Calf lengthening may improve knee recurvatum in specific children with spastic diplegic cerebral palsy.

PURPOSE: Knee hyperextension in stance is a difficult condition to treat in children with spastic diplegic cerebral palsy (CP). In children with passive knee hyperextension, the presence of contracture or spasticity of the calf leads to knee hyperextension in stance phase. We hypothesize surgical treatment of the contracture of the calf will lead to less knee hyperextension. METHODS: We performed a retrospective review of children who were evaluated in our movement laboratory over 23 years with a diagnosis of CP Gross Motor Function Classification System I, II or III. We selected children who had passive knee hyperextension on exam and who underwent calf lengthening surgery. Children were divided into two groups: early recurvatum (ER) (n = 20) and late recurvatum (LR) (n = 14). RESULTS: There was no difference in the preoperative passive knee extension among the groups or the surgeries performed. For children who had passive knee hyperextension, calf lengthening improved static dorsiflexion with knee flexion on clinical exam by 9.3° in the ER group, 9.6° in the LR group as well as dorsiflexion with knee extension on clinical exam by 9.5° in the ER group and 6.4° in the LR group. The kinematic data showed that the ER group improved their knee hyperextension by 11° (p < 0.001), whereas the LR group did not significantly change their stance phase knee position. CONCLUSION: Children with passive knee hyperextension who have a calf contracture and walk in knee hyperextension in the first half of stance phase may improve after calf lengthening.Level of Evidence: III.

Comparison of Rectus Femoris Transfer Surgery Done Concomitant With Hamstring Lengthening or Delayed in Patients With Cerebral Palsy.

BACKGROUND: Children with spastic cerebral palsy frequently develop stiff knee gait. A common treatment of flexed knee gait is lengthening of the hamstring tendons. It has been shown that minimum knee extension improves after hamstring surgeries. However, it has been observed that a decreased peak knee flexion in swing may be a complication of hamstring lengthening (HSL). This has been noted to occur because of an overactive rectus femoris during the swing phase of gait. A common treatment of decreased knee flexion in swing is distal rectus femoris transfer (DRFT). The purpose of this study is to compare the differences between doing DRFT concomitantly with HSL and doing delayed DRFT after HSL. METHODS: A total of 111 children with cerebral palsy (74 males and 37 females) who underwent HSL were reviewed retrospectively. All patients who met the inclusion criteria were divided into 3 groups, 28 subjects in the HSL alone group (H), 57 subjects in the HSL with concomitant rectus femoris transfer group (C), and 26 subjects in the HSL with delayed rectus femoris transfer group (D). RESULTS: The groups had similar minimum knee flexion in stance preoperatively and postoperatively. Group D's minimum knee flexion in stance improved to 5.5±12.7 degrees after HSL, but increased to 8.8±11.6 degrees after DRFT. Groups D and H had statistically significant reduction in maximum knee flexion in swing after HSL (P<0.05). Maximum knee flexion in swing was statistically significantly reduced in the D group after DRFT (P<0.05), but the C group was not statistically different from preoperative after DRFT (P>0.05). The C and D groups had similar total knee excursion postoperatively. The H group had less knee excursion than the other 2 groups, but it was not significant. CONCLUSIONS: The group that had DRFT concomitantly with HSL maintained maximum knee flexion in swing phase postoperatively. Although the group that had delayed DRFT had a reduction in maximum knee flexion after isolated HSL, gains in swing phase motion were achieved after delayed DRFT (comparable to that of the simultaneous group). LEVEL OF EVIDENCE: Level II.

Gait patterns in children with limb length discrepancy.

BACKGROUND: Very few articles describe the compensations in gait caused by limb-length discrepancy (LLD). Song and colleagues explored kinematic and kinetic variables utilizing work equalization as a marker of successful compensation for LLD. They found no difference in strategies based on the location of pathology. The purpose of this study was to define the various gait patterns in patients with LLD and the impact of these compensations on gait kinetics. METHODS: Forty-three children (mean age 12.9±3.7 y) with LLD >2 cm were evaluated in the motion lab using a VICON motion system with 2 AMTI force plates. Etiologies included Legg-Calve-Perthes, developmental hip dysplasia, growth plate damage due to infection or trauma, congenital shortening of the femur or tibia, and syndromes creating shortening of the limb. Evaluation included physical examination and 3-dimensional motion data generated using the model described by Vicon Clinical Manager (VCM). For data analysis, 3 representative trials were processed with the Plug-in Gait lower-body model using the "VCM spline" filter. Walking strategies were identified by visual review. A kinematic threshold of 2 SD away from normal values was used for inclusion in each group. Strategies included: (1) pelvic obliquity with the short side lower (<-1.5 degrees); (2) flexion of the knee of the longer leg in stance (>5.2 degrees); (3) plantar flexion of the ankle on the shorter leg through the gait cycle (<0 degrees); and (4) early plantarflexion crossover of the shorter limb (plantarflexion crossover occurred before 35% of the gait cycle). Variables were extracted into Excel using PECS (Vicon Motion Systems). The mean of the 3 trials was used for analysis. Scanograms were used to establish lengths of the femur and the lower leg including the foot. The percentage difference for the subject (%LLD) was calculated as the leg length between the 2 sides divided by the length of the long side. The total mechanical work over the stride was the sum of the positive work and the absolute value of the negative work in all planes. Paired t tests were used to analyze the work differences between the short limb versus the long limb. Unpaired t tests were used to compare between the different groups (short tibias, short femurs, and controls). RESULTS: Distribution of single strategies for the group included: pelvis (11), equinis (5), vaulting (7), knee flexion (3); 17 subjects used multiple strategies. If the discrepancy was in the femur, patients chose a more distal compensation strategy, utilizing ankle movements, which resulted in more work at the ankle joint on the short limb compared with normal (P<0.0001). All subjects with tibia shortening showed pelvic obliquity (3 combined with knee flexion), which caused more work at the hip joint on the short limb compared with normal (P<0.01). Total mechanical work on the uninvolved limb was above normal for all groups (P<0.0001). CONCLUSIONS: Our study contradicts previous literature that found no difference in strategy on the basis of location of the shortening and also a higher number of children with pelvic obliquity than previously described. It appears that different compensation schemes are used by patients with LLD. The increase in work may have long-term implications for management. Future studies will include changes in kinematics and work, after intervention. Better understanding of postoperative changes from different surgical methods may provide more insight for preoperative planning and may lead to a more satisfactory outcome for specific patients. LEVEL OF EVIDENCE: Level II.

Motion of the center of mass in children with spastic hemiplegia: balance, energy transfer, and work performed by the affected leg vs. the unaffected leg.

Asymmetry between limbs in people with spastic hemiplegic cerebral palsy (HEMI) adversely affects limb coordination and energy generation and consumption. This study compared how the affected leg and the unaffected leg of children with HEMI would differ based on which leg trails. Full-body gait analysis data and force-plate data were analyzed for 31 children (11.9 ± 3.8 years) with HEMI and 23 children (11.1 ± 3.1 years) with typical development (TD). Results showed that peak posterior center of mass-center of pressure (COM-COP) inclination angles of HEMI were smaller than TD when the affected leg trailed but not when the unaffected leg trailed. HEMI showed greater peak medial COM-COP inclination angles and wider step width than TD, no matter which leg trailed. More importantly, when the affected leg of HEMI trailed, it did not perform enough positive work during double support to propel COM motion. Consequently, the unaffected leg had to perform additional positive work during the early portion of single support, which costs more energy. When the unaffected leg trailed, the affected leg performed more negative work during double support; therefore, more positive work was still needed during early single support, but energy efficiency was closer to that of TD. Energy recovery factor was lower when the affected leg trailed than when the unaffected leg trailed; both were lower than TD. These findings suggest that the trailing leg plays a significant role in propelling COM motion during double support, and the 'unaffected' side of HEMI may not be completely unaffected. It is important to strengthen both legs.

Use of a patella marker to improve tracking of dynamic hip rotation range of motion.

Hip rotation during gait has traditionally been measured using thigh wand markers. Hip rotation data calculated using thigh wands shows large variability between different laboratories and underestimates the rotation movement. This study investigated effectiveness of a patella marker in tracking hip rotation range of motion in comparison with traditional thigh wands. In controlled trials of isolated hip internal-external rotation, the patella marker detected 98+/-8% of the actual range of motion, compared with 53+/-10% for a distal thigh wand and 43+/-13% for a proximal thigh wand. The patella marker produced the smoothest hip rotation curves and the smallest hip rotation range in walking, and results from the patella marker did not depend on walking speed. These results suggest that the patella marker is less vulnerable to wobbling, inertial effects, and soft tissue movement than traditional thigh wands. The use of patella markers with knee alignment devices may therefore allow for more accurate measurement of hip rotations during clinical gait analysis than is currently possible using traditional thigh wands.

Cross-correlation as a method for comparing dynamic electromyography signals during gait.

Current clinical interpretation of dynamic electromyography (EMG) data is usually based on qualitative assessments of muscle timing. Cross-correlation may provide a method for objectively comparing the timing and shape of EMG signals. This study used cross-correlation to compare EMG signals from different walking trials, different test sessions, and different individuals in able-bodied adults. Cross-correlation results (R-values) for different walking trials within a single test session were high, averaging > or = 0.90 for all muscles tested (R = 1.0 indicates exact agreement). Cross-correlation values were also high among trials from different test sessions conducted by the same and different examiners (average R > or = 0.78 for all muscles). R-values were much more variable when comparing different subjects (average 0.40-0.81, range 0.00-0.91). R-values were lower for the medial hamstrings and rectus femoris compared with the other muscles tested. These results suggest that cross-correlation may be useful for evaluating changes in an individual patient's muscle activation patterns, such as before and after surgery, but not for comparing EMG patterns among different individuals, such as between patients and normative data. This is especially true for biarticular muscles such as the hamstrings and rectus femoris, which may have variable activation patterns and/or increased sensitivity to electrode placement. Cross-correlation may also be useful for identifying appropriate muscles for transfer, identifying "outlier" trials within a test session, and selecting representative EMG curves for a given patient. The advantages of cross-correlation are that it considers shape of the EMG signal in addition to timing and that the assessments it provides are objective, rather than subjective.

Reliability and validity of visual assessments of gait using a modified physician rating scale for crouch and foot contact.

This study evaluates the visual assessment of gait using portions of the Physicians' Rating Scale (PRS). Thirty children with pathologic gait were evaluated "live" and using full- and slow-speed video. Interobserver reliability (weighted kappa) was 0.57 to 0.74 for foot contact, 0.69 to 0.71 for crouch, 0.30 to 0.40 for hip flexion, 0.57 to 0.65 for knee flexion, and 0.42 to 0.52 for dorsiflexion in stance. Intraobserver reliability (comparing the three conditions) was 0.50 to 0.78 for foot contact, 0.71 to 0.80 for crouch, 0.26 to 0.44 for hip flexion, 0.60 to 0.86 for knee flexion, and 0.39 to 0.61 for dorsiflexion. Observers were correct only 12% to 32% of the time when reporting less than 0 degrees of dorsiflexion and 0% to 29% of the time when reporting more than 20 degrees of hip flexion due to overestimation of hip flexion and underestimation of ankle dorsiflexion. These errors could lead some clinicians to presume the presence of contractures that do not actually exist. Visual assessment using the PRS does not appear to accurately measure what it is most commonly used to assess: ankle position in stance.

Gastrocnemius and soleus lengths in cerebral palsy equinus gait--differences between children with and without static contracture and effects of gastrocnemius recession.

Equinus gait is one of the most common abnormalities in children with cerebral palsy. Although it is generally assumed that the calf muscles are abnormally short in equinus gait, no studies have been done to confirm that the muscles are short and that this shortness contributes to the equinus. This study used musculoskeletal modeling combined with computerized gait analysis to examine medial gastrocnemius (MGAS), lateral gastrocnemius (LGAS), and soleus (SOL) musculotendinous lengths during equinus gait in children with cerebral palsy. All three muscles were abnormally short during equinus gait whether or not the children had equinus contractures (P < or = 0.005). Children with static contractures had shorter maximum static MGAS and LGAS lengths than children with dynamic equinus (P < or = 0.002). The children with static contractures had ratios of peak dynamic length to maximum static length close to 1.0 for MGAS and LGAS (1.005 +/- 0.015) but lower ratios for SOL (0.984 +/- 0.024). For the children with static contracture, these ratios did not change significantly after gastrocnemius recession (P > or = 0.14) because both static and dynamic lengths increased postoperatively (P < or = 0.04). These results support the current clinical understanding of the role of calf "tightness" in equinus gait, including the appropriateness and effectiveness of gastrocnemius recession for children with equinus contracture.

Changes in pelvic rotation after soft tissue and bony surgery in ambulatory children with cerebral palsy.

The authors performed a retrospective review of pelvic rotation in 59 children with cerebral palsy who underwent lower extremity surgery and pre- and postoperative gait analysis. Two groups were studied: a femoral derotation osteotomy (FDRO) group and a soft tissue surgery only (no FDRO) group. Both groups exhibited abnormal pelvic rotation preoperatively and normalization of this abnormal pelvic rotation postoperatively. Though the mean change in pelvic rotation was small (3.3 degrees +/- 6.0 degrees), some patients demonstrated postoperative changes as large as 21 degrees. Variability in pelvic rotation was greater in the no FDRO group than in the FDRO group. Improvement in pelvic rotation occurred both in children with unilateral (hemiplegic) involvement and in those with bilateral (diplegic or quadriplegic) involvement. Surgeons planning lower extremity surgery in children with cerebral palsy should expect improvement in abnormal pelvic rotation in both hemiplegic and diplegic patients, whether or not bony surgery is planned in addition to soft tissue surgery.