Is there a relation between rotator cuff injury and core stability?

Abstract

BACKGROUND:

Strong core stabilization not only minimizes the load on the vertebral column, but also improves strength and endurance of peripheral joints, and enables the energy transfer to distal segments. Despite the current interest surrounding core stability, none of the studies investigated the effect of core stability on the formation of rotator cuff tear or healing after repair.

OBJECTIVE:

To determine the relationship between core stability and upper extremity functional performance in patients who underwent rotator cuff repair surgery and to compare those with healthy subjects of similar age.

METHODS:

Patients who underwent rotator cuff repair (RC repair group, $n=$ 58 patient) and healthy subjects of the similar age group (control group, $n=$ 114) were included in the study. The mean age was 55.03 $\pm$ 9.84 years in the RC repair group and 52.71 $\pm$ 6.31 years in the control group. The RC repair group took standardized rehabilitation. The rehabilitation program did not include core strength and stability exercise. Core endurance was assessed with Flexor Endurance, Prone Bridge and Supine bridge test. Disabilities of the Arm, Shoulder and Hand (DASH), Short Form-36 (SF-36) and the Close Kinetic Chain Upper Extremity Stability (CKCUES) test were used to evaluate the upper extremity functional performance.

RESULTS:

The core endurance (prone and supine bridge test) of the control group was statistically significantly better than the RC repair group ( $p\leqslant$ 0.005). The DASH-T, SF-36 and CKCUES scores of the control group were also statistically significantly better.

CONCLUSION:

The neuromuscular system should be considered as a whole, and addition of the core stabilization exercises to an effective rehabilitation program after RC repair surgery may be beneficial.

Keywords

Rotator cuff core stability upper extremity quality of life

1. Introduction

The shoulder joint complex requires the coordinated movement of many muscle groups and has an important role in daily living activities [1]. Neuromuscular control and stability impairments and injuries negatively affect shoulder function. Neuromuscular control of the shoulder joint is provided by rotator cuff (RC) muscle activation by the management of the nervous system [2, 3].

RC pathologies and tears affect 30–50% of patients over 50 years of age and surgery rates increase substantially every year [4, 5]. In a recent study, retear after rotator cuff repair is reported in approximately 20% of cases and caused by various factors such as inadequate repair, biological failure to heal, and inappropriate rehabilitation programs after surgery [6].

The relationship between core stability and extremity performances was generally studied in athletes. However, most of the studies focused on its relationship with lower extremity [7, 8, 9]. Core stability is becoming an increasingly popular topic in literature with regards to enhanced of extremity functions and prevention of injuries in athletes [10, 11, 12]. Although there is limited evidence supporting the link between core stability and upper extremity injuries and athletic performance amongst athletes who participate in baseball, football, or swimming, many elite athletes undertake core exercises as part of their training program [12, 13]. The addition of core exercises to the shoulder rehabilitation program in overhead athletes may help to close the gap between initial rehabilitation exercises and later functional rehabilitation exercises [14].

Strong core stabilization not only minimizes the load on the vertebral column, but also improves strength and endurance of peripheral joints, and enables the energy transfer to distal segments [15, 16]. The relationship between strength and endurance of core muscles and shoulder problems has become especially interesting, and authors suggested that an effective rehabilitation program planned for prevention or treatment should include core stabilization exercises [17, 18, 19].

Despite the current interest surrounding core stability, we have not found a study about the effect of core stability on the formation of RC tear or healing after repair. The purpose of this study is to determine the relationship between core stability and upper extremity functional performance in patients who underwent RC repair surgery and to compare those with healthy subjects of similar age.

2. Methods

2.1 Subjects and allocation of participants

Patients who underwent rotator cuff repair at the Pamukkale University, Department of Orthopedics and Traumatology between August 2014–July 2016 (RC repair group) and healthy subjects of similar age (control group) were included in the study. The study was approved by the Pamukkale University Non-invasive Clinical Researches Ethics Committee (60116787-020/49572). Written informed consent was obtained from all participants.

Inclusion criteria for the RC repair group were as follows: patients who underwent RC repair surgery and do not have retear and chronic diseases that may adversely affect healing. An inclusion criterion for the control group was: no prior history of shoulder injury or surgery. Exclusion criteria for both groups were as follows: having chronic diseases that may adversely affect shoulder functions, using corticosteroid, previous spinal, lumbar pathology or surgery, and having lower back pain or a neuromuscular disease.

2.2 Interventions

The initial RC repair group study sample consisted of 67 patients. After surgery, all patients were subsequently referred to the clinical physical therapist for initiation of rehabilitation (within a range of 2 days to 15 days post-surgery) and followed the standardized rehabilitation program. The program did not include exercises on core strength and stability. Individual home exercises were given at all phases. Each exercise session consisted of three sets of 15 repetitions twice a day for 8 weeks. Standardized rehabilitation program is as follows:

0–2 weeks postoperative: immobilization, cryo- therapy, pendulum exercises, hand, wrist, and elbow active and passive range of motion (ROM), shoulder passive ROM (0–90 ${}^{\circ}$ ) and scapular plane rotation (0–45 ${}^{\circ}$ ). 2–4 weeks postoperative: continue the above, shoulder isometric exercises, Wand exercises and scapular strengthening. 4–5 weeks postoperative: continue the above, active ROM all planes. 6–8 weeks postoperative: full active ROM, progressive resistive exercises as tolerated.

2.3 Examinations

The assessments of the RC repair group were performed one year after the surgery.

Shoulder Pain and Disability Index (SPADI) was developed by Roach et al. [20]. This is a self-administered questionnaire that aims to measure shoulder pain and disability. The SPADI has been translated into Turkish and is a reliable and valid tool for assessing pain and disability in patients with shoulder pathology [21]. It contains 5 items pain scale and 8 items disability scale which is scored by a numeric rating scale that ranges from 0 (no pain/no difficulty) to 10 (worst pain imaginable/so difficult it required help). A higher score indicates greater pain-related disability [20].

Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire is a self-administered 30-item upper-extremity disability/symptom scale introduced by the “American Academy of Orthopedic Surgeons”, the Council of the “Musculoskeletal Specialty Societies” and the “Institute for Work and Health” [22]. It aims to measure disability and symptoms related to upper extremity musculoskeletal disorders. The Turkish version of the DASH has been published by Duger et al. The scores range from 0 (no disability) to 100 (most severe disability).

Short Form-36 (SF-36) Health Survey was developed by the Rand Corporation to assess the self-perceived health-related quality of life, and the Turkish reliability and validity study conducted by Kocyıgıt et al. It consists eight scaled scores; physical functioning, role physical, bodily pain, general health, vitality, social functioning, role emotional, and mental health. Each scores range from 0 to 100, with higher scores representing better self-reported quality of life.

Western Ontario Rotator Cuff (WORC) index is a disease-specific quality of life questionnaire that developed by Kirkley et al. for patients with disorders of the rotator cuff. It has been translated and validated in Turkish [23]. Total percentage scores range from 0 to 100, with higher scores representing worst quality of life. We conducted this index only RC repair group.

The Close Kinetic Chain Upper Extremity Stability Test (CKCUES test) is an objective clinical performance test which assesses upper extremity function and stability. It can be used to assess subjects with shoulder conditions. The test consists in how many times, during 15 seconds, the subject assuming a push-up position is able to touch his/her supporting hand with the swinging hand. The test was performed in a modified (or kneeling) push position in females, as recommended by the original proposers [24].

The Flexor endurance test measures the endurance of the anterior abdominal wall by asking the person to hold a sit-up position as long as they can. The isometric sit-up position is held at 60 ${}^{\circ}$ from a supine position with hips and knees at 90 ${}^{\circ}$ and arms positioned across the chest. The test started when the bolster is slid 10 cm away from the subject’s back and was stopped when the subject back touches the bolster [10].

Prone bridge and Supine bridge test [25] were performed for core endurance. For the prone bridge test, subjects began in the prone position propped on the elbows. The elbows were spaced shoulder-width apart, and the feet were set with a narrow base, but not touching. The subject then raised the pelvis from the floor so that only the forearms and the toes were in contact with the floor. The shoulders, hips and ankles were maintained in a straight line. The position was held until fatigue prevented maintenance of the test position. The time duration between the assumption of the position and the termination of it was counted as the endurance hold duration of the test. For the supine bridge test, the subject began in the supine position with knees flexed 90 degrees and the soles of the feet on the floor with a narrow base, but not touching. The thighs could not be in contact. The subject then raised the pelvis from the floor so that the shoulders, hips, and knees were maintained in a straight line. The position was held until fatigue prevented maintenance of the test position. If the subject reached 2 mins, the dominant leg was extended at the knee, removing one point of support.

2.4 Statistical analysis

The obtained data were analyzed using the Statistical Package for the Social Sciences (version 21; SPSS Inc., Chicago, IL, USA). Continuous variables were described as mean $\pm$ standard deviation. Categorical variables were presented as absolute number and percentage. Normality of data distribution was assessed by the Kolmogorov Smirnov test. The Student t-test was used to compare the quantitative variables of the groups. Pearson Correlation Coefficient was used to determine the relationships between core stability and upper extremity functional performance variables. In addition, comparisons of continuous variables between groups were done by analysis of covariance (ANCOVA) with adjustment of age. The Significance level in all the tests was considered as $p\leqslant$ 0.05.

3. Results

In RC repair group 9 patient excluded from the study because of postoperative infection ( $n=$ 1), retear ( $n=$ 2), directed to different treatments due to persistent pain ( $n=$ 2), unwilling to come to the assessments ( $n=$ 4). The final study sample consisted of 58 patients (34 females, 24 males) from RC repair group and 114 subjects (55 females, 59 males) from the control group.

Descriptive characteristics of subjects are provided in Table 1. The mean age was 55.03 $\pm$ 9.84 years in the RC repair group and 52.71 $\pm$ 6.31 years in the control group. The affected upper extremities of the RC repair group were 48.3% dominant side, 50% non-dominant side and 1.7% bilateral.

Table 1
Descriptive characteristics of subjects

	RC repair group ( $n=$ 58)		Control group ( $n=$ 114)
Variables	Min-max	X $\pm$ SD	Min-max	X $\pm$ SD	$p$
Age (y)	38–78	55.03 $\pm$ 9.84	45–70	52.71 $\pm$ 6.31	0.064
Height (cm)	150–185	162.92 $\pm$ 0.09	148–185	165.20 $\pm$ 0.08	0.125
Weight (kg)	57–110	74.84 $\pm$ 12.41	52–112	79.01 $\pm$ 11.26	0.033
BMI (kg/m ${}^{2}$ )	21.67–39.52	28.09 $\pm$ 4.16	17.99–46.67	29.09 $\pm$ 4.65	0.186
Education (year)	4–18	5.76 $\pm$ 3.39	4–18	8.96 $\pm$ 5.96	0.004
	$n$	%	$n$	%
Gender
Female	34	58.6	55	48.2
Male	24	41.4	59	51.8
Dominant extremity
Right	55	94.8	111	97.4
Left	3	5.2	3	2.6
Affected extremity
Dominant side	28	48.3	–	–
Non dominant side	29	50.0	–	–
Bilateral	1	1.7

Abbreviations: BMI, body mass index; RC, rotator cuff.

Table 2

Comparison of clinical outcome scores of RC repair and control group

Variable	RC repair group ( $n=$ 58)		Control group ( $n=$ 114)		$p$
SPADI
Pain	42.60	$\pm$ 29.24	12.02	$\pm$ 18.58	0.000
Disability	28.18	$\pm$ 24.55	6.84	$\pm$ 11.25	0.000
Total score	34.38	$\pm$ 24.97	8.83	$\pm$ 13.60	0.000
DASH-T	27.73	$\pm$ 23.26	8.27	$\pm$ 10.37	0.000
SF-36
General health perceptions	61.33	$\pm$ 24.34	63.46	$\pm$ 18.23	0.525
Physical functioning	69.21	$\pm$ 29.05	84.62	$\pm$ 20.20	0.000
Mental health	66.64	$\pm$ 23.61	67.91	$\pm$ 14.58	0.667
Social functioning	78.34	$\pm$ 27.22	86.95	$\pm$ 20.12	0.021
Role physical	49.10	$\pm$ 42.63	83.12	$\pm$ 32.98	0.000
Role emotional	55.95	$\pm$ 45.88	89.58	$\pm$ 27.86	0.000
Pain	58.21	$\pm$ 29.31	83.42	$\pm$ 21.30	0.000
Energy/vitality	57.89	$\pm$ 25.90	60.92	$\pm$ 16.86	0.361
WORC
Physical symptoms	0.31	$\pm$ 0.26	–		–
Sports/recreation	0.35	$\pm$ 0.29	–		–
Work	0.43	$\pm$ 0.33	–		–
Lifestyle	0.22	$\pm$ 0.31	–		–
Emotions	0.19	$\pm$ 0.22	–		–
Total score	30.33	$\pm$ 25.31	–		–
CKCUES test	8.32	$\pm$ 6.08	12.42	$\pm$ 4.35	0.000
Core endurance
Flexor endurance test	26.75	$\pm$ 17.65	30.96	$\pm$ 15.65	0.159
Prone bridge test	24.13	$\pm$ 17.86	31.66	$\pm$ 21.14	0.028
Supine bridge test	92.97	$\pm$ 56.83	159.77	$\pm$ 25.73	0.000

Note. Values are mean $\pm$ SD. Abbreviations: BMI, body mass index; RC, rotator cuff; SPADI, Shoulder pain and disability index; DASH-T, Disabilities of the arm, shoulder and hand; SF-36, Short Form-36; CKCUES test, The close kinetic chain upper extremity stability test.

Table 3

Comparison of means and 95% CI for clinical outcome scores using an ANCOVA model adjusted for age

	RC repair group ( $n=$ 58)		Control group ( $n=$ 114)
	Mean $\pm$ Std.Er. (%95 CI)		Mean $\pm$ Std.Er. (%95 CI)		$p$
SPADI
Pain	43.23	$\pm$ 3.21 (36.88–49.59)	11.52	$\pm$ 2.55 (6.46–16.57)	0.0001
Disability	26.93	$\pm$ 2.42 (22.15–31.72)	6.61	$\pm$ 1.92 (2.81–10.41)	0.0001
Total score	33.2	$\pm$ 2.58 (28.1–38.3)	8.5	$\pm$ 2.05 (4.44–12.55)	0.0001
DASH-T	26.46	$\pm$ 2.22 (22.07–30.84)	8.13	$\pm$ 1.83 (4.51–11.76)	0.0001
SF-36
General health perceptions	61.26	$\pm$ 2.78 (55.77–66.75)	63.38	$\pm$ 1.93 (59.58–67.19)	0.533
Physical functioning	70.49	$\pm$ 3.23 (64.1–76.88)	83.74	$\pm$ 2.67 (78.46–89.02)	0.002
Mental health	66.53	$\pm$ 2.46 (61.67–71.39)	67.92	$\pm$ 1.7 (64.55–71.28)	0.645
Social functioning	78.71	$\pm$ 3.04 (72.71–84.71)	86.59	$\pm$ 2.1 (82.43–90.74)	0.035
Role physical	50.46	$\pm$ 5.07 (40.42–60.49)	82.5	$\pm$ 4.19 (74.2–90.79)	0.0001
Role emotional	58.04	$\pm$ 4.9 (48.35–67.74)	88.85	$\pm$ 4.05 (80.83–96.86)	0.0001
Pain	57.69	$\pm$ 3.27 (51.23–64.14)	83.31	$\pm$ 2.26 (78.84–87.78)	0.0001
Energy/vitality	57.73	$\pm$ 2.76 (52.27–63.19)	60.98	$\pm$ 1.91 (57.2–64.76)	0.337
CKCUES test	8.66	$\pm$ 0.71 (7.25–10.06)	12.29	$\pm$ 0.45 (11.4–13.18)	0.0001
Core endurance
Flexor endurance test	27.06	$\pm$ 2.58 (21.97–32.15)	30.86	$\pm$ 1.52 (27.86–33.86)	0.208
Prone bridge test	24.21	$\pm$ 3.13 (18.02–30.39)	31.64	$\pm$ 1.91 (27.86–35.42)	0.045
Supine bridge test	92.4	$\pm$ 5.36 (81.81–102.99)	158.18	$\pm$ 3.42 (151.43–164.92)	0.0001

Abbreviations: RC, rotator cuff; SPADI, Shoulder pain and disability index; DASH-T, Disabilities of the arm, shoulder and hand; SF-36, Short Form-36; CKCUES test, The close kinetic chain upper extremity stability test.

Table 4

The relationship between clinical outcome scores and core endurance in RC repair group

	Core endurance						CKCUES test
Variable	Flexor endurance test		Prone bridge test		Supine bridge test
SPADI
Pain	$-$ 0.037	(0.821)	$-$ 0.361	(0.019)	$-$ 0.238	(0.112)	0.012	(0.940)
Disability	0.068	(0.678)	$-$ 0.166	(0.294)	$-$ 0.043	(0.774)	$-$ 0.090	(0.557)
Total score	0.026	(0.875)	$-$ 0.268	(0.087)	$-$ 0.135	(0.372)	$-$ 0.051	(0.741)
DASH-T	$-$ 0.042	(0.799)	$-$ 0.427	(0.004)	$-$ 0.171	(0.250)	$-$ 0.182	(0.225)
SF-36
General health perceptions	0.374	(0.019)	0.408	(0.007)	0.449	(0.002)	0.163	(0.286)
Physical functioning	$-$ 0.128	(0.438)	0.249	(0.108)	0.343	(0.020)	0.075	(0.625)
Mental health	0.160	(0.330)	0.211	(0.175)	0.141	(0.349)	0.105	(0.491)
Social functioning	0.010	(0.954)	0.227	(0.143)	0.016	(0.918)	0.295	(0.049)
Role physical	0.122	(0.461)	0.248	(0.109)	0.274	(0.065)	0.114	(0.458)
Role emotional	$-$ 0.003	(0.984)	0.026	(0.870)	0.097	(0.520)	0.200	(0.188)
Pain	0.009	(0.957)	0.293	(0.057)	0.316	(0.033)	0.313	(0.033)
Energy/vitality	0.128	(0.439)	0.351	(0.021)	0.285	(0.055)	0.138	(0.367)
WORC
Physical symptoms	$-$ 0.183	(0.309)	$-$ 0.361	(0.031)	$-$ 0.139	(0.393)	0.074	(0.656)
Sports/recreation	$-$ 0.082	(0.650)	$-$ 0.240	(0.159)	$-$ 0.044	(0.786)	$-$ 0.072	(0.662)
Work	$-$ 0.127	(0.482)	$-$ 0.293	(0.083)	$-$ 0.024	(0.881)	$-$ 0.068	(0.680)
Lifestyle	$-$ 0.069	(0.702)	$-$ 0.116	(0.501)	$-$ 0.069	(0.672)	$-$ 0.177	(0.480)
Emotions	$-$ 0.092	(0.612)	$-$ 0.190	(0.266)	$-$ 0.015	(0.929)	$-$ 0.092	(0.579)
Total score	$-$ 0.127	(0.482)	$-$ 0.277	(0.102)	$-$ 0.067	(0.681)	$-$ 0.054	(0.745)
CKCUES test	0.116	(0.481)	0.174	(0.266)	0.269	(0.070)	–

Note. Values are, correlation coefficient r and (p). Abbreviations: BMI, body mass index; RC, rotator cuff; SPADI, Shoulder pain and disability index; DASH-T, Disabilities of the arm, shoulder and hand; SF-36, Short Form-36; CKCUES test, The close kinetic chain upper extremity stability test.

Table 5

The relationship between clinical outcome scores and core endurance in the control group

	Core endurance						CKCUES test
Variable	Flexor endurance test		Prone bridge test		Supine bridge test
SPADI
Pain	$-$ 0.326	(0.003)	$-$ 0.354	(0.001)	$-$ 0.335	(0.002)	$-$ 0.118	(0.296)
Disability	$-$ 0.255	(0.023)	$-$ 0.289	(0.009)	$-$ 0.270	(0.015)	$-$ 0.180	(0.110)
Total score	$-$ 0.301	(0.007)	$-$ 0.333	(0.003)	$-$ 0.313	(0.005)	$-$ 0.115	(0.173)
DASH-T	$-$ 0.284	(0.011)	$-$ 0.350	(0.001)	$-$ 0.295	(0.008)	$-$ 0.188	(0.094)
SF-36
General health perceptions	0.377	(0.000)	0.513	(0.000)	0.364	(0.000)	0.018	(0.848)
Physical functioning	0.212	(0.058)	0.346	(0.002)	0.369	(0.001)	0.203	(0.071)
Mental health	0.141	(0.131)	0.268	(0.004)	0.045	(0.631)	$-$ 0.102	(0.278)
Social functioning	0.271	(0.004)	0.348	(0.000)	0.213	(0.023)	0.062	(0.510)
Role physical	0.241	(0.031)	0.340	(0.002)	0.304	(0.006)	$-$ 0.061	(0.593)
Role emotional	0.134	(0.235)	0.222	(0.048)	0.347	(0.002)	0.092	(0.417)
Pain	0.268	(0.004)	0.277	(0.003)	0.294	(0.002)	$-$ 0.159	(0.091)
Energy/vitality	0.073	(0.440)	0.267	(0.004)	0.066	(0.077)	0.001	(0.990)
CKCUES test	$-$ 0.057	(0.545)	0.060	(0.529)	$-$ 0.080	(0.381)	–

The comparison of clinical outcome scores of the RC repair and the control group is shown in Table 2. The SPADI ( $p=$ 0.000), DASH-T ( $p=$ 0.000) and physical functioning ( $p=$ 0.000), social functioning ( $p=$ 0.021), role physical ( $p=$ 0.000), role emotional ( $p=$ 0.000) and pain ( $p=$ 0.000) subscale scores of SF-36 and CKCUES test scores ( $p=$ 0.000) were statistically significantly better in control group. Prone ( $p=$ 0.028) and supine bridge test ( $p=$ 0.000) of the control group was statistically significantly better than RC repair group whereas no significance in flexor endurance test ( $p=$ 0.159). There were no statistically significant between groups in general health perceptions ( $p=$ 0.525), mental health ( $p=$ 0.667) and energy/vitality ( $p=$ 0.361) subscale scores of SF-36. The average WORC percentage score of the RC repair group was 30.33 $\pm$ 25.31.

Comparison of means and 95% CI.for clinical outcome scores using an ANCOVA model adjusted for age is shown in Table 3. Adjustment for ‘age’ covariate has not impact on clinical outcomes.

The correlation between core endurance and clinical outcome scores of RC repair group was presented in Table 4. Flexor endurance test showed a significant positive correlation with general health perceptions score of SF-36 ( $p=$ 0.019). Prone bridge test showed a significant negative correlation with DASH-T ( $p=$ 0.004) whereas showed a significant positive correlation with general health perceptions ( $p=$ 0.007), and energy/vitality scores ( $p=$ 0.021) of SF-36. Supine bridge test showed a significant positive correlation with general health perceptions ( $p=$ 0.002), physical functioning ( $p=$ 0.020) and pain ( $p=$ 0.033) scores of SF-36. CKCUES Test showed a significant positive correlation with social functioning ( $p=$ 0.049) and pain ( $p=$ 0.033) scores of SF-36.

The relationship between core endurance and clinical outcome scores of the control group is shown in Table 5. Flexor endurance test showed a significant negative correlation with pain ( $p=$ 0.003), disability ( $p=$ 0.023) and total scores ( $p=$ 0.007) of SPADI and DASH-T ( $p=$ 0.011) whereas showed a significant positive correlation with general health perceptions ( $p=$ 0.000), social functioning ( $p=$ 0.004), role physical ( $p=$ 0.031) and pain ( $p=$ 0.004) scores of SF-36. Prone bridge test showed a significant negative correlation with pain ( $p=$ 0.001), disability ( $p=$ 0.009) and total scores ( $p=$ 0.003) of SPADI and DASH-T ( $p=$ 0.001) whereas showed a significant positive correlation with all subscale scores of SF-36. Supine bridge test showed a significant negative correlation with pain ( $p=$ 0.002), disability ( $p=$ 0.015) and total scores ( $p=$ 0.005) of SPADI and DASH-T ( $p=$ 0.008) whereas general health perceptions ( $p=$ 0.000), physical functioning ( $p=$ 0.001), social functioning ( $p=$ 0.023), role physical ( $p=$ 0.006), role emotional ( $p=$ 0.002) and pain ( $p=$ 0.002) scores of SF-36. There was no significant correlation between SPADI, DASH-T and SF-36 with CKCUES Test.

4. Discussion

This study aimed to determine the relationship between core stability and upper extremity functional performance in patients with RC repair surgery and to compare with healthy subjects of the similar age. We found that patients who underwent RC repair surgery had poor core stability than healthy subjects of the similar age. There was a relationship between their core stability and upper extremity physical functions and symptoms, general health perceptions and pain. Furthermore, they are not capable of upper extremity function and quality of life at levels similar to control groups one year after surgery.

The effectiveness of rehabilitation programs and contents after rotator cuff surgery has been discussed in recent years [26, 27] and some researchers suggest that core stabilization exercises could be added to rehabilitation programs [28]. In our knowledge, none of the study investigates core stabilization in patients undergoing RC surgery.

The healthy neuromuscular system provides a strong core-stability during functional activities and controls the movement and strength of the terminal segments as well as the body position [12]. Neuromuscular control impairments of kinetic chain cause biomechanical changes and force imbalances during upper extremity movements, thus making the shoulder joint susceptible to injury. The few studies conducted on athletes reported that strong core stability maximizes force production and reduces the load on peripheral joints [15], while weak core stability increases the risk of injury [29] by causing shoulder and elbow pain in the upper extremity of athletes [30]. Therefore the program of preventing [30] or treating [17] shoulder injuries should include core stability training. In our study, there was a significant negative correlation between core stabilization and upper extremity function in the control group, but this relationship was not found in the RC repair group (Tables 4 and 5). This may be because the RC repair group may have poor core stability, pain, or upper extremity disability (Table 3). In addition, the effects of shoulder injury and surgical treatment may be reflected in the trunk segments (tensegrity theorem and myofascial meridian system).

In this study, we evaluated disability with SPADI and DASH-T. We determined that the functional results of the RC repair group were notably lower than the control group. We also determined that there is a negative correlation between the disability scores and core endurance. Also, durations of the prone bridge and supine bridge endurances of the control group were remarkably higher. We think that the increase in the disability decreases independence of daily life activities and that is why it causes the decreasing in the life quality. Being core area which is called the ‘power area’ of the body is powerful, makes truncus more stable and powerful. Therefore, it ensures usage of upper extremity more functional during life activities of individuals through dissemination of the force. Furthermore, core endurance scores were found to be more correlated with the parameters than the RC repair group and the relationship power was higher in the control group. In the framework of the holistic approach, we think that it should be focused on the truncus with the holistic view and basic area core exercises should be included in each treatment program.

Nevertheless, some studies have shown that core stabilization does not affect upper extremity performance [31, 32]. But reduces compensatory movement patterns during upper extremity functional activities in the traumatic elbow and wrist injuries [29]. Especially in the early postoperative period, patients present compensatory movement patterns after RC repair surgery in our clinic. We think that adding core stabilization exercises to traditional rehabilitation allow to optimal neuromuscular recovery by avoiding compensatory movements and prevent to retear caused by abnormal motion patterns.

One of the limitations of our study was that we did not have any information about the core stability of the RC repair group before the injury and subsequent surgery. In addition to this, with exception of the CKCUS test, all our outcome measures were self-reported questionnaires. It may be more appropriate to measure the results of the shoulder with objective methods. Future studies could include a larger sample size and patients with varied shoulder problems. Also, researchers could investigate the role of ipsilateral and contralateral core muscle influence. Clinical studies could be designed to respond to the following questions: “Is core stability affected in upper extremity pathology or surgery?” and “Does poor core stability lead to upper extremity pathologies?”

We observed that patients who underwent RC repair surgery had poor core stability than healthy subjects of the similar age. Considering previous studies, the results of our study may be interpreted in two ways: cause or result? The poor core stability may have resulted in RC tears, or RC tear may adversely affect core stability, and core strength is still insufficient one year after RC repair surgery.

5. Conclusion

We think that the neuromuscular system should be considered as a whole, and the addition of core stabilization exercises to an effective rehabilitation program after RC repair surgery may be beneficial.

Footnotes

Conflict of interest

None to report.

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