Posterosuperior displacement due to rotator cuff tears

Wei-Ren Su, Jeffrey E. Budoff, Zong Ping Luo

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Purpose: To compare the effects of different-sized anterosuperior and posterosuperior rotator cuff tears (RCTs) and the effects of long head of the biceps tendon (LHB) loading on posterosuperior glenohumeral translation. Methods: Ten cadaveric shoulders were subjected to posterosuperior loading in the intact state and with sequentially larger anterosuperior and posterosuperior RCTs. Glenohumeral translation was measured with and without LHB loading. Results: At 50 N of force, cutting the superior half of the infraspinatus led to significantly greater posterosuperior translation than did cutting the superior half of the subscapularis (8.9 mm v 5.9 mm, P =.0179), and cutting the entire infraspinatus led to significantly greater posterosuperior translation compared with cutting the entire subscapularis (12.7 mm v 8.0 mm, P =.0003). Fifty newtons of LHB loading reduced posterosuperior translation in the intact specimen, as well as for all sizes of anterosuperior and posterosuperior RCTs (P <.05). The percentage decrease in posterosuperior glenohumeral translation with LHB loading increased as the size of the RCT increased, varying from 16% to 43%. Comparing these results with those previously published, we found that for anterosuperior RCTs, loading the LHB decreased translation significantly more in the anterosuperior direction than the superior and posterosuperior directions for supraspinatus and 2-tendon tears. For posterosuperior RCTs, there was no difference in the effect of LHB loading between anterosuperior and posterosuperior translation. Conclusions: The infraspinatus is a major dynamic restraint against posterosuperior glenohumeral translation, especially its inferior half. The LHB is less effective in constraining posterosuperior translation than anterosuperior translation. Clinical Relevance: Knowledge of the biomechanics of RCTs enhances our ability to treat them.

Original languageEnglish
Pages (from-to)1472-1477
Number of pages6
JournalArthroscopy - Journal of Arthroscopic and Related Surgery
Volume27
Issue number11
DOIs
Publication statusPublished - 2011 Nov 1

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Tendons
Rotator Cuff
Rotator Cuff Injuries
Biomechanical Phenomena

All Science Journal Classification (ASJC) codes

  • Orthopedics and Sports Medicine

Cite this

Su, Wei-Ren ; Budoff, Jeffrey E. ; Luo, Zong Ping. / Posterosuperior displacement due to rotator cuff tears. In: Arthroscopy - Journal of Arthroscopic and Related Surgery. 2011 ; Vol. 27, No. 11. pp. 1472-1477.
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Posterosuperior displacement due to rotator cuff tears. / Su, Wei-Ren; Budoff, Jeffrey E.; Luo, Zong Ping.

In: Arthroscopy - Journal of Arthroscopic and Related Surgery, Vol. 27, No. 11, 01.11.2011, p. 1472-1477.

Research output: Contribution to journalArticle

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N2 - Purpose: To compare the effects of different-sized anterosuperior and posterosuperior rotator cuff tears (RCTs) and the effects of long head of the biceps tendon (LHB) loading on posterosuperior glenohumeral translation. Methods: Ten cadaveric shoulders were subjected to posterosuperior loading in the intact state and with sequentially larger anterosuperior and posterosuperior RCTs. Glenohumeral translation was measured with and without LHB loading. Results: At 50 N of force, cutting the superior half of the infraspinatus led to significantly greater posterosuperior translation than did cutting the superior half of the subscapularis (8.9 mm v 5.9 mm, P =.0179), and cutting the entire infraspinatus led to significantly greater posterosuperior translation compared with cutting the entire subscapularis (12.7 mm v 8.0 mm, P =.0003). Fifty newtons of LHB loading reduced posterosuperior translation in the intact specimen, as well as for all sizes of anterosuperior and posterosuperior RCTs (P <.05). The percentage decrease in posterosuperior glenohumeral translation with LHB loading increased as the size of the RCT increased, varying from 16% to 43%. Comparing these results with those previously published, we found that for anterosuperior RCTs, loading the LHB decreased translation significantly more in the anterosuperior direction than the superior and posterosuperior directions for supraspinatus and 2-tendon tears. For posterosuperior RCTs, there was no difference in the effect of LHB loading between anterosuperior and posterosuperior translation. Conclusions: The infraspinatus is a major dynamic restraint against posterosuperior glenohumeral translation, especially its inferior half. The LHB is less effective in constraining posterosuperior translation than anterosuperior translation. Clinical Relevance: Knowledge of the biomechanics of RCTs enhances our ability to treat them.

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