TMJ Surgery and Biomechanical Engineering

Dr. Kirk recently presented a paper at the 2nd annual Bioengineering Conference on Tissue Engineering for the Temporomandibular Joint, in Broomfield, Colorado on November 4-7.  This meeting was sponsored by the NIH and NIDCR and invloved bioengineers and researchers interested in TM joint diseases and TMJ surgery.

Analysis of computer based model studies along with surgical data suggests that the TMJ develops impingement conditions that are very similar to impingement dysfunction (rotator cuff tearing) of the shoulder.  The unique biomechanics of the TMJ and the fact that the main “cartilage” of this joint system is in reality fibro-cartilage tissue with a low threshold for shear and torque destruction; patients with true orthopedic dysfunction and a history of osteoarthritis develop this condition two to three decades younger in life than patients with similar issues in other joint systems (knee, shoulder).

Examples of MRI of the TMJ and impingement’s are presented here in this blog.  Impingement’s are diagnosed by examining the joint in 3 directions, sagittal and coronal images.  Developmental forms of impingement may be due to asymmetries of the base of the skull relative to the articulation with the jaw, this is prevalent in younger patients.  This type is important to diagnose in younger patients, especially those who become symptomatic during growth and development years of life.  Unfortunately, many of these patients go undiagnosed by dentists and orthodontists treating this age patient during their growth and developmental years.  Schellhas and Piper have documented a high percentage of patients in adolescence with derangement and skeletal malocclusion.  Unfortunately, treating orthodontists can be uncomfortable with imaging patients during their treatment.  It is this exact population of patient that needs to be identified early to prevent significant orthopaedic and chronic pain conditions from developing.

Computer models help suggest that both normal fuction and dysfunction during chronic instability can lead to development of impingement which can require TMJ surgery to correct progession of irreversible damage.

NORMAL CORONAL TMJ AND NO IMPINGEMENT: Note Centered position of condyle (ball) within fossa (socket) of joint. Joint space between these structures is even and respective shape/size of fossa and condyle match. When this match is maintained throughout all joint range of motion, orthopedic stability and good function is maintained.

SEVERE TYPE I IMPINGEMENT: Compared to normal, note the peaked, projecting bone mass downward and into the lateral aspect of the condyle. There is no measurable joint space and a rupture of the disc/capsule is present. Patient's main complaint other than longstanding pain and joint instability was the inability to move the jaw from side to side without extreme pain and the perception of "locking"

TYPE II IMPINGEMENT: This view shows a dynamic change from when teeth are together ( left film) to attempted mouth opening (right film). Notice dramatic change on right where there is one point of bone to bone contact between the lateral rim of the fossa and the lateral pole of the condyle during mouth opening and condyle translation (sliding forward). The nature of such an impingement is delivery of concentrated force over small area during joint movement which can create tears in the attachment of the disc/capsule during normal function. This type of impingement is most likely due to growth and development differences between the fossa or socket of the joint system which develops as does the base of the skull, and the condyle or ball component which develops as the lower jaw develops. This type of impingement is often seen in young patients, especially those in their teenage or advancing growth and development years.

Tags: tmj, TMJ adolescence, TMJ Dentist, TMJ Impingement, TMJ MRI, TMJ Orthodontist, TMJ Surgery, TMJ Surgury