Rapid Prototyping Casebook
Edited by JA McDonald & CJ Ryall & DI Wimpenny
Available through Professional Engineering Publishing - for link please click the horse. ISBN:1860580769
For further details...
The Rapid Prototyping & Tooling Centre, ATC, University of Warwick, Coventry. CV4 7AL
Tel: 01203 524722/572991
Fax: 01203 524878
Engineering Assisted Surgery - EAS
New developments in engineering, used for the first time in oral and maxillofacial surgery, permit the manufacture of accurate anatomical biomodels of the skeleton from CAT scans (rapid prototyping). Biomodels have been used in diagnosis, treatment planning in conjunction with existing clinical interventions. EAS technology lends itself evolution of new treatments and clinical procedures, previously not possible has been the catalyst for the design / manufacture of customized titanium implants for the single staged reconstruction of the orofacial region using very simple cost effective interventions. These may carried out without surgery from a second surgical site, and obviate the necessity for complex flap surgery.
Implants are inserted with relatively atraumatic surgical protocols permitting, for the first time, a single staged orofacial reconstruction, including the dentition.
Engineering Assisted Surgery - Oral & Maxillofacial Surgery
Within oral and maxillofacial surgery, EAS has special relevance in the planning and treatment of:
|Skull Base Surgery|
Engineering Assisted Surgery - Case Planning
There are applications in many surgical disciplines, especially orthopaedics, with respect to:
|Customized Joint Replacement|
EAS - New Standards in Clinical Practice
EAS technology permits an accuracy of diagnosis, treatment planning and design and manufacture of
customized implants to an accuracy previously not possible. Applications pertaining
to medicolegal practice, the demonstration of personal injury and audit of
outcomes, herald new standards in duty of care, and there are applications in
high risk procedures where precision is of primary importance, for example in
spinal surgery, with the use of customised cutting and position jigs.
It is advocated that as this technology is development and mastered, reappraisal of the principles of surgery in general are warranted, especially in relation to the incredible accuracy that is possible using these techniques, and the potential of the elimination of operator error.
EAS - Resource Implications
Experience in oral and maxillofacial surgery illustrate important resource implications
relating to the utilisation of:
|Single surgical teams for EAS interventions|
|Single staged surgery|
|Reduced surgical trauma|
|Reduction in the use / morbidity of donor sites|
|Projections of reduced morbidity|
|Projections of reduced perioperative mortality|
|Reduction in critical care use|
|Projections of reduced hospitalisation times|
|Reduction in cost of surgical interventions|
EAS - Clinical Implications
It is advocated that:
|accuracy of diagnosis is enhanced|
|accurate surgical planning is facilitated|
|translation of plan into patient is facilitated|
|single site / single staged surgery is possible with non-mutilating reconstructions|
|excellent aesthetics / immediate dental rehabilitation possible.|
|no tumour recurrence possible in a custom titanium jaw prosthesis|
|plans using orally exposed implants not dependent on intraoral wound healing|
|complications - implant salvage vs. free flap loss|
|conventional surgery held in reserve|
Customised Orbital Implant with Cutting and Positional Jigs
|The introductions of this technology has far reaching implications for surgery in general and further
development and research is advocated with respect to:
|implant biotechnology and design|
|treatment planning and protocols|
|morbidity and mortality studies|
|hospitalisation / rehabilitation times|
|outcomes; cost savings|
Indications for Engineering Assisted Surgery
EAS has global relevance to many specialties especially maxillofacial surgery and orthopaedics:
|To promote the accuracy of planning and delivery of surgical treatment plans.|
|To facilitate the transfer of the surgical plan from biomodel to patient.|
|To replicate bone resection cuts exactly at operation with customized cutting jigs.|
|To accurately determine positions of the bones with position jigs.|
|To eliminate operator error|
|To facilitate single stage reconstructive surgery.|
|To facilitate single site surgery.|
|To reduce surgical trauma.|
|To reduce the dependency on post operative critical care.|
|To guarantee quality of outcome related to technique|
|To facilitate audit of outcomes.|
|To promote the principles of clinical effectiveness and governance.|
Applications of Engineering Assisted Surgery
|Face of a Medical Miracle|
Author: David Moller © Photograph by permission of Reader's Digest UK Edition - August 1st 2000
Experience of EAS applications within oral and maxillofacial surgery include:
|Surgical planning of cases|
|Customised implant design and manufacture|
|Reconstruction, customised implants - no bone grafting required|
Facilitation of Existing Surgical Interventions
Major (cranio) facial trauma, especially involving the midface, is technically demanding, and involves very long surgical procedures that are not in the interest of patient nor surgeon and operative performance. EAS techniques facilitate the delivery of both current surgical techniques and new evolving procedures. In established practice, the anatomy of the fracture can be analysed and fractured parts can be repositioned on a biomodel preoperatively. Titanium bone plates can be bent to the correct shape and fitted to the model. The reassembled biomodel can be sterilised as a single unit.
New innovative applications are of benefit in old and malunited fractures. Cutting and position jigs can be manufactured. These remove the parameter of operator error, and facilitate transfer of the plan from model to patient. Defects in the skeleton can be more accurately reconstructed, than is possible with bone grafting techniques, with customized implants e.g. in major orbital injuries. The use of such implants obviates the requirement for second site surgery, increased surgical trauma, and potential complications from a chosen donor site. Surgery time is significantly reduced with overall cost reduction and enhanced outcome.
Head and Neck Reconstructive Surgery
Midface / Nasal Reconstruction
Head and Neck Reconstruction commonly involves long and complex procedures with an outcome dependent on the skill and judgement of multidisciplinary surgical teams. Problems exist with respect to the translation of the proposed surgical plan into the patient at operation, which are currently carried out by “naked eye variables”. Procedures as long as 18 hours are not uncommon. Referral pathways to under funded national centres of excellence in the European Union have resulted in services that do not always have the resources to deliver the reconstructive component for optimum outcome (personal communication) and the cost of treatment is generally unknown. EAS techniques potentially offer the opportunity to address these potential problems by reducing treatment time, surgical trauma and overall cost, with enhanced outcomes.
Reduction in the number of surgical procedures to achieve the desired outcome is possible in multistaged treatment plans; it is not unknown for nasal reconstruction to involve many dozens of procedures; this could potentially be reduced to two procedures with EAS techniques.
Technical problems with respect to mandibular reconstruction are not uncommon and include:
|Exposure of the osseous component of repair|
|Ultimate loss of the osseous repair|
This appears to be more likely to occur after two years, and is more common in those patients who have had postoperative radiotherapy. Raveh1-3 has indicated that skin ulceration may be reduced by fixing titanium reconstruction plates on the lingual (tongue) side of the mandible forming a bridge across a mandibular resection, so that any ulceration preferentially occurs into the oral cavity, sparing the external skin and the formation of a fistula. However this solution is associated with metal fatigue and plate fracture, to the extent that this technique has been abandoned in favour of free flap surgery.
The manufacture of a customized mandible, which fits exactly into the resection defect, may overcome the problems encountered by Raveh. Such a device attached to a reconstruction bone plate resists the flexion, extension, and lateral forces that come to play on a plate bridging a osseous gap, by virtue of its close association with the resection cuts. This example has been in place and functioning for four years. Prototypes are currently being developed to incorporate this concept with fixation of the osseous attachments to the lingual side of the mandible.
|Midface / Nose|
|Failed Cleft Cases|
The treatment of congenital and acquired facial deformity becomes possible with a predictable outcome with EAS planning techniques +/- customized implants. Long complex surgical procedures using reconstructive techniques, that have no association with the creation of normal anatomical contour and function, can be replaced by simple,shorter and less traumatic procedures, with the creation of normal anatomical contour, with a greater margin of safety.
The use of customized veneer onlays (for example augmentation of the zygoma), converts a major osteotomy into a simple day case episode, with creation of normal facial contour. For those patients who have a history of failed reconstruction with intraoral wound breakdown, the use of customized implants, which do not require to be covered by soft tissue, offers a simple treatment solution with improved quality of life at reduced cost (e.g. persistent cleft palate)
Preprosthetic Oral Surgery
Atrophic Maxilla Customised Subperiosteal Implant
The atrophic maxilla commonly presents as a retention problem for the full upper denture. Patients with this condition have difficulty in eating and speaking and have a poor quality of life. Treatment commonly involves complex surgical procedures to provide an osseous reconstruction, with autologous bone and endosseous titanium implant techniques for overdenture attachment. Multiple interventions are required involving surgery at secondary donor sites. Success is dependent on primary intraoral healing to prevent infection / loss of bone graft, and promotion of implant osseointegration. Medical complications include deep venous thrombosis and pulmonary embolus, especially if bone is harvested from the iliac crest.
The use of veneer implants cantilevered from the zygomas converts this type of case into a single staged twenty-minute procedure, whose success is not dependent on primary intraoral wound healing with concomitant cost savings for the purchaser.
Atrophic Mandible Customised Subperiosteal Implant
EAS technology could be adapted for the very atrophic mandible, unsuitable for endosseous implant insertion, or distraction osteogenesis techniques, because of a risk of peroperative iatrogenic fracture of the mandible.
|a.||Craniofacial Surgical Planning +/- customised distracter|
|b.||Midface Surgical Planning +/- customised distracter|
|c.||Mandible Surgical Planning +/- customised distracter|
Disorders of facial growth may be treated by influencing bone growth across osteotomy cuts with distraction devices. These may be inserted with minimal access techniques wherever possible to reduce surgical trauma. Current techniques permit a choice of linear vector with great precision; this is important to maintain the correct end point occlusion. However it is possible with EAS techniques to produce customized devices with a changing vector; such devices would permit the growth of a new chin and floor of mouth after anterior mandibular resection without the use of any flap surgery, whilst maintaining the contour of the chin throughout the process of distraction.
|Restorative Dentistry, Orthodontics|
|Orthopaedics, trauma, deformity, customised arthroplasty|
|Head & Neck, ENT, Neurosurgery/Skull Base Surgery, Plastic Surgery General Surgery Cardiothoric,|
|Vascular Surgery General Medicine - Cardiology, Neurology, Gastroenterology Medicolegal / Forensic Medicine|
EAS - Implications for the Health care Industry
Click image for references
EAS technology has a wide application across many specialities24-167
trauma management24,96, congenital and acquired deformity53,93, customized prostheses38, limb prostheses for amputees, customised templates jigs, joint prostheses, spinal surgery94,131, hand/foot96, surgery, customized distraction osteogenesis.
diagnosis and treatment planning of cranial tumours, spinal surgery94,131, tauma136, stereotaxy134, nerve root pain, tumour resection; customised templates, jigs and implants62,136, customized distraction osteogenesis.
3. Maxillofacial Surgery2,6,101,107,108
photomorphanalysis (i.e. digital photographic planning and image prediction of outcome, audit and informed consent), cosmetic facial surgery, trauma, orbital surgery61,68,80, congenital/acquired deformity50-52,54,78-79,83-84,88 , cleft lip and palate100, tumour resection, colour stereolithography65,74 and tumour mapping1,65, reconstructive surgery, temporomandibular joint Surgery36, customized distraction osteogenesis1,39,55, customized templates jigs and implants67,70,72,103, oral rehabilitation45, diagnosis and treatment of facial and nerve root pain1
4. Orthodontics http://www.aligntech.com
The Invisalign System154-167 has centralised consultant orthodontic treatment planning services and the making orthodontic splints with digital transmission of data rapid prototyping and reverse engineering techniques. Diagnosis and treatment planning is carried out at a central unit and a series of splints are distributed to referring general dental practitioners who instigate treatment without the need for traditional orthodontic “braces”. Similar changes in working practice are to be expected in sister specialities as EAS evolves.
5. Craniofacial and Skull Base Surgery
photomorphanalysis, trauma, congenital118/acquired deformity35,71,73,81,86,97,112-114, tumour resection, reconstructive surgery62,63,129, customized templates, jigs and implants and prostheses37,59, customized distraction osteogenesis, cranial base surgery66,130,132.
6. Plastic and Reconstructive Surgery
photomorphanalysis, treatment planning of cosmetic surgery40, trauma, congenital/acquired deformity44,49,64,110, tumour resection, reconstructive surgery56, (head and neck surgery114-116, hand surgery, customized distraction osteogenesis, amputees) customized templates, jigs and implants, customized stencils for scar revision,
photomorphanalysis, treatment planning of cosmetic facial surgery, rhinoplasty, rhinometry34, trauma, congenital/acquired deformity, tumour resection, head, neck99 and laryngo-pharyngeal reconstructive surgery98, customized templates jigs and implants, scar revision, planning inner ear surgery92, petrous bone training workshops77,82.
8. Vascular Surgery
diagnosis and treatment planning, customised vascular stents conversion of major procedures to minimal access procedures ( eg management of aortic aneurysm) cerebrovascular biomodelling135
9. General Surgery
diagnosis and treatment planning, general surgery, cardiaothoracic surgery29-30,32, surgical oncology, urology31, obstetrics and gynaecology, paediatric surgery128,138, reconstructive surgery, biomaterial science.
10. Surgical Pathology
photomorphanalysis ( superimposition of clinical photographs on scans/biomodels) biomodel tumour mapping of hard and parenchymal tumours, identification of lymph node metastasis using microstereolithographic techniques148-153, in vitro biological testing systems, cerebrovascular biomodelling135, biomodels for surgical workshop training77,82.
11. Medicolegal Practice
medical reports have a major effect on expert evidence and are the basis for cross examination. EAS techniques, PowerPoint computer presentation, photomorphanalysis and biomodels, provide a hard copy description of personal injury and audit of outcomes. Medical negligence claims against the NHS currently run at £7billion/year. Improved outcomes with EAS will reduce this burden on resources. Forensic medicine applications have also been described43,75.
tumour mapping, radiotherapy planning, mask device manufacture
general medicine42 photomorphanalysis, parenchymal biomodels, cardiology48,85, neurology1, pharmacology and therapeutics, drug delivery systems, oncology133, cerebrovascular biomodelling135, tumour mapping, tissue engineering.
14. Ophthalmology - Artificial Vision
Please click icon for link to Dobelle website
New York, NY, January 18, 2000 - A biomedical engineering team today announced development of an artificial
vision system providing independent mobility to blind people. The system,
reflecting more than 30 years in development work by the Dobelle Institute
in New York City and its affiliates on Long Island and in Switzerland,
enables a totally blind person to achieve visual acuity of about 20/400, in
a narrow visual "tunnel."
The "Dobelle Eye," as described in the ASAIO Journal (the journal of American Society of Artificial Internal Organs) consists of a sub-miniature television camera and an ultrasonic distance sensor, both of which are mounted on a pair of eyeglasses. The sensors connect through a cable to a miniature computer, which is worn in a pack on a person's belt. After processing the video and distance signals, the computer uses sophisticated computer-imaging technology, including edge-detection algorithms to simplify the image eliminating "noise." The computer then triggers a second microcomputer that transmits pulses to an array of 68 platinum electrodes implanted on the surface of the brain's visual cortex. Bringing wires through the skin for two decades without discomfort or infection is one of many independent inventions that has made the new visual prosthesis possible.
Duty of Care - New Gold Standards
On the evidence presented to date there are early signs that the use of these techniques may herald new gold standards in “Duty of Care”. It is important that Society in general maintains a synchronous pace with technology and responsibly manages the introduction of innovative techniques and therapies, within the framework of Clinical Governance. The absence of appropriate funding for efficacious cost effective therapies has implications within international human rights law.
Head & Neck Surgery - Philosophical Considerations
Conventional reconstructive surgical techniques, involving composite microvascular free flap tissue transfer, are often carried out on elderly head and neck cancer patients, who have a poor prognosis. There is a perioperative morbidity and a mortality related to extensive surgical procedures involved in these repairs, and the possibility always exists of a compromised resection, in order to facilitate the reconstruction. Successful rehabilitation is likely to be a function of the preoperative American Joint Cancer Committee (AJCC) fitness score5, and associated surgical trauma of the resection/reconstruction procedure. If a functional result can be achieved by means other than additional reconstructive surgical trauma, parameters associated with major surgical procedures such as, perioperative, morbidity, mortality, and overall rehabilitation, may be favourably influenced.
The recurrence and mortality rates for advanced squamous carcinoma of the mouth is highest within the first two years of treatment6, and in order to maintain the dignity of existence, it is necessary to ensure that the reconstruction, can be maintained or easily salvaged, during this period, as the clinical condition deteriorates.
The "Mutilation" of Reconstruction
The osseous reconstruction of the Hemi-Mandible is associated with increased patient mutilation and the harvesting of tissue from donor sites.
Farag and McGurk17 have indicated that the risk of experiencing a complication increases two fold by each increasing magnitude of surgery, and that major procedures have 4 times the complication rate as minor operations". Both medical status and magnitude of surgery are independent risk factors for complicationss17. Morbidity, related to the donor and recipient sites17-21, is not uncommon, and total or partial flap loss has been reported as high as 28.6%18 for free fibula transfer, to 33%21, with respect to reconstruction of the extensive defects of the Head and Neck, in a series of 648 patients.
Perioperative mortality figures within the first 20 days20 have been reported as high as 9%, and is probably related to the metabolic response to surgical trauma.
The successful use of customised titanium implants without flap cover avoids the "mutilation" of conventional reconstructive techniques, and may influence the morbidity and mortality associated with major Head and Neck Reconstructive Surgery, especially in medically compromised patients. The technique has been successfully carried out in the Maxilla3 and Hemi-Mandible4 without any primary flap surgery whatsoever, and has permitted a single stage technique to be carried out with respect to reconstruction of the oral cavity and dental occlusion. At the time of writing, these 2 implants have been in situ for four and a half years without significant complication3-4.
The use of customised implants, combined with relative conservative reconstructive techniques with local flaps, is possible, and the salvage of customised implants has been demonstrated in medically compromised patients who may not have survived more major reconstructive procedures.
It is advocated that as this technology is development and mastered, reappraisal of the principles of reconstructive surgery in general are warranted, especially in relation to the introduction of engineering technology and the utilisation of customised titanium implants, without flap cover.
Outcome Update - Head and Neck Cancer 2000
Using simple rather than complex surgical techniques and customised implants where indicated, a highly statistically significant reduction in overall mortality related to tumour recurrence has been documented 3/43 (7%) in an independent audit for all patients treated between 1994-1998. This is to be compared to a national 2 year overall survival rate of around 50% in England and Wales.
Oral Cancer Mortality England and Wales 1991
Click flag for info
The reduction in mortality is so unexpectedly large that it requires further investigation within a Regional Cancer Centre and a larger referral base, in accordance with the principles of Clinical Governance.
This topic has been referred on the advice of the Department of Health to the National Institute for Clinical Excellence (NICE) for further consideration.