The purpose of this study was to evaluate the stability and viability of mandibular bone regeneration using a poly( l -lactide) (PLLA) mesh and autogenous particulate cancellous bone and marrow (PCBM). Sixty-two procedures were undertaken at eight hospitals (22 malignant tumours, 30 benign tumours, five cysts, two osteomyelitis, two trauma, and one atrophy of the alveolar ridge); the success rate was 84%. The follow-up period was between 9 and 200 months (mean 88.2 months). Consequently, bone regeneration at 6 months postoperation was excellent in 35 cases (57%), good in 17 cases (27%), and poor in 10 cases (16%). In six of the ‘poor’ cases, the PLLA mesh was removed due to local infection early after surgery. Bone resorption > 20% was observed in only one of 46 cases with a follow-up term of >1 year. There were no signs of any other adverse effects except in one case where a section of the tray broke off late in the follow-up period. It is concluded that this method is stable and effective due to favourable morphological and functional recovery and low invasiveness. It may thus be a useful alternative procedure for mandibular reconstruction.
Defects in the mandible due to tumour excision or injury leave the patient with not only a noticeable deformity of the face, but also a mandible that does not function properly for chewing, swallowing, and speaking. Such a defect is generally reconstructed using bone grafting, or artificial materials. Both methods have advantages and disadvantages in terms of morphological and functional recovery.
Microvascular free flaps from the fibula or iliac crest are often used and are considered a gold standard for the reconstruction of critical mandibular defects; however these procedures require specialized surgical expertise and hospital infrastructure, and donor site morbidity is significant. There are also limitations in restoring the complex shape of the mandible. The goal of mandibular reconstruction is to recover aesthetics as well as occlusal and masticatory functions using dentures and dental implant applications, which necessitates physiological mandibular reconstruction. Regenerative medicine applying tissue engineering (TE) techniques allows us to achieve this goal. One method of bone regeneration involves clonal proliferation (‘bulking up’) of osteoprogenitor cells ex vivo, followed by the induction of differentiation on an engineered designed scaffold and transplantation into the body as cultured bone, a process known as extracoronal bone tissue engineering. However, the scaffolding for this three-dimensional culture and cultivation method must be optimized to ensure safe and substantial bone formation. Another TE method for bone regeneration is to directly transplant tissue containing mesenchymal stem cells or osteoprogenitor cells into the body with a scaffold for morphological maintenance, and therein guide bone formation into the desired shape, a procedure known as in situ tissue engineering. Such a scaffold should be fully biodegradable after bone regeneration. Kinoshita et al. have developed a scaffold comprising poly( l -lactide) (PLLA) mesh and have established a method of jaw bone regeneration using the PLLA mesh and particulate cancellous bone and marrow (PCBM) as a cellular reservoir. We performed a multicenter research study and clinical trial of mandibular regeneration surgery using this method, focusing particularly on its stability and viability.
Materials and methods
PLLA mesh is fabricated by spinning PLLA (molecular weight 20.5 × 10 4 ) into monofilaments. This study employed sheet- and tray-types of PLLA mesh, processed into mandible shapes (Gunze Ltd., Kyoto).
The PLLA mesh sheet or tray was adjusted to the bone-defect shape with scissors and moulding at about 70 °C; it was then fixed to the remaining bone using stainless-steel wire. PCBM was harvested either from the anterior or posterior iliac bones, then injected and densely packed into the mesh tray, which was consolidated by this dense packing of PCBM. In mandibular marginal resections, intermandibular fixation is not necessary, but in segmental or unilateral resections, intermandibular fixation or fixation using a plastic splint and chin cap is necessary for 1–2 months.
Sixty-two mandibular reconstruction surgeries using PLLA and PCBM were performed at eight facilities between April 1995 and September 2001. This study had ethics review board approval, and informed consent was obtained for all patients. Contraindications to using this method (i.e. exclusion criteria) included: pre-existing infection; unstable blood circulation to the skin and oral mucosa covering the implanted material; inflexibility in the skin and oral mucosa covering the implanted material; any disease or abnormality contraindicating bone graft or surgery in general.
The subjects were 41 males and 21 females aged between 12 and 78 years (mean age 47.1 years). Twenty-two cases had malignant tumours, 30 had benign tumours, five had cysts, two had trauma, two had osteomyelitis, and one had atrophy of the alveolar ridge. Forty-two cases underwent primary reconstruction surgery, and the remaining 20 underwent secondary reconstruction surgery. The preferred mandibular resection methods in 59 cases were: marginal resection (25 cases), segmental resection (31 cases), and unilateral resection (three cases). Preoperative irradiation of 20–70 Gy (mean 37.4 Gy) was performed in 17 cases. Nine patients required a combination of soft tissue reconstructions. The quantity of PCBM collected was 4–60 g (mean 20.8 g). The bone defect types in the segmental and unilateral resection cases were identified by the HCL classification as involving the entire central segment (C), the lateral segment but not the condyle (L), and/or the lateral segment including the condyle (H). Of 34 patients requiring segmental and/or unilateral resection, 17 were classified as L, eight as LC, six as LCL, two as H, and one as HC. The follow-up period was a minimum of 6 months postoperatively, followed by as much additional follow-up as possible. The total follow-up was between 9 and 200 months (mean 88.2 months) ( Table 1 ). Patients for whom follow-up of over 1, 3, or 5 years was achieved were evaluated for bone resorption and late adverse effects. The interval of observation was once a month for up to a year after surgery, with observation for malignant tumours performed once every 1–2 months and for benign lesions every 2–3 months up to 2 years. After 2 years, the follow-up interval was increased to once every 3–6 months.
|Patient||Age, years||Sex||Diagnosis||Mandibulectomy||Defect a||RT (Gy)||Period b||Mesh type||ST Rec.||Bone regeneration||Follow-up (months)|
|2||62||M||SCC||Marginal||–||30||First||Tray||Free flap||Poor (infection)||–|
|9||57||F||SCC||Segmental||L||20||Second||Tray||Pedicle flap||Poor (infection)||–|
|11||66||M||SCC||Segmental||L||30||First||Tray||Free flap||Poor (infection)||–|
|49||50||F||Keratocystic odontogenic tumour||Segmental||L||–||First||Tray||–||Excellent||120|
|57||32||M||Calcifying odontogenic cyst||Segmental||LC||–||First||Tray||–||Good||55|