Scaffold for Nasoalveolar Augmentation

This trial will utilise a patient specific 3D-printed medical grade polycaprolactone-tricalciumphosphate (mPCL-TCP) scaffold for the purpose of paranasal maxillary augmentation in patients with a unilateral cleft lip. The PCL-TCP scaffolds used will be augmented through the addition of bone marrow aspirate (BMA) and injectable Platelet Rich Fibrin (i-PRF). Cleft lip patients with paranasal maxillary deficiencies associated with nasal alar base retrusion will be candidates for inclusion in the trial. Scaffold placement will be timed to coincide with either their secondary alveolar bone graft or their rhinoplasty (intermediate or secondary). The standard of care at our institution for a nasal base deformity is placing an onlay cancellous bone graft along the piriform rim and superior maxillary alveolus at the cleft margin. The long-term persistence of cancellous bone graft volume and position, however, is generally considered poor and its direct effect on nasal base form is largely unknown. As such, the scaffold will replace the onlay bone graft, not adding any time to the standard of care procedure. The participant specific scaffolds will be designed following an existing published workflow as described by Bartnikowski M, Vaquette C and Ivanovski S (Bartnikowski et al. 2020). Firstly, the participant’s de-identified CT data is loaded into the Materialise Mimics software (Materialise, Belgium) and a mask is created using the threshold tool to isolate the bone of the participant. This threshold can be adjusted depending on the quality of the scan. Next, noise from the mask (a result from scan or metallic artefacts) is cleaned using the multiple slice edit and region grow tools and bones can be separated using the split mask tool. Once the maxilla has been isolated and scan artefacts have been removed it can be exported into 3-Matic (Materialise, Belgium) for further processing and the creation of the patient specific scaffold outline. Note that in 3-Matic the maxilla can be smoothed using the smooth tool if appropriate and re-meshed to minimise the presence of surface artefacts from the STL conversion process. To compensate for potential dimensional errors in the subsequent processes and manufacturing step, the part is wrapped using the wrap tool. The area to undergo onlay bone augmentation is then identified by the treating clinician and the area is traced using a curve tool. The non-cleft maxilla (contralateral side) geometry is duplicated, mirrored in reference to its sagittal plane, and virtually placed over the cleft side to guide design of the anatomical template. The solid geometry is then saved and exported as an STL file. The anonymised scaffold outline will then be sent to Osteopore for manufacturing of the mPCL-TCP scaffold. The Osteopore mPCL-TCP are made of an FDA approved polymer (K051093) PCL that is bioresorbable, slow-degrading and possesses adequate mechanical strength, similar to that of trabecular bone. The mPCL-TCP scaffold will be manufactured using additive manufacturing to produce accurate and reproducible participant-specific implants. The protocol for device manufacturing will be following that of the Osteopore Patient Specific Implant (PSI) which has already been used at QCH. Serial computed tomography (CT) or cone beam CT (CBCT) scans will be taken for the participants enrolling in this study. All patients will have had a CT or CBCT prior to their alveolar bone graft as per standard of care and then again at approximately 12 months following secondary alveolar bone grafting insertion of the scaffold. This is part of the standard of care for alveolar bone graft patients. The CT scans will be used to assess bone volume formed within the scaffold and the volume of bone formed Surgical placement of the scaffold will be performed under a general anaesthetic at QCH by the treating clinician (all treating clinicians are part of the study team) at the same time as bone grafting of the alveolar cleft or rhinoplasty. A. Scaffold placement at the time of alveolar bone graft: For patients having scaffold placement at the time of alveolar bone grafting, surgery involves incisions along the cleft margin, raising gingivoperiosteal flaps to close the nasal floor and palatal defect (roof of the alveolar cleft). Iliac crest cancellous bone graft is then harvest via a short incision posterior to the anterior superior iliac spine and this is packed into the alveolar cleft. A broad superiorly based gingivoperiosteal flap is then raised distal to the cleft (from the lesser alveolar segment) and this is advanced with a backcut in the region of the first molar to close the anterior wall of the cleft. Vicryl sutures are used to close mucosa. This is the standard approach amongst all cleft surgeons in the unit and will not differ in patients undergoing scaffold placement. Following placement of iliac crest cancellous bone graft, a scaffold will be inserted to sit along the piriform margin. The amount of overlap from the piriform margin and across the superior alveolus will be determine pre-operatively based on the patient’s imaging. It is anticipated that there will be some overlap over both the piriform and grafted superior alveolus to adequately support the alar base. The scaffold extension for nasal alar support will be sutured to the fibrofatty tissue of the alar base. Small perforations in the maxilla deep to the region of scaffold placement, avoiding unerupted teeth or tooth roots, will be performed to encourage bony bleeding. The scaffold will then be inserted and secured with one or several degradable screws (e.g. Sonic WeldTM (KLS Martin) or Delta system (Stryker)) through premade flanges. Thereafter, BMA and autologous i-PRF will be injected in the scaffold. Once the scaffold has been secured, the lateral gingivoperiosteal flap will be advanced in the standard manner as all other patients undergoing an alveolar bone graft and closed tension free. The participant will be admitted 1-2 nights for observation. Post-operative oral antibiotics will continue for 24 hours, and chlorhexidine mouthwash will be prescribed for all participants to be used for 2 weeks as per standard protocol. B. Scaffold placement at the time of rhinoplasty: For patients having scaffold placement at the time of a rhinoplasty, a standard open tip rhinoplasty will be carried out by the treating clinician. A separate incision will then be made in either the alar crease or the upper gingivolabial sulcus, allowing access and subperiosteal dissection of the piriform margin and superior alveolus. The patient specific implant will then be inserted and secured in the same manner described above. Thereafter, BMA and autologous I-PRF will be injected in the scaffold. The participant will be admitted 1-2 nights for observation. Post-operative oral antibiotics will continue for 24 hours. After surgery, the patient will return to standard of care, and return for visits to the QCH outpatient clinic for a review as per standard of care after 2 weeks, 3 months, 6 months and 12 months. At these visits everything will as per standard of care except for the Cleft-Q questionnaire that the patient will fill out at the enrolment visit and at the 12 month visit. The patient will then continue to be under the care of their treating clinician until they reach maturity and leave the care of the QCH as per standard of care.