This study describes the clinical variables in 61 patients following total alloplastic temporomandibular joint reconstruction (TJR) in which the Biomet Microfixation Patient-Patient-Matched TMJ Implant was used. All patients were classified using the Wilkes classification. The visual analogue scale score for jaw pain intensity, the maximum inter-incisal opening (MIO), and the frequency of adverse events were recorded during follow-up; the mean follow-up was 14.2 ± 8.6 months. Significant improvements were found in the MIO ( P < 0.0005), except at the 3-year follow-up. Additionally, a significant reduction in pain was observed both short and long term ( P < 0.0005). The incidence of adverse events was low (seven of the 81 alloplastic joints); two joints needed revision. TJR appears to be a relevant treatment option in patients with a broad range of temporomandibular joint disorders in whom none of the joint components are salvageable because of significant disease. Our patients gained an almost normal range of mouth opening and experienced a significant reduction in pain. Our results are promising, however TJR is associated with some side effects. TJR should be considered when less invasive procedures fail and a comprehensive presurgical work-up has been performed. Ongoing prospective studies are needed to consolidate the possible significant treatment outcomes.
Disorders of the temporomandibular joint (TMJ) occur frequently, with a prevalence of between 15% and 18% ; these can be the result of disease or trauma, or may be of unknown aetiology. In those cases in which non-invasive therapy and minor surgical procedures fail to improve function or reduce pain and the patient remains functionally and psychosocially affected, surgical replacement of the TMJ with an alloplastic implant may be an alternative.
Historically, prosthetic reconstruction of the TMJ has been plagued with device failures, including heterotopic bone formation, pain, and foreign body formations. Numerous data are available concerning the outcome of long-term follow-up, although the data only represent two of the three US Food and Drug Administration (FDA)-approved systems on the market today. Thus, the current data only concern the TMJ Concepts Prosthesis (TMJ Concepts Inc., Ventura, CA, USA) and the Biomet Microfixation TMJ Replacement System (Biomet Microfixation, Jacksonville, FL, USA). Much of the data support a possible positive outcome for the use of alloplastic joints as an end-stage treatment option.
Mercuri et al. published a 14-year follow-up, showing a survival rate of 90%. Recently, an article by Giannakopoulos et al. indicated the need for appropriate patient selection for TMJ alloplastic replacement and that this treatment should only be an option for patients who have no other viable medical or more conservative surgical alternatives.
The Christensen TMJ Fossa–Eminence Prosthesis System differs from the two other systems, having a metal-to-metal contact between the fossa component and the head of the ramus component. The TMJ Concepts Prosthesis is a custom-fitted prosthesis system.
Biomet Microfixation manufactures and distributes both stock and custom implants. The stock implant is approved and available for use in approximately 50 countries worldwide. The Biomet stock joint was first used in 1995 as part of an FDA-regulated clinical trial in which 442 joints were implanted. The Biomet custom joint has been used since 2007 and is not yet FDA-approved.
The Biomet Microfixation custom implant is a patient-matched version of the stock implant. It contains the same components and materials. The custom implant is intended for use in patients with a unique anatomy and in cases where the stock implant does not fit. Three-dimensional (3D) computed tomography (CT) scan reconstructions are used to map the individual patient’s geometry, and the custom implant is machined to specifically match the unique geometry of the patient.
In this study we evaluated the use of the Biomet Microfixation Patient-Matched TMJ Implant.
Materials and methods
The patients attended up to nine appointments, one before alloplastic reconstruction, followed by appointments at 1 week, 1, 3, 6, 12, 18, 24, and 36 months after alloplastic TMJ reconstruction. The local ethics committee approved this prospective single-centre study, which was conducted in concordance with the Declaration of Helsinki. Two consultants from the department of radiology described all CT DICOM (Digital Imaging and Communications in Medicine) data. Ten patients could not be staged with the Wilkes classification (fracture, ankylosis, revisions, and benign neoplasms). At each session, a visual analog scale (VAS) was used to evaluate the pain level. Patients were asked to score the pain from 0 to 10, where 0 is absolutely no pain and 10 is the worst pain imaginable. Maximum inter-incisal opening (MIO) was evaluated clinically and recorded: a ruler was used to measure the MIO (the total range of movement of the central incisors in the upper jaw and the central incisors in the lower jaw) in millimetres. In addition, the frequency of adverse events was recorded.
The main objective was to obtain safe and reliable data on patients treated with the Biomet Patient-Matched TMJ Implant. The primary metrics monitored included preoperative and postoperative pain, MIO, and adverse events.
All surgeries were performed by one of the authors (EA). Data collection was undertaken by all members of the surgical staff at the department of oral and maxillofacial surgery. All observers were calibrated according to overall guidelines. Calibration was done using educational sessions with practical tests and audits of relevant patient files.
Inclusion criteria were the following: osteoarthritis; traumatic arthritis; rheumatoid arthritis; ankylosis; revision procedures where other treatments have failed (e.g. alloplastic reconstruction and autogenous grafts); avascular necrosis; multiple operated joints; fracture; functional deformity (e.g. following poor healing following condylar neck fracture); degenerated or resorbed joints with severe anatomical discrepancies; developmental abnormality (e.g. hemifacial microsomia); patients aged ≥18 years; patients with a minimum of 3 months of follow-up.
Exclusion criteria were the following: active or chronic infection; patient conditions where there is insufficient quantity or quality of bone to support the components; systemic disease with increased susceptibility to infection; partial TMJ joint reconstruction; known allergic reaction to any materials used in the components; patients with mental or neurological conditions who are unwilling or unable to follow postoperative care instructions; skeletally immature patients; patients with severe hyper-functional habits (e.g. clenching, grinding, etc.); patients with a foreign body reaction to previous implants.
All patients except patients with ankylosis or benign tumours had a history of normal conservative therapy (splints, muscle exercise, pain medications, etc.) for TMJ disorders ( Fig. 1 ). Furthermore, the vast majority of the patients had undergone minor surgical interventions, such as arthrocentesis and/or arthroscopy (in 66 out of 81 joints) ( Fig. 2 ).