Bony pelvis anomalies in bladder exstrophy have prompted a great deal of papers addressing biomechanical analysis and kinematic of walking joints. However, a direct evaluation of forces applied to each joint (moments and powers) has never been performed nor has it been correlated to osteotomy
Methods Exstrophy patients in a collaborative age were asked to participate in gait studies using a Vicon MX, a 3-dimensional motion analysis system with 8 cameras – kinematics - and two force plates (AMTI, USA) - kinetics. Kinematics analysis included pelvic tilt and hip, knee and ankle flexion-extension angles. Kinetics analysis consisted in the evaluation of hip, knee and ankle moments and powers. Normal healthy peers acted as controls. Correlations were sought between exstrophy patients and controls and between patients non osteotomized (Group 1) and those with osteotomy (Group 2) In particular, were analyzed: i)knee angle at contact with floor, during load response , in late stance and during swing ;( ii) pelvic tilt angle at contact with floor and the absolute maximum of posterior tilt ; (iii) maximum knee flexor moment during early stance (K-fm); iv) maximum knee extensor moment during late stance (K-em); v ) maximum knee power generation during late stance (k-p).Anova statistical test and Bonferroni post-hoc test was performed with Spss software (p<0.05).
Results Nineteen patients were recruited, ranging in age from 5 to 22 years. Two patients underwent complete primary repair and 17 staged repair Group 1 consisted of 13 exstrophy patients without osteotomy and Group 2 consisted of 6 osteotomized patients , 4 anteriorly and 2 posteriorly. Mean value of the kinematic and kinetic indexes analyzed showed statistically significant differences for all values, between patients and controls, with the only exception for the ankle plantar flexion. . Maximum flexor moment values of the knee increased in patients respect to control group (K-fm 0.41±0.17 Nmkg / 0.25±0.19 Nmkg for patients and controls respectively), while decreased both the maximum extensor moment (K-em -0.20±0.35 Nmkg / -0.43±0.20 Nmkg for patients and controls respectively) and maximum power generation (K-p 0.15±0.19 Wkg / 0.85±0.50 Wkg for patients and controls respectively). The comparison between Group1, Group2 and controls revealed that patient that received osteotomy (Group2) showed the greatest differences with controls
Conclusions Normal walking in exstrophy patients can be achieved at the prize of retroversion of the whole body center of mass which puts knee joint in a state of permanent flexion. This, in turn, leads to increased flexor moment and to decreased extensory moment and power generation at the knee joint. Such modifications are more evident in patients receiving osteotomy. . Impaired kinetics at the knee joint should be disclosed early thereby prompting rehabilitative treatment with the aim to prevent joint and tendon diseases.