Objective A prospective study was conducted to investigate the feasibility and effectiveness of three-dimensional (3D)-printed in vitro guide plates assisted hip arthroscopy in the treatment of Cam-type femoroacetabular impingement (FAI). Methods The clinical data of 25 patients with Cam type FAI who met the selection criteria between December 2016 and September 2022 were collected. There were 13 males and 12 females with an average age of 42 years (range, 19-66 years). The disease duration ranged from 3 to 120 months, with an average of 22.2 months. The preoperative range of internal rotation-external rotation was (28.7±4.50)°, α angle was (69.04±0.99)°, visual analogue scale (VAS) score was 6.5±0.2, and modified Harris hip score (HHS) was 50.5±0.7. All patients were treated with hip arthroscopy assisted by 3D printed in vitro guide plate. The incidence of complications was observed postoperatively, the acetabular coverage and the α angle of the affected hip joint were measured by hip CT before and after operation, and the glenoid labrum injury was observed by MRI. The percentage of overlap between the Cam plasty area and the preoperative simulated grinding area was calculated by three-dimensional CT+reconstruction, and the difference between them was evaluated. The effectiveness was evaluated by VAS score and modified HHS score. ResultsPostoperative dorsalis pedis numbness occurred in 1 case, and the symptoms disappeared after 1 month of conventional drug treatment such as neurotrophy. Two cases of perineal skin injury occurred, and healed after symptomatic treatment. There was no male erectile dysfunction, deep incision infection, pulmonary embolism, or other serious complications occurred. The percentage of overlap between the Cam plasty area and the preoperative simulated grinding area was 81.6%-95.3%, with an average of 89.8%. All 25 patients were followed up 6-12 months, with an average of 8 months. At last follow-up, the range of internal rotation-external rotation was (40.10±2.98)°, the α angle was (43.72±0.84)°, the VAS score was 1.8±0.2, and the modified HHS score was 72.1±1.3, which significantly improved when compared with those before operation (P<0.05). ConclusionThe treatment of Cam-type FAI with 3D printed in vitro guide plates assisted hip arthroscopy is safe and feasible, and can achieve good effectiveness.