Defining the shape of the scapulothoracic gliding surface.

PURPOSE: The aim of the study is to evaluate the difference in shape of the upper part and lower part of the Scapulothoracic Gliding Surface (STGS). METHODS: 3D-CT images of the thoracic cage of 50 patients were created in MIMICS ®. Three anatomical landmarks (insertion m. serratus anterior on 5th rib; transverse process of 2th and 7th vertebra) were used as an anteroposterior cutting plane to define the STGS. The upper part of the STG was defined as rib 2-5 and the lower part as 5-8. Next, in MATLAB ®, a script was used to create the sphere with best fit for upper and lower parts of STGS. The Root-Square-Mean Error (RSME) (mm) between two closest points on the fitted sphere and the STGS of both parts were calculated to determine the goodness-of-fit. RESULTS: The RSME was found to be significantly lower for the area ribs 2-5 (mean 7.85 mm, SD 1.86) compared the area of ribs 5-8 (mean 10.08 mm, SD 1.90). CONCLUSION: The STGS of the upper thoracic wall (2-5) is more spherical shaped than the STGS of the lower thoracic wall (rib 5-8).

Morphologic variations of the scapula in 3-dimensions: a statistical shape model approach.

BACKGROUND: Morphologic variations of the scapula and acromion have been found to be associated with shoulder pathology. This study used statistical shape modelling to quantify these variations in healthy shoulders. MATERIALS AND METHODS: A statistical shape model of the scapula was created using 3-dimensional computed tomography reconstructions of 108 survey-confirmed nonpathologic shoulders of 54 patients. The mean shape and the 95% confidence interval were calculated and analyzed in the first 5 shape modes. RESULTS: The first 5 shape modes consisted of consecutively sized (72% of total variation), rotation of the coracoacromial complex (5%), acromial shape and slope (4%), shape of the scapular spine (2%), and acromial overhang (2%). DISCUSSION AND CONCLUSION: In healthy shoulders, a certain variation in rotation of the coracoacromial complex and in acromial shape and slope was observed. These new parameters might be correlated with shoulder pathology such as glenohumeral osteoarthritis or rotator cuff tears.

Revision of reversed shoulder arthroplasty: Is a reoperation possible?

INTRODUCTION: As the number of reversed shoulder arthroplasty (RSA) procedures increases, the revision rate will also increase. In case of severe bone insufficiency, instability or infection of the primary RSA, revision to another RSA is preferable but not always possible. Hemiarthroplasty (HA), spacers and resection arthroplasty (RA) have been described in this indication. MATERIALS AND METHODS: Between 2004 and 2016, 20 shoulders in 19 patients were treated at Ghent University Hospital for failed revision of RSA. Nine received a megahead prosthesis, a spacer was implanted in 6, and 5 underwent RA. RESULTS: Indications for implantation of a megahead prosthesis were loosening RSA (n = 5), infection (n = 4), dislocation (n = 1) and nerve irritation (n = 1). Improvement of range of motion was observed. Anterosuperior migration of the prosthesis was noted in 2 patients. Another 2 patients were ultimately revised to RSA. Seven permanent spacers were implanted for infection, of which 2 remain in place till today. The other 5 were revised to RSA. Of the 5 patients treated with RA, 3 were revised further on to RSA, resulting in pain relief and regain of function. DISCUSSION: Our study shows that a megahead prosthesis has better functional results than RA, but is inferior to RSA. Due to increasing surgical experience and improving technique, 9 patients could ultimately be reconverted to another RSA. A review of current literature is presented. In HA and RA, the functional results are poor, and pain relief is uncertain. Results of spacers are variable and can be satisfactory. Arthrodesis is a last resort. CONCLUSION: In our case series study, a hemiarthroplasty can be performed in case of failure of RSA. However, the results are inferior to another RSA.