Research on the Association Between the Inclination of the Proximal Tibiofibular Joint Surface and Medial Compartment Knee Osteoarthritis
Conditions: Osteoarthritis, Knee
Sponsor: 113th Hospital of Chinese People's Liberation Army

 
 
Research on the Association Between the Inclination of the 
Proximal Tibiofibular Joint Surface and Medial Compartment 
Knee Osteoarthritis 
 
 
ClinicalTrials.gov ID: NCT03147495 
2017.2.10 
 
 

Study Protocal 
Study Design and Patient Selection 
This case-control study (Level III Evidence) will be performed in line with the 
principles of the Declaration of Helsinki.  
The study will be performed to compare the inclination angle of the PTFJ 
surface in participants with and without medial compartment knee osteoarthritis. A 
sample size power analysis was conducted before the study, which revealed that a 
minimum of 39 subjects per group was needed to achieve statistical significance with 
two-sided α=0.05 and 1-ß=0.80 and an assumed mean difference between two 
groups=65% of the standard deviation. The participants will be enrolled at the 
outpatient clinic of our hospital. The patients with medial compartment knee 
osteoarthritis will be enrolled at first. The anticipated number of patients is 40, and the 
female-to-male ratio is expected to be 1:1. Then, the participants of the control group 
will be enrolled and matched for sex and age (within 5 years) to the patients. The 
control-to-patient ratio is expected to be 1:1. 
Inclusion criteria for participants of the patient group will be: (1) minimum age 
of 50 years, (2) symptomatic knee osteoarthritis according to the American College of 
Rheumatology criteria for the classification and reporting of osteoarthritis of the knee 
joint, (3) predominance of self-reported pain over the medial aspect of the knee, (4) 
radiographic evidence of medial compartment knee osteoarthritis with an Ahlbäck 
score of grade Ⅰ or greater, and (5) radiographic evidence of lateral compartment 
with Ahlbäck classification grade 0. We will exclude participants with any previous 

surgery, severe trauma, inflammatory joint disease, or tumors in the affected limb. 
Our controls will be participants aged 50 years or older, without knee 
osteoarthritis according to the American College of Rheumatology criteria for the 
classification and reporting of osteoarthritis of the knee joint, and with radiographic 
evidence of the knee with Ahlbäck classification grade 0. Exclusion criteria will be a 
history of previous surgery, severe trauma, inflammatory joint disease, or tumors in 
the affected limb. 
All participants should give signed informed consent before enrolment. 
Radiographic Examination 
Standing anteroposterior knee radiographs and special PTFJ radiographs will be 
taken for the participants in both groups. The standing anteroposterior knee 
radiographs will be obtained with the knee extended. The PTFJ radiographs will be 
acquired with the knee of the participants in approximately 45°-60° of internal 
rotation. In this projection, the PTFJ articulation can be clearly visible. 
Radiographic Evaluations and Measurements 
For the standing anteroposterior knee radiographs, radiographic knee 
osteoarthritis will be evaluated by using the Ahlbäck grading scale, and the 
femorotibial angle (FTA) will be measured. For the PTFJ radiographs, the 
degenerative joint disease of the PTFJ will be staged with the Kellgren-Lawrence 
staging system, and the fibular inclination angle (FIA) and the tibial inclination angle 
(TIA) of the PTFJ surface to the longitudinal axis of both fibula and tibia will be 
measured separately. The horizontal type of PTFJ will be defined as the inclination 

angle ≤ 20°, and the oblique type will be defined as the inclination angle > 20°.  
Radiograph annotations will be deleted. Each participant will be assigned a 
random and unique number, and participants of the two groups will be mixed. All 
radiographic evaluations and measurements will be carried out in a blinded, 
independent, and random fashion by a radiologist, who do not know the study 
hypothesis, with tools of the digitized picture archiving communication system (PACS, 
RADinfo Technologies Co.,Ltd, Hangzhou, China). Additionally, 20 participants per 
group will be randomly selected. The FIA and TIA of the 40participants will be 
measured again after 1 month by the same radiologist and an orthopedic surgeon who 
do not know the study hypothesis. The intraobserver reliability and interobserver 
reliability in the FIA and TIA measurement will be assessed by using an intraclass 
correlation coefficient (ICC). 
 
 
 
Statistical Analysis Plan 
Statistical analysis will be performed with SPSS (v25.0; IBM Corp). P﹤.05 will 
be considered significant. Demographics, laterality of included knees and FTA will be 
compared between the patient and control groups by using two-sample t test or χ2 test. 
Paired-samples t test will be used to compare the difference between the FIA and TIA 
of all participants. 
Any differences of the FIA and TIA between the patient and control groups will 

be assessed with the two-sample t test. Furthermore, the participants of each group 
will be separately grouped into sex subgroups and into two age subgroups. The old 
age subgroup of each group will include approximately 20 participants with earlier 
ages, and the remaining participants with higher ages will form the older age 
subgroups (The number of participants in each subgroup will be as close as possible 
to 20). The two-sample t tests will be repeated for each sex subgroup and age 
subgroup in isolation. The odds ratios (ORs) for risk factors of medial compartment 
knee osteoarthritis will also be calculated by using binary logistic regression analysis. 
The PTFJ types will be compared between the two groups by using the χ2 test. 
The PTFJ osteoarthritis grades will be compared between the two groups by using the 
Mann-Whitney U test.