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Comparison of bone adaptation after modification in biomet standard alloplastic temporomandibular joint prostheses
Journal of Cranio-Maxillo-Facial Surgery xxx (2018) 1e5
Contents lists available at ScienceDirect
Journal of Cranio-Maxillo-Facial Surgery journal homepage: www.jcmfs.com
Comparison of bone adaptation after modification in biomet standard alloplastic temporomandibular joint prostheses Jieyun Zhao a, b, c, Luxiang Zou a, b, c, Dongmei He a, b, c, *, Edward Ellis III d a
Department of Oral Surgery, Head: Chi Yang, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, No. 639 Zhi Zao Ju Road, Huang Pu District, Shanghai, 200011, China b Shanghai Key Laboratory of Stomatology & Shanghai Research Institute of Stomatology, Head: Zhiyuan Zhang, No. 639 Zhi Zao Ju Road, Huang Pu District, Shanghai, 200011, China c National Clinical Research Center of Stomatology, Head: Zhiyuan Zhang, No. 639 Zhi Zao Ju Road, Huang Pu District, Shanghai, 200011, China d Department of Oral and Maxillofacial Surgery, University of Texas Health Science Center at San Antonio, USA
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 6 April 2018 Accepted 27 July 2018 Available online xxx
Purpose: The aim of the study was to compare bone adaptation after design modification in Biomet stock prostheses. Materials and methods: Computed tomography (CT) data of the patients treated with a Biomet TMJ replacement from 2010 to 2016 were recruited. Fossa prosthesis with a bulge and 4 types of condyleramus angle prostheses were virtually designed and implanted by computer-assisted simulation. The amount of bone trimming including fossa, mandibular ramus and bone graft were measured by ProPlan CMF 1.4 software. The differences between the original and modified prostheses were compared by SPSS 17.0 software for statistical analysis. Results: There were 54 patients’ CT data included in the study. The amount of fossa bone trimming was 150.20 mm3 in the modified prosthesis and 281.82 mm3 in the original one. The amount of ramus bone trimming was 103.86 mm3 in the modified prosthesis and 229.45 mm3 in the original one. The amount of fossa bone grafting was 95.88 mm3 in the modified prosthesis and 263.03 mm3 in the original one. There were significant differences between them (p ¼ 0.000). Conclusions: The modified Biomet prostheses design requires less bone trimming and grafting for implantation. © 2018 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Stock alloplastic prosthesis Temporomandibular joint Bone trimming and graft Computer-assisted simulation
1. Introduction Alloplastic temporomandibular joint (TMJ) replacement is an important method for the treatment of osteoarthritis, ankylosis, condylar tumor and idiopathic condylar resorption. In recent years, total joint prosthesis (TJP) has become a widely used method of TMJ reconstruction. Compared with autologous bone grafts, TJP has no risk of resorption and no need for a donor site (Mercuri, 1998; Mercuri et al., 2008; Wolford et al., 2015). There are two kinds of TJP at present: patient-fitted (TMJ Concepts, Ventura, CA, USA) and stock (Zimmer Biomet, Jacksonville,
* Corresponding author. Department of Oral Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, No. 639 Zhi Zao Ju Road, Huang Pu District, Shanghai 200011, China. Fax: þ86 23271699. E-mail address: [email protected] (D. He).
FL, USA). Patient-fitted prostheses are designed to suit the patient's bone anatomy, which provides better stability and easier implantation (Mercuri, 2012). However, they have a higher cost and a lengthy waiting time for design and manufacture (Mercuri, 1999; Wolford et al., 2003). Stock prosthesis is less expensive and requires no waiting time for fabrication. Although it can match most patients' anatomy, the bone of the patient including both TMJ fossa and mandibular ramus has to be trimmed to fit the prostheses. The Biomet stock prosthesis is the one that is widely used for Western people. It has a flat fossa component design and only two types of condyle-mandibular ramus angle component (normal and offset). While using the Biomet stock prosthesis in 165 TMJs during the past 10 years, we found that some patients need a lot of bone trimmed or bone graft to adjust the condyle-ramus angle for stable prosthesis implantation. We also used bone graft in the fossa to improve the stability of fossa prosthesis (Bai et al., 2014, 2015). This
https://doi.org/10.1016/j.jcms.2018.07.024 1010-5182/© 2018 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Zhao J, et al., Comparison of bone adaptation after modification in biomet standard alloplastic temporomandibular joint prostheses, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.07.024
2
J. Zhao et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2018) 1e5
could increase operative trauma and time. By measuring 700 Chinese TMJs from CT scans and cluster analysis, we found there were 4 types of condyle-ramus angle (Zhang et al., 2016). Thus, in this study, we intended to modify the Biomet ramus prosthesis angle into these 4 types and also to design a bulge for the fossa prosthesis to avoid bone graft in the fossa. The purpose of this study was to compare bone adaptation between the modified Biomet stock prostheses with the original one by computer-assisted implantation simulation in TJP patients. 2. Materials and methods 2.1. Case selection This is a retrospective study that was approved by the local ethics board of the hospital. CT data of the patients treated by TJP from January 2010 to December 2016 were recruited for the study. The criteria for inclusion were age >18 years, and diagnosis of osteoarthritis or idiopathic condylar resorption (ICR). Patients diagnosed with TMJ ankylosis, condylar tumor or failed autogenous bone graft were excluded from the study. 2.2. Prosthesis modification and 3D reconstruction Four types of condyle-ramus angle were selected according to our previous study (Zhang et al., 2016) to compare with the mostly used condyle-ramus angle of Biomet prosthesis. CT data of the patients were imported into the ProPlan CMF 1.4 software (Materialize, Leuven, Belgium) for three-dimensional (3D) reconstruction of the skull. The maxilla and mandible were separated by CT sagittal image and labeled with different colors. The fossa prosthesis was placed parallel to the Frankfort horizontal plane and its posterior rim kept an appropriate distance from the external auditory canal. The wing of the prosthesis was positioned along the root of the zygomatic arch to guarantee quality bone for fixation. In lieu of reducing the articular eminence performed by most surgeons, we prefer to remove the eminence with a sagittal saw and to use it as a graft in the fossa (Bai et al., 2015). In the modified Biomet fossa prosthesis, a bulge was designed to fill the space in the remnant fossa (Fig. 1A). The next step in the process involved virtual positioning of the ramus prosthesis. The ramus was positioned with the condyle in the most posterosuperior portion of the fossa and tilted such that the fixation screws would be positioned away from the inferior alveolar neurovascular bundle (Bai et al., 2015) (Fig. 1B). The height of the mandibular ramus and the inclination of the condyle were measured for the selection of a modified Biomet prosthesis. The sizes of two types of prostheses were selected according to the patients’ skeletal anatomy and implanted by simulation for the following measurements: 1) Fossa bone trimming: The volume of the bone trimmed for implantation of the fossa component (Fig. 2). A volume less than 150 mm3 is defined as a small amount of bone trimming; 150 mm3e300 mm3 as a medium amount of bone trimming; and more than 300 mm3 as a large amount of bone trimming. 2) Mandibular ramus trimming: Bony interference of the ramus to ideal prosthesis placement was trimmed for implantation of the ramus component (Fig. 3). A volume less than 150 mm3 was regarded as a small amount of bone trimming; 150 mm3e300 mm3 as a medium amount of bone trimming; and more than 300 mm3 as a large amount of bone trimming. 3) Fossa bone graft: The volume of bone graft between the fossa and the prosthesis (Fig. 1A). A volume less than 100 mm3 is defined as a small amount of bone grafting; 100 mm3e300 mm3
Fig. 1. Implantation and bone trimming of the prostheses. (A) Fossa prosthesis implantation and bone graft/bulge (red color). (B) Ramus prosthesis implantation and overlapped bone trimming (red color).
as a medium amount of bone grafting; and more than 300 mm3 as a large amount of bone grafting. 4) Location of the ramus trimming: The location of the ramus trimming has been compared between the two prostheses systems.
2.3. Statistical analysis The bone triming of the fossa, mandibular ramus, and the fossa bone graft of the two types of TJP were compared using paired t-test in the Statistical Package for Social Sciences software package, version 17.0 (SPSS Inc., Chicago, IL, USA). One-way analysis of variance was used to compare the amount of bone trimming and graft between the two types of TJP, and an a level of 0.05 was considered significant. The distribution proportions were compared using a Chi square test, and an a level of 0.05 was considered significant.
3. Results CT data of the 54 patients (63 TMJs) treated with TJP were included in the study. There were 7 males and 47 females, whose ages ranged from 26 to 76 years (mean age 53.8 years). The duration of the disease was 0.25e40 years (mean 3.9 years). There were 51 patients diagnosed with osteoarthritis (94.4%) and 3 patients with idiopathic condylar resorption (5.6%). The size distribution of the two types of prostheses was as follows: 1) Biomet system: The small fossa component was used for all fossae; and the ramus component was selected according to the
Please cite this article in press as: Zhao J, et al., Comparison of bone adaptation after modification in biomet standard alloplastic temporomandibular joint prostheses, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.07.024
J. Zhao et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2018) 1e5
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medium amount of bone trimming and 29% required a large amount of bone trimming. In the computer-modified Biomet system, 84% needed little or no bone trimming, 16% needed a medium amount of bone trimming and no TMJ required a large amount of bone trimming (Table 3). The distribution of the amount of fossa bone graft between the two systems were as follows: In the Biomet system, 21% needed a little amount of bone graft, 44% needed a medium amount of bone graft, 35% required a large amount of bone graft; in the computer modified Biomet system, 62% needed little or no bone graft, 38% needed a medium amount of bone grafting, and there was no need for a large amount of bone graft (Table 4). The main location of bone trimming in the TMJ fossa was the lateral side of the articular eminence and condylar neck in the mandibular ramus to assist with prosthesis positioning. In the Biomet system, 77.8% of the rami required bone trimming with an average amount of 1.49 mm; in the computer-modified Biomet system, 33.3% required trimming with an average of 1.18 mm. 4. Discussion
Fig. 2. Fossa bone trimming of the protheses. (A) Volume of Biomet fossa bone trimming. (B) Volume of modified Biomet fossa bone trimming.
ramus height, as small in 32 sides (50.8%), medium in 15 sides (23.8%) and large in 16 sides (25.4%). 2) Computer-modified Biomet system: The small fossa component was used for all fossae. The mandibular prosthesis was selected according to both the ramus height and the condyle-ramus angles, as type I in 8 sides (12.7%), type II in 38 sides (60.3%), type III in 15 sides (23.8%), and type IV in 2 sides (3.2%). The mean amount of fossa bone trimming was 150.20 mm3 in the computer-modified Biomet prosthesis and 281.82 mm3 in the original Biomet system. The mean amount of mandibular ramus bone trimming was 103.86 mm3 in the compute-modified Biomet prosthesis and 229.45 mm3 in the original Biomet system. The mean volume of fossa bone graft was 95.88 mm3 in the computermodified Biomet prosthesis and 263.03 mm3 in the original Biomet system. There were significant differences between the two systems (p < 0.001) (Table 1). According to the 3D reconstruction and the analogue simulation, the distribution of the amount of fossa bone trimming in the 54 patients with 63 joints between the two systems were as follows: In the Biomet system, 21% needed little or no fossa bone trimming, 46% needed a medium amount of bone trimming and 33% required a large amount of bone trimming. In the computermodified Biomet system, 67% needed a little or no bone trimming, 25% need a medium amount of bone trimming and 8% required large amount of bone trimming (Table 2). The distribution of the amount of mandibular ramus bone trimming between the two systems were as follows: In the Biomet system, 44% needed little or no bone trimming, 27% needed a
Over 50 years, there have been more types of TMJ prosthesis in the market such as Christensen, Vitek-Kent, W-Lorenz, and others. Most dropped out of the market because of inappropriate design and materials with fast wear rate and debris that caused failure of the device. Hemiarthroplasty or partial joint reconstuction such as fossa or condylar component, which, against natural condyle or fossa, has disadvantages including bone resorption and progressive occlusal changes (Quinn, Granquist, 2015). Now there are two TJR systems on the market: 1) Zimmer Biomet (Warsaw, IN, USA) stock TMJ replacement system; and 2) TMJ Concepts (Ventura, CA, USA) patient-fitted TMJ replacement system. Although individualized products are much easier to implant than stock ones, the patientspecific joints have a higher cost and require a longer time for manufacture. Stock products have the advantages of immediate availability, single-stage surgery, no requirement for recapitulation from a stereolithic model, and lower cost. The Zimmer Biomet system is the only product currently approved for TJP in China. We used hemiarthroplasty or partial joint reconstruction before but had a high revision rate. After using Biomet TJP since 2006 in our department, 133 patients with 165 joints underwent successful implantation, with long-time stability. However, it is difficult, especially for inexperienced surgeons, to implant the flat bone contact stock prostheses on a rocky bone. Where and how much to trim the bone are unclear. In recent years, computer-assisted surgery (CAS) has been widely used and has greatly improved operative accuracy and safety (Hassfeld, Mühling, 2001). By simulation, the size of the prostheses can be chosen, and the area of bone trimming and grafting can be planned by digital templates (Bai et al., 2014; Chandran et al., 2011). In that way, the stock prostheses can be implanted depending on individual situations with guidance of digital templates and can match each patient better. After applying 165 Biomet prostheses, we thought that bone trimming and graft may be reduced if there are more types of condyle-ramus angle prostheses in which one closer to the patient's anatomy can be chosen. According to CT measurements and a cluster analysis of TMJs anatomy (Zhang et al., 2016), we modified the condyle-ramus angle of Biomet prosthesis into 4 types, and also put a bulge on the Biomet fossa prosthesis to avoid bone graft in the fossa by computer-assisted design. The bone adaptation between the modified and original Biomet prostheses was compared by computer-assisted implantation simulation. The results showd that 67% of computer-modified Biomet fossa prostheses had no need for bone trimming or grafting, whereas 79% of Zimmer Biomet fossa prostheses needed bone trimming and grafting. This makes the
Please cite this article in press as: Zhao J, et al., Comparison of bone adaptation after modification in biomet standard alloplastic temporomandibular joint prostheses, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.07.024
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Fig. 3. Ramus bone trimming of the protheses. (A) Volume of Biomet ramus bone trimming. (B) Volume of modified Biomet ramus bone trimming.
Table 1 Comparison of the amount of bone trimming between the two systems (mm3).
Fossa bone trimming Mandible ramus bone trimming Fossa bone grafting *
Biomet
Modified Biomet
281.82 ± 188.26* 229.45 ± 159.35# 263.03 ± 187.00^
150.20 ± 125.86* 103.86 ± 64.07# 95.88 ± 74.72^
p ¼ 0.000, #p ¼ 0.000, ^p ¼ 0.000.
computer-modified Biomet fossa prosthesis easier to position with greater stability. We also used computer-assisted simulation to choose the suitable size of both the Zimmer Biomet and computermodified Biomet prostheses according to the patient's anatomy. By comparing the amount of bone trimming and grafting between the two types of prostheses, computer-modified Biomet prostheses
required less bone trimming and no need for fossa bone grafting as compared to the Zimmer Biomet prostheses. This is because we designed four types of condyle-ramus angle according to the cluster analysis of TMJ anatomy. Different from the Zimmer Biomet stock system with the only fixed invariable ramus-condylar angle, the computer-modified Biomet prostheses can fit the bone better which significantly decreased the mandibular ramus bone trimming and the risk of alveolar nerve injury. The Type II computer-modified Biomet ramus component had a similar ramus-condylar angle to that of the Zimmer Biomet system. In this study, we found that 60.3% of the TMJs were suitable for the Type II computer-modified Biomet prosthesis, 23.8% were suitable for the Type III prosthesis, 12.7% were suitable for the Type I and 3.2% were suitable for the Type IV. Of the TMJs, 29% required large amounts of bone trimming for the Zimmer Biomet prosthesis,
Please cite this article in press as: Zhao J, et al., Comparison of bone adaptation after modification in biomet standard alloplastic temporomandibular joint prostheses, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.07.024
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Table 2 Distribution of the amount of fossa bone trimming between the two systems (mm3).
Small amount of bone trimming (<150 mm3) Medium amount of bone trimming (150 mm3e300 mm3) Large amount of bone trimming (>300 mm3)
Biomet
Modified Biomet
13 (21%) 29 (46%) 21 (33%)
42 (67%) 16 (25%) 5 (8%)
p ¼ 0.000.
Table 3 Distribution of the amount of mandible ramus bone trimming between the two systems (mm3).
3
Small amount of bone trimming (<150 mm ) Medium amount of bone trimming (150 mm3e300 mm3) Large amount of bone trimming (>300 mm3)
Biomet
Modified Biomet
28 (44%) 17 (27%) 18 (29%)
53 (84%) 10 (16%) 0
p ¼ 0.000.
Table 4 Distribution of the amount of fossa bone graft between the two systems (mm3).
Small amount of bone grafting (<100 mm3) Medium amount of bone grafting (100 mm3e300 mm3) Large amount of bone grafting (>300 mm3)
Biomet
Modified Biomet
13 (21%) 28 (44%) 22 (35%)
39 (62%) 24 (38%) 0
p ¼ 0.000.
whereas no patients needed large bone trimming for the computermodified Biomet prosthesis. The remarkable advantages of the modified TJP in this study compared to the custom prosthesis is that modified TJP is very similar to the custom prosthesis, which needs little bone trimming for implantation but can be immediately available for use without waiting before the operation and at a lower price. It is also very easy for surgeons to use. 5. Conclusion The computer-modified Biomet prosthesis requires less bone trimming and no bone grafting than the original Biomet prosthesis. It may reduce the risk of injury to the skull base and inferior alveolar nerve, and save operation time. Conflicts of interest The authors declare no conflict of interest. Acknowledgements This study was supported by grants from the National Natural Science Foundation of China (81472117), the Fund of Medicine and Engineering Interdisciplinary Program of Shanghai Jiao Tong University (YG2014MS05), the Science and Technology Commission of Shanghai Municipality Science Research Project (17441900300), Shanghai Shen Kang Medical Development Fund (16CR3045A) and Eleventh college students innovation training project of Shanghai Jiao Tong University School of Medicine (1117591).
References Bai G, He D, Yang C, Chen M, Yuan J, Wilson JJ: Application of digital templates to guide total alloplastic joint replacement surgery with biomet standard replacement system. J Oral Maxillofac Surg 72: 2440e2452, 2014 Bai G, Yang C, He D, Zhang X, Abdelrehem A: Application of fossa bone graft to stabilize stock total joint prosthesis in temporomandibular joint surgery. J Craniomaxillofac Surg 43: 1392e1397, 2015 Chandran R, Keeler GD, Christensen AM, Weimer KA, Caloss R: Application of virtual surgical planning for total joint reconstruction with a stock alloplast system. J Oral Maxillofac Surg 69: 285e294, 2011 Hassfeld S, Mühling J: Computer assisted oral and maxillofacial surgeryea review and an assessment of technology. Int J Oral Maxillofac Surg 30: 2e13, 2001 Mercuri LG: Alloplastic temporomandibular joint reconstruction [Review]. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 85: 631e637, 1998 Mercuri LG: Subjective and objective outcomes in patients reconstructed with a custom-fitted alloplastic temporomandibular joint prosthesis. J Oral Maxillofac Surg 57: 1427e1430, 1999 Mercuri LG, Ali FA, Woolson R: Outcomes of total alloplastic replacement with periarticular autogenous fat grafting for management of reankylosis of the temporomandibular joint. J Oral Maxillofac Surg 66: 1794e1803, 2008 Mercuri LG: Alloplastic temporomandibular joint replacement: rationale for the use of custom devices [Review]. Int J Oral Maxillofac Surg 41: 1033e1040, 2012 Quinn P, Granquist EJ: Stock alloplastic reconstruction of the temporomandibular joint. Atlas of temporomandibular joint surgery. 2nd ed, vol. 157. Ames, IA: Wiley Blackwell, 2015 Wolford LM, Pitta MC, Reiche-Fischel O, Franco PF: TMJ Concepts/Techmedica custom-made TMJ total joint prosthesis: 5-year follow-up study. Int J Oral Maxillofac Surg 32: 268e274, 2003 Wolford LM, Mercuri LG, Schneiderman ED, Movahed R, Allen W: Twenty-year follow-up study on a patient-fitted temporomandibular joint prosthesis: the Techmedica/TMJ Concepts device. J Oral Maxillofac Surg 73: 952e960, 2015 Zhang LZ, Meng SS, He DM, Fu YZ, Liu T, Wang FY, et al: Three-dimensional measurement and cluster analysis for determining the size ranges of Chinese temporomandibular joint replacement prosthesis. Medicine (Baltimore) 95: e2897, 2016
Please cite this article in press as: Zhao J, et al., Comparison of bone adaptation after modification in biomet standard alloplastic temporomandibular joint prostheses, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.07.024
Contents lists available at ScienceDirect
Journal of Cranio-Maxillo-Facial Surgery journal homepage: www.jcmfs.com
Comparison of bone adaptation after modification in biomet standard alloplastic temporomandibular joint prostheses Jieyun Zhao a, b, c, Luxiang Zou a, b, c, Dongmei He a, b, c, *, Edward Ellis III d a
Department of Oral Surgery, Head: Chi Yang, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, No. 639 Zhi Zao Ju Road, Huang Pu District, Shanghai, 200011, China b Shanghai Key Laboratory of Stomatology & Shanghai Research Institute of Stomatology, Head: Zhiyuan Zhang, No. 639 Zhi Zao Ju Road, Huang Pu District, Shanghai, 200011, China c National Clinical Research Center of Stomatology, Head: Zhiyuan Zhang, No. 639 Zhi Zao Ju Road, Huang Pu District, Shanghai, 200011, China d Department of Oral and Maxillofacial Surgery, University of Texas Health Science Center at San Antonio, USA
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 6 April 2018 Accepted 27 July 2018 Available online xxx
Purpose: The aim of the study was to compare bone adaptation after design modification in Biomet stock prostheses. Materials and methods: Computed tomography (CT) data of the patients treated with a Biomet TMJ replacement from 2010 to 2016 were recruited. Fossa prosthesis with a bulge and 4 types of condyleramus angle prostheses were virtually designed and implanted by computer-assisted simulation. The amount of bone trimming including fossa, mandibular ramus and bone graft were measured by ProPlan CMF 1.4 software. The differences between the original and modified prostheses were compared by SPSS 17.0 software for statistical analysis. Results: There were 54 patients’ CT data included in the study. The amount of fossa bone trimming was 150.20 mm3 in the modified prosthesis and 281.82 mm3 in the original one. The amount of ramus bone trimming was 103.86 mm3 in the modified prosthesis and 229.45 mm3 in the original one. The amount of fossa bone grafting was 95.88 mm3 in the modified prosthesis and 263.03 mm3 in the original one. There were significant differences between them (p ¼ 0.000). Conclusions: The modified Biomet prostheses design requires less bone trimming and grafting for implantation. © 2018 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Stock alloplastic prosthesis Temporomandibular joint Bone trimming and graft Computer-assisted simulation
1. Introduction Alloplastic temporomandibular joint (TMJ) replacement is an important method for the treatment of osteoarthritis, ankylosis, condylar tumor and idiopathic condylar resorption. In recent years, total joint prosthesis (TJP) has become a widely used method of TMJ reconstruction. Compared with autologous bone grafts, TJP has no risk of resorption and no need for a donor site (Mercuri, 1998; Mercuri et al., 2008; Wolford et al., 2015). There are two kinds of TJP at present: patient-fitted (TMJ Concepts, Ventura, CA, USA) and stock (Zimmer Biomet, Jacksonville,
* Corresponding author. Department of Oral Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, No. 639 Zhi Zao Ju Road, Huang Pu District, Shanghai 200011, China. Fax: þ86 23271699. E-mail address: [email protected] (D. He).
FL, USA). Patient-fitted prostheses are designed to suit the patient's bone anatomy, which provides better stability and easier implantation (Mercuri, 2012). However, they have a higher cost and a lengthy waiting time for design and manufacture (Mercuri, 1999; Wolford et al., 2003). Stock prosthesis is less expensive and requires no waiting time for fabrication. Although it can match most patients' anatomy, the bone of the patient including both TMJ fossa and mandibular ramus has to be trimmed to fit the prostheses. The Biomet stock prosthesis is the one that is widely used for Western people. It has a flat fossa component design and only two types of condyle-mandibular ramus angle component (normal and offset). While using the Biomet stock prosthesis in 165 TMJs during the past 10 years, we found that some patients need a lot of bone trimmed or bone graft to adjust the condyle-ramus angle for stable prosthesis implantation. We also used bone graft in the fossa to improve the stability of fossa prosthesis (Bai et al., 2014, 2015). This
https://doi.org/10.1016/j.jcms.2018.07.024 1010-5182/© 2018 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Zhao J, et al., Comparison of bone adaptation after modification in biomet standard alloplastic temporomandibular joint prostheses, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.07.024
2
J. Zhao et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2018) 1e5
could increase operative trauma and time. By measuring 700 Chinese TMJs from CT scans and cluster analysis, we found there were 4 types of condyle-ramus angle (Zhang et al., 2016). Thus, in this study, we intended to modify the Biomet ramus prosthesis angle into these 4 types and also to design a bulge for the fossa prosthesis to avoid bone graft in the fossa. The purpose of this study was to compare bone adaptation between the modified Biomet stock prostheses with the original one by computer-assisted implantation simulation in TJP patients. 2. Materials and methods 2.1. Case selection This is a retrospective study that was approved by the local ethics board of the hospital. CT data of the patients treated by TJP from January 2010 to December 2016 were recruited for the study. The criteria for inclusion were age >18 years, and diagnosis of osteoarthritis or idiopathic condylar resorption (ICR). Patients diagnosed with TMJ ankylosis, condylar tumor or failed autogenous bone graft were excluded from the study. 2.2. Prosthesis modification and 3D reconstruction Four types of condyle-ramus angle were selected according to our previous study (Zhang et al., 2016) to compare with the mostly used condyle-ramus angle of Biomet prosthesis. CT data of the patients were imported into the ProPlan CMF 1.4 software (Materialize, Leuven, Belgium) for three-dimensional (3D) reconstruction of the skull. The maxilla and mandible were separated by CT sagittal image and labeled with different colors. The fossa prosthesis was placed parallel to the Frankfort horizontal plane and its posterior rim kept an appropriate distance from the external auditory canal. The wing of the prosthesis was positioned along the root of the zygomatic arch to guarantee quality bone for fixation. In lieu of reducing the articular eminence performed by most surgeons, we prefer to remove the eminence with a sagittal saw and to use it as a graft in the fossa (Bai et al., 2015). In the modified Biomet fossa prosthesis, a bulge was designed to fill the space in the remnant fossa (Fig. 1A). The next step in the process involved virtual positioning of the ramus prosthesis. The ramus was positioned with the condyle in the most posterosuperior portion of the fossa and tilted such that the fixation screws would be positioned away from the inferior alveolar neurovascular bundle (Bai et al., 2015) (Fig. 1B). The height of the mandibular ramus and the inclination of the condyle were measured for the selection of a modified Biomet prosthesis. The sizes of two types of prostheses were selected according to the patients’ skeletal anatomy and implanted by simulation for the following measurements: 1) Fossa bone trimming: The volume of the bone trimmed for implantation of the fossa component (Fig. 2). A volume less than 150 mm3 is defined as a small amount of bone trimming; 150 mm3e300 mm3 as a medium amount of bone trimming; and more than 300 mm3 as a large amount of bone trimming. 2) Mandibular ramus trimming: Bony interference of the ramus to ideal prosthesis placement was trimmed for implantation of the ramus component (Fig. 3). A volume less than 150 mm3 was regarded as a small amount of bone trimming; 150 mm3e300 mm3 as a medium amount of bone trimming; and more than 300 mm3 as a large amount of bone trimming. 3) Fossa bone graft: The volume of bone graft between the fossa and the prosthesis (Fig. 1A). A volume less than 100 mm3 is defined as a small amount of bone grafting; 100 mm3e300 mm3
Fig. 1. Implantation and bone trimming of the prostheses. (A) Fossa prosthesis implantation and bone graft/bulge (red color). (B) Ramus prosthesis implantation and overlapped bone trimming (red color).
as a medium amount of bone grafting; and more than 300 mm3 as a large amount of bone grafting. 4) Location of the ramus trimming: The location of the ramus trimming has been compared between the two prostheses systems.
2.3. Statistical analysis The bone triming of the fossa, mandibular ramus, and the fossa bone graft of the two types of TJP were compared using paired t-test in the Statistical Package for Social Sciences software package, version 17.0 (SPSS Inc., Chicago, IL, USA). One-way analysis of variance was used to compare the amount of bone trimming and graft between the two types of TJP, and an a level of 0.05 was considered significant. The distribution proportions were compared using a Chi square test, and an a level of 0.05 was considered significant.
3. Results CT data of the 54 patients (63 TMJs) treated with TJP were included in the study. There were 7 males and 47 females, whose ages ranged from 26 to 76 years (mean age 53.8 years). The duration of the disease was 0.25e40 years (mean 3.9 years). There were 51 patients diagnosed with osteoarthritis (94.4%) and 3 patients with idiopathic condylar resorption (5.6%). The size distribution of the two types of prostheses was as follows: 1) Biomet system: The small fossa component was used for all fossae; and the ramus component was selected according to the
Please cite this article in press as: Zhao J, et al., Comparison of bone adaptation after modification in biomet standard alloplastic temporomandibular joint prostheses, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.07.024
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medium amount of bone trimming and 29% required a large amount of bone trimming. In the computer-modified Biomet system, 84% needed little or no bone trimming, 16% needed a medium amount of bone trimming and no TMJ required a large amount of bone trimming (Table 3). The distribution of the amount of fossa bone graft between the two systems were as follows: In the Biomet system, 21% needed a little amount of bone graft, 44% needed a medium amount of bone graft, 35% required a large amount of bone graft; in the computer modified Biomet system, 62% needed little or no bone graft, 38% needed a medium amount of bone grafting, and there was no need for a large amount of bone graft (Table 4). The main location of bone trimming in the TMJ fossa was the lateral side of the articular eminence and condylar neck in the mandibular ramus to assist with prosthesis positioning. In the Biomet system, 77.8% of the rami required bone trimming with an average amount of 1.49 mm; in the computer-modified Biomet system, 33.3% required trimming with an average of 1.18 mm. 4. Discussion
Fig. 2. Fossa bone trimming of the protheses. (A) Volume of Biomet fossa bone trimming. (B) Volume of modified Biomet fossa bone trimming.
ramus height, as small in 32 sides (50.8%), medium in 15 sides (23.8%) and large in 16 sides (25.4%). 2) Computer-modified Biomet system: The small fossa component was used for all fossae. The mandibular prosthesis was selected according to both the ramus height and the condyle-ramus angles, as type I in 8 sides (12.7%), type II in 38 sides (60.3%), type III in 15 sides (23.8%), and type IV in 2 sides (3.2%). The mean amount of fossa bone trimming was 150.20 mm3 in the computer-modified Biomet prosthesis and 281.82 mm3 in the original Biomet system. The mean amount of mandibular ramus bone trimming was 103.86 mm3 in the compute-modified Biomet prosthesis and 229.45 mm3 in the original Biomet system. The mean volume of fossa bone graft was 95.88 mm3 in the computermodified Biomet prosthesis and 263.03 mm3 in the original Biomet system. There were significant differences between the two systems (p < 0.001) (Table 1). According to the 3D reconstruction and the analogue simulation, the distribution of the amount of fossa bone trimming in the 54 patients with 63 joints between the two systems were as follows: In the Biomet system, 21% needed little or no fossa bone trimming, 46% needed a medium amount of bone trimming and 33% required a large amount of bone trimming. In the computermodified Biomet system, 67% needed a little or no bone trimming, 25% need a medium amount of bone trimming and 8% required large amount of bone trimming (Table 2). The distribution of the amount of mandibular ramus bone trimming between the two systems were as follows: In the Biomet system, 44% needed little or no bone trimming, 27% needed a
Over 50 years, there have been more types of TMJ prosthesis in the market such as Christensen, Vitek-Kent, W-Lorenz, and others. Most dropped out of the market because of inappropriate design and materials with fast wear rate and debris that caused failure of the device. Hemiarthroplasty or partial joint reconstuction such as fossa or condylar component, which, against natural condyle or fossa, has disadvantages including bone resorption and progressive occlusal changes (Quinn, Granquist, 2015). Now there are two TJR systems on the market: 1) Zimmer Biomet (Warsaw, IN, USA) stock TMJ replacement system; and 2) TMJ Concepts (Ventura, CA, USA) patient-fitted TMJ replacement system. Although individualized products are much easier to implant than stock ones, the patientspecific joints have a higher cost and require a longer time for manufacture. Stock products have the advantages of immediate availability, single-stage surgery, no requirement for recapitulation from a stereolithic model, and lower cost. The Zimmer Biomet system is the only product currently approved for TJP in China. We used hemiarthroplasty or partial joint reconstruction before but had a high revision rate. After using Biomet TJP since 2006 in our department, 133 patients with 165 joints underwent successful implantation, with long-time stability. However, it is difficult, especially for inexperienced surgeons, to implant the flat bone contact stock prostheses on a rocky bone. Where and how much to trim the bone are unclear. In recent years, computer-assisted surgery (CAS) has been widely used and has greatly improved operative accuracy and safety (Hassfeld, Mühling, 2001). By simulation, the size of the prostheses can be chosen, and the area of bone trimming and grafting can be planned by digital templates (Bai et al., 2014; Chandran et al., 2011). In that way, the stock prostheses can be implanted depending on individual situations with guidance of digital templates and can match each patient better. After applying 165 Biomet prostheses, we thought that bone trimming and graft may be reduced if there are more types of condyle-ramus angle prostheses in which one closer to the patient's anatomy can be chosen. According to CT measurements and a cluster analysis of TMJs anatomy (Zhang et al., 2016), we modified the condyle-ramus angle of Biomet prosthesis into 4 types, and also put a bulge on the Biomet fossa prosthesis to avoid bone graft in the fossa by computer-assisted design. The bone adaptation between the modified and original Biomet prostheses was compared by computer-assisted implantation simulation. The results showd that 67% of computer-modified Biomet fossa prostheses had no need for bone trimming or grafting, whereas 79% of Zimmer Biomet fossa prostheses needed bone trimming and grafting. This makes the
Please cite this article in press as: Zhao J, et al., Comparison of bone adaptation after modification in biomet standard alloplastic temporomandibular joint prostheses, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.07.024
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J. Zhao et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2018) 1e5
Fig. 3. Ramus bone trimming of the protheses. (A) Volume of Biomet ramus bone trimming. (B) Volume of modified Biomet ramus bone trimming.
Table 1 Comparison of the amount of bone trimming between the two systems (mm3).
Fossa bone trimming Mandible ramus bone trimming Fossa bone grafting *
Biomet
Modified Biomet
281.82 ± 188.26* 229.45 ± 159.35# 263.03 ± 187.00^
150.20 ± 125.86* 103.86 ± 64.07# 95.88 ± 74.72^
p ¼ 0.000, #p ¼ 0.000, ^p ¼ 0.000.
computer-modified Biomet fossa prosthesis easier to position with greater stability. We also used computer-assisted simulation to choose the suitable size of both the Zimmer Biomet and computermodified Biomet prostheses according to the patient's anatomy. By comparing the amount of bone trimming and grafting between the two types of prostheses, computer-modified Biomet prostheses
required less bone trimming and no need for fossa bone grafting as compared to the Zimmer Biomet prostheses. This is because we designed four types of condyle-ramus angle according to the cluster analysis of TMJ anatomy. Different from the Zimmer Biomet stock system with the only fixed invariable ramus-condylar angle, the computer-modified Biomet prostheses can fit the bone better which significantly decreased the mandibular ramus bone trimming and the risk of alveolar nerve injury. The Type II computer-modified Biomet ramus component had a similar ramus-condylar angle to that of the Zimmer Biomet system. In this study, we found that 60.3% of the TMJs were suitable for the Type II computer-modified Biomet prosthesis, 23.8% were suitable for the Type III prosthesis, 12.7% were suitable for the Type I and 3.2% were suitable for the Type IV. Of the TMJs, 29% required large amounts of bone trimming for the Zimmer Biomet prosthesis,
Please cite this article in press as: Zhao J, et al., Comparison of bone adaptation after modification in biomet standard alloplastic temporomandibular joint prostheses, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.07.024
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Table 2 Distribution of the amount of fossa bone trimming between the two systems (mm3).
Small amount of bone trimming (<150 mm3) Medium amount of bone trimming (150 mm3e300 mm3) Large amount of bone trimming (>300 mm3)
Biomet
Modified Biomet
13 (21%) 29 (46%) 21 (33%)
42 (67%) 16 (25%) 5 (8%)
p ¼ 0.000.
Table 3 Distribution of the amount of mandible ramus bone trimming between the two systems (mm3).
3
Small amount of bone trimming (<150 mm ) Medium amount of bone trimming (150 mm3e300 mm3) Large amount of bone trimming (>300 mm3)
Biomet
Modified Biomet
28 (44%) 17 (27%) 18 (29%)
53 (84%) 10 (16%) 0
p ¼ 0.000.
Table 4 Distribution of the amount of fossa bone graft between the two systems (mm3).
Small amount of bone grafting (<100 mm3) Medium amount of bone grafting (100 mm3e300 mm3) Large amount of bone grafting (>300 mm3)
Biomet
Modified Biomet
13 (21%) 28 (44%) 22 (35%)
39 (62%) 24 (38%) 0
p ¼ 0.000.
whereas no patients needed large bone trimming for the computermodified Biomet prosthesis. The remarkable advantages of the modified TJP in this study compared to the custom prosthesis is that modified TJP is very similar to the custom prosthesis, which needs little bone trimming for implantation but can be immediately available for use without waiting before the operation and at a lower price. It is also very easy for surgeons to use. 5. Conclusion The computer-modified Biomet prosthesis requires less bone trimming and no bone grafting than the original Biomet prosthesis. It may reduce the risk of injury to the skull base and inferior alveolar nerve, and save operation time. Conflicts of interest The authors declare no conflict of interest. Acknowledgements This study was supported by grants from the National Natural Science Foundation of China (81472117), the Fund of Medicine and Engineering Interdisciplinary Program of Shanghai Jiao Tong University (YG2014MS05), the Science and Technology Commission of Shanghai Municipality Science Research Project (17441900300), Shanghai Shen Kang Medical Development Fund (16CR3045A) and Eleventh college students innovation training project of Shanghai Jiao Tong University School of Medicine (1117591).
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Please cite this article in press as: Zhao J, et al., Comparison of bone adaptation after modification in biomet standard alloplastic temporomandibular joint prostheses, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.07.024