Comment on: Thomason et al.: “Knee surveillance for ambulant children with cerebral palsy”: J Child Orthop 2025;19(4): 253–256

To the Editor JCO:

I am writing regarding the recent publication in JCO by Thomason et al: “Knee surveillance for ambulant children with cerebral palsy.” I congratulate this esteemed group of authors for the excellent and comprehensive guidelines for the assessment and treatment of the sagittal plane kinematic abnormalities at the knee in ambulatory children with Cerebral Palsy. I would however take issue regarding their comments on lateral hamstring lengthening.

There seems to be a long-standing misunderstanding of the value of this procedure in the orthopedic community, perhaps dating back to the mid-20th century, when the Eggers procedure became popular, wherein all hamstring insertions were transferred to the femoral condyles, and which unfortunately frequently resulted in the development of severe knee recurvatum.

The support cited in this current paper for avoidance of lateral hamstring lengthening is a consensus study using the Delphi method. ¹ This study cited as evidence the only study in the literature at that time which assessed the outcome of the addition of lateral hamstring lengthening to medial surgery on sagittal plane motion at the knee in cerebral palsy patients. However, this study actually supports the addition of lateral hamstring lengthening to medial surgery, and concluded that there “was a suggestion that combined medial/lateral hamstring lengthening may provide greater improvement in popliteal angle and maximum knee extension in stance.” ² On the negative side, this latter study also reported an increased level of knee recurvatum in the combined group which the authors theorized may have been due to “concomitant calf spasticity.”

A second study from our group at the Portland Shriners hospital on the issue of the addition of lateral hamstring lengthening to medial surgery, appeared in JCO subsequent to this consensus paper, and cited in the Thomason et al. paper (their ref. 57), showed a significantly greater percentage correction of stance knee flexion in those more severe patients who had lateral lengthening in addition to medial lengthening +/− transfer as compared to those having medial hamstring surgery alone, as well as a 69% success rate in GMFCS I and II and 60% in GMFCS III patients at long-term follow-up (mean 9.2 years). ³ Furthermore, this study found no significant increase in anterior pelvic tilt and an improvement in maximum hip extension in late stance as compared to preoperative measurements in the group who had the addition of biceps lengthening. Finally, there was only one case of knee recurvatum >5° in those patients who had the addition of lateral hamstring surgery.

If the medial hamstrings alone are lengthened, and the biceps femoris is left intact in patients with more severe degrees of dynamic deformity and contracture, this is likely to contribute to incomplete correction and a greater risk of recurrence. The biceps femoris is well-suited for fractional lengthening with its tendon extending far proximally on the muscle belly, so the lengthening can be easily performed technically without risk of complete tenotomy.

Perhaps the difference in the incidence of knee recurvatum between this second study and that of Kay et al. is accounted for by the fact that this study reserved the lateral release for those patients with a greater degree of stance knee flexion and contracture. Thus, to achieve an optimal outcome, we must apply an adequate, but not excessive surgical “dose.”

A second concern I have is the recommendation for postoperative management, wherein long sitting with extended knees is recommended. Although the authors mention the risk for neuropraxia, I think this serious complication should be emphasized. Although prevention of knee flexion postoperatively with an knee orthotic is beneficial, full upright sitting with the knee extension orthotic in place with 90° hip flexion should be avoided in the immediate postoperative period, as excessive hip flexion with the knee held in extension will lead to further sciatic stretch.

I was also surprised that this article did not include the influence of the limitation of hip extension on the dynamic knee deformity in stance, which this group of authors, who were instrumental in the recognition of SEMLS, surely recognize.

Although I have expressed these few concerns, I recognize this as a work of great significance to guide clinicians in the treatment of children with spastic diplegia.

Michael D. Sussman, M.D.

Supplemental Material

sj-pdf-1-cho-10.1177_18632521251396648 – Supplemental material for Comment on: Thomason et al.: “Knee surveillance for ambulant children with cerebral palsy”: J Child Orthop 2025; 19(4): 253–256

Supplemental material, sj-pdf-1-cho-10.1177_18632521251396648 for Comment on: Thomason et al.: “Knee surveillance for ambulant children with cerebral palsy”: J Child Orthop 2025; 19(4): 253–256 by Michael D Sussman in Journal of Children's Orthopaedics