Introduction

Jaw deformities may result from temporomandibular joint (TMJ) disorders. TMJ pathology is often associated with dentofacial abnormalities, malocclusion, TMJ pain, headaches, and myofascial pain [1]. The loss of mandibular continuity caused by osteomyelitis, ablative tumor therapy, or severe trauma may significantly affect a patient’s psychological and physiological well-being. Plastic surgeons find it extremely difficult to restore occlusal function and reconstruct the facial form due to the complexity of mandibular anatomy [2, 3].

Alloplastic grafts, such as acrylic, synthetic fibers, ulnar head prostheses, compressible silicone rubber, and total joint replacements, as well as autogenous bone grafts, such as fibula, metatarsal, clavicle, iliac, and costochondral grafts, have been described as the primary reconstructive approaches [4, 5].

To achieve satisfactory results in accurate mandibular contouring and restoration of masticatory function, the three-dimensional configuration of the graft is the most important factor influencing the facial contour and the occlusal relationship. Proper occlusal relationship and condylar position are also particularly important [6, 7].

Numerous maxillofacial surgical applications, including dentofacial abnormalities, congenital deformities, defects following tumor ablation, post-traumatic defects, reconstruction of cranial defects, and reconstruction of the TMJ, have utilized computer-assisted surgical simulation technologies. Compared with conventional case preparation techniques, these technologies can reduce the amount of time the surgeon spends preparing for surgery, increase surgical precision, and provide both intermediate and final surgical splints [8, 9].

Mandibular condyle reconstruction presents several challenges, including potential nerve injury, infection, bleeding, and long-term complications. The complexity of the surgery increases with case severity, particularly in patients with ankylosis or a history of previous surgeries. Functional restoration, especially in children, and the long-term stability of reconstruction are also key considerations. Computer-assisted surgery simulation offers significant advantages by enabling the design and simulation of the surgical procedure and providing fast and accurate results, which compensate for limitations of conventional methods [10].

Our study aimed to use this technology to guide the selection of the rib and print a template with the precise length, and to guide the osteotomy for the joint pathology. The contouring and fixation of the rib grafts were also addressed in this study.

Materials and methods

Preoperative evaluation

Clinical examination

Evaluation incorporated a thorough history and physical examination of occlusion, midline deviation, facial asymmetry and measurement of maximal incisor opening.

Radiographical examination

Preoperative radiographic analysis incorporated panoramic and chest X-rays. All selected patients had a computed tomography (CT) scan; the preoperative CT should have an interslice thickness of 1 mm, and the CT should not be older than 3 months (Figure 1). Data acquisition and processing: Patients underwent the preoperative cranialmaxillofacial and chest CT scans with 0.625 mm slice increment, 0.3 mm voxel size, 17 × 23 cm extended field of view, 1,120 kV, 5 mA, and “4 ms” exposure time with a stable molar occlusion [12], using ProPlan CMF software [FDA 510 (k) Number: K111641], Materialise Mimics 16.0 (Materialise, Leuven, Belgium) and DePuy Synthes (Johnson & Johnson, Solothurn, Switzerland), for virtual surgical planning.

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Figure 1. Traumatic bone cyst of the left mandibular ramus and condyle. Panoramic X-ray film shows a left traumatic bone cyst related to the left ramus and condyle (A). Axial and coronal cuts CT shows a left traumatic bone cyst (B, C). Source from case No.3.

Surgical intervention

All procedures, including general anesthesia and nasoendotracheal intubation, were performed under strict conditions. Preauricular and Risdon incisions were combined. To ensure optimal visualization and facilitate management of any external carotid branch hemorrhage that may arise during the procedure, it was essential to finish the dissections of the superior and inferior incisions prior to performing osteotomies.

The dissection was carried out as far posteriorly as feasible to prevent injury to the branches of the facial nerve, all the way down to the posterior root of the zygomatic arch. Adequate dissection of the soft tissue medial to the neck of the condyle was essential to avoid hemorrhage from the internal maxillary artery and its branches, which are most commonly involved with hemorrhage during TMJ surgery. Ramal exposure was achieved through the posterior mandibular, which provided excellent visualization of the entire ramus for placement of the costochondral graft. Prior to releasing the bone mass in case of TMJ ankylosis, the condyle was excised in accordance with the osteotomy guidance (Figure 2).

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Figure 2. Computer-assisted surgery simulation technology used to make a surgical template of costochondral graft. Source from case No.3.

To provide an appropriate bone interface between the rib and ramus, the lateral surface of the ramus was clipped. This was predicated on the preoperative planning and measurements.

The mandible was virtually repositioned based on CT measurements; the height from the glenoid fossa to the mandibular angle was measured, as this corresponded to the required rib length. All the contralateral 5th, 6th, and 7th ribs were exported in STL format to choose the most suitable rib for reconstruction. By making an inframammary incision, typically made in the inframammary crease, which is the natural fold under the breast, beginning about 4 cm from the midline, the incision’s length was 3 to 4 cm. A costochondral graft was removed from the right chest at the 5th, 6th, and 7th rib bones. The rib length ranged from 3 to 5.5 cm, and included no more than 5 mm of cartilage corresponding to the prefabricated template as determined by the cranio-maxillofacial 3D reconstruction.

To ensure proper placement of the cartilage into the middle of the temporomandibular fossa, the cartilage was cut and shaped. A titanium plate with four holes was used to secure the graft to the lateral surface of the ramus with bicortical screws measuring 10 mm in length and 2 mm in diameter. To prevent reankylosis, temporal fascia was interposed in the joint space and secured with 3-0 Vicryl suture. Wound closure was performed in a layer-by-layer manner, where the muscle layer was closed and the skin was sutured with interrupted 3-0 Vicryl sutures. A pressure dressing was applied and changed every 12 hours for 4–5 days postoperatively.

Results

A physical examination was performed on all patients as part of the routine assessment of overall health status, and all patients were found to be fit for surgery with no complications regarding general examination and assessment. Ten patients (eight male and two female), with a mean age of 14.5 years (range: 12–20 years), including two cases of unilateral ankylosis (20%), six cases of TMJ pathology (60%), including three cases of aneurysmal cyst (30%), two cases of traumatic bone cyst (20%), and one case of osteomyelitis (10%), and two cases of condylar resorption due to long-standing infection (20%). All patients underwent costochondral graft reconstruction guided with computer-assisted surgery simulation. The 5th rib was selected in six joint reconstructions, while the 6th rib was used in four reconstructions (Figure 3).

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Figure 3. The distribution of the etiology of the mandibular defect.

Before surgery, all patients had moderate discomfort, with a mean VAS score of 4.8 (range: 1–7 points). Six patients reported excellent pain relief, while four reported moderate relief. At one month postoperatively, the mean VAS score was 2.2 points (range: 1–4 points). By six months after surgery, all patients were satisfied with the reduction in their degree of pain.

After six months, the mean postoperative maximum interincisal opening was 30 mm (range: 26 to 33 mm) and standard deviation 1.75 mm, while the mean preoperative maximum interincisal opening was 18.1 mm (range: 15–29 mm) and standard deviation 2.5 mm. The difference in maximal interincisal opening between the preoperative measures showed notable improvements (p < 0.001).

A successful postoperative occlusion was achieved in every patient. No patients had complaints regarding weakening of the facial muscles on the repaired side or numbness of the lower lip. Every patient was pleased with the appearance of the wound scar, and every patient’s range of motion in the mandible had significantly improved after surgery.

All patients’ mandibular condyle reconstructions using the costochondral graft were effective, according to postoperative CT scans, and every rib suited the lateral surface of the ramus perfectly. The titanium plate and screws were precisely secured, and the postoperative position of the bone grafts was comparable to the normal position of the mandible in relation to the glenoid fossa (Figure 4).

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Figure 4. Postoperative 3D and axial computed tomography show costochondral graft with accurate position in relation to the lateral surface of ramus. Source from case No.3.

Discussion

Computer-assisted surgery simulation technology eliminates the traditional steps in which the surgeon manually positions the costochondral graft into its new final position on the mandible, thus saving time and improving surgical accuracy. We have documented the accuracy of the computer-assisted surgery simulation in this study compared to the traditional planning methods, as the actual surgical outcomes were consistent with the planned outcomes. These findings are in agreement with a recently published study demonstrating that the computer-assisted surgery simulation protocol results in improved outcomes [13–16].

The costochondral transplant is the autogenous approach that is most commonly used. Compared to other autogenous transplants, costochondral transplantation offers numerous benefits. Harvesting is simple and causes minimal morbidity for patients. The costal cartilaginous cap is composed of hyaline cartilage, which allows the transplant to withstand functional loading effectively and exhibit outstanding biocompatibility. Children who receive a costochondral graft may grow. Notwithstanding these benefits, several potential complications exist, including donor-site morbidity, poor rib bone quality, the potential for cartilage and rib bone to separate, graft fracture, recurrence of ankylosis, and inconsistent development behavior. Despite being rare, donor site morbidity, including emphysema, atelectasis, pleural effusion, pneumothorax, and pleural rupture, can nonetheless cause discomfort for patients. The graft was harvested from the right side to differentiate postoperative pain from cardiac pain and the cartilaginous part, which has an important role as a growth center [17, 18].

Costochondral grafts have been reported in several publications for condylar reconstruction in patients with merely a preauricular incision [19] or an intraoral incision along with a preauricular incision [20], which offer the advantage of minimizing the risk of injury to the facial nerve’s marginal mandibular branch. To provide wide exposure and good access without causing affection to the marginal mandibular nerve, our procedure only required a preauricular incision in conjunction with a Risdon incision.

Based on the clinical findings, 100% of the joints were reconstructed using the fifth or sixth ribs. According to earlier research, several surgeons removed the fifth and seventh ribs for joint reconstruction [19]. Another study reported that the sixth rib has the optimal depth and width, this study precisely answered that the fifth and sixth ribs may be harvested for the majority of joint reconstructions [20].

In terms of surgical guide accuracy, the findings demonstrated that all guides were stable with sufficient retention on the bone surfaces, guided all osteotomies safely, and were simple to insert in their designated locations. Other writers, who discovered that computer-aided surgery simulation greatly increased the safety of TMJ ankylosis procedures and decreased the frequency of complications, corroborated these results. These results run counter to those of another study that found certain limitations, including the likelihood that the surgical guides would be difficult to put on [21, 22].

The limitations of this study include the following: First, the statistical strength of the results is limited by the small sample size (10 patients). To confirm the observed trends and support the findings, a larger sample size would be required. Second, the absence of a control group makes it difficult to assess how much of the observed benefits can be attributed to 3D-printed templates and virtual surgical planning alone, rather than to conventional surgical techniques. Third, the six-month follow-up period was relatively short, which might not have sufficiently captured the stability of results over the long term or the possibility of late complications. To validate and build on these findings, more research with randomized controlled designs, larger populations, and longer follow-up periods is crucial.