Effects of different internal fixations on callus content in tibial fracture healing of experimental rabbits: an analytic study with X-ray images

Zhiwei WANG; Yuesong WU; Guozheng QIAN; Wenliang WANG; Jianhua WANG; Bin XIAO

ABSTRACT

BACKGROUND:

Fracture healing occurrs by two ways healing by first intention and healing by second intention, with the latter one similar to natural healing process. It has been proved that only 37% tibial farcture can reach healing by first intention, even it is fixed with strong AO steel plate. Different materials for intramedullary fixation have different influences on callus formation and callus content in the process of fracture healing.

OBJECTIVE:

To explore the influences of different internal fixations on callus formation and content in the course of fracture healing analysis with X ray computer image.

DESIGN:

Randomized controlled trial

SETTING:

At the Department of Orthopeadics of Changhai Hospital Affiliated to the Second Millitary Medical University of Chinese PLA and the Experimental Animal Center of the Second Millitary Medical University of Chinese PLA.MATERIALS This study was carried out at the Experimental Animal Center and Orthopeadic Laboratory of the Second Millitary Medical University of Chinese PLA between March 2000 and July 2001. Totally 51New Zealand rabbits were randomly selected without gender limitation and divided, accccording to intermeduallry nails, into three groups with 17 rabbits in each group rectangle-shaped intramedullary nails (RIN), Ender's nails (END) and stainless steel plates (SPL) groups

METHODS:

Fracture models were succccesufly established on rabbits.And then intramedullary nails were fixed 2 mm below the border of left tibial and fibula without exopexy. Positve and lateral X-ray films of each operational tibia were obtained at postoperational 2,3,4,8,12 weeks.Three rabbits in each group were killed for callus observation with naked eyes, and the maximal callus diameter at different time points was measured. The X-ray films at different periods were read carefully and quanatatively analyzed with computor image analysis system (lAS). The difference was compared with the analysis of variance and SNK test.MAIN OUTCOME

MEASURES:

The maximal callus diameter was determined with X-ray image at different time points so as to calculate the corrssponding integral of callus grey level.

RESULTS:

Totally 51 rabbits were enrolled in this study, 6 missed the experiment because 4 died for diarrhea and other two has exposed bone due to local infection, and then two rabbits were derived from each group; thereby, data of 45 rabbits were subjecte to the final statistical to the epak at postoperational 8 weeks; it was the longest in RIN group of the same stage,followed by Ender group and SPL group [(11.24±0.38), (10.86±0.65), (8.12±0.36) mm at postoperatively 4 weeks; ( 13.56±0.88 ), (12.84±0.20), (10.52±0.68) mm at postoperatively 8 weeks; ( 12.66±0.65 ), ( 11.84±0.55 ), (9.68±0.27) mm at postoperatively 12 weeks]. The difference between RIN, Ender and SPL was statistically significant, but the difference between the former two was unobvigroup; at the same postoperational time point, the intergral of callus grey level was the highest in RIN group, followed by Ender group and SPL group (89.11 ± 1.05,86.42±3.12,47.28 ± 1.57 at postoperatively 4weeks;159.69 ±3.64,148.72 ±1.68,79.63 ±2.41 at postoperatively 8 weeks;192.46 ±4.96,186.53 ±1.84,107.34 ±2.37 at postoperatively 12 weeks),The difference between RIN, Ender and SPL was obvious and moreover,the difference between RIN and Ender was significant at 8th week.

CONCLUSION:

The callus content in RIN and Ender group were higher than that in SPL group at each postoperational time point, which benefited for fracture healing. Callus content examination is a traditional means for the judgement of fracture healing. It prossesses that properties of intuition and persicuity, reliability, simplicity and practicibility. Moreover, subjectivity could be avioided if used in combination with X-ray image analysis system, since the digital management can help judging not only callus content but also callus quality, which may provide guidance for clinical treatment.