The effect of articular malposition after total shoulder arthroplasty on glenohumeral translations, range of motion, and subacromial impingement (original) (raw)
Related papers
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.
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
Journal of Shoulder and Elbow Surgery, 2010
Hypothesis: We hypothesized that the malpositioning of the humeral component can preclude the longterm success of anatomical total shoulder arthroplasty. The goal of this study was to evaluate the mechanical consequences of superior and inferior malpositioning of the humeral head. Materials and methods: A numerical musculoskeletal model of the shoulder joint allowing natural humeral head translation was used to simulate a loaded abduction movement controlled by muscular activation. An inferior and superior malpositioning of 5 mm were compared to an optimal positioning. Impingements, articular contact pattern, and cement stress were evaluated. Results: Inferior malpositioning of the humeral head induced impingement and limited the abduction level, while superior malpositioning increased the subluxation risk. Both inferior and superior malpositioning increased the stress level within the cement mantle. Discussion: This numerical study highlights the importance of an anatomical reconstruction of the glenohumeral surfaces for the success rate of anatomical total shoulder arthroplasty.
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...
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...
Reverse shoulder arthroplasty components and surgical techniques that restore glenohumeral motion
Journal of Shoulder and Elbow Surgery, 2013
Background: Modifications in reverse shoulder arthroplasty (RSA) have been made with the intent of maximizing motion, although there is little objective evidence outlining their benefit. This study investigated the RSA component combinations that impart the greatest effect on impingement-free glenohumeral motion. Methods: A previously validated virtual shoulder model was implanted with RSA components that varied by humeral implant type (inset/onset), glenosphere diameter (30, 36, and 42 mm), glenosphere placement (inferior/neutral), glenosphere center-of-rotation offset (0, 5, and 10 mm), humeral neck-shaft angle (130 and 150 ), and humeral offset (zero, five, and ten mm). Motion was simulated in all technique combinations until the point of impingement in abduction, flexion/extension (F/E), and internal/external rotation (IR/ER). Regression analysis was used to rank combinations based on motion. Results: Of 216 possible study combinations, 126 constructs (58%) demonstrated no arm-at-side impingement and were included for analysis. Models with the largest motion in abduction, F/E, and IR/ER, respectively, were inset-42-inferior-10-150-zero (107 ), inset-36-inferior-10-130-five (146 ), and inset-42-inferior-10-130-ten (121 ). Humeral neck-shaft angle, glenosphere center-of-rotation offset, glenosphere placement, and glenosphere diameter had a significant effect on motion in all planes tested. Of these variables, humeral neck-shaft angle was most predictive of a change in abduction and F/E motion, whereas glenosphere placement was most predictive of a change in IR/ER motion. Conclusion: Higher glenosphere center-of-rotation offsets led to an increase in motion in all planes. To maximize motion in abduction, a valgus humeral component should be selected; to maximize F/E, a varus humeral component should be selected; and, to maximize IR/ER, the glenosphere should be placed inferiorly.
2005
The purpose of this study was to determine whether plane, end-range determination, or scapular motion affects shoulder range-of-motion measurements. In 16 healthy subjects, instrumentation with a magnetic tracking device was used to measure shoulder internal and external range of motion. The arm was supported while it was rotated either actively or passively with a measured torque. There was a significant main effect of plane for internal rotation (P Ͻ .001) but not for external rotation (P ϭ .584). Passive humerothoracic motion was significantly greater than active humerothoracic motion for internal rotation (P Ͻ .006) and external rotation (P Ͻ .01). Active and passive humerothoracic motion was significantly greater than active and passive glenohumeral motion in 6 of the 7 active conditions and all 7 passive conditions (P Ͻ .002). Our results suggest that significant amounts of scapulothoracic motion may impact measurements of isolated glenohumeral joint motion. (J Shoulder Elbow Surg 2005;14:602-610.) The shoulder is one of the most mobile joints in the human body and moves in a complex 3-dimensional pattern. This motion is accomplished through coordinated interactions between 3 diarthrodial articulations: the glenohumeral, acromioclavicular, and sternoclavicular joints, of which the former has the largest range of motion. However, this mobility comes at a price, as this joint is the most frequently dislocated in the body. Whereas active muscle contraction and glenoid geometry are primarily responsible for stability in the mid ranges of motion, the ligaments and capsular structures are mainly responsible for stability at the end ranges of motion. 36,46 A failure of any of these stabilizers can negatively affect shoulder kinematics and may result in decreased glenohumeral joint function. From a biomechanical perspective, the glenohumeral joint is typically described as having the following 3 degrees of rotational freedom: plane of motion, elevation, and internal and external rotation. 2 Although many of the traditional studies of shoulder motion have primarily focused on shoulder elevation, 20,43 there has been considerable interest of late in measuring internal and external rotation along the long axis of the humerus. 9,45 Study of this motion is important for two main reasons. First, the available range of internal and external rotation impacts shoulder function, from simple activities of daily living, such as hair combing, to more complex tasks required by athletes and occupational workers. Depending on the level of force applied throughout the shoulder joint, osseous and soft-tissue adaptations can result from repetitive shoulder motions. For example, bodybuilders have a decreased internal range of motion, 5 whereas professional baseball pitchers have an increased external range of motion coupled with a decreased internal range of motion. Second, measurements of internal and external rotation can be used as indicators of capsular tightness. Cadaveric studies using either selective cutting protocols 11,24,34,39,50 or strain measurements, 14,42,49,52 as well as numerical models, have been used to assess the extent to which various portions of the capsule limit rotation. Clinically, measurements of capsular tightness are used in the assessment of patients with impingement syndrome. The American Academy of Orthopaedic Surgeons' current recommendations for clinical measurement of shoulder rotation is by goniometer for external rotation with the arm at the side and for internal and external rotation with the arm at 90°of humeral abduction. In addition, internal rotation with the arm at the side is assessed by having the patient reach behind his or her back and noting what vertebral level can be reached with the thumb. These measurements are cost-effective and easy to perform and have fair to good intrarater and interrater reliability. 28 However, from a biomechanical perspec-From the
This numerical study assesses the influence of an oversized humeral hemiprosthesis with a larger medial offset on the mechanics of the shoulder with cuff tear arthropathy (CTA). Shoulder elevation in the scapular plane is performed, and a Seebauer Type IIa CTA is simulated: a massive rotator cuff tear, a proximal and static migration of the humeral head, and two contacts with friction (glenohumeral and acromiohumeral). The CTA model without a prosthesis (friction coefficient 0.3) is evaluated first as a reference model. Then, three humeral head prosthetic geometries (friction coefficient 0.15) are evaluated: anatomical head, oversized head, and oversized head with a large medial offset. The function of the middle deltoid (i.e. moment arm, applied force, and strength), the contact forces, and the range of motion are studied. The anatomical head, which reduces friction by half, decreases the middle deltoid force (25%) and the contact forces (glenoid 7%; acromion 25%), and increases the range of motion from 41 to 541. The oversized head increases the moment arm (15%) and the middle deltoid strength (13%), which further decreases the deltoid force (7%) and the contact forces (glenoid 7%; acromion 17%), and increases the range of motion from 541 to 691. The oversized head with a large medial offset enhances these effects: the moment arm increases by another 3.1%, the deltoid force decreases by another 5% and the acromiohumeral contact force by another 12%, and the range of motion increases from 691 to 841. These results suggest that increasing the medial offset and oversizing the hemiprosthetic head improve the function of the deltoid, reduce acromial solicitation, and restore elevation to almost 901.