In-toeing gait is a common feature of cerebral palsy (CP) children that causes poor cosmesis and function 1–3. In-toeing is the result of abnormal muscle tone, internal torsion of the femur and tibia, and various foot deformities 4,5. Torsional deformity of the femur or the tibia causes lever-arm disease and reduces the efficiency of muscles during walking 6. Among these, medial femoral torsion (MFT) is the most common pathology of in-toeing gait in CP children.
Surgical correction of MFT is recommended in CP children to resolve the inefficient lever-arm of torsional deformity 1. Femoral derotational osteotomy (FDO) could correct MFT in CP children and directly improve the foot progression angle (FPA) and hip rotation angle in the transverse plane. In addition, it is indicated when in-toeing is principally because of MFT. Many authors have reported that various gait parameters improve or change after FDO to varying degrees 1,3,7,8. There are, however, few papers on correlations between the amount of derotation by FDO and the degree of changes in gait parameters after FDO 9. FDO can be performed proximally and distally. The proximal FDO is frequently performed to decrease the increased anteversion and at the same time to correct other hip problems, such as valgus angulation of femoral neck, subluxation of hip joint, and others. There may be some bias when analyzing the simple correlation between the derotation angle by proximal FDO and postoperative kinematic changes in CP patients with hip problems 1. The aim of this study was to analyze how much the kinematic data and Staheli’s rotational profiles changed after a certain degree of distal FDO in CP patients.
Patients and methods
This retrospective analysis included CP patients younger than 20 years of age who underwent distal FDO to correct MFT between 2010 and 2013. The average follow-up period was 3.8 years (2–7.5 years). The study group included 19 spastic CP patients (28 lower limbs) with the Gross Motor Function Classification System level I or II. All the patients underwent a derotational osteotomy in the distal femur. MFT and gait of the patients were evaluated with Staheli’s rotational profile and gait kinematics. A preoperative evaluation was performed 1 day before surgery and a postoperative evaluation was performed 1 year after surgery. Exclusion criteria were as follows: subluxated hip, previous selective dorsal rhizotomy, and injections of botulinum toxin A in the previous 6 months. Also, CP patients who had been treated for long bone fractures or for torsional deformities in segments (tibia or foot) other than the femur were excluded.
The study group was divided into the bilateral group (BG) (nine cases, CP spastic diplegia patients) and the unilateral group (UG) (10 cases, usually CP spastic hemiplegia patients) for analysis. At the time of surgery, the mean age of the study group was 13.2 years (range: 4–20, the BG: 12.5 years, and UG: 13.9 years). There were 10 male and nine female patients in the study group. There were four male patients in the BG and six patients in the UG (Table 1).
All surgeries were performed by a single senior surgeon. Surgical treatment of each patient was planned according to the principles of single-event multilevel surgery by Gage or SMILE by Sussman, and various operations in different segments were performed simultaneously, including FDO (Table 1). Distal FDO was indicated for patients with symptoms and increased MFT. Patients’ symptoms included tripping or a patient susceptible to fall down during walking. FDO was indicated with limited external rotation of the hip less than 15° on physical examination and hip internal rotation and internal FPA with a difference of more than 10° from the norm on kinematic data.
Preoperatively, we decided on the amount of derotation using various data such as Staheli’s rotational profile, computed tomography (CT) torsional study, and kinematics of gait analysis. A CT torsional study was carried out as a routine preoperative evaluation together with the gait analysis. However, the CT torsional study was not carried out postoperatively, unlike the gait analysis, and was excluded from statistical analysis. The mean amount of derotation was 24.6° by the FDO (a mean of 25.0° for the UG and a mean of 24.4° for the BG).
Derotational osteotomy was performed at the distal femur in the supine position. The distal femur was approached on the lateral side. Two guide wires (Kirschner wire, 1.6 mm) were inserted tilted as much as the predetermined correction angle proximal and distal to the osteotomy site. After the osteotomy, the distal segment was externally rotated so that the two guide wires were positioned parallel to one another. Then, the osteotomy site was internally fixated using an AO locking compression plate (LCP). Narrow or broad AO LCP was chosen according to the patient’s femur size. A cylinder splint was applied for 2 weeks postoperatively. Knee range-of-motion exercise was started 1 week after surgery. Partial weight bearing was allowed 2 weeks after surgery.
Evaluation of deformity
The effects of FDO were assessed by comparing preoperative Staheli’s rotational profile and gait kinematics with postoperative values. Staheli’s rotational profile was checked at the time of gait analysis. Among the five parameters of Staheli’s rotational profile, the degree of internal and external rotation of the hip joint, which reflects the femoral torsion, was used for evaluation 10,11. Hip rotation was measured in the prone position using a goniometer.
Gait analysis was carried out preoperatively and postoperatively. A preoperative gait analysis was carried out 1 day before the surgery and a postoperative gait analysis was carried out in patients after obtaining their informed consent when they were readmitted for the removal of internally fixated implants. The plate and screws were removed 1 year after surgery in most cases.
For gait analysis, passive reflective markers were attached using the modified Helen-Hayes method. Optical tracking of reflective markers was performed using the Eagle camera system (Eagle system; Motion Analysis, Santa Rosa, California, USA) at a capture frequency of 120 frames per second. EvaRT version 4.2 (Motion Analysis) and Orthotrak (Motion Analysis) softwares were used for data processing to obtain kinematic data from the three-dimensional gait analysis.
We analyzed the amount of changes in various parameters after a certain amount of derotation by FDO (mean of 24.6°; 25.0° for the UG and 24.4° for the BG). The paired t-test was used to analyze changes in rotational profiles and kinematic data after FDO. Linear regression was used to evaluate the amount of change after derotational osteotomy. Statistical analysis of the correlation was carried out using the Pearson correlation test, with a 95% confidence interval (P<0.05) for statistical significance. The SPSS (version 18.0; SPSS Inc., Chicago, Illinois, USA) program was used.
Staheli’s rotational profile
The mean internal hip rotation was 71.4±6.9° before surgery and 48.6±10.7° after surgery in the UG, meaning that a decrease of 22.8° occurred after surgical derotation of 25.0° (P<0.05). A decrease of internal rotation in the BG was 22.9° (P<0.05), with 63.8±15.8° before surgery and 40.9±9.2° after surgical derotation of 24.4°. The changes in internal rotation in both groups (22.8°, 22.9°) were almost proportional to the amount of surgical derotation (24.6°) (Table 2).
The mean external hip rotation in the UG was −14.3±15.9° before surgery and −41.4±10.3° after surgery (a minus sign denotes ‘external’ in this study), showing an increase of 27.1° (P<0.05), which is the change almost equal to the amount of surgical derotation (25.0°). In the BG, the mean external hip rotation increased by about 16.6° (P<0.05), with −32.5±14.5° before surgery and −49.1±16.4° after surgery, which is almost two-thirds of surgical derotation (24.4°).
Foot progression angle and hip rotation
The mean FPA (a minus sign indicates ‘external’ for the kinematic data) was −2.1° during gait in the UG before surgery and −13.8° after surgical derotation of 25.0° (P<0.05). In the BG, FPA was 3.1° preoperatively and −9.5° postoperatively (P<0.05); FPA was 12.6° more outward after FDO. In both groups, FPA showed changes in parameters equal to 50% of surgical derotation.
Hip rotation during gait is a parameter directly affected by the FDO. In the UG, the mean hip rotation during gait was 15.9° before surgery and 1.1° after surgery, which meant that the hip joint was rotated more externally by 14.8° after surgical derotation of 25.0° (P<0.05). The BG showed a hip rotation of 7.4° before surgery and an average of 0.7° after surgery, meaning that the hip joint rotated externally by 6.7° after derotation of the femur by 24.4° (P<0.05).
Foot and knee rotation
FDO is a surgical procedure on the femur and basically it does not affect the transverse kinematics of other segments, such as foot rotation or knee rotation. In the UG, the average foot rotation (a minus sign denotes ‘external’ for the kinematic data) was −4.1° preoperatively and −5.4° postoperatively. In the BG, it was 2.0° before surgery and −3.0° after surgery. In both groups, foot rotation was not affected by the FDO (P>0.05).
Knee rotation mostly reflects tibial torsion, and in the UG, the mean knee rotation was −12.7° before surgery and −10.1° after surgery (P>0.05), which meant that it was not influenced by the FDO. However, in the BG, it was −4.7° before surgery and −14.3° after surgery, which meant that knee rotation was changed by 9.6° after FDO (P<0.05).
In the UG, the mean pelvic rotation was 0.4° preoperatively and 0.6° postoperatively (P>0.05). In the BG, the mean pelvic rotation was 0.5° preoperatively and 0.2° postoperatively (P>0.05). Pelvic rotation was not changed after surgery in both groups.
However, in the patients with compensatory pelvic rotation of more than 5° preoperatively, pelvic rotation showed a change of about 5.4±4.8° in the UG and 6.6±1.5° in the BG after surgery (P<0.05). There was also a trend indicating that the younger the patient, the more the pelvic rotation changed (P=0.069). The total range of pelvic rotation during gait was not meaningfully changed (16.0°–15.7°) in the UG (P>0.05). However, it showed a significant difference in the BG postoperatively (21.2°–15.4°; P<0.05).
There were no complications, such as nonunion or operative wound infection, in any of the patients.
Classifications, such as the classification of Winters and colleagues 12,13, of the pathologic gait in CP children are mostly focused on the sagittal plane. The most common pathologic gait of CP children in transverse plane is in-toeing gait caused by MFT. MFT causes lever arm dysfunction which reduces muscle efficiency by reducing the coronal plane hip abductor moment arm. And it also causes inappropriate foot clearance and tripping. 6,14.
It is well known from previous studies that MFT can be corrected with FDO. It is, however, not clear to what degree transverse gait parameters, including hip rotation, FPA, pelvic rotation, and others, are changed after surgery. In this study, we attempted to answer these questions. FDO was performed at the distal femur and internally fixated with AO LCP. The advantage of LCP was that derotation of the distal segment could be performed accurately as planned and early rehabilitation could be started without immobilization in the long leg cast.
Parameters that are directly affected by FDO are internal and external hip rotation in Staheli’s rotational profile and FPA and hip rotation in the gait analysis. Pirpiris et al.1 reported that internal and external hip rotation in the prone position improved as much as the amount of FDO in CP patients, which is in agreement with this study. Chung et al.15 showed that FPA improved by two-thirds of the amount of FDO after bilateral FDO in diplegic CP. In this study, FPA improved about half of the FDO in both groups. FPA improved less than the amount of FDO 15.
The change in FPA is roughly the sum of rotation changes in all the segments of lower extremity. In the UG, improvement in FPA occurred entirely at the femur (hip rotation), which was equal to half of FDO. In the BG, superficially, it appeared as if half of the FPA improvement (6.7°) took place at the femur (hip rotation) and another half of the improvement (9.6°) took place at the tibia (knee rotation) according to the kinematic data.
Knee rotation was not changed postoperatively in the UG, as expected. In the BG, knee rotation changed by as much as one-fourth of FDO, even though theoretically it should not be affected by the FDO. Transverse kinematic data of the BG were confusing as the improvement in FPA took place at the femur and tibia. This might be because of measuring error that is prone to occur in the transverse plane compared with other planes.
There are still debates on whether compensatory pelvic rotation is corrected after FDO. Some authors, including Chung et al.15 and Christopher et al.16, reported that pelvic rotation in spastic diplegia was not changed even after normalization of femoral torsion by FDO.
There are more debates on spastic hemiplegias. Gage et al.6 reported that pelvic external rotation cannot be corrected after FDO in hemiplegic patients. He recommended a slight undercorrection during FDO for hemiplegias because of the above-mentioned reason. Meanwhile, Christopher et al.16 reported that hemiplegic patients showed a significant improvement in pelvic rotation after FDO. In this study, the overall pelvic rotation was not changed after FDO in both groups.
As the study group included many patients without compensatory pelvic rotation, we reanalyzed changes in pelvic rotation only in patients with preoperative pelvic rotation of more than 5°. In these patients, preoperatively externally rotated pelvis showed normalization of rotation after FDO in both the UG and the BG (P<0.05). In addition, the degree of change tended to be larger in younger patients. These facts suggest that compensatory pelvic rotation may be corrected after FDO if the deformity is not a fixed one as in young children.
The range of pelvic rotation is a parameter that reflects the energy efficiency of ambulation. The fact that range of rotation has increased means that additional energy was used to transfer the center of gravity to achieve an adequate stride length. There was no major change in the range of rotation in the hemiplegia group (0.3° decrease, P=0.87), but there was a statistically significant decrease in the diplegia group (5.8° decrease, P<0.05, Figs 1–3). Therefore, a decrease in the range of pelvic motion after FDO might be an indication that FDO may improve energy efficiency during gait.
There are some limitations in this study. First, we did not analyze the effect of soft tissue procedures, such as psoas or hamstring release, and foot procedures, such as split tibialis anterior tendon transfer, heel cord lengthening, or calcaneal lengthening. However, they may mainly influence motion in the sagittal plane and seem to have a slight effect in the transverse plane. Second, two young patients (4 and 5 years old) were included in this study. This may have affected the results. Third, our results were analyzed 1 year after operation. Hence, we do not have long-term follow-up results. Further research is needed.
Conclusions and clinical significance
In-toeing gait because of MFT could be corrected with FDO. FPA and hip rotation on the kinematics were corrected and the amount of correction was about a half of the surgical derotation angle. The degree of compensatory pelvic rotation should be considered to plan the derotation and decide the correction angle. Patients with pelvic rotation larger than 5° before the surgery showed the normalization of pelvic rotation after FDO. This phenomenon was obvious in young patients. Pelvic rotation in aged patients, whose pelvic rotation is considered to be already fixed, did not significantly change even after a surgery. Future research on FDO impact on clinical practice and the patient`s quality of life is needed.
Conflicts of interest
There are no conflicts of interest.
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