Radiological evaluation and correlation of Posterior tibial slope and Metaphysio-Diaphyseal angle in osteoarthritic patients planned for Total knee arthroplasty

Abstract

Background: Posterior tibial slope (PTS) plays a very important role in kinematics and
biomechanics of the knee joint. The posterior inclination of the tibial plateau relative to the
longitudinal axis of tibia is defined as posterior tibial slope. Metaphysio-diaphyseal angle
(MDA) is the angle between longitudinal axis of tibia and proximal tibia metaphysis. MDA is
a recent radiological concept gaining clinical significance and its role in Total Knee
Arthroplasty (TKA) is under study and research. The study was performed to evaluate and
correlate the PTS and MDA using lateral knee radiograph in osteoarthritic patients planned
for TKA.
Materials and Methods: This prospective study was conducted in the Department of
Orthopaedics, Ruxmaniben Deepchand Gardi Medical College, Ujjain, Madhya Pradesh,
India from August 2020 - July 2021. Permission was obtained from the Institutional Ethical
Committee and departmental scientific committee. A total of 36 cases of knee osteoarthritis
were enrolled in this study. Posterior cruciate ligament substituting TKA was done with the
same jig to achieve different PTS in different patients. MDA, pre-operative PTS, and postoperative PTS were calculated. All the observations and measurements of PTS and MDA
were analyzed using appropriate statistical analysis.
Result: The mean MDA of the study sample was 20.11 degree with standard deviation of
3.23 degree. The mean Pre-operative PTS of the study sample was 13.68 degree with
standard deviation of 4.06 degree. The mean Post-operative PTS was 9.27 degree with
standard deviation of 4.42 degree.
Conclusion: In this study we found that females undergoing total knee replacement have
nearly the same PTS as males. Also, age had no significant correlation with variation in PTS
of the patients. Patients with MDA above 20° tend to have post-operative PTS significantly
higher than the desired values making them vulnerable to complications. Thus, MDA should
be considered during planning of a total knee arthroplasty. Necessary modifications (such as
pre-operative templating, intraoperative jig angle setting and using intramedullary jigs)
should be done in the current protocols to achieve desired PTS in patients having higher
MDA.