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Estudio morfometrico de los ligamentos colateral medial y oblicuo de la articulacion del codo en perros (Canis familiaris).

RESUMEN: El objetivo del trabajo fue describir, en 20 perros adultos (Canis familiaris) machos y hembras de iguales proporciones, los sitios de insercion de los ligamentos colateral medial y oblicuo de la articulacion del codo y su evaluacion morfometrica ademas de analizar los huesos (humero, radio y ulna) que forman parte de esta articulacion.

El ligamento colateral medial se divididio en porciones craneal y caudal, encontrandose que la porcion craneal es larga y estrecha, com valores medios de 3,30 + 0,36 cm de largo y 0,26 + 0,06 cm de ancho, y penetra en el espacio interoseo, fijandose en la superficie caudolateral proximal del radio. El ligamento oblicuo es capsular y tambien se divide en porciones craneal y caudal. La primera porcion se fija al borde medial proximal del radio y envuelve los tendones de insercion de los musculos braquial y biceps braquial, con valores medios de 2,94 + 0,30 cm de largo y 0,28 + 0,08 cm de ancho.

La porcion craneal del ligamento colateral medial y la porcion caudal del ligamento oblicuo se confunden, ocurriendo esto porque, probablemente, es una region que actua como un refuerzo para las estructuras ligamentosas adyacentes.

PALABRAS CLAVE: 1. Articulacion del codo; 2. Perro; 3. Ligamento oblicuo; 4. Ligamento colateral medial; 5. Morfometria.

MORPHOMETRIC STUDY OF THE MEDIAL COLLATERAL AND OBLIQUE LIGAMENTS OF THE ELBOW JOINT OF THE DOG (Canis familiaris)

SUMMARY: The objective of the present study was to describe the sites of insertion of the medial collateral and oblique ligaments of the cubital joint of the dog and to evaluate their morphometry, in addition to the bones (humerus, radius and ulna) involved in the joint. The study was conducted on 20 adult dogs (10 males and 10 females). The distal part of the medial collateral ligament is divided into cranial and caudal portions, with the caudal portion being long and narrow, with a mean length of 3.30 [+ or -] 0.36 cm and a mean width of 0.26 [+ or -] 0.06 cm. This portion penetrates the interosseous space and attaches to the proximal caudolateral surface of the radius. The oblique ligament is capsular, with a mean length of 2.94 [+ or -] 0.30 cm and a mean width of 0.28 [+ or -] 0.08 cm and caudally is also divided into cranial and caudal portions, with the former attaching to the proximal medial border of the radius, bypassing the tendons of insertion of the brachial muscle and biceps brachii muscle. The cranial portion of the medial collateral ligament and the caudal portion of the oblique ligament fuse together, representing a region that acts as a reinforcement for adjacent ligament structures.

KEY WORD: 1. Elbow joint; 2. Dog; 3. Oblique ligament; 4. Collateral medial ligament; 5. Morphometry.

INTRODUCTION

Ligaments are highly specialized structures that connect bones to one another, promoting stability of the joints and serving as guides for articular movement. There is also evidence that they play a sensorineural role in the dynamic information of the muscle (Bloomberg, 1995 and Benjamin & Ralphs, 1997).

Benjamin & Ralphs mentioned the existence of two types of ligaments: capsular, when the ligament is a local thickening of the articular capsule, or accessory when it is located free from the joint capsule, inside or outside the capsule.

The elbow is a compound joint in which the humeral condyle articulates with the head of the radius, the humeroradial joint, and with the semilunar notch of the ulna, the humeroulnar joint (Denny, 1987; Evans, 1993; Denny, 1993). The elbow joint is classified as a hinge type joint, only able to execute extension and flexion movements (Campbell, 1969; Denny, 1987 and 1993; Taylor, 1996). Campbell reported that the elbow joint is vulnerable to injury because of the small amount of soft tissues protecting it, the frequent rotational efforts to which it is submitted, and the fact that it is a joint of the hinge type that does not absorb vigorous impacts supported laterally or caudally.

The medial collateral ligament of dogs, also called medial radial ligament (Campbell), is thinner than the lateral collateral ligament (Sisson, 1996). It arises from the medial epicondyle of the humerus and passes deeply through the proximal part of the interosseous space, essentially ending on the caudal surface of the radius, slightly medially to the insertion of the lateral collateral ligament (Sisson). There is also a small insertion on the interosseous margin of the ulna (Sisson). Campbell and Vogelsang et al., (1997) described two portions of the medial collateral ligament in dogs: the cranial portion and the caudal portion. Evans mentioned that the caudal portion of the ligament is mainly fixed to the radius, but is also partially fixed to the ulna.

Campbell reported that the medial collateral ligament of the dog is located immediately below the junction of the pronator teres muscle and radial flexor muscle of the carpus, distally to their origins. This author also reported that a medial incision of the elbow joint extended to the antebrachial fascia permits the surgeon to locate the pronator teres muscle and radial flexor muscle of the carpus, and favors the approach to the medial collateral ligament after these structures are dissected.

In addition to the collateral ligaments, the elbow joint of the dog is composed of the annular ligament, olecranon ligament, and oblique ligament (Campbell; Denny, 1993 and Evans).

The oblique ligament represents a reinforcement of the articular capsule and therefore has not been named by the International Committee of Nomenclatura Anatomica Veterinaria (NAV,1994). Sisson reported that the articular capsule of the elbow is cranially reinforced by an oblique ligament that originates cranially to the lateral condyle of the humerus, close to the surface of the joint capsule and joins the terminal part of the biceps brachii muscle and brachial muscle distally.

Evans defined the oblique ligament as a small bundle of fibers in the articular capsule, which arises from the dorsal margin of the supratrochlear foramen and crosses the elbow joint distally and medially to the tendons of the biceps brachii muscle and brachial muscle, and at the level of these tendons the oblique ligament divides into two parts: cranial and caudal portions.

In traumatic elbow luxations, the orientation of the oblique and olecranal ligaments causes a lateral luxation to be more probable than a medial luxation. The latter, in addition, depends on another preponderant factor such as the considerably larger size of the medial condylar surface of the humerus compared to the lateral condyle (Taylor).

According to Van Pelt (1962), the study of the anatomy and physiology of the joints contributes to the treatment of articular diseases since knowledge of the sites of fixation of ligament components is essential for surgeons to repair or reconstruct these structures (Vogelsang). On this basis, in view of the above considerations, the objective of the present study was to describe the morphometry of the oblique and medial collateral ligaments of the dog's elbow with emphasis on their anatomical aspects.

MATERIAL AND METHOD

In the present study we used 20 adult medium-sized mongrel dogs (10 males and 10 females) donated by the Veterinary Hospitals of the Jaboticabal and Botucatu Campuses of Unesp, SP, Brazil. Sex, age, weight, and length from the nuchal crest to the joint between the first and second coccygeal vertebra were recorded, corresponding to the data indicative of the general characteristics of the dogs used.

The right and left thoracic limbs were then separated from the animal's body, some soft tissues (cutaneous and muscular) and some bones (scapula, bones of the carpus and metacarpus, phalanges and sesamoid bones), while the parts consisting of the humerus, radius, ulna and the ligaments under study were maintained.

A Norfol pachymeter was used for the biometric measurements of the caudal portion of the medial collateral ligament and the cranial portion of the oblique ligament, and humerus, radius and ulna of the right and left thoracic limbs. The following parameters were evaluated:

Maximum length between the points of origin and insertion of the caudal portion of the medial collateral ligament (measured from the medial epicondyle to the caudolateral surface of the proximal portion of the radius) and cranial portion of the oblique ligament (measured from the articular capsule in the region of the lateral condyle of the humerus to the proximal and medial margin of the radius).

Maximum lateromedial width of the caudal portion of the medial collateral ligament and cranial portion of the oblique ligament.

Bone length, as follows:

Humerus: from the greater tubercle to the capitulum of the humerus,

Radius: measured from the articular circumference to the styloid process of the radius.

Ulna: measured from the olecranon to the styloid process of the ulna.

Lateromedial width of the proximal epiphysis and distal width of the humerus, radius and ulna, using the olecranon as the reference parameter.

The numerical data obtained were analyzed statistically using variance analysis.

RESULTS

Age, body weight and length, reported as means [+ or -] SD, were 2.80 [+ or -] 1.91 years, 18.39 [+ or -] 3.44 kg and 61.55 [+ or -] 1.70 cm, respectively.

The medial collateral ligament had the appearance of a dense whitish ribbon that started wide in the medial epicondyle of the humerus and divided distally into a cranial and acaudal portion (Fig. 1A). The cranial portion is short and fuses with the articular capsule and with the caudal or short portion of the oblique ligament. The caudal portion is longer and narrower and penetrates the interosseous space, attaching to the proximal caudolateral surface of the radius caudally to the insertion of the cranial portion of the lateral collateral ligament. The entire ligament rests on an adipose pad. Biometric data were collected from the medial epicondyle to the insertion of the caudal portion of the ligament (Table I). The cranial portion was not measured due to its continuity with the caudal of short portion of the oblique ligament.

[FIGURE 1 OMITTED]

The oblique ligament is a thin whitish structure presenting as a cranial reinforcement of the articular capsule (Fig. 1B). It originates from the articular capsule in the region of the lateral condyle of the humerus, it crosses obliquely the cranial surface of the elbow joint and divides into cranial of long and caudal or short portions close to the annular ligament. The cranial portion attaches to the proximal medial border of the radius, bypassing the tendons of insertion of the brachial muscle and biceps brachii muscle, and the caudal portion fuses with the cranial portion of the medial collateral ligament, this being the reason why biometric data were obtained only for the cranial portion of the oblique ligament (Table I). The adipose pad is located close to regions of insertion.

As shown in Table I, the medial collateral ligament was significantly longer than the oblique ligament (p<0.01) although the two ligaments did not differ significantly in width (p>0.05). Also, no significant differences were observed in terms of antimers or sex (p>0.05).

Table II shows the biometric values for the bones involved in the elbow joint of the dogs studied in the present investigation.

In a comparative study of the antimers (right and left), significant differences (p<0.01) were observed in the length and width of the distal epiphysis of the humerus due to the homogeneity of the absolute values. There were no significant differences between sexes in terms of the biometric data for the bones composing the humero-radial-ulnar joint. Interaction between sexes and limbs was also observed for length (p=0.0422) and for the distal epiphysis of the radius (p=0.0192).

We calculated correlations for all the data studied and, in the medial collateral ligament, we observed positive and significant correlations between ligament length and ligament width and all the biometric data for the bones, except for the width of the proximal epiphysis of the ulna. There was no correlation between this characteristic and animal age of weight. The width of the medial collateral ligament was positively and significantly correlated with the biometric data for the bones involved in the elbow joint, but not with animal age, weight or length. The same was observed for the correlation between animal length and bone biometric data, which was positive and significant, except for the width of the distal epiphysis of the ulna.

Analysis of the correlation of length of the oblique ligament with all the data studied revealed that there was a positive and significant correlation between animal length and all the biometric data for the bones of the elbow joint. In contrast, the width of the same ligament was positively and significantly correlated with animal weight and with the biometric data for the bones, except for bone length. Similarly, animal length was correlated with the biometric data for the bones, except for the width of the distal epiphysis of the ulna. All the biometric data for the bones were positively and significantly correlated per se, i.e., with one another.

DISCUSSION

Morphophysiologic analysis of the medial collateral and oblique ligaments of the humero-radial-ulnar joint demonstrated that these ligaments have an important function in the process of static and dynamic union of these bone parts. The medial collateral ligament had the aspect of a wide ribbon in the initial portion and divided distally into cranial and caudal portions. Vogelsang et al. mentioned that the cranial portion is indistinct and seems to be just a slight thickening of the articular capsule, attaching to the proximal medial surface of the radius. It fixes in association with the articular capsule, the oblique ligament and the radial insertion of the tendon of the biceps and brachial muscle.

The caudal portion of the medial collateral ligament is longer and narrower and penetrates the interosseous space, attaching to the proximal caudolateral surface of the radius caudally to the insertion of the cranial portion of the lateral collateral ligament. The entire ligament rested on an adipose pad, as also observed by Vogelsang et al.

The distal insertion of the medial collateral ligament mainly occurs in the ulna in felids (Acinonyx jubatus) (Kunzerl & Probst, 1998), in contrast to what was observed in the caudal portion of this ligament in the dogs studied here. In buffaloes (Bos bubalis) the medial collateral ligament is a strong, wide and thick ligament also composed of white fibers and is fixed to a small tuberosity in the medial epicondyle, ending in the medial tuberosity of the radius. Few fibers are fixed at the level of the proximal radio-ulnar interosseous space (Singh & Johari, 1972).

In the present study we observed that the distal fixation of the caudal portion of the medial collateral ligament of the elbow joint occurred mainly in the proximal caudolateral region of the radius and only a few fibers were loosely fixed to the ulna. This observation supports the idea that the greatest load and support of body weight are transmitted to the humero-radial joint, in detriment of the humero-ulnar joint, which is reserved for elbow stability on the sagittal plane (Denny, 1987; Denny, 1993; Komtebedde & Vasseur, 1993).

With respect to the morphometric data, the measurements made here for the medial collateral ligament were proportional to those reported by Vogelsang et al. for dogs. The mean weight of the dogs used here was lower than that of the dogs studied by Vogelsang et al., suggesting that our dogs were smaller and therefore obviously had shorter mean ligament lengths. According to the same authors, there was a significant difference between sexes (P>0.03), a fact that was not observed in our study (P=0.2144) with respect to the length of the medial collateral ligament.

The oblique ligament was found to be fine and whitish, appearing to be a cranial reinforcement of the articular capsule of the elbow. It originated from the anterior capsule in the region of the lateral condyle of the humerus, obliquely crossing the cranial surface of the elbow joint and dividing into a cranial or long portion and a caudal or short portion close to the annular ligament. The former was fixed to the proximal medial border of the radius, bypassing the tendons of insertion of the brachial muscle and biceps brachii muscle, and the latter fused with the cranial portion of the medial collateral ligament.

The data reported here are anatomically similar to those reported by Evans. When examining the distribution

of the adipose pad around this ligament, a greater concentration was observed in the regions of insertion, probably in order to reduce attrition between the ligament and the bone structure and consequently favor the sliding of the bone pieces and muscle of this region, a fact not previously described.

The medial collateral ligament is classified as an accessory ligament because it is in a position free from the joint within the articular capsule, in agreement with the classification of Benjamin & Ralphs, and therefore can be classified as a capsular ligament.

The major function of articular ligaments is to prevent excessive of abnormal movements of the joints, but the ligaments also maintain the stability of these joints through their proprioceptive function (Benjamin & Ralphs). The stabilizing function of these ligaments in the dog's elbow joint was actually observed, and the last proposition could be deduced from this last statement.

Histological, biomechanical and ultrastructural studies will be performed to better determine the importance and function of the medial collateral and oblique ligaments, in order to contribute to the diagnosis and treatment of affections involving these structures and the cubital joint of the dog, in general.

ACKNOWLEDGEMENT

We would like to thank the Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) and Fundacao para o Desenvolvimento da UNESP (FUNDUNESP) for the financial support of this research, and Nilton Araujo for the technical assistance.

Received : 26-11-2002

Accepted : 06-03-2003

REFERENCES

Benjamin, M. & Ralphs, J. R. Tendons and ligaments--an overview. Histol. & Histopathol., 12:1135-44, 1997.

Bloomberg, M.S. Tendon, muscle and ligament injuries and surgery. In: Amstead, M.L. Small animal orthopedics. St. Louis, Mosby, 1995.

Campbell, J.R. Nonfracture injuries to the canine elbow. JAVMA, 155(5):735-44, 1969.

Denny, H.R. The canine elbow. British Vet. J., 143(1): 1-20, 1987.

Denny, H.R. The forelimb. In: Denny, H.R. A guide to canine and feline orthopaedic surgery. 3 ed. Oxford, Blackwell Scientific, 1993.

Evans, H.E. Ligaments and joints of thoracic limb. In: Evans, H.E. Miller's Anatomy of the dog. 3 ed. Philadelphia, Saunders, 1993.

Komtebedde, J. & Vasseur, P. B. Elbow luxation. In: Slatter, D. Textbook of small animal surgery. 2 ed. Philadelphia, Saunders, 1993.

Kunzerl, W. & Probst, A. Anatomische besonderheiten am ellbogengelenk des geparden (Acinonyx jubatus). Anat. Hist. Embryol., 27(3): 167-72, 1998.

NAV--Nomenclatura Anatomica Veterinaria. International Committee on Veterinary Gross Anatomical Nomenclature. International Committee on Veterinary Histological Nomenclature. International Committee on Veterinary Embriological Nomenclature. Nomina Anatomica Veterinaria. 4 ed. Nomina Histologica Veterinaria. 2 ed. Nomina Embriologica Veterinaria. New York, World Association on Veterinary Anatomist, 1994.

Singh, A. & Johari, M.P. The medial ligament of elbow joint of buffalo (Bos bubalis L.). Current Sci., 41(16):606-7, 1972.

Sisson, S. Articulacoes do carnivoro. In: Getty, R. Anatomia dos animais domesticos. 5 ed. Rio de Janeiro, Guanabara Koogan, 1996.

Taylor, R.A. Tratamento das luxaq6es do cotovelo. In: Bojrab, M. J. Tecnicas atuais em cirurgia dos pequenos animais. 3 ed. Sao Paulo, Roca, 1996.

Van Pelt, R.W. Anatomy and physiology of articular structures. Veterinary Medicine, 57:135-43, 1962.

Vogelsang, R. L.; Vasseur, P.B.; Peauroi, J.R.; Kass, R.H. & Sharley, N. Structural, material and anatomic characteristics of the collateral ligaments of the canine cubital joint. Am. J. Vet. Res. 58(5):461-6, 1997.

* Daniela Oliveira; * Silvana Martinez Baraldi Artoni; ** Antonio Marcos Orsi & * Anita Isabel Roque Rodriguez

* Laboratory of Anatomy, Department of Animal Morphology and Physiology, Faculty of Agrarian and Veterinary Sciences of Jaboticabal/UNESP, Brazil.

** Department of Anatomy, Institute of Biosciences, UNESP/Botucatu, Brazil.

* Financial support by Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), Brazil.

Correspondence to:

Prof. Dra. Silvana Martinez Baraldi Artoni

Laboratory of Anatomy

Department of Animal Morphology and Physiology

Faculty of Agrarian and Veterinary Sciences of Jaboticabal/UNESP--Rod. de Acesso Paulo Donato Castellane, Km 5, s/n.

CEP 14883-900

Jaboticabal

BRAZIL

E-mail: smbart@fcav.unesp.br
Table I. Mean (+ SD, cm), median and percentiles and P value
of the length and width of the medial collateral and oblique
ligaments of the elbow joint of the dog (Canis familiaris).
Number of animals = 20.

                Ligament medial collateral

           Mean [+ or -] SD     Median (10%, 90%)

Length     3.3 [+ or -] 0.36     3.2 (2.8;3.75)
Width     0.26 [+ or -] 0.06     0.3 (0.2;0.30)

                     Ligament oblique

           Mean [+ or -] SD     Median (10%, 90%)    p Value

Length    2.94 [+ or -] 0.29      3.0 (2.5;3.3)      0.0001
Width     0.28 [+ or -] 0.08      0.3 (0.2;0.4)      0.1630

SD=standard deviation

Table II--Mean (+ SD, cm) lengths and widths of the proximal
and distal epiphyses of the bones of the elbow joint of the
dog (Canis familiaris). Number of animals = 20.

                      Variable                 Mean [+ or -] SD

Humerus    Length                             14.82 [+ or -] 1.06
           Width of the proximal epiphysis     2.54 [+ or -] 0.24
           Width of the distal epiphysis       2.84 [+ or -] 0.23

Radius     Length                             14.75 [+ or -] 1.32
           Width of the proximal epiphysis     1.62 [+ or -] 0.13
           Width of the distal epiphysis       1.98 [+ or -] 0.21

Ulna       Length                             17.26 [+ or -] 1.56
           Width of the proximal epiphysis     1.04 [+ or -] 0.15
           Width of the distal epiphysis       0.36 [+ or -] 0.08

SD=standard deviation
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Author:Oliveira, Daniela; Baraldi Artoni, Silvana Martinez; Marcos Orsi, Antonio; Roque Rodriguez, Anita Is
Publication:International Journal of Morphology
Date:Mar 1, 2003
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