Can the Medial Proximal Tibial Angle (mPTA) be a Reliable Predictor for the Femoral Rotation in Total Knee Arthroplasty for Varus Osteoarthritis? - A Pilot Study. In Conclusion, there is a Strong Correlation Between the Femoral External Rotation and the Proximal Tibia Varus
Venkataramanan Swaminathan1* and Akash Venkataramanan2
1Apollo Speciality Hospitals, Old Mahabalipuram road, Perungudi, Chennai, India
2Intern, Madras Medical College, Park Town, Near Central Station, Poonamallee High Road, Chennai, India
*Corresponding Author: Venkataramanan Swaminathan, Apollo Speciality Hospitals, Old Mahabalipuram road, Perungudi, Chennai, India.
Received: May 30, 2022; Published: June 27, 2022
Background: In this retrospective study the authors determine if there is a correlation between a preoperative x-ray measurement and intra-operative femoral rotation.
Methods: 20 consecutive patients with varus osteoarthritis of the knee underwent total knee arthroplasty using a modified flexion gap technique. The predicted degree (pDER) was calculated by subtracting the medial Proximal Tibial Angle (mPTA) from 90o. The intraoperative degree of external rotation given to the femur was recorded (iDER). The error of deviation (ED) of the tibial cut was calculated by subtracting the postoperative mPTA from 90o. The corrected iDER (ciDER) was calculated as ciDER = iDER + ED. The correlation between pDER and ciDER was statistically analysed.
Results: The pDER correlated significantly with the ciDER with a p value of <0.00001, weighted Kappa value of 0.868 and Pearson`s Coefficient R of 0.88.
Conclusions: A strong correlation exist between the preoperative mPTA and the femoral implant rotation. The level of evidence is III.
What are the new findings?
- This is a case-cohort study (observational retrospective).
- Shows a strong correlation between the tibia varus angle and the degree of femoral rotation.
- Can derive a reasonably accurate estimate from a simple preoperative radiograph.
Keywords: Knee Arthroplasty; Varus Osteoarthritis; Femoral Rotation; Preoperative Radiographic Measurements
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