How does thoracic kyphosis affect patient outcomes in growing rod surgery?

Retrospective review of a multicenter series.

This study was conducted to specifically identify the complication rate of growing rod surgery in patients with normal (10°-40°) versus abnormal thoracic kyphosis.

Surgical treatment options for progressive early onset scoliosis include spinal fusion versus growth-sparing techniques. The current most commonly employed growing rod technique involves short fusions at the foundation sites using either hooks or screws as anchors and placement of dual growing rods spanning the deformity. Although the coronal deformity in these patients has been studied extensively, the sagittal profile has received less attention as a possible factor in complication rates and patient outcomes.

Out of 387 patients who underwent surgical placement of growing rods, 90 patients had complete clinical and radiographical data, with 2-year follow-up after initial surgery. Patients were categorized into 3 groups on the basis of preoperative thoracic kyphosis magnitude: less than 10° (K- group), 10°-40° (N group), and more than 40° (K+ group). Patient diagnosis, demographics, surgical information, radiographical measurements, and complication types were tabulated and analyzed. A P value of <0.05 was considered significant for all statistical tests.

The K- group experienced 27 total complications including 15 general medical complications, the N group had 20 total and 4 general complications, and the K+ group had 55 total and 22 general complications. Patients in the K+ group were 3.1 times more likely to experience a complication than those in the N group, which was statistically significant (P < 0.05). When considering all types of complications, length of follow-up, T2-T5 proximal kyphosis, postoperative Cobb angle, and rod diameter were identified as confounding variables. When the confounding variables were taken into consideration in the analysis, the odds ratios were no longer significant between the N and K+ groups. Patients in the K+ group and K- group were 2.95 and 2.89 times more likely to experience a general medical complication than those in the N group, respectively (P > 0.05). The rate of implant-related complications between the groups did not reach statistical significance, although the K+ group had the most implant complications (n = 34), including 25 rod breakages in 16 patients. Syndromic patients had 2.9 times the risk of having an overall complication when compared with the entire patient series (P < 0.05). The number of patients who experienced multiple complications was higher in the K- and K+ groups than in the N group.

Patients with thoracic hyperkyphosis present even more of a challenge with respect to complications, specifically implant-related complications. Our study shows that growing rod surgery in patients with kyphosis more than 40° has significantly more general and implant complications than that in patients with normal thoracic kyphosis. Implant complications were more common in hyperkyphotic (>40°) patients and increased linearly with increasing kyphosis. The most common implant complication was rod breakage. Patients with hyperkyphotic thoracic spines, particularly syndromic patients, must be monitored closely and parents should be counseled regarding the likelihood of future adverse events.