Effects of Bone Bruise on Patients’ Pain after Acute Knee Trauma
Journal of Orthopedic and Spine Trauma: March 2017, 3 (1); e9547
March 31, 2017
Article Type: Research Article
January 2, 2017
February 7, 2017
March 4, 2017
S. Effects of Bone Bruise on Patients’ Pain after Acute Knee Trauma,
J Orthop Spine Trauma.
Bone bruise is a signal change in marrow that can be the result of edema, bleeding, or trabecular bone fractures. Analysis of the exact location of bone bruise can specify the injury pattern, trace the mechanism of injury, and contribute to a better understanding of the internal structural lesions in knees and concomitant injuries. The current study aimed to find a relationship between occurrence, location, and severity of pain and bone bruise.
The current analytical case study was conducted on 22 patients with the isolated bone bruise associated with acute traumatic knee. The patients were asked to grade the severity of pain according to the visual analogue scale (VAS) from 1 to 10. To calculate the volume of bone bruise by magnetic resonance imaging (MRI), the 3 dimensional vectors A × B × C were used. The image analysis software was employed to determine the intensity of bone bruise in the coronal plane in pixel, and the scale of severity of pain was analyzed statistically by the location of bone bruise.
The mean pain scores among male (n = 20) and female (n = 2) patients were 4.40 ± 1.56 and 7 ± 2.82, respectively. The statistical tests showed no significant relationship between the age of patients and severity of pain (P < 0.05). The results of the current study showed no significant relationship between the location of bone bruise and that of severe pain. The average of bone bruise volume in the patients was 8.12 ± 8.77 cm 2 and the mean score of pain was 4.63 ± 1.78, having a significant relationship with each other. In addition, the mean severity score of bone bruise was 42.47 ± 176.40 pixels and the mean pain score was 4.63 ± 1.78, having a significant correlation with each other (P = 0.03, r = 0.8). The tests showed that the severity of pain increased by increasing the intensity of bone bruise.
According to the findings of the present study, the severity of acute bone edema had the highest effect on increasing the severity of pain.
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Bone bruise is an MRI (magnetic resonance imaging) finding in which the signal change in marrow is the result of traumatic injury to the bone. MRI is a powerful test to detect the injuries undetectable by X-rays and arthroscopy. It is a selective method to detect acute bone injuries when physical examinations are ambiguous (
1). Bone bruise (acute bone edema) is a very common finding in acute knee injury that can be only found by MRI, which is associated with hemorrhage, edema, and microtrabecular fracture, without breaking the adjacent cortical bone. Knee bone bruise is of great importance since it may be the result of acute pain and decreased knee function. Detailed analysis of the location of bone bruise can determine the injury pattern, trace the mechanism of injury, and contribute to a better understanding of the internal structural lesions in knees and concomitant injuries. Anterior cruciate ligament (ACL) and meniscal injuries occur more in the patients with bone bruise than in ones without this traumatic injury ( 2). Association of bone bruise with ACL tear or sprain is well defined and known. It is estimated that 98% of ACL traumatic injuries are associated with bone bruise, which can cause pain and disability after surgery of ACL ( 3).
Bone bruise has negative effects on hyaline cartilage and may later cause injuries in the cartilage and osteoarthritis (
3). Most patients with bone bruise feel better after disappearance of abnormal signals. The time reported for disappearance of these signals ranges from 3 weeks to 2 years. In short, the relationship between bone bruise and pain in knee after trauma is not clear and can be a predetermined finding in some patients. The abnormal signal can last for a long time; while, it may not be the cause of pain in patients ( 4). It is not clearly recognized if bone bruise is the cause of pain and disorders in knee function. Joseph et al. showed that pain decreased 2 weeks after the trauma caused by bone bruise, but the bone bruise symptoms in MRI were in the maximum intensity ( 5). Other studies claimed that bone bruise is a type of stress fracture and causes pain ( 6). As already mentioned, bone bruise is mostly the result of shock and trauma and causes pain and disability in patients. There are few studies on the relationship between isolated bone bruise, type, and severity of pain, and pain relief. Therefore, the current study aimed to find the relationship of occurrence, location, and severity of pain with knee bone bruise. The current prospective study investigated the relationship between bone bruise and clinical presentations, particularly pain, in patients.
The current analytical case study selected 22 patients with isolated bone bruise associated with acute knee trauma and pain referring to the emergency department of trauma center and orthopedic clinic of the same center. The inclusion criteria were age over 18 years and recent knee trauma without previous injury. The exclusion criteria were soft tissue traumas such as ligament, tendon, or meniscus injuries, evidence of bone fracture in X-ray, restricted bent due to previous trauma, knee inflammatory arthritis in the past, and delay in doing MRI test more than 5 days after trauma. The patients were clinically examined for their joint motion and diameter of the knee. Local swelling, effusion, ecchymosis, lacerations, and contusions of the skin and soft tissue crush were evaluated and preliminary X-ray on any fracture was fully investigated. Further, the McMurray and the Apley tests were conducted to examine meniscuses. In addition, the Varus and the Valgus stress tests as well as the Lachman and the Pivot shift tests were performed to examine collateral ligaments and anterior cruciate ligament, respectively. The visual analogous scale (VAS) was prepared and the patients were asked to grade the severity of pain from 1 to 10 and mark the most appropriate picture of pain by eye measuring. They were also asked to mark the location of maximum pain and distribution of pain in their knees. Then, this localization was matched to the knee pattern by the examiner. The injury mechanism described by the patient was recorded and listed with the patient’s name. Then, the MRI results were monthly studied. The A × B × C method developed by Davies et al. was used to calculate the volume of bone bruise in MRI, where A reflected the widest distribution of bone bruise measured in coronal plane, B was the deepest anterior-posterior distribution sagittal plane, and C was the highest distribution of craniocaudal in sagittal plane (
7). The metallographic software Image J was employed to determine the intensity of bone bruise. The intensity of bone bruise in coronal plane was determined in a section with the highest distribution of bone bruise in pixels ( Figure 1), and the information was recorded in another checklist. Pain intensity scale was statistically analyzed by the location of bone bruise, and the intensity and pattern of bone bruise were separately evaluated to recognize any relationship with the severity of pain. The relationship between restrictions on motion and the location of bone bruise was statistically analyzed.
Figure 1. Analyzing the Intensity of Bone Bruise by Image J
The general characteristics of the patients were measured on the qualitative variables of relative frequency and the quantitative variables such as mean, standard deviation (SD), and 95% confidence interval. Independent t test was employed to assess the relationship between the independent and dependent variables if the distribution of data was normal, and ANOVA was employed if there were more than 2 groups. The Pearson and the Spearman correlation coefficient tests were employed to measure the correlation between them. The significance level of 5% was the criterion to decide the relationship between the variables.
Regarding the gender frequency distribution in the patients with bone bruise, 20 patients were male and 2 female. The most painful location was internal femoral condyle (n = 8, 36.4%); while, 10 out of 22 patients (45.5%) had isolated bone bruise in other sites of femoral or tibial condyle.
Table 1 shows the frequency distribution of pain location and location of bone bruise in MRI. The most frequent location of bone bruise was medial femoral condyle.
The mean pain severity score, according to the visual analogous scale (VAS), was 1.87 ± 4.63, ranging from 1 to 9. The average volume of bone bruise, on percentage, was 8.12 ± 8.77 cm
2 and the average intensity of bone bruise, on pixels, was 176.40 ± 42.47.
Table 1. The Frequency Distribution of Pain Location and Location of Bone Bruise in MRI
Anatomic Location Maximum Severity of Pain Location of Bone Bruise in MRI Medial femoral condyle 8 (36.4) 10 (45.5) Lateral femoral condyle 2 (9.1) 2 (9.1) Medial tibial condyle 4 (18.2) 1 (4.5) Lateral tibial condyle 2 (9.1) 2 (9.1) Patella 5 (22.7) 6 (27.3) Metaphyseal femoral distal 1 (4.5) 1 (9.1)
aValues are expressed as No. (%).
The frequency distribution of location of maximum pain according to the location of bone bruise can be observed in
Table 2. Using chi-square test, the P value was measured as 0.1; therefore, there was no statistical relationship between these 2 variables.
Table 2. Frequency Distribution of Location of Maximum Pain According to Location of Bone Bruise
Location of Maximum Pain Location of Bone Bruise Total Medial Femoral Condyle Lateral Femoral Condyle Medial Tibial Condyle Lateral Tibial Condyle Patella Metaphyseal Femoral Distal Medial femoral condyle 6 cases 1 case 0 0 1 case 0 8 75% 12.5% 0 0 12.5% 0 100% Lateral femoral condyle 0 0 0 0 2 cases 0 2 0 0 0 0 100% 0 100% Medial tibial condyle 2 cases 0 1 case 1 case 0 0 4 50% 0 25% 25% 0 0 100% Lateral tibial condyle 1 case 0 0 0 1 case 0 2 50% 0 0 0 50% 0 100% Patella 1 case 1 case 0 0 2 cases 1 case 5 20% 20% 0 0 40% 20 100% Anterior tibia 0 0 0 1 case 0 0 1 case 0 0 0 100% 0 0 100%
One-way ANOVA was employed to assess the relationship between location of bone bruise and severity of pain that gave the P value of 0.1, indicating no statistically significant relationship between them (
Table 3. Mean Pain Severity Score According to Location of Bone Bruise
Location of Bone Bruise Numbers Mean Pain Severity Score Standard Deviation Medial femoral condyle 10 4.7 1.63 Lateral femoral condyle 2 3.5 3.5 Medial tibial condyle 1 9 - Lateral tibial condyle 2 5 0 Patella 6 4.1 1.16 Metaphyseal distal femoral 1 4 -
The mean ± SD of bone bruise volume in the patients was 8.12 ± 8.77 cm
2 and the mean ± SD of pain severity score was 4.63 ± 1.78 cm 2. The Pearson test was employed to evaluate the relationship between bone bruise volume and pain severity; P value of 0.2 showed no statistically significant relationship between the 2 variables.
Average intensity of bone bruise was 176.40 ± 42.47 pixels. Pearson test was performed to evaluate the relationship between intensity of bone bruise and severity of pain that obtained the P value of 0.03, revealing that pain became more severe when the intensity of bone bruise increased and it was a statistically significant relationship (r = 0.8) (
Figure 2. Significant Correlation Between the Intensity of Bone Bruise in MRI and the Intensity of Patients’ Pain
The mean age of the patients in the current study was 34.22 ± 12.93 years and the mean pain severity score calculated by relationship tests was 0.6, indicating no statistically significant relationship between them.
Wilson reported for the first time the undefined changes in bone density in T2 in patients with trauma and pain in knee with normal radiographs (
8), and as increased density may cause an increase in fluid in T2, it was concluded that trauma caused edema in bone. However, confounding factors such as soft tissue trauma, nerve damage, and meniscus and ligaments tear prevented the establishment of a direct relationship between bone edema and symptoms in the patients. Shirakura and Mair studied the knee ligament rupture and concluded that the bone edema was intense; the intensity of edema can be an effective factor in prognosis of knee trauma ( 9).
Illingworth reported the relationship between the volume of edema and meniscus tear in patients with PCL tear and showed that increased volume of trauma can cause an increase in injuries in knee, including acute bone edema (
Li studied the relationship between the knee bone edema and the mediators causing pain, and concluded that there was no direct relationship between the symptoms of pain and knee bone edema intensity. Therefore, there could be other factors causing pain in the knee. There could be also no relationship between the volume of acute edema and the severity of pain. Though the higher volume of acute edema was associated with more injuries such as meniscus tear and ligament injuries, it had no relationship with the individual pain symptoms (
The current study mainly showed the relationship between the intensity of acute edema and the severity of pain in patients. Excluding all confounding factors such as soft tissue trauma, ligament and cartilage trauma, meniscal injuries, isolated acute edema, the current study showed a relationship between the severity of pain and changes in intensity of signals in knee acute edema. Changes in the intensity of signals reflect the fluid accumulation in bone. There was no direct relationship, in the current study, between the factors of volume of acute edema and location of acute edema, while previous studies did not consider the factor of intensity of signal changes. It seems that there was a threshold for the changes in signals to make pain in the cases of acute bone edema, which was not studied in the present paper, but it can explain the discrepancies in the literature on the severity of pain and acute bone edema. More studies should be conducted to determine the threshold of changes in signals contributing to pain.
According to the findings of the present study, the severity of acute bone edema had the highest effect on increasing the severity of pain. There was no correlation between anatomical site bone bruise and severity of pain.