DOI:10.2214/AJR.06.5039 Treatment of Sacral Insufficiency Fractures We read with interest the article by Butler et al. [1], and we wish to make the following comments. Our unit is a tertiary referral center for pelvic and acetabular injuries, and we treat operatively more than 100 sacral insufficiency fractures per annum. We are concerned with the conclusions drawn by Butler et al. for the following reasons: First, the period of follow-up evaluation was rather short for conclusive results. Second, there was no clear protocol of mobilization of these patients and we are surprised that no protective weight-bearing status was prescribed after the procedure in any of the patients. Third, pain is a rather subjective way of result validation; visual analogue scales to quantify pain, quality-of-life scores (i.e., SF-36 [Short Form 36], EuroQoL [European quality of life scale]), or consumption of pain medication may have provided more accurate grading of the results. Fourth, radiologic evaluation of fracture healing is not possible because of the interference of the polymethyl methacrylate (PMMA) cement and as a result postoperative radiographs or CT scans are difficult to interpret. Fracture healing is impaired by cement. How do the authors believe that healing of the fracture will take place? In the case of a sacral fracture, the socalled void-filling theory of vertebroplasty cannot be supported. It is difficult to believe that randomly and haphazardly put cement spikes that fill the osteoporotic and fractured sacral voids could biomechanically withstand the vertical forces of the torso. We suggest the following: First, biomechanical stability could be achieved with screw fixation (sacroiliac percutaneous screw fixation) without risking neurologic or vascular injury to the sacral foramens as can possibly happen with the uncontrolled injection of hot cement. Second, immobilization of the patient in a wheelchair for at least 4 weeks to allow time for healing and then partial mobilization to the limits of the expected residual pain, because healing of osteoporotic bones may last more than 2 months in the pelvic ring. Third, systemic treatment after the procedure with anticatabolic or anabolic bone-enhancing agents of choice of the treating clinician. Because a growing number of case reports are appearing in the literature regarding imagingguided percutaneous sacroplasty [1–4], we believe that input from the perspective of pelvic and acetabular orthopedic and trauma surgeons would optimize the best treatment strategy of these patients. We trust that our comments will be appreciated by the authors, and we look forward to their response. Eleftherios Tsiridis Peter V. Giannoudis St. James’s University Hospital Leeds LS9 7TF, UK