Clinical Imaging 38 (2014) 495–498
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Clinical Imaging journal homepage: http://www.clinicalimaging.org
The association of patellofemoral joint morphology with chondromalacia patella: a quantitative MRI analysis Burcu Kaya Tuna a, Aslıhan Semiz-Oysu a,⁎, Bilhan Pekar b, Yasar Bukte a, Alper Hayirlioglu b a b
Umraniye Training and Research Hospital, Department of Radiology, Istanbul, Turkey Istanbul Medeniyet University, Goztepe Training and Research Hospital, Department of Radiology, Istanbul, Turkey
a r t i c l e
i n f o
Article history: Received 5 September 2013 Received in revised form 3 January 2014 Accepted 16 January 2014 Keywords: Patellofemoral joint Chondromalacia patellae Patellofemoral pain syndrome Magnetic resonance imaging Cartilage
a b s t r a c t The relationship of patellofemoral congruency with chondromalacia patellae (CP) was retrospectively evaluated. Lateral patellar tilt angle (LPTA), sulcus angle (SA), trochlear depth (TD), and patella angle (PA) were measured at 301 knee magnetic resonance images and compared between groups with and without CP. In the CP group, LPTA and TD were significantly low (Pb .01), SA was high (Pb.01), while PA showed no difference (PN.05). The parameters were also compared between groups with mild and severe CP, and no significant difference was found (PN .05). Our results demonstrate that patellar tilt and trochlear dysplasia are related to the presence but not the degree of CP. © 2014 Elsevier Inc. All rights reserved.
1. Introduction Patellofemoral pain syndrome, a common orthopedic problem causing considerable disability, is often caused by chondromalacia patellae [1–3]. The disruption of patellar cartilage may occur due to patellofemoral morphological variations or anatomical incongruence, which causes distress on the joint and exerts abnormal mechanical force on articular surfaces [3,4]. For this reason, evaluation of morphological features of the patellofemoral joint plays an important role in diagnosis and treatment of patellar chondromalacia. Evaluation of patellofemoral incongruency and its relation to chondromalacia has traditionally been studied by conventional radiography in which direct visualization of patellar cartilage is not possible [4–7]. Although several methods have been described such as lateral radiographies or tangential views at various degrees of knee flexion, it is difficult to establish a diagnosis using tangential radiographies [8,9]. The measurements described in conventional radiography are inadequate in reflecting exact patellar alignment, and normal measurements of congruency angles are inconsistent between different studies [4–6,10]. Additionally, in evaluation of patellofemoral relationship, radiographic studies remain unable to visualize the joint in transverse view at extension, which is important to reveal exact patellofemoral morphology, since quadriceps femoris muscle is
⁎ Corresponding author. Adem Yavuz Cad. No:1, Umraniye Egitim ve Arastirma Hastanesi, Radyoloji Klinigi, Umraniye, 34764, Istanbul, TURKEY. Tel.: +90 216 632 1818. E-mail address: [email protected] (A. Semiz-Oysu). http://dx.doi.org/10.1016/j.clinimag.2014.01.012 0899-7071/© 2014 Elsevier Inc. All rights reserved.
stronger than its antagonists, and the patella may appear as if dislocated at flexion views [7,8]. Arthroscopy is the most efficient technique in determination of patellar position; presence of chondromalacia; and, if present, location and size of cartilage lesions. On the other hand, the invasive nature of arthroscopy necessitates use of a noninvasive method essential in diagnosis [11,12]. Cross-sectional imaging modalities are the most sensitive noninvasive techniques in demonstrating patellar and trochlear morphology [9,13,14]. Magnetic resonance imaging (MRI) is currently the imaging modality of choice in the noninvasive diagnosis of chondromalacia patellae [12,15,16]. The advantages of MRI over computed tomography lies in its capability of multiplanar, high-resolution imaging of osseous, chondral, and soft tissue lesions without using ionizing radiation [12,17]. MRI images cartilage directly and depicts the relationship between the patella and the trochlea in the position imaged, usually near fully extended [17,18]. In the literature, few studies have evaluated the patellofemoral joint morphology using MRI and its relation to chondromalacia patellae; however, the results of these studies vary, and the relation is not yet well documented [17–19]. In this study, we aimed to investigate the relationship of patellofemoral joint morphology with chondromalacia patellae. For evaluation of patellofemoral morphology, the sulcus angle, the trochlear depth, and the patella angle were measured, and the lateral patellar tilt angle was used to evaluate patellar tilt. To the best of our knowledge, our series is the largest series in the literature analyzing the patellofemoral congruency and its relation to the presence and degree of patellar chondromalacia.
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2. Materials and methods Patients who underwent MRI, in a period of 5 months, with the indication of knee pain were included in the study. The exclusion criteria were a history of knee surgery, arthroscopy, or knee fracture and an imaging finding of a dislocation, trauma, or effusion. Patients who had motion artifacts at MRI were also excluded. MRI images of a total of 301 patients were retrospectively analyzed. The study protocol was approved by the institutional review board, and informed consent was waived. MRI was performed on a 1.5-T system (Signa Excite HD; GE Healthcare, Milwaukee, WI, USA) at supine position with the knee in full extension. Sagittal fast spin-echo, T1-weighted [repetition time (TR)/echo time (TE): 700/11, matrix: 256×192, field of view (FOV): 16×16, slice thickness: 3 mm]; sagittal fat-saturated, proton-density-weighted (TR/TE: 4100/30, matrix: 256×192, FOV: 16×16, slice thickness: 3 mm); coronal fatsaturated, proton-density-weighted (TR/TE: 2300/34, matrix: 256×, FOV: 16×16, slice thickness: 3 mm); and axial fat-saturated, proton-density-weighted (TR/TE: 2800/46, matrix: 256×192, FOV: 16×16, slice thickness: 4 mm) sequences were obtained. MRIs were analyzed on a workstation (Leonardo, Siemens, Erlangen, Germany) by two radiologists in consensus, and measurements were made using electronic calipers. On axial plane images, the lateral patellar tilt angle (the angle between the line parallel to the patellar lateral facet and the line connecting the most posterior parts of femoral condyles), the sulcus angle (the angle between the lines parallel to the medial and lateral trochlear facets), the trochlear depth (the distance from the line connecting the most anterior parts of the medial and lateral femoral trochlear facets and the deepest part of the trochlear groove), and the patella angle (the angle between the lines parallel to the medial and lateral patellar facets) were measured to evaluate patellar alignment (Figs. 1 and 2). The lateral patellar tilt
angle and patella angle were measured at the middle axial slice of patella. MRIs were reviewed to detect the cases with patellar chondral lesions, and the patients were divided into two groups according to the absence or presence of chondromalacia patellae. The chondral lesions were graded using the International Cartilage Repair Society Classification System (Table 1) [20]. In patients with more than one chondral lesion, the most severe defect was used for grading [18]. Cases with chondromalacia patellae were further divided into two groups as mild (types 1 and 2) and severe (types 3 and 4) chondromalacia, and measurements were compared between two groups. Statistical analyses were performed using Number Cruncher Statistical System 2007 and the Power Analysis and Sample Size 2008 Statistical Software (Kaysville, UT, USA). The χ2 test or Student’s t test was used, where appropriate, and Pb .05 was used to determine statistical significance. 3. Results The patients’ ages ranged between 15 and 82 (mean: 46), including 179 women and 122 men. Chondromalacia patella was found in 145 (48%) of 301 cases, while 156 (52%) patients had normal patellar cartilage. Chondromalacia was mild (type 1 or 2) in 72 (49.5%) and severe (type 3 or 4) in 73 (50.5%) cases. The mean lateral patellar tilt angle was measured to be 10.08°± 4.34° in the chondromalacia group, while it was measured as 16.97°± 3.55° in the group without chondromalacia. Also, in the groups with or without chondromalacia patellae, the mean sulcus angles were 147.10° ±7.29° and 134.61°±6.47°, respectively. In patients without chondromalacia, the mean trochlear depth was measured to be 4.81± 0.96 mm, while in those with chondromalacia, the mean trochlear depth was 3.14±0.79 mm. The lateral patellar tilt angles and the
Fig. 1. Measurement of lateral patellar tilt angle (A), sulcus angle (B), trochlear depth (C), and patella angle (D) in a patient with mild chondromalacia.
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Fig. 2. Measurement of lateral patellar tilt angle (A), sulcus angle (B), trochlear depth (C), and patella angle (D) in a patient with severe chondromalacia.
trochlear depths of the chondromalacia group were significantly lower than those of the normal group (Pb.01), while the sulcus angles were significantly higher in the chondromalacia group (Pb .01). The mean patella angle was found to be 125.23°±8.68° in the chondromalacia group, while it was measured as 124.85°±7.01° in the group without chondromalacia. No statistically significant difference was found in patella angles between groups with and without chondromalacia (PN .05). The measurements of lateral patellar tilt angle, sulcus angle, trochlear depth, and patella angle are summarized in Table 2. The lateral patellar tilt angle, the sulcus angle, the trochlear depth, and the patella angle measurements were also compared between groups with mild (type 1 or 2) and severe (type 3 or 4) chondromalacia. No significant difference was found between the two groups, and the measurements are summarized in Table 3 (PN .05).
4. Discussion Femoral trochlear dysplasia may restrict patellofemoral joint stability and cause patellofemoral malalignment, patellar instability, patellar dislocation, and finally loss of patellofemoral cartilage [21].
In trochlear dysplasia, a shallow trochlear groove is related to patellar instability, and the sulcus angle reflects the degree of trochlear dysplasia [22]. Previously, in radiographic studies, a correlation between a wide sulcus angle and chondromalacia patellae was documented [5,6,10]. However, MRI studies evaluating trochlear dysplasia and its relation to chondromalacia are scarce, and their results are inconsistent [17–19]. Endo et al. failed to demonstrate a correlation between the depth of trochlea and chondromalacia patellae [19]. On the contrary, in a different MRI study, both the trochlear depth and the sulcus angle were reported to be associated with severe cartilage defects in a limited number of patients younger than 40 years of age [18]. Another study revealed no significant association between the sulcus angle and patellofemoral cartilage lesions; however, the sulcus depth was reported to be associated with cartilage lesions, and it was concluded that femoral trochlea with a shallow groove could increase the risk of chondromalacia patellae [17]. In an osteoarthritic group of patients, increased medial and lateral cartilage disruption in knees with increased sulcus angle was reported, and the wide sulcus was blamed to increase the pressure on patellofemoral articular surfaces and predispose to cartilage loss [23]. Our study showed that, in patients with chondromalacia patellae, the sulcus angle is increased, while trochlear Table 2 The distribution of parameters among normal and chondromalacia patella groups
Table 1 International Cartilage Repair Society Classification System Cartilage defect Normal Grade 0 Mild defect Grade 1 Grade 2 Severe defect Grade 3 Grade 4
MR findings Normal-appearing cartilage Normal contour with abnormal increased signal Defect b50% of the cartilage thickness Defect N50% of the cartilage thickness Defect extends to or into the subchondral bone
P value⁎
Patient groups
Lateral patellar tilt angle Sulcus angle Trochlear depth Patella angle ⁎ Student's t test. ⁎⁎ Pb.01.
Normal
Chondromalacia
Mean±S.D.
Mean±S.D.
16.97±3.55
10.08±4.34
.001⁎⁎
134.61±6.47 4.81±0.96 124.85±7.01
147.10±7.29 3.14±0.79 125.23±8.68
.001⁎⁎ .001⁎⁎ .674
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Table 3 The distribution of parameters among groups with mild and severe chondromalacia patella P value⁎
Chondromalacia
Lateral patellar tilt angle Sulcus angle Trochlear depth Patella angle
Mild (types 1 and 2) (n=72)
Severe (types 3 and 4) (n=73)
Mean±S.D.
Mean±S.D.
9.76±3.54
10.39±5.01
.600
147.33±7.12 3.12±0.82
146.87±7.51 3.17±0.77
.916 .947
125.73±10.05
124.73±7.10
.947
⁎ Student's t test.
depth is decreased (Pb .01). These findings point out that, in individuals with dysplastic, i.e., more shallow, trochleas, an increased number of patellofemoral cartilage lesions may occur. Abnormal position of the patella in the femoral trochlear groove is also reported to play a role in the pathogenesis of chondromalacia patellae [2,24]. For radiological analysis of patellar tilt, several different imaging techniques and angle measurements have been described [4,24,25]. The lateral patellar tilt angle represents the angle of patellar inclination, which helps to evaluate the lateral stabilizing mechanism of patella [23]. As the lateral inclination of patella increases, the lateral patellar tilt angle decreases [23]. The patellar tilt has been correlated with patellofemoral joint disease radiographically [2]. However, by radiography, the patellofemoral cartilage cannot be assessed directly, and it is not possible to obtain tangential views at full extension of the knee. In studies using MRI, the measurement of the lateral patellar tilt angle at full extension is found to be more sensitive in determination of patellofemoral instability than at flexion [17,25,26]. In a study evaluating patients with osteoarthritis, the lateral patellar tilt angle was reported to be negatively associated with cartilage loss [23]. Yang et al. have found that lateral patellar displacement is associated with patellofemoral cartilage lesions, but the lateral patellar tilt angle was not measured in that study [17]. Our search of the literature revealed no MRI study investigating the relationship of the lateral patellar tilt with chondromalacia patellae. We have demonstrated that the lateral patellar tilt angle is decreased—therefore, patellar tilt is increased—in patients with chondromalacia patellae (Pb.01). In our study, patella angle was also studied, and no significant difference was found between chondromalacia and normal groups (PN .05). This finding was similar in previous studies [17,19]. The relationship of patellofemoral incongruency and the degree of chondromalacia has also been of concern. Ali et al. compared the measurements of each of the mild and severe chondromalacia groups with the control group and found no significant difference between patients with mild chondromalacia and normal group (PN .05). However, they reported statistically significant difference between patients with severe chondromalacia and patients with no chondromalacia in terms of sulcus angle, trochlear depth,, and lateral trochlear inclination angles in a limited number of patients (Pb.01). In our study, chondromalacia patients were also divided into two groups as mild (types 1 and 2) and severe (types 3 and 4). The same measurements were compared between these groups, and no statistically significant difference was found (PN.05). Our results reflect that patellar tilt and morphological properties of trochlea are related to the presence of chondromalacia but not its degree. We have recognized some limitations of our study. First, the diagnosis and grading of chondromalacia were made by MRI but not correlated to arthroscopic findings. It was previously reported that early cartilage changes observed at arthroscopy were not detected by MRI; therefore, in our study, early cartilage lesions might have been interpreted as normal [16]. Additionally, since this was a retrospective study, the routine sequences were used for evaluation instead of
more specific special sequences for cartilage which also might have obscured mild cartilage lesions. 5. Conclusion In patients with chondromalacia patellae, the lateral patellar tilt angle is found to be decreased, and therefore, patellar tilt is increased. Also, patients with patellar chondromalacia show significantly increased sulcus angle and decreased trochlear depth; therefore, patellofemoral congruency is disrupted. Therefore, the morphological variations analyzed in this study, i.e., lateral patellar tilt and trochlear dysplasia, may predispose to cartilage lesions. Our results suggest that patellar tilt and morphological properties of trochlea are related to the presence of chondromalacia but not its degree. References [1] Endo Y, Stein BE, Potter HG. Radiologic assessment of patellofemoral pain in the athlete. Sports Health 2011;3:195–210. [2] Hunter DJ, Zhang YQ, Niu JB, et al. Patella malalignment, pain and patellofemoral progression: the Health ABC Study. Osteoarthritis Cartilage 2007;15:1120–7. [3] Tanamas SK, Teichtahl AJ, Wluka AE, et al. The associations between indices of patellofemoral geometry and knee pain and patella cartilage volume: a crosssectional study. BMC Musculoskelet Disord 2010;11:87. http://dx.doi. org/10.1186/1471-2474-11-87. [4] Grelsamer RP, Bazos AN, Proctor CS. Radiographic analysis of patellar tilt. J Bone Joint Surg Br 1993;75:822–4. [5] Dowd GS, Bentley G. Radiographic assessment in patellar instability and chondromalacia patellae. J Bone Joint Surg Br 1986;68:297–300. [6] Aglietti P, Insall JN, Cerulli G. Patellar pain and incongruence. I: measurements of incongruence. Clin Orthop Relat Res 1983;176:217–24. [7] Carson WG, James SL, Larson RL, Singer KM, Winternitz WW. Patellofemoral disorders: physical and radiographic evaluation. Part II: radiographic examination. Clin Orthop Relat Res 1984;185:178–86. [8] Muhle C, Brossmann J, Heller M. Kinematic CT and MR imaging of the patellofemoral joint. Eur Radiol 1999;9:508–18. [9] Hayes CW, Conway WF. Evaluation of articular cartilage: radiographic and crosssectional imaging techniques. Radiographics 1992;12:409–28. [10] Davies AP, Costa ML, Shepstone L, Glasgow MM, Donell S. The sulcus angle and malalignment of the extensor mechanism of the knee. J Bone Joint Surg Br 2000;82:1162–6. [11] Leslie IJ, Bentley G. Arthroscopy in the diagnosis of chondromalacia patellae. Ann Rheum Dis 1978;37:540–7. [12] Baysal O, Baysal T, Alkan A, Altay Z, Yologlu S. Comparison of MRI graded cartilage and MRI based volume measurement in knee osteoarthritis. Swiss Med Wkly 2004;134:283–8. [13] Disler DG, Recht MP, McCauley TR. MR imaging of articular cartilage. Skeletal Radiol 2000;29:367–77. [14] McCauley TR, Recht MP, Disler DG. Clinical imaging of articular cartilage in the knee. Semin Musculoskelet Radiol 2001;5:293–304. [15] Crema MD, Roemer FW, Marra MD, et al. Articular cartilage in the knee: current MR imaging techniques and applications in clinical practice and research. Radiographics 2011;31:37–61. [16] Pihlajamäki HK, Kuikka PI, Leppänen VV, Kiuru MJ, Mattila VM. Reliability of clinical findings and magnetic resonance imaging for the diagnosis of chondromalacia patellae. J Bone Joint Surg Am 2010;92:927–34. [17] Yang B, Tan H, Yang L, Dai G, Guo B. Correlating anatomy and congruence of the patellofemoral joint with cartilage lesions. Orthopedics 2009;32:20. [18] Ali SA, Helmer R, Terk MR. Analysis of the patellofemoral region on MRI: association of abnormal trochlear morphology with severe cartilage defects. AJR Am J Roentgenol 2010;194:721–7. [19] Endo Y, Schweitzer ME, Bordalo-Rodrigues M, Rokito AS, Babb JS. MRI quantitative morphologic analysis of patellofemoral region: lack of correlation with chondromalacia patellae at surgery. AJR Am J Roentgenol 2007;189:1165–8. [20] Brittberg M, Winalski CS. Evaluation of cartilage injuries and repair. J Bone Joint Surg Am 2003;85-A(Suppl 2):58–69. [21] Rebolledo BJ, Nam D, Cross MB, Green DW, Sculco TP. Familial association of femoral trochlear dysplasia with recurrent bilateral patellar dislocation. Orthopedics 2012;35:e574–9. [22] Pfirrmann CW, Zanetti M, Romero J, Hodler J. Femoral trochlear dysplasia: MR findings. Radiology 2000;216:858–64. [23] Kalichman L, Zhang Y, Niu J, et al. The association between patellar alignment and patellofemoral joint osteoarthritis features—an MRI study. Rheumatology (Oxford) 2007;46:1303–8. [24] Fulkerson JP, Shea KP. Disorders of patellofemoral alignment. J Bone Joint Surg Am 1990;72:1424–9. [25] Kujala UM, Osterman K, Kormano M, Komu M, Schlenzka D. Patellar motion analyzed by magnetic resonance imaging. Acta Orthop Scand 1989;60:13–6. [26] Brossmann J, Muhle C, Schröder C, et al. Patellar tracking patterns during active and passive knee extension: evaluation with motion-triggered cine MR imaging. Radiology 1993;187:205–12.
Contents lists available at ScienceDirect
Clinical Imaging journal homepage: http://www.clinicalimaging.org
The association of patellofemoral joint morphology with chondromalacia patella: a quantitative MRI analysis Burcu Kaya Tuna a, Aslıhan Semiz-Oysu a,⁎, Bilhan Pekar b, Yasar Bukte a, Alper Hayirlioglu b a b
Umraniye Training and Research Hospital, Department of Radiology, Istanbul, Turkey Istanbul Medeniyet University, Goztepe Training and Research Hospital, Department of Radiology, Istanbul, Turkey
a r t i c l e
i n f o
Article history: Received 5 September 2013 Received in revised form 3 January 2014 Accepted 16 January 2014 Keywords: Patellofemoral joint Chondromalacia patellae Patellofemoral pain syndrome Magnetic resonance imaging Cartilage
a b s t r a c t The relationship of patellofemoral congruency with chondromalacia patellae (CP) was retrospectively evaluated. Lateral patellar tilt angle (LPTA), sulcus angle (SA), trochlear depth (TD), and patella angle (PA) were measured at 301 knee magnetic resonance images and compared between groups with and without CP. In the CP group, LPTA and TD were significantly low (Pb .01), SA was high (Pb.01), while PA showed no difference (PN.05). The parameters were also compared between groups with mild and severe CP, and no significant difference was found (PN .05). Our results demonstrate that patellar tilt and trochlear dysplasia are related to the presence but not the degree of CP. © 2014 Elsevier Inc. All rights reserved.
1. Introduction Patellofemoral pain syndrome, a common orthopedic problem causing considerable disability, is often caused by chondromalacia patellae [1–3]. The disruption of patellar cartilage may occur due to patellofemoral morphological variations or anatomical incongruence, which causes distress on the joint and exerts abnormal mechanical force on articular surfaces [3,4]. For this reason, evaluation of morphological features of the patellofemoral joint plays an important role in diagnosis and treatment of patellar chondromalacia. Evaluation of patellofemoral incongruency and its relation to chondromalacia has traditionally been studied by conventional radiography in which direct visualization of patellar cartilage is not possible [4–7]. Although several methods have been described such as lateral radiographies or tangential views at various degrees of knee flexion, it is difficult to establish a diagnosis using tangential radiographies [8,9]. The measurements described in conventional radiography are inadequate in reflecting exact patellar alignment, and normal measurements of congruency angles are inconsistent between different studies [4–6,10]. Additionally, in evaluation of patellofemoral relationship, radiographic studies remain unable to visualize the joint in transverse view at extension, which is important to reveal exact patellofemoral morphology, since quadriceps femoris muscle is
⁎ Corresponding author. Adem Yavuz Cad. No:1, Umraniye Egitim ve Arastirma Hastanesi, Radyoloji Klinigi, Umraniye, 34764, Istanbul, TURKEY. Tel.: +90 216 632 1818. E-mail address: [email protected] (A. Semiz-Oysu). http://dx.doi.org/10.1016/j.clinimag.2014.01.012 0899-7071/© 2014 Elsevier Inc. All rights reserved.
stronger than its antagonists, and the patella may appear as if dislocated at flexion views [7,8]. Arthroscopy is the most efficient technique in determination of patellar position; presence of chondromalacia; and, if present, location and size of cartilage lesions. On the other hand, the invasive nature of arthroscopy necessitates use of a noninvasive method essential in diagnosis [11,12]. Cross-sectional imaging modalities are the most sensitive noninvasive techniques in demonstrating patellar and trochlear morphology [9,13,14]. Magnetic resonance imaging (MRI) is currently the imaging modality of choice in the noninvasive diagnosis of chondromalacia patellae [12,15,16]. The advantages of MRI over computed tomography lies in its capability of multiplanar, high-resolution imaging of osseous, chondral, and soft tissue lesions without using ionizing radiation [12,17]. MRI images cartilage directly and depicts the relationship between the patella and the trochlea in the position imaged, usually near fully extended [17,18]. In the literature, few studies have evaluated the patellofemoral joint morphology using MRI and its relation to chondromalacia patellae; however, the results of these studies vary, and the relation is not yet well documented [17–19]. In this study, we aimed to investigate the relationship of patellofemoral joint morphology with chondromalacia patellae. For evaluation of patellofemoral morphology, the sulcus angle, the trochlear depth, and the patella angle were measured, and the lateral patellar tilt angle was used to evaluate patellar tilt. To the best of our knowledge, our series is the largest series in the literature analyzing the patellofemoral congruency and its relation to the presence and degree of patellar chondromalacia.
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B.K. Tuna et al. / Clinical Imaging 38 (2014) 495–498
2. Materials and methods Patients who underwent MRI, in a period of 5 months, with the indication of knee pain were included in the study. The exclusion criteria were a history of knee surgery, arthroscopy, or knee fracture and an imaging finding of a dislocation, trauma, or effusion. Patients who had motion artifacts at MRI were also excluded. MRI images of a total of 301 patients were retrospectively analyzed. The study protocol was approved by the institutional review board, and informed consent was waived. MRI was performed on a 1.5-T system (Signa Excite HD; GE Healthcare, Milwaukee, WI, USA) at supine position with the knee in full extension. Sagittal fast spin-echo, T1-weighted [repetition time (TR)/echo time (TE): 700/11, matrix: 256×192, field of view (FOV): 16×16, slice thickness: 3 mm]; sagittal fat-saturated, proton-density-weighted (TR/TE: 4100/30, matrix: 256×192, FOV: 16×16, slice thickness: 3 mm); coronal fatsaturated, proton-density-weighted (TR/TE: 2300/34, matrix: 256×, FOV: 16×16, slice thickness: 3 mm); and axial fat-saturated, proton-density-weighted (TR/TE: 2800/46, matrix: 256×192, FOV: 16×16, slice thickness: 4 mm) sequences were obtained. MRIs were analyzed on a workstation (Leonardo, Siemens, Erlangen, Germany) by two radiologists in consensus, and measurements were made using electronic calipers. On axial plane images, the lateral patellar tilt angle (the angle between the line parallel to the patellar lateral facet and the line connecting the most posterior parts of femoral condyles), the sulcus angle (the angle between the lines parallel to the medial and lateral trochlear facets), the trochlear depth (the distance from the line connecting the most anterior parts of the medial and lateral femoral trochlear facets and the deepest part of the trochlear groove), and the patella angle (the angle between the lines parallel to the medial and lateral patellar facets) were measured to evaluate patellar alignment (Figs. 1 and 2). The lateral patellar tilt
angle and patella angle were measured at the middle axial slice of patella. MRIs were reviewed to detect the cases with patellar chondral lesions, and the patients were divided into two groups according to the absence or presence of chondromalacia patellae. The chondral lesions were graded using the International Cartilage Repair Society Classification System (Table 1) [20]. In patients with more than one chondral lesion, the most severe defect was used for grading [18]. Cases with chondromalacia patellae were further divided into two groups as mild (types 1 and 2) and severe (types 3 and 4) chondromalacia, and measurements were compared between two groups. Statistical analyses were performed using Number Cruncher Statistical System 2007 and the Power Analysis and Sample Size 2008 Statistical Software (Kaysville, UT, USA). The χ2 test or Student’s t test was used, where appropriate, and Pb .05 was used to determine statistical significance. 3. Results The patients’ ages ranged between 15 and 82 (mean: 46), including 179 women and 122 men. Chondromalacia patella was found in 145 (48%) of 301 cases, while 156 (52%) patients had normal patellar cartilage. Chondromalacia was mild (type 1 or 2) in 72 (49.5%) and severe (type 3 or 4) in 73 (50.5%) cases. The mean lateral patellar tilt angle was measured to be 10.08°± 4.34° in the chondromalacia group, while it was measured as 16.97°± 3.55° in the group without chondromalacia. Also, in the groups with or without chondromalacia patellae, the mean sulcus angles were 147.10° ±7.29° and 134.61°±6.47°, respectively. In patients without chondromalacia, the mean trochlear depth was measured to be 4.81± 0.96 mm, while in those with chondromalacia, the mean trochlear depth was 3.14±0.79 mm. The lateral patellar tilt angles and the
Fig. 1. Measurement of lateral patellar tilt angle (A), sulcus angle (B), trochlear depth (C), and patella angle (D) in a patient with mild chondromalacia.
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Fig. 2. Measurement of lateral patellar tilt angle (A), sulcus angle (B), trochlear depth (C), and patella angle (D) in a patient with severe chondromalacia.
trochlear depths of the chondromalacia group were significantly lower than those of the normal group (Pb.01), while the sulcus angles were significantly higher in the chondromalacia group (Pb .01). The mean patella angle was found to be 125.23°±8.68° in the chondromalacia group, while it was measured as 124.85°±7.01° in the group without chondromalacia. No statistically significant difference was found in patella angles between groups with and without chondromalacia (PN .05). The measurements of lateral patellar tilt angle, sulcus angle, trochlear depth, and patella angle are summarized in Table 2. The lateral patellar tilt angle, the sulcus angle, the trochlear depth, and the patella angle measurements were also compared between groups with mild (type 1 or 2) and severe (type 3 or 4) chondromalacia. No significant difference was found between the two groups, and the measurements are summarized in Table 3 (PN .05).
4. Discussion Femoral trochlear dysplasia may restrict patellofemoral joint stability and cause patellofemoral malalignment, patellar instability, patellar dislocation, and finally loss of patellofemoral cartilage [21].
In trochlear dysplasia, a shallow trochlear groove is related to patellar instability, and the sulcus angle reflects the degree of trochlear dysplasia [22]. Previously, in radiographic studies, a correlation between a wide sulcus angle and chondromalacia patellae was documented [5,6,10]. However, MRI studies evaluating trochlear dysplasia and its relation to chondromalacia are scarce, and their results are inconsistent [17–19]. Endo et al. failed to demonstrate a correlation between the depth of trochlea and chondromalacia patellae [19]. On the contrary, in a different MRI study, both the trochlear depth and the sulcus angle were reported to be associated with severe cartilage defects in a limited number of patients younger than 40 years of age [18]. Another study revealed no significant association between the sulcus angle and patellofemoral cartilage lesions; however, the sulcus depth was reported to be associated with cartilage lesions, and it was concluded that femoral trochlea with a shallow groove could increase the risk of chondromalacia patellae [17]. In an osteoarthritic group of patients, increased medial and lateral cartilage disruption in knees with increased sulcus angle was reported, and the wide sulcus was blamed to increase the pressure on patellofemoral articular surfaces and predispose to cartilage loss [23]. Our study showed that, in patients with chondromalacia patellae, the sulcus angle is increased, while trochlear Table 2 The distribution of parameters among normal and chondromalacia patella groups
Table 1 International Cartilage Repair Society Classification System Cartilage defect Normal Grade 0 Mild defect Grade 1 Grade 2 Severe defect Grade 3 Grade 4
MR findings Normal-appearing cartilage Normal contour with abnormal increased signal Defect b50% of the cartilage thickness Defect N50% of the cartilage thickness Defect extends to or into the subchondral bone
P value⁎
Patient groups
Lateral patellar tilt angle Sulcus angle Trochlear depth Patella angle ⁎ Student's t test. ⁎⁎ Pb.01.
Normal
Chondromalacia
Mean±S.D.
Mean±S.D.
16.97±3.55
10.08±4.34
.001⁎⁎
134.61±6.47 4.81±0.96 124.85±7.01
147.10±7.29 3.14±0.79 125.23±8.68
.001⁎⁎ .001⁎⁎ .674
498
B.K. Tuna et al. / Clinical Imaging 38 (2014) 495–498
Table 3 The distribution of parameters among groups with mild and severe chondromalacia patella P value⁎
Chondromalacia
Lateral patellar tilt angle Sulcus angle Trochlear depth Patella angle
Mild (types 1 and 2) (n=72)
Severe (types 3 and 4) (n=73)
Mean±S.D.
Mean±S.D.
9.76±3.54
10.39±5.01
.600
147.33±7.12 3.12±0.82
146.87±7.51 3.17±0.77
.916 .947
125.73±10.05
124.73±7.10
.947
⁎ Student's t test.
depth is decreased (Pb .01). These findings point out that, in individuals with dysplastic, i.e., more shallow, trochleas, an increased number of patellofemoral cartilage lesions may occur. Abnormal position of the patella in the femoral trochlear groove is also reported to play a role in the pathogenesis of chondromalacia patellae [2,24]. For radiological analysis of patellar tilt, several different imaging techniques and angle measurements have been described [4,24,25]. The lateral patellar tilt angle represents the angle of patellar inclination, which helps to evaluate the lateral stabilizing mechanism of patella [23]. As the lateral inclination of patella increases, the lateral patellar tilt angle decreases [23]. The patellar tilt has been correlated with patellofemoral joint disease radiographically [2]. However, by radiography, the patellofemoral cartilage cannot be assessed directly, and it is not possible to obtain tangential views at full extension of the knee. In studies using MRI, the measurement of the lateral patellar tilt angle at full extension is found to be more sensitive in determination of patellofemoral instability than at flexion [17,25,26]. In a study evaluating patients with osteoarthritis, the lateral patellar tilt angle was reported to be negatively associated with cartilage loss [23]. Yang et al. have found that lateral patellar displacement is associated with patellofemoral cartilage lesions, but the lateral patellar tilt angle was not measured in that study [17]. Our search of the literature revealed no MRI study investigating the relationship of the lateral patellar tilt with chondromalacia patellae. We have demonstrated that the lateral patellar tilt angle is decreased—therefore, patellar tilt is increased—in patients with chondromalacia patellae (Pb.01). In our study, patella angle was also studied, and no significant difference was found between chondromalacia and normal groups (PN .05). This finding was similar in previous studies [17,19]. The relationship of patellofemoral incongruency and the degree of chondromalacia has also been of concern. Ali et al. compared the measurements of each of the mild and severe chondromalacia groups with the control group and found no significant difference between patients with mild chondromalacia and normal group (PN .05). However, they reported statistically significant difference between patients with severe chondromalacia and patients with no chondromalacia in terms of sulcus angle, trochlear depth,, and lateral trochlear inclination angles in a limited number of patients (Pb.01). In our study, chondromalacia patients were also divided into two groups as mild (types 1 and 2) and severe (types 3 and 4). The same measurements were compared between these groups, and no statistically significant difference was found (PN.05). Our results reflect that patellar tilt and morphological properties of trochlea are related to the presence of chondromalacia but not its degree. We have recognized some limitations of our study. First, the diagnosis and grading of chondromalacia were made by MRI but not correlated to arthroscopic findings. It was previously reported that early cartilage changes observed at arthroscopy were not detected by MRI; therefore, in our study, early cartilage lesions might have been interpreted as normal [16]. Additionally, since this was a retrospective study, the routine sequences were used for evaluation instead of
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