case_images: PMC7195939_01
case_images: The CCD angle was 145 , the LCEA was 42  and asphericity was present on X-ray image.
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case_images: The caput-collum-diaphyseal (CCD) angle was 145  and the lateral center-edge angle (LCEA) was 42  (Fig. 1).
case_images: The 3D CT view of femur head-neck area after arthroscopic surgery.
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case_images: Arthroscopic resection of the cam deformity was performed and the 3D computed tomogram (3D CT) revealed decompression of the head-neck area post-operatively (Fig. 2).
case_images: The patient continued to walk with toes out and thigh abducted despite arthroscopic surgery.
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case_images: Nonetheless, the patient complained of persistent pain, and continued to manifest out-toeing gait with thigh abduction (Fig. 3).
case_images: (A) The orthogonal 3D CT view of femur neck and trochanter showed the external torsional deformity. (B) Right femur neck axis. (C) Right distal femur trans-epicondylar axis. (D) The right distal femoral transepicondylar axis was externally rotated by 10  compared with the right femur neck axis, which meant femoral retroversion.
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case_images: The distal femoral transepicondylar axis was externally rotated compared with the right femoral neck axis (10 ) and there was external torsion at and above lesser trochanter in orthogonal 3D CT view (Fig. 4A-D).
case_images: (A) Two parallel K-wires inserted above and below the osteotomy site were used to measure varization and derotation after osteotomy. (B) The paths of two neck screws were guided by preemptive insertion of K-wires in lateral as well as anteroposterior fluoroscopic film.
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case_images: The degree of varization was calibrated in the pre-operative roentgenogram and that of derotation was measured by two parallel K-wires in the saw bone model (Fig. 5A). The two K-wires for neck screws on the lateral film were inserted in parallel, and linearly in the anteroposterior film under fluoroscopic guidance (Fig. 5B). The entry and direction of two parallel neck screws were pre-drilled in parallelly on the lateral film and linearly in the anteroposterior film calibrated pre-operatively (Fig. 5B).
case_images: (A) The extra-articular impingement was confirmed by viewing the contact between the inferior intertrochanteric line area and the iliopectineal area with internal rotation in both 90 and 20  flex. (B) The previous femoroplasty area was identified by surgical hip dislocation.
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case_images: The extra-articular impingement was confirmed by viewing the contact between anteromedial cortex of the inferior portion along the intertrochanteric line and the anterior acetabular rim along with iliopectineal eminence area within the physiologic ROM (Fig. 6A). Previous femoroplasty area was identified (Fig. 6B).
case_images: (A) Acetabular chondral lesion at the chondrolabral junction of 12 o'clock position. (B) A small rim defect and labral rent at the chondrolabral junction of 2 o'clock position.
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case_images: Acetabular chondral lesion was visible at the chondrolabral junction of 12 o'clock position and the labrum was not torn (Fig. 7A). A small rim defect and rent at chondrolabral junction were noticed at the 2 o'clock position (Fig. 7B).
case_images: (A) Acetabular labral takedown, rim resection and labral refixation with two anchors. (B) In vivo lateral opening and derotation by divergence and rotation of the K-wires and subsequent fixation of neck and plate screw. (C) After the final fixation of the calcar neck and the other plate screws, the osteotomized digastric greater trochanter was relocated and fixed with three large screws.
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case_images: Acetabular labral takedown, bone trimming, and labral refixation were performed at 12 o'clock positions, measuring ~1 inch in length (Fig. 8A). Simultaneous varization and derotation were performed gently as much as measured pre-operatively by rotation and divergence of the distal K-wire with the distal thigh adducted slightly and the leg rotated internally by the assistant (Fig. 8B). The gluteus-greater trochanter-vastus lateralis sleeve was relocated and the osteotomized greater trochanter was fixed with three large cortical screws (Fig. 8C). 
case_images: The CCD angle was changed to 131  and the LCEA decreased to 28 .
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case_images: The CCD angle was changed to 131 , the medial offset was increased and the LCEA decreased from 42 to 28  (Fig. 9).
case_images: The post-operative right femur neck anteversion was 2.6 .
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case_images: The femoral neck axis was anterverted compared with the distal femoral epicondylar axis in CT (2.6  anteversion; Fig. 10).
case_images: Solid bony union on 2-year post-operative X-ray films.
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case_images: Two years post-operatively, a solid bone union of osteotomy site was observed, and the fixative for osteotomy was removed (Fig. 11).