Effect of vascularity on canine distracted tibial callus consolidation

Reamed Intramedullary Nailing has an Adverse Effect on Bone Regeneration During the Distraction Phase in Tibial Lengthening

BACKGROUND

The lengthening over nail (LON) technique has gained popularity because it enables shorter periods of external fixation, prevents deformities during lengthening, and reduces the risk of refracture after removal of the frame compared with the classic Ilizarov method. However, it is not clear if the violation of endosteal blood supply by reamed intramedullary nailing in the LON technique has a negative effect on bone regeneration or a positive effect by compensatory enhancement of periosteal circulation.

QUESTIONS/PURPOSES

The purposes of this study were to (1) compare the amount of regenerate bone during the distraction phase between two tibial lengthening techniques, the LON technique and lengthening and then nail (LATN) technique; and (2) compare callus shape at the end of the distraction phase using the classification of Li et al.

METHODS

This is a retrospective study comparing two treatment groups. Between September 2011 and June 2013, 120 patients underwent bilateral lower leg lengthening for familial short stature with either the LON or LATN technique, and were considered potentially eligible for inclusion in this retrospective, comparative study. During this same period, LON and LATN techniques were used in other patient populations, but all patients with familial short stature were considered for inclusion in the study. The specific contraindications for LON were diameter of the isthmus of the tibia narrower than 8 mm, length of the tibia shorter than 270 mm, and alignment of the lower extremity in valgus; in patients without these specific contraindications to LON, patients were offered either LATN or LON after counseling regarding the advantages and disadvantages of each procedure. The proposed advantages of LATN were shorter healing index and more stable internal fixation which might lead to earlier full weightbearing, whereas proposed disadvantages were a greater chance for deep infection, more deformity during lengthening, and subsequently longer external fixator period for correction. The groups were comparable in terms of age, sex distribution, smoking history, BMI, distraction rate, and final length gain. A longer period of external fixation was necessary in the LATN group, related to the relative stability of the segment without an intramedullary nail. Patients with tibial lengthening with the LON technique (31 patients, 62 tibiae) were compared with patients who had the LATN technique (89 patients, 178 tibiae) regarding the amount of bone regeneration at the anterior, posterior, medial, and lateral cortices of the lengthened area for each at 4, 8, and 12 weeks postoperatively using a pixel value ratio method. In addition, both groups were compared for callus shape and type at the end of the distraction phase (LON, 3.4 ± 0.06 months; LATN, 4.2 ± 0.05 months).

RESULTS

The pixel value ratios of the anterior, posterior, medial, and lateral cortices in the LON and LATN groups were 0.78 ± 0.06 and 0.74 ± 0.05; 0.82 ± 0.08 and 0.76 ± 0.05; 0.75 ± 0.06 and 0.72 ± 0.05; and 0.85 ± 0.06 and 0.82 ± 0.06, respectively at 4 weeks postoperatively(p value > 0.500 for all); 0.75 ± 0.05 and 0.77 ± 0.04; 0.78 ± 0.05 and 0.89 ± 0.04; 0.73 ± 0.05 and 0.82 ± 0.05; and 0.78 ± 0.06 and 0.88 ± 0.03, respectively at 8 weeks postoperatively (p value < 0.001 for the posterior, medial, and lateral cortices); 0.72 ± 0.05 and 0.76 ± 0.03; 0.75 ± 0.07 and 0.89 ± 0.03; 0.71 ± 0.05 and 0.82 ± 0.03; and 0.78 ± 0.06 and 0.91 ± 0.03, respectively at 12 weeks postoperatively (p value < 0.001 for the posterior, medial, and lateral cortices). A greater percentage of tibiae having the generally favored fusiform-shaped callus were seen with the LATN technique (61 of 178 segments) than with the LON technique (four of 62 segments; p < 0.001). There were no tibia showing the inferior concave, lateral, or central-shaped callus with the LATN technique, whereas eight tibiae (eight of 62 segments) showed concave-shaped callus with the LON technique (p < 0.001).

CONCLUSIONS

The potentially negative effect on callus regeneration from the concomitant use of reamed intramedullary nailing during the LON technique should not be overlooked. Based on our study, LATN may be a better choice for patients willing to accept the longer period of external fixation.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Cysteine-rich matricellular protein improves callus regenerate in a rabbit trauma model

PURPOSE

Open fractures with severe soft-tissue trauma are predisposed to poor bone healing. The vital coupling between osteo- and angiogenesis is disturbed. Cysteine-rich protein 61 (CYR61) is an angiogenic inducer promoting vascularisation. However, little is known about the effect of CYR61 on the callus regenerate after acute musculoskeletal trauma. Therefore, our aim was to determine whether local administration of CYR61: (1) has an influence on callus formation and remodelling, (2) increases bone volume and (3) partially restores callus stability.

METHODS

A musculoskeletal trauma was created in 20 rabbits. To simulate fracture-site debridement, the limb was shortened. In the test group, a CYR61-coated collagen matrix was locally applied around the osteotomy. After ten days, gradual distraction was commenced (0.5 mm/12 h) to restore the original length. New bone formation was evaluated histomorphometrically, radiographically and biomechanically.

RESULTS

Osseus consolidation occured in all animals. Average maximum callus diameter was higher in the test group [1.39 mm; standard deviation (SD) = 0.078 vs 1.26 mm (SD = 0.14); p = 0.096]. In addition, bone volume was higher (p = 0.11) in the test group, with a mean value of 49.73 % (SD = 13.68) compared with 37.6 % (SD = 5.91). Torsional strength was significantly higher (p = 0.005) in the test group [105.43 % (SD = 31.68 %) vs. 52.57 % (SD = 24.39)]. Instead, stiffness of the newly reconstructed callus decreased (64.21 % (SD = 11.52) vs. 71.30 % (SD = 32.25) (p = 0.81)).

CONCLUSIONS

CYR61 positively influences callus regenerate after acute trauma, not only histologically and radiographically but also biomechanically, most probably by a CYR61-associated pathway.

Effect of recombinant human fibroblast growth factor-2 on bone formation in rabbit mandibular distraction models using beta-tricalcium phosphate

This study was designed to evaluate the effect of recombinant human fibroblast growth factor-2 (rhFGF-2) on the amount and period of new bone formation in rabbit mandibular distraction models using beta-tricalcium phosphate (beta-TCP) as a bone graft substitute. Sixteen male Japanese White rabbits were divided into the following four experimental groups: 1, distraction alone; 2, distraction with beta-TCP granules; 3, distraction with rhFGF-2 (25 microg/50 microL) injected into beta-TCP granules; and 4, distraction with rhFGF-2 (100 microg/50 microL) injected into beta-TCP granules. The bones were harvested at 4 weeks after the operation and examined using soft radiography, micro-computed tomography (micro-CT), and peripheral quantitative computed tomography (pQCT). The dissected mandibles were stained using the Villanueva bone staining method, and the amount of new bone formed, bioresorption of beta-TCP, and new blood vessel formation were morphometrically calculated using bone histomorphometry. Radiopaque areas were observed more frequently in the distracted area of groups 3 and 4. Micro-CT analysis revealed partial new bone formation in the central region of the distracted area in groups 3 and 4. pQCT analysis revealed increased bone mineral density in groups 3 and 4. Histomorphometric analysis revealed increased newly formed bone and blood vessel areas in groups 3 and 4. In group 4, the number of osteoclasts around the beta-TCP granules had significantly increased. The present findings suggested that the combined use of rhFGF-2 and beta-TCP reduced the treatment period for distraction osteogenesis and accelerated the formation of a new high-quality bone.