The lever arm ratio of the rotator cuff to deltoid muscle explains and predicts pseudoparalysis of the shoulder

Greater tuberosity medial malposition: does it affect shoulder abductor moment?

PURPOSE

The detrimental effect of greater tuberosity malposition on functional scores is well known. Superior or posterior malpositions exceeding five mm lead to excessive loading on the deltoid strength. However, the significance of situations where greater tuberosity becomes medialized due to the compressive effect of the locking plate fixation, especially in fractures with metaphyseal dead space, has not been emphasized. It is hypothesized that this condition may cause shortening of the rotator cuff moment arm and consequently impact functional scores.

METHODS

Between 2012 and 2018, 52 patients, aged 65,28 (ranging 40-85) proximal humerus fractures treated with locking plate fixation were included in the study. Cephalodiaphyseal angle, greater tuberosity displacement , patients reported outcome and Constant-Murley scores were evaluated.

RESULTS

The mean Constant Murley score was determined to be 78.76 (ranging from 38 to 100). According to the patients reported outcome 39 excellent , five good , two fair, six poor results were observed. Avascular necrosis with screw migration was detected in five cases, while one patient experienced implant insufficiency along with varus deformity. Greater tuberosity was found to be positioned between 6 mm posterior-superior and -13 mm medial. Significant medial malposition was observed in three patients, with -9, -12, and -13 mm of medialization, respectively. Cephalodiaphysial angle was determined as 139.30 degrees (ranging from 120 to 150 degrees) and showed weak correlation with the functional score. Greater tuberosity medialization also showed weak correlation with the Constant-Murley score. The values exhibiting deviation were associated with low patient-reported outcome results and functional scores. In the examination of greater tuberosity displacement values, it was observed that Neer type 3 and 4 fractures differed significantly from Neer type 2 fractures regarding to Kruskal-Wallis test.

CONCLUSIONS

Medial impaction of greater tuberosity may be the reason of decreased functional scores, similar to superior or posterior malposition. The medialization of greater tuberosity should be considered as a potential factor leading to the shortening of the rotator cuff's abductor moment.

Massive and Irreparable Rotator Cuff Tears: A Review of Current Definitions and Concepts

Background

While massive and irreparable rotator cuff tears (MIRCTs) have been abundantly studied, inconsistent definitions in the literature and theories about pain and dysfunction related to them can be difficult to navigate when considering an individual patient.

Purpose

To review the current literature for definitions and critical concepts that drive decision-making for MIRCTs.

Study Design

Narrative review.

Methods

A search of the PubMed database was performed to conduct a comprehensive literature review on MIRCTs. A total of 97 studies were included.

Results

Recent literature reflects added attention to clarifying the definitions of "massive, "irreparable," and "pseudoparalysis." In addition, numerous recent studies have added to the understanding of what generates pain and dysfunction from this condition and have reported on new techniques for addressing them.

Conclusion

The current literature provides a nuanced set of definitions and conceptual foundations on MIRCTs. These can be used to better define these complex conditions in patients when comparing current surgical techniques to address MIRCTs, as well as when interpreting the results of new techniques. While the number of effective treatment options has increased, high-quality and comparative evidence on treatments for MIRCTs is lacking.

Pseudoparalysis and Acromiohumeral Interval Reversibility Are the Most Important Factors Affecting the Achievement of Patient-Acceptable Symptom State After Arthroscopic-Assisted Latissimus Dorsi Tendon Transfer

PURPOSE

To determine the patient-acceptable symptom state (PASS) values for American Shoulder and Elbow Surgeons (ASES) score and the Constant-Murley (CM) score after arthroscopic-assisted latissimus dorsi tendon transfer (LDTT) and to identify potential factors affecting the achievement of PASS.

METHODS

Fifty consecutive patients who underwent arthroscopic-assisted LDTT between 2015 and 2020 were retrospectively analyzed. In total, 42 patients met the inclusion criteria with minimum follow-up of 1 year postoperative. Patients were evaluated preoperatively and 1-year postoperatively with multiple clinical measurements including ASES, CM, score and PASS. The primary outcome was identified as patient satisfaction which assessed with achievement of a PASS. Potential factors affecting the patient satisfaction including age, sex, body mass index, previous surgery, presence of pseudoparalysis, critical shoulder angle, shoulder abduction moment index, acromiohumeral interval (AHI) reversibility, Hamada grade and fatty infiltration were evaluated for their association with PASS value by stepwise logistic regression analysis.

RESULTS

A total of 42 patients were evaluated with mean follow-up 27.8 ± 8.21 months. The ASES and CM scores improved from preoperative means of 21.6 ± 6.5 and 25.2 ± 8.5 to 65.6 ± 20.7 points and 56.8 ± 16.5 points, respectively (P < .001). The PASS values for the ASES and CM scores were 62.4 and 52.5, respectively. The univariate analysis showed that older age (P = .021), presence of pseudoparalysis (P < .001), previous surgery (P = .016), lower preoperative AHI (P = .028), and lower AHI reversibility (P < .001) were all significantly associated with worse patient satisfaction. The multivariable logistic regression analysis showed that pseudoparalysis (P = .038) and AHI reversibility (P = .021) were independent prognostic factors affecting the achievement of a PASS after arthroscopic-assisted LDTT. The cutoff value for AHI reversibility to predict an achievement of PASS was found to be 4.0 mm.

CONCLUSIONS

Arthroscopic-assisted LDTT led to satisfactory results in patients with massive rotator cuff tears. However, pseudoparalysis and AHI reversibility were the most important independent prognostic factors that consistently reduced and increased, respectively, the odds of achieving a PASS.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Joint-line medialization after anatomical total shoulder replacement requires more rotator cuff activity to preserve joint stability

BACKGROUND

The biomechanical effects of joint-line medialization during shoulder surgery are poorly understood. It was therefore the purpose of this study to investigate whether medialization of the joint line especially associated with total shoulder arthroplasty leads to changes in the rotator cuff muscle forces required to stabilize the arm in space.

METHODS

A validated computational 3-D rigid body simulation model was used to calculate generated muscle forces, instability ratios, muscle-tendon lengths and moment arms during scapular plane elevation. Measurements took place with the anatomical and a 2 mm and 6 mm lateralized or medialized joint line.

RESULTS

When the joint line was medialized, increased deltoid muscle activity was recorded throughout glenohumeral joint elevation. The rotator cuff muscle forces increased with medialization of the joint line in the early phases of elevation. Lateralization of the joint line led to higher rotator cuff muscle forces after 52° of glenohumeral elevation and to higher absolute values in muscle activity. A maximum instability ratio of >0.6 was recorded with 6 mm of joint-line medialization.

CONCLUSION

In this biomechanical study, medialization and lateralization of the normal joint line during total shoulder arthroplasty led to substantial load changes on the shoulder muscles used for stabilizing the arm in space. Specifically, medialization does not only lead to muscular shortening but also to increased load on the supraspinatus tendon during early arm elevation, the position which is already most loaded in the native joint.

Three-dimensional kinematic features in large and massive rotator cuff tears with pseudoparesis

BACKGROUND

Although massive rotator cuff tears occasionally lead to severe impairment of shoulder function, the criteria for losing the ability to elevate the arm are unclear. This study aimed to analyze the features of both tear size and 3-dimensional (3D) shoulder kinematics that correspond to the loss of the ability to elevate the arm in patients with large and massive rotator cuff tears.

METHODS

We prospectively enrolled patients with rotator cuff tears, including the supraspinatus and more than half of the subscapularis or more than two-thirds of the infraspinatus, without severe pain. A total of 13 patients (15 shoulders) were divided into 2 groups: 9 shoulders in the pseudoparesis (P) group and 6 shoulders in the non-pseudoparesis (NP) group. Fluoroscopic images were collected during active scapular-plane elevation, and 3D shoulder kinematics was analyzed using 2-dimensional-3D registration techniques. The radiographic findings and 3D kinematic results were compared between the groups. The correlation between tear size and 3D kinematics was also investigated.

RESULTS

The most superior position of the humeral head center was significantly higher in the P group (6.7 ± 3.0 mm in P group vs. 3.6 ± 1.3 mm in NP group, P = .0321). Superior migration, which was defined as the most superior position > 5 mm, was significantly more frequent in the P group (7 shoulders and 1 shoulder in the P and NP groups, respectively; P = .0201). Thoracohumeral external rotation was significantly smaller in the P group (16° ± 31° in P group vs. 91° ± 21° in NP group, P < .0001). The total tear size and the tear sizes of the anterior and posterior rotator cuffs were significantly correlated with the superior (r = 0.68, P = .0056), anterior (r = 0.68, P = .0058), and posterior (r = -0.80, P = .0004) positions of the humeral head center. The tear size of the posterior rotator cuff also tended to be correlated with glenohumeral external rotation (r = -0.48, P = .0719).

CONCLUSION

Anterior and posterior rotator cuff tears cause significant superior and anteroposterior translations of the humeral head, and posterior cuff tears may lead to loss of glenohumeral external rotation. With these abnormal kinematics, superior migration and loss of thoracohumeral external rotation were identified as features of pseudoparesis.

Nanofiber Scaffolds by Electrospinning for Rotator Cuff Tissue Engineering

Rotator cuff tears continue to be at risk of retear or failure to heal after surgical repair, despite the use of various surgical techniques, which stimulate development of novel scaffolding strategies. They should be able to address the known causes of failure after the conventional rotator cuff repair: (1) failure to reproduce the normal tendon healing process, (2) resultant failure to reproduce four zones of the enthesis, and (3) failure to attain sufficient mechanical strength after repair. Nanofiber scaffolds are suited for this application because they can be engineered to mimic the ultrastructure and properties of the native rotator cuff tendon. Among various methods for tissue-engineered nanofibers, electrospinning has recently been highlighted in the rotator cuff field. Electrospinning can create fibrous and porous structures that resemble natural tendon's extracellular matrix. Other advantages include the ability to create relatively large surface-to-volume ratios, the ability to control fiber size from the micro to the nano scale, and the flexibility of material choices. In this review, we will discuss the anatomical and mechanical features of the rotator cuff tendon, their potential impacts on improper healing after repair, and the current knowledge of the use of electrospinning for rotator cuff tissue engineering.

Shoulder biomechanics in normal and selected pathological conditions

The stability of the glenohumeral joint depends on soft tissue stabilizers, bone morphology and dynamic stabilizers such as the rotator cuff and long head of the biceps tendon. Shoulder stabilization techniques include anatomic procedures such as repair of the labrum or restoration of bone loss, but also non-anatomic options such as remplissage or tendon transfers.

Rotator cuff repair should restore the cuff anatomy, reattach the rotator cable and respect the coracoacromial arch whenever possible. Tendon transfer, superior capsular reconstruction or balloon implantation have been proposed for irreparable lesions.

Shoulder rehabilitation should focus on restoring balanced glenohumeral and scapular force couples in order to avoid an upward migration of the humeral head and secondary cuff impingement. The primary goal of cuff repair is to be as anatomic as possible and to create a biomechanically favourable environment for tendon healing.

Cite this article: EFORT Open Rev 2020;5:508-518. DOI: 10.1302/2058-5241.5.200006