Ulnar dimelia often presents with restricted elbow movement. To develop a treatment strategy to improve elbow mobility, a detailed understanding of the skeletal deformity is needed. We created 3-D models of the cartilage and bone in the elbows of four children with ulnar dimelia by segmentation of MRI scans. We analysed the anatomy and performed a kinematic analysis. In all four children, the distal humerus was triangular in shape and consisted of a medial epicondyle, an enlarged lateral epicondyle and an anterior epicondyle. By comparing the 3-D images with conventional radiographs, we found that the projection of the enlarged lateral epicondyle created two longitudinal lines, which is a radiographic hallmark feature of the triangular-shaped distal humerus. In addition, during elbow flexion, the radial forearm bone slides along the lateral trochlea rather than rotates. This knowledge can aid surgeons to plan treatment for improving elbow mobility in ulnar dimelia.Level of evidence: IV.

Osteochondritis dissecans (OCD) of the humeral trochlea is very rare. It may cause pain, mechanical symptoms, and loss of elbow motion, typically in the adolescent athlete. However, little published information is available regarding this condition. To describe the clinical presentation, radiographic features, and prognosis of trochlear OCD. Case series; Level of evidence, 4. Over a 10-year period, 28 patients presented to a tertiary pediatric hospital with trochlear OCD. Medical records and imaging were analyzed to characterize presentation, lesions appearances, and outcomes. Mean ± SD age at presentation was 13.4 ± 1.6 years, and 13 of the 28 patients were male. The most common presenting symptom was pain (93%), followed by crepitus (54%). Evidence of trochlear OCD could be seen on initial radiographs in 94% of cases but was commonly missed. Coexisting capitellar OCD lesions were the most common associated abnormalities seen on magnetic resonance imaging (21%). Investigators noted 2 predominant patterns: "typical" trochlear OCD lesions (89%) were located on the lateral crista of the trochlea, 3.1 ± 4.4 mm lateral to the apex of the trochlear groove. This location corresponded to the medial tip of the capitellar epiphyseal ossification center and was not actually on the trochlear ossification center. "Atypical" trochlear OCD lesions (11%) were located more posteromedially. Trochlear OCD lesions in 4 elbows were managed surgically, while the remainder were managed nonoperatively. At mean ± SD follow-up of 13 ± 8 months, 12 patients (43%) were asymptomatic. A further 5 patients had ongoing crepitus but no pain (18%), and 4 patients (14%) underwent surgical treatment for their trochlear OCD (osteochondral fixation, n = 1; drilling/curettage, n = 3); 3 of the 4 patients experienced some improvement in pain. Although rare, trochlear OCD can cause considerable elbow problems. Clinicians should be aware of this differential diagnosis. Plain radiographs should be carefully scrutinized for subtle signs of trochlear OCD, particularly in the repetitive or overhead athlete with elbow pain. Although most patients' symptoms will improve with activity modification, some may require surgery.

Fishtail deformity is a rare deformity of the humerus exhibiting concavity of the lateral trochlea, resulting in ulnotrochlear joint derangement. We wanted to share our experience that osteochondritis dissecans of the capitellum is a common associated complication. To summarize imaging of fishtail deformity in children centered on complications of the radiocapitellar joint. From the radiology information system, we identified all patients <18 years with the diagnosis of fishtail deformity. We included only patients with V-shaped deformity of the distal humerus due to concavity at the lateral trochlea (fishtail deformity). Each patient's initial injury, most recent radiograph and available MRI were evaluated for radiocapitellar joint derangement. Seven patients (4 males) with a mean age of 12.9 years (range: 9.7 to 14.4 years) were identified. Radiocapitellar joint abnormalities were identified in six patients including osteoarthritis (n=5), flattened and sclerotic capitellum (n=4), osteochondritis dissecans (2 associated with loose body, n=4) and radial head subluxation (n=2). In 4 patients, MRI detected changes of osteoarthritis (n=4), osteochondritis dissecans (n=2) and loose body (n=1) not identified on radiography. Two patients with osteochondritis dissecans underwent surgery and one patient has planned surgery. Radiocapitellar joint abnormalities (particularly, capitellar osteochondritis dissecans) are common in patients with fishtail deformities. MRI should be performed in these patients since some abnormalities, possibly requiring surgery, are not detected on elbow radiographs.

Muscles of flexor compartment of forearm have a common origin from medial epicondyle of humerus. Additional bellies of flexor muscles are commonly reported but presence of supernumerary muscles is an infrequent phenomenon. The present study describes an unusual muscle mass in flexor compartment of forearm simulating pronator teres. During routine dissection the upper limb of a 50 years old male cadaver, a supernumerary muscle was found on left side of the upper limb in the flexor compartment. The origin of the muscle was 2cm wide and aponeurotic in nature and attached to an oblique line extending from the inferior surface of the medial epicondyle and the medial surface of the trochlea. It was inserted on an oblique line 2.5cm wide on the radius in area between supinator superiorly and flexor digitorum profundus inferiorly. Existence of accessory muscles, which connect flexor muscles, could be explained embryologically by incomplete cleavage of flexor mass during development. The flexor muscles of the forearm develop from the flexor mass which subsequently divides into two layers: superficial and deep. The deep layer gives rise to flexor digitorum superficialis, flexor digitorum profundus and flexor pollicis longus. These supernumerary muscles are extremely rare entities and probably represent deranged embryological development or the process of atavism in which the anomalous part persist for a longer time in the tree of evolution.