e122 2013 ISAKOS ABSTRACTS

repair and fixation techniques and should inform further in-vivo studies of fixation of chondral flaps and of the effec-tiveness of hydrogel scaffolds in the hip joint.

Paper #144: Can Gait Studies be Used to Predict Riskof Hip Osteoarthritis? MARC RAYMOND SAFRAN, MD, USAPRESENTING AUTHOR

JONATHAN RYLANDER, BS, USATHOMAS P. ANDRIACCHI, PHD, USA $ Stanford University,Stanford, CA, USA

SUMMARYThis study provides additional evidence to support the

idea that the reversal gait profile is associated with hiposteoarthritis risk.

ABSTRACT DATAIntroduction: Osteoarthritis (OA) of the hip is a commoncondition, affecting 1 in 4 individuals by the age of 85.Treatment options for addressing hip OA are generallyfocused on symptom management and many cases endwith surgically replacing the joint with mechanicalcomponents. If hip OA could be detected earlier, treat-ment may be more effective in preventing or slowing theprogression of the disease. A reversal gait pattern, definedas a second order change in the slope of the walking hipflexion angle, has been identified in individuals with hipOA at a significantly higher rate than asymptomaticcontrols and has been found to increase in prevalencewith increasing severity of OA. This same reversal patternhas also been identified in patients with femoroacetabularimpingement (FAI), a condition characterized byabnormal bone growth on the femoral head/neck and/oracetabular rim that leads to physical abutment and softtissue damage. Many consider FAI to be a risk factor foridiopathic hip OA. Therefore, other groups thought to beat risk for hip OA should be analyzed for reversal gaitprevalence to better understand its association to OA risk.One of the highest risk factors for hip OA is advanced age.Longitudinal research would be needed to substantiatethe use of this marker as a predictor for hip OA devel-opment, but if the reversal gait prevalence does increasewith age and is found to be significantly greater in anasymptomatic advanced age group, then additionalevidence would exist to suggest a link between thismarker and hip OA risk. And, if this link exists, then thismarker could be a good, clinical marker for assessingfunctional surgical outcome since it is binary, it eitherexists in an individual or it doesn’t, and it is easily tested,requiring only a limited marker set to collect. Therefore,the Purpose of this study was to test the hypothesis thatreversal gait prevalence would be significantly greater inan older asymptomatic group as compared to a youngerasymptomatic group.Methods: In total, 208 subjects (96 males, 112 females)ranging in age from 20-80 participated in this study. Atleast 30 subjects per decade were enrolled. All participantswere self-described “healthy” based on self-reported lack ofback, hip, knee, or ankle pain; they were not specificallyscreened for hip OA or FAI. Each subject signed a Stanford

University Institutional Review Board approved informedconsent form. Sagittal plane hip kinematics were collectedusing a nine-camera opteoelectronic system by Qualisys Incaccording to an approach previously described by Pro-dromos (Prodromos, 1985). Each participant performedthree walking trials at a self-selected normal walking speed.Walking speed as well as the hip flexioneextension profilefor each trial was recorded while the right leg was in stancephase. Each walking trial was analyzed for the presence ofreversals using an automated program written in Matlab.The reversal profile was first described by Hurwitz (Hur-witz, 1997) and was defined as a second order change inthe slope of the hip flexion-extension profile. A subject wasconsidered to have a reversal gait if this profile existed inat least one of the three normal walking trials. Subjectswere classified by age according to decade and thepercentage of patients in each age group with reversals wasplotted. A Fisher’s exact test was used to compare thepercentage of older subjects with reversals (50-80 y.o.) tothe percentage of younger subjects with reversals (20-49y.o.) (alpha¼0.05).Results: When subjects were divided into a younger andolder group, the older group had a significantly higherpercentage of reversals as compared to the younger group(29.2% vs 12.6%, p¼0.004). Additionally, reversal preva-lence was found to increase with age in a similar manner ascompared to the prevalence of new hip OA cases with age.This pattern along with the fact that the peak in reversalprevalence precedes the peak in new hip OA diagnoses bya decade, suggests that the reversal gait could be a markerfor early onset hip OA, although longitudinal data wouldbe needed to substantiate the idea of the reversal gaitmarker being a predictor of hip OA development. The olderasymptomatic group has a higher incidence of reversal gaitas compared to the younger group. Because the oldergroup is known to be at a higher risk for hip OA devel-opment, this result further supports reversal gait as asso-ciated with hip OA risk.Discussion: The reversal gait metric was identified in anadvanced age group of asymptomatic individuals, a groupknown to be at risk for hip OA. Additionally, previousresearch has identified the reversal gait in FAI patients,another group at a higher risk for hip OA development.Therefore, the reversal gait appears to be associated withhip OA risk and should be studied further as a potentialmarker for hip OA development. The reversal gait trendand peak along with the association with the at-risk groupssuggests that the reversal gait could be a metric to use forpredicting hip OA development and for assessing surgicaloutcome, but long-term data would be needed tosubstantiate this speculation. The participants in this studywere asymptomatic for back and lower limb pain; theywere not specifically screened for hip OA or FAI. Therefore,there are likely a number of subjects in this study withearly onset, asymptomatic hip OA, especially in the oldergroup. The results are promising and suggest that reversalgait is associated with hip OA risk. Future studies should beconducted to further understand the cause of the reversalgait and its association with hip OA development overtime.