The purpose of this study was to determine the effects of botulinum neurotoxin type A (BoNT-A) on vastus lateralis:vastus medialis (VL:VM) muscle balance, patellar tracking, and pain in patients with chronic patellofemoral (PF) pain. We recruited 13 participants (9 females, 4 males) with recalcitrant PF pain who underwent ultrasound-guided BoNT-A injections into the distal third of the VL muscle, followed by a 6-week home exercise program to strengthen their VM muscle. We imaged the participants in a C-arm computed tomography (CT) scanner before and after the intervention. We calculated VL:VM ratios from CT images from a supine, nonweight-bearing condition. We obtained patellar tilt and bisect offset values from CT images from an upright, weight-bearing condition. We recorded functional pain scores before, immediately after, and 2–4 years after the intervention. We classified the participants into normal tracking and maltracking groups based on their patellar tilt and bisect offset values. BoNT-A with home exercise reduced VL:VM ratio (18%; p < 0.001), patellar tilt (19%; p = 0.020), and bisect offset (5%; p = 0.025). Four participants classified as maltrackers before the intervention transitioned to normal tracking after the intervention. Functional pain scores improved immediately after the intervention (13%, p < 0.001) and remained improved at 2-year follow-up (12%, p = 0.011). Statement of Clinical Significance: This study provides new evidence in support of BoNT-A for treatment of PF pain. Classification of patients under weight-bearing conditions may identify individuals who will most benefit from a BoNT-A treatment.

中文翻译：

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A 型肉毒杆菌神经毒素改善股骨肌平衡、髌骨轨迹和慢性髌股疼痛患者的疼痛

本研究的目的是确定 A 型肉毒杆菌神经毒素 (BoNT-A) 对股外侧肌：股内侧肌 (VL:VM) 肌肉平衡、髌骨轨迹和慢性髌股关节 (PF) 疼痛患者疼痛的影响。我们招募了 13 名患有顽固性 PF 疼痛的参与者（9 名女性，4 名男性），他们在超声引导下向 VL 肌肉的远端三分之一处注射 BoNT-A，然后进行为期 6 周的家庭锻炼计划以加强他们的 VM 肌肉。我们在干预前后使用 C 型臂计算机断层扫描 (CT) 扫描仪对参与者进行了成像。我们根据仰卧、非负重条件下的 CT 图像计算了 VL:VM 比率。我们从直立负重条件下的 CT 图像中获得了髌骨倾斜和二等分偏移值。我们在之前、之后立即记录了功能性疼痛评分，干预后 2-4 年。我们根据参与者的髌骨倾斜度和平分偏移值将参与者分为正常跟踪组和跟踪不良组。BoNT-A 与家庭锻炼降低 VL:VM 比率（18%；p  < 0.001）、髌骨倾斜（19%；p  = 0.020）和平分偏移（5%；p  = 0.025）。四名参与者在干预前被归类为不良追踪者，在干预后转变为正常追踪。功能性疼痛评分在干预后立即改善 (13%, p  < 0.001)，并在 2 年随访时保持改善 (12%, p  = 0.011)。临床意义声明：本研究提供了支持 BoNT-A 用于治疗 PF 疼痛的新证据。在负重条件下对患者进行分类可能会识别出最能从 BoNT-A 治疗中获益的个体。