These authors studied 147 patients with primary osteoarthritis who underwent aTSA with a stemless humeral implant and a pegged glenoid between January 2011 and December 2016.
Anteroposterior radiographs were evaluated at six, 12, 24 months, and five years post-TSA for lateral humeral offset (LHO), joint gap (JG), acromiohumeral distance (AHD), andradiolucency (modified Franklin score); patients were included.
The five x-rays below show progressive loss of joint gap and osteolysis around the humeral and glenoid component.
AHD, LHO, and JG all showed a consistent and statistically significant decline over time, with the joint gap decreasing by half. Consistently, smaller joint gap and acromiohumeral distance were correlated with lower subjective shoulder values (p = 0.03 and p = 0.07, respectively).The relationship between the AHD, offset and joint gap to the degree of glenoid loosening and clinical scores are shown below. Massive loosening was associated with a 14.5 points lower SSV (p < 0.01). Narrowing of the joint gap was significantly correlated with increased radiolucency (p < 0.001) and tended toward worse SSV (p = 0.06).
The authors concluded that radiographic parameters displaying medialization and cranialization after aTSA with a cemented pegged glenoid are useful predictors of impaired shoulder function.
Comment: In this study there are many factors that could have influenced the radiographic and clinical outcomes, including serve systemic disease in over one third, the status of the rotator cuff, the degree of cross linking of the polyethylene, the glenohumeral pathoanatomy, the degree of glenoid reaming, the use of a small glenoid component, the cement technique and the placement of the humeral component. Note that in the example given in the article, the humeral component was placed superiorly in relation to the "perfect circle". Superior positioning of the humeral component could lead to eccentric wear of the superior glenoid component (A recent article, Radiographic humeral head restoration after total shoulder arthroplasty: does the stem make a difference? reported, "Restoration of humeral anatomic parameters occurred significantly less with stemless implants than with short- and standard-stem implants. The stem of a shoulder arthroplasty implant aids surgeons in accurately restoring patient-specific anatomy.")
Thus it would be of interest to know which pf these eight factors were related to loss of the joint gap and to superior migration of the humeral head. It would also be of interest to know what percentage of the 211 shoulders were surgically revised.
