Quadriceps and Hamstring Strength Changes as a Function of Selective Dorsal Rhizotomy Surgery and Rehabilitation.

Ross SA, Engsberg JR, Olree KS, Park TS (Human Performance Laboratory, Barnes-Jewish and St Louis Children's Hospital; Washington University School of Medicine, St Louis, Mo), Pediatric Physical Therapy. 2001;13:2-9.

According to the authors, the effects of selective dorsal rhizotomy (SDR) and rehabilitation are controversial subjects in the literature. In particular, they noted that decreased strength appeared to be a complication of SDR and that muscle weakness in potential candidates was considered a contraindication for surgery; however, strength was not routinely or objectively measured during patient selection or after the rhizotomy.

The purpose of this study, therefore, was 2-fold. The first purpose was to quantify the presurgical levels of strength (defined as maximum torque and work) of the quadriceps and hamstring muscles and compare them to the postsurgical and rehabilitation levels in children with cerebral palsy (CP). The authors hypothesized that strength would significantly increase after SDR and rehabilitation. The second purpose was to compare the presurgical and postsurgical measurements of strength to the measurements for children without disabilities. The authors hypothesized that children without disabilities would be significantly stronger than children with CP, both before and after SDR.

The subjects, a sample of convenience, included 20 children without disability (WD [without disability] group; 10 boys, 10 girls; mean age=9 [+ or -] 3.2 years, range=4-16 years) and 19 children with spastic diplegia (CP group; 9 boys, 10 girls; mean age=9 [+ or -] 4.2 years, range=4-16 years). After reviewing prior studies for methods of strength testing in children with CP, the authors chose to use the Kincom dynamometer. This isokinetic method of testing allowed the authors to obtain a measurement of strength defined as maximum torque and work throughout a range of motion. The children with CP were tested the day before surgery and approximately 8 months after the SDR. The children without disability were tested one time only.

For all children, the authors attempted to obtain data from both legs and then randomly selected the data from one leg for analysis. The same leg was tested before and alter surgery. After surgery, the children with CP received inpatient physical therapy twice per day, beginning on postsurgical day 3. The interventions were aimed at improving range of motion, strength, and functional abilities. After discharge, the children continued intensive physical therapy sessions of 45 to 60 minutes in length, 4 to 5 times per week for 8 months, and they also received a daily home exercise program.

Results demonstrated that all children without disabilities were able to sustain flexor and extensor torque throughout the range of motion; however, before the surgery, 63% of the children with CP were unable to sustain either a flexor or extensor torque throughout the range of motion. After the SDR, 63% of the children with CP were still unable to sustain extensor torque production, but only 47% were unable to sustain a flexor torque. The extension maximum torque and the flexion maximum torque for the children with CP before and after the SDR and rehabilitation were significantly less than for the children without disabilities. The extension and flexion work for the children with CP before and after the SDR were also significantly less than for the children without disabilities.

According to the authors, the results supported their hypothesis that children without disabilities would be significantly stronger that children with CP before and after the SDR and rehabilitation. A comparison of the presurgical and postsurgical data for the children with CP yielded significantly greater strength measurements after the SDR and rehabilitation for both quadriceps and hamstring muscle peak torque and work. According to the authors, this finding supported the hypothesis that strength would significantly increase as a result of surgery and rehabilitation.

Because certain children did not show gains in strength, but showed losses after surgery and rehabilitation, the authors offered a discussion of the limitations and significance of this study. Concerning the methods and interpretation of the results, the authors noted that (1) electromyography was needed to help differentiate reasons for weakness of knee extension at end-range, (2) it was necessary to distinguish among the contributions of strength, spasticity, and motor control to the production of torque and work, (3) poor surgical selection was a possible cause of the large standard deviation in the results, (4) it was necessary to link impairments and change in impairments to improved function or reduced disability, (5) the maturation of the children with CP was a possible contributor to changes in strength, and (6) the study provided additional support for the use of an isokinetic method of strength testing rather than an isometric method of strength testing.

The authors concluded that children with CP, after SDR and rehabilitation, generally improved their hamstring and quadriceps muscle strength, but their strength was significantly less than that of children without disabilities. The weakness was especially evident as the knee approached full flexion or extension; therefore, the authors believed that it is important to strengthen the end-ranges of knee extension and flexion in children with CP.

Karen Kott, PT, PhD
SUNY Health Science Center at Syracuse
Syracuse, NY