Comparison of accordion maneuver with compression technique alone for the treatment of atrophic fracture nonunion: A rabbit model

OBJECTIVE The aim of this study was to compare the histological results of Accordion Maneuver (AM) with Compression Technique Alone (CA) in the treatment of atrophic fracture nonunion in a rabbit model. METHODS The study was performed on 91 male New Zealand rabbits aged six months, weighing 3.1 to 3.6 kg. The standardized models of atrophic nonunion with a 3-mm fracture were created in the tibias of rats. For the histomorphological study, 22 rabbits were randomly selected and sacrificed. The remaining 69 rabbits were divided into two groups based on the treatment technique: Group AM (n = 36) and Group CA (n = 33). The group AM was further randomly divided into four subgroups based on the amplitude and interval parameters: subgroup A1B1 (0 day, 4 mm; n = 9), subgroup A1B2 (0 day, 8 mm; n = 7), subgroup A2B1 (6 days, 4 mm; n = 10), and subgroup A2B2 (6 days, 8 mm; n = 10). A monolateral external fixator was employed in each group. Animals were sacrificed 6 weeks after the treatment, and bony healing was assessed both radiologically and histologically. The efficiency of bony healing was assessed using the bone content index, bone mineral density, and bone volume fraction indexes. RESULTS In X-ray and micro-computed tomography assessments, periosteal reaction was detected at the fracture site in all specimens. In group CA, sclerosis was observed at the ends of the fragments. Bony absorption, nonunion, and a little amount of island-like high density were also observed at the nonunion site. Among AM subgroups, sparse callus-like bone formation in A1B1 subgroup and a high density of callus connecting most parts of the gap and large amount of periosteal callus formation in A1B1 subgroup were observed. In A2B2 subgroup, the cortex was initially connected. No gap was observed, and the medullary cavity was recanalized. In histological analyses, the intermission of 0 day at rate of 8 mm was of the highest level of bony regeneration, and the intermission of 6 days at the rate of 4 mm was of the lowest level of bony regeneration (P < 0.05). CONCLUSION Based on the radiological and histological results obtained from the present study, AM seems to be more effective than CA in treating atrophic nonunion. AM can shorten the period of treatment. The interval of 0 day and an amplitude of 8 mm may be more proper for AM.