Objective To compare the mid-term clinical efficacy and the impact on foot pressure distribution of two techniques for deepening the bony fibular groove-sub-cortical drilling and pressurization technique and bone flap flipping and window opening technique-in the treatment of chronic fibular tendon dissociation （CPTS）， and to provide a biomechanical basis for clinical surgical selection. Methods A retrospective cohort study design was employed. A total of 52 patients with CPTS who underwent surgical treatment at Hongdu Central Hospital in Nanchang City between January 2022 and December 2024 were included in the study. Based on the surgical methods， the patients were divided into the modified group （sub-cortical drilling and pressurization technique combined with fibular upper support band reconstruction， n = 26） and the conventional group （bone flap flipping and window opening technique combined with fibular upper support band reconstruction， n = 26）. The average postoperative follow-up period was 18.4 months. The American Orthopedic Foot and Ankle Society （AOFAS） ankle-hindfoot scores and pain visual analogue scale （VAS） scores of the two groups at 12 months after surgery were compared. Additionally， the peak pressure （PP）， pressure-time integral （PTI）， and symmetry index （SI） of each area of both feet during the gait cycle were analyzed using the Sennoscan 120 foot pressure force plate system. Results Twelve months after surgery， the AOFAS and VAS scores of both groups were significantly improved compared with those before surgery （P < 0.05）. However， there was no statistically significant difference between the groups （P > 0.05）. Foot pressure analysis indicated that， during the gait progression phase， the SI-PP of the affected side in the fourth and fifth metatarsal regions of the modified group was significantly better than that of the conventional group （P < 0.05）. The SI-PTI of the affected side in the hindfoot region of the conventional group was significantly higher than that of the modified group （P < 0.05）， which suggests the presence of compensatory gait with prolonged load time on the hindfoot and insufficient external column thrust. The coronal plane swing amplitude of the pressure center （CoP） of the modified group was closer to that of the healthy side. Conclusions The two surgical methods exhibit comparable efficacy in relieving pain and enhancing ankle joint function. Nevertheless， the sub-cortical drilling and pressurization technique can more effectively restore the load characteristics of the lateral column of the foot during the gait progression phase and mitigate compensatory gait， thereby presenting biomechanical advantages in facilitating the recovery of natural gait.