Evaluating the Accuracy and Safety of a Locator-Positioner Guide Device to Assist in Temporomandibular Joint Arthroscopy
Phase: NA
Conditions: Temporomandibular Joint Disc Displacement, Temporomandibular Joint Disorders, Temporomandibular Joint Dysfunction Syndrome
Sponsor: Sheba Medical Center

Research protocol 
 
 
Assessing the precision of a device intended to assist surgeons during 
temporomandibular joint arthroscopy by optimizing the placement  
of the working cannula in relation to the arthroscope 
 
 
 
Date 9.3.2018 
Protocol number 4657-17-SMC 
Author of the protocol: Dr. Waseem Abboud, ID 049031255  
 
 
 
 
The initiator of the study, the main researcher, and the writer of the protocol: 
 
Dr. Waseem Abboud 
Senior Surgeon and Head of TMJ Unit, Department of Oral and Maxillofacial Surgery 
Senior Surgeon, Institute of Movement Disorders, Department of Neurology 
Sheba Medical Center, Aﬃliated to Tel Aviv University, Tel Hashomer, Israel 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Protocol Synopsis: 
Arthroscopy of the temporomandibular joint (TMJ) is a well-established surgical procedure 
for treating various TMJ disorders. The technique involves inserting an arthroscope into the 
joint cavity, followed by the insertion of a working cannula through which the surgeon's 
instruments pass. Successfully inserting the working cannula requires advanced surgical skills 
and extensive clinical experience, as mastering this technique has a steep learning curve. 
Incorrect placement of the working cannula can cause iatrogenic damage to the TMJ and 
adjacent structures, including the facial nerve and ear. It is generally accepted that if the 
working cannula cannot be inserted successfully after 2-3 attempts, the procedure should be 
halted. 
In our department, we developed a guide device we called Locator-Positioner (LOPO) to aid 
surgeons in precisely inserting the working cannula into the joint cavity. This device makes 
the insertion process predictable and straightforward. The aim is to ensure the smooth and 
accurate placement of the working cannula, allowing it to be immediately visible through 
the arthroscope, and eliminating unnecessary movements that could harm the joint tissue 
and nearby structures. 
The prototype of the LOPO was tested on anatomical models and proved to be highly 
accurate. In all insertion attempts, the working cannula – guided by the device – was placed 
precisely and became immediately visible by the arthroscope.  
This pilot study aims to recruit up to 10 patients to test the LOPO device in a clinical setting. 
 
 
Background: 
Temporomandibular joint (TMJ) problems can present a wide range of symptoms, including 
diﬃculty opening the mouth, inability to close the mouth, noises during jaw movement, 
temporary mechanical locking episodes, and pain in the TMJ and masticatory muscles. These 
issues can adversely aﬀect daily activities like eating, speaking, and yawning, thereby 
reducing patients' quality of life. 
Arthroscopy of the TMJ was ﬁrst introduced in 1976 and has since become a recognized 
therapeutic method for treating TMJ issues. The procedure begins with the insertion of the 
arthroscope into the posterior part of the joint cavity. Subsequently, a "working cannula" is 
placed in the anterior part of the joint cavity. The surgeon's instruments are then inserted 
through this working cannula during the procedure. 
Similar to arthroscopy performed on other joints like the knee and shoulder, a tube is 
connected to the arthroscope during the procedure to ﬂow a ﬂushing ﬂuid (isotonic saline or 
similar ﬂuids) into the joint cavity, maintaining constant pressure within the joint space. The 
saline infusion is automatically triggered when the pressure drops. In TMJ surgeries, a ﬂuid 
pressure of around 40 PSI is used. This lavage system ensures continuous hydro-distension 
(inﬂation with water) of the joint cavity, enabling clear vision and facilitating the surgeon's 
work. If the ﬂuid pressure inside the joint drops, the joint capsule collapses onto the intra-
articular structures, obstructing the view through the lens of the arthroscope.  

As previously mentioned, the initial stage of the operation involves inserting the arthroscope 
into the rear part of the TMJ. This step is relatively straightforward because the proximity of 
the joint to the ear provides a visible landmark for the surgeon. The anatomical landmarks 
constituting the ear, eye, and cheekbone aid this approach. Conversely, inserting the working 
cannula into the front part of the joint is more challenging due to signiﬁcant anatomical 
variation among individuals and lack of easy landmarks to rely on. Therefore, facial skin 
landmarks cannot reliably guide this insertion and the triangulation technique was described 
as an alternative. This technique involves creating a spatial relationship between three 
points: the arthroscope, the target area within the joint, and the working cannula’s entry 
point. The term "triangulation" refers to the coordination between the visual axis of the 
arthroscope and the working cannula’s path. The surgeon uses the arthroscope to guide the 
working cannula to the correct position within the joint. Successful insertion of the working 
cannula hinges on three conditions: 1) ensuring it avoids damaging nearby vital structures 
both during and after insertion, 2) positioning it directly within the arthroscope's ﬁeld of 
view in the front part of the joint for immediate visibility, and 3) achieving successful 
insertion on the ﬁrst attempt, with a maximum allowance for additional 1 or 2 attempts if 
necessary. 
Successful arthroscopy relies on accurately placing the working cannula ideally on the ﬁrst 
attempt, and at most on the second or third attempts. Multiple attempts to insert the 
cannula can lead to puncturing of the joint capsule, causing leakage of the irrigation ﬂuid 
(saline) and swelling of the face. This edema not only discomforts the patient but also 
compromises suﬃcient inﬂation (hydro-distension) of the joint cavity, thereby complicating 
the surgical procedure. Scientiﬁc literature generally advises halting the procedure after few 
unsuccessful attempts to insert the working cannula into the correct position. 
Furthermore, repeated attempts increase surgical risks, including potential damage to facial 
nerve branches, blood vessels in the face, and the auditory canal, as well as heightened 
post-operative pain. 
 
 
Bibliography: 
- 
The main investigator’s experience in TMJ arthroscopy: 
o Abboud W, Yarom N, Yahalom R, Joachim M, Reiter S, Koren O, Elishoov H. 
Comparison of Two Physiotherapy Programs for Rehabilitation after 
Temporomandibular Joint Arthroscopy. International Journal of Oral and 
Maxillofacial Surgery. 2018; 47: 755-761. 
o Abboud W, Hirschorn A, Yahalom R. The Role of Arthroscopy in the Diagnosis 
and Treatment of Temporomandibular Joint Disorders. The Journal of the 
Israel Dental Association. 2016; Vol. 33, No. 3.  
o Abboud W, Nadel S, Yarom N, Yahalom R. Arthroscopy of the 
Temporomandibular Joint for the Treatment of Chronic Closed Lock. Israel 
Medical Association Journal. 2016; 18: 397-400. 

o Abboud W, Givol N, Yahalom R. Arthroscopic Lysis and Lavage for Internal 
Derangement of the Temporomandibular Joint. Annals of Oral and 
Maxillofacial Surgery. 2015; 5:158-162. 
o Abboud W, Yahalom R, Givol N. Treatment of Intermittent Locking of the Jaw 
in Wilkes Stage II Derangement by Arthroscopic Lysis and Lavage. Journal of 
Oral and Maxillofacial Surgery. 2015; 73:1466-1472. 
o Abboud W. Novel Guide Device for Temporomandibular Joint Arthroscopy. 
International Journal of Oral and Maxillofacial Surgery. 2020; 49: 1217-1219. 
- 
Surgical techniques for introducing the arthroscope and working cannula into the 
TMJ: 
o Monje Gil F, Hernandez Vila C, Moyano Cuevas JL, Lyra M, Pagador JB, 
Sanchez Margallo FM. Validation of a simulator for temporomandibular joint 
arthroscopy. Int J Oral Maxillofac Surg. 2016 Jul;45(7):836-41. doi: 
10.1016/j.ijom.2016.01.010. Epub 2016 Feb 3.   PubMed ID: 26850940 
o Verde L, Munoz-Guerra MF, Rodriguez-Campo FJ, Escorial V. 
Temporomandibular Joint: Approach to the Intermediate Space by 
Triangulation With Transillumination Reference. J Oral Maxillofac Surg. 2023 
Jun;81(6):684-688. doi: 10.1016/j.joms.2023.02.008. Epub 2023 Mar 
6.   PubMed ID: 36893793 
o Peserico-DalFarra P, Gagliardi-Lugo AF. Training simulation for oral and 
maxillofacial surgeons based on the techniques of arthroscopy in the 
temporomandibular joint. Br J Oral Maxillofac Surg. 2019 Nov;57(9):929-931. 
doi: 10.1016/j.bjoms.2019.08.003. Epub 2019 Aug 22.   PubMed ID: 31445774 
o Slavin AB. Comments on "single-cannula technique for operative arthroscopy 
using holmium:YAG laser". J Oral Maxillofac Surg. 2012 May;70(5):1014; 
author reply 1014. doi: 10.1016/j.joms.2012.02.011. No abstract 
available.   PubMed ID: 22538020 
o McCain JP, Hossameldin RH. Advanced arthroscopy of the 
temporomandibular joint. Atlas Oral Maxillofac Surg Clin North Am. 2011 
Sep;19(2):145-67. doi: 10.1016/j.cxom.2011.06.001. No abstract 
available.   PubMed ID: 21878249   
 
 
Reasoning behind conducting the experiment:  
We developed a guide device referred to as Locator-Positioner (LOPO) designed to assist 
surgeons in accurately and precisely inserting the working cannula into the TMJ. Following 
the initial insertion of the arthroscope into the joint, which is a relatively straightforward 
procedure, the LOPO is attached to the outer part of the arthroscope (remaining external to 
the skin of the face). The LOPO then provides guidance to the surgeon on where and how on 
the skin to insert the working cannula to precisely align with the end of the arthroscope 
found within the joint. 

Importantly, the LOPO does not enter the patient's body at any point during the operation 
and should not touch or rest on the skin of the patient's face. It securely attaches to the 
outer part of the arthroscope, indicating the insertion point and guiding the cannula at the 
correct angle. Following successful testing on anatomical models, where it demonstrated 
exceptional accuracy, we aim to evaluate its clinical eﬀectiveness in up to 10 patients to 
draw conclusive ﬁndings. 
 
 
Description of the device: 
The guide device consists of two arms of equal length, each being a double parallelogram. A 
connector holds both arms and permits movement by changing the angle between them 
(Fig 1). One arm is intended to hold the arthroscope while the other arm holds the working 
cannula. Owing to the double parallelogram design, after attaching the instruments 
(arthroscope and working cannula) their ends have to meet, and this is true in the whole 
range of motion of the guide device, so that while changing the angle between the two arms 
of the LOPO, the meeting point between the tip of the arthroscope and the tip of the 
working cannula keep their intimate relation (Fig 1 and 2). 
During surgery, after the arthroscope is introduced into the joint cavity, the guide device is 
mounted on the base of the arthroscope via one arm. The other arm receives the working 
cannula, and owing to the double parallelogram design, it directs it to the ideal puncture site 
and insertion vector and depth into the joint cavity, where it has to meet the tip of the 
arthroscope (Fig 3). This results in immediate visualization of the working cannula by the 
arthroscope and maintains optimal spatial positions between the two portals. The connector 
between the two arms of the device enables changing the angle between them while 
maintaining the relative position of the tip of the cannula to the tip of the arthroscope. 
The connector can also be locked thus ﬁxating the angle between the two arms. 
Throughout the range of motion, the working cannula will always reaches the tip of the 
arthroscope. The LOPO does not enter the body because only the ends of the arthroscope 
and the working cannula are inside the body while the device is externally positioned and 
held by the surgeon. 
The LOPO is designed to address the challenges of determining the insertion point on the 
skin for the working cannula, the correct angle for insertion into the joint cavity, and the 
proper penetration depth. In addition, it maintains the optimal spatial orientation between 
the arthroscope and cannula throughout surgery. Its main goal is to ensure that the working 
cannula is inserted accurately and becoming immediately visible via the arthroscope on the 
ﬁrst attempt, and them maintaining the correct spatial relationship between the arthroscope 
and the working cannula throughout surgery. 
 
Figure 1: the yellow lines represent the path of insertion of the arthroscope and working 
cannula. The red asterisk represents the meeting point of both. Through all range of motion 

of the LOPO device (changing the angle between its’ two arms), the ends of both 
instruments maintain their relations to one another.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Figure 2: the LOPO with the arthroscope and working cannula mounted on it. 
 
 
 
Figure 3: illustration demonstrating the relations between the TMJ, arthroscope (blue), 
working cannula (red), and LOPO guide device (grey). 
 
 
 
Technical details:  
- Manufacturer: Pollak Steinberg Ltd. 
- Model: TMJ-DEVICE-100 
- Materials: Stainless steel 303, resistant to autoclave sterilization, multi-use 
- The device can be attached and detached from the arthroscope and working cannula at any 
stage of the operation. 
 
 
Summary of existing preclinical knowledge regarding the device: 
The device was tested on anatomical models between August 2017 and February 2018, and 
it was found to meet the objectives exceptionally well. Multiple doctors in the department, 

including interns with no prior arthroscopy experience, conducted several attempts on the 
models. In all cases, the working cannula was guided by the LOPO device and inserted with 
great precision to the end of the arthroscope, where it was immediately visible by it. The 
experiments were conducted in the operating room at Sheba Medical Center using the same 
set of standard arthroscopic tools. 
In this pilot experiment, we will use the same standard set of arthroscopic tools that is 
regularly used at Sheba Medical Center. It is important to note that the LOPO has been 
designed according to the dimensions of the arthroscopic tool set available at Sheba. 
 
 
Goals and Endpoints 
This pilot study aims to recruit up to 10 patients to test the functionality of the LOPO in 
clinical conditions. The outcome of the study are: 
1. The number of attempts required by the surgeon to correctly place the instruments in 
relation to each other within the joint cavity. No more than three attempts will be made in a 
single operation. 
2. The time elapsed from the insertion of the working cannula until it is clearly visible by the 
arthroscope (measured in seconds). 
3. The number of cases in which the surgeon fails to correctly insert the working cannula, 
meaning that after three attempts, the cannula is still not properly placed in the joint and 
not visible by the arthroscope. 
4. The improvement of mouth opening after arthroscopy. 
Our hypothesis is that the LOPO will shorten the duration of surgery by helping the surgeon 
insert the working cannula more quickly and easily. It should allow accurate insertion of the 
working cannula on the ﬁrst attempt, reducing scuﬃng of tissues, ﬂuid leakage, swelling, and 
surgical risks. Using the device does not increase the known risks of surgery. 
 
 
The total number of participants and how they will be recruited: 
The experiment will be carried out in the Department of Oral and Maxillofacial Surgery at 
Sheba Tel Hashomer Medical Center. 
Up to 10 participants are needed to demonstrate that the LOPO device eﬀectively positions 
the working cannula regardless of anatomical variation among individuals. 
Candidates for the procedure are patients diagnosed in our department with closed lock, 
Wilkes stage 3, based on anamnesis, clinical examination, and imaging, for whom TMJ 
arthroscopy is the accepted treatment. These patients will receive the standard preoperative 
explanation about the procedure, including its course, expected results, potential risks, the 
necessity for post-operative physical therapy, and the requirement to avoid hard foods for a 
month after arthroscopy. Additionally, they will be informed about our intention to use the 
LOPO device and asked for their consent. Patients who consent to using the LOPO during 
surgery will receive a letter for their family doctor detailing the procedure and the device. 

The patients will be treated using the standard arthroscopic tool set available at Sheba, 
along with the LOPO device we developed. 
Participants will not receive any ﬁnancial compensation or other beneﬁts. It will be 
explained that their participation contributes to scientiﬁc and medical advancements. 
Successful performance of the device in real patients will signiﬁcantly advance the ﬁeld of 
TMJ arthroscopy. 
 
 
Criteria for inclusion, exclusion, and exclusion from the experiment: 
- 
Inclusion criteria:  
o Diagnosis of lock-jaw (Closed lock of the TMJ, Wilkes stages 3) based on 
anamnesis, clinical, and imaging. 
o Have not undergone surgical intervention in the TMJ in the past. 
o Adult patients (over the age of 18), not pregnant, and of sound judgment. 
- 
Exclusion criteria: 
o Patients who are minors, pregnant, or lacking judgment. 
o Previous surgical intervention of the TMJ. 
- 
Criteria for exclusion from the experiment: 
o Patients who will not complete post-operative follow-ups as planned. 
 
 
Details of the research program and clinical follow-up:  
- 
Patients that are referred for TMJ arthroscopy at our department will be asked if they 
agree to participate in the LOPO experiment. Patients will receive standard treatment 
in terms of hospitalization and examinations. 
- 
Follow-up reviews will take place in our clinic. 
- 
The initial follow-up period is six months. 
- 
Patients may be invited for further follow-up visits as a routine practice in our 
department. 
 
 
Schedule and Flow Chart of the Experiment: 
- 
Recruitment of 10 Participants: we estimate that we can recruit 10 participants 
within a year. Notably, our department performs approximately 70 arthroscopic 
surgeries annually (70 patients per year). 
- 
Data Summary: the data summarization process is expected to take less than 6 
months. 
- 
Publication: the results of the experiment will be published in an international 
scientiﬁc journal. 
 
 

Participant Privacy and Conﬁdentiality of Collected Information: 
- 
Patients diagnosed with lock-jaw who need TMJ arthroscopy will be oﬀered the 
option to use the LOPO device during their surgery. They will receive an 
informational letter explaining the procedure and the use of the device. 
- 
Interested patients should consult with their family doctor, presenting the 
explanatory letter for further advice. Regardless of their decision to participate in the 
trial, all patients will receive standard care in our department, including admission, 
hospitalization, discharge, and periodic follow-ups after surgery. 
- 
A database containing the names of the patients (up to 10) and the experiment 
results (studied indices) will be maintained in an Excel sheet on a secure computer 
within the department. 
 
 
Conditions for Halting the Medical Experiment: 
- 
If the LOPO device does not perform as expected, based on its performance with 
anatomical models, its use will be halted immediately, and no further patients will be 
enrolled in the experiment. 
- 
The use of the LOPO will also be immediately discontinued in the event of any known 
or unforeseen complications arising from the operation 
 
 
Reporting Unusual Events: 
- 
The researcher will promptly inform the Chair of the Helsinki Committee of Sheba 
Medical Center about any signiﬁcant unusual events observed during the 
arthroscopy and the use of the LOPO device within one week. Additionally, any 
relevant new information related to these events will be communicated to the 
Helsinki Committee through subsequent follow-up reports. 
 
 
Method of Analyzing and Processing Results: 
- 
The data from the ten patients using the device will be compared with data from 
patients undergoing TMJ arthroscopy without using the LOPO device. The following 
parameters will be evaluated: 
o Time elapsed from insertion of the working cannula until it is clearly visible 
through the arthroscope. 
o Number of attempts made by the surgeon to correctly position the 
instruments within the joint cavity (limited to three attempts per surgery, 
following standard practice). 
o Number of cases where the surgeon failed to correctly insert the working 
cannula, despite three attempts, as observed through the arthroscope. 

o Measurements of maximal mouth opening of the patients undergoing the 
procedure, before as compared to after arthroscopy.  
 
 
 
Contact: 
Dr. waseem Abboud 
Telepohone: +972-52-6657060 
Email: waseem.abboud@gmail.com, waseem.abboud@sheba.health.gov.il  
Chaim Bar Lev 9, Apartment 26, Ramat-Gan 5265370