Ultrasound evaluation of postsurgical shoulder after rotator cuff repair: comparison of clinical results

Abstract

Background

The relationship between the imaging parameters on postoperative ultrasound (US) other than repaired tendon integrity with clinical outcome such as postoperative residual pain has not been well defined.

Purpose

To investigate whether the repaired tendon thickness and subdeltoid fluid collection after rotator cuff repair are correlated with early postoperative clinical outcome.

Material and Methods

This retrospective study included 54 patients who underwent repair of the arthroscopic rotator cuff either by suture-bridge or single-row technique and postoperative US. We assessed the relationship between the sonographic parameters, including repaired supraspinatus tendon thickness and subdeltoid fluid collection, with the clinical outcome represented by the Korean Shoulder Scoring system (KSS) score using correlation coefficients (R). Also, the subgroup analysis was done to assess the differences by surgical technique and patients’ age.

Results

There was a significant inverse relationship between the amount of subdeltoid fluid collection and degree of self-assessed pain improvement of the patients (P < 0.05), although every KSS category showed statistically insignificant tendency of inverse relationship with the fluid thickness. However, there was no statistically significant relationship between the thickness of repaired supraspinatus tendon and KSS scores. In patients aged >60 years, a statistically significant inverse relationship between thickness of subdeltoid fluid collection and difference value of the KSS scores in category of function was observed with both interpreters (P = 0.015 and P = 0.04, respectively).

Conclusion

Subdeltoid fluid collection measured on US after repair of the arthroscopic rotator cuff in the early postoperative period has significant association with the patients’ subjective clinical outcome.

Keywords

Ultrasound rotator cuff repair Korean Shoulder Scoring system (KSS)suture-bridge technique single-row technique

Introduction

Postoperative imaging is frequently performed when pain or disability occur or persist after repair of the rotator cuff. Some patients suffer from persistent shoulder pain even after successful repair, which gives rise to great concern (1,2). Postoperative shoulder pain after repair of the rotator cuff have adverse effects on rehabilitation and consequently results in poor clinical outcomes (1,2). There were several efforts to identify which preoperative factors have significant associations with persistent postoperative shoulder pain. Shin et al. (3) found that L-shaped rotator cuff tears are assumed to be the cause of intense and frequent postoperative pain and preoperative shoulder stiffness was significantly associated with postoperative pain. In contrast, Ravindra et al. (4) reported that none of the tear characteristics or demographics correlated with postoperative pain. As structural failure after rotator cuff repair is a well-known and frequent complication, postoperative imaging for assessment of the persistent shoulder pain has been generally focused on the integrity of the repaired tendon (5). To date, there have been very few studies investigating the characteristics of the healing tendon other than the integrity of the repaired tendon on postoperative imaging and their associations with the clinical outcome (6). Lasbleiz et al. (7) reported that postsurgical tendon thickness does not closely correlate with clinical outcome. Tham et al. (8) also reported a similar conclusion. Recently, Li et al. (9) reported that postoperative residual pain is associated with a high magnetic resonance imaging (MRI) signal intensity of the repaired supraspinatus tendon. Although MRI is the widely accepted modality for the evaluation of the postsurgical state of rotator cuff repair, there are some limitations associated with MRI, such as susceptible artifacts around surgical materials and high cost for evaluation (10 –12). Ultrasound (US) is a good alternative modality for the postsurgical evaluation of the repaired tendon in the presence of surgical materials, allows dynamic and repeated evaluation of the rotator cuff, and is cost-effective (5,6,10,12,13). The relationship between the imaging parameters on postoperative US other than repaired tendon integrity with clinical outcomes such as postoperative residual pain has not been well defined. As persistent shoulder pain after rotator cuff repair is not always sufficiently explained by the integrity of repaired tendon itself or by tendon thickness, we hypothesized that other structural parameters may give additional information about persistent shoulder pain. Subdeltoid fluid collection is frequently seen on postoperative imaging that may be a non-specific postoperative finding in normal postoperative rotator cuff (14). However, the relationship between subdeltoid fluid collection with clinical outcome is not known.

The aim of the present study was to investigate whether subdeltoid fluid collection and repaired tendon thickness on postoperative US after repair of the rotator cuff show any correlation with patients’ early postoperative clinical outcome at or near the third month after the surgery. We also assessed whether these sonographic parameters have different association with clinical outcomes depending on the surgical technique.

Material and Methods

Case selection

This retrospective, single-center study was approved by the Kangbuk Samsung Hospital Institutional Research Ethics Review Board (IRB) and the requirement for informed consent of the patients was waived. From January 2015 to June 2017, a total of 131 patients underwent postoperative US after arthroscopic rotator cuff repair, regardless of the presence of symptoms. After reviewing the electronic medical records, 77 cases were excluded because of insufficient evaluation of the Korean Shoulder Scoring system (KSS) score. Finally, we retrospectively evaluated the postoperative US findings of 54 consecutive patients who underwent arthroscopic rotator cuff repair either by suture-bridge or single-row technique, with sufficient preoperative and postoperative KSS scores. The patient group included 30 male patients and 24 female patients (mean age = 61.5 ± 8.6 years, age range = 45–79 years); 23 patients were aged <60 years and 31 patients were aged ≥60 years.

Preoperative evaluation

All participants were functionally evaluated using the KSS one day before the surgery by an orthopedic surgeon. The KSS includes five categories and consists of 100 points: function = 30 points; pain = 20; satisfaction = 10; range of motion (ROM) = 20; and muscle power, consisting of strength = 10 and endurance = 10 (15). The total KSS score includes 60 points that are allocated to the patient self-assessed section and 40 points to the physical examination section (15). The function category addresses the patient’s ability to perform a total of 10 daily activities scored from a score of 0 (unable to do) to the maximum score of 3 (no difficulty). The level of pain in the shoulder joint during an ordinary day was scored in the range of 0–20 points. The severity of pain was determined based on the medication used (non-steroidal anti-inflammatory drugs) and the relation with daily activities. Points were graded as follows: no pain at any time = 20; no pain at rest, but mild pain during daily activity = 15; continuous pain but not requiring drug medication = 10; continuous pain alleviated by drugs = 5; and continuous pain persisting even on medication = 0. The ROM was composed of a total of 20 points; a maximum of 10 points was allocated to forward flexion and 5 points each were allocated to external and internal rotation. Muscle power was evaluated using two components: peak strength and endurance. Strength was measured in 90° of forward flexion in the scapular plane using a manual muscle test. Interpretations of strength were made using comparisons with contralateral limbs. Shoulder endurance was tested by asking patients to hold a 2-kg dumbbell in 45° of forward flexion in the scapular plane, with the palm down, for as long as possible. This process was timed and holding this position for >10 s earned a maximum score. Satisfaction category scores were not included in the present study.

Surgical techniques

The same orthopedic surgeon (KE) with 20 years of experience in shoulder surgery performed all surgeries. Among the 54 patients, 37 patients underwent arthroscopic rotator cuff repair by suture-bridge technique and 17 patients by single-row technique. Decisions for the surgical technique were determined by the orthopedic surgeon’s preferences. There are ongoing debates regarding the ideal technique for rotator cuff repair (16,17). Single-row is the conventional technique and double-row is the most commonly used surgical technique currently which is thought to be biomechanically superior to a conventional repair (18,19). Suture-bridge or trans-osseous equivalent repair technique is a more recent type of double-row technique that some claimed that it is better for restoring footprint dimension and provides a stronger repair than by the double-row technique (20).

Postoperative evaluation

All 54 patients were examined by an orthopedic surgeon to determine the postoperative KSS. The mean interval between preoperative and postoperative KSS evaluation was 125.4 ± 62.2 days.

US and image analysis

All postoperative US were performed by one fellowship-trained musculoskeletal radiologist (PHJ) using a Logiq E9 imaging device (GE Medical Systems, Milwaukee, WI, USA) equipped with linear 6–15 MHz probes. The US images were interpreted by two fellowship-trained musculoskeletal radiologists independently. Interpreters 1 and 2 (PHJ and LSY) had 15 and 8 years of experience, respectively. The radiologists measured the thickness of the repaired supraspinatus tendons and fluid collection in the subdeltoid space independently on a picture archiving and communication system workstation (Infinitt, Seoul, Republic of Korea). The tendon thickness was measured on a longitudinal scan of the repaired supraspinatus tendon when the probe aligned parallel with the tendon fiber. Two lines were drawn perpendicular to the tendon fibers at 10 mm and 20 mm distal from the biceps tendon (Fig. 1). The mean values of anterior and posterior repaired supraspinatus tendon thickness were calculated. Subdeltoid fluid collection was measured also on a longitudinal scan of the supraspinatus tendon. Either between the deltoid and supraspinatus muscles or distally, between the deltoid muscle and the humeral shaft (Fig. 2); the measurement reflected the maximum thickness of the fluid layer if present, or 0 mm if the fluid layer was not present.

Statistical analysis

We assessed the relationship between the sonographic parameters, including repaired supraspinatus tendon thickness and subdeltoid fluid collection, with the clinical outcome represented by the KSS score using correlation coefficients (R). We calculated the R values using the non-parametric correlation analysis (Spearman’s correlation) with the difference of the KSS scores (postoperative KSS score – preoperative KSS score) for each category. A very high correlation was defined as R > 0.9, a relatively high correlation as R in the range of 0.7–0.9, a moderate correlation as R of 0.3–0.7, and a weak correlation as R of 0.1–0.3 (21). The intraclass correlation coefficient (ICC) was used in the inter-observer agreement analysis between the two radiologists. ICC values < 0.5 are indicative of poor reproducibility, ICC values of 0.5–0.75 indicate moderate reproducibility, ICC values of 0.75–0.9 indicate good reproducibility, and ICC values > 0.9 indicate excellent reproducibility (22). Statistical analyses were performed using PASW software version 18.0 (IBM Corp., Armonk, NY, USA) and P < 0.05 was considered statistically significant.

Results

The mean duration between surgery and postoperative US examination was 94.5 ± 16.0 days. The mean interval between preoperative and postoperative KSS evaluation was 125.4 ± 62.2 days. The mean thickness of repaired supraspinatus tendon and subdeltoid fluid collection were 6.1 ± 1.3 mm and 1.6 ± 2.0 mm, respectively. Among the 54 cases included this study, 17 (31%) cases underwent supraspinatus tendon repair by single-row technique and 37 (69%) cases by suture-bridge technique. Of the patients, 23 (43%) were aged <60 years and 31 (57%) were aged ≥60 years. The correlation between sonographic parameters and KSS score for each category is described in Table 1. There was a significant relationship between subdeltoid fluid collection and pain of the patients in both interpreters (P = 0.013 and P = 0.025, respectively). A significant relationship between subdeltoid fluid collection and function of the patients was observed with only interpreter 1 (P = 0.006) although every category of KSS showed a statistically insignificant inverse relationship with fluid thickness. However, there was no statistically significant correlation between the thickness of repaired supraspinatus tendon and KSS scores. In the single-row technique, a statistically significant inverse relationship between thickness of subdeltoid fluid collection and difference of the KSS scores in categories of function and pain was observed with only interpreter 1 (P = 0.029 and P = 0.04, respectively) (Table 2). In the suture-bridge technique, a statistically significant inverse relationship between thickness of subdeltoid fluid collection and difference in the value of the KSS scores in the muscle strength category was observed with interpreter 2 (P = 0.03). However, there was no statistically significant correlation between the thickness of repaired supraspinatus tendon and KSS scores in both surgical techniques. In patients aged <60 years, a statistically significant inverse relationship between thickness of subdeltoid fluid collection and difference in value of the KSS scores in the pain category was observed with interpreter 2 (P = 0.045) (Table 3). In patients aged ≥60 years, a statistically significant inverse relationship between thickness of subdeltoid fluid collection and difference in value of the KSS scores in the function category was observed with both interpreters (P = 0.015 and P = 0.04, respectively). However, a statistically significant inverse relationship between thickness of the repaired supraspinatus tendons and difference in value of the KSS scores in the ROM category was observed only with interpreter 1 (P = 0.043). In the age-adjusted study group, we found a significant inverse relationship between the subdeltoid fluid collection and pain scores in both interpreters (P = 0.023 and P = 0.019, respectively) (Table 4). Only interpreter 2 showed a significant inverse relationship between the subdeltoid fluid collection and function scores (P = 0.037). In addition, in the age-adjusted single-row technique group, interpreter 2 showed a significant inverse relationship between thickness of the repaired supraspinatus tendons and ROM scores (P = 0.045). However, there was no statistically significant correlation between the thickness of repaired supraspinatus tendon and KSS scores in the age-adjusted subgroup analysis (Table 4). The ICC values for sonographic imaging parameters between interpreters was in the range of 0.910–0.946, showing excellent reproducibility (Table 5).

Table 1.

Correlation coefficients of sonographic parameters with the difference value of KSS scores* for each category.

Sonographic parameters	Function		Pain		Range of motion		Muscle strength		Endurance
Sonographic parameters	Interpreter 1	Interpreter 2	Interpreter 1	Interpreter 2	Interpreter 1	Interpreter 2	Interpreter 1	Interpreter 2	Interpreter 1	Interpreter 2
Anterior thickness of repaired SST^†	–0.042	–0.039	–0.012	0.042	–0.188	–0.168	0.087	–0.017	–0.114	–0.225
P value	0.763	0.781	0.931	0.761	0.172	0.225	0.529	0.905	0.413	0.102
Posterior thickness of repaired SST^‡	–0.013	0.048	–0.047	0.139	–0.217	–0.139	–0.076	0.002	–0.123	–0.075
P value	0.925	0.729	0.736	0.322	0.116	0.317	0.587	0.987	0.375	0.591
Mean thickness of repaired SST^§	–0.052	0.035	–0.015	0.169	–0.219	–0.180	0.026	0.004	–0.123	–0.159
P value	0.706	0.801	0.914	0.221	0.111	0.194	0.849	0.975	0.376	0.251
Subdeltoid fluid collection	–0.371	–0.039	–0.336	–0.304	–0.196	–0.140	–0.248	–0.240	–0.162	–0.217
P value	0.006	0.781	0.013	0.025	0.156	0.312	0.070	0.081	0.241	0.115

*Difference in value of the KSS scores = postoperative KSS score – preoperative KSS score.

^†Anterior thickness of repaired SST at 10 mm distal from the biceps tendon.

^‡Posterior thickness of repaired SST = thickness of repaired SST at 20 mm distal from the biceps tendon.

^§Mean thickness = (anterior thickness + posterior thickness)/2

KSS, Korean Shoulder Scoring system; SST, supraspinatus tendon.

Table 2.

Correlation coefficients of sonographic parameters with the difference value of KSS scores* for each category for different operation techniques.

Surgical technique	Sonographic parameters	Function		Pain		Range of motion		Muscle strength		Endurance
Surgical technique	Sonographic parameters	Interpreter 1	Interpreter 2	Interpreter 1	Interpreter 2	Interpreter 1	Interpreter 2	Interpreter 1	Interpreter 2	Interpreter 1	Interpreter 2
Single row	Mean thickness of repaired SST^†	–0.305	–0.048	–0.142	0.181	–0.185	–0.189	–0.085	–0.214	–0.079	–0.250
	P value	0.234	0.855	0.587	0.487	0.476	0.468	0.746	0.410	0.762	0.333
	Subdeltoid fluid collection	–0.529	–0.444	–0.502	–0.383	–0.134	0.038	–0.127	–0.054	–0.198	–0.320
	P value	0.029	0.074	0.040	0.129	0.607	0.885	0.626	0.836	0.446	0.211
Suture bridge	Mean thickness of repaired SST^†	0.011	0.047	0.048	0.164	–0.231	–0.171	0.066	0.119	–0.145	–0.134
	P value	0.946	0.780	0.777	0.331	0.169	0.312	0.696	0.481	0.390	0.428
	Subdeltoid fluid collection	–0.283	–0.265	–0.304	–0.303	–0.161	–0.163	–0.320	–0.357	–0.167	–0.172
	P value	0.090	0.113	0.068	0.068	0.341	0.334	0.053	0.030	0.323	0.307

*Difference in value of the KSS scores = postoperative KSS score – preoperative KSS score.

†Mean thickness = (anterior thickness + posterior thickness)/2.

KSS = Korean Shoulder Scoring system, SST = supraspinatus tendon.

Table 3.

Correlation coefficients of sonographic parameters with the difference value of KSS scores* for each category for different age groups.

Age (years)	Sonographic parameters	Function		Pain		Range of motion		Muscle strength		Endurance
Age (years)	Sonographic parameters	Interpreter 1	Interpreter 2	Interpreter 1	Interpreter 2	Interpreter 1	Interpreter 2	Interpreter 1	Interpreter 2	Interpreter 1	Interpreter 2
<60	Mean thickness of repaired SST^†	–0.056	0.073	–0.013	0.151	–0.116	–0.203	0.129	0.063	–0.032	–0.123
	P value	0.800	0.742	0.953	0.491	0.598	0.354	0.557	0.774	0.883	0.577
	Subdeltoid fluid collection	–0.266	–0.296	–0.405	–0.422	–0.099	0.037	–0.154	–0.143	–0.135	–0.162
	P value	0.219	0.170	0.055	0.045	0.654	0.865	0.482	0.514	0.583	0.461
≥60	Mean thickness of repaired SST^†	–0.092	–0.077	–0.049	0.151	–0.366	–0.290	–0.069	–0.021	–0.146	–0.159
	P value	0.624	0.679	0.792	0.418	0.043	0.113	0.714	0.911	0.423	0.393
	Subdeltoid fluid collection	–0.432	–0.370	–0.248	–0.136	–0.239	–0.117	–0.282	–0.253	–0.245	–0.322
	P value	0.015	0.040	0.179	0.467	0.195	0.531	0.124	0.169	0.184	0.078

*Difference in value of the KSS scores = postoperative KSS score – preoperative KSS score.

^†Mean thickness = (anterior thickness + posterior thickness)/2.

KSS, Korean Shoulder Scoring system; SST, supraspinatus tendon.

Table 4.

Correlation coefficients of sonographic parameters with the difference value of KSS scores* for each category for different operation techniques (with control variable of age).

Sonographic parameters		Function		Pain		Range of motion		Muscle strength		Endurance
Sonographic parameters		Interpreter 1	Interpreter 2	Interpreter 1	Interpreter 2	Interpreter 1	Interpreter 2	Interpreter 1	Interpreter 2	Interpreter 1	Interpreter 2
Mean thickness of repaired SST^†		–0.067	0.009	0.015	0.141	–0.215	–0.217	0.016	0.027	–0.117	–0.135
P value		0.632	0.946	0.914	0.314	0.123	0.118	0.911	0.849	0.402	0.335
Subdeltoid fluid collection		–0.231	–0.287	–0.312	–0.322	–0.151	–0.082	–0.183	–0.193	–0.146	–0.211
P value		0.096	0.037	0.023	0.019	0.280	0.562	0.189	0.166	0.296	0.129
Single row	Mean thickness of repaired SST^†	–0.302	–0.028	–0.140	0.179	–0.382	–0.507	–0.083	–0.154	–0.055	–0.200
	P value	0.256	0.917	0.606	0.507	0.144	0.045	0.760	0.568	0.840	0.459
	Subdeltoid fluid collection	–0.418	–0.457	–0.486	–0.405	–0.094	0.106	–0.212	–0.090	–0.233	–0.410
	P value	0.107	0.075	0.056	0.120	0.729	0.697	0.431	0.740	0.386	0.114
Suture bridge	Mean thickness of repaired SST^†	–0.009	0.015	0.059	0.149	–0.175	–0.155	0.052	0.095	–0.137	–0.117
	P value	0.958	0.931	0.732	0.384	0.306	0.365	0.764	0.582	0.424	0.496
	Subdeltoid fluid collection	–0.176	–0.241	–0.263	–0.303	–0.164	–0.150	–0.185	–0.237	–0.122	–0.133
	P value	0.304	0.157	0.122	0.072	0.338	0.383	0.279	0.165	0.478	0.439

*Difference in value of the KSS scores = postoperative KSS score – preoperative KSS score.

^†Mean thickness = (anterior thickness + posterior thickness)/2.

KSS, Korean Shoulder Scoring system; SST, supraspinatus tendon.

Table 5.

Agreement between interpreters (ICC of sonographic parameters).

Sonographic parameters	ICC value	P value
Anterior thickness of repaired SST*	0.910 (0.844–0.948)	<0.001
Posterior thickness of repaired SST^†	0.912 (0.849–0.949)	<0.001
Mean thickness of repaired SST^‡	0.946 (0.905–0.969)	<0.001
Subdeltoid fluid collection	0.922 (0.860–0.956)	<0.001

Values are given as ICC (95% CI).

*Anterior thickness of repaired SST = thickness of repaired SST at 10 mm distal from the biceps tendon.

^†Posterior thickness of repaired SST = thickness of repaired SST at 20 mm distal from the biceps tendon.

^‡Mean thickness = (anterior thickness + posterior thickness)/2.

CI, confidence interval; ICC, intraclass correlation coefficient; SST, supraspinatus tendon.

Discussion

Persistent postoperative shoulder pain after rotator cuff repair has adverse effects for rehabilitation and consequently results in poor clinical outcomes (1,2). Furthermore, understanding the patient-specific factors that influence the subjective satisfaction is of interest in the current health care.

Although the primary etiology for the consideration of postoperative pain or disability is rotator cuff re-tear, subdeltoid fluid collection is frequently seen on postoperative imaging that may be a non-specific postoperative finding in a normal postoperative rotator cuff (14). Yoo et al. (6) found that 34% of patients had subacromial-subdeltoid fluid distension in the three-month postoperative period, although the study did not consider pain status. In the present study, we found that the amount of subdeltoid fluid collection after arthroscopic rotator cuff repair has a significant inverse correlation with the degree of shoulder pain relief after the surgery. The more fluid in the subdeltoid space on postoperative imaging, the higher the chance that the patient would experience persistent pain which has not been much relieved by the surgery. As the management of postoperative pain after rotator cuff repair can be challenging for both the clinician and the patient, treating the subdeltoid fluid collection could be one of the options in dealing with postoperative pain. In such cases, US is a good modality for treatment as US-guided injection or aspiration could be done in a one-stop process as well as a postoperative evaluation. In addition to the pain category, self-assessed score improvement of the function category also had a significant inverse relationship with the amount of subdeltoid fluid collection in some subgroup analyses, especially in patients aged ≥60 years. When there is a large amount of fluid in the subdeltoid space on postoperative US, patients tend to assess their ability to perform daily activities as not much improved after the surgery. In summary, the categories of function and pain, which indicate the subjective satisfaction and assessments, were significantly related to the amount of subdeltoid fluid collection that is frequently seen as a non-specific postoperative imaging finding on US or MRI. On the other hand, objectively measurable clinical outcomes had no significant correlation with the amount of subdeltoid fluid collection. As Yoo et al. (6) reported that postoperative subacromial‐subdeltoid bursitis decreased significantly over time, patients’ subjective postoperative complaints such as pain or disability to perform daily activities may also resolve as time goes by. We hypothesized that early postoperative repaired supraspinatus tendon thickness has a correlation with the patients’ clinical outcome as the repaired tendon thickness relates to degree of inflammation and edema. However, the thickness of the repaired supraspinatus tendon did not show a significant relationship with the clinical outcome in the present study, which was consistent with previous studies on postoperative US and MRI (7,8,23). Differences in supraspinatus tendon thickness may relate to numerous factors such as patients’ age and systemic diseases in addition to preoperative tendon thickness other than the degree of inflammation and edema (24 –26). The appearance of the repaired supraspinatus tendon after arthroscopic repair shows considerable variability in the early postoperative period and does not correlate to clinical outcome (23).

There are ongoing debates about the ideal technique for rotator cuff repair and the single-row and double-row techniques are the two main competitors. Although many studies reported that the double-row technique shows superior biomechanical results than the results by the single-row technique, several other studies reported that there were no significant differences between single-row repair and double-row repair with respect to clinical outcome (16,18,19). In agreement with the previous reports, we observed a statistically insignificant overall inverse relationship with the amount of subdeltoid fluid collection and the degree of clinical outcome improvement regardless of the surgical technique.

Incidence of rotator cuff tear increases with age; however, the effectiveness of repair surgery and the healing potential of repaired tendon in elderly patients remains controversial (27 –29). Elderly patients are more likely to have some factors that can have a negative influence on the healing process of the repaired tendon which may lead to poorer functional outcome (27 –29). We found that in patients aged ≥60 years, the amount of subdeltoid fluid collection showed a statistically significant inverse relationship with the degree of self-assessed function improvement in both interpreters. In elderly patients, the amount of subdeltoid fluid collection on postoperative US may have an uncertain relationship with the healing process of the repaired tendon and may have caused poor improvement of the subjectively assessed functional outcome. However, further study needs to be done to support this hypothesis.

From the viewpoint of accuracy and objectivity of sonographic findings, the agreement between interpreters for US parameter measurement of postoperative rotator cuff was almost perfect (Table 5). This means that standardization of sonographic postoperative rotator cuff measurement could be possible with excellent reproducibility.

The present study has several limitations. First, this was a retrospective study and it inherits all the limitations of retrospective investigations. For example, the measurement of sonographic parameters was based on captured images that had been taken before assessment, and therefore it was not a real-time measurement. Second, the small sample size was because there was a lack of full clinical information of KSS scores for many patients. Third, we did not evaluate the repaired tendon integrity which can contribute to clinical outcomes as well as preoperative factors such as extent of tear, involvement of other tendons beyond the supraspinatus, and findings suggesting subdeltoid bursitis. Other sonographic parameters such as the echogenicity of the repaired supraspinatus tendon or the stiffness measured by elastography could also be evaluated in future study. Fourth, the measurement of patient clinical outcome was based only on the KSS score, which is only used in the Republic of Korea and not worldwide. Fifth, the mean time interval between preoperative and postoperative KSS was in the range of 63–177 days. In general, the clinical outcome, especially pain, is relieved as time goes by, and thus the score could vary depending on the interval between preoperative and postoperative KSS. In addition, subdeltoid fluid collections tend to decrease with a longer follow-up. Moreover, there is a discrepancy between the time of postoperative KSS assessment and postoperative US. Finally, the factors that helped to determine the surgical technique by a surgeon have not been clarified, which could have led to some bias in the results.

In conclusion, persistent shoulder pain after rotator cuff repair in the early postoperative period has a significant correlation with the amount of subdeltoid fluid collection regardless of the surgical technique and patients’ age. The amount of subdeltoid fluid collection in elderly patients has an inverse relationship with the degree of self-assessed function improvement. However, the thickness of the repaired supraspinatus tendon has no significant correlation with the patients’ early postoperative clinical outcome. US evaluation of repaired rotator cuff at or near the third postoperative month is important and cautious interpretation is needed to assess the clinical outcome and may be limited to secondary pain and immobility.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Hee Jin Park

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