Surgical Lengthening of the Mandible of a Bactrian Camel by Distraction Osteogenesis
A female Bactrian camel (Camelus bactrianus) suffered trauma to her lower jaw shortly after
birth due to the overenthusiastic attempts by her mother to get her to stand. She experienced extensive damage to the
lateral aspect of the rostral portion of the left mandible. Bone fragments were evident although the jaw was not
completely fractured. The wounds were debrided and sutured, and she was separated from her mother for hand-rearing. Her
subsequent development was normal except her mandible failed to grow as fast as her maxilla, presumably due to trauma to
the rostral growth center. As a result, by the time she had reached 2 yr of age her mandible was approximately 4 cm
shorter than the maxilla and her tongue protruded from the left side of her mouth. By 3 yr of age, brachygnathism had
increased to 5 cm and the camel was showing increasing problems in food prehension. She was referred to Ontario
Veterinary College for corrective surgery at the age of 3 yr 3 mo.
The camel, which weighed 477 kg, was anesthetized and her head was placed in dorsal recumbency.
Following standard preparation for aseptic surgery, the ventral surface of the ramus of each mandible was exposed at its
narrowest point, approximately 4 cm rostral to the first premolar. A custom-made distraction apparatus consisted of five
semicircular perforated aluminum alloy plates, held approximately 2 cm apart, on two 10-cm long threaded expansion bars.
Three of the plates were positioned caudal to the proposed osteotomy site, two rostrally. The plates were secured to the
mandible through attachment by locking nuts to four threaded Steinmann pins inserted perpendicularly into the
ventrolateral aspect of each ramus: two caudal to the osteotomy site and two rostral. One additional pin was inserted
centrally into the mandibular symphysis and affixed to the most rostral plate. The pins were threaded into, but not
through, the distal cortex. Once the device was secured to the mandible and stabilized, a cortical osteotomy of each
mandible was performed at the exposed sites. Two holes were drilled from the ventral aspect through the ramus of each
mandible to weaken the bone, and transection of the mandible was performed using an osteotome with care being taken to
minimize trauma to the gingiva, periosteum, and the medullary blood supply. The surgical wound was closed and, once the
device was considered stable, the camel was allowed to recover.
Following surgery, ceftiofur (Excenel, Upjohn Animal Health, Orangeville, Ontario L9W 3T3, Canada)
500 mg i.v. was given for 3 wk, and butorphanol (Torbugesic, Ayerst, Guelph, Ontario N1K 1E4) 240 mg i.m. b.i.d. was
given for 3 days. From the sixth postoperative day, the rostral segment of the mandible was advanced relative to the
caudal section 1 mm each day by rotating the threaded expansion bar one full turn on each side. A light bandage and a
waterproof vinyl bag applied over the device, provided protection, and insulation. At first the camel showed some
discomfort during the distractions but was soon highly cooperative. Localized infection was observed around several of
the rostral pins after 30 days. Staphylococcus aureus and Enterococcus faecalis were cultured from the
exudate. Topical treatment was combined with a second course of ceftiofur for 10 days. Daily 1-mm distractions were
continued for 40 days. Expansion of the device was evident by the separation of the semicircular plates along the
expansion bar. After about 35 days of expansion, a progressive bend was seen in the expansion bars and it was apparent
the apparatus was expanding more than the mandible. There was also some deviation of the mandible to the right side. The
camel again showed some discomfort during the daily distraction procedure. Although the distraction device had been
expanded 4 cm, the mandible had not lengthened to the same degree. Further expansion was not attempted due to limitations
in the length of the expansion bars, and the rapid healing of one mandible. Throughout the post-surgical period the camel
continued to eat, although she would only consume a cubed ration and refused hay.
Following completion of the expansion phase, the device was maintained but no further distractions
were performed for an additional 38 days. Eighty-five days postoperatively, radiography revealed adequate ossification of
the healing callus and the device was removed in two stages. One of the two sets of caudal pins and one of the rostral
sets were removed initially, without anesthesia. The remainder of the device was removed under anesthesia 27 days later,
112 days after the original surgery. The jaw had been lengthened approximately 1 cm.
Distraction osteogenesis is the process of new bone formation between bone segments that are
gradually separated by incremental traction.2 The process begins when a distraction force is applied to the
healing callus and continues as long as the distraction is continued. The distraction force applied to bone creates
tension in the surrounding soft tissues, initiating a sequence of changes termed distraction histogenesis.2
Although the principles of bone remodeling and lengthening have been familiar to surgeons for centuries, the science
behind distraction osteogenesis was not known, and complications including non-unions and delayed healing prevented
widespread acceptance of the procedure until the late 20th century.
The Russian surgeon Gavriil Ilizarov refined the technique in the 1950s with the use of circular
fixators which provide greater stability than the earlier linear versions. He is widely credited as the pioneer of this
procedure. The biologic principles he espoused: minimal disturbance of bone, a delay before distraction, consistent rate
(amount of expansion per day) and rhythm (number of distractions per day) of distraction, and the importance of the site
and the technique of osteotomy have been well accepted. Originally used for lengthening and correcting deformities of the
long bones, the technique has gained great popularity over the past 10 yr, particularly for the correction of
craniofacial bone deformities, including lengthening of the mandible.1,2
Typically the bone is separated by means of a low-energy osteotomy of the cortex preserving local
blood supply to both the periosteum and medullary canal. Following a 5-day period of latency to allow the formation of a
stable blood clot and granulation tissue, the ends of the bone are uniformly separated at a constant rate. Mechanical
tension promotes growth of the healing connective tissue faster than occurs with normal fracture healing through
increased blood supply at the fracture site, fibroblast hyperplasia and hypertrophy, alignment of the fibroblasts along
the axis of the direction of tension, and subsequent osteoblast proliferation and ossification. Optimum osteogenesis of
long bones occurs at a distraction rate of 1 mm/day.1-3 Distraction is continued for a period of approximately
6 wk, or less if the desired correction has been achieved. After distraction ceases, the device is left in place for an
additional period to allow the fibrous callus to ossify completely.
In animals, besides its widespread use in laboratory animals for experimental purposes, the technique
has been used to correct long bone deformities in horses and dogs, and for jaw lengthening in horses.3 Our
experience has shown that the technique is applicable to zoo animals provided they tolerate the external fixator and the
daily manipulation of the device during the distraction period. In this case we were aided by the camel's exceptional
disposition. Unfortunately, the degree of lengthening achieved was not as much as desired. This is likely due to more
rapid ossification of the osteotomy site than expected. Although there was some improvement in her ability to eat, she
still eats slowly and her appearance was not changed significantly. In retrospect it may have been necessary to increase
the rate and/or rhythm of the distractions.
1. Aronson J. 1999. Principles of distraction osteogenesis. In: McCarthy, J. G. (ed.).
Distraction of the Craniofacial Skeleton. Springer, New York, New York. Pp. 51-66.
2. Samchukov ML, AM Cherkashin, J B Cope. 1998. Distraction osteogenesis: origins and
evolution In: McNamara, J. A. and C. Trotman. 1997. Distraction Osteogenesis and Tissue Engineering. 24th Annual
Moyers Symposium, Ann Arbor, Michigan. University of Michigan, Ann Arbor, Michigan.
3. Welch RD, DD Lewis. 1999. Distraction osteogenesis. Vet. Clin. North Am. Small Anim.
Pract. 29: 1187-1205.