The Melbourne Temporomandibular Total Joint Replacement System

Transcription

1 The Melbourne Temporomandibular Total Joint Replacement System

2 Device Description: The Melbourne TMJ Total Joint Replacement System is used to reconstruct a damaged or diseased temporomandibular joint that cannot be salvaged. The system comprises 2 components; the mandibular ramus metal alloy condyle and the polymer based glenoid fossa component, both of which are attached to the native bone by screw fixation. The Mandibular Ramus Component has been engineered to facilitate ease of surgical installation and supports greater surface contact during joint subluxation. The targeted screw placement and curved posterior boarder of the device aligns with the natural posterior border contour of the mandible reducing incorrect positioning and/or likelihood of nerve damage. The oversized condylar head maintains maximum contact during rotational and lateral movements more evenly distributing loads and strain. The Mandibular Ramus component manufactured via CNC or Additive Manufacturing processes and produced in Medical Grade 5 Titanium Alloy (ASTM F136/F ) to an accuracy of less than 50µm. The high polish condylar head is machine finished to an industry standard similar to that of other joint replacement systems. The Glenoid Fossa Component is a universal design capable of being positioned both left and right sides and can accommodate different mandible sizes and bone densities. This CNC machined device is produced in Medical Grade Ultra-High-Molecular-Weight-Polyethylene (ASTM F648) and the articular surface is polished to minimize wear and extend life expectancy. Intended Use and Indications: The Melbourne TMJ Total Joint Replacement System is an alloplastic medical implant device used to replace Category 5 Temporomandibular joints where none of the joint components are salvageable because of degenerative joint disease. The most suitable patients are those suffering from intolerable symptoms of pain and/or jaw joint dysfunction who have failed to adequately respond to other treatments. The main indications for total joint replacement surgery of the TMJ are: 1. Osteoarthritis 2. Other Degenerative joint conditions a. Posttraumatic Arthritis b. Rheumatoid Arthritis c. Psoriatic Arthritis 3. Revision Surgery a. Previously failed prosthetic joints b. Previously failed autogenous grafts c. Multiply operated TMJ 4. Developmental Abnormality a. Ankylosis b. Condylar hypoplasia c. Condylar resorption 5. Benign Tumours a. Osteochondroma b. Chondroma/Osteoma

3 Contraindications: The Melbourne TMJ total joint replacement system is not recommended for use in the following circumstances: 1. Active or chronic infection 2. Immunocompromised patients 3. Growing patients (skeletally immature) 4. Psychiatric patients 5. Chronic pain conditions (neuropathic) 6. Insufficient bone to support fossa and/or condylar components 7. Malignant disease 8. Terminal illness Precautions: This medical device is only intended to be used by medical practitioners who are adequately trained in the use of prosthetic TMJ total joint replacements through hands-on and educational course work. Adverse Effects: Listed below are the potential adverse effects that may occur following placement of the Melbourne TMJ total prosthetic joint replacement system: 1. Persistent facial swelling 2. Chronic pain 3. Loosening of one or more screws 4. Infection 5. Limited mouth opening 6. Ear problems including deafness 7. Jaw Dislocation 8. Facial nerve weakness 9. Facial tingling, numbness, hypersensitivity 10. Sensitive teeth 11. Numbness of lower lip, chin or tongue. 12. Altered bite (ie. malocclusion) malpositioning of prosthesis 13. Foreign body or allergic reaction to implant components 14. Heterotopic bone formation 15. Failure and removal of prosthesis

4 Surgical Technique: Step 1 General Anaesthesia 1. Anaesthetist skilled in difficult intubations 2. Naso-endotracheal intubation (fig.1) 3. Reverse Trendelenburg (head up) position 4. Antibiotic cover - IV Cephazolin 1g Figure 1 Step 2 Maxillio-Mandibular Fixation 1. Apply arch bars or MMF screws 2. Wires are applied loosely to allow mandibular manipulation (fig.2) Figure 2 Step 3 Preparation 1. Shave pre-auricular hair/sideburns 2. Apply waterproof sleek tape to cover hair above & behind ear 3. Mark out incision lines in preauricular, neck and abdominal areas (fig.3) 4. Liberally apply surgical antiseptic solution over all surgical sites Figure 3 Step 4 Draping 1. Isolate surgical sites and cover the patient with sterile surgical drapes (fig.4) 2. Set up diathermy, suction and connections for power tools. Figure 4

5 Step 5 Pre-auricular Approach to TMJ 1. Inject local anaesthetic along incision line and into joint capsule 2. Incise through skin and subcutaneous fat 3. Use sharp scissors to bluntly dissect down to temporalis fascia 4. Tie or retract temporal vessels as necessary 5. Expose temporalis fascia along whole length of incision (fig.5) 6. Make horizontal incision along superior edge of root of zygomatic arch (fig.6) 7. Make 60 0 incision obliquely downwards from horizontal incision (fig.6) 8. Sharply raise triangular flap to expose lateral joint capsule (fig 7) 9. Enter superior joint space via sharp incision through lateral capsule (fig.8,9,10) Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10

6 Step 6 Discectomy, Eminectomy and Condylectomy 1. Enter superior joint space and expose whole of eminence anteriorly 2. Surgically excise and remove entire disc 3. Use condylar retractors to expose neck of condyle (fig.11) 4. Perform osteotomy at neck of condyle with oscillating saw blade (fig.12) 5. Sharply dissect off lateral pterygoid muscle attachment and remove condyle 6. Push mandible up into empty fossa to allow further oblique osteotomy of condylar stump at low sub-condylar level (fig.12) 7. Perform eminectomy using sharp osteotomes and files to reduce to flat surface (fig.13,14) Figure 11 Figure 12 Figure 13 Figure 14 Step 7 Placement of Fossa Component 1. Remove any remnants of disc and synovial tissue from glenoid fossa 2. Use oscillating diamond file to flatten eminence and lateral aspect of glenoid fossa and root of zygomatic arch 3. Place the fossa component parallel to root of zygomatic arch and check for stability 4. Eliminate any bony irregularities that may cause rocking of Figure 15 prosthesis 5. Secure fossa prosthesis with 4 or 5 Mandibular bone screws (2.0 mm x 6mm) (fig.15)

7 Step 8 Tighten MMF 1. Place a split drape over the mouth to isolate it from the rest of the operative field 2. Tighten the MMF wires making sure the pre-existing occlusion is correct (fig.16) 3. Remove your gloves and change to a new pair to avoid oral contamination. Figure 16 NB: the oral MMF instruments must be separate from the rest of the surgical instruments Step 9 Retro-Submandibular Approach 1. Inject local anaesthetic solution along incision line in neck 2. Cut through skin and subcutaneous fat until you expose platysma muscle layer 3. Cut through platysma to expose the deep cervical fascia 4. Follow the plane of deep cervical fascia dissecting superiorly towards angle of mandible 5. Once the angle of mandible can be palpated, sharply incise along the lower border (fig.17) 6. Bluntly lift the masseter muscle attachment off the lateral ramus of mandible 7. Use a Seldin to track superiorly and posteriorly along the ramus to the resected TMJ area. 8. The head of the Seldin should appear in the pre-auricular incision (fig.18) 9. Gently rock the Seldin back and forth to release the masseter & soft tissues off the lateral surface of the mandibular ramus. Figure 17 Figure 18

8 Step 10 Placement of Mandibular Condyle Component 1. Use an oscillating diamond file to flatten the bone of the lateral ramus of mandible 2. Insert the Condylar prosthesis via the neck incision (fig.19) 3. Check the seating of the head of the condyle in the fossa component. (fig.20) 4. Line up the lower border of the condylar prosthesis with the lower border of the mandible (fig.21,22) 5. Make sure the condylar head is properly positioned in the middle of the fossa component 6. Secure the condylar prosthesis to the ramus of mandible with 6 screws (2.3mm x 8mm) Figure 19 Figure 20 Figure 21 Figure 22 Step 11 Abdominal Fat Graft 1. Make a 10cm horizontal linear incision, 10cm below umbilicus 2. Tease out about 50ml of subcutaneous fat with Metzenbaum scissors (fig.23) 3. Place the fat graft around the condylar stem of the condylar prosthesis via the preauricular approach (fig.24) Figure 23 Figure 24

9 Step 12 Closure of Wounds and Dressings 1. Check the occlusion and mandibular function before closure (fig.25) 2. Remove intermaxillary fixation 3. Make sure there is no active bleeding before surgical wounds are closed (fig.26) 4. Abdominal graft donor site is closed with 2/0 deep vicryl and 2/0 continuous subcutaneous prolene (remove in 7-10 days) or monocryl (dissolving) are used for skin closure 5. Neck incision is repaired with 4/0 deep vickryl sutures and 4/0 monocryl continuous subcutaneous suture for skin closure. Surgical neck drain is recommended. (fig.27) 6. Gently irrigate and suction out the ear canal 7. Pre-auricular incision is closed with 4/0 deep vicryl sutures and interrupted 5/0 nylon sutures for skin (removed in 7 days) 8. Barrel pressure bandage over head is applied for up to 24 hrs 9. Standard surgical dressings applied to other incision sites 10. Post-operative x-rays are mandatory to check alignment (fig.28,29) Figure 25 Figure 26 Figure 27 Figure 28 Figure 29 DISCLAIMER: The surgical steps described are only a basic guide to the stepwise protocol required to implant a Melbourne TMJ prosthetic total joint replacement system. It is highly recommended that Surgeons seek guidance from Mentors who are experienced in this technique. Furthermore, Surgeons wanting to place TMJ total prosthetic joints are advised to attend clinical and cadaveric workshops before attempting their first case. OMX Solutions Level Collins Street Melbourne Victoria 3000, Australia Phone: enquiries@omx-solutions.com Website: