Relationship between Treatment Choices according to the Modified Osteoporotic Fracture Score and Posttreatment Radiographic Outcomes

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Asian Spine J. 2024;.asj.2023.0319

Publication date (electronic) : 2024 March 8

doi : https://doi.org/10.31616/asj.2023.0319

Shinya Tokunaga¹, Toshiyuki Takahashi¹, Koki Mitani¹, Tomoo Inoue², Ryo Kanematsu¹, Manabu Minami¹, Izumi Suda¹, Sho Nakamura¹, Junya Hanakita¹

¹Spinal Disorders Center, Fujieda Heisei Memorial Hospital, Fujieda, Japan

²Department of Neurosurgery, Saitama Red Cross Hospital, Oomiya, Japan

Corresponding author: Shinya Tokunaga, Spinal Disorders Center, Fujieda Heisei Memorial Hospital, Fujieda city, Shizuoka, Japan, Tel: +81-54-643-1230, Fax: +81-54-643-1289, E-mail: stokunaga129@kuhp.kyoto-u.ac.jp

Received 2023 September 24; Revised 2023 October 30; Accepted 2023 November 13.

Abstract

Introduction

The economic cost and prevalence of osteoporosis are important issues driven by the aging of the general population [1,2]. Moreover, osteoporotic vertebral fractures are a significant cause of morbidity and mortality [3]. Despite the widely used classifications and criteria of treatment recommendations for traumatic vertebral fractures [4,5], no commonly accepted classification has been established.

The Osteoporotic Fracture Working Group (the Spine Section of the German Society of Orthopaedics and Trauma [DGOU]) proposed a new classification for osteoporotic vertebral fractures [6,7]. An osteoporotic fracture (OF) classification-based score for therapeutic decision-making (OF score) has also been developed [6,8]. The clinical validity of the OF score was assessed in the Evaluation of the Osteoporotic Fracture Classification, Treatment Score and Therapy Recommendations study, and treatment according to the OF score-based recommendations was suggested to lead to favorable clinical results [9]. However, the score was further adjusted to increase its compliance. Therefore, a new score for therapeutic decision-making in patients with OF, namely, the modified OF (mOF) score, was established by AO Spine [10].

To assess the clinical utility of the mOF score, the concordance between mOF score-based treatment recommendations and actual treatment decisions among patients receiving nonsurgical therapy, balloon kyphoplasty (BKP), and open surgery was analyzed retrospectively. In addition, pretreatment and posttreatment imaging findings were evaluated in patients treated and not treated according to the mOF score-based treatment recommendations. Moreover, the independence level of the patients in each group after treatment was also assessed.

Materials and Methods

2. Overview of OF classification and mOF score

Tables 1 and 2 present an overview of the OF classification and mOF score [6,7,10]. The mOF score has adapted parameters from the original OF score, with distinct cutoff values for the Visual Analog Scale (VAS) score and health status parameters (VAS score ≥5/<5, health status including American Society of Anesthesiologists [ASA], modified frailty index, and anticoagulation) in contrast to the OF score’s parameters (VAS score ≥4/<4, health status including ASA, body mass index, nursing care, and anticoagulation). Deformity progression was defined as the progression of kyphotic or scoliotic curves by at least 10° on consecutive radiographs. The presence of neurological symptoms was classified into six groups (N0–4, NX) according to the thoracolumbar classification system by AO Spine [4]. Nonsurgical, surgical or nonsurgical, and surgical treatments were recommended for patients with mOF scores of 0–5, 6, and ≥7 points, respectively. Decision-making based on mOF scores in the two cases is shown in Fig. 1.

Table 1

OF classification

Table 2

Modified OF score

Fig. 1

Application of modified osteoporotic fracture (OF) score in two cases. VAS, Visual Analog Scale; ASA, American Society of Anesthesiologists; mFI, modified frailty index.

Results

In total, 487 consecutive patients were diagnosed with a new OF at Fujieda Heisei Memorial Hospital between January 2018 and December 2022. Moreover, 337 patients underwent nonsurgical therapy, 96 underwent BKP, and 52 underwent open surgery. A total of 118 patients underwent further analysis according to the inclusion criteria (Fig. 2). Finally, 57 patients in the nonsurgical group, 48 in the BKP group, and 13 in the open surgery group were evaluated. The open surgery group underwent fixation surgery with or without vertebroplasty, except for one patient who only underwent decompression surgery. The baseline characteristics of the study population are shown in Table 3. The use of antiosteoporotic drugs before fracture and the modified frailty index showed significant differences across the three groups. Notably, the difference in antiosteoporotic drug use between the nonsurgical and BKP groups was significant (p=0.006). The use of antiosteoporotic medication after the fracture was high in all three groups.

Fig. 2

Study flowchart. OF, osteoporotic fracture.

Table 3

Baseline characteristics of the study population

In 100 of 118 patients, the treatment was consistent with the mOF score-based treatment recommendation. Significant differences were found in the scores among patients in the nonsurgical, BKP, and open surgery groups (nonsurgical therapy, 4.7±2.8; BKP, 9.0±2.6; open surgery, 11.2±2.5; p<0.0001) (Fig. 3A). In 14 of 57 patients (Fig. 3B), the mOF scores for the nonsurgical group were above the threshold for surgery recommendation (≥7 points). Of these 14 patients, seven did not wish to undergo surgery, and three did not undergo surgery because of serious general complications. In the BKP group, only four of 48 patients were recommended to undergo nonsurgical treatment according to the mOF scores (Fig. 3C). In the open surgery group, treatment selection was consistent with the mOF score-based treatment recommendations in all patients (Fig. 3D). When 6.5 was used as the cutoff for surgical recommendation, the sensitivity and specificity of the mOF score were 82% (95% confidence interval, 0.74–0.88) and 75% (95% confidence interval, 0.67–0.82), respectively.

Fig. 3

Distribution of cases based on modified osteoporotic fracture (mOF) score. (A) The mOF score value in each treatment group. The distribution of mOF score in nonsurgical therapy group (B), in balloon kyphoplasty (BKP) group (C), and in open surgery group (D).

Then, pretreatment and posttreatment radiographic parameters were compared in patients in the nonsurgical group. On pretreatment plain radiography, patients not treated according to the mOF score-based treatment recommendations (≥7 points) had significantly higher AVBH, MVBH, and LKA than patients with scores below the threshold (p<0.001) (Table 4). Other radiographic parameters were not different in the pretreatment study. Posttreatment image findings also showed that AVBH, MVBH, and LKA were significantly greater in patients not treated according to the mOF score-based treatment recommendation (p<0.001) (Table 4); however, a significant difference in SS was noted (p<0.001). An overview of the posttreatment radiographic parameters is shown in Fig. 4.

Table 4

Radiographic outcomes in patients treated non-surgically

Fig. 4

(A, B) Overview of post-treatment radiographic parameters. AVBH, vertebral body height in the anterior portion; MVBH, vertebral body height in the middle portion; PVBH, vertebral body height in the posterior portion; mOF, modified osteoporotic fracture; LKA, local kyphotic angle; SS, sacral slope.

The levels of independence 6 months after treatment in the three treatment groups are presented in Fig. 5. Approximately 80% of patients were categorized into the good clinical outcome group (groups A and B) across all treatment modalities (nonsurgical therapy, 79%; BKP, 79%; and open surgery, 85%). In the nonsurgical group, 85% of the patients treated in accordance with the mOF score-based treatment recommendation were categorized into the good clinical outcome group, whereas only 69% of the patients not treated in accordance with the mOF score-based treatment recommendation achieved a good clinical outcome. However, no significant difference was found between the two groups (p=0.194).

Fig. 5

Levels of patient independence at 6 months post-treatment. Upper row: patients in nonsurgical therapy, balloon kyphoplasty (BKP), and, open surgery groups. Lower row: patients in two nonsurgical therapy subgroups treated in accordance with modified osteoporotic fracture (mOF) score recommendations (≤6 points) and treated not in accordance with mOF score recommendations (≥7 points).

Discussion

In this study, a significant difference was found in the mOF scores among the three groups, including between the BKP and open surgery groups. This suggests that the mOF score mirrors the invasiveness of the treatment and may indicate the type of surgical intervention required. In a previous study, 75% of the patients received treatment consistent with the OF score-based recommendation [9], whereas 100 of 118 patients (85%) in the present study received treatment consistent with the mOF score-based treatment recommendation. This suggests that the mOF score has higher compliance than the OF score.

In total, 57 of 61 patients (93%) in the BKP and open surgery groups were treated consistently with the mOF score-based decision. In contrast, in 14 of 57 patients who underwent nonsurgical therapy, the actual treatment choice did not match the mOF score-based decision. In the nonsurgical therapy group, patients with treatment choices inconsistent with the mOF score had smaller pretreatment and posttreatment VBH and larger LKA. The posttreatment results suggest that treatment inconsistent with the mOF score-based treatment recommendation leads to greater vertebral body deformity. Furthermore, patients with treatment choices inconsistent with the mOF score-based treatment recommendation had a smaller SS after treatment. The SS reflects the sagittal balance of the spine, and the shape of the thoracolumbar spine can be classified into three types based on the SS according to a previous report [14]: a low SS (<35°) is classified as types 1 and 2, a medium SS (35°–45°) as type 3, and a high SS (>45°) as type 4. Type 3 is the most balanced type, whereas the other types are related to thoracolumbar spine deformation. According to that study, patients treated consistent with the mOF score-based treatment recommendation in the present study were classified as having type 1, 2, or 3 based on the mean and standard deviation of the SS. In contrast, all patients treated inconsistently with the mOF score-based treatment recommendations were classified as having type 1 or 2. This result indicates that patients who received treatment inconsistent with the mOF score-based treatment recommendations had a less well-balanced spine shape than those who received treatment consistent with such recommendations. Thus, our results indicate that treatment selection inconsistent with the mOF score-based treatment recommendations may lead to greater deformity of not only a single vertebra but also of the sagittal balance of the entire spine after treatment.

Moreover, the level of patient independence 6 months after treatment was assessed as a measure of clinical outcome. Approximately 80% of the patients were categorized as having a good clinical outcome, in accordance with a previous report on posttreatment independence after BKP (81%) [13]. This concordance validates the appropriateness of the treatments in the present study compared with the existing literature. In the nonsurgical group, a higher number of patients treated consistent with the mOF score-based treatment recommendations fell into the good clinical outcome category compared with those who were not treated based on these recommendations. However, a significant difference could not be established between the two groups. This lack of significance may be attributed to the limited number of patients with an mOF score of ≥7 points.

This study had several limitations. First, differences between the Japanese osteoporosis diagnostic criteria and the OF score criteria led to the exclusion of many patients. This is because the Japanese guidelines diagnose osteoporosis based on fragility fractures without relying solely on T-scores.

Second, clinical outcome evaluations were based solely on levels of independence 6 months after treatment. Incorporating commonly used patient satisfaction scales, such as the VAS, would provide a more comprehensive assessment. In our evaluation of independence, group D was designated as an indicator of poor outcome based on the developer’s perspective. However, group D is a heterogeneous category potentially encompassing groups A–E, and the overrepresentation of patients in group D might confound the accurate interpretation of treatment outcomes.

Lastly, selection bias was present because of insurance constraints in Japan, which mandate that BKP be performed under general anesthesia. This could exclude patients at a high risk of anesthesia complications. A large-scale prospective study of the mOF score is expected as the next step.

Conclusions

The mOF score may be associated with higher compliance than the OF score. Nearly all patients in the BKP and open surgery groups received treatment consistent with mOF score-based selection, whereas patients in the nonsurgical therapy group who received treatment inconsistent with the mOF score-based treatment recommendation had a greater deformity of the affected vertebrae and a less well-balanced shape of the thoracolumbar spine after treatment. These results suggest that the mOF score is a valid tool for use in clinical practice.

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