Dynamic Three-Dimensional Shoulder Mri during Active Motion for Investigation of Rotator Cuff Diseases.

BACKGROUND: MRI is the standard methodology in diagnosis of rotator cuff diseases. However, many patients continue to have pain despite treatment, and MRI of a static unloaded shoulder seems insufficient for best diagnosis and treatment. This study evaluated if Dynamic MRI provides novel kinematic data that can be used to improve the understanding, diagnosis and best treatment of rotator cuff diseases. METHODS: Dynamic MRI provided real-time 3D image series and was used to measure changes in the width of subacromial space, superior-inferior translation and anterior-posterior translation of the humeral head relative to the glenoid during active abduction. These measures were investigated for consistency with the rotator cuff diseases classifications from standard MRI. RESULTS: The study included: 4 shoulders with massive rotator cuff tears, 5 shoulders with an isolated full-thickness supraspinatus tear, 5 shoulders with tendinopathy and 6 normal shoulders. A change in the width of subacromial space greater than 4mm differentiated between rotator cuff diseases with tendon tears (massive cuff tears and supraspinatus tear) and without tears (tendinopathy) (p = 0.012). The range of the superior-inferior translation was higher in the massive cuff tears group (6.4mm) than in normals (3.4mm) (p = 0.02). The range of the anterior-posterior translation was higher in the massive cuff tears (9.2 mm) and supraspinatus tear (9.3 mm) shoulders compared to normals (3.5mm) and tendinopathy (4.8mm) shoulders (p = 0.05). CONCLUSION: The Dynamic MRI enabled a novel measure; 'Looseness', i.e. the translation of the humeral head on the glenoid during an abduction cycle. Looseness was better able at differentiating different forms of rotator cuff disease than a simple static measure of relative glenohumeral position.The authors received no specific funding for this work

Development and ex-vivo assessment of a novel patient specific guide and instrumentation system for minimally invasive total shoulder arthroplasty.

ObjectiveTo develop and assess a novel guidance technique and instrumentation system for minimally invasive short-stemmed total shoulder arthroplasty that will help to reduce the complications associated with traditional open replacement such as poor muscle healing and neurovascular injury. We have answered key questions about the developed system including (1) can novel patient-specific guides be accurately registered and used within a minimally invasive environment?; (2) can accuracy similar to traditional techniques be achieved?MethodsA novel intra-articular patient-specific guide was developed for use with a new minimally invasive posterior surgical approach that guides bone preparation without requiring muscle resection or joint dislocation. Additionally, a novel set of instruments were developed to enable bone preparation within the minimally invasive environment. The full procedure was evaluated in six cadaveric shoulders, using digitizations to assess accuracy of each step.ResultsPatient-specific guide registration accuracy in 3D translation was 2.2±1.2mm (RMSE±1 SD; p = 0.007) for the humeral component and 2.7±0.7mm (pConclusionThis system achieves minimally invasive shoulder replacement with accuracy similar to traditional open techniques while avoiding common causes of complications.SignificanceThis novel technique could lead to a paradigm shift in shoulder arthroplasty for patients with moderate arthritis, which could significantly improve rehabilitation and functional outcomes

Description of clinical evaluation of patients and healthy volunteers.

<p>Description of clinical evaluation of patients and healthy volunteers.</p

Monitoring of the humeral head center projection on to the glenoid for each of the 14 shoulders during abduction.

<p>The size of the glenoids was standardized so that each fit with a circle of 200% diameter (-100% to +100%). The locations of the humeral head center projections on to the glenoid are expressed in percentile. Fig 4A, massive rotator cuff tear; Fig 4B, <i>Supraspinatus</i> tear; Fig 4C, Tendinopathy alone; Fig 4D, normal shoulders.</p

The width of the subacromial space during abduction motion.

<p>The width of the subacromial space during abduction motion.</p

Translation of the humeral head along the Y-axis (superior-inferior direction) of glenoid coordinate system

<p>Translation of the humeral head along the Y-axis (superior-inferior direction) of glenoid coordinate system</p

Mean of kinematic measures for each rotator cuff disease group

<p>Mean of kinematic measures for each rotator cuff disease group</p

Assessment of rotator cuff.

<p>Assessment of rotator cuff.</p

Translation of the humeral head along the X-axis (anterior-posterior direction) of glenoid coordinate system

<p>Translation of the humeral head along the X-axis (anterior-posterior direction) of glenoid coordinate system</p