The literature on total alloplastic temporomandibular joint (TMJ) reconstructions is encouraging, and studies on total alloplastic TMJ replacements outcomes showed acceptable improvements in terms of both pain levels and jaw function. Nevertheless, some adverse events, such as heterotopic bone formation around the implanted prosthesis, may occur. In consideration of that, the present manuscript describes a case of heterotopic bone formation around a total temporomandibular joint prosthesis, which occurred several years after the implant.
The present manuscript describes a case of heterotopic bone formation around a total TMJ prosthesis, which occurred several years after the implant in patients, who previously underwent multiple failed TMJ surgeries.
Ten years after the surgical TMJ replacement to solve an ankylotic bone block, the patient came to our attention again referring a progressive limitation in mouth opening. A computerized tomography showed evidence of marked heterotopic bone formation in the medial aspects of the joint, where a new-born ankylotic block occupied most part of the gap created by resecting the coronoid process at the time of the TMJ prosthesis insertion.
Despite this adverse event has been sometimes described in the literature, this is the first case in which its occurrence happened several years after the temporomandibular joint replacement. It can be suggested that an accurate assessment of pre-operative risk factors for re-ankylosis (e.g., patients with multiple failed temporomandibular joint surgeries) and within-intervention prevention (e.g., strategies to keep the bone interfaces around the implant separated) should be better standardized and define in future studies.
Despite the catastrophic early experiences
on alloplastic materials and prosthetic systems for temporomandibular
joint (TMJ) rehabilitation (i.e. Proplast-Teflon/Silastic) [
In the new millennium, several studies on
the outcomes of new-generation total alloplastic TMJ replacement showed
acceptable improvements in terms of both pain levels and jaw function,
thus making these interventions worthy of further evaluation [
Since the publication of that last review,
some others papers have been published with longer follow-up periods, in
support of the favourable outcomes of total TMJ replacement [
In consideration of that, the present manuscript describes a case of heterotopic bone formation around a total temporomandibular joint prosthesis, which occurred several years after the implant.
In 2003, a 35 year-old female patient was
referred to the Department of Maxillofacial Surgery, University of
Padua, Italy, for the treatment of a severe mouth opening restriction
and pain in the TMJ. The patient had no other comorbidity and was taking
only pain medication (NSAIDs) when needed; she gave a history of pain in
the TMJ area and had undergone two previous operations (i.e., a disc
repositioning surgery at the age of 25 years, and a discectomy with
condylar remodelling at the age of 32 years) at other maxillofacial
surgery clinics. After the second surgery, the range of mandibular
movements decreased rapidly, and the patient was referred to our clinic.
The maximum mouth opening was 5 mm, with absence of end-feel distance,
and computerized tomography showed ankylosis of the left TMJ (
Computerized tomography showing ankylosis of the left tempormandibular joint.
At that time, several surgical options were
considered to relieve TMJ ankylosis and restore jaw function, ranging
from the quite abandoned gap arthroplasty to interpositional
arthroplasty, which provided the insertion of a biological (temporalis
fascia, temporal muscle flap) or non-biological material (acrylic,
silastic) between the bone structures [
Considering these concerns, a total TMJ prosthesis in the left joint was preferred to the other surgical options, and the patient was scheduled for surgery.
The total TMJ replacement system is a “ball
and socket” type prosthetic joint similar to a hip implant. The total
TMJ replacement system comprises three components [
The condylar (or mandibular) implant, made of metal Cobalt-Chromium-Molybdenum (Co-Cr-Mo) alloy or Titanium alloy. In both cases the implants have a roughened titanium porous coating on the implant surface that contacts bone. Co-Cr-Mo alloy contains nickel.
The fossa implant, made of a hard, plastic polyethylene. The fossa is made of high density polyethylene that has shown excellent wear resistance during mechanical testing.
The screws, made of titanium alloy are used to attach both the condylar and the fossa implants to bone.
In this case a total TMJ stock prosthesis
was inserted (Biomet/Lorenz, Warsaw, IN, USA) [
Two surgical phases characterized the
intervention, viz., the removal of the ankylotic block and the
positioning of the TMJ prosthesis. Thus, both preauricular access to the
TMJ and temporal bone and a posteroinferior submandibular incision for
access to the mandibular ramus were required. The superior incision has
a 45o release into the temporal hairline, and the dissection is kept as
posterior as possible to avoid the facial nerve. The inferior incision
was almost vertical, viz., perpendicular to the lower two-thirds of the
posterior border of the ramus). Once access to the TMJ was gained
through the preauricular incision, the release of the ankylosis was
performed (
The intermaxillary fixation was then removed
and the patient’s mandible was manipulated to ensure that no
obstructions to joint movement or improper fitting between the two
prosthetic components were present. The patient was also forced
intra-operatively to maximum mouth opening, in order to break adhesions
on the contralateral side. Only after verifying the correct functioning
and freedom of movement of the implant, the patient was then sutured and
a control ortopantomography was taken (
Intraoperative photograph showing aggressive excision of the fibrous and/or bony mass.
Ortopantomography performed immediately after surgery.
In this case, the postoperative course was
uneventful, and only pain medication (NSAIDs as needed) and antibiotics
(amoxicillin/clavulanate cp 1g every 12 hours for 7 days) were
prescribed. There was no motor deficit on either side of the face.
Functional rehabilitation was started one week after surgery, by a
combination of active and passive exercises. In particular, the patient
was given an intensive regime of passive motion (TheraBite Jaw Motion
Rehabilitation System®, Therabite, Philadelphia, PA, USA),
which are fundamental to improve jaw mobility after surgical procedures
on the TMJ. The patient was asked to perform passive exercises for the
first three months after surgery, and vigorous active physiotherapy was
then introduced to maintain the mobility. A cycle of five injections
(one per week) of 1 ml low-molecular weight hyaluronic acid (Sinovial®,
IBSA Farmaceutici Italia, Lodi, Italy) injections was also provided to
the contralateral TMJ according to the technique in use at that moment
[
and during a phone contact two years after the last follow-up assessment she declared everything was fine, and that she was able to open the mouth straight without feeling pain.
Ten years after the surgical TMJ
replacement, the patient came to our attention again referring a
progressive limitation in mouth opening. A computerized tomography
showed evidence of marked heterotopic bone formation in the medial
aspects of the joint (
Computerized tomography showing heterotopic bone formation around the TMJ prosthesis.
Computerized tomography showing the new bone in the medial aspects of the joint.
Data on total TMJ replacements suggest that
a history of multiple previous failed operations is the most common
indication for joint replacement, and patients with severe
osteoarthritis, inflammatory arthrosis, connective or autoimmune
disease, ankylosis, absent or deformed structures, congenital
deformities, and chronic pain also underwent the total joint replacement
[
Despite the increasing evidence in support
of long-term positive outcomes of TMJ total replacement prostheses, the
occurrence of some unfavourable events cannot be disregarded [
The present report describes a case of heterotopic bone formation around a total temporomandibular joint alloplastic prosthesis. Despite this adverse event has been sometimes described in the literature, in this particular case its occurrence happened several years after the temporomandibular joint replacement. Based on this observation, even if keeping in mind the low scientific relevance of this single report, it can be suggested that an accurate assessment of pre-operative risk factors for re-ankylosis (e.g., patients with multiple failed temporomandibular joint surgeries) and a within-intervention prevention (e.g., strategies to keep the bone interfaces around the implant separated) should be better standardized and define in future studies.
The author declares that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.