Dissectional Orientation: Morphological Variations of Teres Minor Muscle and its Nerve Supply

SUMMARY: The teres minor is one of the rotator cuff muscles that comprise the superior margin of the quadrangular space. Quadrangular space syndrome (QSS) refers to the entrapment or compression of the axillary nerve and the posterior humeral circumflex artery in the quadrangular space, often caused by injuries, dislocation of the shoulder joint, etc. Patients who fail the primary conservative treatments and have persistent symptoms and no pain relief for at least six months would be considered for surgical interventions for QSS. This cadaveric study of 17 cadavers (males: 9 and females: 8) was conducted in the Gross Anatomy Laboratory at the Department of Anatomy, Faculty of Medicine Siriraj Hospital, Mahidol University. The cadavers were preserved in a 10 % formaldehyde solution and obtained ethical approval by the ethical commission of the Siriraj Institutional Review Board. The morphology of the teres minor muscle-tendon junction, the bifurcation type of the axillary nerve, and the length and number of the terminal branches of the nerve to the teres minor were documented. Specimens with quadrangular space contents and surrounding muscles that had been destroyed were excluded from the study. The results showed that 47.06 % of the specimens had type A bifurcation, 47.06 % had type B bifurcation, and the remaining 5.88 % had type C bifurcation. It was observed that 58.82 % had nonclassic muscle-tendon morphology, while 41.18 % were classic. The average length of the terminal branches of the nerve to the teres minor in males was 1.13 cm, with the majority having two branches. For females, many showed one terminal branch with an average length of 0.97 cm. Understanding the differences in anatomical variations can allow for a personalized treatment plan prior to quadrangular space syndrome surgical procedures and improve the recovery of postsurgical interventions for patients.

El músculo redondo menor es uno de los músculos del manguito rotador que comprende el margen superior del espacio cuadrangular. El síndrome del espacio cuadrangular (QSS) se refiere al atrapamiento o compresión del nervio axilar y la arteria circunfleja humeral posterior en el espacio cuadrangular, a menudo causado por lesiones, dislocación de la articulación humeral, entre otros. En los pacientes en los que fracasan los tratamientos conservadores primarios y presentan síntomas persistentes y ningún alivio del dolor durante al menos seis meses se considerarían para intervenciones quirúrgicas para QSS. Este estudio cadavérico de 17 cadáveres (hombres: 9 y mujeres: 8) se llevó a cabo en el Laboratorio de Anatomía Macroscópica del Departamento de Anatomía de la Facultad de Medicina del Hospital Siriraj de la Universidad Mahidol. Los cadáveres se conservaron en una solución de formaldehído al 10 % y obtuvieron la aprobación ética de la comisión ética de la Junta de Revisión Institucional de Siriraj. Se documentó la morfología de la unión músculo-tendón del músculo redondo menor, el tipo de bifurcación del nervio axilar y la longitud y el número de las ramas terminales del nervio para el músculo redondo menor. Se excluyeron del estudio los especímenes con contenido de espacios cuadrangulares y músculos circundantes que habían sido destruidos. Los resultados mostraron que el 47,06 % de los especímenes presentó bifurcación tipo A, el 47,06 % una bifurcación tipo B y el 5,88 % restante una bifurcación tipo C. Se observó que el 58,82 % presentaba una morfología músculo-tendinosa no clásica, mientras que el 41,18 % era clásica. La longitud pmedia de los ramos terminales del nervio hasta el músculo redondo menor en los hombres era de 1,13 cm, y la mayoría tenía dos ramos. En el caso de las mujeres, mostraron un ramo terminal con una longitud promedio de 0,97 cm. Comprender las diferencias en las variaciones anatómicas puede permitir un plan de tratamiento personalizado antes de los procedimientos quirúrgicos del síndrome del espacio cuadrangular y mejorar la recupe- ración de las intervenciones posquirúrgicas de los pacientes.

Role of Magnetic Resonance Imaging in rotator cuff pathologies

Background: Stability to the shoulder joint which has great range of motility, is provided by the rotator cuff, the coraco-acromial arch and the glenoid labrum along with the capsule and glenohumeral ligaments. The common disorders involving the rotator cuff tendons include impingement, tendinopathies and tears. Magnetic Resonance Imaging (MRI) has good spatial resolution for identifying tendon edema and tears in the rotator cuff. Aim and objectives: To describe the MRI characteristics of rotator cuff pathologies. To describe the rotator cuff pathologies in terms of age, gender, symptomatology and predisposing factors among the study population. Materials and methods: The study was performed in the Department of Radiodiagnosis, NRI General Hospital, Chinakakani, Guntur from September 2015 to August 2017 and comprises of 100 patients with suspected rotator cuff pathologies who were referred for MRI shoulder. Results: The age distribution of patients with rotator cuff abnormalities was in the range of 21 and 74 years. The most commonly affected was supraspinatus tendon followed by subscapularis and infraspinatus tendons. Among the rotator cuff abnormalities the frequently encountered finding was tendinosis followed by partial tears. Conclusion: Magnetic Resonance Imaging is very useful in depicting rotator cuff disease in patients with painful, weak or stiff shoulder for prompt and accurate diagnosis.

Teres minor innervation and injection site / Inervación y sitio de inyección del músculo redondo menor

The aim of this study was to elucidate the injection point on the teres minor (TM) for effective injection. Thirty-two specimens from 16 adult Korean cadavers (10 males and 6 females, age ranging from 42 to 102 years) were used in the study. The reference line between the inferior point on the inferior angle of the scapula (IA) and the most prominent point on the acromial angle of the scapula (AA) on the surface were identified. The measurements expressed the two above-mentioned parameters as X and Y coordinates in relation to the reference line. The X coordinate was located at 128.1±10.4 mm (78.1±5.7 %) and the Y coordinate was located at 25.3±7.6 mm (15.5±4.8 %). The recommended site according to this can be used for injections in patients with TM stiffness.

El objetivo fue determinar el punto de inyección en el músculo redondo menor (MRM) para llevar a cabo una correcta inyección. Se utilizaron 32 muestras correspondientes a 16 cadáveres adultos coreanos (10 hombres y 6 mujeres, entre 42 a 102 años de edad). Se identificó en la superficie la línea de referencia entre el punto inferior en el ángulo inferior de la escápula (AI) y el punto más prominente en el ángulo acromial de la escápula (AA). Las mediciones expresaron los dos parámetros mencionados anteriormente como coordenadas X e Y en relación con la línea de referencia. La coordenada X se encuentra a 128,1±10,4 mm (78,1±5,7 %) y la coordenada Y estaba situada a 25,3±7,6 mm (15,5±4,8 %). El sitio recomendado de acuerdo a estos resultados se puede usar para preparaciones inyectables en pacientes con rigidez del MRM.

Effect of Preoperative Fatty Degeneration of the Deltoid and the Teres Minor Muscles on the Clinical Outcome after Reverse Total Shoulder Arthroplasty

BACKGROUND: To evaluate the effect of preoperative fatty degeneration of deltoid and teres minor muscles on the clinical outcome in patient with reverse total shoulder arthroplasty (RTSA). METHODS: Nineteen patients with RTSA were enrolled. The mean follow-up period was 16.1 months. The fatty degeneration of three distinct parts in each deltoid and the teres minor muscle was measured using a preoperative magnetic resonance imaging. Postoperatively, the muscle strengths for forward elevation (FE), abduction (Abd), and external rotation (ER) were measured using a myometer at the last follow-up. The parameters for clinical outcome were Constant Score (CS) and Korean Shoulder Score (KSS). RESULTS: The number of cases was 10 in group 1 and 9 in group 2. The strength of FE and Abd were significantly higher in group 1 (p<0.001 and p<0.001, respectively), and the strength of ER was not different significantly between two groups (p=0.065). For the clinical outcome, both CS and KSS were higher in group 1 (p=0.002 and p=0.002, respectively). The number of patients in group A was 11, and group B was 8. Although there was not a significant difference in terms of FE and Abd between group A and B (p=0.091, p=0.238), ER was significantly higher in group A (p=0.012). We did not find a significant difference in the clinical scores (CS, p=0.177 and KSS, p=0.238). CONCLUSIONS: These findings suggest the importance of a preoperative evaluation of the fatty degeneration of deltoid and teres minor muscles for predicting postoperative strength and clinical outcome.

Arthroscopic Treatment of Isolated Teres Minor Tendon Tear: A Case Report

Arthroscopic repair of an isolated teres minor tendon tear without associated shoulder joint pathology has not been reported in the literature. We report on a case of isolated teres minor tendon tear after trauma. The patient complained of severe shoulder pain and progressive limited range of motion 4 months after the injury. Magnetic resonance imaging showed a full-thickness tear of the teres minor tendon at its musculotendinous junction and arthroscopic repair was performed. At 2 years follow-up, satisfactory clinical and radiological outcomes were observed with return to pre-injury level. Here, the authors report this case and provide a review of literature.

Effect of Preoperative Fatty Degeneration of the Deltoid and the Teres Minor Muscles on the Clinical Outcome after Reverse Total Shoulder Arthroplasty

BACKGROUND: To evaluate the effect of preoperative fatty degeneration of deltoid and teres minor muscles on the clinical outcome in patient with reverse total shoulder arthroplasty (RTSA). METHODS: Nineteen patients with RTSA were enrolled. The mean follow-up period was 16.1 months. The fatty degeneration of three distinct parts in each deltoid and the teres minor muscle was measured using a preoperative magnetic resonance imaging. Postoperatively, the muscle strengths for forward elevation (FE), abduction (Abd), and external rotation (ER) were measured using a myometer at the last follow-up. The parameters for clinical outcome were Constant Score (CS) and Korean Shoulder Score (KSS). RESULTS: The number of cases was 10 in group 1 and 9 in group 2. The strength of FE and Abd were significantly higher in group 1 (p<0.001 and p<0.001, respectively), and the strength of ER was not different significantly between two groups (p=0.065). For the clinical outcome, both CS and KSS were higher in group 1 (p=0.002 and p=0.002, respectively). The number of patients in group A was 11, and group B was 8. Although there was not a significant difference in terms of FE and Abd between group A and B (p=0.091, p=0.238), ER was significantly higher in group A (p=0.012). We did not find a significant difference in the clinical scores (CS, p=0.177 and KSS, p=0.238). CONCLUSIONS: These findings suggest the importance of a preoperative evaluation of the fatty degeneration of deltoid and teres minor muscles for predicting postoperative strength and clinical outcome.

Arthroscopic Treatment of Isolated Teres Minor Tendon Tear: A Case Report

Arthroscopic repair of an isolated teres minor tendon tear without associated shoulder joint pathology has not been reported in the literature. We report on a case of isolated teres minor tendon tear after trauma. The patient complained of severe shoulder pain and progressive limited range of motion 4 months after the injury. Magnetic resonance imaging showed a full-thickness tear of the teres minor tendon at its musculotendinous junction and arthroscopic repair was performed. At 2 years follow-up, satisfactory clinical and radiological outcomes were observed with return to pre-injury level. Here, the authors report this case and provide a review of literature.

Isolated Injury of the Axillary Nerve Branch to Teres Minor Muscle Following After Traumatic Posterior Instability of Shoulder

We describe a case of a 23-year-old man who presented with posterior instability of the right shoulder following trauma. Focal neuropathy of the axillary nerve branch to the teres minor muscle was diagnosed electrophysiologically. A shoulder magnetic resonance image revealed fatty atrophy of the teres minor muscle with sparing of the deltoid, supraspinatus, infraspinatus, and subscapularis muscles. To our knowledge, this is the first case of selective injury of the branch of the axillary nerve to the teres minor muscle to be described in Korea.

Branching pattern and morphometry of the axillary nerve / 대한해부학회지

The branches of the axillary nerve and branching pattern of the posterior cord of the brachial plexus are not fully described in the anatomy textbooks. The branching pattern of the axillary nerve is needed to understand various symptoms of quadrilateral space syndrome. We studied on the branching patterns and variation of the axillary nerve and posterior cord of brachial plexus in 127 adult cadaver arms. The axillary, radial and thoracodorsal nerves arising from the posterior cord of the brachial plexus were classified into 4 types according to the position of the thoracodorsal nerve. The most common type (42.5%) was that the three nerves directly arising from the posterior cord. The thoracodorsal nerve branched from the axillary nerve in 27.6%. The posterior branches of the axillary nerve were divided into 6 types by the arising point of the nerve to teres minor muscle. The deltoid branch and lateral superior brachial cutaneous nerve were divided after branching of nerve to teres minor muscle in 50.8%. The lower subscapular nerve was branched from the axillary nerve in 70.9%. We measured the distances from the branching point of the axillary nerve to the inferior border of the subscapularis in the quadriangular space and from the coracoid process to the axillary nerve. The length and motor point of the teres minor muscle were measured. The relationship of the axillary nerve and posterior circumflex humeral artery was observed. The axillary nerve was always medial to the artery and their superoinferior relationship was variable. The clinical significance of the branching pattern of the axillary nerve was discussed.