A low teres minor index of trophicity negatively impacts the functional outcomes of reverse shoulder arthroplasty

Influence of preoperative rotational shoulder stiffness on rate of motion restoration after anatomic and reverse total shoulder arthroplasty for glenohumeral osteoarthritis with an intact rotator cuff

BACKGROUND

A subset of patients undergoing anatomic and reverse total shoulder arthroplasty (aTSA and rTSA) lag behind their peers in regaining overhead range of motion (ROM) after surgery. The primary purpose of this study was to compare the rate of recovery of ROM after aTSA and rTSA performed in stiff (preoperative passive external rotation [ER] ≤0 °) versus non-stiff (preoperative passive ER >0°) shoulders with RCI-GHOA.

HYPOTHESIS

We hypothesized that preoperatively stiff shoulders (preoperative passive ER ≤0 °) would have slower recovery in ROM postoperatively with lower postoperative motion compared to non-stiff shoulders.

METHODS AND MATERIALS

A retrospective review of a multi-institution shoulder arthroplasty database was performed between 2001 and 2021. We identified 1,164 aTSAs and 539 rTSAs performed for RCI-GHOA with a minimum of 2-year clinical follow-up along with follow-up between 3-6 months and a third visit at any other time point. Primarily, the rate of recovery in ROM and time to maximum ROM was evaluated. Secondarily, we assessed six outcome scores and the influence of subscapularis repair during rTSA. Recovery in each outcome was modeled using continuous two-phase segmented linear regression models with random effects. Rate of recovery was defined as the slope of the first segment. Patients were considered to have recovered after surgery at the timepoint corresponding to the inflection point between piecewise segments.

RESULTS

Of the 1,164 aTSAs and 539 rTSAs included, 172 aTSAs (15%) and 80 rTSAs (15%) were stiff preoperatively, respectively. Compared to preoperatively stiff aTSAs, non-stiff aTSAs regained ER, abduction, internal rotation (IR), and forward elevation (FE) faster over a shorter duration. Similarly, non-stiff rTSAs regained ER, abduction, and FE faster and over a shorter duration compared to stiff rTSAs, but regained IR more slowly over a longer duration. Stiff rTSAs performed with subscapularis repair did not have any appreciable gain in ER after the immediate postoperative period. Although non-stiff and stiff rTSAs performed without subscapularis repair regained ER at a similar rate (4.4 vs. 4.2 °/month), stiff rTSAs continued to regain ER 1.9-times longer (11.9 vs. 6.4 months). When the subscapularis was repaired, non-stiff rTSAs regained abduction and IR faster over a short duration compared to stiff rTSAs.

CONCLUSIONS

Preoperative stiffness is associated with slower recovery of active ROM over a longer duration in patients undergoing shoulder arthroplasty for RCI-GHOA.

LEVEL OF EVIDENCE

III; Retrospective Cohort Comparison; Treatment Study.

How important is the teres minor in reverse total shoulder arthroplasty combined with latissimus dorsi transfer?

BACKGROUND

The utility of latissimus dorsi (LD) transfer combined with reverse total shoulder arthroplasty to restore external rotation (ER) strength is clinically well-established, but studies directly comparing LD and intact teres minor (TM) strength are lacking. Also, variations in eccentricity in the glenoid components have been under-estimated.

METHODS

We used 8 fresh-frozen cadaveric shoulders in this study. LD transfer to the posterolateral aspect of the greater tuberosity was simulated using a cable pulley system. We explored 6 possible conditions: massive rotator cuff tears (RCTs) (supraspinatus and infraspinatus tears), massive RCTs with TM tears, massive RCTs with TM tears and LD transfer, and all 3 conditions complicated by concentric and eccentric glenoid components. We measured the impingement-free range of motion, the ER torque (N∗m), the maximum abduction angle on successive loading of the middle deltoid (the abduction capacities), and the anterior dislocation forces.

RESULTS

Use of an eccentric glenosphere was associated with greater impingement-free range of motion in all directions, but the differences in ER strength, abduction capability, and anterior dislocation force compared with a concentric design were not significant. LD transfer with TM tears showed significantly greater ER strength than massive RCTs condition at 30° (P < .05) and 60° (P < .05) of abduction. TM tears, with or without LD transfer, had less anterior stability than an intact TM (P < .05). Massive RCTs combined with TM tears tended to be associated with an increased abduction angle under the same deltoid load across all tested loads, revealing the key role played by the TM in joint stability and ER.

CONCLUSIONS

LD transfer enhanced ER abduction strength in the absence of an intact TM, in contrast to a massive RCT with an intact TM. The TM was found to play a significant role in stability. Greater range of motion in all directions was achieved with an eccentric rather than with a concentric glenosphere.

Which muscle is the external rotation compensator after superior capsular reconstruction?

Background

Superior capsular reconstruction (SCR) is a surgical option for massive irreparable rotator cuff tears, particularly involving the supraspinatus and infraspinatus. In this procedure, the torn infraspinatus is not repaired or reconstructed. However, an improvement in postoperative external rotation (ER) angle and strength is observed. There is a lack of studies explaining how ER is restored after SCR. The aim of this study is to identify the ER compensator by assessing the muscle volume of the posterior deltoid and teres minor.

Methods

Sixty-eight patients with massive rotator cuff tears underwent SCR during 2016-2021. Of these patients, 28 who met the following inclusion criteria were retrospectively reviewed: (1) massive rotator cuff tears, including the supraspinatus and infraspinatus, (2) severe muscle atrophy and fatty change, (3) intact or reparable subscapularis tendon, and (4) Hamada of grade 3 or lower. Posterior deltoid and teres minor volume were measured using open-source medical image processing software preoperatively and 1-year postoperatively. The percentage of the posterior deltoid and teres minor muscle volume change was compared between patients with 1-year postoperative ER manual muscle testing (MMT) of grade 5 and of grade < 5. The relationship between grade of fatty change, percentage of the muscle volume change, and ER angle and strength were evaluated.

Results

There was a significant increase in the 1-year postoperative teres minor volume compared with the preoperative volume (24.6 ± 10.3 cm³ vs. 20.9 ± 8.3 cm³, P < .000), while the posterior deltoid volume remained unchanged (178.1 ± 48.3 cm³ vs. 178.8 ± 47 cm³). Patients with ER MMT of grade 5 had a greater teres minor volume change compared to those with an ER MMT grade of less than 5 (22.3% vs. 9.4%), although this difference was not significant (P = .074, 95% CI = -1.3 to 27.0). The posterior deltoid volume showed no significant change. The percentage of teres minor volume change had a weak positive correlation with ER strength (r = 0.308, P = .055, 95% CI = -0.02 to 1.0). There was a significant negative correlation between ER strength and the severity of both preoperative and postoperative fatty changes in the teres minor (r = -0.258, P = .065, 95% CI = -1.0 to -0.042 and r = -0.323, P = .028, 95% CI = -1.0 to -0.113, respectively). The pre and postoperative fatty changes in the teres minor were negatively correlated with the percentage of teres minor volume change (r = -0.298, P = .062, 95% CI = -1.0 to 0.031 and r = -0.413, P = .015, 95% CI = -1.0 to -0.1, respectively).

Conclusion

The teres minor may serve as a potential compensator for ER in patients with massive rotator cuff tears following SCR.

Intraoperative repair of functional subscapularis during RSA by deltopectoral approach could improve internal rotation but does not prevent anterior dislocation

INTRODUCTION

The role of the subscapularis following reverse shoulder arthroplasty (RSA) remains controversial as repair could restore adequate internal rotation and shoulder stability, but might compromise external rotation. The purpose of this multi-centre study, on a large cohort of RSAs performed using the deltopectoral approach, was to determine the effect of subscapularis preoperative status and intraoperative repair on range of motion, clinical scores and rates of complications at a minimum follow-up of 2 years.

HYPOTHESIS

Repair of a functional subscapularis grants better internal rotation and stability without compromising external rotation.

MATERIALS AND METHODS

We retrospectively reviewed records of all RSAs (n=916) performed by 14 surgeons that participated in a large national society symposium, and excluded 234 operated by the anterosuperior approach, 42 operated for rheumatoid arthritis, fractures, instability or post traumatic sequalae, and eight that had adjuvant latissimus dorsi tendon transfer (LDTT). This left 632 RSAs, in which the subscapularis was detached in 594, and repaired after detachment in 495. Patients completed pre- and postoperative Constant Score and postoperative Subjective Shoulder Value (SSV). Active forward elevation, active external rotation (ER), and active internal rotation (IR) were recorded pre- and postoperatively. Complications following RSA that required conservative treatment, reoperation without implant removal, as well as reoperation with implant removal were recorded.

RESULTS

Of the initial cohort of 632 shoulders, 120 (19%) were lost to follow-up, 12 (2%) died due to causes unrelated to RSA, and 26 (4%) were revised with implant removal. Of the remaining 474 shoulders, 259 (55%) had a functional repaired subscapularis (Group FR), 59 (12%) had a non-functional repaired subscapularis (Group nFR), whereas 68 (14%) had a not repaired subscapularis (Group nR). Comparison of patient demographics revealed no significant differences among the three groups. Postoperative Constant Score (p=0.031) and SSV (p=0.016) were significantly different among the three groups, but effect sizes were small and not clinically relevant. Differences in postoperative ER as well as postoperative IR were not significant among the three groups: 91 (35%) gained functional IR in Group FR, 11 (19%) in Group nFR, and 13 (19%) in Group nR. Three shoulders (1.2%) reported subjective instability and 1 (0.4%) dislocated in Group FR, but none in either Groups nFR or nR.

DISCUSSION

Despite statistically significant differences in Constant Score and SSV among the three groups, the clinical relevance of these differences is negligible, so repair of functional subscapularis has little or no influence on functional outcomes. During RSA by deltopectoral approach, repair of a functional subscapularis could slightly improve internal rotation in some patients but does not compromise external rotation, forward elevation or clinical scores, while repair of a non-functional subscapularis, compared to non-repair, did not improve range of motion or clinical scores.

LEVEL OF EVIDENCE

III; retrospective comparative.

Muscle activation patterns during active external rotation after reverse total shoulder arthroplasty: an electrophysiological study of the teres minor and associated musculature

BACKGROUND

Preoperative teres minor insufficiency has been identified as a risk factor for poor restoration of external rotation (ER) after reverse total shoulder arthroplasty (RTSA). However, there has been little investigation regarding muscle activation patterns generating ER. This prospective study sought to determine the timing and activation levels of the shoulder girdle musculature during ER in well-functioning RTSAs with an intact teres minor using a lateralized design.

METHODS

Patients who underwent RTSA ≥1 year previously with functional ER, an American Shoulder and Elbow Surgeons (ASES) score >70, superior rotator cuff deficiency, and an intact teres minor were identified. Electrophysiological and kinematic analyses were performed during ER in the modified neutral position (arm at side with 90° of elbow flexion) and in abduction (AB) (shoulder abducted 90° with 90° of elbow flexion). Dynamometer-recorded torque and position were pattern matched to electromyography during ER. The root-mean-square and integrated electromyography (in microvolts × milliseconds with standard deviation [SD]), as well as median frequency (MF) (in hertz with SD), were calculated to determine muscle recruitment. Pair-wise t test analysis compared muscle activation (P < .05 indicated significance).

RESULTS

After an a priori power analysis, 16 patients were recruited. The average ASES score, visual analog scale pain score, and ASES subscore for ER in AB ("comb hair") were 87.7, 0.5, and 2.75 of 3, respectively. In AB, muscle activation began with the upper trapezius, middle trapezius, and latissimus dorsi, followed by the anterior deltoid activating to neutral. With ER beyond neutral, the teres major (9.6 μV × ms; SD, 9.2 μV × ms) initiated ER, followed by the teres minor (14.1 μV × ms; SD, 18.2 μV × ms) and posterior deltoid (11.1 μV × ms; SD, 9.3 μV × ms). MF analysis indicated equal contributions of the teres major (1.1 Hz; SD, 0.5 Hz), teres minor (1.2 Hz; SD, 0.4 Hz), and posterior deltoid (1.1 Hz; SD, 0.4 Hz) in ER beyond neutral. In the modified neutral position, the upper trapezius and middle trapezius were not recruited to the same level as in AB. For ER beyond neutral, the teres major (9.5 μV × ms [SD, 9 μV × ms]; MF, 1.1 Hz [SD, 0.5 Hz]), teres minor (11.4 μV × ms [SD, 15.1 μV × ms]; MF, 1.1 Hz [SD, 0.5 Hz]), and posterior deltoid (8.5 μV × ms [SD, 8 μV × ms]; MF, 1.2 Hz [SD, 0.3 Hz]) were activated in similar sequence and intensity as AB. No differences in muscle activation duration or intensity were noted among the teres major, teres minor, and posterior deltoid (P > .05).

CONCLUSION

Active ER after RTSA is complex and is not governed by a single muscle-tendon unit. This study establishes a sequence, duration, and intensity of muscle activation for ER in well-functioning RTSAs. In both tested positions, the teres major, teres minor, and posterior deltoid function equally and sequentially to power ER.

Factors that affect external rotation following reverse shoulder arthroplasty: a retrospective multi-centre study on 501 shoulders

INTRODUCTION

The purpose of this multi-centre study was to assess external rotation in a large cohort following reverse shoulder arthroplasty (RSA) at a minimum follow-up of 2 years, and identify factors that influence postoperative and/or net-improvement of external rotation.

METHODS

The authors retrospectively reviewed records of 743 RSAs performed between January 2015 and August 2017 by 16 surgeons that participated in a large national society symposium; 193 (25.7%) were lost to follow-up, 16 (2.1%) died, and 33 (4.4%) were revised with implant exchange, which left 501 available for assessment at 2.0-5.5 years. Pre- and post-operative active forward elevation, active external rotation (ER1), active internal rotation (IR1) and constant score (CS) were collected. Regression analyses were performed to determine associations of patient demographics, surgical and implant parameters, rotator cuff muscles status and radiographic angles with ER1.

RESULTS

Multivariable analyses revealed postoperative ER1 decreased with age (β, - 0.35), increased with lateralisation shoulder angle (LSA) (β, 0.26), and was better in shoulders operated by the antero-superior (AS) approach (β, 11.41), but worse in shoulders with absent/atrophic teres minor muscles (β, - 10.06). Net-improvement of ER1 increased with LSA (β, 0.39), was better with inlay stems (β, 8.33) and BIO RSA (β, 6.22), but worse in shoulders operated for primary OA with rotator cuff (RC) tears (β, - 16.26), for secondary OA due to RC tears (β, - 16.06), or for mRCT (β, - 18.96).

CONCLUSIONS

This large multi-centre study revealed that, at a minimum of 2 years following RSA, ER1 improved by 16.1°. Postoperative ER1 was better in shoulders which had normal or hypertrophic teres minor muscles, were operated by the AS approach, or with greater LSA. Net-improvement of ER1 was better in shoulders with inlay stems, with BIO RSA, or with greater LSA, but worse in shoulders with rotator cuff deficiency.

LEVEL OF EVIDENCE

IV.

Assessment of intraoperative bleeding in reverse shoulder arthroplasty - with or without a stem

INTRODUCTION

The functional results of stemless reverse shoulder prostheses are similar to those with stems. However, the operative time and the bleeding appear less significant because of the absence of humeral reaming. To date, the data amongst the literature regarding this subject is limited. Thus, we report a retrospective evaluation on these 2 types of prostheses by assessing their respective intraoperative blood loss.

HYPOTHESIS

Reverse shoulder arthroplasty without a stem leads to less blood loss, compared to arthroplasty with a stem.

MATERIALS AND METHODS

Twenty-three patients underwent an operation for a stemless prosthesis, while 37 patients had a prosthesis with a stem. The hemoglobin was measured preoperatively, as well as postoperatively. Drainage of the operative site was maintained for two to three days. In the stem group, the preoperative hemoglobin was 14g/dL (11.7-16.6), while it was 13.1g/dL (11-15.8) in the stemless group.

RESULTS

The intraoperative bleeding reached 223cm³ (80-530), with an operative duration of 81minutes (40-110) in the stemless group, compared to 260cm³ (50-1000) and 92minutes (33-110) in the stem group. On the first day postoperatively, 333cm³ (20-570) of blood had been collected by drainage for the stemless group, compared to 279cm³ (40-550) in the stem group. The amount decreased the second day, with 139cm³ (20-510) and 129cm³ (0-750) respectively. There was no difference between the two groups regarding the postoperative hemoglobin level (11g/dL).

DISCUSSION

There is no significant difference concerning the blood loss between reverse shoulder replacements with and without stems.

LEVEL OF EVIDENCE

III Retrospective case control study.