Background and purpose RSA can be used for early detection of unstable implants. We assessed the micromotion of the Mobility Total Ankle System over 2 years, to evaluate the stability of the bone-implant interface using radiostereometric analysis measurements of longitudinal migration and inducible displacement.Patients and methods 23 patients were implanted with the Mobility system. Median age was 62 (28–75) years and median BMI was 28.8 (26.0–34.5). Supine radiostereometric analysis examinations were done from postoperatively to the 2-year follow-up. Standing examinations were taken from the 3-month to the 2-year follow-up. Migrations and displacements were assessed using model-based RSA software (v. 3.2).Results The median maximum total point motion (MTPM) for the implants at 2 years was 1.19 (0.39–1.95) mm for the talar component and 0.90 (0.17–2.28) mm for the spherical tip of the tibial component. The general pattern for all patients was that the slope of the migration curves decreased over time. The main direction of motion for both components was that of subsidence. The median 2-year MTPM inducible displacement for the talar component was 0.49 (0.27–1.15) mm, and it was 0.07 (0.03–0.68) mm for the tibial component tip.Interpretation The implants subside into the bone over time and under load. This corresponds to the direction of primary loading during standing or walking. This statistically significant motion may become a clinically significant finding that would correspond with premature implant failure.

Background: The goal of this study was to design a RSA marker insertion protocol to evaluate the stability of the bone-implant interface of a TAA prosthesis, and to validate that this marker insertion protocol can be combined with MBRSA technology to provide clinically adequate precision in assessing the micromotion of the TAA prosthesis. Methods: The Mobility™ Total Ankle System was used in this study. A marker placement protocol was developed with a Phantom Protocol. The Improved Marker Placement Protocol was used in 20 patients. Postoperative RSA double exams were taken. Condition Numbers (CN) were used to assess the marker distribution. The system precision was defined as the standard deviation of the double exams (MTE, MRE). MBRSA software was used to evaluate the double exams. Results: The RSA marker insertion technique for the 20 in vivo cases provided satisfactory results. CNs in all subjects but one were below 50 mm−1 and implied a desirable marker configuration. The tibial sphere MTE was 0.07 mm and the talar was 0.09 mm. The talar MRE was 0.51 degrees. Conclusion: The system precision for these in vivo TAA implants was within the normal range identified by RSA studies, and comparable to the existing TAA RSA studies. This study demonstrated a reliable RSA marker insertion technique in both the tibia and talus. The study confirms that the insertion and MBRSA technique allows the typical high precision demonstrated in other RSA studies

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BACKGROUND: Intrauterine bladder rupture is a rare complication usually caused by structural bladder outlet obstruction. Some medications are known to cause urinary retention or diuresis in fetuses and preterm infants. CASE: A 31-year-old gravida 6, para 3023 at 29 weeks and 2 days’ gestation required intubation, mechanical ventilation, and medical management for severe chest pain and respiratory failure, eventually diagnosed as asthma and pneumonia. An obstetrical ultrasound on hospital day three revealed a markedly dilated fetal bladder. Repeat ultrasound the following day showed a decompressed fetal bladder and significant ascites. A cesarean delivery was performed for a nonreassuring fetal heart rate. Postnatal evaluation by voiding cystourethrogram and cystoscopy revealed bladder rupture without evidence of outlet obstruction. Given the absence of other plausible causes, the rupture was likely due to exposure to maternal medications. CONCLUSION: Transplacental exposure to maternal medications may cause fetal urinary retention and intrauterine bladder rupture. Fetal ultrasound surveillance during treatment with medications known to cause urinary retention may allow for early diagnosis and intervention