Assessment of Maxillary Distraction Forces in Cleft Lip and Palate Patients

Distraction osteogenesis is a process that depends on biomechanics, where the application of progressive traction forces leads to bone lengthening by gradual new bone formation. (Illizarov, 1989a, 1989b) Consequently, stretching of surrounding soft tissues occurs at different tissue depths, allowing correction of severe skeletal dysplasias in short periods of time. However, biomechanical data from the craniofacial distraction osteogenesis process is limited and the mechanical and biological nature of the traction forces involved is not fully understood (Gardner et al., 1997). Assessment of distraction forces within the structure being distracted may provide current information about the mechanical response and therefore conditions in the distracted structure, including, premature consolidation, device failure, or the existence of incomplete osteotomies (Aarnes et al., 1994, Younger et al., 1994). This assessment may further lead to improved understanding of the nature and biology of distraction, and help determine optimum rates and rhythms (Samchukov, 1998). Studies have been published on forces during distraction of the tibia and femur using instrumented external fixators in conjunction with micrometers or goniometers (Evans et al., 1988, Richardson et al., 1994, Aronson et al., 1994). Similar studies have been performed in animals (Gardner, 1998). However, the results obtained by these authors are extremely controversial. The great variability of distraction devices, complexity of methodology employed, site of distraction force application, and anatomical structure seem to dictate great influence. In the craniofacial area, only few studies have examined the distraction forces required to lengthen the mandible during distraction, even though measurements were performed indirectly through the measurement of torque necessary to perform the activation of the distractor (Robinson et al., 2001, Burstain et al. 2008). Recently, the authors have developed a simple mechanism to measure and adjust maxillary distraction forces during maxillary advancement (Suzuki & Suzuki, 2010). The mechanism was developed in order to allow direct assessment of distraction forces. Therefore, the purpose of the present study is to monitor the distraction forces applied through maxillary distraction osteogenesis in cleft lip and palate patients with this simple mechamism.