A Case Report: Regenerative Biodegradable Chin Implant—A Viable Futuristic Option

Abstract

Chin augmentation can dramatically transform a patient's appearance. Various techniques are in use, each with their specific problems and limitations. We present the first case report from the Indian subcontinent using a custom 3D-printed, bioresorbable polycaprolactone implant. We demonstrate, by appropriate imaging, the replacement of the implant at long-term (22 months) follow-up by patient's own autologous bone formation. An excellent aesthetic result was achieved. Relevant points of technique, as well as pertinent properties of the material, are discussed. This material has been used in neurosurgery and in the management of orbital fractures. Yet, worldwide, very few (3–4) cases of chin implant have been done using this material. We believe this to be a useful and sustainable material, offering several advantages, as set out in the case report.

Keywords

customized chin augmentation - biodegradable chin implant - case report of regenerative chin implant

Introduction

The options for chin augmentation include genioplasty, bone graft, and silastic implants. Genioplasty by advancement osteotomy may not be sufficient and require the placement of hardware. Bone graft requires additional surgery, with donor site pain and deformity, along with hardware placement. Silicon implants are commonly done through the intra- or extraoral route, but they never integrate with the body. The chances of extrusion, displacement, and availability of limited size are some of their shortcomings.[1] [2] [3] We present a 2-year follow-up of a customizable biodegradable chin implant that can integrate permanently with the mandible, with new bone formation.

Case Report

A 23-year-old man ([Figs. 1A] [2A] [3A]) presented with a request for augmentation of the chin. The patient was assessed with 3D simulation software to understand the extent of augmentation desired. The desired augmentation in the anteroposterior plane was 1.7 cm: much beyond the usual available size. The patient expressed the desire to avoid a foreign body and refused to allow a bone graft to be harvested from the iliac crest. The senior author came across a regenerative material by Osteopore, marketed in India by Myovatec. The said material is polycaprolactone, which is biodegradable in the body by hydrolysis.[4] [5] [6] [7] [8] The material was described as being light, porous with a honeycomb structure, like cancellous bone. A customized implant was 3D printed based on the patient's computed tomography (CT) scan Digital Imaging and Communications in Medicine (DICOM) images shared with the company. Necessary suture or biodegradable screw points were identified and necessary modification in shape was made ([Fig. 4]). The implant was delivered in a gamma-ray-sterilized packet. The surgery was performed under general anesthesia through the intraoral route. Standard gingivolabial sulcus incision extending from the first right premolar to the first left premolar was made. An effort was made to retain enough muscle on the alveolus for watertight closure later. The periosteum was then elevated along with the rest of the muscle bulk, sparing the mental nerve carefully. The length of the incision required was nearly as much as the length of implant. The implant ([Fig. 5A]) was soaked in about 8 mL of the patient's own platelet-rich plasma (PRP). The implant was inserted and adjusted, snugly fitting the symphysis menti and the mandibular border. The fit was perfect as it was made as per the patient's own CT images. The implant was secured to the mandibular periosteum using 4–0 PDS. A robust, watertight closure was done, approximating the periosteum, muscles, and mucosa in that order using 4–0 PDS. The standard postoperative protocol including antibiotics, anti-inflammatory agents, and antiseptic mouthwash was followed. Chin belt immobilization was continued for 30 days. [Figs. 1B] [2B], and [3B] show the result after 30 days. [Figs. 1C] [2C], and [3C] show the result of augmentation with regenerative implant after 22 months. X-ray of the skull, lateral view, done 45 days after the procedure failed to show the implant, as seen in [Fig. 5B]. However, upon soft-tissue X-ray exposure, the implant was well visible on the same day, as seen in [Fig. 5C]. Formation of cancellous-like bone was confirmed on post-op magnetic resonance imaging (MRI) done after 22 months. The implant shadow was reported as isodense with the bone ([Fig. 6]).

Fig. 1 (A) Pre-op front view of the patient. (B) Front view at 1 month postoperatively. (C) Front view at 22 months postoperatively.

Fig. 2 (A) Pre-op right profile view of the patient. (B) Right profile view at 1 month postoperatively. (C) Right profile view at 22 months postoperatively.

Fig. 3 (A) Pre-op left profile view of the patient. (B) Left profile view at 1-month postoperatively. (C) Left profile view at 22 months postoperatively.

Fig. 4 Pre-op planning. Digital Imaging and Communications in Medicine (DICOM) images and simulation of implant on the 3D computed tomography (CT).

Fig. 5 (A) Implant. (B) Lateral X-ray bone exposure does not show the implant. Taken after 45 days. (C) Lateral X-ray soft-tissue exposure after 45 days shows the implant.

Fig. 6 Computed tomography scan after 22 months shows that the implant is isodense with bone.

Discussion

Chin augmentation is a frequently requested surgery by both men and women. A strong, projecting, shapely, and well-defined chin adds to aesthetic facial balance and enhances the confidence of the patient. Socially, a strong chin is associated with assertiveness, leadership, and confidence.

The commonest material used to augment the chin is silicon, which is flexible and can be customized. Silicone implants never integrate and remain encapsulated. They are vulnerable to displacement and deviation with even minor trauma.[1] [2] [3] They are fixed to the symphysis menti with nonabsorbable sutures or even a screw. This amounts to putting a permanent foreign body, which is not desirable in a young patient if the option of an integrable material is available. The main advantage of silicone implant is that it can be inserted through a small incision, which can be intra- or extraoral. The surgery can be done under local anesthesia.

Autologous bone usually integrates well with local bone, yet it needs screws and plates for fixation. An additional surgery, leaving a painful donor area with residual defect, and painful walking in the postoperative period for a long time are the major disadvantages of using iliac bone, the commonest donor site.

Medpor polyethylene implants also have a porous structure, allowing vascular ingrowth and tissue integration, but they are not biodegradable.[9]

Both autologous bone and polycaprolactone need long incisions for insertion. These must be intraoral. Surgery is essentially done under general anesthesia.

The Osteopore technology relies upon in situ tissue engineering to regenerate and rebuild host tissue. The implant has a honeycomb structure. This allows vascular ingrowth and bone deposition into the depth of the implant. The new bone is adequately stiff and has a structure similar to cancellous bone.[4] [5] [6] [7] [8] The implant is completely disintegrated by hydrolysis over 18 to 24 months, by which time bone formation occurs. The shape can be customized as the implant is designed using patient's own images and software-generated wish images and then 3D printed. In our patient, the central dimple was specifically requested, and the implant was shaped according to this. It is important to note that intraoperative adjustment and customization, as can be done with silicon or bone implants, is NOT easily possible in Osteopore implants. The implant can be carved to some extent by chipping with a blade. The material has a melting point of 55 °C. Hence, using a water bath at high temperature may simply melt the implant.[10] Postoperative photographs ([Figs. 1B, C] [2B, C], and [3B, C]) clearly show a square jaw shape with a central dimple, matching the preaugmentation shape. Only the size and projection have increased. This would not be possible with any other material. The follow-up X-ray taken 45 days postsurgery revealed only a soft-tissue shadow, whereas the MRI done after 22 months showed good bone formation. This is in accordance with the properties of the material, as described in the literature by Young et al.[11] The skin over the implant is totally free and can be animated. The aesthetic result was very satisfactory.

An issue we faced was the need for prolonged immobilization using a chin strap. This required the patient to be off work for a good 15 to 20 days. Another issue was discharge of serous fluid on day 7, which necessitated reopening a small part of the incision, followed by drainage of collected 4- to 5-mL serosanguinous fluid and performing meticulous everting reclosure. Otherwise, there were no problems such as bruising, hematoma, infection, and displacement.

Conclusion

This is a case report of the first regenerative chin implant ever done in the Indian subcontinent. Before this, only three to four cases have been done worldwide. Hence, the senior author was keen to present a fairly long-term follow-up, with demonstration of actual bone formation. This material has been used in neurosurgery and spine surgery, successfully. We should look at this as an effective option for autologous bone. We should also establish a proper, regular follow-up community of those who have successfully used this material. Although it is currently considered expensive, this is definitely a futuristic material that allows local bone formation while the material itself undergoes complete hydrolysis.

Conflict of Interest

None declared.

Note

This manuscript was initially presented with a short follow-up during the APSICON 2021 Online Meeting.

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Publication History

Article published online:
03 October 2024