Occult periprosthetic fractures of the acetabulum in THA using an elliptic cup design have no adverse impact on outcome.

Occult periprosthetic fractures have been defined as a fracture only visible on postoperative CT scans but not on postoperative plain radiography after an uneventful surgery without intraoperative fracture. The fracture rate for hemispherical and peripheral self-locking cups has been described as 8.4%. We retrospectively analyzed postoperative CT scans after primary THA to clear the question whether such occult periprosthetic fractures of the acetabulum require particular treatment strategy. Between 2014 and 2018 we identified 115 CT scans of 114 patients after primary cementless THA with elliptical cups using a direct anterior approach. The CT scans were obtained as part of other investigations. Localization of the fracture, patients demographics, clinical (WOMAC, Harris Hip Score) and radiological outcome were analyzed. Fracture and non-Fracture group were compared with regard to demographics and short-term outcome after 1 year. Four occult fractures (3.5%) were identified. Three fractures involved the posterior wall. All patients had an uneventful routine postoperative rehabilitation. Patients with occult fractures showed similar post- operative HHS and WOMAC scores at 3 (HHS p = 0.576, WOMAC p = 0.128) and 12 (HHS p = 0.479, WOMAC p = 0.588) months. There were no cup loosening nor radiolucent lines at latest follow-up (mean FU 22 months, range 12-34 months). Clinical and radiological short-term outcome was not impaired by the occurrence of an occult periprosthetic fracture of the acetabulum. The incidental detection of an occult periprosthetic fracture of the acetabulum does not seem to oblige the surgeon to adapt the postoperative regime.

Consistency of 3D femoral torsion measurement from MRI compared to CT gold standard.

BACKGROUND: Several hip and knee pathologies are associated with aberrant femoral torsion. Diagnostic workup includes computed tomography (CT) and magnetic resonance imaging (MRI). For three-dimensional (3D) analysis of complex deformities it would be desirable to measure femoral torsion from MRI data to avoid ionizing radiation of CT in a young patient population. 3D measurement of femoral torsion from MRI has not yet been compared to measurements from CT images. We hypothesize that agreement will exist between MRI and CT 3D measurements of femoral torsion. METHODS: CT and MRI data from 29 hips of 15 patients with routine diagnostic workup for suspected femoroacetabular impingement (FAI) were used to generate 3D bone models. 3D measurement of femoral torsion was performed by two independent readers using the method of Kim et al. which is validated for CT. Inter-modalitiy and inter-reader intraclass correlation coefficients (ICC) were calculated. RESULTS: Between MRI and CT 3D measurements an ICC of 0.950 (0.898; 0.976) (reader 1) respectively 0.950 (0.897; 0.976) (Reader 2) was found. The ICC (95% CI) expressing the inter-reader reliability for both modalities was 0.945 (0.886; 0.973) for MRI and 0.957 (0.910; 0.979) for CT, respectively. Mean difference between CT and MRI measurement was 0.42° (MRI - CT, SD: 2.77°, p = 0.253). CONCLUSIONS: There was consistency between 3D measurements of femoral torsion between computer rendered MRI images compared to measurements with the "gold standard" of CT images. ICC for inter-modality and inter-reader consistency indicate excellent reliability. Accurate, reliable and reproducible 3D measurement of femoral torsion is possible from MRI images.

Revision After Total Transmetatarsal Amputation.

Total transmetatarsal amputation (TMA) can be an option for foot salvage in gangrene, sepsis, or infected necrosis. However, the literature concerning predictive outcome factors and bacterial sampling is scarce. To identify potential associations between revision surgery and underlying bacteria or other preoperative selection criteria, we reviewed all patients with TMA who were treated at our institution. We compared the patients with remissions with surgical revisions. Among 96 adult patients with TMA (105 amputations), 42 required a revision surgery (40%), 18 had a further minor proximal surgical reamputation (17%) and 18 had a major proximal surgical reamputation (14%). In group comparisons, a previous infection with Staphylococcus aureus was protective with a lower revision risk (4/26 with revision surgery vs 22/26 without revisions; p = .03). This was the opposite for postoperative persistent soft tissue or bone infections (p < .01) and delayed wound healing (p < .01), which were positively associated with a revision risk. The American Society of Anesthesiologists Score, sex, age, body mass index, diabetes, polyneuropathy, chronic renal failure, dialysis, peripheral arterial disease, smoking status, and antibiotic regimen did not influence this revision risk. These results must be interpreted cautiously because no multiple variable calculations could be conducted as a result of the paucity of cases and confounding could not be evaluated sufficiently. TMA is an option to prevent major amputations, but it may be associated with a subsequent revision risk of 40% in adult patients. In our cohort study, persistent postamputation infection and delayed wound healing were associated with revision. However, no preoperative selection criteria were found that lead to revision surgery except for an infection with Staphylococcus aureus, which protected against revision surgery.