Bond, Jeffrey R.

Background: Magnetic resonance imaging (MRI) is considered to be the gold standard for imaging of osteochondritis dissecans (OCD). Purpose/Hypothesis: The purpose was to determine the additional value of a preoperative computed tomography (CT) scan in adolescent patients with capitellar OCD of the elbow. Consistent with the fact that OCD is a lesion involving the subchondral bone, the hypothesis was that CT would be superior to MRI for imaging OCD of the capitellum. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: All patients being treated surgically for an OCD of the capitellum between 2006 and 2016 at one institution were reviewed for preoperative imaging. A total of 28 patients met the inclusion criteria. Corresponding MRI and CT scans were compared retrospectively. Multiple parameters were recorded, with special emphasis on OCD lesion size, fragmentation, and tilt as well as joint surface integrity, loose bodies, and osteophytes. Results: The OCD lesions were best seen on CT scans, whereas MRI T1-weighted images overestimated and T2-weighted images underestimated the size of defects. A subchondral fracture nonunion was found on CT scans in 18 patients, whereas this was seen on MRI T1-weighted images in only 2 patients ( P < .001) and MRI T2-weighted images in 4 patients ( P < .001). Fragmentation of the OCD fragment was found on CT scans in 17 patients but on MRI scans in only 9 patients ( P = .05). Osteophytes as a sign of secondary degenerative changes were seen on CT scans in 24 patients and were seen on MRI scans in 15 patients ( P = .02). Altogether, only 51 of 89 secondary changes including loose bodies, effects on the radial head and ulnohumeral joint, and osteophytes that were seen on CT scans were also seen on MRI scans ( P = .002). Conclusion: OCD fragmentation and secondary changes were more often diagnosed on CT. These factors indicate OCD instability or advanced OCD stages, which are indications for surgery. In an adolescent who is considered at risk for OCD (baseball, gymnastics, weightlifting, tennis) and who has lateral elbow joint pain with axial or valgus load bearing, CT is our imaging modality of choice for diagnosing and staging OCD of the capitellum.

A 16‐year‐old high school football player presented with 4 months of anterior knee pain and small, mobile, prepatellar “lumps” after falling onto an opponent's cleat. He reported knee pain primarily during knee flexion and direct pressure during squatting and kneeling. Knee radiographs were unremarkable. Ultrasonography revealed multiple, freely mobile, subcutaneous nodules of variable size and echogenicity in the prepatellar region. Analysis of magnetic resonance imaging suggested possible fat necrosis but was nondiagnostic. The patient opted for surgical exploration, at which time multiple, opalescent subcutaneous nodules were removed. Pathology was consistent with encapsulated fat necrosis. After surgery, his symptoms resolved, and he returned to sports without restrictions.

Objectives: TT-TG distance is a commonly used measurement for surgical decision-making in patients with patellofemoral malalignment and instability. This measurement has historically been performed utilizing axial CT scans. More recently, MRI has been proposed as an equivalent test for measurement of TT-TG distance. We sought to determine the reliability of TT-TG measurements on both MRI and CT, and to determine whether the measurements can be used interchangeably. Methods: All patients diagnosed with patellar instability who had received both CT and MRI of the knee between 2003 and 2011 were included (n=59 knees in 54 patients). Two fellowship trained musculoskeletal radiologists measured the TT-TG distances for each patient by CT and MRI in a randomized, blinded fashion for a total of 236 measurements. Inter-observer reliability was calculated between radiologists for both imaging modalities and inter-methods reliability was calculated between the two imagining modalities. The results are reported using intraclass correlation coefficients (ICC) and Bland Altman analysis (BAA). Results: The 59 knees had a mean TT-TG distance of 16.9 mm (range: 8.3-25.8) by CT and 14.7 mm (range: 1.5-25.1) by MRI. Eighteen patients (31%) had a TT-TG ≥ 20 mm by CT, and only 9 (15%) had a TT-TG ≥ 20 mm by MRI. Inter-observer reliability between the radiologists was considered excellent for both CT and MRI (ICC = 0.777 and 0.843 respectively). When comparing CT to MRI, however, the ICC was considered only fair for each of the two raters (0.532 and 0.539). A total of 11 patients (19%) had a TT-TG ≥ 20 mm on CT preoperatively and underwent distal realignment by tibial tubercle osteotomy (TTO). In this surgical subgroup, the mean TT-TG on CT was 22.5 mm (range 19.8-25.8) while the mean TT-TG on MRI was only 18.7 mm (range 14.4-22.8). Conclusion: TT-TG distance can be measured with excellent inter-rater reliability on both MRI and CT scans; however, the values derived from these two tests may not be interchangeable. This observation should be taken into consideration when MRI is used for surgical planning since MRI may underestimate TT-TG distance when compared to CT.

Background: Tibial tubercle–trochlear groove distance (TT-TG) is a commonly used measurement for surgical decision making in patients with patellofemoral malalignment and instability. This measurement has historically been performed utilizing axial computed tomography (CT). More recently, magnetic resonance imaging (MRI) has been proposed as an equivalent method, but this has not yet been fully validated. Purpose: To determine the reliability of TT-TG distance measurements on both MRI and CT and to determine whether the measurements are interchangeable with one another. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: All patients with patellar instability who underwent both CT and MRI of the knee from 2003 to 2011 were included (n = 59 knees in 54 patients). Two fellowship-trained musculoskeletal radiologists measured the TT-TG distances for each patient by CT and MRI in a randomized, blinded fashion. Interobserver reliability was calculated between radiologists for both imaging modalities, and intermethod reliability was calculated between the 2 imaging modalities. The results are reported using intraclass correlation coefficients (ICCs) and Bland-Altman analysis. Results: The 59 knees had a mean TT-TG distance of 16.9 mm (range, 8.3-25.8 mm) by CT and 14.7 mm (range, 1.5-25.1 mm) by MRI. Interobserver reliability between the radiologists was considered excellent for both CT and MRI (ICC = 0.777 and 0.843, respectively). When comparing CT to MRI, the ICC was considered only fair for each of the raters (0.532 and 0.539). Eleven patients (19%) had a TT-TG distance of ≥20 mm on CT preoperatively and underwent distal realignment by tibial tubercle osteotomy. In this surgical subgroup, the mean TT-TG distance was 22.5 mm (range, 19.8-25.8 mm) by CT and only 18.7 mm (range, 14.4-22.8 mm) by MRI for a mean difference of 3.80 mm ( P < .001). Conclusion: The TT-TG distance can be measured with excellent interrater reliability on both MRI and CT; however, the values derived from these 2 tests may not be interchangeable. This observation should be taken into consideration when MRI is used for surgical planning because MRI may underestimate the TT-TG distance when compared with CT.

Background: Decreased hip range of motion (ROM) is a common finding in patients with femoroacetabular impingement (FAI). Purpose: To report the prevalence of decreased hip ROM in asymptomatic adolescent athletes and to correlate examination findings to signs of FAI on radiographs and magnetic resonance imaging (MRI). Study Design: Cross-sectional study (prevalence); Level of evidence, 3. Methods: A total of 226 adolescent athletes presenting for state-mandated preparticipation physical examinations were assessed. Hip internal rotation was measured with the participant supine and the hip flexed to 90°. All participants with ≤10° of internal rotation were invited to return for standard radiographs and MRI of both hips. An age-matched control group, with >10° of internal rotation, underwent MRI examination only. Twenty-six athletes (13 study and 13 control) returned for clinical and radiographic examinations. Results: Nineteen athletes (34 hips, 8%) were found to have <10° of internal rotation. Eight athletes (13 hips, 3%) also had a positive anterior impingement sign. Thirteen of 19 athletes participated in the radiographic portion of the study. Of these 13 participants, 4 had limited internal rotation unilaterally, leaving 22 hips in the study group. Eight of 13 participants (15 hips, 68%) had a cam-type deformity evident on plain radiographs, and 4 participants (7 hips, 32%) had a positive radiographic crossover sign. The average α angle measured from radial MRI sequences was 58.1° in the study group versus 44.3° in the control group ( P < .001). Fifteen hips (68%) in the study group had abnormal MRI findings within the acetabular labrum or cartilage compared with 10 of 26 hips (38%) in the control group (odds ratio, 3.4; P = .078). Conclusion: Eight percent of asymptomatic teenagers had limited internal rotation on examination; 68% of these had radiographic findings suggestive of FAI. More than two thirds of these participants had evidence of asymptomatic hip pathological lesions on MRI.