[Assessing the Correlation between the Radiological, Macroscopic and Histological Examination of Degenerative Changes of Articular Surfaces in Knee Osteoarthritis with Varus Deformity].

Purpose of the study: Our study aims to compare the results of preoperative radiography and intraoperative visual assessment of the cartilage with histological assessment of joint surfaces of the medial and lateral compartments resected in patients during the total knee replacement.

Material and methods: The cohort included 20 patients (9 men and 11 women) with the mean age of 66.6 (±7.0) years who met the inclusion criteria of the study. Degenerative changes of the knee joint seen on a preoperative weight-bearing anteroposterior X-ray were evaluated according to the Kellgren-Lawrence grading system separately for the medial and lateral compartment. Based on the visual appearance, the condition of articular surfaces was assessed using the International Cartilage Repair Society Score (ICRS Grade). The histological assessment of degenerative changes was conducted by a pathologist with the use of the Osteoarthritis Research Society International Osteoarthritis Cartilage Histopathology Assessment System based on six grades of articular cartilage degeneration.

Results: The mean degree of degenerative changes based on the radiological classification was assessed as 3.5 (±0.6) for the medial compartment and 2.1 (±0.4) for the lateral compartment. The visually assessed chondropathy according to the ICRS Grade was 3.7 (±0.6) for the medial femoral condyle and 1.8 (±1.0) for the lateral femoral condyle. The histological score obtained using the Osteoarthritis Research Society International Osteoarthritis Cartilage Histopathology Assessment was 4.9 (±1.1) for the medial femoral condyle and 2.4 (±0.7) for the lateral femoral condyle. In respect of the medial compartment, there was no statistically significant parametric correlation between the intraoperative visual assessment of the cartilage degeneration and the preoperative radiological grade r = 0.45. The histological assessment showed a statistically significant concordance both with the degree of chondropathy r = 0.76 and the radiological grade r = 0.64. In the lateral compartment, the parametric test showed a statistically significant concordance only between the radiological grade and the histological score r = 0.72. The correlation between the visual assessment of chondropathy and the radiological grade r = 0.27 as well as the histological score r = 0.24 was very low.

Discussion: In our cohort assessing the early degenerative changes of the lateral compartment as well as the more advanced degenerative changes of the medial compartment, the correlation between the intraoperative assessment of cartilage degeneration as a diagnostic method to examine the lateral compartment and the preoperative radiological grade was not confirmed. Our results failed to confirm a better reporting value of the visual cartilage degeneration assessment of the lateral compartment as against the preoperative X-ray. The space width without narrowing on an X-ray has no reporting value for this compartment in case of varus deformity.

Conclusions: The results clearly indicate that the assessment of macroscopic appearance of the cartilage degeneration during arthroscopy does not necessarily guarantee good long-term clinical outcomes after high tibial osteotomy. The respective degrees of cartilage degeneration identified during the intraoperative visual assessment and the radiological grading of osteoarthritic changes did not correlate in either compartment. In the lateral compartment, the initial radiological and histological findings preceded the visually detectable cartilage changes.

Key words: knee, cartilage, osteoarthritis, radiology, histology, arthroscopy, osteotomy.