Shoulder arthroplasty in osteoarthritis: correlation between function and radiographic parameters

Determination of humeral inclination in stemless shoulder arthroplasty using plain radiographs

Plain radiographs of the shoulder are routinely used to assess implant orientation after shoulder arthroplasty. Recently, humeral inclination has come into focus especially in reverse stemless shoulder arthroplasty. But, in X-ray projections not exactly parallel to the base of the humeral component, the humeral inclination angle cannot be determined precisely. Therefore, we established a mathematical algorithm to calculate the humeral neck shaft angle and counterchecked the formula using plain radiographs of a sawbone model containing a humeral head prosthesis. With increasing angles of retroversion, the base of the humeral component forms an ellipse in plain radiographs. Knowing the width and length of the ellipse as well as the inclination angle in a plain radiograph, the exact inclination angle can be determined using the equation reported below. Thus, independent from the viewing angle or angle of retroversion, the inclination angle of a stemless humeral head implant can be estimated with an accuracy of ±1.5-degree deviation. The algorithm proposed may be the basis for further research on the impact of humeral inclination in stemless shoulder arthroplasty.

A reliable method of determining glenohumeral offset in anatomic total shoulder arthroplasty

BACKGROUND

Glenohumeral offset (GHO) may change from the preoperative state after anatomic total shoulder arthroplasty (TSA), and has been identified as a factor that may affect shoulder mechanics, strength, and function. The primary objective was (1) to establish a reliable method of measuring GHO with standardized computed tomography (CT) imaging planes and (2) to determine whether an association exists between GHO and functional outcomes in TSA.

METHODS

Thirty-seven patients underwent TSA for glenohumeral osteoarthritis. Preoperative and postoperative CT scans were reformatted along standardized measurement planes for the glenoid and humerus separately. Inter-rater and intrarater reliability was determined for 3 methods to measure humeral offset and 2 methods to measure glenoid offset. Univariate regression analysis was used to determine the association between GHO and functional outcomes including the Constant score and strength.

RESULTS

Of all methods tested, the highest preoperative and postoperative inter-rater reliability was r = 0.84 and r = 0.8, and r = 0.7 and r = 0.8 for humeral and glenoid offset, respectively. Intrarater reliability was >0.94. There was a mean increase of 4.3 mm (standard deviation, 4.6; range, -10.6 to 10.8) in combined GHO from preoperative to postoperative time points. No associations were observed between change in offset and functional or strength scores.

DISCUSSION

A reliable approach to measure prearthroplasty and postarthroplasty GHO with CT plane standardization has been described. A net increase in GHO was observed after TSA. No associations were found between change in offset after TSA and functional scores or strength up to 2 years postoperatively.

Predictors of medium-term clinical outcomes after total shoulder arthroplasty

PURPOSE

The study aims to measure the relationship of potential clinical and radiographic predictors and medium-term clinical outcomes after total shoulder arthroplasty in primary osteoarthritis.

MATERIALS AND METHODS

In a prospective follow-up study, preoperatively collected clinical and radiographic variables were recorded in 103 patients with an average age of 66 years (range 37-83 years) to measure their influence on the clinical outcome by use of the Constant score. The average length of follow-up was 6 years (range 3-12 years). Radiographs and a computed tomography (CT) of the shoulders were obtained preoperatively for evaluating the acromiohumeral distance, the lateral glenohumeral offset and the morphology of the glenoid, which was classified according to the method by Walch (type-A1 to type-C glenoids).

RESULTS

The mean Constant score improved from its preoperative value of 25 points (range 6-54 points) to 65 points (range 10-86 points) postoperatively (p < 0.001). The mean age- and sex-normalized Constant score was similarly improved from 34 points (range 8-78 points) preoperatively to 90 points (range 14-130 points) at the time of follow-up (p < 0.001). The Walch classification of glenoid wear had a significant negative effect (r = -0.32, p < 0.001). The other predictors showed no significant influence on the Constant score (p > 0.05).

CONCLUSION

A higher Walch classification is a negative predictor for the postoperative clinical function. The proven significant negative effect  on outcomes in total shoulder arthroplasty emphasizes the importance of the preoperative evaluation of humeral head subluxation and glenoid erosion, which are associated with less favorable postoperative results. The measured internal patient variables gave no negative predictions on the medium-term clinical outcomes in the study population.

Comparison of satisfied and dissatisfied patients 2 to 5 years after anatomic total shoulder arthroplasty

BACKGROUND

With an increasingly large number of patients undergoing total shoulder arthroplasty (TSA) combined with increased requirements for public reporting of patient outcomes, there is a greater need to better understand the underlying factors related to patient satisfaction. The purpose of this study was to compare patient demographics, nonorthopedic comorbidities, patient-reported outcome scores, and range of motion of patients who reported being either satisfied or dissatisfied with their procedure at midterm follow-up.

METHODS

We identified 234 primary TSAs performed by a single surgeon for glenohumeral osteoarthritis with a minimum 2-year follow-up in a prospective shoulder arthroplasty registry. American Shoulder and Elbow Surgeons (ASES) score, patient satisfaction, and active forward flexion, abduction, and external rotation at 0° of flexion-abduction were assessed before and after TSA.

RESULTS

Of the 234 patients, 207 (88.5%) were satisfied with their procedure. Dissatisfied patients had significantly lower ASES scores both before and after surgery (P < .001) as well as a significantly lower preoperative to postoperative change in ASES score (P < .001). Similarly, dissatisfied patients demonstrated significantly lower changes in active forward flexion (P = .004), abduction (P = .02), and external rotation (P = .03). Patients with ASES score changes <12 points were 19 times more likely to be dissatisfied after TSA (95% confidence interval, 4.4-81.4; P = .0001).

CONCLUSION

Dissatisfied patients had significantly lower improvements in pain, function, and range of motion. Furthermore, a change in ASES score <12 points was associated with a 19-fold increase in the risk of being dissatisfied after TSA.