|Year : 2018 | Volume
| Issue : 1 | Page : 17-21
The variation of the posterior tibial slope in South Indians: A hospital-based study of 290 cases
Supreeth Nekkanti, Pavan Patted, Lakshmi Malavika Nair, Vijay Chandru, G Shashank
Department of Orthopaedics, JSS Medical College and Hospital, Mysore, Karnataka, India
|Date of Web Publication||30-Jul-2018|
Dr. Supreeth Nekkanti
Department of Orthopaedics, JSS Medical College and Hospital, Mysore, Karnataka
Source of Support: None, Conflict of Interest: None
Background: The knowledge of the normal posterior tibial slope (PTS) is important for orthopaedic surgeons during joint replacement surgeries. Inadequate tibial cuts to replicate the normal tibial slope would lead to the tibial plate loosening or restriction of complete flexion. The tibial slope varies with age, gender, race and the ethnicity. We studied the tibial slope in the South Indian population. Aim: The aim of the study was to evaluate the PTS in a Southern Indian population and compare with the different known values across geographical and ethnic variations. Materials and Methods: The prospective study was conducted using the plain radiographs of the knee joint of 290 adult patients (age ranging from 18 to 81 years old with skiagrams showing complete epiphyseal fusion around the knee) collected over a period of 1 year from 10th January 2017 to 5th January 2018. Collected data were analysed statistically using SPSS (Statistical Package for the Social Sciences software) version 21 software. Results: The PTS varied between −5° and 21° with a mean value of 10.3771° ± 4.59482°. The mean PTS in males was 10.1232° ± 4.69607° and in females was 10.8825° ± 4.36616°. The mean PTS was highest (12.279) in the patients aged between 61 and 75 years of age and was least (8.243) in patients aged more than 75 years of age. There was a significant variation (P = 0.01) in the mean PTS in each age group of our study population [Table 1]. Conclusion: The tibial slope has been reported to vary in different ethnic subsets. In this study, the PTS varied between −5° and 21° with a mean value of 10.3771° ± 4.59482°. There was no statistical significant gender-based variation in the PTS. The PTS was lower than the PTS of the American, Nigerian and Chinese Populations but higher than the French population. We attempt to publish our results of the anatomical variation of the tibial slope in the Indian subcontinent.
Keywords: Anterior tibial line, South Indian population, tibial slope, total knee replacement
|How to cite this article:|
Nekkanti S, Patted P, Nair LM, Chandru V, Shashank G. The variation of the posterior tibial slope in South Indians: A hospital-based study of 290 cases. Niger J Orthop Trauma 2018;17:17-21
|How to cite this URL:|
Nekkanti S, Patted P, Nair LM, Chandru V, Shashank G. The variation of the posterior tibial slope in South Indians: A hospital-based study of 290 cases. Niger J Orthop Trauma [serial online] 2018 [cited 2019 Nov 12];17:17-21. Available from: http://www.njotonline.org/text.asp?2018/17/1/17/237838
| Introduction|| |
The articular surface of the tibial plateau forms a posteriorly and inferiorly directed slope relative to the long axis of the middle of the shaft, known as the posterior tibial slope (PTS). This slope was defined by the angle between a line tangential to the articular surface of the tibial plateau, and a perpendicular dropped from the line tangential to the anterior tibial cortex., [Figure 1] The slope is known to vary with respect to age, squatting habits and gender of the person., Further, the medial and lateral plateau are known to have different slopes within a single tibia.
|Figure 1: Measurement of posterior tibial slope line A: Line tangential to anterior tibial cortex line B: Line tangential to the articular surface of tibial condyle line C: Perpendicular was drawn to line APTS: Angle between Line B and Line C|
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The knee biomechanics are greatly affected by the tibial slope and are important for understanding anterior cruciate ligament (ACL) injury mechanisms. Studies have shown that ACL-injured individuals have a greater PTS than healthy controls. In fact, a greater PTS has been associated with greater peak ACL strain during a dynamic landing along with a greater anterior tibial translation., Furthermore, the slope is also an important consideration when planning surgeries such as high tibial osteotomy for genu recurvatum deformity, tibiofemoral osteoarthritis and knee arthroplasty.,, A comprehensive data and statistical analysis of the anatomical variation of the tibial slope amongst different populations may aid in identifying patients at risk of developing severe ACL injury at a relatively lower threshold of trauma, as well as forming a definite protocol for the management of the same. The objective of the present study was to provide range, mean and standard deviation as well as sexual dimorphism of tibial plateau angle (TPA) in a section of adult South Indian population in an attempt to provide insight into the anatomical variation of the PTS and to add to the data pool of South Asia.
| Materials and Methods|| |
The prospective study was conducted using the plain radiographs of the knee joint of 290 adult patients (age ranging from 18 to 81 years old with skiagrams showing complete epiphyseal fusion around the knee) collected over a period of 1 year from 10th January 2017 to 5th January 2018. The sample population included all patients attending the outpatient department (OPD) of orthopaedics of our institute for minor knee injuries such as bruises, lacerations around the knee joint and minor soft-tissue injuries of the knee joint. The exclusion criteria were patients with congenital anomalies or deformities of the knee joint and lower limb that could affect the alignment of the PTS, fractures or dislocations (recent or past) of the lower limb and any pathology that would alter the normal anatomy of the knee joint. Patients with ACL injury, diagnosed by clinical evaluation and/or magnetic resonance imaging (MRI)/arthroscopy, as well as advanced osteoarthritis (Kellgren-Lawrence Grade >2) were also excluded from the study, in view of their possible association with the PTS.,
No patient underwent radiological examination without clear clinical indication for the same, as part of the investigation for their respective symptoms at the time of visiting the OPD. Clearance of the Institutional Ethics Committee was taken from our Institutional Review Board. Informed consent was obtained from each patient before the examination, and all procedures/tests were explained to each patient in their native tongue. A clear medical history and routine clinical examination were performed on each patient to rule out ligament injuries, with special emphasis on ACL injuries (as inferred from a combination of anterior drawer test, Lachman test, prone Lachman test and pivot shift test).
Anteroposterior and true lateral view radiographs (showing superimposition of the femoral condyles) of the knee joints of the selected subjects were taken by experienced technicians using same X-ray machine of the Department of Radiodiagnosis of the institute with an exposure of 45 kV of 100 mA (exposure time varied according to the soft-tissue thickness around the knee). The radiographic technique was similar to all the subjects. For the lateral view radiograph, the patients were lying on the same side of the affected knee, which was flexed about 25°–30°. The central X-ray beam was directed vertically towards the medial aspect of the knee joint, with about 5°–7° cephalad angulation.
Measurements were taken in the true lateral view radiographs of properly selected patients by the single observer under the guidance of an experienced radiologist using the SigmaView software version 126.96.36.199 (Manufactured by AGFA HealthCare, AGFA-Gevaert N.V, Septestraat 27, B-2640 Mortsel, Belgium). A straight line (anterior cortical line) was drawn along the anterior cortex of the middle of the shaft of the tibia, and it was extended proximally to be intersected by the second straight line drawn tangential to proximal tibial articular surface connecting anterior and posterior ends of the tibial plateau. A further straight line was drawn from the point of intersection perpendicular to the anterior cortical line. The angle between this perpendicular line and the tangential line along the tibial plateau was the TPA [Figure 1]. For practical purpose, the angle formed by the first and the second line subtracted from 90° was the TPA. In true lateral view roentgenogram of the knee, the medial and lateral plateau was almost superimposed and the measured angle was a two-dimensional approximation of complex, asymmetric three-dimensional surface ignoring the difference between medial and lateral plateau. The method adopted here was first described by Moore and Harvey. Radiographs showing osteophytes in the anterior and/or posterior ends of the tibial plateau were excluded because of difficulty in measurement. Collected data were analysed statistically using SPSS software version 21 available in the institute.
| Results|| |
A total of 290 patients were considered in this study. The number of males and females in this study was 193 and 97, respectively [Graph 1]. The mean age of the study population was 42.12 ± 17.155 years with a range of 18–81 years [Table 1]. In males, the mean age was 42.19 ± 17.228. The mean age of the female study population was 41.99 ± 17.096. The highest number of patients (84%, 29%) belonged to the age group between 46 and 60 years of age [Table 2] and [Table 3] The mean PTS was highest (12.279) in the patients aged between 61 and 75 years of age and was least (8.243) in patients aged more than 75 years of age [Graph 2], [Graph 3]. There was a significant variation (P = 0.01) in the mean PTS in each age group of our study population [Table 4] Student's unpaired t-test revealed that there is no significant difference between age and sex of study subjects (P = 0.61). The PTS in this study varied between 0° and 21° with a mean value of 10.8825° ± 4.36616° in females. The mean PTS in males was 10.1232° ± 4.69607° and ranged from −5° to 20° [Table 5] and [Table 6]. There was no statistically significant gender-based variation in the PTS.
|Table 1: Mean posterior tibial slope of the study population based on age group|
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| Discussion|| |
The PTS is critical for flexion stability and range of motion. The tibial cuts to be taken during a total knee replacement surgery should replicate the natural tibial slope of the given demographic population. It becomes imperative that the operating surgeon has a thorough knowledge of the normal radiological parameters of the demographic population of patients he is operating upon. The PTS plays an important role in subsidence or loosening of the tibial component and post-operative range of motion and knee kinematics.,, An increased PTS exposes the weak cancellous bone posteriorly. However, if the cut is taken perpendicular to the tibial axis leading to a 0° posterior slope, it would increase the chances of tibial plate loosening as well as restrict the range of complete knee flexion. Posterior stabilised designed implants require the tibial cut to be made such that the PTS is kept to a minimum to avoid flexion instability on the contrary, posterior cruciate ligament retaining designs require a higher tibial slope to facilitate the rollback phenomenon.
Moore and Harvey in their study of fifty American patients reported the PTS to range from 7° to 22° with a mean of 14° ± 3.7°. Brazier et al. observed the PTS range from 3.47° to 20.29° with a mean of 11.4° ± 3.6°. In another study by Genin et al. in the French population, the PTS ranged from −1° to 18° with a mean of 7.9° ± 3.2°. Chiu et al. published his results of a cadaveric bone study in the Chinese population to be ranging from 5° to 22°, mean of 14.7° ± 3.6° [Table 7]. There is only one other study in the East Indian population by Medda et al., who reported the PTS to range from 6° to 24° with a mean of 13.6° ± 3.5°. In our study, we observed the PTS range from −5° to 21°, with a mean value of 10.3771° ± 4.59482°. Kate and Robert also studied the slope in dry bones in the Indian population. The specific demographic profile of the study could not be identified.
|Table 7: Variation of posterior tibial slope in other ethnic population subsets|
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Khattak et al. studied the medial and lateral plateau slopes separately in a Pakistani Population of both genders. They published that the medial tibial slope was significantly greater than the lateral tibial slope in females but not in males [Table 8]. The lateral slopes, however, did not vary significantly. In our study, the male patients had a mean PTS. The mean PTS in males was 10.1232° ± 4.69607° and in females was 10.8825° ± 4.36616 °. The P value was 0.185, which meant there was no statistical significance in the PTS between the males and females in our study.
|Table 8: Results of variation of medial versus lateral tibial slope in other populations|
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Hashemi et al. performed an MRI-based study and observed that both the medial and lateral tibial slopes were greater in females compared to males. The lateral tibial slope was greater than the medial tibial slopes in both the genders. The reference axis used was the anatomical axis in the sagittal plane. This was different from the axis that was used in our study and others.
The limitation of this study is that it is single hospital-based study. The results of this sample population may not necessarily represent the entire South Indian population. A separate medial and lateral tibial slope could not be measured as this was an X-ray based study. An interobserver difference while measuring the angle could also exist. A similar MRI-based study could be conducted to obtain more information of the radiological morphometry of the knee joint.
| Conclusion|| |
This study aimed to understand the normal PTS in the South Indian population. The PTS varied between −5° and 21° with a mean value of 10.3771 ± 4.59482. There was no significant gender-based variation of PTS in our study. Radiographic variation of the normal PTS s has been reported in different subsets of populations. The mean PTS in our study was lower than the PTS of the American, Nigerian and Chinese Populations but higher than the French population. A thorough knowledge of the normal parameters in the subset population is required to plan the total knee replacement surgery and to have favourable outcomes.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]