Sydney Australia SORI Royal North Shore Hospital Australian Orthopaedic Association Annual Scientific Meeting Adelaide 2010 Demographics and Imaging in Acute Primary Lateral Patellar Dislocation: 100 cases Joshi M PT 1 Giuffre B FRACR 2 Coolican MRJ FRACS 1 Milne B FRACS 1 Parker DA FRACS 1 1 Sydney Orthopaedic Research Institute 2 Royal North Shore Hospital

Conflict of Interest There is no conflict of interest in this research project There is no conflict of interest in this research project

Common problem Common problem Historical belief (Cash & Hughston, 1988) Historical belief (Cash & Hughston, 1988) Overweight adolescent females Overweight adolescent females Abnormal bony anatomy Abnormal bony anatomy Traditional diagnosis Traditional diagnosis Clinical exam & plain radiographs Clinical exam & plain radiographs May lead to under-diagnosis + underestimation (Keene, 1989) May lead to under-diagnosis + underestimation (Keene, 1989) Introduction

Things that are unclear Things that are unclear Demographics (Kirsch et al, 1993) Demographics (Kirsch et al, 1993) Inactive overweight female Vs. young active male Inactive overweight female Vs. young active male Detection of loose bodies (Zaidi et al, 2006) Detection of loose bodies (Zaidi et al, 2006) Plain radiographs Vs. MRI Plain radiographs Vs. MRI Extent of bone + soft tissue injury pattern Extent of bone + soft tissue injury pattern Elias et al, cases Elias et al, cases Guerrero et al, cases (primary + recurrent) Guerrero et al, cases (primary + recurrent) Introduction

Study Aims Understand the demographics of this patient population Understand the demographics of this patient population Compare the efficacy of early X-ray Vs. MRI in loose body detection Compare the efficacy of early X-ray Vs. MRI in loose body detection Delineate the underlying bone + soft tissue injury pattern Delineate the underlying bone + soft tissue injury pattern

Methods 100 knees (97 patients) 100 knees (97 patients) Consecutive series Consecutive series Inclusion Criteria Inclusion Criteria Time to injury < 4 weeks Time to injury < 4 weeks Diagnosis of patellar dislocation Diagnosis of patellar dislocation Reduction in ED Reduction in ED Consistent physical findings Consistent physical findings Exclusion Criteria Exclusion Criteria Past history Past history Knee injury > 4 weeks Knee injury > 4 weeks

Methods- Demographics Standardized questionnaire Standardized questionnaire Age Age Gender Gender Mechanism of Injury Mechanism of Injury Sport Sport

Plain radiographs Plain radiographs Injury to X-ray < 4 weeks Injury to X-ray < 4 weeks Frontal, lateral + Merchant Frontal, lateral + Merchant Analysis by knee surgeons Analysis by knee surgeons MRI MRI Injury to MRI < 4 weeks Injury to MRI < 4 weeks 1.5 T magnet 1.5 T magnet Assessment in 3 planes Assessment in 3 planes Fat suppressed fast spin echo Fat suppressed fast spin echo Non fat suppressed fast spin echo Non fat suppressed fast spin echo Single musculoskeletal radiologist Single musculoskeletal radiologist Methods- Imaging

X-ray X-ray Presence/absence of loose bodies Osteochondral injury (Grades I-IV) (Brittberg & Winalski, 2003) Osteochondral injury (Grades I-IV) (Brittberg & Winalski, 2003) Bone contusion (Grades I-III) (Elias et al, 2002) Bone contusion (Grades I-III) (Elias et al, 2002) MPFL injury- none/partial/complete (Elias et al, 2002) MPFL injury- none/partial/complete (Elias et al, 2002) Patellar insertion Mid portion Femoral insertion Methods- Imaging Analysis

Results- Demographics Mean age = 24 yrs (13-64 yrs) Mean age = 24 yrs (13-64 yrs) 70% male 70% male Mechanism of Injury Mechanism of Injury Sport 66% Sport 66% Rugby Rugby Soccer Soccer Netball Netball Falls 17% Falls 17% Other 17% Other 17%

Results- Imaging Plain radiographs = 16% sensitivity compared to MRI Plain radiographs = 16% sensitivity compared to MRI

Results- Bone Injury Osteochondral injury = 95% GradePatella (%)Femur (%) I4774 II92 III175 IV176 GradePatella (%)Femur (%) I6528 II2655 III29 Bone contusion = 99%

Results- MPFL Injury

Discussion- Demographics Historical belief Non-contact Non-contact Adolescent Adolescent Female Female Non-athlete Non-athlete Study observations * Contact sports Contact sports Young adult Young adult Male Male Athlete Athlete * Consistent with recent literature (Atkin et al, 2000)

X-rays not as sensitive for loose bodies X-rays not as sensitive for loose bodies Underestimation of injury Underestimation of injury Delay in surgical intervention Delay in surgical intervention Consistent with past studies (Atkin et al, 2000; Sallay et al, 1996) Consistent with past studies (Atkin et al, 2000; Sallay et al, 1996) Effect of reviewer consistency on sensitivity Effect of reviewer consistency on sensitivity Discussion- Imaging

OC injury + bone contusion OC injury + bone contusion Clinical importance of bone contusion grade Clinical importance of bone contusion grade Overlying cartilage thinning (Faber et al, 1999) Overlying cartilage thinning (Faber et al, 1999) Discussion- Underlying Injury MPFL Injury MPFL Injury Inconsistency in literature Inconsistency in literature Diffuse nature of injury Diffuse nature of injury Implications for surgery Implications for surgery

Conclusions Most common in young male athletes Most common in young male athletes Sampling bias Sampling bias X-rays under-diagnose + underestimate injury X-rays under-diagnose + underestimate injury Early MRI Early MRI More sensitive for loose body detection More sensitive for loose body detection Extent of bone contusion + osteochondral injury Extent of bone contusion + osteochondral injury Diffuse nature of MPFL injury Diffuse nature of MPFL injury

Future Direction Implications of observed MRI changes Implications of observed MRI changes Bone contusion grade Bone contusion grade Natural history of patellar dislocation Natural history of patellar dislocation Return to sport Return to sport Recurrence rate Recurrence rate Surgical intervention Surgical intervention