Isokinetic testing of the shoulder rotator muscles of older individuals with shoulder pathology: An integrative review
Abstract
BACKGROUND:
Shoulder pathology is common, particularly in older adults. This pathology often involves the muscles of the shoulder, particularly those of the rotator cuff. Although there are many procedures for measuring muscle weakness and imbalance of the shoulder rotator muscles, isokinetic dynamometry is probably considered the gold standard.
OBJECTIVE
: To describe the use and findings of isokinetic testing of the shoulder rotator muscles in patients with shoulder disorders.
METHODS:
A PubMed search was performed using the string “isokinet* AND rotator cuff.” Thereafter, a secondary hand search was conducted. Original articles that reported isokinetic measures of the shoulder rotators in older patients with orthopedic shoulder disorders were identified, summarized, and critically appraised.
RESULTS:
Thirty-four relevant articles were found. The articles largely support the validity, reliability, and responsiveness of isokinetic strength measures of shoulder rotation strength in patients with shoulder pathology.
CONCLUSIONS:
The literature provides support for the isokinetic measurement of rotator muscle performance in patients with shoulder pathology. However, it is not always practical in the clinical setting.
1.Introduction
Shoulder pain and dysfunction are common, particularly among older adults [1]. Pathology of the shoulder rotator muscles, most notably those of the rotator cuff (RTC) is often responsible for this pain and dysfunction [2]. Injuries of the RTC account for numerous physician and physical therapy visits [1, 3]. Muscle strength testing is a fundamental component of the assessments conducted during these visits [4].
Although there are a number of ways in which strength of the shoulder rotator muscles can be assessed, isokinetic testing is considered by many to be the gold standard. The purpose of this review is to describe isokinetic testing procedures applicable to the shoulder rotator muscles, and findings of the procedures, among older adults with shoulder pathology.
2.Methods
Potentially relevant articles were identified by a search of PubMed on March 4, 2019. The search string used was “isokinet* AND rotator cuff.” A hand-search was also conducted. Article titles and abstracts, and where warranted full text, were examined to determine whether articles identified by the searches addressed the isokinetic testing of the shoulder internal and/or external rotator muscles in patients with orthopedic shoulder pathology. In addition to the aforementioned, inclusion required that an article focused on participants over 50 years of age. To be comprehensive, and in acknowledgement of the impact of the RTC on overall shoulder strength and function [5], the results of the isokinetic testing of other shoulder motions (e.g., flexion) were included when provided. Articles were excluded if they were reviews, written in languages other than English, conducted on only healthy individuals or on patients with primarily neurologic conditions such as stroke, or did not provide procedural specifics or quantitative findings.
Results were collated and summarized in a table. The Table included information about participants (country of origin, number, shoulder pathology, and age), testing procedures, and findings relative to clinimetric properties.
3.Results and discussion
The PubMed search identified 148 potentially relevant articles published since 1985. An additional 5 articles were identified by hand searches. After applying the inclusion and exclusion criteria to the title and abstract, 81 articles were identified as potentially relevant. From these, 34 articles were found to be appropriate for inclusion. The main reasons for exclusion were the use of only young and/or healthy participants or incomplete data. Relevant information from included articles is summarized alphabetically by author in the Table [6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39].
Table 1
Summary of studies describing the isokinetic measurement of strength in chronic obstructive pulmonary disease
| Study | Participants | Procedures | Findings |
|---|---|---|---|
| Alta et al.(2014) [6] | Dutch undergoing total ( | Biodex System 3 dynamometer measured shoulder abduction, adduction, external & internal rotation strength (PT) @60 | Validity: strength after total shoulder arthroplasty SGNF |
| Analan et al.(2015) [7] | Turks with rotator cuff lesions treated with true ( | Biodex System 3 dynamometer measured shoulder external & internal rotation strength (PT) @60 | Validity: shoulder strength not SGNF correlated with rotator cuff pathology grade. Responsiveness: no SGNF difference in strength between real & sham ultrasound. |
| Baydar et al.(2009) [8] | Turks with conservatively treated full-thickness supraspinatus tears ( | Cybex Norm dynamometer measured bilateral shoulder abduction, external & internal rotation strength (PT) @60 | Responsiveness: strength of all motions of involved side |
| Bigoni et al.(2009) [9] | Italians undergoing 1 of 2 different types of arthroscopic repair for full-thickness rotator cuff tear ( | Technogym Rev 7000 VX dynamometer measured shoulder external & internal rotation strength (PT) @60 | Responsiveness: strength on the operated side |
| Colliver et al. (2016) [10] | Australians with full-thickness supraspinatus tears who underwent acromioplasty ( | Biodex dynamometer measured concentric shoulder flexion, external & internal rotation strength (PT) @60 | Validity: no SGNF strength difference between subjects with intact tendons, tendinopathy or partial-thickness re-tears. |
| Cools et al. (2006) [11] | Belgians with full-thickness rotator cuff tears ( | LIDO dynamometer measured bilateral shoulder external & internal rotation strength (PT) @60 | Validity: pre-op strength on the operated side of the rotator cuff tear group @60 |
| Costantino et al. (2014) [12] | Italians with proximal humerus fractures ( | Biodex System 3 dynamometer measured bilateral concentric shoulder flexion & extension strength (PT) @180 | Validity: SGNF correlation between CMS & all peak torque parameters ( |
| Davidson and Rivenburgh (2000) [13] | Americans with full-thickness rotator cuff repairs ( | Lido Active dynamometer measured B⃝ shoulder flexion, extension, external & internal rotation strength (PT) @60 | Validity: SGNF |
| Demirors et al. (2009) [14] | Turks who underwent open rotator cuff repair ( | Cybex 770 Norm dynamometer measured shoulder abduction, adduction, flexion, extension, external & internal rotation strength (PT) @60 | Validity: SGNF correlation between tear type & extension strength at all velocities & internal rotation @120 |
|
Table 1, continued | |||
|---|---|---|---|
| Study | Participants | Procedures | Findings |
| Ellenbecker et al. (2006) [15] | Americans with full thickness rotator cuff tears ( | Cybex 6000 dynamometer measured bilateral shoulder external & internal rotation strength (PT) @90 | Validity: operated side external rotation was |
| Ghandour et al. (2019) [16] | Egyptians with repaired complete rotator cuff tears who wore either a pouch arm sling ( | Biodex System 3 dynamometer measured bilateral shoulder external & internal rotation strength (PT) @60 | Validity: no SGNF strength difference between sides at any velocity. CMS score & PT SGNF correlated at each velocity ( |
| Hartsell (1993) [17] | Canadians receiving rotator cuff repair with acromioplasty ( | Cybex II dynamometer measured bilateral shoulder external & internal rotation strength (PT) in neutral & 90 | Validity: PT at slower velocities SGNF |
| Itoi et al.(1997) [18] | Japanese with unilateral partial- ( | Cybex 340 dynamometer measured bilateral shoulder abduction, adduction, external & internal rotation strength (PT) & total work @60 | Validity: after involved side injection abduction & external rotation strength remained SGNF |
| Keen et al.(2006) [19] | Americans after massive rotator cuff tear reconstruction using long head of triceps brachii ( | Biodex Multi-Joint System 3 measured bilateral shoulder external & internal rotation & elbow extension strength (PT) @60 | Reliability: test-retest ICC |
| Kirschenbaum et al. (1992) [20] | Americans with rotator cuff tears treated surgically ( | Cybex II dynamometer measured bilateral shoulder external rotation, flexion, & abduction strength (PT) @90 | Validity: no side to side differences @12 months. Responsiveness: strength @6-month post-op SGNF |
| Krischak et al.(2013) [21] | Germans with unilateral rotator cuff tears treated conservatively ( | Biodex Multi-Joint System 3 dynamometer measured shoulder abduction, adduction, external & internal rotation strength (PT) @60 | Validity: after treatment no SGNF difference between groups for pain, CMS, range of motion, or strength. |
| Land et al. (2016) [22] | Australians with subacromial impingement syndrome ( | Cybex Humac Norm dynamometer measured shoulder external & internal rotation strength (PT) @60 | Reliability: control group PT ICC |
| Leroux et al. (1995) [23] | French patients with subacromial impingement syndrome who underwent anterior acromioplasty ( | Biodex Multi-Joint system dynamometer measured bilateral shoulder external & internal rotation strength (PT) @60 | Validity: no SGNF strength difference between sides. Rotation strength in men SGNF |
| Lubiatowski et al. (2013) [24] | Polish patients following rotator cuff repair ( | Biodex System 3 dynamometer measured shoulder external & internal rotation strength (PT) @90 | Validity: external rotation strength, average work & power in complete re-tear group SGNF |
|
Table 1, continued | |||
|---|---|---|---|
| Study | Participants | Procedures | Findings |
| Oh et al. (2009) [25] | South Koreans with shoulder pain with ( | Biodex System 3 dynamometer measured bilateral shoulder abduction & external rotation strength (PT). Velocity not provided. | Validity: SGNF correlations between serum vitamin D & bilateral abduction ( |
| Oh et al. (2010) [26] | South Koreans with unilateral rotator cuff tears ( | Biodex System 3 dynamometer measured bilateral shoulder abduction, external & internal rotation strength (PT) & total work @60 | Validity: pre-op peak torque SGNF correlated with manual muscle testing scores ( |
| Oh et al. (2010) [27] | South Korean men ( | Biodex System 3 dynamometer measured bilateral shoulder abduction, external & internal rotation strength (PT) @60 | Validity: operated side strength SGNF |
| Petriccioli et al. (2016) [28] | Italians with 1 of 2 types of latissimus dorsi transfer ( | Biodex System 3 dynamometer measured bilateral shoulder flexion, extension, external & internal rotation strength (PT) @210 | Validity: flexion & external rotation strength in men SGNF |
| Pilge et al.(2012) [29] | Germans who underwent rotator cuff repair ( | Cybex-Isokinetic dynamometer measured bilateral shoulder abduction, flexion, external & internal rotation strength (PT) @60 | Validity: no SGNF difference in strength in patients with or without osteolytic changes in surgical bio-anchors. |
| Porcellinni et al.(1996) [30] | Italians with rotator cuff tears ( | Lido dynamometer measured bilateral shoulder external & internal rotation strength (PT) @60 | Validity: recovery of strength SGNF correlated with age ( |
| Rhee et al. (2018) [31] | South Koreans with full-thickness rotator cuff tears receiving continuous ropivacaine ( | Biodex System 3 dynamometer measured bilateral shoulder abduction, external & internal rotation strength (PT), pre-op & 1-year post-op. | Responsiveness: strength SGNF |
| Rokito et al. (1999) [32] | Americans with large or massive chronic rotator cuff tears ( | Biodex dynamometer measured bilateral shoulder flexion, extension, abduction, adduction, external & internal rotation strength (PT) @60 | Responsiveness: post-op flexion, abduction & external rotation strength of operated side SGNF |
| Verdano et al. (2013) [33] | Italians with full-thickness rotator cuff tears who underwent arthroscopic repair ( | Biodex dynamometer measured bilateral shoulder flexion, extension, external & internal rotation strength (isometric, isotonic & PT), total work, & average power @90 | Validity: no SGNF difference between sides for any condition. |
|
Table 1, continued | |||
|---|---|---|---|
| Study | Participants | Procedures | Findings |
| Walmsley and Hartsell (1992) [34] | Canadians who underwent rotator cuff repair ( | Cybex II dynamometer measured bilateral shoulder flexion, extension, abduction, adduction, external & internal rotation strength (PT) @60 | Validity: operated side flexion strength at all speeds & external rotation @60 |
| Wang et al. (2015) [35] | Australians after arthroscopic supraspinatus repair who received ( | Biodex dynamometer measured bilateral shoulder external rotation & flexion strength (PT) & total work @60 | Validity: no SGNF differences between groups for strength or total work. |
| Yen (2005) [36] | Canadians who underwent open rotator cuff repair ( | Cybex II dynamometer measured bilateral shoulder flexion, abduction & external rotation strength (PT) @60 | Validity: involved side abduction strength @120 |
| Yoon et al. (2013) [37] | South Koreans with partial- ( | Biodex System 3 dynamometer measured bilateral shoulder internal rotation strength (PT) @60 | Validity: the lift off test, internal rotation lag sign & belly press test are SGNF correlated with internal rotation strength deficits ( |
| Yoon et al. (2018) [38] | South Koreans who underwent full-thickness rotator cuff repairs ( | Biodex System 3 dynamometer measured bilateral shoulder abduction, external & internal rotation strength (PT & total work) @60 | Validity: external rotation & abduction strength SGNF |
| Zuckerman et al.(2000) [39] | Americans with complete supraspinatus & infraspinatus ruptures who underwent hemiarthroplasty ( | Biodex dynamometer measured shoulder flexion, abduction & external rotation strength (PT) pre-op. 6/15 shoulders also tested 28.2 months post-op. | Responsiveness: post-op flexion (not external rotation or abduction) strength on operated side SGNF |
SGNF
The Table shows that isokinetic dynamometers have been used extensively to measure strength in individuals with shoulder pathology. Studies addressing isokinetic testing of shoulder rotation strength have been conducted in at least 13 different countries, but testing is reported most widely in the United States, followed by Italy, and South Korea. The mean age of individuals participating in collated studies ranged from 50.4 to 73 years. The most common pathology noted was RTC tears with only 3 studies focused on some other diagnosis (e.g., humeral fracture). Many of these studies incorporated post-surgical measures of shoulder rotation strength. The most common time frame was 12 months post-surgery.
In most studies isokinetic strength was measured with some model of Biodex. However, some model of Cybex was used in over 10 studies. Two other brands of isokinetic dynamometer were used in a few studies. Isokinetic testing was carried out at 8 different velocities between 60
The overall validity of isokinetic testing is generally supported by findings of consistently greater peak torque in men than in women [23, 28], in younger compared with older individuals [30], in the uninvolved than in the injured shoulder [11, 15], and in control groups than in patients with shoulder pathology [11, 22].
The most frequently encountered outcome measure across studies was the Constant-Murley Score (CMS) [6, 9, 11, 12, 13], with most studies showing a fair to high correlation between peak torque and overall shoulder function as measured by the 100-point CMS [40].
The validity of isokinetic testing for patients with RTC pathology is supported by the consistent finding of inverse correlations between peak torque and fatty degeneration in the rotator cuff [14, 25, 26, 38]. The utility of isokinetic testing for detecting grades of RTC tears or partial tears is inconsistent [7, 10, 14, 18, 24, 26, 30]. Isokinetic testing is more accurate in diagnosing complete tears of the RTC [18, 23, 24, 26].
We found two studies examining the test-retest reliability of peak torque measurements. The reliability coefficients (ICCs) reported in the studies were all 0.85 or higher [19, 22].
Responsiveness is represented by changes in peak torque over time. Relevant changes in patients with RTC lesions include differences in torques measured before and after surgery [11, 20, 30, 31, 32, 39] or before and after conservative treatment [8, 21]. After surgery there is an initial decrease in peak torque (for approximately 3 months) followed by steady increases thereafter [9, 11, 20, 31]. However, the influence of rehabilitation programs on recovery was not sufficiently described in most studies with some showing continued deficits for certain motions for up to 2 years after surgery [19, 27, 34, 36] while others showed no significant difference after 12–48 months [11, 17, 20, 23, 33, 34]. Likewise, the evidence supports an increase in peak torque after conservative treatment [8, 9].
The findings of this review should be interpreted with caution as there is considerable variability between studies in testing velocities, positions of the participants’ bodies and the upper extremity, movements performed, comparison groups, time frames, and operative procedures. Strength comparisons included side to side, control group, the injured extremity at different time frames, or some combination of these. However, measurements of strength utilizing bilateral comparisons did not always specify the criteria for identifying significant strength deficits. For instance, it may be expected that the dominant upper extremity is 10–15% stronger than the non-dominant upper limb [41] and statistical difference may not equate with clinical significance. It should also be noted that while the focus of this paper was intended to be on older adults, most of the studies involved the young-old. The practicality and utility of isokinetic testing of the shoulder rotator muscles of middle-old and oldest-old remains largely unexplored.
Finally, a single bibliographic database was used. While it is doubtful that the inclusion of additional databases would have markedly altered the results, such an expansion may have added to the evidence for the conclusions presented. A more systematic review may have also allowed for a meta-analysis of some variables and for a quality assessment of included articles.
4.Conclusions
Muscular weakness and imbalance of the RTC and surrounding muscles are important symptoms of shoulder pathology that can be objectively measured with isokinetic testing. This review supports the reliability, validity, and responsiveness of isokinetic measurements of rotator muscle performance in young-old patients with shoulder pathology. However, it is not always practical in the clinical setting
Conflict of interest
The author declares no conflict of interest.
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