Medial closing wedge distal femoral varus osteotomy alters the stress distribution pattern of the patellofemoral joint: An evaluation using computed tomography osteoabsorptiometry

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Abstract Purpose This study aimed to (1) assess changes in subchondral bone density distribution across patellofemoral (PF) joint before and after medial closing wedge‐distal femoral varus osteotomy (MCW‐DFVO) and (2) determine correlation between PF alignment and changes in bone density distribution. Methods This retrospective study enroled patients who underwent MCW‐DFVO for symptomatic isolated lateral compartment osteoarthritis (OA), spontaneous osteonecrosis of the knee and lateral femoral condyle cartilage injury with valgus alignment from 2016 to 2022. Clinical and radiological assessments were conducted preoperatively and at the final follow‐up. The final follow‐up referred to the last documented visit at which outcome measures were available. The radiological quadriceps angle (rQ angle) was measured using computed tomography (CT). The distribution of subchondral bone density on trochlear and patella was examined using CT osteoabsorptiometry. The lateral ratio was calculated as the proportion of high‐density areas (HDAs) in the lateral compartments relative to the total HDAs across compartments of trochlea and patella. The paired Student's t test and Pearson's correlation analysis were used to test for significance ( p = 0.05). Results Seventeen knees (17 patients; mean age, 48 years) were included. Following MCW‐DFVO, the mean postoperative Lysholm score significantly improved at the final follow‐up (mean, 29.2 months; range, 14–65 months). The mean lateral ratio of the trochlea and patella notably declined from 69% to 50% and 69% to 56%, respectively ( p = 0.004 and p = 0.041). Changes in trochlear lateral ratio were significantly correlated with changes in the hip–knee–ankle angle, mechanical axis, rQ angle and lateral shift ratio ( p = 0.027, p = 0.031, p = 0.024 and p = 0.008, respectively). Conclusion MCW‐DFVO induced a redistribution of HDA from lateral to medial PF articular surface. Moreover, degree of PF alignment correction post‐MCW‐DFVO was linked to shifts in HDA distribution. MCW‐DFVO alters PF joint stress distribution by reducing lateral compartment loading, supporting its use in valgus knees with PF mal‐tracking or overload. Level of Evidence Level IV, case series.

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