Quantitative Assessment of Regenerate Bone Maturation using the Pixel Value Ratio Following Distraction Osteogenesis: A Scoping Review

Aim and background:The objective assessment of regenerate bone maturation during distraction osteogenesis traditionally relied on expensive and impractical methods such as quantitative computerised tomography (qCT) and dual-energy X-ray absorptiometry (DEXA) scans.The pixel value ratio (PVR), derived from standard digital radiographs, has emerged as a cost-effective and reliable alternative for evaluating bone mineralisation.However, its clinical utility, particularly in determining the threshold for safe full weight-bearing (FWB), remains unclear.Methods: This scoping review was conducted according to PRISMA-ScR guidelines and the participants, concept, and context (PCC) framework, systematically identified and analysed human clinical studies published in English and involving the use of PVR in human subjects undergoing distraction osteogenesis.We carried out a systematic search of seven databases using relevant keywords.Results: Of 215 records, 22 studies met the inclusion criteria [21 retrospective, one randomised controlled trial (RCT)].Fourteen studies assessed extramedullary lengthening, six intramedullary, and two both.Ten focused on the tibia, four on the femur, seven on both, and one included the humerus.Sample sizes ranged from 12 to 125.Sixteen studies calculated PVR using adjacent cortices; only eight reported PVR at FWB, mostly between 0.85 and 0.94.Most did not report PVR at hardware removal.Pixel value ratio was the sole assessment tool in only three studies; complications related to regenerate bone were rarely discussed. Conclusion:The PVR has been primarily used as an adjunctive tool for assessing regenerate bone mineralisation during distraction osteogenesis.There is no standardised method for its calculation, and its role in guiding key clinical decisions, such as FWB initiation or hardware removal, remains limited.Clinical significance: The PVR is a cost-effective tool for assessing regenerate bone maturation, but inconsistent methods and unclear thresholds limit its clinical utility.Standardisation and prospective validation are needed to guide safe weight-bearing and hardware removal decisions.