Francisco Angulo Parker, MD PGY3 UKY PM&R Knee hyperextension after hamstring lengthening in cerebral palsy: Incidence, predictive factors and cost in gait efficiency Francisco Angulo Parker, MD PGY3 UKY PM&R

Cerebral Palsy Cerebral palsy (CP) is the leading cause of childhood disability affecting function & development Overall estimated prevalence of CP is 2-2.5 cases per 1000 live births Criteria for CP: Static Brain lesion Neuro-motor control deficit that affects movement or posture Immature brain

Hamstring Lengthening Goal of surgery in ambulatory patients To improve gait efficiency To improve knee flexion deformity To increase knee extension at the end of swing phase and at heel strike Crouching gait

Descriptive statistics No. (%) Gender Male 97 (66%) Female 50 (34%) GMFCS 1 26 (17.7%) GMFCS 2 48 (32.7%) GMFCS 3 73 (49.7%) Mean(std) Age at surgery 12. 1 (3.2) years Duration b/w surgery & post op gait analysis 1.4 (1.1) years

BACKGROUND KINEMATICS IN GAIT EFFICIENCY POOR DATA PREDICTING KNEE HYPEREXTENSION REGARDED AS POOR OUTCOME AVAILABILITY OF DATABASE SERIES OF STUDIES FROM SAME DATABASE

Objectives Incidence Can we predict it? What are the predictive variables? Cost of knee hyperextension in gait efficiency

Methodology Retrospective, case control study. Regression analysis for predicting variables.

population

Population Diagnosis Frequency CP hemiplegia 2 CP diplegia 142 HSP 5 parplegia 3 fredrichs ataxia 1 Total 153

Population Characteristics Gender Previous Hamstring 93 males 49 female Previous Hamstring No: 110 Yes: 32

Population Procedures 33 only HS lengthening 34 TAL and HS lengthening 30 Rectus transfer and HS lengthening 27 TAL, HS lengthening and rectus transfer

Incidence of knee hyperextension 284 knees (142 patients) Hyperextension considered 0 deg and above pass full extension 11.5% of the knees showed hyperextension post HS lengthening

Variable analysis for prediction Preop GMFCSLevel Age at surgery Other simultaneous surgery (yes/no) Simultaneous RECTUS (yes/no) Preop L Popliteal angle Preop L Knee extension Preop L Knee flexor tone Preop L hip extensor Preop L knee Flexor Preop L knee Extensor PRE L 0 = knee flexion at initial contact preop PRE L 30 = knee flexion at mid-stance preop Change HT change in height from preop to post op Change WT change in weight from preop to post op

Variables in the Equation   B S.E. Wald df Sig. Exp(B) Step 1a preGMFCSLevel 1.027 .424 5.854 1 .016 2.793 age_atsurgery -.131 .087 2.262 .133 .877 othersimultaneoussurgery -.253 .199 1.620 .203 .776 simultaneous_RECTUS .316 .614 .266 .606 1.372 Preop__Popliteal_angle .057 .027 4.533 .033 1.059 Preop__Knee_extension .013 .039 .114 .736 1.013 Pre_op__Knee_flexor_tone .382 .273 1.966 .161 1.466 Pre_op__hip_extesor_control .310 .196 2.516 .113 1.364 Pre_op__knee_Flexor_control .024 .241 .010 .921 1.024 Pre_op__knee_Extensor_control -.476 .345 1.906 .167 .622 PRE__0 -.049 3.225 .073 .953 PRE__30 -.046 .023 4.070 .044 .955 changeHT .009 .040 .053 .818 1.009 changeWT .034 .037 .861 .354 1.035 timetofollowup -.060 .164 .134 .715 .942 Constant -1.339 3.043 .194 .660 .262

Variable analysis for prediction Statistically significant P=<0.05 Pre GMFCS Pre op angle Pre operative knee flexion at midstance Clinically significant Significant results only present in Pre operative knee flexion at midstance

Gait Stance phase (1) Swing phase (1) Limb of interest in contact with ground 60% of gait when walking Heel strike loading response - foot plantar flexes to ground midstance - tibia shifts forward over plantigrade foot terminal stance – heel rise preswing Swing phase (1) Limb of interest in air 40% of gait when walking Initial swing – begins with toe off, limb moves forward Midswing – when limb passes grounded limb Terminal swing – also known as deceleration, slow down towards heel strike Both feet are on ground during initial contact and during the end of swing phase at terminal stance as the body weight is shifted onto the other limb and the heel rises from the floor in preparation for push off **tight hamstrings effect all phases of gait

Results Pre-operative knee flexion at midstance Not hyperextended. Mean: 35.451 SD: 16.2 Hyperextended Mean: 23.9 SD: 17.59

Gait efficiency Measured by Oxygen consumption pre and post bilateral hamstring lengthening Same database  Only 78 subjects with preop and post op oxygen consumption data

Gait efficiency Oxygen consumption Amount of oxygen consumed per kg of body weight over time (mL/kg-min) Total power required to keep the body in motion Related to the level of effort it takes to walk Does not take walking velocity into account

Results Group Statistics post_Hyper_R N Mean Std. Deviation   post_Hyper_R N Mean Std. Deviation Std. Error Mean PreO2ConsumptionExercise not hyper 69 18.938 3.8794 .4670 hyper 9 19.422 3.2468 1.0823 Pre02Cost .6293 .30379 .03657 .7344 .24895 .08298 PostO2ConsumptionExercise 17.233 3.4472 .4150 17.722 4.1176 1.3725 Post02Cost .5419 .19304 .02324 .6233 .20062 .06687 Change_O2_cost -.0874 .21070 .02536 -.1111 .12830 .04277 Change_O2_Consum -1.7043 3.97937 .47906 -1.7000 2.73359 .91120

Conclusion Incidence of knee hyperextension after hamstring lengthening in our population is 11.5% Significant variable: knee flexion at midstance Statistical and clinical significance at a mean of 23.9 degrees when compared to a mean of 35.4 degrees No significant change in Oxygen consumption in hyperextended vs non-hyperextended knees

discussion Clinical follow up at 1.5 years after surgery. Long term observance should be considered Insufficient knee flexion at midstance would bring up the incidence to approximately 25% What is the efficiency cost in chronic knee hyperextension? Overall, the prediction of hyperextension continues to be difficult

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