Biomechanical consequences of humeral component malpositioning after anatomical total shoulder arthroplasty (original) (raw)
Related papers
Total shoulder arthroplasty -- current problems and possible solutions
Journal of Orthopaedic Science, 1999
The concept and design of a cemented unconstrained total shoulder arthroplasty (TSA), introduced by Charles Neer II 25 years ago, has been successful in the management of degenerative and inflammatory conditions of the shoulder, controlling pain and, in many patients, significantly improving function. The clinical outcome is very much determined by the nature and severity of the pathology, as well as by the surgeon's experience and ability to correctly locate and fix the components. Total shoulder arthroplasty is a technically difficult procedure with perhaps a greater potential for technical errors and complications compared with other commonly performed arthroplasties. Current systems are modular on the humeral side, with varying head diameters and neck lengths, allowing more accurate coverage of the cut surface of the humeral neck and improved ability to establish the position of the joint line within the requirements of correct soft tissue tension and balance. Cemented all-polyethylene glenoid components remain the most favored, but the majority now have an increased radius of curvature compared with their corresponding humeral head, to allow translation during movement. Aseptic glenoid component loosening is the most frequently encountered long-term complication and is hastened by conforming prostheses, incorrect positioning, rotator cuff tears, and capsular contractures, but is protected by secure glenoid fixation. Cemented one-piece metal-backed glenoids have been disappointing, but non-cemented glenoids are being trialed with promising early results, although they have introduced their own particular problems of rapid polyethylene wear and component dissociation. Although cemented humeral components have a very low incidence of symptomatic loosening, most surgeons currently use press-fit designs supplemented with metaphyseal porous coating for osseous integration. Based on increased understanding of the morphology of the upper humerus, current designs are evolving with increased modularity, allowing the surgeon to choose the appropriate size, inclination, offset and version of the humeral component. These changes will, it is hoped, result in improved functional recovery and increased survivorship of the glenoid component.
Prosthetic positioning in total shoulder arthroplasty
Journal of Shoulder and Elbow Surgery, 2005
Accurate positioning of the prosthetic humeral head is necessary to reproduce normal glenohumeral kinematics and to avoid damage to the rotator cuff and impingement on the glenoid component or coracoacromial arch. Proper positioning of the head requires accurate placement of the stem and prosthetic designs that allow the head position to adapt to the variations in both normal and pathologic humeral anatomy. Glenoid malpositioning can lead to both humeral instability and increased stress of the glenoid component that may lead to premature glenoid loosening. This review summarizes the cadaveric and finite-element model that defines the abnormalities associated with humeral and glenoid component malpositioning. (J Shoulder Elbow Surg 2005;14:111S-121S.)
Glenohumeral kinematics following total shoulder arthroplasty: a finite element investigation
Journal of …, 2007
The osseous geometry of the glenohumeral joint is naturally nonconforming and minimally constrained, and the joint's stability is maintained by action of the rotator cuff muscles. Damage to these muscles is often associated with joint degeneration, and a variety of glenoid prostheses have been developed to impart varying degrees of stability postoperatively. The issues of conformity and constraint within the artificial shoulder have been addressed through in vivo and in vitro studies, although few computational models have been presented. The current investigation presents the results of three-dimensional finite element analyses of the total shoulder joint and the effects of design parameters upon glenohumeral interaction. Conformity was shown not to influence the loads required to destabilize the joint, although it was the principal factor determining the magnitude of humeral head translation. Constraint was found to correlate linearly with the forces required to dislocate the humeral head, with higher constraint leading to slightly greater humeral migration at the point of joint instability. The model predicts that patients with a dysfunctional supraspinatus would experience frequent eccentric loading of the glenoid, especially in the superior direction, which would likely lead to increased fixation stresses, and hence, a greater chance of loosening. For candidates with an intact rotator cuff, the models developed in this study predict that angular constraints of at least 148 and 6.58 in the superoinferior and anteroposterior axes are required to provide stable unloaded abduction of the humerus, with larger constraints of 188 and 108 necessitated by a dysfunctional supraspinatus. The tools developed during this study can be used to determine the capacity for different implant designs to provide resistance to excessive glenohumeral translations and reduce the potential for instability of the joint, allowing surgeons to optimize postoperative functional gains on a patient by patient basis. ß
Biomechanics of anatomic and reverse shoulder arthroplasty
EFORT Open Reviews
The biomechanics of the shoulder relies on careful balancing between stability and mobility. A thorough understanding of normal and degenerative shoulder anatomy is necessary, as the goal of anatomic total shoulder arthroplasty is to reproduce premorbid shoulder kinematics. With reported joint reaction forces up to 2.4 times bodyweight, failure to restore anatomy and therefore provide a stable fulcrum will result in early implant failure secondary to glenoid loosening. The high variability of proximal humeral anatomy can be addressed with modular stems or stemless humeral components. The development of three-dimensional planning has led to a better understanding of the complex nature of glenoid bone deformity in eccentric osteoarthritis. The treatment of cuff tear arthropathy patients was revolutionized by the arrival of Grammont’s reverse shoulder arthroplasty. The initial design medialized the centre of rotation and distalized the humerus, allowing up to a 42% increase in the delt...
Journal of shoulder and elbow surgery / American Shoulder and Elbow Surgeons ... [et al.], 2016
A non-spherical humeral head has been shown to influence kinematics and stability of the glenohumeral joint; yet, most prosthetic humeral head components are designed to be a perfect sphere. The effect of humeral head shape on prosthetic joint kinematics after total shoulder arthroplasty is not well understood. We hypothesized that prosthetic joint kinematics during humeral axial rotation is dependent on humeral head shape, regardless of joint conformity. Four prosthetic configurations were investigated using a spherical and a non-spherical prosthetic humeral head articulated with a conforming and a non-conforming glenoid component. Testing was performed in the coronal, scapular, and forward flexion plane at 0°, 30°, and 60° of abduction. Prosthetic joint kinematics was measured in 10° intervals during a 100° arc of humeral axial rotation. Glenohumeral translation patterns, net glenohumeral translation, and averaged glenohumeral translation were compared for each of 4 configurations...
Joint stability after total shoulder arthroplasty in a cadaver model
Journal of Shoulder and Elbow Surgery, 1997
A cadaver model was used to test the hypothesis that glenohumeral joint stabi/i!y is independent of articular surface conformity aher total shoulder arthroplasiy. For the purposes of this study joint stability was defined as the minimum force required for joint dislocation. After arthroplasty components were implanted into fresh-frozen glenohumeral joints, specimens were mounted on a load frame and tested for joint stabilify. for each specimen the amount of conformiiy between the articular surfaces was varied from 0 to 5 mm by changing the humeral head radius of curvature. Because the glenoid component was not changed, the wall height, or joint constraint, was maintained constant for a given specimen. Variations in joint conformity changed dislocation forces by an average of only 3%. These small differences are not believed to be clinically relevant, indicating that design changes affecting the joint conformiiy of a total shoulder arthropkasty system will not significant/y affect glenohumeral joint stabiliv, assuming that all other factors remain constant. I./ SHOULDER ELBOW SURG 7 997;6:506-7 I .
Journal of Shoulder and Elbow Surgery, 2013
Introduction: Patients may experience a loss of internal rotation (IR) and external rotation (ER) after reverse total shoulder arthroplasty (RTSA). We hypothesized that alterations in the glenosphere position will affect the amount of impingement-free IR and ER. Materials and methods: Computed tomography (CT) scans of the scapula and humerus were obtained from 7 cadaveric specimens, and 3-dimensional reconstructions were created. RTSA models were virtually implanted into each specimen. The glenosphere position was determined in relation to the neutral position in 7 settings: medialization (5 mm), lateralization (10 mm), superior translation (6 mm), inferior translation (6 mm), superior tilt (20), and inferior tilt (15 and 30). The humerus in each virtual model was allowed to freely rotate at a fixed scaption angle (0 , 20 , 40 , and 60) until encountering bone-to-bone or bone-toimplant impingement (180 of limitation). Measurements were recorded for each scaption angulation. Results: At 0 scaption, only inferior translation, lateralization, and inferior tilt (30) allowed any impingement-free motion in IR and ER. At the midranges of scaption (20 and 40), increased lateralization and inferior translation resulted in improved rotation. Supraphysiologic motion (>90 rotation) was seen consistently at 60 of scaption in IR. Superior translation (6 mm) resulted in no rotation at 0 and 20 of scaption for IR and ER. Conclusions: Glenosphere position significantly affected humeral IR and ER after RTSA. Superior translation resulted in significant restrictions on IR and ER. Optimal glenosphere positioning was achieved with inferior translation, inferior tilt, and lateralization in all degrees of scaption.