Abstract
This study aimed to assess the distance and angular location of the common peroneal
nerve (CPN) on axial magnetic resonance imaging (MRI) in the valgus knees and compare
the measurements with those obtained from the control group. We compared the location
of the CPN according to the type of alignment by performing a subgroup analysis. From
January 2009 to December 2019, we identified 41 knees with preoperative MRI in patients
who underwent total knee arthroplasty (TKA) for valgus deformity (valgus group). We
performed one-to-two matched-pair analysis to a cohort of patients who underwent MRI
but were not candidates for TKA (control group), according to sex and age. The valgus
group was classified according to the grading system reported by Ranawat et al, and
the control group was also subdivided according to the hip-knee-ankle (HKA) angle
obtained from lower extremity scanography: neutral (–3 to +3 degrees from the neutral
mechanical axis), valgus (> +3 degrees), and varus alignment (< –3 degrees). Distance
between the CPN and posterolateral cortex of the tibia at the knee joint (distance
J) and tibial cut level (distance C) were measured. Angle of the CPN from the central anteroposterior axis of the tibia
(angle α) was measured. We compared the measurements between the groups. Distance J was significantly closer in the valgus group (p < 0.001), whereas angle α was significantly smaller in the valgus group (p < 0.001). However, no significant differences were found in the subgroup analysis.
Moreover, a significant correlation was found between distance J and the HKA angle (p < 0.001). The location of the CPN in the valgus knees was closer to the posterolateral
cortex of the tibia at the joint level and showed a smaller angle than that in the
other aligned knees. We recommend that lateral soft tissue release for valgus knees
should not be performed at the joint line. The results of this study suggest that
this would be less safe than a release performed at the level of the proximal tibial
bone resection.
Keywords
common peroneal nerve - magnetic resonance image - valgus knee - total knee arthroplasty
- osteoarthritis
