Korkie E1, Headland K1, Bester C1, Maligana F1, Gaia N1, van Rooyen J-A1, Schalkwyk J1
1University of Pretoria, Physiotherapy, Pretoria, South Africa
Background: Normal shoulder biomechanics depends on the extensibility as well as strength of the muscles surrounding the shoulder joint. Extensibility of the pectoralis minor muscle allows the scapula to go into full upward rotation and posterior tipping, resulting in ideal positioning of the glenoid fossa. If pectoralis minor is shortened, the scapula is in a downward rotated and anteriorly tipped position, which could lead to a decrease in sub-acromial space and ultimately to joint pathology. The pectoralis minor index (PMI) is used as an expression of pectoralis minor length, taking soft tissue and body built into account for each individual. Normal PMI values have not been specified in the literature for healthy individuals aged between 45-55 years.
Purpose: The objective of this study was to determine the mean PMI of healthy
individuals aged 45-55 years. The secondary objective was to determine if there is any difference in the PMI in three different measuring positions namely: the resting position of the scapula in supine, when the scapula is actively retracted in supine and when the scapula is passively taken into full retraction.
Methods: A quantitative non-experimental cross-sectional study design was used.
The study was conducted in the Physiotherapy department, at the University of Pretoria, South Africa. Participants were included if they were aged between 45 and 55 years with no shoulder pathology. Participants were excluded if they had shoulder pain when the shoulder quadrant test was performed. A total of 40 participants were included, 27 females and 13 males. The coracoid process and fourth costo-sternal junction were marked as anatomical markers for pectoralis minor. The participants were positioned in supine to eliminate the effect of gravity on the scapula, the elbows were flexed and hands placed on the abdomen to eliminate passive insufficiency of the biceps brachii muscle. The distance between the anatomical markers were measured with a Vernier® calliper (ICC 0.96). Three measurements were done in each position. The average of the three measurements, in each position, were used to calculate the PMI.
Results: The mean PMI for this group was 9.77 [±1.33] on the dominant side and 9.44 [±1.09] on the non-dominant side. A significant difference (p 0.00) in PMI was found between the actively retracted position (dominant side (9.78 [±1.09]) and non-dominant side (9.83 [±1.06]) and the passively stretched position (dominant side (10.16 [±1.08]) and non-dominant side (10.02 [±1.08]).
Conclusion(s): The significant difference between the passively stretched position and the actively retracted position could imply that the available range allowed by pectoralis minor was not actively used by the participant.
Implications: Pectoralis minor extensibility is often seen as a contributing factor to shoulder pathology. The results of this study imply that the inner range strength of the
scapula retractor muscles in combination with pectoralis minor extensibility are equally important for optimum range and shoulder function.
Keywords: PMI, Scapula, Pectoralis minor
Funding acknowledgements: University of Pretoria
Purpose: The objective of this study was to determine the mean PMI of healthy
individuals aged 45-55 years. The secondary objective was to determine if there is any difference in the PMI in three different measuring positions namely: the resting position of the scapula in supine, when the scapula is actively retracted in supine and when the scapula is passively taken into full retraction.
Methods: A quantitative non-experimental cross-sectional study design was used.
The study was conducted in the Physiotherapy department, at the University of Pretoria, South Africa. Participants were included if they were aged between 45 and 55 years with no shoulder pathology. Participants were excluded if they had shoulder pain when the shoulder quadrant test was performed. A total of 40 participants were included, 27 females and 13 males. The coracoid process and fourth costo-sternal junction were marked as anatomical markers for pectoralis minor. The participants were positioned in supine to eliminate the effect of gravity on the scapula, the elbows were flexed and hands placed on the abdomen to eliminate passive insufficiency of the biceps brachii muscle. The distance between the anatomical markers were measured with a Vernier® calliper (ICC 0.96). Three measurements were done in each position. The average of the three measurements, in each position, were used to calculate the PMI.
Results: The mean PMI for this group was 9.77 [±1.33] on the dominant side and 9.44 [±1.09] on the non-dominant side. A significant difference (p 0.00) in PMI was found between the actively retracted position (dominant side (9.78 [±1.09]) and non-dominant side (9.83 [±1.06]) and the passively stretched position (dominant side (10.16 [±1.08]) and non-dominant side (10.02 [±1.08]).
Conclusion(s): The significant difference between the passively stretched position and the actively retracted position could imply that the available range allowed by pectoralis minor was not actively used by the participant.
Implications: Pectoralis minor extensibility is often seen as a contributing factor to shoulder pathology. The results of this study imply that the inner range strength of the
scapula retractor muscles in combination with pectoralis minor extensibility are equally important for optimum range and shoulder function.
Keywords: PMI, Scapula, Pectoralis minor
Funding acknowledgements: University of Pretoria
Topic: Musculoskeletal: upper limb; Musculoskeletal: peripheral; Sport & sports injuries
Ethics approval required: Yes
Institution: University of Pretoria
Ethics committee: Faculty of Health Sciences Research and Ethical Committee
Ethics number: 534/2017
All authors, affiliations and abstracts have been published as submitted.
