The effect of posterior distraction on vertebral growth in immature pigs: an experimental simulation of growing rod technique.
METHODS
Experimental study.


OBJECTIVE
The aim of this study is to evaluate the vertebral body growth under distraction forces in immature pigs treated with growing rod (GR) technique.


BACKGROUND
Distraction forces applied on growth plate of appendicular skeleton stimulate longitudinal growth. However, the effect of distraction forces on axial skeletal growth has not been fully investigated yet.


METHODS
Twelve 10-week-old domestic pigs were used in this experimental model to simulate GR technique. Four of them were lost during postoperative period because of deep wound infection. Cranially T12-L1 and caudally L4-L5 vertebrae were instrumented by pedicle screws bilaterally, while L2 and L3 were skipped. Distraction between pedicle screws was applied at index surgery. The rods were then lengthened twice in a month interval. All subjects were evaluated with anteroposterior and lateral spinal radiograph before surgery, after surgery, and at the final follow-up. The vertebral body heights of distracted segments (HD = L2 and L3) and control segments (HC = T9, T10 and T11) were measured. Average vertebral body heights and the increase percentage in the vertebral body heights were compared among control segments and distracted segments.


RESULTS
The preoperative vertebral body height was similar in 2 groups (preHC: 10.81 mm, n = 19, preHD: 11.27 mm, n = 16, P > 0.05). At the final follow-up, the average vertebral body height in distraction group was significantly higher than the control group (postHC: 17.03 mm, postHD: 18.58 mm, P < 0.05). The increase percentage in vertebral body height was higher in distracted segments, but there was no statistically significant difference between the 2 groups.


CONCLUSIONS
The vertebral growth continues during GR instrumentation. Distraction forces might stimulate also apophyseal growth of axial skeleton.
Yilmaz
Güney
G
Department of Orthopaedics and Traumatology, Hacettepe University, Ankara, Turkey.
Huri
Gazi
G
Demirkran
Gökhan
G
Dağloğlu
Kenan
K
Ozkan
Cenk
C
Alanay
Ahmet
A
Acaroglu
Emre
E
Yazici
Muharrem
M
D000818:Animals; D001863:Bone Screws; D004195:Disease Models, Animal; D016268:Internal Fixators; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000254:growth & development / Q000601:surgery*; D019857:Osteogenesis, Distraction / Q000379:methods*; D011859:Radiography; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000601:surgery; D013552:Swine; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000254:growth & development / Q000601:surgery*; D016896:Treatment Outcome