Free Shoulder CT Viewer for Glenoid, Humerus, and Scapula Detail

Getting From Files to Findings

Why a Shoulder CT Instead of an MRI

Surgeons order a dedicated shoulder CT, rather than an MRI, whenever the question is really about bone rather than soft tissue. Before an anterior shoulder stabilization procedure, CT measures how much glenoid bone has been lost off the front rim of the socket and lets the surgeon trace the glenoid track — the strip of humeral head bone that stays in contact with the glenoid through the arc of rotation. When that track is breached by a Hill-Sachs lesion on the back of the humeral head, the CT is what sizes the depression and decides whether a soft-tissue repair alone will hold or whether bone needs to be added back.

CT is also the workhorse for trauma. A proximal humerus fracture is classified by how many major fragments have separated — the head, the shaft, and the two tuberosities — and by how far each fragment has rotated or displaced, detail that is much easier to see on thin CT slices than on plain films. Scapular body fractures and clavicle fractures, including where a clavicle fracture sits relative to the coracoclavicular ligaments, are read the same way: slice by slice through the bone, then confirmed on a 3D render when the fracture pattern is complex.

For replacement surgery, a preoperative CT gives the surgeon glenoid version — how far the socket faces forward or backward relative to the scapular body — plus bone stock and wear pattern, all of which feed into templating for a total or reverse shoulder replacement. After surgery, if a replaced shoulder becomes painful, CT (sometimes with metal-suppression technique) is used to look for loosening at the bone-implant interface, since the metal in a replacement degrades MRI far more than it degrades CT.

What a Shoulder CT Dataset Actually Contains

A modern shoulder CT is acquired as a thin, sub-millimetre axial stack on a sharp bone kernel, which trades a grainier soft-tissue appearance for crisp cortical edges. Because the raw voxels are close to isotropic, the scanner or the reading workstation can build oblique coronal and sagittal reformats that are angled to the plane of the scapula rather than to the axis the patient was lying in — those scapular-plane views are what let a radiologist compare the glenoid to the humeral head the same way on every study.

For instability workups, the dataset often includes an en-face glenoid reconstruction, built by digitally subtracting the humeral head so the socket rim can be viewed straight on, like looking at a clock face. Many studies also carry a 3D surface-rendered volume of the scapula and proximal humerus, which is what most people picture when they hear “3D CT of the shoulder” and is genuinely useful for visualizing a fracture pattern or a glenoid defect before surgery.

What You Can Do With It Here

Reading the Language in a Shoulder CT Report

A shoulder CT report will often quote a percentage of glenoid bone loss — the fraction of the socket's surface area missing off the anterior rim, calculated from the en-face view. That number, together with the size of any Hill-Sachs lesion, is what separates a soft-tissue stabilization from a bone-block or Latarjet-type procedure. You may also see a description of an “inverted-pear” glenoid, which means the normal pear-shaped socket has been eroded into a narrower, more rounded contour by chronic anterior bone loss.

Reports on trauma or arthritic shoulders describe glenoid version — the angle of the socket relative to the scapular body, expressed as retroverted or anteverted degrees — which templating software uses to plan implant position before a replacement. For a proximal humerus fracture, look for tuberosity displacement measured in millimetres, since greater tuberosity displacement beyond a small threshold is often what tips the decision toward surgical fixation rather than a sling and physical therapy.

Where CT Stops Being the Right Tool

CT is unmatched for cortical bone detail, but it is a poor tool for the soft tissues that cause most shoulder pain. The rotator cuff tendons, the labrum, and the long head of the biceps tendon all show up as low-contrast soft tissue on CT, with none of the signal differences that let MRI separate a partial-thickness tear from an intact tendon or a labral tear from a normal capsular fold. A CT arthrogram, where contrast is injected into the joint before scanning, can outline the labrum and cuff undersurface reasonably well, but a plain, non-arthrogram shoulder CT is read for bone and should not be relied on to clear or diagnose a cuff or labral injury.

Supported CT Formats

Frequently Asked Questions

3D CT and DICOM Viewing

A shoulder CT is a good candidate for 3D and MPR precisely because it is acquired as a thin, near-isotropic volumetric series to begin with. How sharp the resulting scapular or glenoid render looks still depends on the original slice thickness and spacing, the bone kernel used at acquisition, and how much memory your device has free.

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