Abstract
To investigate the morphometric data of the lumbar spinous process dimensions in Chinese population. Forty-six adult subjects (22 males, 24 females, age range 26-45 years) were studied using the method of the three dimensional CT reconstruction in our hospital. The following parameters were measured: the distance between two adjacent spinous processes (DB), distance across the two adjacent spinous processes (DA), thickness of central of spinous processes (TC), thickness of the superior margin of spinous processes (TS), thickness of the inferior margin of spinous processes (TI), and height of spinous processes (H). Variance and correlation analysis were conducted for these data. Data met with normal distribution and homogeneity of variance. Similar variation trend of the parameters of lumbar spinous process for male and female was found. DB became shorter gradually from L1-2 to L4-5, and increased at the L5-S1. DA became larger from T12-L1 to L1-2 for male and L2-3 for female, and then became shorter from L1-2 for male and L2-3 for female, respectively. The largest H of male and female were both noted at L3. TS of the adjacent spinous processes were lower than that of TI for male and female. Statistical significance between male and female were found in H, TC, TS, TI (L1, L3 and L4), and DA (except for L4-5). Compared to male, the spinous processes of female were shorter, thinner and lower. These data may be useful for clinical application and the design of interspinous implant in Chinese population.
Keywords: Spinous process, lumbar spine, morphometry, computed tomography reconstruction
Introduction
Lumbar degenerative disc disease (LDDD) is an age-related disease associated with deteriorated discs of lumbar spine, which is one of the causes of low back pain [1]. The symptomatic LDDD can cause magnificent disability and depression to patients, which greatly affect the living quality of them [2]. It is commonly acknowledged that surgical treatment should be considered for late phase of LDDD, or when the traditional conservative treatment has no obvious effect for LDDD. At present, there are many different kinds of surgical procedures for LDDD, and the number is increasing [3,4]. Among the diverse surgical methods performed for LDDD, the fusion surgery has been identified as the “gold standard” for the LDDD surgical treatment, which is the performance of jointing two bones [4]. However, various studies have shown that fusion surgery could promote the presentation of adjacent segment degeneration after surgery because of more motion of the above or below fusion vertebrae and more pressure on the adjacent discs from the fusion site [5,6]. The secondary adjacent segment degeneration may cause pain and disability again, increasing the need for second surgery [7].
Interspinous process implant is a novel surgical procedure known to be minimally invasive due to the simple operating protocol and shortened operating time [8]. Several biomechanical studies have shown that interspinous stabilizing implant could offer non-rigid fixation without affecting adjacent segments significantly and decrease the pressures of anulus and central nucleus [9-11]. Although this surgery procedure presented with many advantages, complications may still occur after surgery, such as implant device migration and spinous fracture [12,13]. Too small size device may lead to the dislocation of implant, while too large size device may result in the breakage of implant. Thus, detailed information of lumbar spinous process morphometry is critically important for the appropriate interspinous process implantation to prevent the post-operative complications [13,14].
Emerging evidence has indicated that the morphometric dimension of spine is diverse in different populations, suggesting racial differences [15-18]. Our previous study has reported the anatomical measurement data of lumbar spinous process on cadavers in Chinese population [19] (in press). In order to confirm our previous data obtained from the cadavers, the present study defined the morphometric dimension of lumbar spinous process in Chinese population by the radiographic measurement on the living subjects. We compared the radiographic data with our previous data from the cadavers. Besides, the gender difference with the data was also analyzed.
Materials and methods
Forty-six patients (24 males and 22 females; average age, 32 ± 3.7 years) with no abnormalities, injures or degeneration in the lumbar spine were enrolled in this study. All human studies were approved by the Hospital Ethics Committee and performed in accordance with the ethical standards. After the informed consent was obtained from all patients, all patients underwent the CT scanner using the 16-slice spiral CT machine (Light Speed, GE Medical System, Waukesha WI, USA). The scanning parameters were tube voltage 80 KV, tube current 50 mA, slice thickness 1.25 mm, slice interval 1.25 mm and beam pitch 1.375:1. Images are reconstructed with slice thickness of 0.625 mm and slice interval of 0.3 mm. The reconstructed CT images were transferred to a remote GE Advantage Workstation, equipped with commercial navigator software (ADW 4.4 version, GE) capable of performing volume rendering (VR) and multiple planar reformatting (MPR) [20]. The following parameters were obtained on the CT radiographs: 1) DB (distance between the two adjacent spinous processes): L1-2, L2-3, L3-4, L4-5 and L5-S1; 2) DA (distance across the two adjacent spinous processes): T12-L1, L1-2, L2-3, L3-4 and L4-5; 3) TC (thickness of central spinous processes); 4) TS and TI (thickness of the superior and the inferior margin of spinous processes); 5) H (the height of spinous processes). The measuring methods are illustrated in Figure 1. Three times were measured for each distance with a single investigator.
Figure 1.
Illustration of measuring parameters. The upper picture: schematic diagram of DA, DB, TS, TI, TC and H. The lower picture: three dimensional reconstruction images of DA, DB, TS, TI, TC and H. DB, distance between the two adjacent spinous processes); DA, distance across the two adjacent spinous processes; TC, thickness of central of spinous processes; TS, thickness of the superior margin of spinous processes; TI, thickness of the inferior margin of spinous processes; H, height of spinous processes.
All data were expressed as mean ± standard deviation and analyzed by SPSS 8.0 software (SPSS Inc, Chicago, Illinois, USA). One-sample Kolmogorov-Smirnov test and one-way ANOVA analysis of variance were used to evaluate the normal distribution and the homogeneity of variance among data in each group. P < 0.05 was considered statistically significant.
Results
CT scanning measurement
One-sample Kolmogorov-Smirnov test confirmed the approximately normal distribution among data in each group, and one-way ANOVA analysis of variance indicated the homogeneity of variance among data in each group. There were no statistical significance among TC and TI of male and TC, TI and H of female by variance analysis, respectively (Table 1).
Table 1.
CT scanning measurement data of lumbar spinous process in males and females
| Items | Male (n = 24) | Female (n = 22) | F value | P value |
|---|---|---|---|---|
| DB | ||||
| L1-2 | 8.26 ± 2.48 (3.60-13.80) | 7.22 ± 2.04 (3.80-10.70) | 1.28 | 0.26 |
| L2-3 | 7.99 ± 2.86 (2.90-13.80) | 7.08 ± 2.19 (2.00-11.20) | 1.46 | 0.23 |
| L3-4 | 7.33 ± 2.51 (2.10-12.30) | 6.96 ± 2.32 (2.70-11.60) | 0.28 | 0.60 |
| L4-5 | 5.66 ± 2.08 (1.00-9.80) | 5.34 ± 1.95 (1.20-8.90) | 0.29 | 0.59 |
| L5-S1 | 5.68 ± 2.22 (1.20-10.30) | 6.52 ± 2.10 (2.40-10.60) | 1.75 | 0.19 |
| DA | ||||
| T12-L1 | 54.91 ± 7.49 (37.60-68.40) | 48.73 ± 6.47 (35.40-62.50) | 8.94 | < 0.01 |
| L1-2 | 60.00 ± 7.80 (43.20-75.40) | 52.10 ± 5.80 (40.20-63.40) | 12.59 | < 0.01 |
| L2-3 | 59.35 ± 6.46 (46.50-72.30) | 52.24 ± 5.41 (40.10-62.80) | 16.37 | < 0.01 |
| L3-4 | 52.22 ± 6.13 (39.60-64.60) | 48.64 ± 5.74 (36.50-61.20) | 4.18 | < 0.05 |
| L4-5 | 47.13 ± 6.16 (36.40-63.20) | 47.10 ± 6.12 (35.20-58.50) | 0.20 | 0.65 |
| H | ||||
| L1 | 20.53 ± 4.03 (13.60-28.90) | 17.49 ± 2.78 (12.30-23.60) | 8.87 | < 0.01 |
| L2 | 21.37 ± 3.66 (14.10-28.50) | 17.44 ± 2.81 (12.70-23.60) | 16.71 | < 0.01 |
| L3 | 21.56 ± 5.38 (8.90-31.40) | 17.67 ± 5.39 (7.60-28.40) | 6.88 | 0.01 |
| L4 | 21.40 ± 6.116 (9.20-33.50) | 17.24 ± 4.98 (8.50-27.60) | 8.72 | < 0.01 |
| L5 | 19.53 ± 4.71 (10.10-31.50) | 15.07 ± 3.95 (7.80-25.60) | 12.51 | < 0.01 |
| TS | ||||
| L2 | 5.40 ± 2.22 (1.90-11.60) | 4.00 ± 0.97 (1.80-6.00) | 7.71 | < 0.01 |
| L3 | 5.73 ± 2.23 (2.30-11.90) | 4.33 ± 1.11 (1.80-6.70) | 7.22 | 0.01 |
| L4 | 6.55 ± 2.19 (2.90-12.60) | 4.56 ± 1.12 (2.00-6.90) | 15.01 | < 0.01 |
| L5 | 7.03 ± 2.13 (3.10-12.40) | 5.12 ± 1.31 (2.60-7.90) | 13.45 | < 0.01 |
| S1 | 6.81 ± 2.15 (2.90-11.80) | 5.00 ± 1.33 (2.60-7.80) | 11.86 | < 0.01 |
| TI | ||||
| L1 | 8.27 ± 2.60 (3.20-13.40) | 6.73 ± 2.05 (3.40-11.20) | 4.95 | 0.03 |
| L2 | 9.24 ± 2.23 (4.90-13.50) | 8.43 ± 2.08 (4.20-12.80) | 0.07 | 0.79 |
| L3 | 9.67 ± 2.37 (5.00-14.90) | 7.40 ± 1.09 (4.20-11.50) | 12.30 | < 0.01 |
| L4 | 9.11 ± 2.35 (4.70-13.50) | 7.13 ± 1.83 (4.00-10.80) | 10.21 | < 0.01 |
| L5 | 8.78 ± 2.81 (3.70-14.10) | 7.95 ± 1.69 (4.80-11.50) | 1.42 | 0.24 |
| TC | 7.75 ± 2.43 (1.80-12.51) | 6.35 ± 2.47 (1.70-11.30) | 3.75 | < 0.05 |
The data were represented as, x̅ ± SD, and the measurement unit was mm. DB, distance between the two adjacent spinous processes); DA, distance across the two adjacent spinous processes; TC, thickness of central of spinous processes; TS, thickness of the superior margin of spinous processes; TI, thickness of the inferior margin of spinous processes; H, height of spinous processes.
The data of DB became shorter gradually from L1-2 (male: 8.26 ± 2.48 mm; female: 7.22 ± 2.04 mm) to L4-5 (male: 5.66 ± 2.08 mm; female: 5.34 ± 2.95 mm) and then increased slightly from L4-5 to L5S1 (male: 5.68 ± 2.22 mm; female: 4.03 ± 2.57 mm). For males, DA increased from T12L1 (54.91 ± 7.49 mm) to L1-2 (60.00 ± 7.80 mm) and then followed by decrease from L1-2 to L4-5 (47.13 ± 6.16 mm). For females, the data of DA increased from T12L1 (48.73 ± 6.47 mm) to L2-3 (52.24 ± 5.41 mm) and then followed by decrease from L2-3 to L4-5 (47.10 ± 6.12 mm). The largest H was noted at L3 (male: 21.56 ± 2.38 mm; female: 17.67 ± 5.39 mm). TS of the adjacent spinous process were lower than that of TI at all levels (Table 1). The parameters of lumbar spinous process of male and female indicated approximately similar variation trend.
Comparison of the lumbar spinous process size between males and females
The comparison of each parameter between male and female are shown in Figure 2. The DB values of females were shorter than that in males except at L5S1 but there was no significant difference (P > 0.05). The values of males in the terms of DA were larger than that in females at all levels, and the significance difference was seen (P < 0.05) except at level of L4-5 (P > 0.05). Analyzing H data, the values in males were significantly higher than that in females at all levels (P < 0.05). In addition, TS in males were significantly thicker than that in females at all levels (P < 0.05). The similar phenomenon was also found in TI, but there was significant difference only at L1 L3 L4 (P < 0.05). For TC, the value of males were larger compared with that in females with significant difference (P < 0.05). The above results suggested that the spinous processes of female were shorter, thinner and lower than that of male.
Figure 2.
Comparison of each parameter of DA, DB, TS, TI, TC and H between male and female. *P < 0.05 female vs. male DB, distance between the two adjacent spinous processes); DA, distance across the two adjacent spinous processes; TC, thickness of central of spinous processes; TS, thickness of the superior margin of spinous processes; TI, thickness of the inferior margin of spinous processes; H, height of spinous processes.
Comparison of the radiographic data and the direct measurement data from our previous study
The CT scanning measurement values and our previous direct measurement values were comparatively similar and the absolute majority of the comparisons showed no significant difference with a few exceptions. For DB, the direct measurement value were significantly less than CT value in males (P = 0.0175), while the same phenomenon was found at L3-4 in female (P = 0.0068). The data of H using the direct method were larger than that using the CT scanning measurement method in males at levels of L3 and L4 (P < 0.05) (Table 2).
Table 2.
Comparison of the radiographic data and our previous direct measurement data
| Direct | measurement | 3D-CTR | measurement | t | P | |||
|---|---|---|---|---|---|---|---|---|
|
|
|
|
||||||
| M | F | M | F | M | F | M | F | |
| DB | ||||||||
| L1-2 | 7.61 ± 2.44 | 7.75 ± 1.65 | 8.26 ± 2.48 | 7.22 ± 2.04 | -0.95 | 0.96 | 0.35 | 0.35 |
| L2-3 | 6.80 ± 2.57 | 7.58 ± 1.94 | 7.99 ± 2.86 | 7.08 ± 2.19 | -0.96 | 0.81 | 0.12 | 0.42 |
| L3-4 | 6.00 ± 2.27 | 5.17 ± 1.87 | 7.33 ± 2.51 | 6.96 ± 2.32 | -2.02 | -2.84 | 0.05 | 0.01 |
| L4-5 | 4.90 ± 2.17 | 5.68 ± 2.62 | 5.66 ± 2.08 | 5.34 ± 1.95 | -1.29 | 0.50 | 0.20 | 0.62 |
| L5-S1 | 4.03 ± 2.57 | 6.49 ± 2.78 | 5.68 ± 2.22 | 6.52 ± 2.10 | -2.56 | -0.04 | 0.02 | 0.97 |
| DA | ||||||||
| T12-L1 | 54.63 ± 6.50 | 49.88 ± 7.33 | 54.91 ± 7.49 | 48.73 ± 6.47 | -0.15 | 0.56 | 0.89 | 0.58 |
| L1-2 | 60.13 ± 6.56 | 52.83 ± 3.90 | 60.00 ± 7.80 | 52.10 ± 5.80 | 0.07 | 0.49 | 0.95 | 0.62 |
| L2-3 | 60.18 ± 6.11 | 53.64 ± 4.38 | 59.35 ± 6.46 | 52.24 ± 5.41 | 0.48 | 0.95 | 0.64 | 0.35 |
| L3-4 | 53.76 ± 6.37 | 45.68 ± 5.31 | 52.22 ± 6.13 | 48.64 ± 5.74 | 0.89 | -1.80 | 0.38 | 0.08 |
| L4-5 | 45.07 ± 5.89 | 49.40 ± 7.05 | 47.13 ± 6.16 | 47.10 ± 6.12 | -1.24 | 1.17 | 0.22 | 0.25 |
| H | ||||||||
| L1 | 21.63 ± 3.28 | 17.08 ± 2.83 | 20.53 ± 4.03 | 17.49 ± 2.78 | 1.10 | -1.03 | 0.28 | 0.31 |
| L2 | 24.09 ± 3.95 | 17.59 ± 3.01 | 21.37 ± 3.66 | 17.44 ± 2.81 | 2.00 | 0.17 | 0.05 | 0.86 |
| L3 | 25.45 ± 5.96 | 18.42 ± 4.98 | 21.56 ± 5.38 | 17.67 ± 5.39 | 2.46 | 0.48 | 0.02 | 0.63 |
| L4 | 25.00 ± 5.03 | 18.71 ± 4.50 | 21.40 ± 6.12 | 17.24 ± 4.98 | 3.35 | 1.04 | 0.02 | 0.31 |
| L5 | 21.41 ± 4.41 | 17.44 ± 3.75 | 19.53 ± 4.71 | 15.07 ± 3.95 | 1.49 | 2.00 | 0.14 | 0.05 |
| TS | ||||||||
| L2 | 5.97 ± 2.11 | 4.39 ± 0.94 | 5.40 ± 2.22 | 4.00 ± 0.97 | 0.95 | 1.37 | 0.35 | 0.18 |
| L3 | 6.12 ± 1.89 | 4.48 ± 1.92 | 5.73 ± 2.23 | 4.33 ± 1.11 | 0.69 | 0.32 | 0.50 | 0.75 |
| L4 | 7.83 ± 2.39 | 6.76 ± 1.64 | 6.55 ± 2.19 | 4.56 ± 1.12 | 2.00 | 5.28 | 0.06 | < 0.01 |
| L5 | 6.97 ± 2.25 | 6.03 ± 1.24 | 7.03 ± 2.13 | 5.12 ± 1.31 | -0.11 | 2.39 | 0.92 | 0.02 |
| S1 | 7.93 ± 2.86 | 6.82 ± 0.96 | 6.81 ± 2.15 | 5.00 ± 1.33 | 1.57 | 5.24 | 0.12 | < 0.01 |
| TI | ||||||||
| L1 | 8.42 ± 1.52 | 6.27 ± 2.01 | 8.27 ± 2.60 | 6.73 ± 2.05 | 0.26 | -0.76 | 0.79 | 0.45 |
| L2 | 9.57 ± 2.63 | 8.26 ± 2.06 | 9.24 ± 2.23 | 8.43 ± 2.08 | 1.48 | -0.28 | 0.63 | 0.78 |
| L3 | 9.64 ± 2.56 | 7.72 ± 1.87 | 9.67 ± 2.37 | 7.40 ± 1.09 | -0.04 | 0.71 | 0.97 | 0.49 |
| L4 | 8.72 ± 2.17 | 7.25 ± 2.40 | 9.11 ± 2.35 | 7.13 ± 1.83 | -0.63 | 0.19 | 0.53 | 0.85 |
| L5 | 8.61 ± 3.11 | 7.40 ± 1.04 | 8.78 ± 2.81 | 7.95 ± 1.69 | -0.21 | -1.31 | 0.84 | 0.20 |
| TC | 7.94 ± 1.90 | 6.18 ± 1.16 | 7.75 ± 2.43 | 6.35 ± 2.47 | 0.38 | -0.29 | 0.75 | 0.77 |
The data were represented as x̅ ± SD, and the measurement unit was mm. 3D-CTR, three dimensional CT reconstruction; DB, distance between the two adjacent spinous processes); DA, distance across the two adjacent spinous processes; TC, thickness of central of spinous processes; TS, thickness of the superior margin of spinous processes; TI, thickness of the inferior margin of spinous processes; H, height of spinous processes.
Discussion
Different kinds of interspinous implant devices have been applied in the treatment of various lumbar spine diseases favorably, such as lumbar neurogenic intermittent claudication, lumbar spinal stenosis and degenerative lumbar spinal diseases [21-24]. At present, it is acknowledged that the instability of the lumbar spine, disappearance of the intervertebral space and the decrease in the area of the spinal canal will occur after traditional laminectomy [25]. And it has been reported that the interspinous implant presents with the increase of the spinal canal area to avoid the secondary symptom of compressing the nerves [21]. The evaluation of the morphometric data of the interspinous process is of great importance to the preoperative preparation of interspinous implantation. The results of our present study showed the special characteristics of the lumbar spinous process dimensions in the subset of Chinese population using radiographic methods. Furthermore, we also found the gender difference in the dimensions of lumbarspinous process region.
In our opinions, there are variations between the data from the cadavers and the real normal data due to the long immersion in the fixed liquid of the specimen, which may affect the physiological state of the bone tissues. Compared with the direct measurement method on cadavers, the three dimensional CT reconstruction method can be more easy to obtain the data close to the physiological state and large quantities of in vitro studies [26,27]. Thus, our present study measured the data of lumbar spinous process on the living subjects using the three dimensional CT reconstruction method (Figure 1). Compared with our previous data on cadavers [19], it was found that the CT scanning measurement values and our previous direct measurement values were comparatively similar and the absolute majority of the comparisons between parameters at different levels showed no significant difference with a few exceptions (Table 2). To our limited knowledge, one potential explanation for this may be due to the difference of subjects and the position during examination. Another reason may be the different methods of measurement. The reconstruction of CT images may be affected by many factors, such as the degree of the removed soft tissues. To sum up, our radiographic data could confirm our previous direct measurement data and provide the more accurate anatomy basis for the clinical application of inspinous implantation.
Ihm et al. has reported the spinous process morphometry in Korean patients using lateral radiographic images [16]. The changing trend of interspinous distance from our data was comparatively similar compared with the Korean data by Ihm and his coworkers. Another report also showed the similar trend [28]. In contrast, Ihm et al. showed that the largest height was at L2, while our data indicated at L3 (Table 1). This phenomenon may suggest racial difference of the lumbar spinous process. In addition, we found the gender difference with the spinous process size: the spinous processes of female were shorter, thinner and lower than that of male (Figure 2). Our finding suggested that the gender difference should be considered in the design of the inspinous implant device.
We would like to discuss some limitations in this study that we are aware of. The number of the subjects was small. The relationship of age with the lumbar spinous process was not considered in this study, because many studies has demonstrated that the size of lumbar spinous process changes with age [16,28]. Therefore, a large quantity of Chinese population should be studied in the future to provide the more accurate measurement data of lumbar spious process. Meanwhile, the factor of age should be taken into consideration in the future study.
In conclusion, our results defined the dimensions of lumbar spinous process in the subset of Chinese population using the three dimensional CT reconstruction method on the living subjects. These data may be useful to design the interspinous implant devices fit for the characteristics of the Chinese population and provide the theoretical anatomy basis for the clinical application of this surgical procedure in a Chinese population. Meanwhile, gender difference should be considered in the design of the inspinous implant device.
Disclosure of conflict of interest
None.
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