [[MRI]]; this procedure reduces the costs and the duration of creating, positioning, cutting, repositioning and refixing the cast models for each patient.
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The usefulness of the preoperative planning, no matter how accurate, depends on the accuracy of the reproduction of the simulated [[osteotomy]] in the surgical field. The transfer of the planning was mainly based on the surgeon's visual skills. Different guiding headframes were further developed to mechanically guide bone fragment repositioning. {{citation needed|date=October 2018}}
Such a headframe is attached to the patient's head, during CT or MRI, and surgery. There are certain difficulties in using this device. First, exact reproducibility of the headframe position on the patient's head is needed, both during CT or MRI registration, and during surgery. The headframe is relatively uncomfortable to wear, and very difficult or even impossible to use on small children, who can be uncooperative during medical procedures. For this reason headframes have been abandoned in favor of frameless stereotaxy of the mobilized segments with respect to the skull base. Intraoperative registration of the patient's anatomy with the computer model is done such that pre-CT placement of fiducial points is not necessary.{{cn|date=January 2022}}
[[Image:SSNimOP.jpg|thumb|Using the [[Surgical Segment Navigator|SSN]] in the operating theatre; 1=IR receiver, 2 and 4=IR Reference devices, 3=SSN-Workstation]]
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Initial bone fragment positioning efforts using an electro-magnetic system were abandoned due to the need for an environment without ferrous metals.<ref>{{Cite journal|last1=Cutting|first1=C|last2=Grayson|first2=B|last3=Kim|first3=H|date=1990|title=Precision multi-segment bone positioning using computer aided methods in craniofacial surgical procedures.|journal=Proc. IEEE Eng. Med. Biol. Soc.|volume=12|pages=1926–7}}</ref> In 1991 Taylor at IBM working in collaboration with the craniofacial surgery team at New York University developed a bone fragment tracking system based on an [[Infrared|infrared (IR)]] camera and IR [[transmitters]] attached to the skull.<ref>{{Cite book|title=A Model-Based Optimal Planning and Execution System with Active Sensing and Passive Manipulation for Augmentation of Human Precision in Computer-Integrated Surgery|last1=Taylor|first1=RH|last2=Cutting|first2=C|last3=Kim|first3=Y|display-authors=etal|work=Proceedings International Symposium on Experimental Robotics.|publisher=Springer-Verlag|year=1991|___location=Toulouse, France}}</ref><ref>{{Cite journal|last1=Taylor|first1=RH|last2=Paul|first2=H|last3=Cutting|first3=C|display-authors=etal|date=1992|title=Augmentation of Human Precision in Computer Integrated Surgery.|journal=Innovation et Technologie en Biologie et Medicine|volume=13|issue=4|pages=450–68}}</ref> This system was patented by IBM in 1994.<ref>{{Cite book|title=Signaling device and method for monitoring positions in a surgical operation.|last1=Taylor|first1=R|last2=Kim|first2=Y (inventors)|publisher=United States Patent 5,279,309|year=1994|___location=Ossining, NY}}</ref> At least three IR transmitters are attached in the [[neurocranium]] area to compensate the movements of the patient's head. There are three or more IR transmitters are attached to the bones where the osteotomy and bone repositioning is about to be performed onto. The [[Three-dimensional space|3D]] position of each transmitter is measured by the IR camera, using the same principle as in [[satellite navigation]]. A computer workstation is constantly visualizing the actual position of the bone fragments, compared with the predetermined position, and also makes real-time spatial determinations of the free-moving bony segments resulting from the osteotomy.
Thus, fragments can be very accurately positioned into the target position, predetermined by surgical simulation. More recently a similar system, the [[Surgical Segment Navigator]] (SSN), was developed in 1997 at the [[University of Regensburg|University of Regensburg, Germany]], with the support of the [[Carl Zeiss AG|Carl Zeiss Company]].<ref name=":0">Marmulla R, Niederdellmann H: ''Computer-assisted Bone Segment Navigation'', J Craniomaxillofac Surg 26: 347-359, 1998</ref>
== References ==
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