In-person Randomized Control Trial of the Incidence of Postoperative Hypoesthesia Among Bilateral Sagittal Split Osteotomy Patients Treated With Ultrasonic vs. Reciprocating Saw Instrumentation
Phase: NA
Conditions: Surgical Complication, Paresthesia, Fracture, Nerve Injury, Nerve Entrapments, Mandibular Nerve Injuries, Mandibular Hypoplasia, Mandibular Retrognathism, Mandibular Hyperplasia, Mandibular Prognathism
Sponsor: University of California, San Francisco

Protocol: In-person randomized control trial of the incidence of 
postoperative hypoesthesia among bilateral sagittal split osteotomy 
patients treated with ultrasonic vs. reciprocating saw instrumentation.
NCT05205616
May 30th, 2025
Table of Contents
RESEARCH STRATEGY OVERVIEW........................................................................2
STUDY PROCEDURES..........................................................................................3
TREATMENT:...........................................................................................................................3
DATA COLLECTION:..................................................................................................................3
STATISTICS........................................................................................................4
OUTCOME OPERATIONALIZATION:.................................................................................................4
PRIMARY ANALYSIS:..................................................................................................................4
SECONDARY ANALYSES:.............................................................................................................4
QUALITY CONTROL / INTERIM ANALYSIS..............................................................5
HUMAN SUBJECTS..............................................................................................6

Research Strategy Overview
The aim of this prospective study is to analyze the postoperative paresthesias experienced in 
patients who undergo bilateral sagittal split osteotomies (BSSO) using an ultrasonic saw, versus 
a reciprocating saw. A matched-pair (with-in person) RCT design will be used, wherein each 
mandibular side (right versus left) in each patient will be randomized to be treated with either 
reciprocating saw (RemB) or Sonopet ultrasonic device (Sonopet IQ Hp). Patients included in 
the study are ages 15-45 scheduled to undergo BSSO surgery at the University of California, San
Francisco. The orthognathic surgeries will be performed at UCSF Parnassus Moffitt-Long 
Hospital and UCSF Medical Center at Mission Bay, Benioff Children's Hospital. Follow-up 
appointments will be conducted at 513 Parnassus Ave, S738, Oral and Maxillofacial Surgery 
(OMFS) Faculty Practice Clinic.
One side of the patient’s mandible will be instrumented with either the Stryker Sonopet 
ultrasonic saw or traditional reciprocating saw, while the other side will receive the remaining 
intervention (determined via randomization on the day of surgery). Patient paresthesias will then 
be analyzed on each side for 3 months postoperatively (at postoperative days: 1, 7, 14, 28, and 
84). Sensory examinations will be carried out by blinded examiners using von Frey hairs and 
two-point discrimination testing. Patients will also subjectively rate their sensation on each side. 
The results will then be analyzed to determine if patient paresthesias, including the severity and 
duration, differed depending on which instrument was used, the ultrasonic or reciprocating saw.

Study procedures 
Treatment: 
On the day of surgery, a randomization process (using randomization blocks of 8, using 
sealedenvelope.com with a predetermined seed) will determine which mandibular side receives 
which intervention (Sonopet ultrasonic saw or reciprocating saw), as well as which side is 
operated on by Dr. Soheil Saghezchi, DDS, MD, with the remaining side being operated on by 
the senior resident involved with the case. Given the supervision of the attending surgeon, the 
senior resident has the appropriate skills to perform the equivalent procedure on the contralateral 
side. Given that the two osteotomy instruments are physically different, the provider delivering 
the treatment cannot be blinded. It will be documented in the operative report if the patient 
received any other interventions, such as LeFort I osteotomy or genioplasty, and if any direct 
manipulation of the inferior alveolar nerve occurred (for instance if the nerve was gently freed 
from the proximal mandibular segment, if the nerve was not directly visualized, etc.). 
 
Data Collection: 
Patient sensation in the V3 distribution will be analyzed on each side at one week preoperatively 
(baseline) and at five different postoperative timepoints: 1 day, 1 week, 2 weeks, 4 weeks, and 3 
months. Patients are already and consistently under OMFS care at these timepoints (whether as 
an inpatient or at a clinic visit) thereby collecting this data will be at minimal inconvenience to 
the patient. Sensation will be evaluated with patients completing a Medical Research Council 
Scale questionnaire, along with residents testing sensation with von Frey hairs (at a region 1 cm 
below corresponding lower lip) and two-point discrimination tests with calipers (on 
corresponding lower lip). 
The patient, as well as the resident evaluating the patient, will be blinded to which side received 
which intervention. Patient's medical records will not indicate which side was operated on with 
which osteotomy instrument, and the evaluating resident will be a different provider than the 
senior resident who delivered the treatment. To assess efficacy of observer blinding, the 
observing resident will guess at the time of sensory measurement which side of the patient was 
operated on using the ultrasonic saw. Also to verify measurement accuracy, a second observer 
(Dr. Saghezchi) will reexamine the patient and verify the von Frey hair and two point 
discrimination findings that the resident collected at each visit. 
Patient’s age, gender, race/ethnicity, and intraoperative complications relating to osteotomy will 
also be recorded. Also, medication history (steroids, analgesics, psychiatric/neuroepileptic, etc...)
will be recorded at each visit.

Statistics 
Outcome operationalization: 
For more practical clinical a\ined as a lower lip two point discrimination test >15mm, or patient’s
inability to sense third hair or thicker in the von Frey hair series. 
Primary analysis: 
Effect measure (Odds Ratio) of the intervention on neurosensory deficit at 3 months will be 
calculated in both an Intention to Treat (ITT) and Per Protocol (PP) analysis using conditional 
logistic regression models (an extension of McNemar’s test). If the treatment and intervention 
arms are perfectly balanced and matched, age and gender will not be used as covariates. 
However, effect measure modification (interaction) of these and other covariates (e.g. gender, 
age, specific medications) will be explored. Likely, very few patients will undergo unexpected 
intraoperative manipulation of the inferior alveolar nerve. These patients will be omitted from 
analysis, unless they represent >10% of the sample size, in which case, we will include the 
patients and adjust for them as a covariate in the conditional logistic regression.  
Secondary analyses: 
A subgroup time-to-recovery analysis will also be performed among those patients exhibiting 
neurosensory deficit in post-operative day 1. This analysis will be a survival analysis with 
follow-up period from day 1 to 3 months, with “failure event” being recovery of neurosensory 
deficit. If too few recoveries occur prior to 3 month visit, we will again use conditional logistic 
regression test instead. [Update: This analyses was not ultimately done due to small sample size 
at completion of study.]

Quality Control / Interim Analysis
For the first six months, all investigators and an on-field data collecting resident will meet 
monthly to discuss and assess challenges, progress, harms, and benefit. Any initial reports of 
deviation/adverse event/breaks in confidentiality will be reviewed immediately by the principal 
investigator and out-report in accordance with the UCSF post-approval reporting requirements. 
Thereafter, the research team will reconvene at a minimum of every three months. An unblinded 
interim analysis of efficacy and effect measure will be performed by the analytic investigator at 1
year (or at 25 patients, whichever is sooner) to assess for termination of trial due to unexpectedly
strong benefit or harm.

Human Subjects
Patients will be identified from the UCSF Moffitt-Long and Mission Bay Benioff Children's 
hospital operating room schedules for Dr. Saghezchi, and those scheduled for BSSO surgery who
meet the inclusion criteria will be approached for enrollment in the study. All patients scheduled 
for BSSO surgery with Dr. Saghezchi will be approached for enrollment in the study. Exclusion 
criteria will be an age of over 45, and any preexisting mandibular sensory derangements. This 
study will aim to include 50 patient participants.
At each patient’s presurgical clinic appointment, which occurs one week before their scheduled 
surgery date, they will be approached for enrollment by a resident. The resident will explain the 
study and emphasize that whether they decide to enroll or not will not affect their scheduled 
surgery date. It will be explained that on the day of surgery, randomization will decide which 
mandibular side will be instrumented with the Sonopet ultrasonic saw, with the remaining side 
receiving treatment with the traditional reciprocating saw. Both of these methods are an accepted
and standard level of care for BSSO patients, commonly used in academic institutions across the 
country. We will then analyze their V3 paresthesias on each side at various timepoints 
postoperatively. Dr. Saghezchi will see the patient next and will further answer any questions 
they have about the study. If the patient, or their legal guardian if they are under the age of 18, 
agree to be involved in the study they will then sign a paper consent form explicitly documenting
this. Less than one hour- roughly 10 additional minutes will be added to each follow up 
appointment (5 in total) time to thoroughly assess their sensory function on each mandibular 
side.
Data will be stored immediately on collection using the secure and HIPAA-compliant online web
application, REDCap. Sepehr Hashemi will serve as data manager, programmer, analyst, and 
quality control coordinator. All patient records will be accessed from UCSF campus computers, 
therefore no PHI will be saved on personal computers or stored for later use. Any identifiable 
data collected for recruitment purposes (i.e. during patient approach and while gathering 
informed consent) will be discarded via shredder machine the same day should the patient not be 
interested in participating in the study. Only necessary information for the study will be kept 
regarding patients who do choose to participate in the study.