118 Review article
A radiographic scoring system to assess healing in congenital pseudarthrosis of the tibia B. Stephens Richards, David Wilkes, Molly Dempsey and Pamela Nurenberg The aim of this study was to determine whether an established radiographic union scoring system for tibial fracture healing (RUST) is reliable when used in neurofibromatosis (NF1) patients with congenital pseudarthrosis of the tibia (CPT) treated by intramedullary fixation. Four individuals reviewed 36 sets of radiographs from 12 NF1 patients with CPT (preoperative, and 6 months and 1 year postoperative). Intraobserver reliability (κ-value 0.89) and interobserver reliability (κ-value 0.76) were high. The modified RUST scoring system is a useful tool when faced with the challenge of postoperative radiographic evaluation of the tibia in NF1 patients with CPT. J Pediatr
Introduction Congenital dysplasia of the tibia is an uncommon pathological entity in which the tibial bone has an exaggerated anterolateral bow. Nearly 50% of individuals affected with this condition have neurofibromatosis. It is not uncommon that patients sustain a pathological fracture in this bone at an early age. When this occurs, spontaneous healing rarely occurs and the fractured ends develop a narrowed, cystic, sclerotic, or resorbed appearance, resulting in the condition commonly known as congenital pseudarthrosis of the tibia (CPT). Operative stabilization is needed and most commonly includes intramedullary rod fixation of the tibia with autogenous bone grafting, followed by cast immobilization. Postoperative healing across the pseudarthrotic site can be difficult to determine radiographically because of the atypical appearance of the fractured tibia in these young patients, the postoperative presence of an intramedullary device, and the potential for limited callus formation along the dystrophic bone. In 2010, an objective radiographic scoring system was introduced for the assessment of healing of fractures of normal tibias in which intramedullary fixation was used [1,2]. This system, known as the radiographic union score for tibial shaft fractures (RUST), examines each of the four cortices seen on two orthogonal radiographic views of the tibia. It assesses both the presence of a bridging callus and the persistence of a fracture line. This scoring system exhibits substantial improvements in reliability compared with previously published scores and produces equally reproducible results among a variety of orthopedic specialties and experience levels. This study was undertaken to determine whether the RUST scoring system is reliable when used to assess 1060-152X Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Orthop B 24:118–122 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. Journal of Pediatric Orthopaedics B 2015, 24:118–122 Keywords: congenital pseudarthrosis of the tibia, neurofibromatosis, radiographic scoring system Department of Orthopaedics, Texas Scottish Rite Hospital for Children, Dallas, Texas, USA Correspondence to B. Stephens Richards, MD, Department of Orthopaedics, Texas Scottish Rite Hospital for Children, Dallas, TX 75219, USA Tel: + 1 214 559 7558; fax: + 1 214 559 7570; e-mail: [email protected]
healing of CPT in patients with neurofibromatosis 1 (NF1).
Materials and methods Radiographs of 12 NF1 patients’ tibias that were affected by congenital pseudarthroses were evaluated by four reviewers (three pediatric radiologists and one pediatric orthopedic surgeon). For each of these 12 patients, anteroposterior (AP) and lateral radiographs from three different time periods were examined: preoperative, 6 months after intramedullary stabilization, and 12 months following intramedullary stabilization. These 36 sets of AP and lateral radiographs were presented in a randomized manner and were evaluated independently by each reviewer. Four weeks later, the sets of radiographs were once again randomized, and each reviewer examined each set again. When these individual evaluations were completed, the data were analyzed for intraobserver and interobserver reliability. Once this was completed, the radiographs were again assessed in a single session attended by all four reviewers in an effort to determine reasonable criteria that qualify the tibias as healed in NF1. This is based on the understanding that tibial cortical contours in young NF1 children can be obscured by eccentrically positioned intramedullary rods. If this occurs, it is not possible to rely on the visualization of all four cortices to determine a healed tibia. The RUST scoring system is shown in Table 1. For each set of radiographs, the four cortices of the tibia were evaluated (anterior, posterior, lateral, medial). Each cortex was assigned a numerical score of 1, 2, or 3. A score of ‘1’ represents the presence of an evident fracture line with no callus formation (Fig. 1). A score of ‘2’ represents the presence of callus, but the fracture line is still visible DOI: 10.1097/BPB.0000000000000141
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of the article is prohibited.
A radiographic scoring system Richards et al. 119
Table 1
Overview of the RUST
Fig. 2 Radiographic criteria
Score per cortex 1 2 3
a
Callus
Fracture line
Absent Present Present
Visible Visible Invisible
RUST, radiographic union scoring system for tibial fracture healing. a The individual cortical scores (anterior, posterior, medial, and lateral) are added to provide a RUST value for a set of radiographs, ranging from 4 (definitely not healed) to 12 (definitely healed).
Fig. 1
cm
IM:1
Score of ‘2’ based on the presence of callus and a visible fracture line.
observed proportion of agreement by correcting for the proportion of agreement that could have occurred by chance alone. Guidelines for strength of agreement indicated with κ-values are shown in (Table 2). This is an Institutional Review Board approved retrospective study.
Results cm
IM: 1
Score of ‘1’ based on the absence of callus and a visible fracture line.
(Fig. 2). A score of ‘3’ represents the presence of a bridging callus or mature bone, and no evidence of a persistent fracture line (Fig. 3). If the intramedullary rod obscured visualization of the cortex on a projection, the affected cortex was assigned a value of ‘1’ (Fig. 4). The minimal total score possible was 4 (no evidence of healing) and the maximum total score possible was 12 (complete healing of all cortices). Intraobserver reliability and interobserver reliability were measured using κ-values. The weighted κ adjusts the
The total numerical score assigned to each sample by the four reviewers using the RUST classification system to assess healing in the NF1 patients with congenital tibial pseudarthrosis is shown in Table 3. When these data were statistically evaluated, the intraobserver κ-value between the two review sessions was 0.89 (range 0.75–0.95), demonstrating almost perfect agreement beyond chance. The interobserver κ-value was calculated twice. For the first review session, the interobserver κ-value was 0.76 (range 0.68–0.84), demonstrating substantial strength of agreement beyond chance. For the second review session, the interobserver κ-value was 0.81 (range 0.74–0.85).
Discussion Treatment of CPT commonly involves intramedullary rod fixation and autogenous bone grafting. The ability to
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of the article is prohibited.
120 Journal of Pediatric Orthopaedics B 2015, Vol 24 No 2
Fig. 3
Fig. 4
cm
IM: 1 cm
Score of ‘3’ based on the presence of callus or a healed cortex and the absence of a fracture line.
IM: 1
The eccentric location of an intramedullary rod at the fracture site may prevent clear visualization of one or more cortices. When this occurs, the measurement of the particular cortex is assigned a value of ‘1’.
accurately assess healing on the radiographs has been challenging in this disorder because of a lack of objective, reliable, and valid scoring systems. As a result, subjective descriptions of healing interpreted from radiographs are often used, such as ‘osseous union’ [3] or ‘evidence of bridging across the transverse tibial cortical defect’ [4]. Johnston [5] reported that radiographic union was considered unequivocal when there were no transverse or longitudinal cortical defects or atrophy and there was remodeling and thickening of the tibial and fibular cortices circumferentially. Any union that did not fulfill these criteria was considered to be equivocal (residual longitudinal or transverse cortical deficiency), although this designation did not necessarily mean that additional treatment was needed or that the outcome was suboptimal. Inan et al. [6] defined radiographic union as a bridging callus across three of four visible cortices on AP and lateral views. In the original studies reporting on the RUST scoring system, the patients did not have dysplastic bones, and the cortices were not obstructed by intramedullary rods, presumably because of the adult-sized tibias. Despite the potential presence of these two issues in young patients with NF1, use of the RUST scoring system resulted in reliable interobserver and intraobserver assessments of
Table 2
Strength of agreement indicated with κ-values
κ-Value
Strength of agreement beyond chance
A radiographic scoring system to assess healing in congenital pseudarthrosis of the tibia B. Stephens Richards, David Wilkes, Molly Dempsey and Pamela Nurenberg The aim of this study was to determine whether an established radiographic union scoring system for tibial fracture healing (RUST) is reliable when used in neurofibromatosis (NF1) patients with congenital pseudarthrosis of the tibia (CPT) treated by intramedullary fixation. Four individuals reviewed 36 sets of radiographs from 12 NF1 patients with CPT (preoperative, and 6 months and 1 year postoperative). Intraobserver reliability (κ-value 0.89) and interobserver reliability (κ-value 0.76) were high. The modified RUST scoring system is a useful tool when faced with the challenge of postoperative radiographic evaluation of the tibia in NF1 patients with CPT. J Pediatr
Introduction Congenital dysplasia of the tibia is an uncommon pathological entity in which the tibial bone has an exaggerated anterolateral bow. Nearly 50% of individuals affected with this condition have neurofibromatosis. It is not uncommon that patients sustain a pathological fracture in this bone at an early age. When this occurs, spontaneous healing rarely occurs and the fractured ends develop a narrowed, cystic, sclerotic, or resorbed appearance, resulting in the condition commonly known as congenital pseudarthrosis of the tibia (CPT). Operative stabilization is needed and most commonly includes intramedullary rod fixation of the tibia with autogenous bone grafting, followed by cast immobilization. Postoperative healing across the pseudarthrotic site can be difficult to determine radiographically because of the atypical appearance of the fractured tibia in these young patients, the postoperative presence of an intramedullary device, and the potential for limited callus formation along the dystrophic bone. In 2010, an objective radiographic scoring system was introduced for the assessment of healing of fractures of normal tibias in which intramedullary fixation was used [1,2]. This system, known as the radiographic union score for tibial shaft fractures (RUST), examines each of the four cortices seen on two orthogonal radiographic views of the tibia. It assesses both the presence of a bridging callus and the persistence of a fracture line. This scoring system exhibits substantial improvements in reliability compared with previously published scores and produces equally reproducible results among a variety of orthopedic specialties and experience levels. This study was undertaken to determine whether the RUST scoring system is reliable when used to assess 1060-152X Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Orthop B 24:118–122 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. Journal of Pediatric Orthopaedics B 2015, 24:118–122 Keywords: congenital pseudarthrosis of the tibia, neurofibromatosis, radiographic scoring system Department of Orthopaedics, Texas Scottish Rite Hospital for Children, Dallas, Texas, USA Correspondence to B. Stephens Richards, MD, Department of Orthopaedics, Texas Scottish Rite Hospital for Children, Dallas, TX 75219, USA Tel: + 1 214 559 7558; fax: + 1 214 559 7570; e-mail: [email protected]
healing of CPT in patients with neurofibromatosis 1 (NF1).
Materials and methods Radiographs of 12 NF1 patients’ tibias that were affected by congenital pseudarthroses were evaluated by four reviewers (three pediatric radiologists and one pediatric orthopedic surgeon). For each of these 12 patients, anteroposterior (AP) and lateral radiographs from three different time periods were examined: preoperative, 6 months after intramedullary stabilization, and 12 months following intramedullary stabilization. These 36 sets of AP and lateral radiographs were presented in a randomized manner and were evaluated independently by each reviewer. Four weeks later, the sets of radiographs were once again randomized, and each reviewer examined each set again. When these individual evaluations were completed, the data were analyzed for intraobserver and interobserver reliability. Once this was completed, the radiographs were again assessed in a single session attended by all four reviewers in an effort to determine reasonable criteria that qualify the tibias as healed in NF1. This is based on the understanding that tibial cortical contours in young NF1 children can be obscured by eccentrically positioned intramedullary rods. If this occurs, it is not possible to rely on the visualization of all four cortices to determine a healed tibia. The RUST scoring system is shown in Table 1. For each set of radiographs, the four cortices of the tibia were evaluated (anterior, posterior, lateral, medial). Each cortex was assigned a numerical score of 1, 2, or 3. A score of ‘1’ represents the presence of an evident fracture line with no callus formation (Fig. 1). A score of ‘2’ represents the presence of callus, but the fracture line is still visible DOI: 10.1097/BPB.0000000000000141
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of the article is prohibited.
A radiographic scoring system Richards et al. 119
Table 1
Overview of the RUST
Fig. 2 Radiographic criteria
Score per cortex 1 2 3
a
Callus
Fracture line
Absent Present Present
Visible Visible Invisible
RUST, radiographic union scoring system for tibial fracture healing. a The individual cortical scores (anterior, posterior, medial, and lateral) are added to provide a RUST value for a set of radiographs, ranging from 4 (definitely not healed) to 12 (definitely healed).
Fig. 1
cm
IM:1
Score of ‘2’ based on the presence of callus and a visible fracture line.
observed proportion of agreement by correcting for the proportion of agreement that could have occurred by chance alone. Guidelines for strength of agreement indicated with κ-values are shown in (Table 2). This is an Institutional Review Board approved retrospective study.
Results cm
IM: 1
Score of ‘1’ based on the absence of callus and a visible fracture line.
(Fig. 2). A score of ‘3’ represents the presence of a bridging callus or mature bone, and no evidence of a persistent fracture line (Fig. 3). If the intramedullary rod obscured visualization of the cortex on a projection, the affected cortex was assigned a value of ‘1’ (Fig. 4). The minimal total score possible was 4 (no evidence of healing) and the maximum total score possible was 12 (complete healing of all cortices). Intraobserver reliability and interobserver reliability were measured using κ-values. The weighted κ adjusts the
The total numerical score assigned to each sample by the four reviewers using the RUST classification system to assess healing in the NF1 patients with congenital tibial pseudarthrosis is shown in Table 3. When these data were statistically evaluated, the intraobserver κ-value between the two review sessions was 0.89 (range 0.75–0.95), demonstrating almost perfect agreement beyond chance. The interobserver κ-value was calculated twice. For the first review session, the interobserver κ-value was 0.76 (range 0.68–0.84), demonstrating substantial strength of agreement beyond chance. For the second review session, the interobserver κ-value was 0.81 (range 0.74–0.85).
Discussion Treatment of CPT commonly involves intramedullary rod fixation and autogenous bone grafting. The ability to
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of the article is prohibited.
120 Journal of Pediatric Orthopaedics B 2015, Vol 24 No 2
Fig. 3
Fig. 4
cm
IM: 1 cm
Score of ‘3’ based on the presence of callus or a healed cortex and the absence of a fracture line.
IM: 1
The eccentric location of an intramedullary rod at the fracture site may prevent clear visualization of one or more cortices. When this occurs, the measurement of the particular cortex is assigned a value of ‘1’.
accurately assess healing on the radiographs has been challenging in this disorder because of a lack of objective, reliable, and valid scoring systems. As a result, subjective descriptions of healing interpreted from radiographs are often used, such as ‘osseous union’ [3] or ‘evidence of bridging across the transverse tibial cortical defect’ [4]. Johnston [5] reported that radiographic union was considered unequivocal when there were no transverse or longitudinal cortical defects or atrophy and there was remodeling and thickening of the tibial and fibular cortices circumferentially. Any union that did not fulfill these criteria was considered to be equivocal (residual longitudinal or transverse cortical deficiency), although this designation did not necessarily mean that additional treatment was needed or that the outcome was suboptimal. Inan et al. [6] defined radiographic union as a bridging callus across three of four visible cortices on AP and lateral views. In the original studies reporting on the RUST scoring system, the patients did not have dysplastic bones, and the cortices were not obstructed by intramedullary rods, presumably because of the adult-sized tibias. Despite the potential presence of these two issues in young patients with NF1, use of the RUST scoring system resulted in reliable interobserver and intraobserver assessments of
Table 2
Strength of agreement indicated with κ-values
κ-Value
Strength of agreement beyond chance
