Muscle-Tendon Surgery in Diplegic Cerebral Palsy: Functional and Mechanical Changes,
by M. Abel, D. Damiano, M. Pannunzio, and J. Bush, Journal of Pediatric Orthopedics, 1999;19:366–375.
Common impairments in patients with spastic diplegic cerebral palsy are impeded gait and decreased joint mobility. According to the authors, diminished ambulation results from the patient's muscular hypertonicity, decreased motor control, decreased equilibrium, and muscular weakness. Spasticity contributes to decreased joint mobility. Muscle tendon surgery may mediate these impairments by increasing joint motion and allowing for normal musculoskeletal alignment during gait. It is expected that these improvements will also lead to improvements in day-to-day function. Past researchers have found that joint mobility increased and joint alignment improved after muscle tendon surgery. However, these have been retrospective studies and did not use valid tests to assess the gains in parameters such as velocity and stance time during ambulation or function. This study is designed to determine the effects of muscle tendon surgery on joint alignment during gait, and to examine how change in joint motion alters the velocity and stride length in gait. In addition, gross motor functional abilities were measured and assessed for improvements.
Subjects in this study had a diagnosis of spastic diplegia and were able to walk with or without an assistive device for 10 meters. In addition, subjects qualified as surgical candidates based on kinematic abnormalities detected during gait analysis that were secondary to decreased dynamic or passive joint mobility. Subjects were excluded who demonstrated moderate to severe mental retardation, disorders involving the extrapyramidal motor system, use of medications that might affect motor function, or skeletal deformities requiring osteotomies. Subjects underwent either recessions or releases of one or more of the following muscles: hamstrings, gastroc soleus, gracilis, adductor longus and iliopsoas. The same surgeon performed all procedures. Subjects were encouraged to walk starting on the first postoperative day two to three times a day. Physical therapy began the day after surgery with the goals of regaining muscle strength and promoting ambulation. After 12 weeks, the subjects resumed working toward preoperative therapy goals.
Evaluation was conducted through passive range of motion of hip extension and abduction, knee extension and ankle dorsiflexion. A three-dimensional gait analysis consisted of subjects walking barefoot for 10 meters at a volitional speed. The velocity, stride length, cadence, percent support time, total sagittal joint excursion and joint angles were computed for each subject. The Gross Motor Function Measure (GMFM), which measures the functional domains of 1) lying and rolling, 2) sitting, 3) crawling and kneeling, 4) standing, and 5) walking, running, and jumping, was administered and scored for each subject. All measures were gathered from all 30 subjects preoperatively (average of two months before surgery) and postoperatively (average of nine months after surgery). Twenty-one of the subjects were also evaluated at three and six months postoperatively and 27 of the subjects were evaluated for gait changes approximately 26 months after surgery. Data were analyzed by determining the mean of each variable for each subject at each assessment and repeated-measures multiple analyses of variance (MANOVA) were performed for the gait variables and GMFM scores by time postsurgery.
Nine months after surgery, functional status improved in most of the 30 subjects with 20 showing ≥10% improvement in velocity and stride length, whereas three subjects presented a loss of >10% in these same areas. GMFM scores increased in domain four (standing) and domain five (walking, running and jumping) by an average of 3.8% and 3.1%, respectively. The scores in the other three domains did not change. The muscle-tendon recessions and releases resulted in improvements in passive range of motion in the lower extremities nine months postsurgery. On average for all subjects, hip extension, knee extension, and ankle dorsiflexion increased whereas hip abduction and popliteal angle did not change. Hip abduction with hip extended, popliteal angle, and passive knee extension increased significantly in subjects who only had hamstring surgery. Subjects who only had gastrocsoleus release showed improvement in ankle dorsiflexion with the knee extended and flexed, but passive range of motion at the knee did not improve significantly. Subjects who had either proximal gracilis or adductor longus release, in addition to another procedure, demonstrated increases in hip extension as well as hip abduction with the hip extended.
Overall trends in gait analysis at nine months after all surgeries include an anterior tilt of the pelvis, increased knee extension during stance, and decreased knee flexion during swing. Maximal ankle dorsiflexion was achieved later in stance and maximal plantar flexion during stance was decreased. At two years postsurgery, the younger subjects and those with prior limited community ambulation showed increases in velocity and stride length. However, the majority of changes occurred during the first year and not the second year after the operation.
The results indicate improvements in some measured variables after muscle tendon surgery. The gait speed demonstrated a larger percentage of gain after one year as compared with increases in velocity normally seen as a child ages. The GMFM also increased in domains pertaining to walking (domains four and five), and no change was found in the other domains indicating that other functional activities were not sacrificed for the gait improvements. Passive range of motion did increase, although this increase was not as large as that shown in other studies. This smaller gain may be due to the decision of the investigator to lengthen muscles by muscle-tendon recession to preserve strengths of the lengthened muscle. Joint dynamics of the knee were altered by an increase in knee extension during stance and a decrease in knee flexion during swing. However, foot clearance was not affected since hip flexion and ankle dorsiflexion were sufficient for clearance. Changes at the ankle joint included an altered position during late stance, demonstrated by maximal dorsiflexion occurring later during stance phase. This allows for tibial progression over the foot to approach standards that are more normal.
Limitations and Implications
These authors investigated the effects of muscle tendon surgery on joint mobility, gait, and daily function. Recession and releases of muscles are proposed to lessen contractures and decrease the effects of spasticity in muscles, which will consequently enable the child to assume a more upright posture during ambulation and increase stride length. However, children with spastic diplegic cerebral palsy have other impairments as well, such as poor balance, decreased strength and abnormal timing, and recruitment of muscles. These additional impairments will also affect gait and posture and were not controlled in this study. Another uncontrolled variable was the level of spasticity and contractures. In addition, the subjects underwent a variety of surgical procedures, each having specific results depending upon which muscle(s) were released and/or lengthened. The subjects also varied in age from approximately three to 20 years and the gait, musculoskeletal alignment, and functional abilities of individuals in this age range vary a great deal. The functional status of the subjects before surgery was not controlled. Some subjects may have been very limited in activities of daily living whereas others may have been much more independent. All of these factors may influence the outcomes of the study; hence, the generalizability of these results must be questioned.
The investigators did not use a control group, and this is another limitation of the study. The subjects of this study underwent intensive physical therapy after surgery. A control group who received intensive physical therapy on the same schedule but did not have surgery would have been beneficial to examine the implications of this study.
In this study, the same surgeon performed all procedures and made all decisions which permits control of many factors. However, different facilities and surgeons use different techniques and have varied opinions regarding the proper time for surgery and the management of the patient after surgery. These differences will influence the outcomes of muscle tendon surgeries, thus limiting the implications of this study for other populations.
These authors AFFILIATIONSed the important aspect of function and how function is influenced by muscle tendon surgery. Function is an important outcome and needs to be properly studied and analyzed considering the current state of health care. This work establishes a foundation, but additional studies are needed to supplement the present information on the effectiveness of muscle tendon surgeries in patients from this population.