Periacetabular Osteotomy: Intra-articular Work Department of Orthopaedic surgery, University of Toronto, Toronto, Ontario, Canada, Hip and Pelvis Clinic , Chonbuk University Hospital , Jeonju, Korea . E-mail: hugo999@naver.com

Background Periacetabular Osteotomy - Goal : Improvement of hip biomechanics by reorienting the acetabulum → postpone degenerative progression Desire of improvement Potential for overcorrection

Background Overlooked intra-articular hip inspection Overcoverage of femoral head → iatrogenic FAI Overlooked chondrolabral injury (dysplasia, FAI) Overlooked intra-articular hip inspection (early experience) Complications of PAO Prevalence % Authors Acetabular cartilage delamination 28 of 64 hips 44% CLP Labral injury 22% Siebenrock et al Labral tearing+/-degeneration 63 of 73 hips 86.3% Ross et al Hypertrophied labrum 46 of 73 hips 63% Acetabular retroversion 25 of 95 osteotomies 26% Dora et al

Intra-articular Work Labral pathology The acetabular labrum - a triangular structure with a basilar attachment to the osseous acetabular rim - a capsular insertion along the external surface - a free intra articular apical margin Dysplastic hip pathomorphology FAI-pincer type FAI-cam type Labral tissue hypertrophy with myxoid degeneration and/or detachment from the osseous acetabular rim Undersurface labral tearing without hypertrophy Labral tearing -extends perpendicular to the labral surface Labral tearing- at the transition(fibrous cartiliginous labrum/articular hyaline cartilage) zone perpendicular to the articular surface Transition zone : between fibrocartilaginous labrum and the articular hyaline cartilage Labral injury alone could generate sufficient pain to require intervention The positive outcome- pain relief after debridement and/or fixation of labral tears,

Intra-articular Work Labral pathology Labral repair with suture anchor : TOC for unstable hypertrophied labrum Anterior hip arthrotomy Modified Smith-Petersen approach used for Bernese PAO Indirect head of rectus femoris is tagged and mobilized for improved view Capsular incision along the long axis of the femoral neck → AP direction at the level of acetabular rim Simple debridement Labral repair using suture anchor technique is used for labral detachment at the extra-articular osseous insertion Labral detachment → Preservation of the blood supply

Intra-articular Work Labral pathology

Intra-articular Work Labral pathology Labral takedown and Rim resection Labral refixation with suture anchors fixed to new acetabular rim Correction achieved

Intra-articular Work Chondral pathology Chondral lesion - Location : anterior and superolateral aspect of acetabulum - Size : 171.7 mm2 Chondromalacic, cleavage, or debonding injury

Intra-articular Work Chondral pathology The natural history of these lesion and whether chondral lesions are independent source of pain have not been determined. Nascent chondral lesions identified at the time of PAO represent an opportunity to alter the degenerative cascade.

Intra-articular Work Chondral pathology In contrast with labral pathology, preOP diagnosis of chondral injury has implications for preOP planning - Hip MR Arthrography : mainstay of soft-tissue hip diagnostic imaging (Specificity ↑, Sensitivity ↓)

Intra-articular Work Chondral pathology Inspection : Patient’s specific hip pathophysiology Diagnostic imaging 2. Rim resection Amount of rim resection to properly address the chondral lesion Staged surgical dislocation → PAO Obtain consent for a possible simultaneous PAO

Intra-articular Work Chondral pathology

Femoral head-neck offset More than 90% of patients treated with PAO require some degree of femoral head-neck offset correction → Intraoperative C-arm fluoroscopy (False profile view, Dynamic impingement view) Assess Intended acetabular correction Femoral head-neck offset Potential exacerbation of FAI

Femoral head-neck offset Cam lesion on femoral head-neck junction burr allows adequate restoration of the femoral head-neck offset Adequate offset achieved