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Stability study of total temporomandibular joint replacement on sheep
Journal of Cranio-Maxillo-Facial Surgery xxx (2014) 1e6
Contents lists available at ScienceDirect
Journal of Cranio-Maxillo-Facial Surgery journal homepage: www.jcmfs.com
Stability study of total temporomandibular joint replacement on sheep Pei Shen, Shan Yong Zhang*, Chi Yang, Bai Yun Department of Oral Surgery, Ninth People’s Hospital, College of Stomatology, Shanghai Jiao Tong University School of Medicine, Shanghai Key Laboratory of Stomatology & Shanghai Research Institute of Stomatology, No. 639, ZhiZaoJu Rd, 200011 Shanghai, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 25 July 2013 Accepted 10 March 2014
Objective: To evaluate the stability of our custom-made prosthesis by establishing the model of sheep total temporomandibular joint (TMJ) replacement. Methods: Six sheep were included in our study. Spiral computed tomography (CT) data of all sheep was obtained and transformed into 3-dimensional model by surgicase5.0 software preoperatively. Total TMJ prostheses were made based on the skull model. Ultra-high molecular weight polyethylene was used to make glenoid fossa lining, while titanium alloy to prefabricate mandibular retention handle and titanium plate over glenoid fossa. Cobalt-chromium-molybdenum alloy was also used to prefabricate the condyle. The right sides of all sheep, as the experimental group, were carried out total TMJ replacement, while the left sides were as the control group. The bone in both experimental and control side were excised after 3 and 6 months. Scanning electron microscope (SEM) was used to observe the interface between bone and prosthesis. Van Gieson staining and immunohistochemical staining (IHC) were used respectively to observe the interface of titanium screw and bone and the expression of alkaline phosphatase (ALP). Results: SEM and Van Gieson staining showed that there was immature bone and osteoid formed in the interface of prosthesis and bone after 3 months. While after 6 months, there was osseointegration between them. IHC showed that the expression of ALP in the experimental side was much higher than in the control side after 3 months and its expression decreased after 6 months with no difference from the control side. Conclusion: The custom-made TMJ prosthesis which was designed and manufactured by ourselves has good stability after total TMJ replacement. Ó 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Total temporomandibular joint replacement Stability Sheep Osseointegration
1. Introduction Total temporomandibular joint (TMJ) replacement is one of the most useful treatments for TMJ diseases, including TMJ osteoarthrosis, recurrent ankylosis of TMJ, crushing condylar fractures, end-stage TMJ disease and TMJ hypoplasia caused by congenital craniofacial syndrome (Guarda-Nardini et al., 2008; Mercuri, 1998; Schuurhuis et al., 2012; Wolford et al., 2003). Total TMJ prostheses include both standard and custom-made one. At present, the most common standard prosthesis used in China is the BiometeLorenz
* Corresponding author. Tel.: þ86 021 23271699 5204; fax: þ86 021 53072423. E-mail address: [email protected] (S.Y. Zhang).
total TMJ prosthesis (Biomet Microfixation, Jacksonville, FL, USA) (Jones, 2011). However, this type of prosthesis is designed based on American jaw morphology, which is quite different from the Chinese jaw in size. This limits its use in our clinical work. While custom-made prosthesis can exactly match the patient’s joint according to preoperative reconstruction, and it can be highly consistent with the patient’s mandible causing less adjustment and shaping (A and E, 2013). However, all of the custom-made prostheses used in China now are manufactured in other countries, which is expensive and time-consuming. Therefore, we designed the custom-made prosthesis by ourselves by referring to the TMJ Concepts (Ventura, CA, USA) (Wolford et al., 2003). In the present study, we chose normal sheep as subjects and a total TMJ replacement was performed on the sheep in order to observe the stability of the prosthesis we made.
http://dx.doi.org/10.1016/j.jcms.2014.03.008 1010-5182/Ó 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Shen P, et al., Stability study of total temporomandibular joint replacement on sheep, Journal of CranioMaxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.03.008
2
P. Shen et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2014) 1e6
2. Materials and methods 2.1. Experimental animals and groups Six healthy sheep were provided by the Animal Experiment Lab of Shanghai Jiao Tong University School of Medicine. The selection standards of the animals were as follows: 6 months old, weighing 17 to 20 kg, no teeth missing, good nutrition, and moving freely. The right TMJ was used as the experimental side which received total TMJ replacement, while the left side was used as the control side without any treatment. 2.2. Design and manufacturing of TMJ prostheses CT scanning (0.625-mm slices, 0.33 mm reconstruction) (General Electric, Milwaukee, WI) was performed on all six sheep before surgery. The CT data in DICOM (Digital Imaging and Communications in Medicine) format were input into an interactive surgicase5.0 software program (Materialise Medical, Leuven, Belgium). Then 3-dimensional skulls were reconstructed in STL (Standard Template Library) format and replacement surgery was simulated. The STL data was input into RP software (Geomagic, version 10.0; Geomagic, Research Triangle Park, NC) and then 3-dimensional resin skull models were fabricated, grinded, polished, and sprayed by the AFS-320YS laser RP machine (Longyuan, Beijing, China). The prostheses, which were referring to TMJ Concepts system, were manufactured by Shanghai PuWei Medical Equipment Limited Company. Ultra-high molecular weight polyethylene (Hoechst, Frankfurt am Main, Germany) were used to make glenoid fossa lining, while titanium alloy (Ergste westig, Dusseldorf, Germany) to prefabricate mandibular retention handle and titanium plate over glenoid fossa, and cobalt-chromium-molybdenum alloy (Dynamet Technology, Florida, America) to prefabricate condyle. The prosthetic components had preformed holes for fixation with 2.0 mm diameter and 6.0 mm length titanium alloy screws. The size of glenoid fossa and condyle were all in accordance with the nature TMJ of sheep, while the glenoid fossa was concave and the condyle was convex (Fig. 1). 2.3. Surgical technique The experimental animals were generally anesthetized using 2.5% andsodium amobarbital (1 mL/kg) by intravenous injection after Ketamine (2 mL/5 kg) via intramuscular injection. Preauricular incision was conducted to expose TMJ of the sheep after intermaxillary ligation to maintain the normal occlusion. Condyle, coronoid process together with articular disc were cut off and removed based on preoperative planning after exposing the TMJ and mandibular ramus. The front part of the fossa component was attached to bone at the root of the zygomatic arch while the retral to the front bone wall of external auditory canal. When the prostheses coincided with the bone fossa steadily, 4 titanium screws were used to fix it. Similarly, the mandibular component was
attached to the lateral aspect of the ramus of the mandibule and the prosthetic condyle was maintained in the posterosuperior medial position of the glenoid fossa. After this 8 titanium screws were used to fix it and the incision was processed by demixing suture. Threehundred and twenty thousand units of penicillin were injected intramuscularly for one week after operation, and these animals were fed with a soft diet for one week, followed by a normal diet (Fig. 2). The design and manufacture of the custom-made prostheses and the surgical process were the same as our previous article (Shen et al., 2013). 2.4. Specimen preparation and scanning electron microscope observation The experimental animals were killed after 3 and 6 months and the bone in contact with the prosthesis was resected with the size of 5 mm 5 mm 5 mm. Then the bone specimens were fixed by immersion in glutaraldehyde (2.5% in 0.05 M sodium cacodylate buffer, pH 7.4) and dehydrated in ethanol. The specimens were polished with diamond paper and coated with a thin layer of gold for examination by a scanning electron microscope (SEM; S-4700, Hitachi Co., Japan), where the scanning electron microscope was attached to an energy-dispersive, X-ray micro-analyzer (EMAX7000, Horiba Ltd., Japan). 2.5. Van Gieson-picric acid and magenta staining A titanium screw surrounded with bone tissue was cut with the size of 10 mm 10 mm 10 mm. The bone specimens were fixed using a 4% formaldehyde solution for 48 h and dehydrated in ethanol. Undecalcified specimens were embedded in plastic resin and then were incised into slices by rotary microtome (Leica, Germany) with the thickness of 150 mm. After the slices were ground to 30w40 mm, van gieson-picric acid and magenta staining were performed on the slices. 2.6. Immunohistochemical (IHC) staining of alkaline phosphatase (ALP) The bone in contact with the prosthesis at the broken end of the mandibule, as well as the bone at the same site on the control side, was resected to fix in a 4% formaldehyde solution for 24 h. Then, the specimens were decalcified in EDTA solution for 1 month and conventional dehydrated paraffin embedment, and serial sections were performed. IHC staining of the ALP was done for light microscope observation. 3. Results 3.1. SEM finding SEM observation showed that some immature bone, with a large amount of collagen fiber, was found in the bone surface in contact
Fig. 1. Surgicase5.0 software design before operation. A. The 3-dimensional model of the sheep; B. The simulation of ramus osteotomy by Surgicase5.0; C. The prosthesis of temporomandibular joint.
Please cite this article in press as: Shen P, et al., Stability study of total temporomandibular joint replacement on sheep, Journal of CranioMaxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.03.008
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Fig. 2. The process of the temporomandibular joint replacement. A. Incision of the surgery; B. Exposing the mandibular ramus; C. Resection of the condyle, coronoid process and disc; D. Implantation the TMJ prosthesis.
with the prosthesis after 3 months. Calcification could also be seen in some sites on the bone surface. After 6 months, a considerable quantity of mature bone was observed in the specimens (Fig. 3). 3.2. Van Gieson-picric acid and magenta observation Trabecular bone sparsely arranged around the titanium screw and the combination of screw and bone was intermittent after 3 months under a light microscope. A lot of osteoid could also be found around the titanium screw. After 6 months, new bone was tightly bound to the screw and the osteoid disappeared but was replaced by mature bone (Fig. 4). 3.3. ALP expression in the bone We used DAPI to dye the cell nucleus, which presented blue fluorescence. We also used FITC to mark ALP manifesting green
fluorescence under a light microscope. ALP was found in the bones of both the experimental and control sites and it was mainly expressed in the cytoplasm of the osteoblast. However, the expression of ALP in the experimental bone tissue was much higher than in the control side after 3 months (Fig. 5). It was significantly decreased in the experimental side after 6 months and there was no significant difference between the two sides (Fig. 6). 4. Discussion Total TMJ prosthesis replacement is one of the useful methods to treat end-stage TMJ diseases. However, the stability of total TMJ replacement is one of the most important factors affecting the service life of the prosthesis (Harris, 1995; Valen, 2013). As a result, it is key to investigate how to improve the stability of prostheses in TMJ surgery.
Please cite this article in press as: Shen P, et al., Stability study of total temporomandibular joint replacement on sheep, Journal of CranioMaxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.03.008
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Fig. 3. SEM images of the bone on the surface of the prosthesis. A. There were a lot of collagenous fibers on the surface of the prosthesis 3 months after operation. Calcifications can also be seen in some areas; B. A large number of mature bone was formed on the surface of prosthesis 6 months after operation. CF: collagenous fibers. NB: new bone.
The studies on prosthesis show that besides infection, aseptic loosening is another major factor which can influence the stability of the prosthesis. Aseptic loosening can be the result of mechanical and biological factors (Baumann et al., 2004; Nadzadi et al., 2003; Soong et al., 2004). Among them, the change of mechanics (that is the micromotion on the interface between prosthesis and bone) has a direct relationship with aseptic loosening. Bowman et al. (Bowman et al., 1998) found that micromotion on the trabecular bone could result in fatigued damage or a break in the trabecular bone, which could promote bone resorption between bone and prosthesis and lead to the loosening of the prosthesis. Jasty et al. (Jasty et al., 1997) reported that once the micromotion on the interface between prosthesis and bone reached a certain critical value, bone growth was inhibited while the growth of fibrous tissue was significantly increased. TMJ as one of the most complex joints also has the problem of aseptic loosening of the prosthesis (Jones, 2011). Therefore, reducing micromotion is a difficult and important point to investigate. Due to the personalized characteristic of the body and complex anatomical structures of the TMJ, standard TMJ prostheses could hardly reach perfect matching with the mandibule. Large gaps often exists between the prosthesis and bone, which could result in micromotion of the prosthesis (Spagnoli and Kent, 1992). As a result, standard TMJ prosthesis cannot ensure long-term stability. In order to reach the exact match between prosthesis and body, nowadays, custom-made prostheses have an increasing application in our clinical work (Mercuri, 1998, 2012a). Because of overcoming repeated adjustment and the shaping shortcomings of the standard prosthesis, and achieving a perfect match with the bone, custommade prostheses have gradually won many surgeons’ welcome. In the present study, we used the CAD/CAM technique to
manufacture the custom-made prostheses. Although many reports showed that custom-made TMJ prostheses have good clinical effect (Jones, 2011; Mercuri et al., 2007; Westermark et al., 2011), it is necessary for us to observe the histological changes of bone in newly-made prostheses. In this study, we found that there was osteoid formation on the surface of the prosthesis, and around the titanium screw, by SEM and light microscope observation after 3 months. This was in accordance with the results from Arabshahia who confirmed that the anatomical curvature contact surface design of TMJ implant can moderately improve the stability (Arabshahi et al., 2011). Accordingly, the expression of ALP in the experimental side was much higher than in the control side by the IHC. ALP is an effective index for the activity of the osteoblast. These results indicated that it was in the active phase of new bone formation after 3 months. However, after 6 months, there was a large amount of mature bone on the interface between prosthesis and bone and the osteoid disappeared, which suggested that it was osseointegration between the prosthesis and bone. Meanwhile, the expression of ALP was significantly decreased in the experimental side with no difference from the control side. This suggested osteogenetic activity was stable. Because the design and manufacture of custommade TMJ prosthesis was entirely based on the patient’s anatomical structures (Bouyssie et al., 1997; Swaelens and K, 1993), the prosthesis could achieve a perfect match with the bone and the gap between them was narrowed as much as possible (Mercuri, 2012a). This not only reduced micromotion on the interface between prosthesis and bone but also increased the contact area and promoted osteogenesis. Thus, custom-made TMJ prosthesis could reduce the incidence of aseptic loosening and increase stability.
Fig. 4. Van Gieson staining of the screw-bone junction (100). A. A lot of osteoid was observed, which presented yellow along the screw after 3 months; B. Osteoid disappeared and was replaced by mature bone after 6 months.
Please cite this article in press as: Shen P, et al., Stability study of total temporomandibular joint replacement on sheep, Journal of CranioMaxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.03.008
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Fig. 5. Immunofluorescence staining of the bone after 3 months (400). A.B. Images of the control side; C.D. Images of the experimental side. The green fluorescence is due to ALP expression in bone (A.C.). A merger of immunofluorescence staining and DAPI staining shows that ALP exists in the cytoplasm (B.D.).
Fig. 6. Immunofluorescence staining of the bone after 6 months (400). A.B. Images of the control side; C.D. Images of the experimental side. The green fluorescence is due to ALP expression in bone (A.C.). A merger of immunofluorescence staining and DAPI staining shows that ALP exists in the cytoplasm (B.D.).
Please cite this article in press as: Shen P, et al., Stability study of total temporomandibular joint replacement on sheep, Journal of CranioMaxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.03.008
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P. Shen et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2014) 1e6
There are many other factors which can influence stability of the prosthesis, such as infection, material sensitivity, wear particles, chronic post operation pain and so on (Baumann et al., 2004; Fuller et al., 2002; Mercuri, 2012b; Overgaard and Soballe, 2000; Zreiqat et al., 2003). Therefore, investigating how to improve the stability of the prosthesis from every aspect is also the direction of our research. 5. Conclusion In conclusion, we can deduce that the custom-made TMJ prosthesis, which we designed and manufactured by ourselves, can reduce the incidence of aseptic loosening and it has good stability. Funding This study was supported by 2013 National Natural Science Foundation of China, China (81371168), Shanghai Leading Academic Discipline Project, China (S30206), Natural Science Foundation of Shanghai, China (10ZR1418200), Shanghai Pujiang Talent Plan in 2011, China, Shanghai Science and Technology Commission funded project, China (13XD1402300) and the Seventh Students’ Innovative Training Project of Shanghai Jiao Tong University School of Medicine, China (2013052). References A JS, E G: One-year prospective outcome analysis and complications following total replacement of the temporomandibular joint with the TMJ concepts system. Br J Oral Maxillofac Surg 51: 620e624, 2013 Arabshahi Z, Kashani J, Kadir MRA, Azari A: Influence of thickness and contact surface geometry of condylar stem of TMJ implant on its stability. Phys Procedia 22: 414e419, 2011 Baumann B, Rader CP, Seufert J, Noth U, Rolf O, Eulert J, et al: Effects of polyethylene and TiAlV wear particles on expression of RANK, RANKL and OPG mRNA. Acta Orthop Scand 75: 295e302, 2004 Bouyssie JF, Bouyssie S, Sharrock P, Duran D: Stereolithographic models derived from X-ray computed tomography. Reproduction accuracy. Surg Radiol Anat 19: 193e199, 1997 Bowman SM, Guo XE, Cheng DW, Keaveny TM, Gibson LJ, Hayes WC, et al: Creep contributes to the fatigue behavior of bovine trabecular bone. J Biomech Eng 120: 647e654, 1998
Fuller K, Murphy C, Kirstein B, Fox SW, Chambers TJ: TNFalpha potently activates osteoclasts, through a direct action independent of and strongly synergistic with RANKL. Endocrinology 143: 1108e1118, 2002 Guarda-Nardini L, Manfredini D, Ferronato G: Total temporomandibular joint replacement: a clinical case with a proposal for post-surgical rehabilitation. J Craniomaxillofac Surg 36: 403e409, 2008 Harris WH: The problem is osteolysis. Clin Orthop Relat Res: 46e53, 1995 Jasty M, Bragdon C, Burke D, O’Connor D, Lowenstein J, Harris WH: In vivo skeletal responses to porous-surfaced implants subjected to small induced motions. J Bone Joint Surg Am 79: 707e714, 1997 Jones RH: Temporomandibular joint reconstruction with total alloplastic joint replacement. Aust Dent J 56: 85e91, 2011 Mercuri LG: Alloplastic temporomandibular joint reconstruction. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 85: 631e637, 1998 Mercuri LG: Alloplastic temporomandibular joint replacement: rationale for the use of custom devices. Int J Oral Maxillofac Surg 41: 1033e1040, 2012a Mercuri LG: Avoiding and managing temporomandibular joint total joint replacement surgical site infections. J Oral Maxillofac Surg 70: 2280e2289, 2012b Mercuri LG, Edibam NR, Giobbie-Hurder A: Fourteen-year follow-up of a patientfitted total temporomandibular joint reconstruction system. J Oral Maxillofac Surg 65: 1140e1148, 2007 Nadzadi ME, Pedersen DR, Yack HJ, Callaghan JJ, Brown TD: Kinematics, kinetics, and finite element analysis of commonplace maneuvers at risk for total hip dislocation. J Biomech 36: 577e591, 2003 Overgaard S, Soballe K: Polyethylene wear, osteolysis and acetabular loosening with an HA-coated hip prosthesis. J Bone Joint Surg Br 82: 305e306, 2000 Schuurhuis JM, Dijkstra PU, Stegenga B, de Bont LG, Spijkervet FK: Groningen temporomandibular total joint prosthesis: an 8-year longitudinal follow-up on function and pain. J Craniomaxillofac Surg 40: 815e820, 2012 Shen P, Zhang S, Yang C, Huang D: The mandibular symmetry evaluation of total temporomandibular joint replacement on developing sheep. J Craniomaxillofac Surg, 2013 Soong M, Rubash HE, Macaulay W: Dislocation after total hip arthroplasty. J Am Acad Orthop Surg 12: 314e321, 2004 Spagnoli D, Kent JN: Multicentser evaluation of temporomandibular joint proplastteflon disk implant. Oral Surg Oral Med Oral Pathol 74: 411e421, 1992 Swaelens B, K J: Medical applications of rapid prototyping techniques. In: Richard P, Chartoff AJL, Schenk Joseph A (eds), Proceedings of the Fourth International Conference on Rapid Prototyping; 1993, 1993 Toledo: OH 107e120 Valen B: Dislocation of hip prostheses. Tidsskr Nor Laegeforen 133: 1197e1199, 2013 Westermark A, Heden P, Aagaard E, Cornelius CP: The use of TMJ concepts prostheses to reconstruct patients with major temporomandibular joint and mandibular defects. Int J Oral Maxillofac Surg 40: 487e496, 2011 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 Zreiqat H, Crotti TN, Howlett CR, Capone M, Markovic B, Haynes DR: Prosthetic particles modify the expression of bone-related proteins by human osteoblastic cells in vitro. Biomaterials 24: 337e346, 2003
Please cite this article in press as: Shen P, et al., Stability study of total temporomandibular joint replacement on sheep, Journal of CranioMaxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.03.008
Contents lists available at ScienceDirect
Journal of Cranio-Maxillo-Facial Surgery journal homepage: www.jcmfs.com
Stability study of total temporomandibular joint replacement on sheep Pei Shen, Shan Yong Zhang*, Chi Yang, Bai Yun Department of Oral Surgery, Ninth People’s Hospital, College of Stomatology, Shanghai Jiao Tong University School of Medicine, Shanghai Key Laboratory of Stomatology & Shanghai Research Institute of Stomatology, No. 639, ZhiZaoJu Rd, 200011 Shanghai, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 25 July 2013 Accepted 10 March 2014
Objective: To evaluate the stability of our custom-made prosthesis by establishing the model of sheep total temporomandibular joint (TMJ) replacement. Methods: Six sheep were included in our study. Spiral computed tomography (CT) data of all sheep was obtained and transformed into 3-dimensional model by surgicase5.0 software preoperatively. Total TMJ prostheses were made based on the skull model. Ultra-high molecular weight polyethylene was used to make glenoid fossa lining, while titanium alloy to prefabricate mandibular retention handle and titanium plate over glenoid fossa. Cobalt-chromium-molybdenum alloy was also used to prefabricate the condyle. The right sides of all sheep, as the experimental group, were carried out total TMJ replacement, while the left sides were as the control group. The bone in both experimental and control side were excised after 3 and 6 months. Scanning electron microscope (SEM) was used to observe the interface between bone and prosthesis. Van Gieson staining and immunohistochemical staining (IHC) were used respectively to observe the interface of titanium screw and bone and the expression of alkaline phosphatase (ALP). Results: SEM and Van Gieson staining showed that there was immature bone and osteoid formed in the interface of prosthesis and bone after 3 months. While after 6 months, there was osseointegration between them. IHC showed that the expression of ALP in the experimental side was much higher than in the control side after 3 months and its expression decreased after 6 months with no difference from the control side. Conclusion: The custom-made TMJ prosthesis which was designed and manufactured by ourselves has good stability after total TMJ replacement. Ó 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Total temporomandibular joint replacement Stability Sheep Osseointegration
1. Introduction Total temporomandibular joint (TMJ) replacement is one of the most useful treatments for TMJ diseases, including TMJ osteoarthrosis, recurrent ankylosis of TMJ, crushing condylar fractures, end-stage TMJ disease and TMJ hypoplasia caused by congenital craniofacial syndrome (Guarda-Nardini et al., 2008; Mercuri, 1998; Schuurhuis et al., 2012; Wolford et al., 2003). Total TMJ prostheses include both standard and custom-made one. At present, the most common standard prosthesis used in China is the BiometeLorenz
* Corresponding author. Tel.: þ86 021 23271699 5204; fax: þ86 021 53072423. E-mail address: [email protected] (S.Y. Zhang).
total TMJ prosthesis (Biomet Microfixation, Jacksonville, FL, USA) (Jones, 2011). However, this type of prosthesis is designed based on American jaw morphology, which is quite different from the Chinese jaw in size. This limits its use in our clinical work. While custom-made prosthesis can exactly match the patient’s joint according to preoperative reconstruction, and it can be highly consistent with the patient’s mandible causing less adjustment and shaping (A and E, 2013). However, all of the custom-made prostheses used in China now are manufactured in other countries, which is expensive and time-consuming. Therefore, we designed the custom-made prosthesis by ourselves by referring to the TMJ Concepts (Ventura, CA, USA) (Wolford et al., 2003). In the present study, we chose normal sheep as subjects and a total TMJ replacement was performed on the sheep in order to observe the stability of the prosthesis we made.
http://dx.doi.org/10.1016/j.jcms.2014.03.008 1010-5182/Ó 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Shen P, et al., Stability study of total temporomandibular joint replacement on sheep, Journal of CranioMaxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.03.008
2
P. Shen et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2014) 1e6
2. Materials and methods 2.1. Experimental animals and groups Six healthy sheep were provided by the Animal Experiment Lab of Shanghai Jiao Tong University School of Medicine. The selection standards of the animals were as follows: 6 months old, weighing 17 to 20 kg, no teeth missing, good nutrition, and moving freely. The right TMJ was used as the experimental side which received total TMJ replacement, while the left side was used as the control side without any treatment. 2.2. Design and manufacturing of TMJ prostheses CT scanning (0.625-mm slices, 0.33 mm reconstruction) (General Electric, Milwaukee, WI) was performed on all six sheep before surgery. The CT data in DICOM (Digital Imaging and Communications in Medicine) format were input into an interactive surgicase5.0 software program (Materialise Medical, Leuven, Belgium). Then 3-dimensional skulls were reconstructed in STL (Standard Template Library) format and replacement surgery was simulated. The STL data was input into RP software (Geomagic, version 10.0; Geomagic, Research Triangle Park, NC) and then 3-dimensional resin skull models were fabricated, grinded, polished, and sprayed by the AFS-320YS laser RP machine (Longyuan, Beijing, China). The prostheses, which were referring to TMJ Concepts system, were manufactured by Shanghai PuWei Medical Equipment Limited Company. Ultra-high molecular weight polyethylene (Hoechst, Frankfurt am Main, Germany) were used to make glenoid fossa lining, while titanium alloy (Ergste westig, Dusseldorf, Germany) to prefabricate mandibular retention handle and titanium plate over glenoid fossa, and cobalt-chromium-molybdenum alloy (Dynamet Technology, Florida, America) to prefabricate condyle. The prosthetic components had preformed holes for fixation with 2.0 mm diameter and 6.0 mm length titanium alloy screws. The size of glenoid fossa and condyle were all in accordance with the nature TMJ of sheep, while the glenoid fossa was concave and the condyle was convex (Fig. 1). 2.3. Surgical technique The experimental animals were generally anesthetized using 2.5% andsodium amobarbital (1 mL/kg) by intravenous injection after Ketamine (2 mL/5 kg) via intramuscular injection. Preauricular incision was conducted to expose TMJ of the sheep after intermaxillary ligation to maintain the normal occlusion. Condyle, coronoid process together with articular disc were cut off and removed based on preoperative planning after exposing the TMJ and mandibular ramus. The front part of the fossa component was attached to bone at the root of the zygomatic arch while the retral to the front bone wall of external auditory canal. When the prostheses coincided with the bone fossa steadily, 4 titanium screws were used to fix it. Similarly, the mandibular component was
attached to the lateral aspect of the ramus of the mandibule and the prosthetic condyle was maintained in the posterosuperior medial position of the glenoid fossa. After this 8 titanium screws were used to fix it and the incision was processed by demixing suture. Threehundred and twenty thousand units of penicillin were injected intramuscularly for one week after operation, and these animals were fed with a soft diet for one week, followed by a normal diet (Fig. 2). The design and manufacture of the custom-made prostheses and the surgical process were the same as our previous article (Shen et al., 2013). 2.4. Specimen preparation and scanning electron microscope observation The experimental animals were killed after 3 and 6 months and the bone in contact with the prosthesis was resected with the size of 5 mm 5 mm 5 mm. Then the bone specimens were fixed by immersion in glutaraldehyde (2.5% in 0.05 M sodium cacodylate buffer, pH 7.4) and dehydrated in ethanol. The specimens were polished with diamond paper and coated with a thin layer of gold for examination by a scanning electron microscope (SEM; S-4700, Hitachi Co., Japan), where the scanning electron microscope was attached to an energy-dispersive, X-ray micro-analyzer (EMAX7000, Horiba Ltd., Japan). 2.5. Van Gieson-picric acid and magenta staining A titanium screw surrounded with bone tissue was cut with the size of 10 mm 10 mm 10 mm. The bone specimens were fixed using a 4% formaldehyde solution for 48 h and dehydrated in ethanol. Undecalcified specimens were embedded in plastic resin and then were incised into slices by rotary microtome (Leica, Germany) with the thickness of 150 mm. After the slices were ground to 30w40 mm, van gieson-picric acid and magenta staining were performed on the slices. 2.6. Immunohistochemical (IHC) staining of alkaline phosphatase (ALP) The bone in contact with the prosthesis at the broken end of the mandibule, as well as the bone at the same site on the control side, was resected to fix in a 4% formaldehyde solution for 24 h. Then, the specimens were decalcified in EDTA solution for 1 month and conventional dehydrated paraffin embedment, and serial sections were performed. IHC staining of the ALP was done for light microscope observation. 3. Results 3.1. SEM finding SEM observation showed that some immature bone, with a large amount of collagen fiber, was found in the bone surface in contact
Fig. 1. Surgicase5.0 software design before operation. A. The 3-dimensional model of the sheep; B. The simulation of ramus osteotomy by Surgicase5.0; C. The prosthesis of temporomandibular joint.
Please cite this article in press as: Shen P, et al., Stability study of total temporomandibular joint replacement on sheep, Journal of CranioMaxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.03.008
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Fig. 2. The process of the temporomandibular joint replacement. A. Incision of the surgery; B. Exposing the mandibular ramus; C. Resection of the condyle, coronoid process and disc; D. Implantation the TMJ prosthesis.
with the prosthesis after 3 months. Calcification could also be seen in some sites on the bone surface. After 6 months, a considerable quantity of mature bone was observed in the specimens (Fig. 3). 3.2. Van Gieson-picric acid and magenta observation Trabecular bone sparsely arranged around the titanium screw and the combination of screw and bone was intermittent after 3 months under a light microscope. A lot of osteoid could also be found around the titanium screw. After 6 months, new bone was tightly bound to the screw and the osteoid disappeared but was replaced by mature bone (Fig. 4). 3.3. ALP expression in the bone We used DAPI to dye the cell nucleus, which presented blue fluorescence. We also used FITC to mark ALP manifesting green
fluorescence under a light microscope. ALP was found in the bones of both the experimental and control sites and it was mainly expressed in the cytoplasm of the osteoblast. However, the expression of ALP in the experimental bone tissue was much higher than in the control side after 3 months (Fig. 5). It was significantly decreased in the experimental side after 6 months and there was no significant difference between the two sides (Fig. 6). 4. Discussion Total TMJ prosthesis replacement is one of the useful methods to treat end-stage TMJ diseases. However, the stability of total TMJ replacement is one of the most important factors affecting the service life of the prosthesis (Harris, 1995; Valen, 2013). As a result, it is key to investigate how to improve the stability of prostheses in TMJ surgery.
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Fig. 3. SEM images of the bone on the surface of the prosthesis. A. There were a lot of collagenous fibers on the surface of the prosthesis 3 months after operation. Calcifications can also be seen in some areas; B. A large number of mature bone was formed on the surface of prosthesis 6 months after operation. CF: collagenous fibers. NB: new bone.
The studies on prosthesis show that besides infection, aseptic loosening is another major factor which can influence the stability of the prosthesis. Aseptic loosening can be the result of mechanical and biological factors (Baumann et al., 2004; Nadzadi et al., 2003; Soong et al., 2004). Among them, the change of mechanics (that is the micromotion on the interface between prosthesis and bone) has a direct relationship with aseptic loosening. Bowman et al. (Bowman et al., 1998) found that micromotion on the trabecular bone could result in fatigued damage or a break in the trabecular bone, which could promote bone resorption between bone and prosthesis and lead to the loosening of the prosthesis. Jasty et al. (Jasty et al., 1997) reported that once the micromotion on the interface between prosthesis and bone reached a certain critical value, bone growth was inhibited while the growth of fibrous tissue was significantly increased. TMJ as one of the most complex joints also has the problem of aseptic loosening of the prosthesis (Jones, 2011). Therefore, reducing micromotion is a difficult and important point to investigate. Due to the personalized characteristic of the body and complex anatomical structures of the TMJ, standard TMJ prostheses could hardly reach perfect matching with the mandibule. Large gaps often exists between the prosthesis and bone, which could result in micromotion of the prosthesis (Spagnoli and Kent, 1992). As a result, standard TMJ prosthesis cannot ensure long-term stability. In order to reach the exact match between prosthesis and body, nowadays, custom-made prostheses have an increasing application in our clinical work (Mercuri, 1998, 2012a). Because of overcoming repeated adjustment and the shaping shortcomings of the standard prosthesis, and achieving a perfect match with the bone, custommade prostheses have gradually won many surgeons’ welcome. In the present study, we used the CAD/CAM technique to
manufacture the custom-made prostheses. Although many reports showed that custom-made TMJ prostheses have good clinical effect (Jones, 2011; Mercuri et al., 2007; Westermark et al., 2011), it is necessary for us to observe the histological changes of bone in newly-made prostheses. In this study, we found that there was osteoid formation on the surface of the prosthesis, and around the titanium screw, by SEM and light microscope observation after 3 months. This was in accordance with the results from Arabshahia who confirmed that the anatomical curvature contact surface design of TMJ implant can moderately improve the stability (Arabshahi et al., 2011). Accordingly, the expression of ALP in the experimental side was much higher than in the control side by the IHC. ALP is an effective index for the activity of the osteoblast. These results indicated that it was in the active phase of new bone formation after 3 months. However, after 6 months, there was a large amount of mature bone on the interface between prosthesis and bone and the osteoid disappeared, which suggested that it was osseointegration between the prosthesis and bone. Meanwhile, the expression of ALP was significantly decreased in the experimental side with no difference from the control side. This suggested osteogenetic activity was stable. Because the design and manufacture of custommade TMJ prosthesis was entirely based on the patient’s anatomical structures (Bouyssie et al., 1997; Swaelens and K, 1993), the prosthesis could achieve a perfect match with the bone and the gap between them was narrowed as much as possible (Mercuri, 2012a). This not only reduced micromotion on the interface between prosthesis and bone but also increased the contact area and promoted osteogenesis. Thus, custom-made TMJ prosthesis could reduce the incidence of aseptic loosening and increase stability.
Fig. 4. Van Gieson staining of the screw-bone junction (100). A. A lot of osteoid was observed, which presented yellow along the screw after 3 months; B. Osteoid disappeared and was replaced by mature bone after 6 months.
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Fig. 5. Immunofluorescence staining of the bone after 3 months (400). A.B. Images of the control side; C.D. Images of the experimental side. The green fluorescence is due to ALP expression in bone (A.C.). A merger of immunofluorescence staining and DAPI staining shows that ALP exists in the cytoplasm (B.D.).
Fig. 6. Immunofluorescence staining of the bone after 6 months (400). A.B. Images of the control side; C.D. Images of the experimental side. The green fluorescence is due to ALP expression in bone (A.C.). A merger of immunofluorescence staining and DAPI staining shows that ALP exists in the cytoplasm (B.D.).
Please cite this article in press as: Shen P, et al., Stability study of total temporomandibular joint replacement on sheep, Journal of CranioMaxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.03.008
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There are many other factors which can influence stability of the prosthesis, such as infection, material sensitivity, wear particles, chronic post operation pain and so on (Baumann et al., 2004; Fuller et al., 2002; Mercuri, 2012b; Overgaard and Soballe, 2000; Zreiqat et al., 2003). Therefore, investigating how to improve the stability of the prosthesis from every aspect is also the direction of our research. 5. Conclusion In conclusion, we can deduce that the custom-made TMJ prosthesis, which we designed and manufactured by ourselves, can reduce the incidence of aseptic loosening and it has good stability. Funding This study was supported by 2013 National Natural Science Foundation of China, China (81371168), Shanghai Leading Academic Discipline Project, China (S30206), Natural Science Foundation of Shanghai, China (10ZR1418200), Shanghai Pujiang Talent Plan in 2011, China, Shanghai Science and Technology Commission funded project, China (13XD1402300) and the Seventh Students’ Innovative Training Project of Shanghai Jiao Tong University School of Medicine, China (2013052). References A JS, E G: One-year prospective outcome analysis and complications following total replacement of the temporomandibular joint with the TMJ concepts system. Br J Oral Maxillofac Surg 51: 620e624, 2013 Arabshahi Z, Kashani J, Kadir MRA, Azari A: Influence of thickness and contact surface geometry of condylar stem of TMJ implant on its stability. Phys Procedia 22: 414e419, 2011 Baumann B, Rader CP, Seufert J, Noth U, Rolf O, Eulert J, et al: Effects of polyethylene and TiAlV wear particles on expression of RANK, RANKL and OPG mRNA. Acta Orthop Scand 75: 295e302, 2004 Bouyssie JF, Bouyssie S, Sharrock P, Duran D: Stereolithographic models derived from X-ray computed tomography. Reproduction accuracy. Surg Radiol Anat 19: 193e199, 1997 Bowman SM, Guo XE, Cheng DW, Keaveny TM, Gibson LJ, Hayes WC, et al: Creep contributes to the fatigue behavior of bovine trabecular bone. J Biomech Eng 120: 647e654, 1998
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Please cite this article in press as: Shen P, et al., Stability study of total temporomandibular joint replacement on sheep, Journal of CranioMaxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.03.008