During shoulder arthroplasty the native functionality of the diseased shoulder joint is restored, this functionality is strongly dependent upon the native anatomy of the pre-diseased shoulder joint. Therefore, surgeons often use the healthy contralateral scapula to plan the surgery, however in bilateral diseases such as osteoarthritis this is not always feasible. Virtual reconstructions are then used to reconstruct the pre-diseased anatomy and plan surgery or subject-specific implants. In this project, we develop and validate a statistical shape modeling method to reconstruct the pre-diseased anatomy of eroded scapulae with the aim to investigate the existence of predisposing anatomy for certain shoulder conditions. The training dataset for the statistical shape model consisted of 110 CT images from patients without observable scapulae pathologies as judged by an experienced shoulder surgeon. 3D scapulae models were constructed from the segmented images. An open-source non-rigid B-spline-based registration algorithm was used to obtain point-to-point correspondences between the models. The statistical shape model was then constructed from the dataset using principle component analysis. The cross-validation was performed similarly to the procedure described by Plessers et al. Virtual defects were created on each of the training set models, which closely resemble the morphology of glenoid defects according to the Wallace classification method. The statistical shape model was reconstructed using the leave-one-out method, so the corresponding training set model is no longer incorporated in the shape model. Scapula reconstruction was performed using a Monte Carlo Markov chain algorithm, random walk proposals included both shape and pose parameters, the closest fitting proposal was selected for the virtual reconstruction. Automatic 3D measurements were performed on both the training and reconstructed 3D models, including glenoid version, critical shoulder angle, glenoid offset and glenoid center position. The root-mean-square error between the measurements of the training data and reconstructed models was calculated for the different severities of glenoid defects. For the least severe defect, the mean error on the inclination, version and critical shoulder angle (°) was 2.22 (± 1.60 SD), 2.59 (± 1.86 SD) and 1.92 (± 1.44 SD) respectively. The reconstructed models predicted the native glenoid offset and centre position (mm) an accuracy of 0.87 (± 0.96 SD) and 0.88 (± 0.57 SD) respectively. The overall reconstruction error was 0.71 mm for the reconstructed part. For larger defects each error measurement increased significantly. A virtual reconstruction methodology was developed which can predict glenoid parameters with high accuracy. This tool will be used in the planning of shoulder surgeries and investigation of predisposing
Objectives. To date, no study has considered the impact of acromial morphology on shoulder range of movement (ROM). The purpose of our study was to evaluate the effects of lateralization of the centre of rotation (COR) and neck-shaft angle (NSA) on shoulder ROM after reverse shoulder arthroplasty (RSA) in patients with different
Introduction. Reverse Shoulder Arthroplasty (RSA) is recognized to be an effective solution for rotator cuff deficient arthritic shoulders, but there are still concerns about impingement and range of motion (ROM). Several RSA biomechanical studies have shown that humeral lateralization can increase ROM in planar motions (e.g. abduction). However, there is still a debate whether humeral lateralization should be achieved with a larger sphere diameter or by lateralizing the center of rotation (COR). The latter has shown to decrease the deltoid moment arm and increase shear forces, where the former may pose challenges in implanting the device in small patients. The aim of this study was to evaluate how humeral lateralization achieved by varying COR lateral offset and glenosphere diameter in a reverse implant can affect impingement during activities of daily living (ADLs). Methods. Nine shoulder CT scans were obtained from healthy subjects. A reverse SMR implant (LimaCorporate, IT) was virtually implanted on the glenoid and humerus (neck-shaft angle 150°) as per surgical technique using Mimics software (Materialise NV). Implant positioning was assessed and approved by a senior surgeon. The 3D models were imported into a validated shoulder computational model (Newcastle Shoulder Model) to study the effects of humeral lateralization. The main design parameters considered were glenosphere diameter (concentric Ø36mm, Ø40mm, Ø44mm) and COR offset (standard, +2mm, +5mm), for a total of 9 combinations for each subject; −10°, 0° and 10° humeral components versions were analyzed. The model calculated the percentage of impingement (intra-articular, contact of cup with scapula neck and glenoid border; extra-articular, contact of humerus with acromion and coracoid) during 5 ADLs (hand to opposite shoulder, hand to back of head, hand to mouth, drink from mug and place object to head height). Results. On average, the Ø40mm and Ø44mm glenosphere resulted in significantly less impingement across ADLs compared to Ø36mm (−31% and −35% respectively). Humeral version and lateralization had no significant effect on impingement for the Ø44mm glenosphere. However, lateralization of +5 mm substantially reduced impingement on the Ø36mm glenosphere but the effect was significant only for the neutral 0° version (−42%) and 10° (−50%) anteversion. Discussion and Conclusions. The results of this study suggest that, for the SMR Reverse prosthesis, humeral lateralization through the increase of glenosphere diameter was the most efficient way to reduce impingement during ADLs compared to the lateralization of the COR. Humeral version can also affect the impact of lateralization on impingement during ADLs; in this study, the impingement for the Ø36mm glenosphere with 10° retroversion was not decreased through lateralization; this may be related to the combined effect of version and
The three-dimensional (3D) correction of glenoid
erosion is critical to the long-term success of total shoulder replacement
(TSR). In order to characterise the 3D morphology of eroded glenoid
surfaces, we looked for a set of morphological parameters useful
for TSR planning. We defined a scapular coordinates system based
on non-eroded bony landmarks. The maximum glenoid version was measured
and specified in 3D by its orientation angle. Medialisation was
considered relative to the spino-glenoid notch. We analysed regular
CT scans of 19 normal (N) and 86 osteoarthritic (OA) scapulae. When
the maximum version of OA shoulders was higher than 10°, the orientation
was not only posterior, but extended in postero-superior (35%),
postero-inferior (6%) and anterior sectors (4%). The medialisation
of the glenoid was higher in OA than normal shoulders. The orientation
angle of maximum version appeared as a critical parameter to specify
the glenoid shape in 3D. It will be very useful in planning the
best position for the glenoid in TSR. Cite this article:
Background. There has been increased focus on understanding the risk factors associated with scapular notching in reverse shoulder arthroplasty (RSA). The purpose of this study is to evaluate the effect of
This study provides recommendations on the position
of the implant in reverse shoulder replacement in order to minimise
scapular notching and osteophyte formation. Radiographs from 151
patients who underwent primary reverse shoulder replacement with
a single prosthesis were analysed at a mean follow-up of 28.3 months
(24 to 44) for notching, osteophytes, the position of the glenoid
baseplate, the overhang of the glenosphere, and the prosthesis scapular
neck angle (PSNA). A total of 20 patients (13.2%) had a notch (16 Grade 1 and four
Grade 2) and 47 (31.1%) had an osteophyte. In patients without either
notching or an osteophyte the baseplate was found to be positioned
lower on the glenoid, with greater overhang of the glenosphere and
a lower PSNA than those with notching and an osteophyte. Female patients
had a higher rate of notching than males (13.3% Based on these findings we make recommendations on the placement
of the implant in both male and female patients to avoid notching
and osteophyte formation. Cite this article:
Introduction: Classical studies have defined axes from prominent scapular landmarks that have been used to synthesise many applications. The morphology of the scapula is however known to be highly variable between individuals. 1. ,. 2. ,. 3. This introduces significant variability on the use of these classical axes for various clinical applications. Also, some of the literatureapplied landmarks were highly dependant on the presence of pathology, thus introducing more variability in the products they parented. This limits accuracy in inter-subject comparisons from such applications. Therefore there is a need to identify and define pathology-insensitive anatomical landmarks that are less variable between individuals than the variability of the overall scapular shape. The aim of this study was to define more scapular axes from clearly identifiable landmarks, analysing these and other classical definitions for the best axis that minimizes variability and is closely related to the scapular clinical frame of reference. Materials and Method: Fourteen different axes of new and classical definitions from clearly identifiable landmarks were quantified by applying medical images of 21 scapulae. The orientations of the quantified axes were calculated. The plane of the blade of the scapula was defined, bounded by the angulus inferior. 4. , the spine/medial border intersection. 5. and the most inferolateral point of the infra-glenoid tubercle. This was applied to grade the alienation of the quantified axes from the scapular blade. The angular relationships between individual axes of a spcapula were quantified, averaged over the 21 specimens and their standard deviations (SD) applied to grade the sensitivity of each axis to interscapular variations in the others. The volume of data required to define an axis (VDA) was noted for its dependency on pathology. These three criteria were weighted according to relative importance such that. axes bearing 10° or more from the blade deviated significantly and were eliminated;. insensitivity to
