Jason J. Haselhuhn

Study Design: Cohort retrospective review. Objective: To investigate placement accuracy and malposition rates of cervical pedicle screws (CPS) using intraoperative CT (O-arm) based three-dimensional navigation. Background: CPS placement is technically demanding due to small pedicle sizes and risk of damage to neurovascular structures in the neck. Computer navigation (CN) has been shown to improve accuracy rates in thoracolumbar pedicle screw placement. However, there are limited studies on CN use for placing CPS. Materials and Methods: We identified 100 patients who underwent CN CPS placement (C3–C7). Screw position was evaluated on axial, coronal, and sagittal planes and graded as follows: 0—fully in bone; I—minor breach deemed inconsequential (<25% of screw width); II—minor breach considered not ideal, but acceptable (25%–50% of screw width); and III—major breach considered dangerous or that compromised strength of fixation. Results: Four hundred thirteen CN CPS screws (C3–C7) were placed in 100 patients (54M:46F). Rates of serious screw malpositions: combined Gr II/III = 42/413 (10.2%). Breaking down the combined Gr II/III screws per level: C3 = 8/33 (24.2%), C4 = 9/63 (14.3%), C5 = 8/72 (11.1%), C6 = 10/85 (11.8%), C7 = 7/160 (4.4%). Conclusion: Our study shows a 10.2% nonoptimal rate (combined Gr II and III) using intraoperative three-dimensional imaging and CN. Our results add to a limited number of studies that have reported on this procedure. To our knowledge, this is the biggest study on a uniform technique of navigated pedicle screw placement that included only subaxial levels C3–C7.

Sacroiliac joint fusion was performed in a patient with a preexisting ipsilateral total hip arthroplasty, with no hip dislocation and unrestricted return to farm work at 3.5 years. Fusion eliminates sacroiliac motion and raises hip contact stress, so adjacent joint health warrants preoperative assessment.

Study Design: Retrospective cohort using pooled individual-level data from four prospective multicenter SIJ fusion trials. Objective: To determine the incidence of subsequent THA in patients with pre-existing SIJ fusion. Summary of Background Data: Finite element investigation demonstrates a 10% increase in hip stress due to sacroiliac joint (SIJ) fusion. This questions the reciprocal clinical effects of SIJ fusion and total hip arthroplasty (THA) on each other. The estimated incidence of THA is 0.1% to 0.5% among the US total population. Methods: Data sets from four prospective multicenter clinical trials (SIFI, SALLY, iMIA, and INSITE) of SIJ fusion using triangular titanium rods between August 2012 and April 2022 were queried. Pelvis radiographs were reviewed to identify the presence of a THA. Patient demographics, follow-up dates, and laterality information from study participants’ medical records were collected and analyzed. Results: A total of 223 patients (158F:65M) were analyzed with a mean age of 51.3±11.2 years and a BMI of 30.3±6.6 kg/m². Pre-existing THA prevalence was 2.8% (95% CI: 1.6%–4.8%). Among 218 patients without prior THA, subsequent THA incidence was 2.3% (95% CI: 1.0%–5.3%) over 3.4±1.5 years follow-up. Age-standardized risk ratios were 36.0 in the 40 to 49 age group, 9.8 in the 50 to 59 age group, and 2.5 in the 60 to 69 age group compared with general population rates. Conclusions: In patients undergoing SIJ fusion in prospective multicenter clinical trials, the prevalence of pre-existing THA was 2.8%. At 3.4-year follow-up, the incidence of new THA was 2.3%. These rates exceed the prevalence and incidence of THA among the general population. Level of Evidence: Level III.

BACKGROUND: Scheuermann kyphosis and pectus excavatum rarely present concomitantly. The sternal-rib complex functions as a “fourth column” of thoracic spine support; its disruption can destabilize the spine and exacerbate kyphosis progression. Traditional surgical indications include curves exceeding 70°–75°, but compensatory mechanism assessment may provide additional indicators. OBSERVATIONS: A 16-year-old male presented with thoracic kyphosis (77°) and pectus excavatum (Haller index 2.8). Staged treatment included the Nuss procedure followed by observation. Despite physical therapy, kyphosis prog ressed to 90° over 28 months. Equal standing versus supine extension lumbar lordosis measurements (78°) indicated exhausted compensatory mechanisms. The patient underwent T2–L2 posterior spinal fusion with Smith-Petersen osteotomies while the Nuss bar remained in place, with bar removal 8 months later. LESSONS: This case demonstrates the biomechanical interdependence between thoracic spine and anterior chest wall as a fourth column and introduces compensatory mechanism assessment as a novel surgical indication. The successful retention of the Nuss bar during spinal correction represents a technical innovation minimizing surgical morbidity. This paradigm shift from curve magnitude–based to functional capacity evaluation may revolutionize timing decisions for spinal deformity correction. https://thejns.org/doi/10.3171/CASE25496

(1) Background and introduction: High-demand lumbosacral fusions are often supplemented with sacral-alar-iliac (SAI) screws. The idealized SAI trajectory was estimated to traverse 35 mm of sacrum before crossing the sacroiliac (SI) joint. However, there is debate on how much osseous purchase SAI screws achieve. The goal of this study was to determine the amount of osseous engagement achieved using a porous fusion–fixation screw (PFFS) when placed in a stacked SAI configuration. (2) Materials and methods: We retrospectively reviewed 40 consecutive patients who underwent sacropelvic fixation with stacked PFFS at our institution from 1 June 2022 to 30 June 2023, using intraoperative computed tomography (CT)-based computer navigation. A snapshot of each screw was taken and the length of purchase within the sacrum and ilium was measured on the axial image along the anterior and posterior aspect of each screw. Nineteen patients did not have adequate images available for review and were excluded. (3) Results: The overall mean anterior sacral engagement was 38.6 mm (±8.2 mm), which was found to be statistically significantly greater than the hypothesized threshold of 35 mm (p < 0.001), while posterior sacral engagement was 28.1 mm (±8.6 mm), which was not found to be statistically significantly greater than the hypothesized threshold of 35 mm (p = 1). The mean difference in sacral engagement between the anatomical location for the cephalad screws was 10.3 mm (p < 0.001) and 10.6 mm (p < 0.001) for the caudal screws. The total sacral surface area available for bone ingrowth for bilateral stacked PFFS was calculated to be 3338.3 mm², while the total iliac surface area available for bone ingrowth was 4364.8 mm². A mean difference in surface area availability between anatomical locations was −689.5 mm² (p < 0.001) for the sacrum and 689.5 mm² (p < 0.001) for the ilium. (4) Discussion and conclusions: The SAI trajectory screws in this cohort of patients achieved approximately 39 mm of sacrum engagement anteriorly and 28 mm posteriorly. This is consistent with prior estimates based on the idealized SAI pathway through the sacrum. PFFSs allow for simultaneous sacropelvic fixation and SI joint fusion, which may reduce the incidence of de novo SI joint pain in patients with long fusion constructs.

Case: Spinal epidural lipomatosis (SEL) is the epidural accumulation of adipose tissue, sometimes associated with steroid use. There are limited reported cases of pediatric SEL. The purpose of this case report was to describe a 15-year-old girl with severe sagittal malalignment secondary to steroid-induced SEL associated with cardiac transplant rejection immunotherapy. She underwent multilevel decompression without traditional deformity correction and fusion, which improved her spinal deformity and symptoms. She had improved sagittal alignment and clinical outcomes at 2-year follow-up. Conclusion: Nonstructural spinal deformities due to SEL can be improved with a limited decompression when nonoperative treatment fails.

Background/Objectives: A variety of techniques for pedicle screw placement exist. Efficiency claims have varied, but limited data are available to support or refute these claims. Our goal was to study our screw placement efficiency, reporting real-time screw placement using O-arm 3D navigation. Methods: We prospectively enrolled patients from July 2019 to February 2022 who were undergoing primary procedures involving thoracolumbar pedicle and pelvic screw placement with O-arm navigation. Screw time began at the first placement of the navigated probe/awl and ended once the navigated screwdriver was removed from the screw head. Confirmatory 3D scans were performed to assess all screw placements. Results: The real-time average to place pedicle screws was 2 min 9 s (SD ± 1 min 5 s); for pelvic screws, this was 3 min 36 s. Screw placement was slightly faster in pediatric patients (2 min 3 s) vs. adults (2 min 24 s), p < 0.001. Screw placement was faster in the thoracic spine (2 min 2 s) vs. the lumbosacral spine (2 min 22 s), p < 0.001. Screw placement was faster in adolescent idiopathic scoliosis (2 min 0 s) vs. all other diagnoses (2 min 24 s), p < 0.001. Screw placement performed by a single attending surgeon (2 min 24 s) was no different from dual-surgeon placement(2 min 13 s), p = 0.35. Conclusions: Our screw placement time is shorter than previously published estimates, and has a very high accuracy rate. While there are variations in how time is reported compared to the previous literature, our study serves as a benchmark for real-time screw placement for future studies. The use of navigation technology for pedicle and pelvic screw placement can be efficient.

Purpose: The Bedrock technique involves fusion of the sacroiliac (SI) joint at the time of long construct spinal fusion extending to the pelvis. This is done with triangular titanium rods (TTR) placed parallel and cephalad to S2AI screws, requiring placement of two implants into the small bony corridor in the teardrop of the pelvis. In our initial 21 cases adopting this technique, we found a 7.1% rate of implant malposition requiring intraoperative repositioning. The objective of this follow-up study was to report on our implant malposition rates over a larger number of cases, to determine a potential learning curve, and to report on strategies for minimizing implant malpositioning. Methods: Surgeries in which SI joint fusion was performed concomitant with spinopelvic fixation using the Bedrock Technique with TTRs and CT-navigation between 5/1/2019 and 5/27/2021 were reviewed. Operative reports were analyzed and any intraoperative TTR/S2AI screw malpositions were recorded. Demographic/surgical information, TTR/S2AI specifications, and PROMs were obtained and analyzed along with risk assessment and correlation of failure between cohorts (α < 0.05). Results: A total of 43 patients were included with a mean length of fusion of 4.8 (1–14 levels). Overall, 86 TTRs and S2AI screws were implanted of which, 4/86 (4.7%) TTRs were repositioned intraoperatively and 1/86 (1.2%) was removed and replaced with allograft, while 0/86 (0%) S2AI screws were malpositioned. All TTR malpositions were medial and/or cephalad. In the initial 21 cases, 3/42 (7.1%) TTRs required intraoperative repositioning; this decreased in the subsequent 22 cases to 2/44 (4.5%) with a non-significant relative risk of 1.57 ( p = .664). Malposition was non-significantly negatively correlated to time (r = -.135; p = .39). Our patients showed statistically significant ( p < .001) one-year improvements in mean ODI, VAS back, and PROMIS-10 metrics, meeting MCID for ODI and VAS back. Conclusions: Posterior placement of a TTR above an S2AI screw poses technical challenges due to the natural cephalad narrowing of the bony corridor in the teardrop and blunt tip of the implant which predisposes it to medial skiving as it is passes through the SI joint. Our overall intraoperative reposition rate for caudal S2AI screws was 0% compared to 5.8% for cephalad TTRs, which decreased from 7.1 to 4.5% between our first- and second-year cohorts, suggesting a potential learning curve. All malpositions occurred medially and/or cephalad, and over time we transitioned our technique to placing implants as low as possible in the teardrop to minimize this risk.

Fibrous dysplasia (FD) is a rare, benign fibro-osseous disorder that can compromise structural integrity, particularly in weight-bearing bones like the sacrum. Managing sacral FD is challenging due to the need for both lesion control and biomechanical stabilization. A 34-year-old woman presented with chronic right sacral pain, functional impairment, and a large lytic lesion in the right sacral ala, later confirmed as FD. Conservative treatment, including physical therapy and epidural steroid injection, failed to provide relief. Imaging revealed an impending pathological fracture, prompting surgical intervention. A minimally invasive approach, including curettage, bone grafting, and iliosacral fixation with ingrowth screws, was performed. The patient experienced significant pain relief, functional improvement, and sustained stability, with 2-year follow-up confirming stable fixation and complete lesion filling. This case highlights the role of minimally invasive sacropelvic fixation in preventing structural failure in sacral FD. Integrating biomechanical stabilization with targeted lesion management optimizes outcomes. Long-term follow-up is essential to monitor implant stability and bone remodeling. https://thejns.org/doi/10.3171/CASE25159.