Scheuermann kyphosis: The importance of tight hamstrings in the surgical correction

Study Design. A historic cohort study of the sagittal alignment in 33 consecutive patients with surgically corrected thoracic Scheuermann kyphosis. Objectives. To determine if postsurgical imbalance, sagittal malalignment, and decreased lumbar-pelvic range of motion in patients with thoracic Scheuermann kyphosis is related to tight hamstrings. Summary of Background Data. Tight hamstrings are a frequent sign in Scheuermann kyphosis. The importance of tight hamstrings in the surgical management of Scheuermann kyphosis has not yet been studied. Methods. Thirty-three patients with Scheuermann kyphosis were managed by surgical correction and fusion. Tight hamstrings, lumbar-pelvic range of motion, and sagittal balance were evaluated. Sixteen patients had tight hamstrings, and 17 patients had nontight hamstrings. Hamstrings were considered tight if the popliteal angle was >30degrees. Results. Patients with tight hamstrings have a significantly greater risk of postoperative imbalance ( P = 0.05), and these patients can only compensate for this risk by reducing their lumbar lordosis ( P = 0.0227). Furthermore, the limitations in the lumbar and pelvic range of motion are predicted by tight hamstrings ( P less than or equal to 0.005). Conclusion. Tight hamstrings can be considered as an important factor in the surgical management of thoracic Scheuermann kyphosis. Tight hamstring patients can be classified as "lumbar compensators" and as such are prone to overcorrection and imbalance. Preoperative assessment of the lumbar-pelvic range of motion and tight hamstrings should therefore be advised. Extensive fusion of the lumbar segments might compromise the lumbar compensation mechanism and induces further risk of imbalance.