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HISTOSTRUCTURE OF KNEE MENISCI IN THE MEN OF DIFFERENT BODY TYPES Russkikh A.N., Shabokha A.D., Kasimov V.I.

Krasnoyarsk State Medical University named after prof. V.F. Voino-Yasenetskiy, Krasnoyarsk, Russia

 

The knee joint injury takes a leading place in addressing for medical care in patients of working age. It is often accompanied by degenerative and dystrophic diseases, disability and limited physiological mobility of the joint [1, 2]. The issue of dissatisfaction with the offered methods for prevention and treatment of such conditions is still actual. Certainly, the knee joint is exposed to various types of load, and structural changes are not distinguishable at the macrolevel, although changes in microlevel are significant even in nonthreatening conditions [3].

Rybalko D.Yu. et al. (2015) investigated the histological structure of various zones of human knee meniscus and identified some age characteristics. They found that the knee meniscus structure was uniform with acellular regions and regions with small amount (1-3) chondrocytes (the mean diameter from 11.19 ± 3.02 to 12.51 ± 1.97 µm) in persons at the age ≤ 35 (mature age). With age, the amount of chondrocytes and their diameter increase (to the maximal value – 22.01 µm), regions with maximal level of chondrocytes appear. Isogenous groups are more common. The meniscus structure becomes ununiform and loose, with lower percentage of elastic fibers. Such changes in meniscus suppose the development of degenerative and dystrophic processes over age [3, 4].

At the same time, there are some described cases of degenerative and dystrophic changes in knee meniscus and susceptibility to different injuries in children, adolescents and persons at the age ≤ 35 [5]. Moreover, the statistical analysis of the results of the study by Rybalko D.Yu., and absence of statistically significant differences in some case suppose an unknown factor of knee joint pathology [3, 4].

It has been proved that the risk of different diseases is mainly related to life style, hypodynamia, excessive body mass and, not least importantly, with body composition [3, 6-9]. For example, one of the last studies by Gorbunov N.S. and Tutynin K.V. (2015), which was dedicated to constitutional features of older women with trochanteric fractures and femoral neck fractures, demonstrate a relationship between manifestation of diseases and features of body composition. The study identified some evident constitutional differences in older women with trochanteric fractures and femoral neck fractures. So, according to the classification by Shevkunenko V.N., women with femoral neck fractures demonstrate the dominance of persons of dolichomorphic type, and a low percentage of persons of brachymorphic type of body composition as compared to women with trochanteric fractures [10].

Such studies are multiple, and they suppose a presence of a causal relationship between the locomotor system (particularly, the knee joint) and features of body composition [1, 11, 12].

Considering the above-mentioned facts, the objective of the study was to determine the histological structure of the man’s knee meniscus, taking into account the features of his physique.

MATERIALS AND METHODS

The cadaveric male (age of 32-55) internal and external menisci of both knee joints were investigated. The ethical principles and the standards of the study were adhered (the extract from the protocol of the local ethical committee of Krasnoyarsk State Medical University No.39/2012, March 28, 2012).

After standard fixation of the biological samples in 10 % formaline, the menisci were sectioned at the level of their anterior and posterior horns and the body. The hematoxylin-eosin stained histological specimens were exposed to microscopy, estimation and morphometry of knee menisci specimen. The inclusion criteria were absence of inflammatory and dystrophic changes in the hyaline cartilage. The diameter of chondrocytes was estimated at different levels of meniscus section. The amount of single cells and isogenous groups per square unit of unchanged cartilaginous tissue were estimated.

The constitutional approach allowed individualizing the results. The estimation of body composition was conducted with the technique by W.L. Rees – Н.J. Eysenck, with first-priority estimation of anthropometric parameters of the studied objects: the length of the body and the transverse diameter of the chest [13]. The regional features were considered during estimation of results of anthropometric study [8, 9, 14].

The statistical analysis was conducted with SPSS Statistics 17.0. The normalcy of distribution was estimated with Shapiro-Wilk test. The characteristics of ordered samples for quantitative signs with non-parametrical distribution and the data with parametrical distribution (owing to low number) were presented with measure of central tendency – mean (M), median (Me), mode (Mo) and measure of dispersion – mean quadratic deviation, range, interquartile range [P₂₅; P₇₅]. Non-parametric Mann-Whitney test (U-test) was used for comparison of two independent samples of non-parametrical data, with its critical value of 1,308 (with N = 84) for p < 0.05 and 1,189 for p < 0.01. Kruskal-Wallis test was used for comparison of three independent samples of non-parametrical data [15].

 

RESULTS AND DISCUSSION

The study showed that the structure of the cartilage of the external and internal menisci of both knee joints included the perichondrium zone, where single spindle-shaped chondroblasts and the zones of new and mature cartilages without clear borders were visualized. At the background of prevailing intercellular space, the isogenous groups of chondrocytes (in lacunes) were found. As a rule, such accumulations consist of two-four cells. Such structure is common for all levels of histological sections of both menisci regardless of a side of examination of the male knee joints (the table 1).

Table 1 Histological characteristics of menisci of both knee joints in the men (n = 84)

Parameter	Examination level	сустав Right knee joint	Left knee joint	p level
1	2	3	4	5
Internal meniscus
Mean diameter of chondrocytes (µm)	Anterior horn of meniscus	11.62 [11.17; 11.97]	11.74 [11.33; 11.98]	NA
	Meniscus body	12.33 [11.9; 12.75]	12.12 [11.63; 12.7]	NA
	Posterior horn of meniscus	12.47 [12.04; 13.25]	12.31 [11.33; 12.5]	NA
Amount of single cells (c.u.)	Anterior horn of meniscus	14.95 [13.2; 15.9]	14.1 [13.15; 15.5]	NA
	Meniscus body	12.85 [9.45; 13.9]	13.2 [12.0; 14.1]	NA
	Posterior horn of meniscus	13.68 [13.2; 14.2]	13.8 [10.3; 14.5]	NA
Amount of isogenous groups of chondrocytes (c.u.)	Anterior horn of meniscus	1.29 [1.1; 1.7]	1.33 [0.45; 1.6]	NA
	Meniscus body	1.35 [1.1; 2.05]	1.32 [0.8; 1.5]	NA
	Posterior horn of meniscus	1.27 [0.9; 2.5]	1.11 [0.9; 2.1]	NA
External meniscus
Mean diameter of chondrocytes (µm)	Anterior horn of meniscus	12.08 [11.68; 12.58]	11.9 [11.42; 12.54]	NA
	Meniscus body	12.43 [12.9; 12.64]	12.01 [11.7; 12.8]	NA
	Posterior horn of meniscus	12.34 [11.6; 12.88]	12.34 [11.6; 12.6]	NA
Amount of single cells (c.u.)	Anterior horn of meniscus	15.07 [13.8; 15.4]	14,7 [13.8; 15.2]	NA
	Meniscus body	12.72 [12.0; 13.4]	13.01 [12.9; 13.8]	NA
	Posterior horn of meniscus	13.35 [11.8; 14.4]	13.33 [11.7; 13.9]	NA
Amount of isogenous groups of chondrocytes (c.u.)	Anterior horn of meniscus	1.49 [1.1; 1.7]	1.29 [0.45; 1.6]	NA
	Meniscus body	1.27 [1.0; 2.05]	1.21 [0.8; 1.5]	NA
	Задний рог мениска Posterior horn of meniscus	1.06 [1.0; 1.4]	1.64 [0.9; 2.5]	NA

Note: NA – no significant differences between the groups. 

The detailed comparative analysis of the results of morphometry of section of internal and external menisci of both knee joints identified the absence of statistically significant differences between the compared parameters of morphometry at different levels of a section, between menisci and between the opposite sides. So, the mean diameter of chondrocytes was 11.62 [11.17; 11.97] µm at the level of the anterior horn of the internal right knee meniscus. It did not differ statistically from the mean diameter of chondrocytes of the anterior horn of the external meniscus of the same knee – 12.08 [11.68; 12.58] µm within the interquartile range P_25-75. The similar picture is observed in comparison with parameters of amount of some cells and amount of isogenous groups of chondrocytes. The mean amount of individual cells was 13.69 [13.2; 14.2] (the level of the posterior horn of the internal right knee meniscus), the average amount of isogenous groups of chondrocytes – 1.27 [1.0; 2.05] (the level of the body of the external right knee meniscus). Therefore, the further text of the article demonstrate only the results of the comparative analysis of the morphometric values of only medial meniscus of the right knee joint in the men in the compared groups.                              

The further analysis of the results confirms the presence of previous results of histological structure of knee menisci over age described in the studies by Rybalko D.Yu. (2015) [3, 4, 5]. So, the structure of knee menisci in the men (age ≤ 35) has the perichondrium with smooth borders and single chondroblasts. There are some unevenly distributed isogenous groups of chondrocytes (in lacunes) in the region of young and mature cartilage (Fig. 1).

Figure 1

Hyaline cartilage tissue of the anterior horn of medial meniscus of the right knee joint of the men aged of 32. Hematoxylin and eosine staining. Magnification × 400. I – perichondrium zone, 1 – isogenous group of chondrocytes, 2 – single chondrocyte.

The hyaline cartilage of knee menisci has some changes in men older 35. The number of chondrocytes in cartilaginous zones demonstrates visual increase. Single hypertrophied chondrocytes and events of karyopyknosis and karyorhexis appear. The number of isogenous groups increases (Fig. 2).

Figure 2

Hyaline cartilage tissue of the anterior horn of medial meniscus of the right knee joint of the men aged of 48. Hematoxylin and eosine staining. Magnification × 400. 1 – isogenous group of chondrocytes, 2 – a single chondrocyte with evident lacuna.

The estimation of morphological significance of the identified visual features in men of the second stage of mature age is not possible owing to minimal statistically reliable differences in the studied parameters which consist in only features of amount of isogenous groups of chondrocytes (the table 2).

Table 2

Histological characteristics of knee menisci in the men of 1st and 2nd periods of mature age (n = 84)

Parameter	Examination level	1st period of mature age (n1=35)	2nd period of mature age (n2=49)	p level
1	2	3	4	5
Mean diameter of chondrocytes (µm)	Anterior horn of meniscus	11.62 [11.33; 11.98]	11.39 [11.17; 11.88]	NA
	Meniscus body	12.33 [11.9; 12.74]	12.18 [11.63; 12.75]	NA
	Posterior horn of meniscus	12.47 [11.33; 12.84]	13.06 [11.65; 13.25]	NA
Amount of single cells (c.u.)	Anterior horn of meniscus	14.55 [13.15; 15.8]	14.97 [14.8; 15.9]	NA
	Meniscus body	13.85 [9.45; 13.9]	13.72 [13.0; 14.1]	NA
	Posterior horn of meniscus	14.08 [13.2; 14.5]	14.05 [10.3; 14.4]	NA
Amount of isogenous groups of chondrocytes (c.u.)	Anterior horn of meniscus	1.09 [0.45; 1.4]	1.28 [1.1; 1.7]	NA
	Meniscus body	1.85 [1.1; 2.05]	1.16 [0.8; 1.8]	NA
	Posterior horn of meniscus	1.37 [0.9; 1.8]	2,14 [2.0; 2.5]*	р < 0.05

Note: NA – no significant differences between the groups; * – differences are statistically reliable for comparison of the value of the examined parameter at the level of posterior horn of meniscus (p < 0.05).

The table 2 shows some statistically reliable differences in comparison of parameters of isogenous groups of chondrocytes in men of different age at the level of the posterior horn of menisci. Here, the value of this parameter in men of the second period of mature age is 2.14 [2.0; 2.5] that is statistically higher than the similar parameter in men of the first period of mature age (1.37 [0.9; 1.8], p < 0.05). Moreover, men of this age group demonstrate the significantly higher amount of isogenous groups of chondrocytes at the level of the posterior horn of meniscus in comparison with the level of the body or the anterior horn of meniscus (1.16 [0.8; 1.8] and 1.28 [1.1; 1.7] within the interquartile range Р_25-75). Concerning such parameters as mean diameter of chondrocytes and amount of single cells, they have not any age features and are 12.18 [11.63; 12.75] (the level of meniscus body in men of the second period of mature age) and 14.08 [13.2; 14.5] (the level of the posterior horn of meniscus in men of the first period of mature age) correspondingly.

As result of the anthropometric examination with subsequent somatotyping (according to W.L. Rees – Н.J. Eysenck) of 84 male cadavers, 32 (38 %) showed the pyknic type, 24 (28.5 %) – normosthenic type, 28 (33.5 %) – asthenic type. The comparative estimation of the histological structure of menisci in men of different body composition is presented in the table 3.

In comparison with age differences of histologic structure of menisci, the table 3 shows some constitutional features. First of all, the interesting fact is presence of statistically reliable differences in all examined parameters at the level of the posterior horn of menisci in men of pyknic type. At this level, the mean diameter of chondrocytes of knee menisci is 13.08 [12.77; 13.25] µm that is higher than the values at the level of the body and the anterior horn of menisci (11.55 [11.35; 11.86] and 12.48 [11.64; 12.58] µm correspondingly within the interquartile range Р_25-75). Also men of this body composition demonstrate the minimal amount of single cells at the level of posterior horn of menisci (11.1 [10.3; 11.6] in 13.2 [11.85; 13.7] near the body and 15.7 [13.5; 15.3] in the plane of the anterior horn), and maximal value of amount of isogenous group – 2.3 [2.2; 2.5] (1.8 [1.2; 2.05] and 1.3 [0.6; 1.7] correspondingly at the level of the body and the anterior horn). The structure of the tissue is uneven, with chaotic position of isogenous groups, ruptured perichondrium with multiple increased chondrocytes with events of karyopyknosis (Fig. 3).

Figure 3

Hyaline cartilage tissue of the posterior horn of medial meniscus of the right knee joint in a man of pyknic type. Hematoxylin and eosine staining. Magnification × 400. 1 – isogenous group of chondrocytes, 2 – a single chondrocyte.

The comparative analysis of the morphometric parameters of menisci at the level of the posterior horn of men of pyknic type and men of asthenic and normosthenic types show the presence of the statistically reliable differences. So, the mean diameter of chondrocytes in the value of 13.08 [12.77; 13.25] µm at the level of the posterior horn is higher than values of the parameter in asthenic and normosthenic types (12.15 [11.33; 12.3] and 12.44 [11.61; 12.67] correspondingly within the interquartile range Р_25-75). Such reliable constitutional predominance of the parameter at the level of the posterior horn of meniscus is common for amount of isogenous groups of chondrocytes – 2.3 [2.2; 2.5]; it is reliably higher than in asthenic and normosthenic types (1.2 [0.9; 1.3] and 1.2 [1.1; 1.4] µm correspondingly within the interquartile range Р_25-75).

For men of asthenic type, the common features are the even structure of menisci, smooth perichondrium, absence of hypertrophied chondrocytes and their stable diameter at different levels of a section (11.33 [11.17; 11.98] µm – the anterior horn, 12.10 [11.63; 12.31] µm – the body and 12.15 [11.33; 12.3] µm – the posterior horn). At the same time, there is a statistically reliable difference in amount of chondrocytes and amount of isogenous groups of chondrocytes inside the somatotypical group (the table 3, Fig. 4). Amount of chondrocytes is 15.4 [14.25; 15.9] at the level of the anterior horn of meniscus that is reliably higher than at the level of the body and the posterior horn (12.2 [9.45; 13.5] and 13.4 [12.75; 14.05] correspondingly within the interquartile range Р_25-75). From other side, the amount of isogenous groups of chondrocytes at the level of the anterior horn presents the minimal value as compared to other levels (p < 0.05) and is 0.5 [0.45; 0.65] for the value of this parameter 1.0 [0.8; 1.25] at the level of the body and 1.2 [0.9; 1.3] at the level of the posterior horn.

Figure 4

Hyaline cartilage tissue of the posterior horn of medial meniscus of the right knee joint in a man of asthenic type. Hematoxylin and eosine staining. Magnification × 400. 1 – isogenous group of chondrocytes, 2 – a single chondrocyte

Table 3

Histological characteristics of knee menisci in the med of different body composition according to W.L. Rees – Н.J. Eysenck (n = 84)

Parameter	Examination level	Asthenic type  (n1 = 28)	Normosthenic type (n2 = 24)	Pyknic type (n3 = 32)	p level
1	2	3	4	5	6
Mean diameter of chondrocytes (µm)	Anterior horn of meniscus	11.33 [11.17; 11.98]	11.60 [11.44; 11.97]	11.55 [11.35; 11.86]*
	Meniscus body	12.10 [11.63; 12.31]	12.41 [11.66; 12.75]	12.48 [11.64; 12.58]*
	Posterior horn of meniscus	12.15 [11.33; 12.3]	12.44 [11.61; 12.67]	13.08 [12.77; 13.25]*	р3-5,4-5 < 0.05
Amount of single cells (c.u.)	Anterior horn of meniscus	15.4 [14.25; 15.9]*	15.3 [13.15; 15.05]	15.7 [13.5; 15.3]*
	Meniscus body	12.2 [9.45; 13.5]*	13.7 [12.7; 14.1]	13.2 [11.85; 13.7]*
	Posterior horn of meniscus	13.4 [12.75; 14.05]*	13.4 [13.1; 14.05]	11.1 [10.3; 11.6]*	р3-5,4-5 < 0.05
Amount of isogenous groups of chondrocytes (c.u.)	Anterior horn of meniscus	0.5 [0.45; 0.65]*	1.1 [0.55; 1.2]	1.3 [0.6; 1.7]*
	Meniscus body	1.0 [0.8; 1.25]*	1.2 [1.15; 1.5]	1.8 [1.2; 2.05]*
	Posterior horn of meniscus	1.2 [0.9; 1.3]*	1.2 [1.1; 1.4]	2.3 [2.2; 2.5]*	р3-5,4-5 < 0.05

Note: * – differences are statistically reliable for comparison of values of parameters of different examination levels in the somatotype group (p < 0.05).

The histological structure of male menisci in normosthenic men has a few differences from the structure of menisci in men of hynecomorphic type (Fig. 5). The only difference is that all morphometric parameters of menisci have not any statistically reliable differences at different levels of histological examination (the table 3). The mean value of diameter of chondrocytes is within 12.41 [11.66; 11.75] µm (meniscus body); amount of chondrocytes within 13.7 [12.7; 14.1] (meniscus body); amount of isogenous groups – 1.2 [1.15; 1.5].

Figure 5

Hyaline cartilage tissue of the posterior horn of medial meniscus of the right knee joint in a man of normosthenic type. Hematoxylin and eosine staining. Magnification × 400. 1 – isogenous group of chondrocytes, 2 – a single chondrocyte  

CONCLUSION

Therefore, the study confirms the presence of age features of histological structure of menisci and proves the fact that the constitutional features of the human influence on microstructure of knee menisci at different levels. The menisci in men of pyknic type, in contrast to other body types, are exposed to structural changes in histological picture at the level of the posterior horn, with predominant amount of isogenous groups of chondrocytes in minimal amount of chondrocytes with maximal diameter. Men of asthenic type are characterized by the increase in amount of single cells with minimal number of isogenous groups of chondrocytes at the level of the anterior horn of menisci in comparison with other parts of meniscus.

 

Information on financing and conflict of interests

The study was conducted without sponsorship.

The authors declare the absence of clear or potential conflicts of interests relating to publishing this article.