- Email: [email protected]
Navigation-Guided Lateral Gap Arthroplasty as the Treatment of Temporomandibular Joint Ankylosis
CRANIOMAXILLOFACIAL DEFORMITIES/COSMETIC SURGERY
Navigation-Guided Lateral Gap Arthroplasty as the Treatment of Temporomandibular Joint Ankylosis Haijun Gui, MD, DDS,* Jinyang Wu, DDS,y Steve G. F. Shen, MD, DDS,z Joy S. Bautista, DMD, MHPED,x P. J. Voss, MD, DDS,k and ShiLei Zhang, MD, DDS{ Purpose:
This article presents a novel method of navigation-guided lateral gap arthroplasty (LGA) in the treatment of temporomandibular joint ankylosis (TMJA).
Materials and Methods:
Six patients with unilateral TMJA from 2007 through 2011 were included in this study. Presurgical planning was performed to determine the amount and extent of ankylosed bone to be resected using the simulation platform. Minimum follow-up was 6 months. Patients were monitored for complications and signs of recurrence. Maximum mouth opening (MO) was measured and compared intra- and postoperatively.
Results:
Preoperative planning was performed at the STN or Accu-Navi workstation. The amount and extent of ankylosed bone to be resected was determined. All 6 LGAs were completed successfully using realtime instrument- and pointer-based navigation. Measurements performed intraoperatively showed that the mean for maximum MO was about 35 to 40 mm and remained the same postoperatively. Follow-up evaluation showed remarkable improvement in function and esthetics, with no signs of recurrence.
Conclusion:
Navigation-guided LGA can be regarded a viable option for performing this delicate and complicated surgical procedure. Ó 2014 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 72:128-138, 2014
arily after infection.1 Maxillofacial surgeons encounter numerous TMJAs with medial condylar fragment malunion owing to sagittal condylar fractures and delayed treatment.
Temporomandibular joint ankylosis (TMJA) is a joint disorder that refers to bony or fibrous adhesion of the anatomic joint components and the ensuing loss of function; it occurs mainly after trauma and second-
*Medical Doctor, Department of Oral and Maxillofacial Surgery,
Conflict of Interest Disclosures: None of the authors reported any
Ninth People’s Hospital, affiliated to Shanghai Jiao Tong University
disclosures.
School of Medicine, Shanghai, China.
Address correspondence and reprint requests to Prof Zhang:
yMedical Doctor, Department of Oral and Maxillofacial Surgery,
Shanghai Ninth People’s Hospital, Zhi Zao Ju Road 639, Shanghai,
Ninth People’s Hospital, affiliated to Shanghai Jiao Tong University
People’s Republic of China; e-mail: [email protected]
School of Medicine, Shanghai, China. zProfessor, Department of Oral and Maxillofacial Surgery, Ninth
Received May 16 2013 Accepted July 26 2013
People’s Hospital, affiliated to Shanghai Jiao Tong University
Ó 2014 American Association of Oral and Maxillofacial Surgeons
School of Medicine, Shanghai, China.
0278-2391/13/00951-8$36.00/0
xAssociate Professor, Department of Oral Surgery, University of
http://dx.doi.org/10.1016/j.joms.2013.07.039
the East, College of Dentistry, Manila; Department of Oral and Maxillofacial Surgery, Lung Center of the Philippines, Quezon City, Philippines. kMedical Doctor, Department of Oral and Maxillofacial Surgery, Albert-Ludwigs-University Freiburg, Freiburg, Germany. {Associate Professor, Department of Oral and Maxillofacial Surgery, Ninth People’s Hospital, affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.
128
129
GUI ET AL
FIGURE 1. Case 3. Typical Y-shaped bifid condyle and outer bony fusion in the left temporomandibular joint. Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
The management of TMJA is performed mainly through surgical intervention. Various techniques have been described in the literature.1-4 Lateral gap arthroplasty (LGA), which involves resection of the outer part of the ankylosed bone from the medial condyle malunion, is considered useful in preventing recurrence and promoting rehabilitation of mandibular function.5 However, this delicate surgical procedure poses a great challenge for maxillofacial surgeons because access and visibility inside the TMJ region is arduous and a slight mistake can further destroy the medially displaced condyle. In the treatment of TMJ disease, computerized navigation technology plays an ever-increasing role in procedures, such as resection of tumors and gap arthroplasty.6,7 The aim of this study was to share the authors’ experience in managing 6 patients with TMJA using navigation-guided LGA and evaluate the effectiveness of this procedure.
Materials and Methods From 2007 through 2011, 6 patients (2 male and 4 female) with unilateral TMJA were admitted to the authors’ department (Table 1). Their ages ranged from 17 to 24 years (average mean, 25 yr), and the duration of ankylosis varied from 6 to 36 months before surgical intervention. All 6 affected joints were sec-
ondary to sagittal condylar fractures and met the criteria for type II ankylosis group according to the Sawhney classification.1 The average maximal mouth opening (MO) was 10 mm preoperatively. In the left side, a Y-shaped bifid condyle presented the typical appearance on computed tomographic (CT) scans, and a bony bridge had formed, but was localized to a limited area (Fig 1). Spiral CT datasets (0.625-mm slice thickness; Lightspeed 16, General Electric, London, UK) were acquired for all patients preoperatively. Two navigation systems, the STN system (StrykerLeibinger, Freiburg, Germany)2 and the authors’ Table 1. PATIENTS WITH TYPE II TMJA IN THIS STUDY
Case 1 2 3 4 5 6
Gender/ Age (yr)
Site of TMJA
Duration of Ankylosis (mo)
Navigation System
M/17 F/20 M/30 F/26 F/32 F/30
left right left right left left
12 24 12 6 36 12
STN STN Accu-Navi Accu-Navi STN Accu-Navi
Abbreviations: F, female; M, male; TMJA, temporomandibular joint ankylosis. Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
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NAVIGATION-GUIDED LATERAL GAP ARTHROPLASTY
FIGURE 2. Case 3. Preoperative plan designed and displayed in different colors. Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
Accu-Navi system (Accu-Navi, UEG, Shanghai, China),3 were used. Each system was used in 3 patients based on the choice of the surgeon. This study was approved by the ethics committee of the same university (Shanghai Jiao Tong University School, Shanghai, China). Patients provided written informed consent. The 2 navigation systems include a navigation workstation and a tracking device. At the workstation, virtual corrections were performed, new anatomic contours for the glenoid fossa were created, and margins for resection were determined (Fig 2). Because all affected joints were unilateral, the mirroring tool was used by superimposing the unaffected side as a reference on the ankylosed side. The amount of ankylosed bone to be resected was determined and displayed in different colors. According to this method, all 6 presurgical plans were achieved and imported into the navigation system for intraoperative navigation.
All patients underwent image-guided LGA under general anesthesia. After registration, an accurate match between the skull and the virtual model was achieved (Fig 3). Access to the TMJ was achieved through a preauricular incision with temporal extension. This was followed by dissection of the superficial layers and freeing of the temporal vessels. The capsule was visualized and the ankylosed joint was exposed. The surgical drill clamping a DRF (Digital Reference Frame) was calibrated to mark the lateral edges of the upper and lower articular surfaces according to the virtual plan (Fig 4A, B). Next, a calibrated saw was used to perform the osteotomy (Fig 4C, D). A probe was used to check the accuracy and ensure a favorable outcome by frequently pinpointing the anatomic landmarks during surgery. After exposing the joint and determining the site of ankylosis, LGA was performed by resecting the outer bony ankylosed tissue and then burring of the glenoid fossa until a gap of at least 10 mm appeared
131
GUI ET AL
FIGURE 3. Case 3. Registration procedure by pinpointing the screws markers implanted in the alveolar bone before computed tomographic data acquisition. Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
between the roof of the fossa and the mandible. The medial condyle malunion was retained. An intraoperative MO of at least 35 mm was achieved. The disc, if found, or the temporalis myofascial flap was sutured to the articular capsule as interpositional material. The postoperative CT image obtained after 1 week was compared with the preoperative CT image. Physiotherapy was advised immediately postoperatively. This is a key element to the success of TMJA management. In addition, MO exercises began as soon as 7 to 10 days later to achieve an optimal MO. The ranges of MO and TMJ function were continually recorded at followups ranging from 6 to 24 months (average, 12 months).
LGA for the 6 ankylosed joints was completed successfully. Burring of the glenoid fossa and the condylar stump created a gap of about 10 mm between the roof of the fossa and the top of the condylar stump. The fractured fragment of the medial condyle remained. An average MO larger than 35 mm was achieved. The postoperative CT image superimposed on the virtual plan showed great congruency, with discrepancies smaller than 0.8 mm (Fig 5). At 6-month follow-up, maximal MO was maintained at 35 to 40 mm (Fig 6A, B, C, D). There were no complications or relapse encountered in the 6 cases (Table 2). Function was restored and all patients were satisfied with the outcome of the procedure.
Results Registration and instrument- and pointer-based navigation were carried out successfully using the STN and Accu-Navi systems intraoperatively, with discrepancies smaller than 0.8 mm. Image-guided
Discussion Management of TMJA is performed mainly through surgical intervention. Treatment modalities can be divided into 3 groups: gap arthroplasty, interpositional
132
NAVIGATION-GUIDED LATERAL GAP ARTHROPLASTY
FIGURE 4. Case 3. Intraoperative instrument-based navigation using multiplanar and 3-dimensional views. A, B, Image-guided calibrated drill for marking the border before resection. (Fig 4 continued on next page.) Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
arthroplasty, and total joint reconstruction using autogenous or alloplastic material.8 The goals for treatment of TMJA include an increase in the range of MO, improvement of mandibular function, decrease in deformity and pain, prevention of recurrence, and allowance for possible growth of the jaw in young patients.9 However, treatment of TMJA poses a significant challenge because of technical difficulties and a high incidence of recurrence. Gap arthroplasty was initially used for the treatment of TMJA. However, ramus height is commonly decreased after osteotomy, leading to malocclusion and exacerbation of micrognathia or hemi-prognathism. According to the literature reviewed, gap arthroplasty can be a frustrating ordeal because recurrence is a major problem, with relapse rates higher than 50%.10,11 According to Ferretti et al,12 a medially dislocated condylar fracture and the remnant disc often can be found in most patients with traumatic TMJA, which was found to be more prone to ankylosis than other condylar fractures. This is consistent with the authors’ experience. In the present study, Y-shaped bifid condyles presented a characteristic appearance on preoperative CT scans, and all discs were identified and
mostly intact. LGA with the remains of the disc and medial condylar fracture was carried out to restore the normal structure of the TMJ and to prevent recurrence. Panoramic radiographs and CT images showed that the ramus height remained the same and ideal reconstruction of the condyle and articular fossa was achieved. The average MO improved remarkably from 7 mm preoperatively to 35 mm intraoperatively and at least 35 mm postoperatively. No recurrence was observed in any case. These results indicate that LGA for restoration of a medial condyle malunion is an effective method for treating type II posttraumatic TMJA. However, LGA may not be applicable to type III and IV ankylosis because the medially positioned remnant of the articular head (smaller than one third the transverse diameter) is not large enough to maintain stable and sustained pressure, often resulting in displacement, absorption, malocclusion, decreased ramus height, etc. CCG (costochondral grafts) should be considered another option for reconstructing the TMJ. Based on the present study, the authors conclude that early release of TMJA, reconstruction of ramus height with medially displaced condylar fracture
133
GUI ET AL
FIGURE 4 (cont’d). (Fig 4 continued on next page.) Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
combined with restoration of the remnant disc or temporalis myofascial flap as an interpositional material, followed by early MO exercise and vigorous physiotherapy is a successful strategy for the management of TMJA. Close follow-up can help identify those patients prone to early recurrence. However, using a conventional surgical technique is challenging when performing LGA because of poor visibility in the deep TMJ region. Any minor mistake could destroy the delicate medial condyle malunion, which should be retained. Accurate preoperative simulation and precise surgical execution are required to produce the optimal outcome. Computerized navigation systems, which allow preoperative simulation and intraoperative visualization, have been described as an effective treatment modality for improving surgical outcome.6,7,13-15 In the present study, the commercial STN navigation
system and the authors’ commercial Accu-Navi navigation system were used. These systems have been introduced into craniofacial surgery and have a proven accuracy of less than 0.1 mm.2,3 To improve visibility and safety, the navigation-guided technique was introduced to assist in the LGA procedure. In patients with TMJA, the ankylosed bone is irregular and has no clear margins, so resecting bone at the skull base is quite difficult. Computer-assisted planning and intraoperative navigation have greatly increased safety in skull base surgery and substantially decreased complications.16,17 For patients with unilateral TMJA, the preoperative plan could be carried out using a mirroring tool and side-to-side comparison. The selected fraction was mirrored from the unaffected side against the deformed side. The new contour was used as the resection margin and intraoperative control during surgery. LGA was
134
NAVIGATION-GUIDED LATERAL GAP ARTHROPLASTY
FIGURE 4 (cont’d). C, D, Image-guided calibrated saw for osteotomy in accord with the virtual plan. (Fig 4 continued on next page.) Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
performed under the guidance of the navigation system so that the medial condyle malunion could be protected against displacement. Consistent with the findings of other groups, navigation-guided technology enabled the execution of LGA more reliably by identifying safety margins, preserving vital struc-
tures, and operating with better visualization of the area. In conclusion, navigation-guided LGA with the remaining ramus height and occlusion showed great benefits for accuracy and safety in this potentially complicated procedure.
135
GUI ET AL
FIGURE 4 (cont’d). Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
136
NAVIGATION-GUIDED LATERAL GAP ARTHROPLASTY
FIGURE 5. The maximal discrepancy was confirmed to be smaller than 0.8 mm by superimposing the postoperative computed tomogram (orange skull) on the preoperative plan (transparent purple part). Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
FIGURE 6. Case 3. Average mouth opening improved significantly from A, 10 mm preoperatively to B, 40 mm intraoperatively and (Fig 6 continued on next page.) Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
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GUI ET AL
FIGURE 6 (cont’d). C, 38 mm 6 months postoperatively. D, Postoperative effect with resection of outer bony fusion and retention of the medial condyle malunion. Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
Table 2. SUMMARY OF PREOPERATIVE, INTRAOPERATIVE, AND POSTOPERATIVE EXAMINATIONS
Case 1 2 3 4 5 6
Preoperative MO (mm)
Intraoperative MO (mm)
Duration of Follow-Up (mo)
Postoperative MO (mm)
5 6 10 5 8 7
38 35 40 35 40 40
24 12 6 12 6 6
35 35 40 35 40 35
Abbreviation: MO, mouth opening. Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
138
References 1. Mangenollo-Souza LC, Mariani PB: Temporomandibular joint ankylosis: Report of 14 cases. Int J Oral Maxillofac Surg 32: 24, 2003 2. Karaca C, Barutu A, Baytekin C, et al: Modifications of the inverted T-shaped silicone implant for treatment of temporomandibular joint ankylosis. J Craniomaxillofac Surg 32:243, 2004 3. Saeed N, Hensher R, McLeod N, et al: Reconstruction of the temporomandibular joint autogenous compared with alloplastic. Br J Oral Maxillofac Surg 40:296, 2002 4. Long X, Li X, Cheng Y, et al: Preservation of disc for treatment of traumatic temporomandibular joint ankylosis. J Oral Maxillofac Surg 63:897, 2005 5. Li ZB, Li Z, Shang ZJ, et al: Potential role of disc repositioning in preventing postsurgical recurrence of traumatogenic temporomandibular joint ankylosis: A retrospective review of 17 consecutive cases. Int J Oral Maxillofac Surg 35:219, 2006 6. Schmelzeisen R, Gellrich NC, Schramm A, et al: Navigation guided resection of temporomandibular joint ankylosis promotes safety in skull base surgery. J Oral Maxillofac Surg 60:1275, 2002 7. Yu HB, Shen GF, Zhang SL, et al: Navigation-guided gap arthroplasty in the treatment of temporomandibular joint ankylosis. Int J Oral Maxillofac Surg 38:1030, 2009
NAVIGATION-GUIDED LATERAL GAP ARTHROPLASTY 8. el-Sheikh MM: Temporomandibular joint ankylosis: The Egyptian experience. Ann R Coll Surg Engl 81:12, 1999 9. Valentini V, Vetrano S, Agrillo A, et al: Surgical treatment of TMJ ankylosis: Our experience (60 cases). J Craniofac Surg 13:59, 2002 10. Matsuura H, Miyamoto H, Ogi N: The effect of gap arthroplasty on temporomandibular joint ankylosis: An experimental study. Int J Oral Maxillofac Surg 30:431, 2001 11. Topazian RG: Gap versus interposition arthroplasty for ankylosis of the temporomandibular joint. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 91:338, 2001 12. Ferretti C, Bryant R, Becker P, et al: Temporomandibular joint morphology following post-traumatic ankylosis in 26 patients. Int J Oral Maxillofac Surg 34:376, 2005 13. Watzinger F, Wanschitz F, Wagner A, et al: Computer-aided navigation in secondary reconstruction of post-traumatic deformities of the zygoma. J Craniomaxillofac Surg 25:68, 1998 14. Klimek L, Wenzel M, Mosges R: Computer-assisted orbital surgery. Ophthal Surg 24:411, 1993 15. Brief J, Edinger D, Hassfeld S, et al: Accuracy of image-guided implantology. Clin Oral Implants Res 16:495, 2005 16. Schmelzeisen R, Gellrich NC, Schoen R, et al: Navigation-aided reconstruction of medial orbital wall and floor contour in cranio-maxillofacial reconstruction. Injury 35:955, 2004 17. Voss PJ, Leow AM, Schulze D, et al: Navigation-guided resection with immediate functional reconstruction for high-grade malignant parotid tumour at skull base. Int J Oral Maxillofac Surg 38: 886, 2009
Navigation-Guided Lateral Gap Arthroplasty as the Treatment of Temporomandibular Joint Ankylosis Haijun Gui, MD, DDS,* Jinyang Wu, DDS,y Steve G. F. Shen, MD, DDS,z Joy S. Bautista, DMD, MHPED,x P. J. Voss, MD, DDS,k and ShiLei Zhang, MD, DDS{ Purpose:
This article presents a novel method of navigation-guided lateral gap arthroplasty (LGA) in the treatment of temporomandibular joint ankylosis (TMJA).
Materials and Methods:
Six patients with unilateral TMJA from 2007 through 2011 were included in this study. Presurgical planning was performed to determine the amount and extent of ankylosed bone to be resected using the simulation platform. Minimum follow-up was 6 months. Patients were monitored for complications and signs of recurrence. Maximum mouth opening (MO) was measured and compared intra- and postoperatively.
Results:
Preoperative planning was performed at the STN or Accu-Navi workstation. The amount and extent of ankylosed bone to be resected was determined. All 6 LGAs were completed successfully using realtime instrument- and pointer-based navigation. Measurements performed intraoperatively showed that the mean for maximum MO was about 35 to 40 mm and remained the same postoperatively. Follow-up evaluation showed remarkable improvement in function and esthetics, with no signs of recurrence.
Conclusion:
Navigation-guided LGA can be regarded a viable option for performing this delicate and complicated surgical procedure. Ó 2014 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 72:128-138, 2014
arily after infection.1 Maxillofacial surgeons encounter numerous TMJAs with medial condylar fragment malunion owing to sagittal condylar fractures and delayed treatment.
Temporomandibular joint ankylosis (TMJA) is a joint disorder that refers to bony or fibrous adhesion of the anatomic joint components and the ensuing loss of function; it occurs mainly after trauma and second-
*Medical Doctor, Department of Oral and Maxillofacial Surgery,
Conflict of Interest Disclosures: None of the authors reported any
Ninth People’s Hospital, affiliated to Shanghai Jiao Tong University
disclosures.
School of Medicine, Shanghai, China.
Address correspondence and reprint requests to Prof Zhang:
yMedical Doctor, Department of Oral and Maxillofacial Surgery,
Shanghai Ninth People’s Hospital, Zhi Zao Ju Road 639, Shanghai,
Ninth People’s Hospital, affiliated to Shanghai Jiao Tong University
People’s Republic of China; e-mail: [email protected]
School of Medicine, Shanghai, China. zProfessor, Department of Oral and Maxillofacial Surgery, Ninth
Received May 16 2013 Accepted July 26 2013
People’s Hospital, affiliated to Shanghai Jiao Tong University
Ó 2014 American Association of Oral and Maxillofacial Surgeons
School of Medicine, Shanghai, China.
0278-2391/13/00951-8$36.00/0
xAssociate Professor, Department of Oral Surgery, University of
http://dx.doi.org/10.1016/j.joms.2013.07.039
the East, College of Dentistry, Manila; Department of Oral and Maxillofacial Surgery, Lung Center of the Philippines, Quezon City, Philippines. kMedical Doctor, Department of Oral and Maxillofacial Surgery, Albert-Ludwigs-University Freiburg, Freiburg, Germany. {Associate Professor, Department of Oral and Maxillofacial Surgery, Ninth People’s Hospital, affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.
128
129
GUI ET AL
FIGURE 1. Case 3. Typical Y-shaped bifid condyle and outer bony fusion in the left temporomandibular joint. Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
The management of TMJA is performed mainly through surgical intervention. Various techniques have been described in the literature.1-4 Lateral gap arthroplasty (LGA), which involves resection of the outer part of the ankylosed bone from the medial condyle malunion, is considered useful in preventing recurrence and promoting rehabilitation of mandibular function.5 However, this delicate surgical procedure poses a great challenge for maxillofacial surgeons because access and visibility inside the TMJ region is arduous and a slight mistake can further destroy the medially displaced condyle. In the treatment of TMJ disease, computerized navigation technology plays an ever-increasing role in procedures, such as resection of tumors and gap arthroplasty.6,7 The aim of this study was to share the authors’ experience in managing 6 patients with TMJA using navigation-guided LGA and evaluate the effectiveness of this procedure.
Materials and Methods From 2007 through 2011, 6 patients (2 male and 4 female) with unilateral TMJA were admitted to the authors’ department (Table 1). Their ages ranged from 17 to 24 years (average mean, 25 yr), and the duration of ankylosis varied from 6 to 36 months before surgical intervention. All 6 affected joints were sec-
ondary to sagittal condylar fractures and met the criteria for type II ankylosis group according to the Sawhney classification.1 The average maximal mouth opening (MO) was 10 mm preoperatively. In the left side, a Y-shaped bifid condyle presented the typical appearance on computed tomographic (CT) scans, and a bony bridge had formed, but was localized to a limited area (Fig 1). Spiral CT datasets (0.625-mm slice thickness; Lightspeed 16, General Electric, London, UK) were acquired for all patients preoperatively. Two navigation systems, the STN system (StrykerLeibinger, Freiburg, Germany)2 and the authors’ Table 1. PATIENTS WITH TYPE II TMJA IN THIS STUDY
Case 1 2 3 4 5 6
Gender/ Age (yr)
Site of TMJA
Duration of Ankylosis (mo)
Navigation System
M/17 F/20 M/30 F/26 F/32 F/30
left right left right left left
12 24 12 6 36 12
STN STN Accu-Navi Accu-Navi STN Accu-Navi
Abbreviations: F, female; M, male; TMJA, temporomandibular joint ankylosis. Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
130
NAVIGATION-GUIDED LATERAL GAP ARTHROPLASTY
FIGURE 2. Case 3. Preoperative plan designed and displayed in different colors. Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
Accu-Navi system (Accu-Navi, UEG, Shanghai, China),3 were used. Each system was used in 3 patients based on the choice of the surgeon. This study was approved by the ethics committee of the same university (Shanghai Jiao Tong University School, Shanghai, China). Patients provided written informed consent. The 2 navigation systems include a navigation workstation and a tracking device. At the workstation, virtual corrections were performed, new anatomic contours for the glenoid fossa were created, and margins for resection were determined (Fig 2). Because all affected joints were unilateral, the mirroring tool was used by superimposing the unaffected side as a reference on the ankylosed side. The amount of ankylosed bone to be resected was determined and displayed in different colors. According to this method, all 6 presurgical plans were achieved and imported into the navigation system for intraoperative navigation.
All patients underwent image-guided LGA under general anesthesia. After registration, an accurate match between the skull and the virtual model was achieved (Fig 3). Access to the TMJ was achieved through a preauricular incision with temporal extension. This was followed by dissection of the superficial layers and freeing of the temporal vessels. The capsule was visualized and the ankylosed joint was exposed. The surgical drill clamping a DRF (Digital Reference Frame) was calibrated to mark the lateral edges of the upper and lower articular surfaces according to the virtual plan (Fig 4A, B). Next, a calibrated saw was used to perform the osteotomy (Fig 4C, D). A probe was used to check the accuracy and ensure a favorable outcome by frequently pinpointing the anatomic landmarks during surgery. After exposing the joint and determining the site of ankylosis, LGA was performed by resecting the outer bony ankylosed tissue and then burring of the glenoid fossa until a gap of at least 10 mm appeared
131
GUI ET AL
FIGURE 3. Case 3. Registration procedure by pinpointing the screws markers implanted in the alveolar bone before computed tomographic data acquisition. Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
between the roof of the fossa and the mandible. The medial condyle malunion was retained. An intraoperative MO of at least 35 mm was achieved. The disc, if found, or the temporalis myofascial flap was sutured to the articular capsule as interpositional material. The postoperative CT image obtained after 1 week was compared with the preoperative CT image. Physiotherapy was advised immediately postoperatively. This is a key element to the success of TMJA management. In addition, MO exercises began as soon as 7 to 10 days later to achieve an optimal MO. The ranges of MO and TMJ function were continually recorded at followups ranging from 6 to 24 months (average, 12 months).
LGA for the 6 ankylosed joints was completed successfully. Burring of the glenoid fossa and the condylar stump created a gap of about 10 mm between the roof of the fossa and the top of the condylar stump. The fractured fragment of the medial condyle remained. An average MO larger than 35 mm was achieved. The postoperative CT image superimposed on the virtual plan showed great congruency, with discrepancies smaller than 0.8 mm (Fig 5). At 6-month follow-up, maximal MO was maintained at 35 to 40 mm (Fig 6A, B, C, D). There were no complications or relapse encountered in the 6 cases (Table 2). Function was restored and all patients were satisfied with the outcome of the procedure.
Results Registration and instrument- and pointer-based navigation were carried out successfully using the STN and Accu-Navi systems intraoperatively, with discrepancies smaller than 0.8 mm. Image-guided
Discussion Management of TMJA is performed mainly through surgical intervention. Treatment modalities can be divided into 3 groups: gap arthroplasty, interpositional
132
NAVIGATION-GUIDED LATERAL GAP ARTHROPLASTY
FIGURE 4. Case 3. Intraoperative instrument-based navigation using multiplanar and 3-dimensional views. A, B, Image-guided calibrated drill for marking the border before resection. (Fig 4 continued on next page.) Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
arthroplasty, and total joint reconstruction using autogenous or alloplastic material.8 The goals for treatment of TMJA include an increase in the range of MO, improvement of mandibular function, decrease in deformity and pain, prevention of recurrence, and allowance for possible growth of the jaw in young patients.9 However, treatment of TMJA poses a significant challenge because of technical difficulties and a high incidence of recurrence. Gap arthroplasty was initially used for the treatment of TMJA. However, ramus height is commonly decreased after osteotomy, leading to malocclusion and exacerbation of micrognathia or hemi-prognathism. According to the literature reviewed, gap arthroplasty can be a frustrating ordeal because recurrence is a major problem, with relapse rates higher than 50%.10,11 According to Ferretti et al,12 a medially dislocated condylar fracture and the remnant disc often can be found in most patients with traumatic TMJA, which was found to be more prone to ankylosis than other condylar fractures. This is consistent with the authors’ experience. In the present study, Y-shaped bifid condyles presented a characteristic appearance on preoperative CT scans, and all discs were identified and
mostly intact. LGA with the remains of the disc and medial condylar fracture was carried out to restore the normal structure of the TMJ and to prevent recurrence. Panoramic radiographs and CT images showed that the ramus height remained the same and ideal reconstruction of the condyle and articular fossa was achieved. The average MO improved remarkably from 7 mm preoperatively to 35 mm intraoperatively and at least 35 mm postoperatively. No recurrence was observed in any case. These results indicate that LGA for restoration of a medial condyle malunion is an effective method for treating type II posttraumatic TMJA. However, LGA may not be applicable to type III and IV ankylosis because the medially positioned remnant of the articular head (smaller than one third the transverse diameter) is not large enough to maintain stable and sustained pressure, often resulting in displacement, absorption, malocclusion, decreased ramus height, etc. CCG (costochondral grafts) should be considered another option for reconstructing the TMJ. Based on the present study, the authors conclude that early release of TMJA, reconstruction of ramus height with medially displaced condylar fracture
133
GUI ET AL
FIGURE 4 (cont’d). (Fig 4 continued on next page.) Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
combined with restoration of the remnant disc or temporalis myofascial flap as an interpositional material, followed by early MO exercise and vigorous physiotherapy is a successful strategy for the management of TMJA. Close follow-up can help identify those patients prone to early recurrence. However, using a conventional surgical technique is challenging when performing LGA because of poor visibility in the deep TMJ region. Any minor mistake could destroy the delicate medial condyle malunion, which should be retained. Accurate preoperative simulation and precise surgical execution are required to produce the optimal outcome. Computerized navigation systems, which allow preoperative simulation and intraoperative visualization, have been described as an effective treatment modality for improving surgical outcome.6,7,13-15 In the present study, the commercial STN navigation
system and the authors’ commercial Accu-Navi navigation system were used. These systems have been introduced into craniofacial surgery and have a proven accuracy of less than 0.1 mm.2,3 To improve visibility and safety, the navigation-guided technique was introduced to assist in the LGA procedure. In patients with TMJA, the ankylosed bone is irregular and has no clear margins, so resecting bone at the skull base is quite difficult. Computer-assisted planning and intraoperative navigation have greatly increased safety in skull base surgery and substantially decreased complications.16,17 For patients with unilateral TMJA, the preoperative plan could be carried out using a mirroring tool and side-to-side comparison. The selected fraction was mirrored from the unaffected side against the deformed side. The new contour was used as the resection margin and intraoperative control during surgery. LGA was
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FIGURE 4 (cont’d). C, D, Image-guided calibrated saw for osteotomy in accord with the virtual plan. (Fig 4 continued on next page.) Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
performed under the guidance of the navigation system so that the medial condyle malunion could be protected against displacement. Consistent with the findings of other groups, navigation-guided technology enabled the execution of LGA more reliably by identifying safety margins, preserving vital struc-
tures, and operating with better visualization of the area. In conclusion, navigation-guided LGA with the remaining ramus height and occlusion showed great benefits for accuracy and safety in this potentially complicated procedure.
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FIGURE 4 (cont’d). Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
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FIGURE 5. The maximal discrepancy was confirmed to be smaller than 0.8 mm by superimposing the postoperative computed tomogram (orange skull) on the preoperative plan (transparent purple part). Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
FIGURE 6. Case 3. Average mouth opening improved significantly from A, 10 mm preoperatively to B, 40 mm intraoperatively and (Fig 6 continued on next page.) Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
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FIGURE 6 (cont’d). C, 38 mm 6 months postoperatively. D, Postoperative effect with resection of outer bony fusion and retention of the medial condyle malunion. Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
Table 2. SUMMARY OF PREOPERATIVE, INTRAOPERATIVE, AND POSTOPERATIVE EXAMINATIONS
Case 1 2 3 4 5 6
Preoperative MO (mm)
Intraoperative MO (mm)
Duration of Follow-Up (mo)
Postoperative MO (mm)
5 6 10 5 8 7
38 35 40 35 40 40
24 12 6 12 6 6
35 35 40 35 40 35
Abbreviation: MO, mouth opening. Gui et al. Navigation-Guided Lateral Gap Arthroplasty. J Oral Maxillofac Surg 2014.
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