Morphological and Morphometrical Studies on the Radius and Ulna of Indian Elephant ( Elephas maximus indicus )

Background: The fore and hind limbs of the elephant are arranged in an almost vertical position under the body, similar to a pillar or leg of a table rather than being in the angular position seen in many other quadruped mammals to support great weight. The aim of this study was to elucidate the morphological and morphometrical outline on the radius and ulna in Elephants, thereby making more contribution in filling the gap of knowledge and skills framework in this field. Methods: For the present study, the materials from three Indian elephants were used. Some of the specimens were available at the Department of Veterinary Anatomy, Mhow. Few skeletons were dug out from the ground which was buried from the last 5-10 years in the premises of college. Result: The radius was situated obliquely in the anterior aspect of forearm region. Radius had two extremities proximal and distal extremity and a shaft. The distal end of the radius was thick, flattened and slightly prismatic in shape. The ulna was more massive than radius. It had two extremities and a body.


INTRODUCTION
The elephant under the order of Proboscidea is a nonruminant herbivore, belonging to the family Elephantidae with two living genera and species of elephants, Elephas maximus of Southern Asia and Loxodonta Africana of Africa (Nowak, 1999).The Asian elephants are subdivided into three different subspecies: Elephasmaximusmaximus of Sri Lanka, Elephas maximus indicus of India and Elephas maximus sumatranus of Sumatra (Shoshani and Eisenberg, 1982).As the elephant is the largest living terrestrial mammal, the feet have to carry an enormous weight and hence feet are probably one of the most important parts of its body.Many numbers of captive Asian elephants suffer from numerous foot ailments as a result of being tethered in unhygienic surroundings and these conditions often aggravate due to negligence and lack of awareness regarding proper care and treatment among elephant keepers.Hence an observational study of the elephants of this region was warranted.
The purpose of this wo rk was to en hance the knowledge on elephant skeleton and the study on radius and ulna of Indian elephant will overcome the gap of knowledge in the comparative anatomy also.This study provides a baseline data for further vetero-legal, archaeological and clinical cases.

MATERIALS AND METHODS
For the present study material from three Indian elephants irrespective of sex were used.The permission for the specimen collection has been obtained from the Principal Chief conservator of forest and wildlife warden, Government of Madhya Pradesh, vide letter no 239/6998261 on dated 29.12.2020.

Morphological and Morphometrical Studies on the Radius and Ulna of Indian Elephant (Elephas maximus indicus)
(2016) in Asian elephant, Smuts and Bezuidenhout (1993) in African elephant, Gupta et al. (2015) in camel, Onwuama et al. (2021) in West African giraffe and Budras and Robert (2003) in bovines.The radius articulates proximally with humerus as described by Konig and Liebich (2006) in domestic animals and with the lateral aspect of anterior surface of ulna (Plate 1 and 2).Distally, it articulates with the radial and intermediate carpal bones and distal part of the medial surface of ulna.Radius has two extremities proximal and distal extremity and a shaft (Plate 1) in toto agreement with Ahasan et al. (2016) in Asian elephant, Smuts and Bezuidenhout (1993) in African elephant, Gupta et al. (2015) in camel, Onwuama et al. (2021) in West African giraffe, Getty (1975) in horse and Konig and Liebich (2006) in domestic animals.
The proximal extremity was smaller than the distal extremity as noted by Ahasan et al. (2016) in Asian elephant and Smuts and Bezuidenhout (1993) in African elephant.Talukdar et al. (2008) and Smuts and Bezuidenhout (1993) in African elephant, reviewed that the proximal extremity was triangular in shape and Choudhary et al. (2013) in chital observed it as an irregularly oval in outline.Damian et al. (2012) reported that the proximo-caudal articular surface was L shaped in the giraffe, while in the cow it was crescent shaped.
It was attached to the lateral aspect of anterior surface of the ulna in the prone position so that its proximal end was directed outward, and the distal end was directed inward (Plate 1) as reported by Mariappa (1986) in elephant calf.The proximal part of the radius was fused with the ulna but having a narrow articular facet towards the medial side.France (2009) reported that in antelope radius and ulna were fused.The articular surface of the proximal extremity was slightly saddle shaped which was crossed by sagittal ridge (Plate 2) while Damian et al. (2012) in giraffe reported widened proximal extremity with three glenoid surfaces sculpted on it.Onwuama et al. (2021) in West African giraffe noted a concave articular surface that blended with the notch.Gupta et al. (2015) in camel described that articular area was divided into a smaller medial and larger lateral part by a sagittal ridge.A prominent lip like projection the coronoid process was present on the anterior side (Plate 1) as reported by Getty (1975) in horse.The posterior part of proximal end was fused with the cranial surface of ulna, and it was extended upto the lateral aspect of the ulna at proximal end.The upper articular area of radius took part in the formation of both the concave articular areas with the ulna for articulation with the trochlea of humerus.Only the lateral part of proximal of radius was fused with the ulna, while the medial part was free.However, in one case the medial part was also fused with the ulnar part.
The distal end of the radius was thick, flattened same as reported by Smuts and Bezuidenhout (1993) in African elephant and slightly prismatic in shape and it was extended upto the lower extremity to form styloid process of radius on the medial side (Plate 1).Ahasan et al. (2016) reported that the processes styloideus radii was represented by two rough convexities separated from each other by a straight depression.Akers and Denbow (2008) mentioned that in ruminants the styloid process was at the distal extremity of the radius.The distal end was situated on the medial aspect of the ulna and forming the antero-medial part of this twin

Morphological and Morphometrical Studies on the Radius and Ulna of Indian Elephant (Elephas maximus indicus)
bone.The articular area of distal extremity was not fused with the articular area of ulna (Plate 1).Gupta et al. (2015) in camel noted that the ulna was completely fused with the radius in the distal extremity.Talukdar et al. (2008) in elephant reviewed that the distal extremity of the radius articulated with radial carpal.
The distal articular area was divided into two parts by a ridge for articulation with the radial and intermediate carpal bones (Plate 4).The smaller medial articular area was slightly convex and oval in shape which was articulating the radial carpal bone.The larger articular area was present on its lateral side for articulation with the major part of intermediate carpal.It was convexo concave in shape (Plate 3 and 4).However, three oblique articular facets on the distal extremity of radius was noted by Ingole et al. (2017) in sahiwal cows and Gupta et al. (2015) in camel.
The body was less developed and cylindrical in shape but Gupta et al. (2015) in camel noted that the slightly curved shaft was somewhat flattened cranio-caudally, Onwuama et al. (2021)in West African giraffe noted elongated linear shape.Konig and Liebich (2006) explained that in bovines radius was a rod-shaped bone which was relatively strong.The upper 1/3 rd part was quadrilateral in shape while the distal 1/3 rd part was prismatic in shape.Cranially it was slightly convex and smooth while caudally it was concave and rough.In the middle 1/3 rd part the lateral, cranial and medial surfaces were continuous.In the middle 1/3 rd part of medial surface of body a crest was present.Budras and Robert (2003) noted that in bovines the radius was flattened and relatively short.
In the present study, no significant difference was recorded in between right and left forearm bones of same animal as reported by Gupta et al. (2015) in camel.In the present study weight of radius and ulna was 13.43±0.49kg (Table 1).Sasan et al. (2016) in buffalo recorded this as 553.00±7.02g.

Ulna
The ulna was more massive i.e., heavier, larger and longer than radius (Plate 1) same as mentioned by Ahasan et al. (2016) in Asian elephant, Smuts and Bezuidenhout (1993) in African elephant, Gupta et al. (2015) in camel and Nurhidayat et al. (2015) in Sumatran rhino.However, Siddiqui et al., (2008) in black Bengal goat reported that it was ill developed and Onwuama et al. (2021) in west African giraffe noted it slimmer of the two bones.It was the important weight bearing bone of the forearm region same as reported by Lucy et al. (2018) in elephant.It had two extremities and a body same as reported by Ahasan et al. (2016) in Asian elephant, Smuts and Bezuidenhout (1993)

Morphological and Morphometrical Studies on the Radius and Ulna of Indian Elephant (Elephas maximus indicus)
in Asian elephant, Smuts and Bezuidenhout (1993) in African elephant, Budras et al. (2003) in bovines, Budras et al. (2009) in horse.The ulna was extended upto the distal extremity of the radius (Plate 1, 3 and 4), which was in agreement with the findings in cattle (Getty, 1975), camel (Gupta et al., 2015), west African giraffe (Onwuama et al., 2021)and ox (Frandson et al., 2009) and in disagreement with the findings of Getty (1975) and Frandson et al. (2009) in horse, where the ulna was fused with the proximal third of radius.Nurhidayat et al. (2015) in Sumatran rhino noted that the ulna was fused with radius, however still forming interosseus antebrachia proximal and distal spaces.
The proximal end of the ulna was well developed.It was prismatic in shape and forming the olecranon process of ulna (Plate 1 and 2), however Muhammad and Shahid (2000) noted quadrangular shaped olecranon in buffalo and Pawan and Suraj (1999) noted tuberous in Neel gai but Smuts and Bezuidenhout (1987) in dromedary noted a welldeveloped tuber olecrani which was slightly bifid and Budras and Robert (2008) in bovines noted that olecranon tuber was a crest with two tubercles.In the upper part of this process medial and lateral tuberosities were present.The posterior border was concaved and continued with the same border of the shaft of ulna (Plate 1).The medial surface was slightly convex while the lateral surface was slightly concave in contrast to Getty (1975) in cattle and horse, Siddiqui et al. (2008) in black Bengal goat and Choudhary et al. (2013) in chital.Rajani et al. (2019) in Indian Muntjac described that olecranon of ulna was grooved transversely and consisted of two prominences, the caudal one was being larger than cranial.
In the proximal extremity olecranon process was less developed in comparison to other large domestic animals (cattle, horse) and was extended slightly above the level of anconeal process, however Lucy et al. (2018) in elephant mentioned that olecranon tuberosity and anconaeus process were in the same level.The tuber olecrani was massive caudolaterally same as noted by Lucy et al. (2018) in elephant, Choudhary et al. (2013) in chital, Choudhary et al. (2015) in black buck and Bharti et al. (2020) blue bull.However, Nurhidayat et al. (2015) in Sumatran rhino noted that olecranon protrude to caudodorsal with large olecranon tuber widened to lateral and medial.Below the tuber olecrani the bone compressed bilaterally, and it continues a narrow caudal (margin) of the shaft border same as reported by Ahasan et al. (2016) in Asian elephant.
On both side of olecranon process the tuberosities were present.The tuberosity present on lateral side was thick but medial tuberosity was thin and much extended giving a deeper concave area with the body.Similarly, Ahasan et al. (2016) in Asian elephant reported that tuber olecrani was massive, especially caudolaterally.The olecranon was wide above and rough on its posterior aspect for muscular attachment was in agreement with Mariappa (1986) in elephant calf.A broad arched dorsal border of the olecranon process narrowed as described by Ahasan et al. (2016) in Asian elephant.The number of foramina were present on the anterior surface of the olecranon process same as described by Ahasan et al. (2016) in Asian elephant and Smuts and Bezuidenhout (1993) in African elephant.

Morphological and Morphometrical Studies on the Radius and Ulna of Indian Elephant (Elephas maximus indicus)
The shaft was thick plate as it runs entire length of radius before ending distally as the lateral styloid process (Plate 3 and 4) which was in agreement with Ahasan et al. (2016) in Asian elephant, Siddiqui et al. (2008) in black Bengal goat, and disagreement with the Getty (1975) in horse.Cranially the shaft was flattened, it was triangular in shape proximally and was quadrilateral in shaped distally.
The upper half part of the body of ulna was three sided i.e., prismatic in shape as elucidated in horse (Getty, 1975), chital (Choudhary et al., 2013), black buck (Choudhary et al., 2015) and blue bull (Bharti et al., 2020), having cranial, lateral and medial surfaces with lateral, medial and posterior borders.
The nutrient foramen was present in the medial border of the ulna at the place of proximal 1/3 rd but Smuts and Bezuidenhout (1993) in African elephant mentioned that the position of this foramen was variable.However, it was located on the cranial surface in horse Getty (1975) and it was not recorded in blue bull (Bharti et al., 2020), black buck (Choudhary et al., 2015).The medial surface was smooth and flattened, while the lateral surface was rough and slightly concave, and the anterior surface was more concave towards upper side and rough (Plate 1).The lower half part of the body was quadrilateral in shape having cranial, caudal, lateral and medial surfaces.The lateral, medial and caudal surfaces were smooth, while the cranial surface was rough.
The thin interosseous space was present lengthwise between radius and ulna (Plate 1).Ahasan et al. (2016) in contrast to the findings of Smuts and Bezuidenhout (1993) in African elephant in which this interosseous space was absent.However, proximal and distal interosseous spaces were noted in cattle (Getty, 1975) and camel (Gupta et al., 2015) but in the horse, only one proximal interosseous space was noted (Getty, 1975).Muhammad and Shahid (2000) noted that the groove present between two inter-osseous spaces of radius was deeper in buffalo in comparison with cow.Mahmud and Mussa (2016) noted that in black Bengal goat radius and ulna were in contact with each other by their ends but fused in most part and the interosseous space was narrow.
The distal extremity of ulna had articular facets for small part of intermediate, ulnar and accessory carpal bones (Plate 3) same as reported by Smuts and Bezuidenhout (1993) in African elephant.
The quadrilateral shaped distal extremity of the ulna was thick and more developed (Plate 3).The medial part of this end was articulated with the distal end of radius.This distal articular area was divided into two unequal parts by a prominent ridge.The medial part was smaller and fused with lateral articular part of radius and form a deep concave area for articulation with the intermediate carpal bone (Plate 3).On the lateral side a large concave articular area was present for articulation with the ulnar carpal bone (Plate 4).On the postero-lateral aspect a small articular area was present for articulation with the accessory carpal bone.This small articular area was separated by a faint ridge from the large lateral articular area on the posterolateral aspect (Plate 4).
Styloid process got a shape of lateral prominence (Plate 3 and 4) same as reported by Ahasan et al. (2016) in Asian elephant, Choudhary et al. (2013) in chital and Bharti et al. (2020) in blue bull and it was more prominent than the processus styloideus radiae.Similarly, Pawan and Suraj (1999) studied radius and ulna of neel gai and noted that the styloid process of ulna was more pronounced.In the distal part of ulna numerous foramina were present on just above the articular area in this bone.
The circumference at proximal end and distal end was 54.62±0.20 cm, 40.05±0.25 cm respectively same asAhasan et al. (2016) in Asian elephant noted this as 53 cm and 35 cm, respectively.
The length of olecranon and circumference of olecranon process was 18.93±0.35cm and 47.45±22 cm, respectively (Table 1).Ahasan et al. (2016) in Asian elephant noted this as 11 cm and 42 cm, respectively.Gupta et al. (2015) in camel reported this as 10±0.36cm and 17.5±0.54cm, respectively.The length and width of articular surface of proximal part of ulna was 11.9±0.0.61 cm and 8.17±0.26cm, (Table 1) respectively.Similar parameters reported by Ahasan et al. (2016) in Asian elephant were 9 cm and 16.5 cm, respectively.However Gupta et al. (2015) in camel reported that the width of articular surface was 7.5±0.17cm.

CONCLUSION
The ulna was more massive i.e., heavier, larger and longer than radius It was the important weight bearing bone of the forearm region.On both side of olecranon process the tuberosities were present.Styloid process got a shape of lateral prominence, and it was more prominent than the processus styloideus radiae.

Table 1 :
Various gross parameters of radius and ulna of fore limb in Indian elephant.