Changes in the ultimate load and static bone histomorphometery parameters during the fracture healing process of denervated rats with tibial fracture

Jun MIAO; Chunrong LIU; Qun XIA; Jidong ZHANG; Hongbin JIN

ABSTRACT

BACKGROUND:

Clinical observation demonstrates that accelerated fracture healing or lower limb heterotopic ossifications always occur in patients with paraplegia. It indicates that peripheral nervous system may play an important role in fracture healing process.

OBJECTIVE:

To observe bone histomorphometery parameter, callus formation and biochemical change during the process of fracture healing of unilateral lower limb denervated tibia.

DESIGN:

Self-control animal experiment.

SETTING:

Tianjin Hospital.MATERIALS Totally 36 six-month-old healthy male Wistar rats, with mean body mass of 210 g, were used in this experiment.

METHODS:

This experiment was carried out at Animal Experimental Center of Tianjin Hospital from March 2001 to March 2004. Denervated tibia fracture model and innervated tibia fracture model were made in the same rat. Animals were executed under anaesthetic status at week 2 and week 4 after fracture. Bilateral tibias were chosen to take radiografts.Biomachamical strength was measured and non-decalcification sections were prepared to perform bone histomorphometery observation.MAIN OUTCOME

MEASURES:

① Comparison of wet weight of bilateral tibias and callus of rats between two groups after fracture. ②X-ray plain film scoring. ③ Biomechanical testing of tibial samples. ④ Histomorphological observation of fracture healing

RESULTS:

① Wet weight of bilateral tibia and callus of rats in denervated group was much higher than that in innervated group at weeks 2 and 4 after fracture [(0.94±0.15) vs (0.76±0.14) g, (1.06±0.26)vs (0.81±0.10) g,P ＜ 0.05]. ②In X-ray plain film scoring, callus formation was significantly increased in denervated group (P ＜ 0.01). ③In biomechanical testing of three-point bending of tibial sample, callus intensity was significantly lower at weeks 2 and 4 after fracture in denervated group than in innervated group[ (9.88±8.49)vs ( 16.62±13.38 ) N, ( 12.77±7.55 )vs (20.19±10.60) N,P ＜ 0.05]. ④Bone histomorphometery showed that compared with innervated group, mineralized bone trabecula width of denervated group was significantly reduced (P ＜ 0.05), osteoid width was increased , osteoclast index and bone absorption area were significantly increased (P ＜ 0.05), and there were no significant difference of fibroblast index and bone formation area between two groups; Compared with innervated group, mineralized deposition rate in the denervated group was significantly reduced (P ＜ 0.05), the mature time of osteoid was elongated (P ＜ 0.05).

CONCLUSION:

Peripheral nervous system may play an important role during early and middle period of fracture healing. Intact innervation is essential for normal fracture healing.