Intraosseous lipomas originating from simple bone cysts.

PURPOSE: Fatty or part-fatty intraosseous lesions are occasionally encountered while imaging the skeletal system. A number of case reports have proposed involution of calcaneal bone cysts to intraosseous lipomas, but this has never been proven. This paper sets out to prove that simple bone cysts (SBCs) can involute to fatty lesions indistinguishable from intraosseous lipomas. MATERIALS AND METHODS: The pathology and PACS databases at 2 specialist orthopedic hospitals were retrospectively interrogated for all cases of intraosseous lipomas or SBCs with cross-sectional imaging follow-up for SBCs and precursor or follow-up imaging for intraosseous lipomas, in the time period from August 2007 to December 2016. For intraosseous lipoma cases, these were only included if change in imaging appearances was observed. RESULTS: There was no case of change in the appearance in intraosseous lipomas. Six cases of SBC with cross-sectional imaging follow-up were identified in one participating hospital and none in the other. The 6 cases were comprised of 4 male and 2 female patients. Two were located in the proximal humerus, one in the proximal tibia, and 3 in the os calcis. All cases demonstrated filling in of the cystic lesion with fat from the periphery, in 2 cases complete filling in, and in 4 cases partial fatty conversion. CONCLUSION: SBCs can heal with fatty conversion of the cystic cavity, with partly cystic remnants. It is proposed that at least part of the so-called intraosseous lipomas are healed simple bone cysts.

Ultrasound assessment of the posterolateral elbow ulnohumeral gap in normal subjects with and without posterolateral drawer testing.

Background: Posterolateral rotator instability (PLRI) is the most common pattern of recurrent elbow instability, and current imaging to aid PLRI diagnosis is limited. Thus, we sought to define use of ultrasound (US) to determine normal lateral ulnohumeral joint measurements, with and without posterolateral drawer testing to provide an insight into how US may aid diagnosis. Methods: Sixty elbows were evaluated in thirty healthy volunteers. The lateral ulnohumeral gap (LUHG) was measured with US in the resting position while the posterolateral drawer stress test maneuver was applied. Joint laxity was calculated as the difference between maximum stress and average rest measurements. Two independent readers assessed each elbow with comparison performed between stress and rest positions. Results: Differences in the LUHG were evident between stress and rest conditions (reader 1: P < .0001 and reader 2: P = .0002). At rest, median LUHG values were 2.31 mm and 2.05 mm for readers 1 and 2 respectively, while at stress 2.88 mm and 2.9 mm for readers 1 and 2. Median joint laxity was 0.8 mm for reader 1 and 1.1 mm for reader 2. Pearson correlation was r = 0.457 (absolute intraclass correlation coefficient [ICC] = 0.608) while under stress and r = 0.308 (absolute intraclass correlation coefficient [ICC] = 0.417) at rest. Median joint laxity demonstrated a Pearson correlation of r = 0.161 and absolute intraclass correlation coefficient [ICC] = 0.252. Conclusions: This study demonstrates a dynamic US assessment for PLRI, which aimed to assess the usefulness and feasibility of a laxity measurement after the application of a posterolateral drawer stress maneuver in a healthy population. Although establishing concordance between readers in measuring an LUHG under stress, the utility of a laxity measurement alone is not clear as correlation of measurements is not excellent; hence, an upper limit of normal for the ulnohumeral gap under stress may be more useful. Further evaluation of this technique is required in patients with PLRI.