**2. Materials and Methods**

In this section, we discuss the methodology of designing condylar and fossa components of the custom-designed total TMJ prostheses. Also discussed, are unique design features such as accurate fit of the prosthetic surface to the host bone in contact, perforated notches of implant which protrude and fit into the custom-cut slots in native bone, customized surgical guides, and screws with locking mechanism.

### *2.1. Design of Patient-Specific Total TMJ Prosthesis 2.1. Design of Patient-Specific Total TMJ Prosthesis*

The schematic in Figure 1 outlines our approach to developing a novel patient-specific total TMJ implant system. Our unique patient-fitted designs based on computed tomography (CT) images of the patient's TMJ and associated anatomic structures offer accurate anatomical fit and better fixation to the host bone. The novel/unique features of the prostheses promise an improved osseo-integration and durability. Our design process is based on surgeon's requirements, feedback, and pre-surgical planning to ensure anatomically accurate and clinically viable device design. Pre-planning of the surgery is an integral part of the proposed design and development methodology, and is intended to reduce intraoperative adjustments of the device components, complexity of the already challenging operating procedure, and the overall time spent in the operating room. The schematic in Figure 1 outlines our approach to developing a novel patient-specific total TMJ implant system. Our unique patient-fitted designs based on computed tomography (CT) images of the patient's TMJ and associated anatomic structures offer accurate anatomical fit and better fixation to the host bone. The novel/unique features of the prostheses promise an improved osseo-integration and durability. Our design process is based on surgeon's requirements, feedback, and pre-surgical planning to ensure anatomically accurate and clinically viable device design. Pre-planning of the surgery is an integral part of the proposed design and development methodology, and is intended to reduce intra-operative adjustments of the device components, complexity of the already challenging operating procedure, and the overall time spent in the operating room.

**Figure 1.** Methodology followed for design and preliminary analysis of the patient-specific total temporomandibular joint (TMJ) prostheses. **Figure 1.** Methodology followed for design and preliminary analysis of the patient-specific total temporomandibular joint (TMJ) prostheses.

Subject-specific 3D anatomical reconstruction of the patient's mandible and skull/fossa/ articular eminence is performed using commercial software Mimics v14.12 (Materialise, Plymouth, MI, USA) from computed tomography (CT) scans (see Figure 2). Upon importing the patient's CT images in Mimics, anatomical model comprising of the patient's mandible and fossa eminence is developed by performing a series of operations such as image processing, segmentation, region growing, mask formation for the anatomic region of interest (i.e., bone and teeth), and calculation of 3D equivalent similar to the 3D reconstruction method described elsewhere [18]. The prostheses and accessories are designed using commercial software packages 3-matic v6.0 (Materialise, Plymouth, MI, USA) and SolidWorks v2010 (SIMULIA, Providence, RI, USA) as discussed in following sections. skull/fossa/articular eminence is performed using commercial software Mimics v14.12 (Materialise, Plymouth, MI, USA) from computed tomography (CT) scans (see Figure 2). Upon importing the patient's CT images in Mimics, anatomical model comprising of the patient's mandible and fossa eminence is developed by performing a series of operations such as image processing, segmentation, region growing, mask formation for the anatomic region of interest (i.e., bone and teeth), and calculation of 3D equivalent similar to the 3D reconstruction method described elsewhere [18]. The prostheses and accessories are designed using commercial software packages 3-matic v6.0 (Materialise, Plymouth, MI, USA) and SolidWorks v2010 (SIMULIA, Providence, RI, USA) as discussed in following sections.

Subject-specific 3D anatomical reconstruction of the patient's mandible and

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**Figure 2.** Subject-specific 3D anatomical reconstruction of the patient's mandible and fossa eminence performed from computed tomography (CT) data using Mimics software. **Figure 2.** Subject-specific 3D anatomical reconstruction of the patient's mandible and fossa eminence performed from computed tomography (CT) data using Mimics software.

### 2.1.1. Surgical Pre-Planning and Surgeon Input 2.1.1. Surgical Pre-Planning and Surgeon Input

Close collaboration between device designer and surgeon (treating the given TMJ patient) is an important aspect of the proposed design and development approach. Mutual sharing of knowledge and expertise, clinical and design requirements and constraints is vital in ensuring the optimal design and performance of TMJ devices. We utilize the computerized anatomical model and its 3D printed equivalent to acquire surgeon's design requirements such as location of the facial nerve (to keep it from any damage or injury during surgery), location of the condylar osteotomy (i.e., removal of the degenerated or damaged condylar bone), outline of shape for the planned condylar and fossa prostheses, location of screws to secure the condylar and fossa components to host bone, number and dimension of screws, etc. Close collaboration between device designer and surgeon (treating the given TMJ patient) is an important aspect of the proposed design and development approach. Mutual sharing of knowledge and expertise, clinical and design requirements and constraints is vital in ensuring the optimal design and performance of TMJ devices. We utilize the computerized anatomical model and its 3D printed equivalent to acquire surgeon's design requirements such as location of the facial nerve (to keep it from any damage or injury during surgery), location of the condylar osteotomy (i.e., removal of the degenerated or damaged condylar bone), outline of shape for the planned condylar and fossa prostheses, location of screws to secure the condylar and fossa components to host bone, number and dimension of screws, etc.

To help the surgeon accurately remove the damaged part of condylar neck/head, a surgical guide is custom designed for each reconstruction case as shown in Figure 3. During surgery, after putting the patient in intermaxillary fixation (IMF) and gaining access to TMJ capsule, the surgical guide can be fixated to mandible using screws located superior and inferior to the line of osteotomy/condylectomy. In other words, the surgical guide is secured using screws at the condylar head and condylar neck/ramus depending on osteotomy location and surgeon's preference. After completing the osteotomy, surgical guide is detached from the bone by removing the screws. The location of condylectomy guide screw hole inferior to the anterio-posterior excision line can be selected (and custom designed) such that the same screw hole can also be used later by one of the screws used To help the surgeon accurately remove the damaged part of condylar neck/head, a surgical guide is custom designed for each reconstruction case as shown in Figure 3. During surgery, after putting the patient in intermaxillary fixation (IMF) and gaining access to TMJ capsule, the surgical guide can be fixated to mandible using screws located superior and inferior to the line of osteotomy/condylectomy. In other words, the surgical guide is secured using screws at the condylar head and condylar neck/ramus depending on osteotomy location and surgeon's preference. After completing the osteotomy, surgical guide is detached from the bone by removing the screws. The location of condylectomy guide screw hole inferior to the anterio-posterior excision line can be selected (and custom designed) such that the same screw hole can also be used later by one of the screws used to secure condylar/ramus implant to the host mandible.

to secure condylar/ramus implant to the host mandible. Our design approach and pre-surgical planning enables appropriate design of screws and pre-drilled screw holes in implants to avoid unintentional injury to facial nerve, soft tissue, and other delicate structures in the vicinity of the complex surgical site. Following the similar design approach used for osteotomy guide, the screw-drill-guide is custom designed each for the condylar/ramus component and the fossa-eminence part of the TMJ prostheses. These drill guides are intended to create a hole of preferred dimension (diameter and depth) at the accurate location and orientation for each screw as prescribed by the surgeon. For a given screw, a drill of smaller diameter than that of the particular

screw is selected so ensure less bone damage, optimal purchase, and rigid interface between the screw and host bone during and after implantation. *Materials* **2022**, *15*, x FOR PEER REVIEW 6 of 34

**Figure 3.** Custom-designed surgical guide for condylectomy (i.e., removal of damaged part of the condylar bone). (**A**,**B**) Show the medial and lateral view, respectively, of surgical guide placed at the location on mandible where osteotomy is to be performed. (**C**,**D**) Show medial and lateral–anterior view, respectively, of the surgical guide alone. The visuals demonstrate that custom-design of the device enables it to accurately adapt to the native bone. This methodology allows the designer to control size and shape of the device, and location of its fixation screws as prescribed by the surgeon. **Figure 3.** Custom-designed surgical guide for condylectomy (i.e., removal of damaged part of the condylar bone). (**A**,**B**) Show the medial and lateral view, respectively, of surgical guide placed at the location on mandible where osteotomy is to be performed. (**C**,**D**) Show medial and lateral–anterior view, respectively, of the surgical guide alone. The visuals demonstrate that custom-design of the device enables it to accurately adapt to the native bone. This methodology allows the designer to control size and shape of the device, and location of its fixation screws as prescribed by the surgeon.

Our design approach and pre-surgical planning enables appropriate design of screws and pre-drilled screw holes in implants to avoid unintentional injury to facial nerve, soft tissue, and other delicate structures in the vicinity of the complex surgical site. Following the similar design approach used for osteotomy guide, the screw-drill-guide is custom designed each for the condylar/ramus component and the fossa-eminence part of the TMJ prostheses. These drill guides are intended to create a hole of preferred dimension (diameter and depth) at the accurate location and orientation for each screw as prescribed by the surgeon. For a given screw, a drill of smaller diameter than that of the particular screw is selected so ensure less bone damage, optimal purchase, and rigid interface between the screw and host bone during and after implantation. Based on a surgeon's initial design requirements, the prostheses, drill guides, osteot-Based on a surgeon's initial design requirements, the prostheses, drill guides, osteotomy guide, and templates are designed. In response to surgeon's feedback about the initial designs, suggested changes are incorporated to improve the device design. This feedback loop is kept open, and the designs are fine-tuned, till the surgeon approves the designs. In-vitro biomechanical assessment of patient's host bone and TMJ prostheses is incorporated in the design validation and improvement loop as described later in this paper. After sufficiently improving the designs, the prostheses graduate to the next stage where finished implants and accessories are ready for prototyping and pre-surgical simulation of the operating procedure using anatomical models and finished prototypes. In real-world scenario, before applying our methodology to actual clinical application, it has to be verified and validated through cadaver studies.

### omy guide, and templates are designed. In response to surgeon's feedback about the ini-2.1.2. Design of Condylar Prosthesis

tial designs, suggested changes are incorporated to improve the device design. This feedback loop is kept open, and the designs are fine-tuned, till the surgeon approves the designs. In-vitro biomechanical assessment of patient's host bone and TMJ prostheses is incorporated in the design validation and improvement loop as described later in this paper. After sufficiently improving the designs, the prostheses graduate to the next stage where finished implants and accessories are ready for prototyping and pre-surgical simulation of the operating procedure using anatomical models and finished prototypes. In realworld scenario, before applying our methodology to actual clinical application, it has to be verified and validated through cadaver studies. Anatomically accurate fit of TMJ prosthesis to the host bone is essential for stable fixation leading to efficacy and longevity of the device. Our custom-designed condylar components follow the anatomical geometry and contours on the lateral surface of ramus and condylar part of host anatomy to which the prosthesis is to be fixated. Custom shape of the prosthesis maximizes the possibility of precise fit and secure fixation. Different shapes of the condylar and ramal parts can be designed per surgeon's recommendations to conform to the patient's unique/complex anatomical situation. Figures 4–12 show various such shapes of the condylar component of our TMJ prostheses. Since these components are

custom designed to meet the unique requirements of each individual patient's situation, the characteristic length, width, and thickness of condylar component; the number and locations of screws; and dimensions of condylar neck and head vary from patient to patient. The minimal level of the condylar thickness, width, head diameter, and number and location of screws are maintained (based on orthopaedic experience listed in the literature, surgeon's prescription, and pre-clinical biomechanical evaluation of the device designs) to ensure that the device provides sufficient mechanical strength and stability during functional and para-functional loading after implantation. situation, the characteristic length, width, and thickness of condylar component; the number and locations of screws; and dimensions of condylar neck and head vary from patient to patient. The minimal level of the condylar thickness, width, head diameter, and number and location of screws are maintained (based on orthopaedic experience listed in the literature, surgeon's prescription, and pre-clinical biomechanical evaluation of the device designs) to ensure that the device provides sufficient mechanical strength and stability during functional and para-functional loading after implantation. nents are custom designed to meet the unique requirements of each individual patient's situation, the characteristic length, width, and thickness of condylar component; the number and locations of screws; and dimensions of condylar neck and head vary from patient to patient. The minimal level of the condylar thickness, width, head diameter, and number and location of screws are maintained (based on orthopaedic experience listed in the literature, surgeon's prescription, and pre-clinical biomechanical evaluation of the device designs) to ensure that the device provides sufficient mechanical strength and stability during functional and para-functional loading after implantation.

Anatomically accurate fit of TMJ prosthesis to the host bone is essential for stable fixation leading to efficacy and longevity of the device. Our custom-designed condylar components follow the anatomical geometry and contours on the lateral surface of ramus and condylar part of host anatomy to which the prosthesis is to be fixated. Custom shape of the prosthesis maximizes the possibility of precise fit and secure fixation. Different shapes of the condylar and ramal parts can be designed per surgeon's recommendations to conform to the patient's unique/complex anatomical situation. Figures 4–12 show various such shapes of the condylar component of our TMJ prostheses. Since these components are custom designed to meet the unique requirements of each individual patient's

Anatomically accurate fit of TMJ prosthesis to the host bone is essential for stable fixation leading to efficacy and longevity of the device. Our custom-designed condylar components follow the anatomical geometry and contours on the lateral surface of ramus and condylar part of host anatomy to which the prosthesis is to be fixated. Custom shape of the prosthesis maximizes the possibility of precise fit and secure fixation. Different shapes of the condylar and ramal parts can be designed per surgeon's recommendations to conform to the patient's unique/complex anatomical situation. Figures 4–12 show various such shapes of the condylar component of our TMJ prostheses. Since these compo-

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2.1.2. Design of Condylar Prosthesis

2.1.2. Design of Condylar Prosthesis

**Figure 4.** Shape outline of a custom-designed condylar/ramus prosthesis. (**A**,**B**) Show medial–anterior view and lateral–anterior view, respectively, of the prosthesis accurately adapting to the host bone. (**C**) Shows medial-inferior view of the prosthesis shape outline. **Figure 4.** Shape outline of a custom-designed condylar/ramus prosthesis. (**A**,**B**) Show medial– anterior view and lateral–anterior view, respectively, of the prosthesis accurately adapting to the host bone. (**C**) Shows medial-inferior view of the prosthesis shape outline. **Figure 4.** Shape outline of a custom-designed condylar/ramus prosthesis. (**A**,**B**) Show medial–anterior view and lateral–anterior view, respectively, of the prosthesis accurately adapting to the host bone. (**C**) Shows medial-inferior view of the prosthesis shape outline.

**Figure 5.** Shape outline of a custom-designed condylar/ramus prosthesis for the replacement of right TMJ of a patient. (**A**,**B**) Show lateral–anterior view and lateral–posterior view, respectively, of the prosthesis accurately conforming to geometric shape of patient's mandible.

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prosthesis accurately conforming to geometric shape of patient's mandible.

**Figure 6.** Shape outline of a custom-designed condylar/ramus/mandibular component of the TMJ prosthesis for reconstruction of left TMJ. (**A**,**B**) Show medial–anterior view and lateral–anterior view, respectively, of the prosthesis along with 3D anatomical model of the patient's mandible after condylectomy. The osteotomy gap seen in the left mandibular body is due to removal of a tumor in that region. This osteotomy gap can be filled with a graft, and the mandibular component of this TMJ prosthesis is designed to provide mechanical support to the host bone and graft. **Figure 6.** Shape outline of a custom-designed condylar/ramus/mandibular component of the TMJ prosthesis for reconstruction of left TMJ. (**A**,**B**) Show medial–anterior view and lateral–anterior view, respectively, of the prosthesis along with 3D anatomical model of the patient's mandible after condylectomy. The osteotomy gap seen in the left mandibular body is due to removal of a tumor in that region. This osteotomy gap can be filled with a graft, and the mandibular component of this TMJ prosthesis is designed to provide mechanical support to the host bone and graft. **Figure 6.** Shape outline of a custom-designed condylar/ramus/mandibular component of the TMJ prosthesis for reconstruction of left TMJ. (**A**,**B**) Show medial–anterior view and lateral–anterior view, respectively, of the prosthesis along with 3D anatomical model of the patient's mandible after condylectomy. The osteotomy gap seen in the left mandibular body is due to removal of a tumor in that region. This osteotomy gap can be filled with a graft, and the mandibular component of this TMJ prosthesis is designed to provide mechanical support to the host bone and graft.

**Figure 5.** Shape outline of a custom-designed condylar/ramus prosthesis for the replacement of right TMJ of a patient. (**A**,**B**) Show lateral–anterior view and lateral–posterior view, respectively, of the

sis for left TMJ of a patient. (**A**) Shows lateral view of the implant with screw holes. (**B**) Shows an

enlarged view of the screw holes, where the first superiorly located screw hole has threads to incorporate locking-plate-screw mechanism by engaging the threads on the head of a locking screw described in the text. (**C**) Shows engineering dimensions of this patient-specific implant. **Figure 7.** Custom-designed condylar/ramus component of the TMJ total joint replacement prosthesis for left TMJ of a patient. (**A**) Shows lateral view of the implant with screw holes. (**B**) Shows an enlarged view of the screw holes, where the first superiorly located screw hole has threads to incorporate locking-plate-screw mechanism by engaging the threads on the head of a locking screw described in the text. (**C**) Shows engineering dimensions of this patient-specific implant. **Figure 7.** Custom-designed condylar/ramus component of the TMJ total joint replacement prosthesis for left TMJ of a patient. (**A**) Shows lateral view of the implant with screw holes. (**B**) Shows an enlarged view of the screw holes, where the first superiorly located screw hole has threads to incorporate locking-plate-screw mechanism by engaging the threads on the head of a locking screw described in the text. (**C**) Shows engineering dimensions of this patient-specific implant.

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**Figure 8.** Shape outline of a custom-designed condylar/ramus component of the TMJ total joint replacement prosthesis for left TMJ of a patient. (**A**) Shows anterior–lateral view of the implant with host bone after condylectomy. The posterior–medial view in (**B**) shows that the medial surface of prosthesis is shaped to accurately follow geometric contours of the lateral surface of mandibular host bone for optimal geometrical match between the implant and host bone. (**C**) Shows lateral view of the prosthesis with screw holes. Dimensions of various parts of this patient-specific implant are shown in (**D**). **Figure 8.** Shape outline of a custom-designed condylar/ramus component of the TMJ total joint replacement prosthesis for left TMJ of a patient. (**A**) Shows anterior–lateral view of the implant with host bone after condylectomy. The posterior–medial view in (**B**) shows that the medial surface of prosthesis is shaped to accurately follow geometric contours of the lateral surface of mandibular host bone for optimal geometrical match between the implant and host bone. (**C**) Shows lateral view of the prosthesis with screw holes. Dimensions of various parts of this patient-specific implant are shown in (**D**). **Figure 8.** Shape outline of a custom-designed condylar/ramus component of the TMJ total joint replacement prosthesis for left TMJ of a patient. (**A**) Shows anterior–lateral view of the implant with host bone after condylectomy. The posterior–medial view in (**B**) shows that the medial surface of prosthesis is shaped to accurately follow geometric contours of the lateral surface of mandibular host bone for optimal geometrical match between the implant and host bone. (**C**) Shows lateral view of the prosthesis with screw holes. Dimensions of various parts of this patient-specific implant are shown in (**D**).

placement prosthesis for left TMJ of a patient. Visuals in (**A**–**E**) demonstrate that shape of medial surface of the prosthesis accurately follows the geometric contours of the lateral surface of the mandibular host bone, and maximizes the opportunity for optimal adaptation of implant to the host bone. The lateral surface of the implant is flat, condylar head is spherical, and the condylar neck has a curvature to avoid problems seen in most right-angled designs of orthopaedic implants. **Figure 9.** Shape outline of a custom-designed condylar/ramus component of the TMJ total joint replacement prosthesis for left TMJ of a patient. Visuals in (**A**–**E**) demonstrate that shape of medial surface of the prosthesis accurately follows the geometric contours of the lateral surface of the mandibular host bone, and maximizes the opportunity for optimal adaptation of implant to the host bone. The lateral surface of the implant is flat, condylar head is spherical, and the condylar neck has a curvature to avoid problems seen in most right-angled designs of orthopaedic implants. **Figure 9.** Shape outline of a custom-designed condylar/ramus component of the TMJ total joint replacement prosthesis for left TMJ of a patient. Visuals in (**A**–**E**) demonstrate that shape of medial surface of the prosthesis accurately follows the geometric contours of the lateral surface of the mandibular host bone, and maximizes the opportunity for optimal adaptation of implant to the host bone. The lateral surface of the implant is flat, condylar head is spherical, and the condylar neck has a curvature to avoid problems seen in most right-angled designs of orthopaedic implants.

**Figure 10.** Different shapes of the condylar head of the custom-designed condylar/ramus component of the TMJ prosthesis. (**A**) Shows a prosthesis with spherical condylar head. (**B**,**C**) Show prostheses with elliptical head of different dimensions. The condylar heads are designed to offer larger articulating surface area to avoid stress concentration at small area which may lead to more wear of the articulating surfaces of reconstructed TMJ. **Figure 10.** Different shapes of the condylar head of the custom-designed condylar/ramus component of the TMJ prosthesis. (**A**) Shows a prosthesis with spherical condylar head. (**B**,**C**) Show prostheses with elliptical head of different dimensions. The condylar heads are designed to offer larger articulating surface area to avoid stress concentration at small area which may lead to more wear of the articulating surfaces of reconstructed TMJ.

An important advantage of our patient-specific design approach is that the components can be precisely designed to withstand the loads encountered by unique anatomic condition. For the custom-designed condylar/ramus component, the center of rotation of its head can be moved vertically to correct the open bite deformity. The prosthetic condylar head can be placed such that its center of location in located inferior to that of the natural condyle it replaced, thereby allowing low-wear articulation of the reconstructed total TMJ and natural movements of the non-replaced contra-lateral TMJ. Ramal component can be shaped to

accommodate the amount of available mandibular host bone. The condylar heads can be designed in different shapes to offer larger articulating surface area to avoid stress concentration in small area of the articulating condylar head and fossa as illustrated in Figure 10. Figures 4–12 show custom-designed condylar/ramus prostheses of varying shape and size. These models demonstrate that our methodology of custom design enables the condylar component to conform to the anatomic situation of damaged and/or complex mandibular host bone. Though the shown designs of condylar component vary in size and shape per anatomic demands and surgeon's prescription, an important common design feature among all these models is that each device provides accurate adaptation to the host bone. *Materials* **2022**, *15*, x FOR PEER REVIEW 11 of 34

**Figure 11.** Modification of the custom-designed condylar/ramus component, shown in Figure 9, to include a novel feature; perforated notches protruding into host bone at implantation. (**A**) Shows a grove in the flat lateral surface of the condylar implant. The opposite side of this grove, as shown in (**B**), protrudes out of the medial surface as a notch with perforations. The enlarged views of medial notch and its perforations are shown in (**D**,**E**). The device also has pointed and perforated notch protruding from inferior surface of the implant's collar/neck. Perforated surfaces of these notches are designed to permit bone in-growth into the prosthesis after implantation to provide added stability. Dimensions of these notches can be customized to fit the size and shape of patient's native bone. Protrudes out of the medial surface as a notch with perforations (**C**). **Figure 11.** Modification of the custom-designed condylar/ramus component, shown in Figure 9, to include a novel feature; perforated notches protruding into host bone at implantation. (**A**) Shows a grove in the flat lateral surface of the condylar implant. The opposite side of this grove, as shown in (**B**), protrudes out of the medial surface as a notch with perforations. The enlarged views of medial notch and its perforations are shown in (**D**,**E**). The device also has pointed and perforated notch protruding from inferior surface of the implant's collar/neck. Perforated surfaces of these notches are designed to permit bone in-growth into the prosthesis after implantation to provide added stability. Dimensions of these notches can be customized to fit the size and shape of patient's native bone. Protrudes out of the medial surface as a notch with perforations (**C**).

One novel feature of our TMJ prostheses is the perforated notches protruding into the host bone. Figures 11 and 12 show a condylar/ramus component with its medial surface accurately following the geometric shape of patient's mandibular bone. Also seen protruding out of the medial surface of this device is a rectangular notch with perforations on its surface. This notch is intended to be placed in a custom-cut grove to be created on the lateral surface of mandibular ramus by the surgeon during implantation. Custom-designed cutting guides and templates can be provided to the surgeon to accurately create a small grove in the host bone. This intentional removal of native bone is performed in exchange of the opportunity for maximizing implant stability through bony ingrowth into perforated surfaces of the notch. Figures 11 and 12 show a perforated notch protruding from the inferior surface or collar of condylar neck. This notch is intended to be placed into a customcut grove in the superior surface of mandibular condyle/ramus resulting from osteotomy

(performed to remove damaged condylar head/neck). In addition to providing better stabilization, the notches also provide an avenue for load transfer between the prosthesis and host bone. This will reduce forces and resultant stress experienced by fixation screws which act as the only mode of load transfer between most TMJ prostheses, especially for the condylar devices in which the collar of condylar prosthesis does not adequately contact the host bone or the medial surface of the implant does not adapt accurately to the complex geometry of patient's mandible. Though having both medial and superior notches in the condylar prosthesis is likely to be advantageous from biomechanical viewpoint, this may make surgical implantation of the device more challenging for the surgeon. Therefore, it will be the surgeon's choice to have either one or both notches for condylar implant. **Figure 11.** Modification of the custom-designed condylar/ramus component, shown in Figure 9, to include a novel feature; perforated notches protruding into host bone at implantation. (**A**) Shows a grove in the flat lateral surface of the condylar implant. The opposite side of this grove, as shown in (**B**), protrudes out of the medial surface as a notch with perforations. The enlarged views of medial notch and its perforations are shown in (**D**,**E**). The device also has pointed and perforated notch protruding from inferior surface of the implant's collar/neck. Perforated surfaces of these notches are designed to permit bone in-growth into the prosthesis after implantation to provide added stability. Dimensions of these notches can be customized to fit the size and shape of patient's native bone. Protrudes out of the medial surface as a notch with perforations (**C**).

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**Figure 12.** Modification and refinement of custom-designed condylar/ramus component shown in Figures 9 and 11. (**A**,**C**) Show pre-drilled screw holes and a grove in the lateral surface of implant. As shown in (**C**), lateral surface of the device is flat and medial surface is shaped to match the host bone geometry. (**B**) Shows a perforated notch each protruding from the medial surface of the ramus and inferior surface of the implant collar/neck.
