The lexicon of multirod constructs in adult spinal deformity: a concise description of when, why, and how

The use of multirod constructs in the setting of adult spinal deformity (ASD) began to prevent rod fracture and pseudarthrosis near the site of pedicle subtraction osteotomies (PSOs) and 3-column osteotomies (3COs). However, there has been unclear and inconsistent nomenclature, both clinically and in the literature, for the various techniques of supplemental rod implantation. In this review the authors aim to provide the first succinct lexicon of multirod constructs available for the treatment of ASD, providing a universal nomenclature and definition for each type of supplementary rod. The primary rod of ASD constructs is the longest rod that typically spans from the bottom of the construct to the upper instrumented vertebrae. The secondary rod is shorter than the primary rod, but is connected directly to pedicle screws, albeit fewer of them, and connects to the primary rod via lateral connectors or cross-linkers. Satellite rods are a 4-rod technique in which 2 rods span only the site of a 3CO via pedicle screws at the levels above and below, and are not connected to the primary rod (hence the term “satellite”). Accessory rods are connected to the primary rods via side connectors and buttress the primary rod in areas of high rod strain, such as at a 3CO or the lumbosacral junction. Delta rods span the site of a 3CO, typically a PSO, and are not contoured to the newly restored lordosis of the spine, thus buttressing the primary rod above and below a 3CO. The kickstand rod itself functions as an additional means of restoring coronal balance and is secured to a newly placed iliac screw on the side of truncal shift and connected to the primary rod; distracting against the kickstand then helps to correct the concavity of a coronal curve. The use of multirod constructs has dramatically increased over the last several years in parallel with the increasing prevalence of ASD correction surgery. However, ambiguity persists both clinically and in the literature regarding the nomenclature of each supplemental rod. This nomenclature of supplemental rods should help unify the lexicon of multirod constructs and generalize their usage in a variety of scientific and clinical scenarios.

Sequential correction technique in degenerative scoliosis with type C coronal imbalance: a comparison with traditional 2-rod technique

OBJECTIVE The aim of this study was to compare the radiographic and clinical outcomes in patients with degenerative scoliosis (DS) with type C coronal imbalance who underwent either a sequential correction technique or a traditional 2-rod technique with a minimum of 2 years of follow-up. METHODS DS patients with type C coronal imbalance undergoing posterior correction surgery from February 2014 to January 2018 were divided into groups by technique: the sequential correction technique (SC group) and the traditional 2-rod technique (TT group). Radiographic parameters, including Cobb angle, coronal balance distance (CBD), global kyphosis (GK), thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT), and sacral slope, were assessed pre- and postoperatively. The SF-36 questionnaire was used to assess quality of life. RESULTS A total of 34 patients were included. Significant postoperative improvement in the Cobb angle of the main curve, CBD, GK, TK, LL, SVA, and PT was found in both groups (p < 0.05). Postoperatively, the coronal balance was type A in 13 patients (92.9%) in the SC group and in 16 patients (80.0%) in the TT group (p = 0.298). In the TT group, 1 patient had deteriorative coronal imbalance immediately postoperatively, and coronal imbalance deteriorated from type A to type C in 2 patients during follow-up. The scores of Physical Functioning, Role-Physical, Bodily Pain, Vitality, Social Functioning, Role-Emotional, and Mental Health were statistically improved postoperatively (p < 0.05) in both groups. Type C coronal imbalance at the last follow-up was associated with a relatively worse quality of life. There were no implant failures during follow-up in the SC group, whereas rod fracture was observed in 3 patients in the TT group. CONCLUSIONS Compared with the traditional 2-rod technique, the sequential correction technique can simplify rod installation procedure, enhance internal instrumentation, and reduce risk of implant failures. The sequential correction technique could be routinely recommended for DS patients with type C coronal imbalance.

Transient fixation of L4 vertebra preserves lumbar motion and function in Lenke Type 5C and 6C scoliosis

This study investigated the efficacy of a novel surgical method that relies on the transient fixation of L4 in Lenke Type 5C and 6C adolescent idiopathic scoliosis. Thirty-six transient surgically treated L4 fixation patients were retrospectively evaluated. The first surgery involved mechanical correction of scoliosis; the lowest instrumented vertebra (LIV) was L4. After an average of 1.3 years (range, 0.3–3.4), the second surgery to remove transient L4 pedicle screws was performed. Radiographic parameters and SRS-22 scores were measured. Cobb’s angle, coronal balance, LIV tilting angle, and LIV coronal disc angle clearly improved after the first surgery (p < 0.01). After the second surgery, the corrected Cobb angle (p = 0.446) and coronal balance were maintained (p = 0.271). Although L3/S1 lumbar lordosis decreased after the first surgery (p < 0.01), after removal of transient L4 pedicle screws, it recovered slightly (p = 0.03). Similarly, the preoperative L3/4 lateral disc mobility eventually recovered after transient L4 screw removal (p < 0.01). The function domain of the SRS-22 showed better scores after removal of transient L4 screws (p = 0.04). L4 transient fixation surgery is beneficial for Lenke Type 5C and 6C scolioses that do not fully satisfy LIV (L3) criteria. It preserves L3/4 disc motion, increases functional outcomes, and maintains spinal correction and coronal balance.

Coronal Compensation Mechanism of Pelvic Obliquity in Patients With Developmental Dysplasia of the Hip

Study Design: Descriptive retrospective study. Objective: DDH is a common lower limb deformity. It has been reported that this deformity can change the sagittal alignment of spine and pelvis. Sacral obliquity (SO) and iliac obliquity (IO) have been proven simple and reliable pelvic-lower limb coronal parameters to evaluate the coronal balance of the pelvis. To study the spine-pelvic coronal compensation mechanism of pelvic obliquity in patients with developmental dysplasia of the hip (DDH). Methods: We collected the data of 110 patients with DDH in our hospital from January 2009 to December 2019, who underwent total hip arthroplasty. We used ICC (Intraclass correlation coefficient) to test the reliability of the measurement result of SO and IO in patients with DDH. A paired t-test was used for the statistical analysis. Results: The intra observer reliability of IO and SO was 0.965 and 0.875 respectively, and the inter observer reliability of IO and SO was 0.887 and 0.889 respectively. The sacroiliac joint and spine can compensate for pelvic obliquity in patients with DDH. We classified the compensatory mechanism into 3 types according to the different imaging performances. Conclusions: The sacroiliac joint has a considerable compensatory ability to ensure coronal balance. We clarified and classified the compensatory mechanism of pelvic obliquity into 3 types. We differentiated the pelvic obliquity in patients with DDH and in those with scoliosis, which is clinical significant to understand the process of development of the disease.

Intra operative assessment of the coronal balance in spinal deformity surgery : a technical note and retrospective study

Obtaining a spine that is well balanced after fusion for scoliotic deformity is primordial for the patients’ quality of life. A simple T-shaped instrument combined with standard intraoperative fluoroscopy can be of great help to evaluate the coronal alignment quickly. The aim of this study was to evaluate if a T-shaped device could predict the postoperative coronal balance. Before finalization of the rod fixation, the balance was checked by verifying the relationship between the T-shaped instrument and the upper instrumented vertebra (UIV), and final adjustments were made to correct the coronal balance. A retrospective study was conducted on 48 patients who underwent surgery to correct scoliotic deformity. Intraoperative and postoperative coronal alignment was measured independently by two observers. The mean intraoperative horizontal offset measured between T-shaped instrument and the center of the UIV was 1,69mm to the right with a standard deviation (SD) of 12,43 mm. On postoperative full spine radiographs, the mean offset between the centra sacral vertical line and the center of the UIV was 2,44mm to the left with a SD of 13,10mm. There is no significant difference in coronal balance between both measurements (p=0,12). With this technique we were able to predict the postoperative coronal balance in all but one patient (97,92%). We conclude that the use of a simple T-shaped instrument can provide adequate intraoperative assessment of coronal balance in correcting scoliotic deformity. Level of evidence : IV – case series

A novel integrated global coronal aligner helps prevent post-operative standing coronal imbalance in adult spinal deformity patients fused to pelvis: technical notes and preliminary results

Background Chieving postoperative coronal balance in adult spinal deformity correction surgeries can be challenging. Even with T square rod technique, there were still some cases with good intraoperative coronal alignment but unsatisfactory post-operative standing coronal imbalance. Thus, the novel techniques to obtain global coronal balance are still in great needs. The purpose of this study was to describe a novel integrated global coronal aligner (IGCA) and evaluate its efficacy on avoidance of post-operative coronal imbalance in adult spinal deformity patients fused to pelvis. Methods A detailed description of IGCA technique was presented. 52 ASD patients fused to pelvis were divided into two groups (IGCA group, n = 27; and non-IGCA group, n = 25) according to whether intraoperative IGCA was used or not. Preoperative demographics and postoperative outcomes were compared. Results There were no significant differences regarding coronal balance difference (CBD) and imbalance/balance ratio between IGCA and non-IGCA groups preoperatively. After surgery, CBD in IGCA group was significantly improved from 24.7 ± 20.3 mm preoperatively to 12.6 ± 6.4 mm postoperatively (t = 3.185 p = 0.004), and imbalance/balance ratio decreased significantly from 55.6% (15/27) preoperatively to 11.1% (3/27) postoperatively (χ2 = 12.000, p = 0.001), while CBD and imbalance/balance ratio in non-IGCA group were not significantly improved. Compared to non-IGCA group, the amount of correction in CBD was significantly larger in IGCA group (t = 3.274, P = 0.002), and imbalance/balance ratio in IGCA group was significantly lowered (χ2 = 8.606 p = 0.003). Further logistic regression analysis revealed IGCA technique was associated with increased odds ratio for postoperative coronal balance (odds ratio: 7.385; 95% confidence interval 1.760–30.980; P = 0.006). Conclusions The novel intraoperative IGCA technique could help improve CBD and reduce imbalance/balance ratio. It could help prevent post-operative coronal imbalance in adult spinal deformity patients fused to pelvis. Level of evidence 3

Different distal fixation anchors in lumbosacral spinal deformities associated with sacral agenesis: which one is better?

OBJECTIVE Sacral agenesis (SA) is a rare congenital malformation of the spine. There has been a paucity of clinical research to investigate the surgical outcome of spinopelvic fixation in these patients. In this study, the authors aimed to evaluate the outcome of different distal fixation anchors in lumbosacral spinal deformities associated with SA and to determine the optimal distal fixation anchor. METHODS Patients with diagnoses of SA and lumbosacral scoliosis undergoing spinopelvic fixation with S1 screws, iliac screws, or S2-alar-iliac (S2AI) screws were analyzed. The main curve, coronal balance distance, and pelvic obliquity were compared at baseline, postoperatively, and during follow-up in three groups. The complications were also recorded. RESULTS A total of 24 patients were included: 8 patients were stratified into group 1 (S1 screws), 9 into group 2 (iliac screws), and 7 into group 3 (S2AI screws). The main curves were well corrected postoperatively (p < 0.05) in all groups. Coronal balance showed a tendency of deterioration during follow-up in patients with S1 screws (from 18.8 mm to 27.0 mm). Regarding pelvic obliquity, patients with both iliac and S2AI screws showed significant correction (from 3.7° to 2.3° and from 3.3° to 1.6°). Implant-related complications were rod breakage in 3 patients and infection in 1 patient in group 2, and no implant-related complications were observed in group 3. There were 3 cases of unilateral S1 pedicle screw misplacement in group 1. CONCLUSIONS Spinopelvic fixation is a safe and effective procedure that can achieve coronal correction in lumbosacral scoliosis associated with SA. Compared with S1 and iliac screws, S2AI screws as distal fixation anchors can achieve a more satisfactory correction with fewer implant-related complications.

Radiological outcomes of the selective spinal fusion for lenke type 5C adolescent idiopathic scoliosis

Objective: To determine the short term radiological outcomes of Lenke type 5C adolescent idiopathic scoliosis in terms of Cobb angle correction and coronal balance after selective posterior segmental spinal instrumentation with pedicle screws. Methods: This retrospective cohort study was conducted in the department of Orthopaedic at tertiary care public hospital of Mumbai, India. The medical records of patients from 17th April 2015 to 29th October 2019 who underwent a selective spinal fusion with pedicle screws for Lenke type-5C adolescent idiopathic scoliosis were reviewed. Preoperative radiographs were evaluated for Cobb angle of the lumbar or thoracolumbar curve as well as a sagittal and lumbar modifier on anteroposterior and lateral standing films. The curve correction, implant density, number of segment fused and coronal balance was assessed on postoperative radiographs. The pre and postoperative comparison of important study variables was done and P-value was calculated with the help of the chi-square test. P-value <0.05 was considered statistically significant. Results: The total number of patients was 34. Majority (94.1%, n=32) were females while only 2(5.9%) were males. The mean age at the time of operation was 14.35±2.19 years (range 8 to 19 years). Mean pre-operative and post-operative Cobb angles were 61.790±13.120 (range 400 to 850) and 10.550±8.710 (range 00 to 300) respectively (P-value 0.00). The mean percentage of curve correction and percentage of fulcrum flexibility was 83.35±13.07 % (range 55% to 100%) and 59.56%±15.07 (range 28.57% to 84.60%) respectively (P value 0.469). Mean implant density and fusion mass was 66.03±7.94% (range 53 to 79%) and 10.32±2.8 (range 7 to 15%) segments respectively. The coronal balance was achieved in all patients. No major complication was noted. Conclusion: Near normal Cobb angle correction and coronal balance was achieved in all patients of Lenke type 5C adolescent idiopathic scoliosis treated with posterior segmental spinal instrumentation utilizing pedicle screws.