Original article
A study of the micromovement of pegged and keeled glenoid components compared using radiostereometric analysis

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In a prospective, randomized study between 2000 and 2004, 20 patients with primary osteoarthritis of the shoulder had a total shoulder arthroplasty with radiostereometric analysis, 10 with keeled and 10 with pegged glenoid components. The relative movement of the glenoid component with respect to the scapula was measured over a 24-month period. Three keeled and five pegged glenoids needed reaming for erosion. The largest translations occurred along the longitudinal axis (mean of 1.35 mm for keeled eroded components) ( P = .017 for keeled vs pegged components and P = .013 for eroded vs non-eroded components). Both of the other translation axes showed no significant differences. The highest maximum total point movement at 24 months was 2.57 mm for keeled eroded components and 1.64 mm for pegged eroded components ( P = .029 for keeled vs pegged components and P = .023 for eroded vs non-eroded components). The largest rotation was anteversion, with mean values of 5.5° for keeled eroded components and 4.8° for pegged eroded components ( P = .658 for keeled vs pegged components and P = .90 for eroded vs non-eroded components). The mean varus tilt was 4.5° for keeled eroded components compared with 2.3° for pegged eroded components ( P = .004 for keeled vs pegged components and P = .016 for eroded vs non-eroded components), and finally, anterior-posterior rotation mean values were 3.5° for keeled eroded components and 1.1° for pegged eroded components ( P = .022 for keeled vs pegged components and P = .04 for eroded vs non-eroded components). In conclusion, whereas all components moved, radiostereometric analysis revealed increased migration with keeled components, exacerbated by glenoid erosion. Furthermore, a distinctive pattern of migration was identified over the 2-year period.

Section snippets

Materials and methods

In a prospective, randomized study between 2000 and 2004, 20 patients with primary osteoarthritis had a total shoulder arthroplasty with roentgen stereophotogrammetric analysis. Full ethical committee approval and patient informed consent were obtained. To enter the study, patients had to have good glenoid bone stock, sufficient to introduce a glenoid component, and an intact and functioning rotator cuff. Two patients died before the end of the study, another had unstable marker-bead placement,

Results

The clinical outcome for all patients is shown in Table I at 2 years postoperatively, with pain scores, range of movement, Constant-Murley scores, and self-assessed American Shoulder and Elbow Surgeons scores all improving significantly (P < .001, paired t test) for both keeled and pegged groups of patients.

The results of translations of the glenoid rigid body are presented in Table II. Two of the three axes of translation showed significant translation over time, with the third, the sagittal

Discussion

As stated previously, aseptic loosening of the glenoid component is a common complication of total shoulder arthroplasty. In the 1970s, several designs of constrained implants had a high rate of glenoid loosening.11 In contrast, Neer9 reported a 10-year follow-up of 46 unconstrained total shoulder arthroplasties and reported no evidence of clinical loosening. As a consequence, this type of glenoid forms the basis of most modern designs. However, although the incidence of glenoid revision

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