The iliac kickstand screw: anatomic CT analysis of screw trajectory and osseous corridor for screw placement

INTRODUCTION

The 'kickstand screw-rod' technique has been recently described for correction of coronal malalignment. This technique utilizes powerful 'construct-to-ilium' distraction between a fixed multi-screw thoracic construct and the ilium, facilitated by a novel 'iliac kickstand screw'. The 'iliac kickstand screw' traverses a previously undescribed osseous corridor in the ilium.

OBJECTIVE

Using a radiographic CT study, the objective is to describe a large osseous corridor within the ilium to accommodate the novel iliac kickstand screw.

METHODS

50 consecutive patients with pelvic CTs at an academic medical center were queried. Simulated iliac kickstand screw trajectories for the left and right hemipelvis were analyzed with 3D visualization software. Maximal screw lengths and dimensions, and trajectories in the osseous corridor were measured.

RESULTS

50 patients' (31 female, 19 male) pelvic CTs were measured with a total of 100 simulated screws. The mean age was 52.4 years and BMI 28.1 ± 7.9. The average length is 119.7 ± 6.6 mm (range 98.7 - 135.3). The narrowest width (maximum potential screw diameter) is 17.8 ± 2.9 mm (coronal) and 20.8 ± 5.3 mm (sagittal). The starting point to the top of the iliac crest is 66.4 mm lateral to midline, and 15.9° caudal in the sagittal and 6.1° lateral in the coronal planes.

CONCLUSIONS

The novel iliac kickstand screw traverses a consistent and large osseous corridor within the ilium. The average simulated screw length is 119.7 mm and maximum potential diameter of 17.8 mm. Starting points relative to the iliac crest are identified.

Treatment of sacroiliac joint laxity-induced coronal imbalance with the kickstand rod technique

BACKGROUND

Considerations of the sacroiliac joint (SIJ) and its role in causing lower back and limb pain have taken a secondary role ever since Mixter and Barr's hallmark article in 1934 on the herniated nucleus pulposus. However, recent literature has highlighted the contribution of sacroiliac joint degeneration in the development of failed back surgery syndrome (FBSS), especially in patients undergoing lumbar or lumbosacral spinal fusion surgeries. Many reports have studied the anatomy, physiology, and clinical significance of the sacroiliac joint, but none have linked its dysfunction with other spinal deformities.

CASE DESCRIPTION

A 63-year-old female with a history of multiple complex instrumented spinal fusions presented to our institution with progressive leftward coronal imbalance despite successful arthrodesis from T3 through S1. She was initially treated with decompression and reimplantation, but adjacent segment disease at the SIJ led to laxity, distal failure, and a worsening coronal deformity. A mechanical fall after her decompression surgery led to a dramatically increased coronal imbalance, which was ultimately treated using Lenke's kickstand rod technique. At 3.5 years follow up, the patient's coronal balance remains stable.

CONCLUSION

Few studies have related SIJ degeneration and laxity with spinal deformity. Our case describes SIJ degeneration that evolved to joint laxity, which ultimately produced a leftward coronal imbalance according to the adjacent segment disease mechanism. Additionally, we describe the use of a kickstand rod to effectively correct the coronal imbalance, reduce pain levels, promote SIJ arthrodesis, and prevent further SIJ-related issues without significant complications over 3 years post-operation.

The "Kickstand Rod" Technique for Coronal Imbalance in Patients With Spinal Deformity: A Case Report With Review of Literature

Coronal imbalance is a type of spinal deformity with deviation from midline in the coronal plane. It is challenging to correct even in the hands of experienced spine surgeons. Many conventional techniques lead to unsuccessful results or complications. However, the incorporation of “kickstand rod” (KR) instrumentation is now understood to provide a more supported coronal correction and improve spinal deformities. Sometimes it can be used to provide additional spinal support in instances where spinal fusion has already occurred. The KR is placed from a posterior approach along the lateral spine from lumbar spine to ilium and exerts distraction forces that counteract misaligned spinal segments. Our objective is to present a clinical case example with a brief review of literature. Herein, we present a case of a 62-year-old male with the development of significant coronal imbalance following his posterior lumbosacral instrumentation and fusion 11 years prior to presentation. KR supplementation to his hardware improved his functional outcome significantly. Further, we provide a literature review of the surgical characteristics, indications, and functional outcomes of KR instrumentation. A term search of “kickstand rod” was performed in PubMed, and relevant English language publications were included. The literature search yielded only six publications. A total of 45 patients across three studies were assessed. A mean postoperative coronal balance magnitude of 26.83 mm was calculated compared to the preoperative coronal magnitude of 64.16 mm. Results also showed only four cases of intraoperative or postoperative complications. Moreover, the presented case reported successful KR implementation without any intraoperative complications. KR instrumentation is a safe and effective technique for coronal imbalance correction. The results show favorable outcomes in terms of coronal adjustment and low complication rates. Nevertheless, we caution the fact that further studies are warranted with long-term follow-ups.

The "kickstand rod" technique for correction of coronal imbalance in patients with adult spinal deformity: initial case series

OBJECTIVE

The objective of this study was to describe and evaluate a new surgical procedure for the correction of coronal imbalance (CI) in adult spinal deformity patients, called the "kickstand rod" technique.

METHODS

The authors analyzed the records of 24 consecutive patients with pediatric and adult spinal deformity and CI treated between July 2015 and October 2017 with a long-segment fusion and a kickstand rod. For the kickstand rod technique, an iliac screw was placed on the ipsilateral side of the trunk shift and connected proximally through a side-by-side domino link to the thoracolumbar junction; this rod was distracted to promote coronal plane balancing. Distraction occurred with the rod on the contralateral side locked in order to preserve sagittal correction. Radiographic and clinical analyses were conducted to evaluate the outcomes and possible complications of the kickstand rod technique.

RESULTS

The mean age of the patients was 55 years (range 14-73 years). Eighteen of the 24 patients were female. CI preoperatively was a mean of 63 mm, and the mean measurement at the final follow-up (mean duration 1.4 years) was 47 mm. There were no neurological, vascular, or implant-related complications in any of the patients. One patient developed wound dehiscence that was successfully treated without implant removal, and one developed proximal junctional kyphosis requiring extension of the construct proximally. One patient also returned to the operating room for excision of a spinous process. There were no complaints about screw prominence, kickstand construct failure, or significant worsening of CI after surgery.

CONCLUSIONS

The kickstand rod technique is safe and effective for the correction of CI in spinal deformity patients. This technique was found to provide marked coronal correction and additional strength to the overall construct without significant adverse consequences.