Glenoid Region Research Articles

3D reconstruction of the scapula from biplanar X-rays for pose estimation and morphological analysis.

Patient-specific scapular shape in functional posture can be highly relevant to clinical research. Biplanar radiography is a relevant modality for that purpose with already two existing assessment methods. However, they are either time-consuming or lack accuracy. The aim of this study was to propose a new, more user-friendly and accurate method to determine scapular shape. The proposed method relied on simplified manual inputs and an upgraded version of the first 3D estimate based on statistical inferences and Moving-Least Square (MLS) deformation of a template. Then, manual adjustments, with real-time MLS algorithm and contour matching adjustments with an adapted minimal path method, were added to improve the match between the projected 3D model and the radiographic contours. The accuracy and reproducibility of the method were assessed (with 6 and 12 subjects, respectively). The shape accuracy was in average under 2mm (1.3mm in the glenoid region). The reproducibility study on the clinical parameters found intra-observer 95% confidence intervals under 3mm or 3° for all parameters, except for glenoid inclination and Critical Shoulder Angle, ranging between 3° and 6°. This method is a first step towards an accurate reconstruction of the scapula to assess clinical parameters in a functional posture. This can already be used in clinical research on non-pathologic bones to investigate the scapulothoracic joint in functional position.

Evolution of gliding in squirrel-related rodents (Mammalia: Sciuromorpha) did not induce a new optimum on the cortical thickness of the scapular glenoid fossa.

Many of the squirrel-related rodents (i.e., Sciuromorpha) are tree-dwelling species known to be very agile climbers. This taxon also includes the most diverse clade of gliding (aerial) mammals that likely descended from a non-gliding arboreal ancestor and evolved a patagium (i.e., a gliding membrane) to increase gliding performance. Glides can cover distances of up to 150 m and landing is typically accomplished by stalling the patagium to reduce impact velocity. It remains unclear if this behavior suffices to keep stresses on the locomotor apparatus similar to those experienced by their arboreal relatives or whether gliding behavior increases landing forces and stresses. The sparsely available support reaction force data are ambiguous, but bone microstructure is highly adaptable to changes in loading regime and likely provides insights into this question. Using μCT scans, we compared the cortical thickness of the glenoid fossa of the shoulder joint between arboreal and aerial Sciuromorpha using evolutionary model comparison, while also accounting for regional differences of the glenoid fossa. We did not find any differences between these locomotor behaviors, irrespective of the glenoid region. These findings agree with previous analyses of the microstructure of the femur in Sciuromorpha. We discuss different aspects that could explain the similarity in cortical thickness. According to our analysis of glenoid cortical thickness the loading regime appears not to have changed after the evolution of gliding locomotion, likely due to adjustments in landing performance.

The orbitotemporal region and the mandibular joint in the skull of shrews (Soricidae, Mammalia)

Modern phylogenetics place the Soricidae (shrews) into the order Lipotyphla, which belongs to the relatively new superorder clade Laurasiatheria. Their most derived skull feature is the unusual position and shape of the jaw articulation: Whereas in all other mammals the glenoid region of the squamosum is more or less tightly attached to the otic capsule or petrosal, respectively, in the soricids it is attached to the nasal capsule. This new position of the jaw articulation becomes possible by the posterior extension of the nasal capsule and the rostral shift of the glenoid fossa. By the study of dated postnatal ontogenetic stages of Crocidura russula and Sorex araneus, we show that the glenoid part of the squamosal becomes fixed to the nasal capsule by the ossified alae orbitalis and temporalis. The ala orbitalis is displaced laterally by the expanded cupula nasi posterior; this posterior expansion is well documented by the lamina terminalis, which incorporates parts of the palatinum and alisphenoid. Both alae consist largely of ‘Zuwachsknochen’ (‘appositional bone’) and are then named orbitosphenoid and alisphenoid. By the forward move of the pars glenoidea and of the alisphenoid, the foramen lacerum medium (‘fenestra piriformis’) also expands rostrally. Functionally, the forward shift of the jaw joint helps to keep the incisal biting force high. Biomechanically the jaws can be considered as a tweezer, and the rostral position of the jaw joints makes the interorbital pillar and the shell-like walls of the facial skull a lever for the highly specialized incisal dentition.

Clinical relevance of augmented statistical shape model of the scapula in the glenoid region

Objective: To illustrate (a) whether a statistical shape model (SSM) augmented with anatomical landmark set(s) performs better fitting and provides improved clinical relevance over non-augmented SSM and (b) which anatomical landmark set provides the best augmentation strategy for predicting the glenoid region of the scapula. Methods: Scapula SSM was built using 27 dry bone CT scans and augmented with three anatomical landmark sets (16 landmarks each) resulting in three augmented SSMs (aSSMproposed, aSSMset1, aSSMset2). The non-augmented and three augmented SSMs were then used in a non-rigid registration (regression) algorithm to fit to six external scapular shapes. The prediction error by each type of SSM was evaluated in the glenoid region for the goodness of fit (mean error, root mean square error, Hausdorff distance and Dice similarity coefficient) and for four anatomical angles (critical shoulder angle, lateral acromion angle, glenoid inclination, glenopoar angle). Results: Inter- and intra-observer reliability for landmark selection was moderate to excellent (ICC>0.74). Prediction error was significantly lower for SSMnon-augmented for mean (0.9 mm) and root mean square (1.15 mm) distances. Dice coefficient was significantly higher (0.78) for aSSMproposed compared to all other SSM types. Prediction error for anatomical angles was lowest using the aSSMproposed for critical shoulder angle (3.4°), glenoid inclination (2.6°), and lateral acromion angle (3.2°). Conclusion and Significance: The conventional SSM robustness criteria or better goodness of fit do not guarantee improved anatomical angle accuracy which may be crucial for certain clinical applications in pre-surgical planning. This study provides insights into how SSM augmented with region-specific anatomical landmarks can provide improved clinical relevance.

Statistical Shape Modeling Approach to Predict Missing Scapular Bone.

Prediction of complete and premorbid scapular anatomy is an important aspect of successful shoulder arthroplasty surgeries to treat glenohumeral arthritis and which remains elusive in the current literature. We proposed to build a statistical shape model (SSM) of the scapula and use it to build a framework to predict a complete scapular shape from virtually created scapular bone defects. The bone defects were synthetically created to imitate bone loss in the glenoid region and missing bony part in inferior and superior scapular regions. Sixty seven dry scapulae were used to build the SSM while ten external scapular shapes (not used in SSM building) were selected to map scapular shape variability using its anatomical classification. For each external scapula, four virtual bone defects were created in the superior, inferior and glenoid regions by manually removing a part of the original mesh. Using these defective shapes as prior knowledge, original shapes were reconstructed using scapula SSM and Gaussian process regression. Robustness of the scapula SSM was excellent (generality = 0.79mm, specificity = 1.74mm, first 15 principal modes of variations accounted for 95% variability). The validity and quality of the reconstruction of complete scapular bone were evaluated using two methods (1) mesh distances in terms of mean and RMS values and (2) four anatomical measures (three angles: glenoid version, glenoid inclination, and critical shoulder angle, and glenoid center location). The prediction error in the angle measures ranged from 1.0° to 2.2°. For mesh distances, highest mean and RMS error was 0.97mm and 1.30 respectively. DICE similarity coefficient between the original and predicted shapes was excellent (≥ 0.81). This framework provided high reconstruction accuracy and can be effectively embedded in the pre-surgical planning of shoulder arthroplasty or in morphology-based shoulder biomechanics modeling pipelines.

Computed Tomography Features of Glenoid Osteophytes in Traumatic Anterior Shoulder Instability: Comparison Between Younger and Older Patients.

Background:Osteoarthritis that develops after traumatic anterior shoulder instability is known as dislocation arthropathy, but its frequency and characteristics are still unclear.Purpose:To evaluate glenoid osteophytes in shoulders with traumatic anterior instability by using computed tomography (CT) and to elucidate the influence of instability on the progression of dislocation arthropathy in different age groups.Study Design:Cross-sectional study; Level of evidence, 3.Methods:This study involved 214 unoperated patients with unilateral instability who underwent CT of both shoulders. The patients were divided into 2 groups according to age at the time of CT: ≤30 years (younger group; n = 172) and ≥31 years (older group; n = 42). Patient demographics as well as the presence, size, and location of glenoid osteophytes were compared between the 2 groups and also between patients with and without osteophytes. Furthermore, patients with osteophytes in the older group were divided into 2 subgroups according to age at the time of the initial injury: as a teenager (early-onset subgroup; n = 9) or at ≥31 years (late-onset subgroup; n = 14), and the same assessments were conducted.Results:Osteophytes were significantly more frequent on the affected side of the older group compared with the younger group (71.4% vs 13.9%, respectively; P < .001). In the younger group, patients with osteophytes had more multiple-instability events (P = .002) and a longer interval from injury to CT (P < .001) than those without osteophytes. Although there was no difference in osteophyte size between the 2 groups, most osteophytes were located at the anteroinferior part of the glenoid in the younger group, while osteophytes were usually circumferential around the glenoid in the older group. A comparison between the early- and late-onset subgroups in older patients with osteophytes revealed that the osteophytes were more frequently located at the anteroinferior glenoid region in the early-onset subgroup.Conclusion:CT allowed a detailed evaluation of glenoid osteophytes, revealing that osteophytes were not uncommon in younger patients. Instability itself might influence the progression of osteoarthritic changes in younger patients, while aging seems to have a greater effect in older patients.

Ichthyosaurian palaeopathology: evidence of injury and disease in fossil ‘fish lizards’

AbstractThe documented record of ichthyosaurian paleopathologies reveals an array of injury‐related bone modifications and instances of disease evidenced through multiple clades, skeletal regions and body‐size classes from the Middle Triassic to middle Cretaceous. Examples include traumatic injuries, as well as a high incidence of articular diseases, including avascular necrosis. Forelimb pathologies are particularly abundant (65% of total reported), and the glenoid region seems to have been especially prone to articular disease. In contrast, pathologies affecting the vertebral column are comparatively underrepresented (6% of reported pathologies). Also notable is the disproportionate commonality of osteopathologies in ichthyosaurian taxa between 2 and 6 m in length (54%), as opposed to demonstrably larger (31%) or smaller bodied (15%) species. Furthermore, osteopathologies are almost exclusively described from skeletally mature individuals, and are best known from taxa of Jurassic age (78%), versus those from the Triassic (15%) or Cretaceous (7%); this likely reflects biases in the ichthyosaurian fossil record through time. Ichthyosaurs evince remarkable similarities in the types of observed skeletal damage relative to other ecologically similar marine amniotes – especially cetaceans and mosasaurid squamates, all of which potentially exhibited equivalent palaeoecological and/or behavioural adaptations for life in aqueous environments. Notably, however, the unusually low frequency of vertebral pathologies in ichthyosaurs is peculiar, and requires further investigation to establish significance.

Prediction of normal glenoid morphology with statistical shape modelling

Introduction Patients suffering from glenohumeral osteoarthritis may present an important wear of the glenoid articular surface leading to a new glenoid shape (Neoglenoid). The amount of wear to correct can thus be difficult to evaluate when a total shoulder arthroplasty is planned. Since the positioning of the glenoid component is known to be critical for the long-term success of the surgery, it would be helpful to have an estimate of the glenoid shape before it was deformed by osteoarthritis (paleoglenoid). The objective of this project was to evaluate the potential of statistical shape modeling to predict the shape of the articular glenoid surface from the remaining parts of the scapula, which have not been affected by the glenoid degenerative wear. Materials and methods To build a statistical shape model (SSM) of the scapula, CT scans of 64 scapulae without any sign of pathology were segmented to produce smooth three-dimensional surfaces of triangular meshes. The 64 meshes were then registered and combined into a SSM using the Statismo library. To evaluate the accuracy of the SSM prediction, we repeated the following six steps for each of the 64 scapulae. Step 1: one of the 64 scapulae is selected. Step 2: the SSM is built without this scapula (leave-one-out). Step 3: the glenoid region of the selected scapula is removed. Step 4: the SSM is fitted based on the remaining part of the scapula. Step 5: the SSM predicts the removed glenoid region. Step 6: the local accuracy of the SSM is evaluated by the distance between the predicted and existing glenoid surfaces. The orientations of the original and reconstructed glenoid were also assessed. Results When the SSM was based on the lateral scapula, the average accuracy reached 0.6 ± 0.1 mm. The accuracy of the glenoid orientation prediction was 2.9 ± 1.8 degrees. Discussion & conclusions The proposed method allowed to predict the shape of the glenoid surface, which was here artificially removed. This prediction could be obtained from the lateral part of the scapula, glenoid excluded, which is not affected by wear caused by osteoarthritis. The accuracy of the reconstruction was below 1 mm, and thus acceptable for the preoperative planning of total shoulder arthroplasty. This method should help to improve the positioning of glenoid implants for severe glenoid wear, and eventually reduce the failure risk after total shoulder arthroplasty.

The cranial base of Australopithecus afarensis : new insights from the female skull

Cranial base morphology differs among hominoids in ways that are usually attributed to some combination of an enlarged brain, retracted face and upright locomotion in humans. The human foramen magnum is anteriorly inclined and, with the occipital condyles, is forwardly located on a broad, short and flexed basicranium; the petrous elements are coronally rotated; the glenoid region is topographically complex; the nuchal lines are low; and the nuchal plane is horizontal. Australopithecus afarensis (3.7-3.0 Ma) is the earliest known species of the australopith grade in which the adult cranial base can be assessed comprehensively. This region of the adult skull was known from fragments in the 1970s, but renewed fieldwork beginning in the 1990s at the Hadar site, Ethiopia (3.4-3.0 Ma), recovered two nearly complete crania and major portions of a third, each associated with a mandible. These new specimens confirm that in small-brained, bipedal Australopithecus the foramen magnum and occipital condyles were anteriorly sited, as in humans, but without the foramen's forward inclination. In the large male A.L. 444-2 this is associated with a short basal axis, a bilateral expansion of the base, and an inferiorly rotated, flexed occipital squama--all derived characters shared by later australopiths and humans. However, in A.L. 822-1 (a female) a more primitive morphology is present: although the foramen and condyles reside anteriorly on a short base, the nuchal lines are very high, the nuchal plane is very steep, and the base is as relatively narrow centrally. A.L. 822-1 illuminates fragmentary specimens in the 1970s Hadar collection that hint at aspects of this primitive suite, suggesting that it is a common pattern in the A. afarensis hypodigm. We explore the implications of these specimens for sexual dimorphism and evolutionary scenarios of functional integration in the hominin cranial base.

Australopithecus afarensis and the Evolution of the Human Cranial Base

Differences in ape and human cranial base form are usually attributed to a combination of an enlarged brain, retracted face and upright locomotion in humans. Relative to the apes, the human foramen magnum is anteriorly inclined and, with the occipital condyles, is forwardly located on a broad, short and flexed base; the petrous bones are coronally rotated; the glenoid region is topographically complex; the nuchal lines low; and the nuchal plane horizontal. The proximate causes of these innovations are accessible through the fossil record, the only data source on the temporal pattern of trait evolution in the human lineage.Australopithecus afarensis (3.7‐3.0 Ma) is the earliest hominin species in which the cranial base can be assessed comprehensively. It shows that in small‐brained, bipedal hominins the foramen magnum and occipital condyles are anterior, as in humans, but without the foramen's forward inclination. In some skulls this is associated with a short, broad base and an inferiorly rotated occipital – novelties shared with later australopiths and humans. In others, including a recently recovered female, a more primitive morphology is present: while the foramen and condyles reside anteriorly on a short base, the nuchal lines are high, the nuchal plane is steep, and the base is relatively narrow.We explore implications for sexual dimorphism and functional integration in the hominin cranial base.

Zur Differenzialindikation anatomischer und inverser Schulterendoprothesen bei chronischer Polyarthritis

In addition to joint destruction, there is often also a loss of rotator cuff function in rheumatism patients. Thus, joint replacement alone using an anatomical prosthesis is unable to achieve satisfactory results. A half-linked inverse prosthesis, on the other hand, achieves improved function even in the presence of non-functioning rotator cuffs. Of 157 shoulder prostheses that were followed up, 21 had been implanted in patients with rheumatoid arthritis. An anatomical endoprosthesis was implanted in 15 cases and an inversed endoprosthesis in six cases (average age 55.5/66.6 years). The Constant score improved from 23 to 65 points for the anatomical prosthesis and from 15 to 67 points for the inversed endoprosthesis. An analogous improvement was also noted for mobility, strength and pain relief. The results of anatomical prostheses depend substantially on the extent of damage to the rotator cuff. Implantation of a semi-constrained inversed prosthesis provides a solution for severely damaged joints since it has a fixed centre of rotation. One prerequisite of success, however, is a sufficient bone stock in the glenoid region. The indication for bipolar prostheses, in contrast, is particularly strong when implantation of an inverse prosthesis is no longer possible.

Cyclic loading comparison of Bio-SutureTak-#2 FiberWire and Bio Mini-Revo-#2 Hi-Fi suture anchor-sutures in cadaveric scapulae

This study compared tap-in Bio-SutureTak suture anchor-#2 FiberWire suture (Group 1) and screw-in Bio Mini-Revo suture anchor-#2 Hi-Fi suture (Group 2) fixation in the glenoid region of interest for Bankart repair, in addition to evaluation of isolated suture loop biomechanical properties under progressive incremental cyclic loads. With knowledge of glenoid apparent bone mineral density (BMD), implant preparation and fit characteristics, and following application of a light manual tensile load, the primary investigator scored each specimen for perceived within group biomechanical test performance using a 0-10 point modified visual analog scale. After scoring, 12 paired constructs were placed in a servo hydraulic device clamp, preloaded to 25 N, and cycled between 25 and 50 Hz with a 25 N load increase every 25 cycles. Group 2 withstood greater load (104.1 +/- 56 vs. 70 +/- 36.9 N, P = 0.04) and displaced more at failure (13 +/- 4.5 vs. 8.6 +/- 3.3 mm, P = 0.04). All Group 1 specimens failed prior to reaching 150 N, whereas 25% of Group 2 specimens (n = 3) failed at 200 N. All specimens failed by anchor pullout except for three Group 2 specimens that failed by eyelet breakage at 200 N. Isolated suture testing revealed that Group 1 sutures displaced less at each cyclic load (P = 0.028) and withstood greater failure loads (P = 0.028) than that of Group 2 sutures. Group 2 constructs displayed moderately strong relationships between perceived within group biomechanical test performance and ultimate load (r (2) = 0.55) and displacement at failure (r (2) = 0.67). Group 1 did not display significant relationships. Similar biomechanical performance between 50 and 125 N, greater load at failure, and superior biomechanical test prediction accuracy suggest that the screw-in type Bio Mini-Revo suture anchor-#2 Hi-Fi suture combination may be preferred for Bankart lesion repair in low apparent BMD glenoid processes. The #2 Hi-Fi suture, however, allowed significantly greater displacement than the #2 FiberWire suture at each progressive cyclic load interval.

Homology of the reptilian coracoid and a reappraisal of the evolution and development of the amniote pectoral apparatus

As in monotreme mammals, the pectoral apparatus of basal (fossil) amniotes includes two coracoid elements, the procoracoid and metacoracoid. Among extant reptiles the metacoracoid has long been assumed lost; this notion is herein challenged. A comprehensive review of data from numerous sources, including the fossil record, experimental embryology, genetic manipulations and an analysis of morphology at the level cell condensations, supports the conclusion that the metacoracoid gives rise to the majority of the reptilian coracoid. By contrast, the reptilian procoracoid remains as a rudiment that is incorporated as a process of the (meta)coracoid and/or the glenoid region of the scapula early during development, prior to skeletogenesis. Application of this integrated approach corroborates and enhances previous work describing the evolution of the pectoral apparatus in mammals. A revised scenario of amniote coracoid evolution is presented emphasizing the importance of considering cell condensations when evaluating the homology of a skeletal complex.

The scapulocoracoid of the Queensland lungfish Neoceratodus forsteri (Dipnoi: Sarcopterygii): morphology, development and evolutionary implications for bony fishes (Osteichthyes)

Among bony fishes, the ontogenetic sequence by which the actinopterygian scapulocoracoid develops has been well described, but that of the sarcopterygian scapulocoracoid is poorly known, as the majority of taxa are only known from fossils. To rectify this, the cartilaginous scapulocoracoid of the extant lungfish Neoceratodus forsteri is examined. In initial stages of its development, the scapulocoracoid of Neoceratodus has a simple rounded shape, and supports the glenoid fossa. It appears nearly contemporaneously with the proximal endochondral element (humerus) of the pectoral fin. Pectoral fin elements develop by segmentation from a continuous field of cartilaginous precursor cells extending distally from the glenoid region of the scapulocoracoid. Subsequent scapulocoracoid development produces a ventromedial process, which is not associated with this field of precursor cells. A dorsal process also develops outside this field. Thus, the scapulocoracoid of Neoceratodus may consist of at least two developmentally distinct regions; (1) the ventromedial being homologous with the coracoid of actinopterygians, tetrapods and other jawed vertebrates and (2) a smaller dorsal process, homologous to the scapular region. The two, together with the glenoid region, give an overall triangular shape. The scapulocoracoids of fossil lungfish and other sarcopterygian fishes are also triangular and are composed of scapular and coracoid regions, rather than the ‘buttresses’ associated with scapulocoracoids of the Actinopterygii and Tetrapoda.

A finite element model of the shoulder: application to the comparison of normal and osteoarthritic joints

Objective. The objective of the present study was to develop a numerical model of the shoulder able to quantify the influence of the shape of the humeral head on the stress distribution in the scapula. The subsequent objective was to apply the model to the comparison of the biomechanics of a normal shoulder (free of pathologies) and an osteoarthritic shoulder presenting primary degenerative disease that changes its bone shape. Design. Since the stability of the glenohumeral joint is mainly provided by soft tissues, the model includes the major rotator cuff muscles in addition to the bones. Background. No existing numerical model of the shoulder is able to determine the modification of the stress distribution in the scapula due to a change of the shape of the humeral head or to a modification of the glenoid contact shape and orientation. Methods. The finite element method was used. The model includes the three-dimensional computed tomography-reconstructed bone geometry and three-dimensional rotator cuff muscles. Large sliding contacts between the reconstructed muscles and the bone surfaces, which provide the joint stability, were considered. A non-homogenous constitutive law was used for the bone as well as non-linear hyperelastic laws for the muscles and for the cartilage. Muscles were considered as passive structures. Internal and external rotations of the shoulders were achieved by a displacement of the muscle active during the specific rotation (subscapularis for internal and infrapinatus for external rotation). Results. The numerical model proposed is able to describe the biomechanics of the shoulder during rotations. The comparison of normal vs. osteoarthritic joints showed a posterior subluxation of the humeral head during external rotation for the osteoarthritic shoulder but no subluxation for the normal shoulder. This leads to important von Mises stress in the posterior part of the glenoid region of the pathologic shoulder while the stress distribution in the normal shoulder is fairly homogeneous. Conclusion. This study shows that the posterior subluxation observed in clinical situations for osteoarthritic shoulders may also be cause by the altered geometry of the pathological shoulder and not only by a rigidification of the subscapularis muscle as often postulated. This result is only possible with a model including the soft tissues provided stability of the shoulder. Relevance One possible cause of the glenoid loosening is the eccentric loading of the glenoid component due to the translation of the humeral head. The proposed model would be a useful tool for designing new shapes for a humeral head prosthesis that optimizes the glenoid loading, the bone stress around the implant, and the bone/implant micromotions in a way that limits the risks of loosening.

SHOULDER INJURY - FOOTBALL

HISTORY: An 18-year-old high school football player was involved in full speed hitting drills when he went shoulder to shoulder with his teammate, striking the superior aspect of his right shoulder against the superior aspect of his teammate's shoulder. The impact was such that both players came to a complete stop and both immediately complained of pain. The presenting player was unable to move his right shoulder in any direction without significant discomfort. He reported no numbness, tingling, or swelling. He had no prior history of shoulder dislocations or injuries. He did not finish practice. Upon office presentation his main complaint was painful, limited motion of the right shoulder. He continued to be free of numbness and tingling. He had no neck pain. PHYSICAL EXAM: The patient's exam revealed no gross deformities. He displayed decreased range of motion of the right shoulder in all planes as well as pronounced pain with any movement. There was mild anterior joint tenderness and early echymotic changes but no swelling. There was pain with humeral palpation. Apprehension and AP glide tests were difficult to assess secondary to pain and limited motion. Sensation was intact. Refelexes were 2/4 and symmetrical. Cervical spine examination was within normal limits. DIFFERENTIAL DIAGNOSIS: Acromioclavicular separation Clavicular fracture Glenoid fracture Shoulder subluxation/dislocation TESTS AND RESULTS: 4 view radiographs: lucency through the glenoid region consistent with fracture MRI: nondisplaced glenoid fracture extending through fossa with apparent tear of articular cartilage FINAL WORKING DIAGNOSIS: Glenoid fracture TREATMENT AND OUTCOMES: Sling for immobilization Gentle home range of motion exercises Ice, NSAIDS Physical therapy initiated at 3 weeks post injury Restricted return to play at 4 weeks post injury Full return to play at 6 weeks post injury

Structural analysis of an offset-keel design glenoid component compared with a center-keel design

Many different designs of glenoid prostheses have been developed in an attempt to reduce the loosening rates and improve the prognosis of total shoulder arthroplasty. This study investigated a design in which the keel is positioned anterior to the central plane of the component, an offset-keel design. The primary purpose of anterior location of the keel is to avoid contact between the keel and the cortical bone surface. However, anterior placement of the keel also situates it more directly under the line of action of the contact force in abduction; this has the possible advantage of reducing the bending stress on the cement mantle. Our purpose was to establish whether an offset-keel design reduces the cement stresses below those obtained with conventional central-keel designs. A computed tomography-based finite element model of the glenoid region is used and dynamic loading for 0° to 180° in both flexion and abduction is simulated with the use of data from van der Helm (J Biomech 1994;27:527-50). Finite element analyses are carried out for both the normal and the rheumatoid arthritic case. For the rheumatoid arthritic joint, a Larsen grade IV type destruction is reproduced and proximal subluxed loads are applied, associated with a deficient rotator cuff for 0° to 180° in flexion and abduction. Results predict that the cement mantle in the offset-keel design is much less stressed compared with that in the center-keel design for the maximum glenohumeral joint load in abduction for both the normal and the rheumatoid arthritis case. In flexion the offset-keel design still has lower cement stresses even though the load is acting on the opposite side of the glenoid cup from the keel; one explanation for this is that insertion of the offset keel involves removal of the lower stiffness cancellous bone, leaving the glenoid component flanges to be supported by the stronger bone remaining in the glenoid cavity. From a biomechanical point of view, the advantages of an offset-keel design would appear to be considerable. (J Shoulder Elbow Surg 2001;10:568-79.)

The anterior band of the inferior glenohumeral ligament. Assessment of its permanent deformation and the anatomy of its glenoid attachment.

Surgical treatment for traumatic, anterior glenohumeral instability requires repair of the anterior band of the inferior glenohumeral ligament, usually at the site of glenoid insertion, often combined with capsuloligamentous plication. In this study, we determined the mechanical properties of this ligament and the precise anatomy of its insertion into the glenoid in fresh-frozen glenohumeral joints of cadavers. Strength was measured by tensile testing of the glenoid-soft-tissue-humerus (G-ST-H) complex. Two other specimens of the complex were frozen in the position of apprehension, serially sectioned perpendicular to the plane containing the anterior and posterior rims of the glenoid, and stained with Toluidine Blue. On tensile testing, eight G-ST-H complexes failed at the site of the glenoid insertion, representing a Bankart lesion, two at the insertion into the humerus, and two at the midsubstance. For those which failed at the glenoid attachment the mean yield load was 491.0 N and the mean ultimate load, 585.0 N. At the glenoid region, stress at yield was 7.8 +/- 1.3 MPa and stress at failure, 9.2 +/- 1.5 MPa. The permanent deformation, defined as the difference between yield and ultimate deformation, was only 2.3 +/- 0.8 mm. The strain at yield was 13.0 +/- 0.7% and at failure, 15.4 +/- 1.2%; therefore permanent strain was only 2.4 +/- 1.1%. Histological examination showed that there were two attachments of the anterior band of the inferior glenohumeral ligament at the site of the glenoid insertion. In one, poorly organised collagen fibres inserted into the labrum. In the other, dense collagen fibres were attached to the front of the neck of the glenoid.

The anterior band of the inferior glenohumeral ligament

Surgical treatment for traumatic, anterior glenohumeral instability requires repair of the anterior band of the inferior glenohumeral ligament, usually at the site of glenoid insertion, often combined with capsuloligamentous plication. In this study, we determined the mechanical properties of this ligament and the precise anatomy of its insertion into the glenoid in fresh-frozen glenohumeral joints of cadavers. Strength was measured by tensile testing of the glenoid-soft-tissue-humerus (G-ST-H) complex. Two other specimens of the complex were frozen in the position of apprehension, serially sectioned perpendicular to the plane containing the anterior and posterior rims of the glenoid, and stained with Toluidine Blue. On tensile testing, eight G-ST-H complexes failed at the site of the glenoid insertion, representing a Bankart lesion, two at the insertion into the humerus, and two at the midsubstance. For those which failed at the glenoid attachment the mean yield load was 491.0 N and the mean ultimate load, 585.0 N. At the glenoid region, stress at yield was 7.8 ± 1.3 MPa and stress at failure, 9.2 ± 1.5 MPa. The permanent deformation, defined as the difference between yield and ultimate deformation, was only 2.3 ± 0.8 mm. The strain at yield was 13.0 ± 0.7% and at failure, 15.4 ± 1.2%; therefore permanent strain was only 2.4 ± 1.1%. Histological examination showed that there were two attachments of the anterior band of the inferior glenohumeral ligament at the site of the glenoid insertion. In one, poorly organised collagen fibres inserted into the labrum. In the other, dense collagen fibres were attached to the front of the neck of the glenoid.

The mixed dentition and associated skull fragments of a juvenile fossil hominid from Sterkfontein, South Africa.

In April-May 1983, the late A.R. Hughes and his field team recovered more than 40 bone fragments and teeth from a single solution pocket of the Sterkfontein Formation. After preparation and reconstruction by JMC, it was recognised that these fragments represent a single juvenile individual (Stw 151), consisting of more than 40 cranial and dental parts, with mixed dentition. It constitutes the most complete set of jaws and teeth of an early hominid child since the Taung child was recovered in 1924. In this paper, the morphological and metrical features of the individual teeth are described. The other associated skull fragments (right ramus of the mandible, left petrous bone, right glenoid region) are also described. Comparisons are made with other South (and East) African fossil hominids. The beautiful preservation simultaneously of most of the deciduous teeth and of the permanent teeth exposed in their crypts allows an accurate analysis of the developmental sequence. A report on the dental developmental status of this juvenile is presented. On the basis of the microanatomical study of the developing permanent teeth, the estimated age at death is 5.2-5.3 years. Reconstructions of the maxillary and mandibular arcades are also offered. The morphological and metrical features of Stw 151 raise the possibility that it may represent a hominid more derived towards an early Homo condition than the rest of the A. africanus sample from Member 4.