Novel Guide Device for Temporomandibular Joint Arthroscopy (#2015043)

Introduction

The temporomandibular joint (TMJ) is the joint that connects your lower jaw to your skull. When this joint is injured or damaged, it can lead to localized pain, limited mouth opening, interference with mouth closing, and joint noises. The general term describing these conditions is temporomandibular disorders (TMDs). Causes of TMDs include head or facial trauma, misalignment of the teeth or jaw, teeth grinding, poor posture, stress, arthritis, rheumatoid disorders, gum chewing, and in many cases, unknown cause. TMDs affect patient's quality of life as they interfere with daily activities such chewing, yawning, and talking.

Arthroscopy of the TMJ is a minimally invasive surgical intervention aimed at diagnosis and treatment of many joint disorders. It was first described in 1974, and since then has gained great popularity and become an acceptable therapeutic modality for various joint pathologies. Arthroscopy of the TMJ is broadly divided into two types; 1) Diagnostic-Lavage Arthroscopy , and 2) Operative Arthroscopy . Mild and early joint disorders may benefit from Diagnostic-Lavage Arthroscopy, while advanced joint pathologies will require either Operative Arthroscopy or open surgery of the joint.

Diagnostic-Lavage Arthroscopy is a relatively simple surgical procedure, and is routinely performed in many departments of Oral and Maxillofacial surgery. It involves the introduction of an arthroscope into the joint cavity. Saline is flushed through the arthroscope into the joint space to enable visualization, and simulteneously provides lavage, hydrodistention, and washout of inflammatory substances, giving a therapeutic side-effect for the procedure. The entry point into the TMJ is located immediately in front of the ear, and this surface anatomical landmark makes the intoduction of the arthroscope relatively easy.

Operative Arthroscopy manadates the insertion of a second cannula into the joint space – a working cannula, through which surgical instruments are introduced. This working cannula has to be inserted in a way that it would be readily visualized by the arthroscope upon entering the joint cavity and throughout the surgical procedure. In addition, it should be oriented in such a manner that enables surgical instrumentation and manipulation of joint structures. As oppposed to the puncture site of the arthroscope where it is almost constant in all individuals (~1 cm in front of the tragus of the ear) and easily palpable (the cheek bone in front of the ear), there are numerous options for the skin puncture site for the working cannula, and identifying the ideal puncture site is a challenging task for the surgeon. The ideal puncture site of the working cannula may lie at any point within a diameter ranging from 2 to 4 cm from the arthroscope. This is because great variability exists among individuals with regard to the anatomy and dimensions of the anterior part of the cheek, the area infront of the TMJ. In addition to the entry point, determinimg the angulation vector and the insertion depth are two other factors that add to the complexity of the procedure.

This anatomical variability makes the learning curve of proper introdution of a working cannula long and challenging. Operative Arthroscopy thus is a more complicated surgical procedure that requires higher degrees of expertise.

The Need 

For the working cannula to be readily visualized and functional, skin puncture site, angulation of insertion, and insertion depth must be accurate and precise. If the working cannula is improperly inserted so it becomes difficult or impossible to direct an instrument through it to be visualized by the arthroscope, it becomes necessary to remove and re-insert it, leading to greater trauma and increased surgical risks and morbidity to the patient, as well as excess leakage of saline into surrounding tissues, preventing the joint cavity from being effectively distended and dramatically shortening operation time. Generally, two or three succeeding failures to properly insert the working cannula lead to suspension of the TMJ operative arthroscopy.

An additional challenge is maintaining the relative orientation of the tips of the arthroscope and the working cannula in three-dimension throughout the operative procedure, so the arthroscope can have continuous and uninterrupted line of sight to the surgical instruments introduced through the working cannula. In the operation theater, much effort is made to ensure that the relative orientation is unchanged; usually the main surgeon has to hold both the arthroscope and the working cannula steady with both hands, while an assistant surgeon is tasked with introducing and manipulating the surgical tools.

Our Innovation

We have designed a guide device that enables accurate insertion of the working cannula relative to the arthroscope, and maintains this relation throughout the procedure. The device in essence is a double parallelogram that the arthroscope and working cannula are mounted on. After inserting the arthroscope into the joint cavity, the guide device is mounted on the part of the arthroscope remaining outside the joint. The other arm of the parallelogram (device) receives the working cannula and directs it into the joint cavity. The working cannula in this way reaches exactly the spot where the guide device directs it to, which is a location with optimal spatial orientation relative to the arthroscope, achieving both immediate visualization and ideal relations for instrumentation. After proper insertion of the working cannula by the guide device and visualizing it by the arthroscope, the working cannula can be locked in this fixed orientation relative to the arthroscope, allowing the surgeon to hold the arthroscope and working cannula with one hand using the guide device, and performing the surgical instrumentation with the other hand.

After mounting the arthroscope and working cannula on the guide device and achieving optimal spatial orientations, the arthroscope and working cannula have a full range of motion in space and can be moved by the surgeon in three dimensions, while keeping optimal configuration between them:

• The guide device may be opened by widening the angle between the arms or closed by narrowing the angle between the arms, while maintaining direct visualization of the working cannula by the arthroscope.
• Flexible connectors of the arthroscope and working cannula to the guide device enable additional micro-movements for the arthroscope and working cannula without opening or closing the guide device and meanwhile maintaining optimal orientation between them and keeping the working cannula within the visual field of the arthroscope.

The Product

A prototype has been manufactured from stainless steel and autoclave-able polymeric materials. It proved accurate on anatomical models. The device was tried in clinical setting with human patients and proved accurate and successful in three consecutive patients . No side effects occurred. The subjective experience of the surgeon was positive, and the impression was that the device:

• Improved the predictability of the insertion of the working cannula
• Achieved optimal spatial relations between the arthroscope and working cannula
• Enabled the senior surgeon to hold both the arthroscope and working cannula with one hand (via the device) while using the other hand to hold the surgical instruments and insert/remove them through the working cannula.

The device can be mounted and dismounted at any time during the operation; before and after introduction of both, the arthroscope and working cannula.

Applications

In addition to arthroscopy of the temporomandibular joint, the guide device can be used in arthroscopic surgery of all other joints of the body. Whenever accurate insertion of the working cannula to a specific location of the joint is desired, or in any case fixation of the spatial relations between the arthroscope and working cannula steady is warranted (while maintaining micromotion of both), the device can be successfully used to achieve these goals.

Advantages

• Entering joint cavity with one single puncture → Minimal violation of joint capsule → Improved hydro-distention of joint cavity → Improved vision and easier surgical instrumentation.
• Minimal puncturing of skin → Decreased surgical risks associated with facial nerve injury, ear injury, and scarring of skin.
• Minimal sweeping in joint cavity looking for the working cannula → Prevents scuffing of joint lining and iatrogenic damage to intra-articular tissues.
• More simple, predictable, and easy operation → Enables the novice arthroscopist of performing Operative Arthroscopy.
• More simple, predictable, and easy operation → Allows patients with various TMJ disorders to undergo minimally invasive arthroscopic intervention instead of open surgery of the joint.
• Fixating the arthroscope and working cannula in 3D → The main surgeon can perform the surgical instrumentation instead of being confined to merely stabilizing the relations between the cannula and arthroscope throughout the operation.
• Decreased morbidity for the patient in terms of pain, swelling, and hospitalization time.
• Less operative time in the surgical theatre.
• More predictable procedure.

The Market

The prevalence of TMDs is between 5% and 12% of the general population. Unusual for chronic pain conditions, the prevalence rates of TMJ disorders are higher among younger persons. TMJ disorders are at least twice as prevalent in women as men, of the general population. Approximately 5% of them will benefit from a surgical intervention.

The global Craniomaxillofacial devices market size was valued at USD 2.45 billion in 2018 and is expected to witness a CAGR of 6.0% during the forecast period. Increasing demand for minimally invasive surgeries is expected to drive the demand for Craniomaxillofacial (CMF) devices.

Craniomaxillofacial devices market products include temporomandibular joint (TMJ) replacement, CMF distraction, cranial flap fixation, plate and screw fixation, bone graft substitutes, and thoracic fixation. Plate and screw fixation dominated the product segment with over 70% revenue share in 2014. This dominance is attributed to its wide usage in various surgical procedures such as deformity correction, Orthognathic surgery, tumor removal and pediatric surgeries. Temporomandibular joint (TMJ) replacement devices is expected to be one of the fastest growing segment over the forecast period due to increasing incidences of road accidents and sport injuries leading to cranial and facial fractures.

Global Craniomaxillofacial Devices Market: Key Players

The key players in the global craniomaxillofacial devices market players are Johnson & Johnson Services, Inc., Stryker Corporation,  Zimmer Holdings, Inc., KARL STORZ SE & Co. KG, ,  B. Braun Melsungen AG, CONMED, Invibio Ltd,  KLS Martin LP, Medtronic, Inc., Medartis AG, Integra LifeSciences Holdings Corporation, Boston Medical Products, Inc. Olympus Corp., Arthrex, Inc., Arthrocare Corp., BIOTEK, Covidien Plc, Depuy Synthes, ConMed Corporation, Cannuflow, CorTek Endoscopy Inc., Stryker Corporation and Smith and Nephew Plc.