Object The diagnosis and treatment of Chiari malformation Type I (CM-I) has evolved over the last few decades. The authors present their surgical experience of over 2 decades of treating children with this form of hindbrain herniation. Methods The authors conducted a retrospective review of their institutional experience with the surgical treatment of the pediatric CM-I from 1989 to 2010. Results The 2 most common presentations were headache/neck pain (40%) and scoliosis (18%). Common associated diagnoses included neurofibromatosis Type 1 (5%) and idiopathic growth hormone deficiency (4.2%). Spine anomalies included scoliosis (18%), retroversion of the odontoid process (24%), Klippel-Feil anomaly (3%), and atlantooccipital fusion (8%). Approximately 3% of patients had a known family member with CM-I. Hydrocephalus was present in 48 patients (9.6%). Syringomyelia was present in 285 patients (57%), and at operation, 12% of patients with syringomyelia were found to have an arachnoid veil occluding the fourth ventricular outlet. Fifteen patients (3%) have undergone reoperation for continued symptoms or persistent large syringomyelia. The most likely symptoms and signs to resolve following surgery were Valsalva-induced headache and syringomyelia. The average hospital stay and “return to school” time were 3 and 12 days, respectively. The follow-up for this group ranged from 2 months to 15 years (mean 5 years). Complications occurred in 2.4% of cases; there was no mortality. No patient required acute return to the operating room, and no blood transfusions were performed. Conclusions The authors believe this to be the largest reported series of surgically treated pediatric CM-I patients and hope that their experience will be of use to others who treat this surgical entity.

Background:In an effort to minimize rod fractures and nonunion in pedicle subtraction osteotomy (PSO) constructs, surgeons have adopted multirod constructs and interbody cages. Anterior column realignment (ACR) with posterior column osteotomies is a minimally invasive alternative to PSO in sagittal balance correction, however, there is a paucity of evidence with respect to rod survival.Methods:Three-dimensional (3D) finite-element-model of a T12-sacrum spine segment was used to compare a 25° PSO at L3 and an ACR with a posterior column osteotomy and 30° hyperlordotic interbody cage at L3–4. The amount of overall T12–S1 lordosis correction was the same for each condition. Each simulation included cobalt chromium alloy primary rods with: (1) PSO; (2) PSO with an interbody cage (IB) at L2–3 (PSO+IB); (3) PSO with accessory (A) rods and IB at L2–3 (PSO+IB+A); (4) PSO with satellite (S) rods and IB at L2–3 (PSO+IB+2S); (5) ACR; 6) ACR with satellite rods (ACR + 2S). A 400 N follower preload was simulated for each condition.Results:PSO condition had the largest rod stress of 286 MPa in flexion. Adding interbody support reduced the rod stress by 15%. The 4-rod constructs further reduced rod stress, with the satellite rod condition facilitating the largest reduction. The rod stress in the ACR+2S was equivalent to the PSO+2S, with 50% reduction in rod stress.Conclusion:The rod stress with an ACR was comparable to a PSO coupled with interbody support. These results suggest an ACR is a viable MIS alternative to a PSO without the need for a large posterior osteotomy.

Increased segmental lumbar lordosis is achievable with hyperlordotic cages after ALL resection. Increased cage height tended to increase the amount of lordosis achieved, although in some cases additional posterior bone resection was required to maximize lordosis. Further studies are needed to evaluate the impact on regional lumbar lordosis.

The MIS-ACR is one of the most technically demanding procedures performed from the lateral transpsoas approach. This procedure has the advantage of maintaining and improving spinal global alignment while minimizing blood loss and excessive tissue dissection. It comes with its own unique set of potentially catastrophic complications and should only be performed by surgeons proficient in both deformity correction and the lateral approach.

OBJECTIVE Minimally invasive lateral lumbar interbody fusion (LLIF) via the retroperitoneal transpsoas approach is a technically demanding procedure with a multitude of potential complications. A relatively unknown complication is the contralateral psoas hematoma. The authors speculate that injury occurs from segmental vessel injury at the time of contralateral annulus release; however, this is not fully understood. In this multicenter retrospective review, the authors report the incidence of this contralateral complication and its neurological sequelae. METHODS This study was a retrospective chart review of all minimally invasive LLIF performed at participating institutions from 2008 to 2014. Exclusion criteria included an underlying diagnosis of trauma or neoplasia as well as lateral corpectomies or anterior column releases. Single-level, multilevel, and stand-alone constructs were included. All patients underwent preoperative MRI. Follow-up was at least 12 months. All complications and clinical outcomes were self-reported by each surgeon. RESULTS There were 3950 lumbar interbody cages placed via the retroperitoneal transpsoas approach, with 7 cases (0.18% incidence) of symptomatic contralateral psoas hematoma, 3 of which required reoperation for hematoma evacuation. Neurological outcome did not improve after reoperation. Reoperation occurred an average of 1 month after the initial operation due to a delay in diagnosis. In 1 case, segmental artery injury was confirmed at the time of surgery; in the others, segmental vessel injury was suspected, although it could not be confirmed. Neurological deficits persisted in 3 patients while the others remained neurologically intact. Two patients were receiving antiplatelet therapy prior to the procedure. CONCLUSIONS The contralateral psoas hematoma is a rare complication suspected to occur from segmental vessel injury during contralateral annulus release. Detailed review of preoperative imaging for aberrant vessel anatomy may prevent injury and subsequent neurological deficit.