The evaluation of a patient who has undergone total shoulder replacement is a complex process. There are clinical and radiographic parameters that are taken into account to assess the postoperative function and status of the shoulder. From a radiographic perspective the type of the implant used, the patient characteristics, the diagnosis at the time of surgery, and the radiographic appearance of the shoulder prior and after surgery are key components in evaluating the overall status of the shoulder replacement as well as predicting the longevity of the implant.
The following case is a female patient in her sixties who underwent total shoulder replacement for inflammatory glenohumeral arthritis (rheumatoid arthritis) with an intact rotator cuff. Preoperative CT scan and postoperative radiographs are demonstrated below.
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| CLICK ON IMAGES FOR LARGER VERSION |
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| Inflammatory arthropathy. CT demonstrates medialization of the shoulder due to glenoid erosion. |
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| Immediate Grashey postoperative view of the shoulder |
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| Axillary view demonstrates no subluxation or dislocation |
The picture above illustrates the all polyethylene glenoid components and an example metal backed glenoid component. As of today most surgeons use all polyethylene glenoid components. There are different configurations and designs however it is critical to assess whether a metal backed or an all polyethylene glenoid component was used.
The second step in the assessment is to evaluate the "height" of the prosthesis. In normal shoulders the top of the humeral head lies 4-6mm higher than the footprint of the rotator cuff as illustrated above.
Preoperative Xrays can be helpful in identifying the pathology for which the total shoulder replacement was performed. In the picture above the presence of large inferior osteophytes is an indication of degenerative arthritis. Inflammatory arthropathy as in the case demonstrated at the beginning of this post is not associated with formation of osteophytes. In the picture above and below the concept of the "height" of the prosthesis is indicated.
A "low" placement of the prosthesis can lead to "overstuffing" of the joint and stiffness. A superiorly prominent prosthesis as illustrated on the above picture on the left can lead to impingement and irritation of the rotator cuff and early failure in the midterm due to failure of the rotator cuff.
While the anterior posterior offset is difficult to assess with radiographs (see picture above) correct placement of the implant during surgery is crucial
The quality of the Xrays during evaluation is essential. The Grashey view as illustrated above with the Xray beam angled 45 degrees in relation to the body of the patient and perpendicular to the plane of the scapula is an essential view for radiographic assessment of the glenoid and humeral implant.
The three parameters evaluated in the picture above are from left to right. (1) the varus position of the stem that leads to stiffness due to overstuffing of the joint (2) the acromio-humeral index which is indicative of the status of the rotator cuff ie if the cuff has failed the distance becomes smaller-high riding humeral head (3) the height of the prosthesis in relation to the footprint of the rotator cuff as described previously.
The concept of radiolucency and loosening is important to be assessed on the initial postoperative and late postoperative period. Be aware that radiolucent lines can reach up to 50% around the all polyethylene glenoid components at 5 years after surgery, while in some cases they can be seen on the immediate postoperative xrays which may indicate poor technique in terms of seating of the implant or cementation of the peripheral pegs. Radiolucent lines are seen around the zones of the stem and around the polyethylene glenoid component in cases of loosening (see pictures above and below).
The axillary view as demonstrated below should be performed with care making sure that the beam is parallel to the plane of the scapula and the entire glenoid rim can be viewed.
This is critical to assess subluxation or dislocation of the implant. Techniques of obtaining an axillary view are demonstrated below.
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| Axillary view indicates no subluxation or dislocation. Notice that the entire ream of the glenoid is visible without overlap or superimposition of the glenoid, coracoid process or acromion. |
Although there are grading systems to assess the subluxation of the implant these systems have limited clinical use. The main question that needs to be answered during evaluation of the axillary view is whether there is subluxation or dislocation
