Clinically practical formula for preoperatively estimating the cutting rate of the spinal nerve root in a functional posterior rhizotomy
A functional posterior rhizotomy (FPR) ideally involves minimal cutting of the posterior root while providing maximal reduction of disabling spasticity. However, the ideal cutting rate has yet to be determined. It was hypothesized that the cutting rate of the posterior root would negatively correlate with preoperative motor function in children with spasticity.
Children who underwent an FPR between March 1996 and March 2017 and whose pre- and postoperative data were followed more than a year were enrolled. The preoperative Gross Motor Function Measure (GMFM) score and the overall cutting rate of the posterior root were plotted on a scatter plot, and a simple linear regression analysis was performed. The rationale for the cutting rate of the posterior root was tested by postoperative chronological changes in the GMFM score up to 5 years after the FPR. The Gross Motor Function Classification System (GMFCS) was used to group the children. The postoperative and preoperative GMFM were compared at each GMFCS level.
One hundred thirty-seven children (aged 2 to 19 years old, mean 5.9 years old) met the selection criteria. The cutting rate of the posterior root ranged from 17 to 83%, (mean 48.3%). A scatter plot was then made using GMFM scores between 10 and 90. The formula for the simple linear regression analysis was y = − 0.5539x + 73.896 (x, GMFM score; y, overall cutting rate (%)). The formula was further approximated based on the scatter plot findings as y = 100 - x. The postoperative GMFM showed an improved average score for all GMFCS levels although statistically significant improvement at postoperative 5 years was confirmed in only the GMFCS level 1 group.
The findings of this study supported the hypothesis of the negative correlation of the cutting rate of the posterior root with preoperative motor function in children with spasticity. The amount of posterior nerve root/rootlet cutting during FPR negatively correlated with the preoperative GMFM score. The approximated formula is simple, practical for clinical use, and helpful for preoperatively estimating the required overall cutting rate for the posterior root. The suggested cutting rate induced by the approximated formula should be used as a reference value and be modified according to preoperative motor function, severity and distribution of spasticity, the result of intraoperative neurophysiology, and other factors.
KeywordsRhizotomy Spasticity GMFM Surgery Cerebral palsy
The author thanks Dr. Yuji Wada (Department of rehabilitation medicine, Tokyo Metropolitan Children’s Medical Center), Dr. Keiji Hashimoto (former head, Department of rehabilitation medicine, National Center for Child Health and Development), and the physical therapists at both institutes for their support in the pre- and postoperative evaluation of children who underwent FPR. The author would also like to thank Mr. James Robert Valera for his editorial assistance and professional advice on the manuscript.
Compliance with ethical standards
Conflict of interest
The author has no conflict of interest.
- 11.Fasano VA, Broggi G, Zeme S (1988) Intraoperative electrical stimulation for functional posterior rhizotomy. Scand J Rehab Med Suppl 17:149–154Google Scholar
- 12.Foerster O (1913) On the indications and results of the excision of posterior spinal nerve roots in men. Surg Gynecol Obstet 16:463–474Google Scholar
- 30.Nishida T, Storrs B (1991) Electrophysiological monitoring in selective posterior rhizotomy for spasticity. Principles, techniques and interpretation of responses. In: Sindou M, Abbott R, Keravel Y (eds) Neurosurgery for spasticity. A multidisciplinary approach. Springer-Verlag, New York, pp 159–163CrossRefGoogle Scholar
- 31.O’Brien DF, Park TS, Puglisi JA, Collins DR, Leuthardt EC (2004) Effect of selective dorsal rhizotomy on need for orthopedic surgery for spastic quadriplegic cerebral palsy: long-term outcome analysis in relation to age. J Neurosurg 101:59–63Google Scholar
- 33.Park TS, Gaffney PE, Kaufman BA, Molleston MC (1993) Selective lumobosacral dorsal rhizotomy immediately caudal to the conus medullaris for cerebral palsy spasticity. Neurosurgery 33:929–934Google Scholar
- 34.Peacock WJ, Arens LJ (1982) Selective posterior rhizotomy for the relief of spasticity in cerebral palsy. S Afr Med J 62:119–124Google Scholar
- 35.Phillips LH II, Park TS (1989) Electrophysiologic studies of selective posteiror rhizotomy patients. In: Park TS (ed) Neurosurgery: state of the art reviews 4. Management of spasticity in cerebral palsy and spinal cord injury. Hanley & Belfu, Philadelphia, pp 459–469Google Scholar
- 38.Russel DJ, Avery L, Rosenbaum PR, Raina P, Walter SD, Palisano RJ (2000) Improved scaling of the gross motor function measure for children with cerebral palsy. Phys Ther 80:873–885Google Scholar
- 39.Russell DJ, Rosenbaum PL, Avery L, Lane M (2002) Gross Motor Function Measure (GMFM-66 and GMFM-88): user’s manual. MacKeith Press, LondonGoogle Scholar