Sub-acute and chronic MRI findings in bilateral canine fibrotic contracture of the infraspinatus muscle

Fibrotic Contracture of the Infraspinatus Muscle with or without Contracture of the Teres Minor Muscle: A Retrospective Study in Eight Dogs

(1) Background: Fibrotic contracture of the canine infraspinatus muscle (FCIM) is considered an uncommon musculotendinous condition mainly affecting hunting dogs. After an acute onset of a painful non-weight-bearing lameness over a period of one to four weeks, a characteristic circumducted gait is developed in the affected thoracic limb. (2) Methods: Eight client-owned dogs of varying breeds, both sexes, aged 4-9 years old, and weighing 14-26 kg participated in the study. The duration of lameness prior to their first consultation ranged from 10 to 450 days. All participants were thoroughly examined clinically, orthopedically, and radiographically. (3) Results: The dogs underwent infraspinatus tenotomy, resulting in improved limb function. In three cases, a teres minor muscle contracture was revealed intraoperatively and resolved via a tenotomy at its insertion. The findings showed that 15 days post-operation, all dogs returned to full activity. The results obtained confirm and reinforce the literature data around FCIM and describe the first recorded condition of the simultaneous contracture of the infraspinatus and teres minor muscles. (4) Conclusions: In every case of shoulder lameness, contractures of all shoulder muscles should be included in the differential diagnosis and patients should be assessed for concurrent contractures even if infraspinatus contracture is identified.

Diagnosis of suprascapular nerve entrapment syndrome based on the infraspinatus muscle cross-sectional area on shoulder MRI

Suprascapular nerve entrapment (SNE) syndrome is a commonly overlooked cause of shoulder weakness and pain. It frequently causes weakness over the posterior and lateral and posterior aspects of the shoulder, as well as pain of infraspinatus muscles. Therefore, we considered that the infraspinatus muscle cross-sectional area (IMCSA) might be a new morphological parameter to analyze SNE syndrome. We assumed that the IMCSA is an important morphologic parameter in SNE syndrome diagnosis. We acquired infraspinatus muscle data from 10 patients with SNE syndrome and from 10 healthy subjects who had undergone magnetic resonance imaging of the shoulder and who revealed no evidence of SNE syndrome. We analyzed the infraspinatus muscle thickness (IMT) and IMCSA at the shoulder on the imaging of the shoulder using our image analysis program. The IMCSA was measured as the whole infraspinatus muscle cross-sectional area that was most atrophied in the sagittal S-MR images. The IMT was measured as the thickest level of infraspinatus muscle. The mean IMT was 29.17 ± 2.81 mm in the healthy subjects and 25.22 ± 3.19 mm in the SNE syndrome group. The mean IMCSA was 1321.95 ± 175.91 mm2 in the healthy group and 1048.38 ± 259.94 mm2 in the SNE syndrome group. SNE syndrome patients had significantly lower IMT (P < .001) and IMCSA (P < .001) than the healthy group. The ROC curve shows that the optimal cutoff point of the IMT was 26.74 mm, with 70.0% sensitivity, 70.0% specificity, and an AUC of 0.83 (95% CI, 0.65-1.00). The best cutoff value of the IMCSA was 1151.02 mm2, with 80.0% sensitivity, 80.0% specificity, and AUC of 0.87 (95% CI, 0.69-1.00). The IMT and IMCSA were both significantly associated with SNE syndrome. And the IMCSA was a highly sensitive diagnostic tool.

The Shoulder Joint and Common Abnormalities

The shoulder is a complex joint composed mostly of static and dynamic capsuloligamentous structures and plays an important role in forelimb lameness. Its complex anatomy and biomechanics necessitate thorough examination and diagnostic work-up for accurate diagnosis. This article provides an updated review of common canine shoulder pathologies, including osteochondrosis, bicipital and supraspinatus tendinopathies, infraspinatus contracture, medial shoulder syndrome, and luxation.

Advanced Imaging of the Forelimb: Use of Musculoskeletal Ultrasound and MRI of the Shoulder and Brachial Plexus

Advanced imaging (ultrasound, computed tomography, MRI) is a key component in defining and localizing the underlying cause of forelimb lameness. Given the propensity of soft tissue injury/disease of the shoulder and brachial plexus, ultrasound and MRI are of particular utility in defining tendinous, muscular, and nerve lesions. An advanced knowledge of shoulder and brachial plexus anatomy is necessary for both image acquisition and interpretation. To determine clinical significance, interpretation of both normal anatomy and suspected pathology must be correlated with clinical signs and orthopedic examination findings.

CT findings in a dog with subacute myopathy and later fibrotic contracture of the infraspinatus muscle

A 5-year-old Norwegian elkhound was referred due to an acute onset of lameness and persistent shoulder pain over a period of 3 weeks. Computed tomography demonstrated an enlarged, hypoattenuating right infraspinatus muscle with peripheral contrast enhancement and a nonenhancing center, without concurrent lesions in superficial structures or bones. The right infraspinatus muscle showed progressive atrophy on consecutive CT studies. The dog developed clinical symptoms compatible with fibrotic infraspinatus contracture 2 months after the initial presentation, and was treated with infraspinatus tenotomy. Histopathological diagnoses based on intraoperative biopsy samples were fibrotic muscle atrophy and muscle hypertrophy with regeneration.