Accuracy of fit analysis of the patient-specific Groningen temporomandibular joint prosthesis

Abstract

Total joint replacement (TJR) with a prosthesis can be indicated for patients with severe temporomandibular joint (TMJ) dysfunction. Surgical accuracy is necessary for correct translation of the preoperatively predicted functional outcome, wear, and biomechanical behaviour of the patient-specific TMJ-TJR prosthesis. This study describes the first clinical applications of the patient-specific TMJ-TJR prosthesis according to the Groningen principles (G-TMJ-TJR), which was developed and validated in a prior human cadaver test study. The aim of this study was to validate the accuracy of placement of the patient-specific G-TMJ-TJR in the clinical setting. It was hypothesized that a virtual surgical plan (VSP) combined with guided placement of the patient-specific G-TMJ-TJR would be performed as predictably and accurately as in the prior cadaver series. All patients who received a VSP-based patient-specific G-TMJ-TJR between December 2017 and March 2020 were included in this study. The accuracy analysis was based on postoperative cone beam computed tomography (CBCT) data. All 11 prostheses could be inserted using routine pre-auricular and retromandibular surgical approaches. Analysis of the VSPs and postoperative CBCTs showed an average three-dimensional deviation of 1.07 mm (standard deviation 0.46 mm, range 0.33-1.91 mm) for all of the fossa and mandibular components. The patient-specific G-TMJ-TJR can be applied predictably and accurately in a clinical setting.

Evolutionary Steps in the Development of a Patient-specific Temporomandibular Joint Prosthesis

“…This was done by allowing the replaced side to move synchronously with the other joint during both rotational movements with the other joint and vice versa, as well as during translative movements (e.g., when performing movements of opening and closing, both the healthy and replaced condyle should move without causing interferences in each other’s joint space). In comparison with the Groningen TMJ prosthesis, where a more bulky fossa component with a low rotational point is used, 16 the articular surface of the TMJ is placed more cranial, to allow for a more natural movement. The same study, concerning the Groningen TMJ prosthesis, did indicate that a more accurate planning and prediction was feasible thanks to the patient-specific fit.…”

Four-Dimensional Determination of the Patient-Specific Centre of Rotation for Total Temporomandibular Joint Replacements: Following the Groningen Principle

“…To overcome this effect, the Groningen TMJ-TJR prosthesis was developed [7][8][9]. Apart from its unique feature that allows for free translational movement of the neo-disc, the prosthesis applies a lowered centre of rotation (CR) in relation to the anatomical condylar centre [8].…”

“…To overcome this effect, the Groningen TMJ-TJR prosthesis was developed [7][8][9]. Apart from its unique feature that allows for free translational movement of the neo-disc, the prosthesis applies a lowered centre of rotation (CR) in relation to the anatomical condylar centre [8]. Prior research suggested that a lowering of 15 [mm] in relation to the condyle would be optimal as a fixed CR for unilateral TMJ prostheses [3].…”

“…This study was, however, based on 2D optical movement tracking with no direct relation to the bony anatomy and thus the condyles of the mandible [10]. The Groningen TMJ-TJR prosthesis has been available as a patient-specific (PS) device since 2017, opening doors to also personalise the position of the CR [8]. Figure 1 illustrates the effect of a lowered centre of rotation with the Groningen TMJ-TJR prosthesis.…”

“…However, as mentioned, the movement of a TMJ reconstructed by means of a TMJ-TJR prosthesis should predominantly show rotational movement [4]. Since any translational movement cannot be expected to occur in the reconstructed TMJ due to a lack in lateral pterygoid muscle function, we chose to analyse a fixed centre of rotation, even though the Groningen TMJ-TJR allows for some free translation of the neo-disc [8].…”