Radiographic Study of Humeral Stem in Shoulder Arthroplasty After Lesser Tuberosity Osteotomy or Subscapularis Tenotomy

RADIOGRAPHIC DATA

There was no significant difference in preoperative HAD between the LTO and ST groups (9.5 ± 2.4 mm vs 10.9 ± 2.7 mm, P = .11). The immediate postoperative HAD was statistically significant between the LTO and ST groups (11.9 ± 3.7 mm vs 15.9 ± 4.5 mm, P = .005). There was as statistically significant difference noted in the final follow-up films between the LTO and ST groups (11.8 ± 3.2 mm vs 14.5 ± 3.9 mm, P = .025) (Table 2). 

Abbreviations: LTO, lesser tuberosity osteotomy; ST, subscapularis tenotomy.

There were no statistically significant differences found in subsidence between LTO and ST groups at final follow-up (2.8 mm ± 3.1 mm vs 2.5 mm ± 3.1 mm, P = .72) (Table 2). No statistically significant difference was noted in the subluxation index between the LTO and ST groups (0.55% ± .06% vs 0.54% ± 0.07%, P = .45), but there was a statistically significant difference noted postoperatively between the LTO and ST groups (0.55% ± 0.09% vs .48% ± 0.05%, P = .015) (Table 2).

Two stems were noted to have lucent lines >2 mm, both within the ST cohort. Each had 1 stem zone >2 mm, 1 in zone 7, and 1 in zone 4. No statistically significant difference was identified between the LTO and ST groups (0/15 vs 2/24, P = .51) (Table 2).

FUNCTIONAL OUTCOMES

Study patients were evaluated using functional outcome scores, including the Constant, WOOS, and DASH scores (Table 3). 

Abbreviations: DASH, disabilities of the arm, shoulder and hand; WOOS, Western Ontario Osteoarthritis of the Shoulder.

No statistically significant differences were noted in the DASH scores (8.4 ± 6.6 vs 13.8 ± 4.9, P = .13) or Constant scores (83.3 ± 9.1 vs 81.8 ± 10.1, P = .64) between the LTO and ST cohorts. There was a statistically significant difference between the WOOS scores (93.3 ± 5.3 vs 81.5 ± 20.8, P = .013). Because separate radiographic reviews were done by 3 independent personnel at 3 different times, it was important to ensure agreement among the reviewers. This was compared using the intraclass correlation coefficients. In the statistical analysis completed, the intraclass coefficients showed the 3 reviewers agreed with each other throughout the radiographic analysis (Table 4).

Abbreviations: CI, confidence interval; HAD, humeral acromial distance; ICC, intraclass correlation coefficient; SI, subluxation index.

DISCUSSION

At final follow-up, we identified no statistically significant difference between the LTO and ST patients in subsidence, lucent lines >2 mm, or functional outcomes (Constant and DASH scores) in patients who underwent TSA with the same proximal collar press-fit humeral stem. In regard to the functional outcome scores, although the WOOS score was statistically significant (P = .013) between the LTO and ST cohorts, we do not feel that this is clinically relevant because it does not reach the minimal clinically important difference threshold of 15 points.⁸

A statistically significant difference was noted in postoperative subluxation index but was not clinically relevant, because the values between the LTO and ST groups (0.55 vs 0.48) still showed a centered humeral head. Gerber and colleagues³ discussed using a value of 0.65 as a measure of posterior humeral head subluxation, whereas Walch and colleagues¹² defined posterior humeral head subluxation as a value >0.55. On the basis of these numbers, the values obtained in this study demonstrated that the postoperative values were still centered on the glenoid, and therefore were not clinically significant.^3,12

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