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The menisci of the knee joint in human foetuses of manipur population--a morphological study.

BACKGROUND

The menisci are two crescentic lamellae, which serve to deepen the surfaces of the articular fossae of the head of the tibia for reception of the condyles of the femur. The menisci share load and reduce contact stresses across the joint. The anatomical abnormalities and variations of the intra-articular structures of the knee joint have recently become significant because of new techniques such as arthroscopy, CT and MRI. In American football, knee is the most commonly injured joint. [1] Meniscal injuries accounts for 12% of all football knee injuries. Injuries are sustained more often by the medial than the lateral meniscus in the proportion of 4:1, 5:1 or even 20:1. The snapping knee syndrome is usually related with the type of the meniscus or to the presence of a tear of the meniscus. This syndrome appears more often in children and young adolescents, and it is usually related with the type of meniscus like discoid meniscus. [2]

Also, the investigations of these parameters are important in order to describe the morphological features for clinical diagnosis and for surgical procedures. [3] In meniscus allograft transplantation, it has been stated that providing a meniscal allograft that matches the size and shape of the meniscus to the recipient's knee is the responsibility of the tissue bank providing the graft. [4] Long-term complications of removal of a meniscus include cartilage degeneration and bone remodelling, this discovery changed considerably the therapeutic approach to this common work or sports injury. [5] Hence, today a ruptured meniscus is repaired rather than removed, but this treatment is only feasible when the meniscus tissue is otherwise of good quality. [6] The reported incidence of discoid meniscus ranges from 0.4% to 17% for the lateral and 0.06% to 0.3% for the medial side. The condition is more frequently reported in Asian countries. Discoid meniscus are often asymptomatic but can be associated with knee pain, a snapping or popping knee. [7] The incidence of bilateral lateral discoid meniscus is up to 20% of the cases, whereas bilateral medial involvement is rare. [8] Discoid type of lateral meniscus has been discussed in both anatomical and orthopaedic literature. Very few data are available related to classification of menisci according to their shapes or racial differences. [9] The aim of the present study is to describe the morphology of the menisci and the incidence of discoid meniscus in foetal knee joints of Manipur population.

MATERIALS AND METHODS

To carry out this cross-sectional descriptive study, 100 human foetal cadavers were collected from the Department of Obstetrics and Gynaecology, RIMS Hospital, Imphal with the permission of concerned authorities and parents. To carry out this study, a formal permission from the Institutional Ethical Committee was obtained. The study included 100 right and 100 left foetal knee joints from 100 foetuses without musculoskeletal system anomalies. The age of the foetus was determined from the crown-rump length (CRL) and obstetrical history, and foetuses ranged from 14 to 37 weeks of gestation (Table 1). Each knee was taken as a separate sample and not as one of a pair of samples in a foetus. All specimens were preserved in 10% formaldehyde solution. Skin of the knee joints with fibrous capsule and the ligamentum patellae was cut along with the collateral ligaments. The anterior and the posterior cruciate ligaments were also cut and tibial plateau were exposed. The morphological variants of the shapes of the lateral and the medial menisci were macroscopically noted and classified. The menisci were subgrouped as C shaped, U shaped, V shaped, crescentic and incomplete discoid. Discoid meniscus was classified according to Watanabe et al where if the meniscus occupied more than 80% of the tibial plateau it is considered as complete type and less than 80% but wider than usual is called as incomplete type and as a Wrisberg ligament. [10]

Description of Meniscus

Discoid Meniscus

When the meniscus covers the tibial plateau circularly, the meniscus is said to be discoid type. [1]

Incomplete discoid meniscus: The incomplete discoid menisci had an open area at the centre of the menisci and they were all horseshoe shaped. [3]

Complete Discoid Meniscus

The menisci which did not have any open area at the centre of the menisci were defined as the complete discoid menisci.

Crescentic Meniscus

The menisci, which had thin anterior and posterior horns and a thin body, were defined as the crescentic (semilunar) type.

Sickle Shaped Meniscus

The menisci, which had thin anterior and posterior horns and a thick body, were defined as the sickle-shaped type.

Other Types

The menisci which resembled like sided U, sided V and C were named as sided U, sided V and C shaped, respectively. [2]

RESULTS

From observations, five morphological types of the shape of menisci were determined. Observation on the Medial Meniscus (MM) found 79% were crescent shaped, 11% were C shaped, 7% were V shaped and 3% were incomplete discoid. (Table 2 and Figure 1-3). U shaped MM was not observed. No discoid menisci were seen.

Among the Lateral Meniscus (LM), 56% were C shaped, 31% crescentic, 8% U-shaped and 5% were incomplete discoid. (Table 3 and Figure 4-6). No complete discoid meniscus was observed in our study.

DISCUSSION

The differences of the shape of meniscus may be due to the mesenchymal differentiation or to the development of the vasculature early in embryonic life. [3] The meniscus arises from the differentiation of mesenchymal tissue within the limb bud and becomes a clearly defined structure by the eighth week of foetal development. [11] Variations of morphological differences of menisci can determine the possibility of an injury. However, the data related to the morphometric parameters of these structures are scarce. [12] There are marked differences in the contour and insertion between the lateral and the medial menisci which are important in relation to the injury mechanisms. [13]

Injuries to the meniscus are common in work, sports, everyday activities and can be disabling. Parsons noted that the medial meniscus always has a crescent shape but that the lateral meniscus may have either a crescent or a disc shape. In 1889, Young first described a discoid lateral meniscus in a cadaver specimen. [14] The most common congenital abnormality of the meniscus in a man is a discoid meniscus with a frequency of 3% to 5% in the general population and slightly higher in Asian populations. [15]

Normal variants of the meniscus are relatively uncommon and are frequently asymptomatic, although there is a greater propensity for discoid menisci to tear. However, recognising these variants is important, as they can be misinterpreted for more significant pathology on MRI. The most common of these meniscal variants is the discoid lateral meniscus and the least common is complete congenital absence of the menisci. Normal variants of the meniscus include hypoplastic menisci, absent menisci, anomalous insertion of the medial meniscus, discoid lateral meniscus, including the Wrisberg variant and discoid medial meniscus. [16] Anomalies of the meniscal shape have been reported in a man and are classified as hypoplasia or hyperplasia. The meniscal hyperplasias or discoid menisci, have been the object of many studies, because they are frequently the source of symptoms. [13] Of the several reported congenital meniscal abnormalities, anomalous attachments of the meniscal horns and discoid menisci are the most frequent. They most frequently affect the lateral side of the knee. In 1967, first case of medial meniscal hypoplasia was reported. The association of simultaneous anomalies in the knee, in some cases is likely due to the common mesenchymal origin of some of these structures. [17]

There are reported cases of complete absence of the medial meniscus as described in thrombocytopenia-absent radius syndrome (TAR syndrome). The congenitally absent meniscus appears to influence the development of the distal femur and proximal tibia, the proximal medial tibia was convex and the distal medial femoral condyle was saddle shaped in these cases. [18] A new case was reported of bilateral hypoplasia of the medial meniscus not in association with other knee anomalies in a young woman as a consequence almost all the medial tibial plateau surface was uncovered. [19]

Studies done by Brantigan et al [20] And Miller et al [21] say that the medial meniscus is much larger in diameter and thinner at the periphery. Studies by Pollard et al [22] and Shaffer et al [23] describe medial meniscus as semi-circular in shape with the posterior horn wider than the anterior horn. Study by Greis et al [24] mentions that medial meniscus is C shaped; posterior horn is larger than anterior horn in anteroposterior dimension. Miller et al [21] explained that the lateral meniscus is smaller in diameter, thicker about the periphery, and usually wider than medial.

In a study done by Gupta S et al, [25] medial meniscus was found to be crescent shaped (10%), U shaped (72%), sickle shaped (16%) and V shaped (2%). And, the lateral meniscus was subgrouped as C shaped (96%) and U shaped (4%). No discoid medial or lateral meniscus was found in the study.

Itagi V et al [26] found that in most of the specimens, the medial meniscus was crescentic in shape (96.66%). Commonest shape of the lateral meniscus was 'C' shape (88.33%). Incomplete lateral discoid menisci were observed in 5% of lateral meniscus. No complete discoid medial or lateral menisci were observed in specimens.

In a sample of 316 nonhuman primates, representative of 43 genera, the lateral meniscus morphology was studied. The lateral meniscus has a crescentic shape in Prosimii, in Platyrrhini (New World monkeys) and in Pongo pygmaeus. The lateral meniscus is disc-shaped, with a central foramen, in Catarrhini (Old World monkeys), in Hylobates, in Gorilla and in Pan troglodytes. [27]

Kale et al [3] observed in medial meniscus that 18.18% were crescentic, 22.72% V shaped, 9.09% U shaped, 36.36% sickle shaped and 13.63% C shaped. In lateral meniscus, they observed 13.63% crescentic, 9.09% C shaped, 77.27% discoid shaped (54.54% were incomplete discoid and 22.72% were complete discoid). Murlimanju BV et al [2] observed in medial meniscus that 50% were crescentic, 38.9% V shaped, 11.1% U shaped and in lateral meniscus 61.1% were C shaped and 38.9% crescentic. They did not observe any discoid meniscus. Murlimanju BV et al [28] also reported a complete type of discoid lateral meniscus, which was found on the left knee joint of an embalmed female foetal cadaver. On medial meniscus, most common finding was sickle shaped (36.36%) in Kale et al [3], crescentic (50%) in Murlimanju BV et al [2] and crescentic (79%) in the present study. On lateral meniscus, the most common was incomplete discoid (54.54%) in Kale et al8, C shaped (61.1%) in Murlimanju BV et al [2] and C shaped (56%) in the present study. The finding of the present study is comparatively closer to the finding of Murlimanju BV et al. [2] The difference in the findings may be due to ethnicity of the study population.

CONCLUSION

In the present study, the majority of the knees showed C-shaped lateral meniscus and crescent-shaped medial meniscus. Incomplete discoid lateral meniscus was observed in 8%. No total discoid meniscus was observed in the study. This study has provided further information on different shapes of the medial and lateral meniscus especially the presence of incomplete lateral discoid menisci, which is a rare finding. This study is useful for the health professionals who work on the treatment of meniscal injuries to create an awareness of the anatomical variations that may exist in the menisci facilitating the rehabilitation process.

ACKNOWLEDGEMENT

We acknowledge the support and help extended by all the staff of Department of Anatomy, RIMS, Imphal. Authors acknowledge the immense help received from the scholars whose articles are cited and included in references of this manuscript. The authors are also grateful to authors/editors/publishers of all those articles, journals and books from where the literature for this article has been reviewed and discussed.

REFERENCES

[1] Murlimanju BV, Nair N, Pai S, et al. Morphological study of the menisci of the knee joint in adult cadavers of the South Indian population. Marmara Medical Journal 2010;23(2):270-5.

[2] Murlimanju BV, Nair N, Pai MM, et al. Morphology of the medial meniscus of the knee in human fetuses. Rom J Morphol Embryol 2010;51(2):347-51.

[3] Kale A, Kopuz C, Edyzer M, et al. Anatomic variations of the shape of the menisci: a neonatal cadaver study. Knee Surg Sports Traumatol Arthrosc 2006;14(10):975-81.

[4] Haut TL, Hull ML, Howell SM. Use of roentgenography and magnetic resonance imaging to predict meniscal geometry determined with a three-dimensional coordinate digitizing system. J Orthop Res 2000;18(2):228-37.

[5] Fairbank TJ. Knee joint changes after meniscectomy. J Bone Joint Surg 1948;30B(4):664-70.

[6] Messner K, Gao J. The menisci of the knee joint. Anatomical and functional characteristics, and a rationale for clinical treatment. J Anat 1998;193(Pt 2):161-78.

[7] Kelly BT, Green DW. Discoid lateral meniscus in children. Curr Opin Pediatr 2002;14(1):54-61.

[8] Yaniv M, Blumberg N. The discoid meniscus. J Child Orthop 2007;1(2):89-96.

[9] Charles CM. On the menisci of the knee joint in American whites and negroes. Anat Rec 1935;63(4):355-64.

[10] Watanabe M, Takada S, Ikeuchi H. Atlas of arthroscopy. Injury 1972;3(4):283.

[11] Kaplan EB. Discoid lateral meniscus of the knee joint; nature, mechanism, and operative treatment. J Bone Joint Surg 1957;39-A(1):77-87.

[12] Almeida SKS, De Moraes ASR, Tashiro T, et al. Morphometric study of menisci of the knee joint. Int J Morphol 2004;22(3):181-4.

[13] Smillie IS. Injuries of the knee joint. 4th edn. London: Churchill Living Stone 1975:23-38.

[14] Young R. The external semilunar cartilage as a complete disc. In: Cleland J, Mackay J, Young R. (eds). Memoirs and memoranda in anatomy. London: Williams and Norgate 1889:pp 179.

[15] Kocher MS, Klingele K, Rassman SO. Meniscal disorders: normal, discoid, and cysts. Orthop Clin North Am 2003;34(3):329-40.

[16] Ali S, Dass C, Shah P, et al. Normal variants of the meniscus. Applied Radiology 2013:14-8.

[17] Clark CR, Ogden JA. Development of the menisci of the human knee joint. Morphological changes and their potential role in childhood meniscal injury. J Bone Joint Surg Am 1983;65(4):538-47.

[18] Tolo VT. Congenital absence of the menisci and cruciate ligaments of the knee. A case report. J Bone Joint Surg Am 1981;63(6):1022-4.

[19] Monllau JC, Gonzalez G, Puig L, et al. Bilateral hypoplasia of the medial meniscus. Knee Surg Sports Traumatol Arthrosc 2006;14(2):112-3.

[20] Brantigan OC, Voshell AF. The mechanics of the ligaments and menisci of knee joint. J Bone Joint Surg 1941;13:44-66.

[21] Miller RH. Knee injuries. In: Canale ST, Beatty JH, (eds). Campbell's operative orthopaedics. Philadelphia, Mosby Elsevier 2003:2182-99.

[22] Pollard ME, Kang Q, Berg EE. Radiographic sizing for meniscal transplantation. Arthroscopy 1995;11(6): 684-7.

[23] Shaffer B, Kennedy S, Klimkiewicz J, et al. Preoperative sizing of meniscal allografts in meniscus transplantation. Am J Sports Med 2000;28(4):524-33.

[24] Greis PE, Bardana DD, Holmstrom MC, et al. Meniscal injury: I. Basic science and evaluation. J Am Acad Orthop Surg 2002;10(3):168-76.

[25] Gupta SA, Bhavsar SP, Singh A, et al. Morphometric study on tibial menisci in west Indian cadavers. J Anat Sciences 2016;24(1):43-6.

[26] Itagi V, Shirol VS, Jayasudha K. Morphology of menisci of knee joint in adult cadavers of north Karnataka. Int J Cur Res Rev 2015;7(5):43-7.

[27] Le Minor JM. Comparative morphology of the lateral meniscus of the knee in primates. J Anat 1990;170:161-71.

[28] Murlimanju BV, Nair N, Kumar V. Complete lateral discoid meniscus in a South Indian fetus: a case report and review of literature the medial menisci in both the knee joints of the fetus were having. Int J Anat Variations 2010;3:110-1.

Colney Suzanne L (1), Sanjenbam Sonali Devi (2), Thounaojam Naranbabu Singh (3)

(1) Tutor, Department of Anatomy, TMC, Agartala, Tripura.

(2) Senior Resident, Department of Anatomy, RIMS, Imphal.

(3) Professor, Department of Anatomy, RIMS, Imphal.

Financial or Other, Competing Interest: None. Submission 23-06-2017, Peer Review 09-08-2017, Acceptance 16-08-2017, Published 21 -08-2017.

Corresponding Author:

Sanjenbam Sonali Devi, Senior Resident, Department of Anatomy, Regional Institute of Medical Sciences, Imphal, Manipur, Lamphelpat-795004.

E-mail: sonali.sanjenbam@gmail.com

DOI: 10.14260/jemds/2017/1043

Caption: Figure 1. Left Tibial Plateau showing Crescent-shaped Medial Meniscus of a Foetus

Caption: Figure 2. Right Tibial Plateau showing V-shaped Medial Meniscus

Caption: Figure 3. Left Tibial Plateau showing C-shaped Medial Meniscus

Caption: Figure 4. Right Tibia! Plateau showing C-shaped Lateral Meniscus

Caption: Figure 5. Left Tibial Plateau showing U-shaped Lateral Meniscus

Caption: Figure 6. Left Tibial Plateau showing Crescentic Lateral Meniscus

Caption: Figure 7. Left Tibial Plateau showing Incomplete Discoid Lateral Meniscus. L-Lateral
Table 1. Different Gestational Ages of the Foetus in the Study

Age (in Weeks)       14-20   21-30   31-37

Number of foetuses    40      43      17

Table 2. Incidence of Different Shapes of Medial Menisci (n=200)

Shape                Total no. (Percentage)

Crescentic                    79%
C-shaped                      11%
V-shaped                       7%
Incomplete Discoid             3%
U- shaped                     Nil

Table 3. Incidence of Different Shapes of Lateral Meniscus (n=200)

Shape                Total no. (Percentage)

C-shaped                      56%
Crescentic                    31%
U-shaped                       8%
Incomplete discoid             5%
V-shaped                      Nil

Table 3. Incidence of Different Shapes of Lateral Meniscus (n=200)

Shape       Kale et al (3)    Murlimanju BV et al (2)   Present Study

            Medial  Lateral    Medial   Lateral         Media   Lateral

C-shaped    13.63   09.09       00       61.1             11       56
Crescentic  18.18   13.63       50       38.9             79       31
U-shaped    09.09   00          11.1      00              00       08
Incomplete
 discoid     00     54.54       00        00              03       05
Complete
 discoid     00     22.72       00        00              00       00
V-shaped     22.72   00         38.9      00              07       00
Sickle       36.36   00
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Title Annotation:Original Research Article
Author:Colney, Suzanne L.; Devi, Sanjenbam Sonali; Singh, Thounaojam Naranbabu
Publication:Journal of Evolution of Medical and Dental Sciences
Article Type:Report
Geographic Code:9INDI
Date:Aug 21, 2017
Words:2994
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