Percutaneous Stone Surgery in Spina Bifida Patients--Are Stone-Free Rates Worth the Risk?

Purpose: Percutaneous stone surgery can be challenging in spina bifida (SB) patients due to their body habitus and spinal cord anomalies. A safe surgical approach may necessitate acceptance of lower stone-free (SF) rates. We seek to determine if anatomic complexity, as measured by spinal cord curvature and torso length, is associated with SF rates after percutaneous stone surgery in SB patients. We hypothesize that increasing anatomic complexity is associated with lower SF rates following percutaneous stone surgery.

Methods: We retrospectively reviewed all cases of percutaneous nephrolithotomy (PCNL) and percutaneous cystolitholapaxy (PC) in patients with SB at our institution. We calculated individual Cobb angles for scoliosis and kyphosis and measured torso lengths to serve as surrogates of anatomic complexity. These parameters were used to test for associations between anatomic complexity and SF rates.

Results: A total of 32 procedures were analyzed (15 PCNL, 17 PC). SF rates for PCNL and PC were 60% and 71%, respectively. For both the PCNL and PC cohorts, there was no difference in age, preoperative stone burden, body mass index, operative time, or estimate blood loss between patients deemed SF or not stone free (NSF) after a single procedure. In the PCNL cohort, worsening scoliosis (higher Cobb angle) and lower SF rates trended toward statistical significance (43° vs. 24°, p = 0.058). In the PC cohort, increasing torso length was associated with lower SF rates (34.1 vs. 28.5 cm, p = 0.02).

Conclusions: Overall SF rates were modest in this population. Cobb angle measurements of scoliosis and kyphosis as well as torso length are novel tools for objectively defining anatomic complexity in the SB population and may help predict success following stone surgery.