Frequency of Restoration of Mechanical Axis in Patients Undergoing Primary Total Knee Arthroplasty by Using Mal-alignment Test in Pre- and Post-Operative Scanogram

Abstract

Objective:
 To assess the frequency of restoration of mechanical axis deviation (MAD) in patients undergoing primary total knee arthroplasty (TKA) using malalignment test on pre- and postoperative weight-bearing scanograms.

Methods:
 A prospective cohort study was conducted from August 2018 to August 2019 at a tertiary care hospital. A total of 30 patients aged 40–100 years with advanced osteoarthritis were included. Pre- and postoperative MAD was measured on full-length weight-bearing scanograms. Patients with revision TKA, rheumatoid arthritis, tumor surgeries, or failed primary TKAs were excluded. Mechanical axis deviation was assessed on the third postoperative day and correlated with functional outcome.

Results:
 Among 30 patients, 46.7% were male and 53.3% female, with a mean age of 58.3 ± 9.8 years. The mean preoperative MAD was 26.88 ± 43.26 mm (80% medial, 20% lateral), and postoperative MAD was significantly reduced to 10.56 ± 7.31 mm (100% medial). Restoration of neutral alignment was achieved in 80% of cases. No statistically significant association was found between restoration of MAD and variables such as age, gender, BMI, comorbidities, or side of surgery (p > 0.05).

Conclusion:
 Primary total knee arthroplasty effectively restored the mechanical axis in 80% of patients. Malalignment remains a critical factor for long-term prosthesis survival and functional outcomes. Postoperative scanogram is a reliable tool for evaluating limb alignment, although its immediate use may not reflect physiological loading. Further studies with larger cohorts and long-term follow-up are recommended.