Comprehensive classification system for multirod constructs across three-column osteotomies: a reliability study

Abstract

OBJECTIVEIn this study, the authors’ goal was to determine the intra- and interobserver reliability of a new classification system that allows the description of all possible constructs used across three-column osteotomies (3COs) in terms of rod configuration and density.METHODSThirty-five patients with multirod constructs (MRCs) across a 3CO were classified by two spinal surgery fellows according to the new system, and then were reclassified 2 weeks later. Constructs were classified as follows: the number of rods across the osteotomy site followed by a letter corresponding to the type of rod configuration: “M” is for a main rod configuration, defined as a single rod spanning the osteotomy. “L” is for linked rod configurations, defined as 2 rods directly connected to each other at the osteotomy site. “S” is for satellite rod configurations, which were defined as a short rod independent of the main rod with anchors above and below the 3CO. “A” is for accessory rods, defined as an additional rod across the 3CO attached to main rods but not attached to any anchors across the osteotomy site. “I” is for intercalary rod configurations, defined as a rod connecting 2 separate constructs across the 3CO, without the intercalary rod itself attached to any anchors across the osteotomy site. The intra- and interobserver reliability of this classification system was determined.RESULTSA sample estimation for validation assuming two readers and 35 subjects results in a two-sided 95% confidence interval with a width of 0.19 and a kappa value of 0.8 (SD 0.3). The Fleiss kappa coefficient (κ) was used to calculate the degree of agreement between interrater and intraobserver reliability. The interrater kappa coefficient was 0.3, and the intrarater kappa coefficient was 0.63 (good reliability). This scenario represents a high degree of agreement despite a low kappa coefficient. Correct observations by both observers were 34 of 35 and 33 of 35 at both time points. Misclassification was related to difficulty in determining connectors versus anchors.CONCLUSIONSMRCs across 3COs have variable rod configurations. Currently, no classification system or agreement on nomenclature exists to define the configuration of rods across 3COs. The authors present a new, comprehensive MRC classification system with good inter- and intraobserver reliability and a high degree of agreement that allows for a standardized description of MRCs across 3COs.

Effects of Revision Rod Position on Spinal Construct Stability in Lumbar Revision Surgery: A Finite Element Study

“…Clinical results indicated that the DRCm could shorten surgical duration, decrease blood loss, reduce RS-related complications, and generate favorable surgical outcomes compared to those of conventional dual-rod RS ( Tan et al, 2021b ). The SRC has been applied in clinical practice to deal with spinal deformity involving osteotomy and long segment instrumentation and the rescue of previous rod fracture ( Buell et al, 2018 ; Zhu et al, 2018 ; Jung et al, 2019 ; El Dafrawy et al, 2020 ). The reported advantages of the SRC include dispersing the rod stress concentrated at the osteotomy site, enhancing the stability of constructs and reducing the occurrence of PJK ( Hyun et al, 2014 ; Zhu et al, 2018 ; Gelb et al, 2021 ).…”

Presumptive Long Rod Technique (PLRT) for Revision Extension Instrumented Spine Surgery: A Technical Note

“…The comprehensive types for multirod constructs across three column osteotomies as suggested by El dafrawy et al, and can be integrated to increase the strength of construct. Multiple ways of increasing stiffness at high stress regions can also be incorporated with the current PLRT technique to increase strength of construct [21,22]. RES when indicated, requires exposure of the primary construct levels for exchange of implants leading to increased length of surgical incision, operative time, blood loss and perioperative morbidity [23].…”

Multiple-Rod Constructs Do Not Reduce Pseudarthrosis and Rod Fracture After Pedicle Subtraction Osteotomy for Adult Spinal Deformity Correction but Improve Quality of Life

“…to define the different configurations of multiple rods constructs allowing for standardized communication and research or clinical practice 19 . In our study, surgical technique regarding the use of multiple rods corresponded to the precited definition of using in addition to the classical 2 rods, at least one accessory or satellite rod systematically spanning the PSO area or the PSO and lumbosacral junction which consists of connecting the accessory or satellite rod to the main rod with one proximal connector and one distal connector placed just below the S1 screw in order to protect the adjacent area.…”

“…An additional detail is to avoid overloading the proximal part of the construct with multiple rods to avoid proximal overload and PJK. In the classification system for multirod constructs 19 , satellite rods are defined as additional rods attached to anchors with or without an attachment to the main rod construct, therefore, bridging screws heads that went out of line is considered a satellite rod. Accessory rods are not attached to any anchors but to the main rod via connectors.…”