Decision making in glenohumeral arthroplasty

Prosthetic replacement arthroplasty for glenohumeral arthritis is a well-developed and well-described technique with good and excellent results. The surgeon is faced with many decisions to make, however, regarding choice of implant, implant fixation, soft tissue management, and options for glenoid resurfacing. In general, when the precise cause of the arthritic condition is identified, the choices become more straightforward. For advanced osteoarthritis of the shoulder joint in an older patient with asymmetric posterior erosion of the glenoid, a total shoulder arthroplasty renders the best relief of pain and improvement in motion. Similarly, for advanced rheumatoid arthritis in patients with an intact rotator cuff, a total shoulder arthroplasty results in the best pain relief. If the rotator cuff is deficient and irreparable, an anatomically sized humeral head replacement is appropriate, taking care to preserve the coracoacromial arch. Acute, nonreducible fractures of the proximal humerus are treated best with a humeral head replacement. Post-traumatic arthropathy of the shoulder joint is treated with arthroplasty, and the decision to resurface the glenoid should take into account the age of the patient and the wear and concentricity of the glenoid. Many options exist for the choice of an implant; biomechanical and anatomic studies suggest that a better technical result can be achieved with a third-generation implant design that has the ability to recreate accurately the proximal anatomy of the humerus.     

Modulare Tumorprothesen des Humerus

The humerus is a common location of musculoskeletal tumors. Modular prostheses of the humerus, besides APC and biological reconstructions, allow restoration of resulting bone defects. The functional outcome is determined by the extent of bone and soft tissue loss. Anatomical shoulder prostheses have a limited abductor function, while shoulder function could be improved by an inverse prosthetic design and implants for ligament repair. Elbow prostheses provide satisfactory function. Our own results in 101 patients showed a 23% revision rate. The median overall survival was 171 months with an overall 5-year survival of 53%. With respect to good oncological outcomes modular reconstruction of the humerus is a feasible treatment option for cancer patients.     

肩关节相关生物力学介绍

肩关节是由胸锁关节、锁骨、肩锁关节、肩胛骨、盂肱关节、肱骨近端以及肩胛胸壁关节共同组成的复杂结构。在我们的临床工作中处理肩关节疾病时很有必要知道在正常的生理状态下,肩关节的结构、力学特点及运动规律。本文重点对与肩关节运动、功能有关的解剖特点以及生理状态下肩部运动及受力的情况进行了综述。     

5Effects of numeral component design on total shoulder arthroplasty

The last decade has brought exciting new ideas into the field of shoulder arthroplasty. This is particularly true withrespect to our understanding of humeral anatomy and how this relates to component design. Anatomic studies have informed the implant industry and surgeons alike leading to new implants and surgical techniques that better conform to normal anatomy. Proximal humeral anatomy is extremely variable. Radius of curvature varies from 20 to 30 mm, head shaft angle from 30° to 50°, offset is variable in 3 dimensions, and retroversion ranges from 0° to 50°. Equally variable are the prosthetic systems available for humeral replacement and the surgical techniques with which they are implanted. A modern approach to shoulder arthroplasty must incorporate an understanding of this variability to effectively reconstruct the anatomy of any particular patient. Available biomechanical information shows that displacing the position of the humeral articular surface by as little as 4 to 5 mm has significant consequences. Increasing the thickness by this amount tensions the overlying soft tissues and rotator cuff decreasing glenohumeral range of motion and introducing aberrant translations of the head on the glenoid. Shifting the articular surface similarly tensions corresponding aspects of the rotator cuff and may result in impingement ox the tuberosities on the glenoid rim, Exact replication of the patient's anatomy is probably not necessary, but staying within the stated limits is highly desirable. Cemented components facilitate this goal by allowing some adjustment of the prosthetic position within the cement mantle. Press-fit components that allow anatomic reconstruction have a significantly greater challenge.     

Hemiarthroplasty for proximal humeral fracture: restoration of the Gothic arch

Proximal humerus fractures are the most common fractures of the shoulder girdle, and initial management of these injuries often determines final outcome. When arthroplasty is used to manage proximal humeral fractures, surgery remains technically demanding, and outcomes have been unpredictable. Recent advances in both technique and prosthetic implants have led to more successful and reproducible results. Key technical points include restoration of the Gothic arch, anatomic tuberosity reconstruction, and minimal soft tissue dissection.     

Total shoulder arthroplasty: Factors influencing prosthetic sizing

Prosthetic sizing of the glenohumeral articulation influences postoperative shoulder strength stability and range of motion through its influence on the lateral humeral offset. Prosthetic sizing along with proper prosthetic orientation, soft tissue balancing, capsular release, and rotator cuff repair when necessary, are inter-related factors that significantly influence the function of the prosthetic shoulder. Intraoperative assessment of prosthetic size is determined by the lateral humeral offset rotator cuff tissue tension, intraoperative range of motion, and stability of the shoulder.     

Schulterendoprothetik bei posttraumatischen Deformitäten durch Frakturfolgen

The sequelae of fractures of the proximal humerus can be of considerable clinical significance. Careful classification of the sequelae allows precise determination of whether correction osteotomy, reconstruction, or implantation of one of the various prostheses available is indicated. The integrity of the greater tuberosity, its position and continuous osseous integration to the metaphysis of the proximal humerus is the most important predictive factor for a good outcome following implantation of an anatomical shoulder prosthesis. When there is some incongruence of the glenohumeral joint while the greater tuberosity remains intact, shoulder arthroplasty can give a better clinical outcome than is seen after arthroplasty for a primary fracture. In the case of nonunion of subcapital fractures the results achieved by reconstruction, i.e. bone grafting and internal fixation using plates with fixed-angle blades, are superior to those possible with an anatomical prosthesis. Reverse shoulder arthroplasty gives better results than anatomical prostheses in the treatment of severe tuberosity malunion. The results of reverse shoulder arthroplasty for the sequelae of fractures are also influenced by the integrity of or damage to the soft tissues, the muscles of the rotator cuff (teres minor muscle), and bone. Secondary interventions for the sequelae of fractures of the proximal humerus are complex and involve high rates of complications and revisions.     

Functional recovery after a reverse prosthesis for reconstruction of the proximal humerus in tumor surgery

An alternative treatment for primary bone tumors of the proximal humerus was assessed. Four patients, who made full functional recovery after complete resection of the proximal humerus inclusive of the rotator cuff and subsequent reconstruction with a reverse shoulder prosthesis, were examined clinically and radiographically. Distinct medialization of the center of rotation of the glenohumeral joint (28 mm) and elongation of the remaining deltoid muscle (116%) were measured. Increased scapular rotation (118%) was observed. The radiologic results and thoracoscapular rhythm analyses were implemented in a three-dimensional computerized model of the glenohumeral joint. This allowed us to calculate a doubling of the moment of the deltoid abductor muscle in the true scapular plane. After tumor surgery, in which the proximal humerus is resected without reinserting the rotator cuff, full functional recovery of the shoulder can be obtained with a total shoulder prosthesis, medializing the glenohumeral center of rotation and elongating the remaining deltoid muscle. Level of Evidence: Therapeutic study, Level IV (case series-no, or historical control group).     

Prosthetic replacement in acute fractures of the proximal humerus

The surgical treatment of selected displaced fractures of the proximal humerus with a humeral head prosthesis is a challenging procedure. Adequate knowledge of the pertinent anatomy and biomechanics of the shoulder as well as a clear roentgenographic evaluation of the displaced fracture patterns are essential. Successful prosthetic replacement requires adherence to technical factors involving soft tissue mobilization, prosthetic insertion, and tuberosity repair. Also, it is important to have a closely supervised rehabilitation program to achieve early passive motion and strengthening after fracture healing.     

Differences in reconstruction of the anatomy with modern adjustable compared to second-generation shoulder prosthesis

Reconstruction of the anatomy of the proximal humerus is a prerequisite to achieving good long-term clinical results after shoulder arthroplasty. Modern, adjustable prostheses have greater flexibility of inclination, retroversion, and medial and dorsal offset in comparison with older prostheses. Such improvements should allow for better reconstruction of the centre of rotation compared to older prostheses. Reconstruction of the humeral head centre was assessed in 106 modern adjustable (Affinis) and 47 second-generation prostheses. All reconstructions were compared both to the preoperative state and the unoperated shoulder. To describe the pre- and postoperative states, the geometry and position of the humeral head in relation to the glenoid were analysed on patient radiographs. Applying the defined parameters, modern adjustable prostheses showed better reconstruction than second generation prostheses. Parameter values measured in reconstructions using fourth generation prostheses were comparable to those of the unoperated shoulder, but differed significantly from the preoperative state. Second generation prostheses, in contrast, only show non-specific differences in parameter values. This suggests that an approximate reconstruction of normal anatomy can be achieved using a modern fourth generation prosthesis. Reconstruction of the complex anatomy of the proximal humerus is significantly better with modern adjustable prostheses compared to second generation prostheses. Improved clinical outcome can therefore be predicted in a functional and intact rotator cuff. The advantage of using modern prostheses systems over older models is clearly demonstrated in this study.     

Editorial Commentary: Superior Capsular Reconstructions in Cases of Irreparable Rotator Cuff Tendons Only Partially Restore Anatomy,Yet Significantly Normalize Biomechanics–Without Resorting to Reverse Anatomy

The goal of shoulder superior capsular reconstruction and/or anterior cable reconstructions, at least in terms of biomechanics, is to primarily restore a fulcrum to assist with pain control and functional optimization, with the secondary hope of maintaining cartilage. Fully restoring glenohumeral joint loads with SCR cannot be expected in the setting of persistent tendon insufficiency. Biomechanical studies characterizing shoulder capsular reconstructions have demonstrated anatomic and functional restorations toward normalization when tested with standard biomechanical methods. Glenohumeral abduction, superior humeral head migration, deltoid forces, and glenohumeral contact pressure and area, can be optimized toward the normal intact condition, as measured by motion tracking and pressure mapping in real time, using dynamic actuators. Insofar as restoring normal native anatomy is considered a fundamental priority, with the idea that joint functional longevity is enhanced by preserving anatomy, as surgeons, we should not lose sight of reconstruction over replacement (such as nonanatomic reverse total shoulder arthroplasty) as a favored goal. Anatomy-based reconstructions such as superior capsule or anterior cable reconstruction, may prove over time to be the best primary treatment as knowledge and innovations (technical and medical) develop, with nonanatomic arthroplasty truly being a last resort (yet a clinically viable option when indicated).     

Neer Award 2006: Biomechanical assessment of inferior tuberosity placement during hemiarthroplasty for four-part proximal humeral fractures

Tuberosity malpositioning commonly occurs and is associated with a decline in clinical function after prosthetic shoulder reconstruction for proximal humeral fractures. This study assesses the biomechanical effects of inferior tuberosity position on glenohumeral joint forces and humeral head position at multiple positions. Eight fresh-frozen cadaveric shoulders were tested. Hemiarthroplasty was performed with preservation of anatomic tuberosity height and with 10 mm and 20 mm of inferior tuberosity displacement. The rotator cuff, deltoid, pectoralis major, and latissimus dorsi muscles were statically loaded. Contact forces and humeral head position were recorded within a functional range of motion. Glenohumeral joint forces shifted significantly superiorly (P < .05) at 30 degrees of abduction after both 10 mm and 20 mm of tuberosity displacement. At 60 degrees of glenohumeral abduction, glenohumeral joint forces remained significantly altered after tuberosity displacement of 10 mm and 20 mm compared with the intact height (P < .005). This study demonstrates that, during hemiarthroplasty performed for proximal humeral fractures, malpositioning the tuberosities inferiorly results in significant superior glenohumeral joint force displacement. These findings suggest that the mechanical advantage of the shoulder abductor muscles is compromised with inferior tuberosity malpositioning and may help to explain inferior functional results seen in these patients.     

肩胛带骨肿瘤的外科治疗结果及评价

目的 探讨肩胛带骨肿瘤的手术切除方式、重建方法,观察术后功能恢复情况及临床结果.方法 回顾性分析1998年7月至2006年7月收治的71例肩胛骨周围骨肿瘤患者的病例资料,其中恶性肿瘤61例,骨巨细胞瘤10例.15例恶性肿瘤起源于肩胛骨,56例起源于肱骨近端.男42例,女29例;年龄11～62岁,平均36.5岁.手术方法:肩胛带离断术10例,单纯肩胛骨切除3例,肩胛骨切除、人工肩胛骨置换3例,部分肩胛骨及肱骨近端切除、假体置换8例,肱骨近端切除、假体置换47例.结果 10例骨巨细胞瘤患者肩周肌肉保留较好,术后MSTS功能评分平均28分.起源于肱骨近端的原发恶性骨肿瘤患者三角肌止点处均予以切除,术后肩外展30°～60°,MSTS功能评分平均23分.37例肱骨骨肉瘤患者中4例(10.8%)局部复发,2例骨转移,5例肺转移.7例转移患者均死亡.1例恶性骨巨细胞瘤患者出现肺转移死亡.3例尤文肉瘤患者出现肺转移死亡.5例肱骨及5例肩胛骨软骨肉瘤患者术后未见局部复发及转移.结论 肩胛带骨肿瘤切除、人工肱骨近端假体重建能保留完整肘部及手部功能、并发症少,是肩部恶性肿瘤的首选术式;肱骨近端骨肉瘤和下肢骨肉瘤比较预后较好;肱骨近端恶性肿瘤行关节内肿瘤切除和关节外肿瘤切除肿瘤的局部复发率接近,提示对多数肱骨近端恶性肿瘤可以采用关节内切除.     

Modular total shoulder: early experience and impressions

All design considerations in shoulder arthroplasty are based on reconstructing normal anatomy and enhancing prosthetic fixation, particularly on the glenoid side. These goals are further enhanced by meticulous attention to detail in placement of the component parts relative to the bony anatomy. In addition, great attention must be paid to management of the soft tissue tensions and placement of the component parts relative to soft tissue origins and insertions so that asymmetric overloading of the components can be avoided and loosening and wear can be minimized. The problem of management of prosthetic replacement with associated massive rotator cuff tears continues to be a dilemma. Use of an oversized humeral head articulating with the acromion can offer a compromise solution to the problem. This technique can be combined with altered glenoid component placement or reshaping of the bony glenoid to accommodate its altered relationship with the humeral articular surface. Future design changes are needed to deal with this complex problem.     

Shoulder prostheses treating cuff tear arthropathy: a comparative biomechanical study.

Painful cuff tear arthropathy (CTA) affects the independence of the elderly. Surgical treatment often consists of joint replacement, the functional outcome of which remains variable. Knowledge of the biomechanical properties of the different prosthetic designs can guide the orthopaedic surgeon in the choice of implant to predict its clinical result. A 3-D computer model of the glenohumeral joint is used to analyse the moment of the deltoid muscle in the scapular plane. A geometrical 3-D ball-and-socket model of the shoulder joint was used to calculate (1) the angle-force relationships, (2) the moment arm of the deltoid muscle and (3) the moment of the deltoid muscle components, for increasing degrees of arm elevation in the scapular plane. In this 3-D model, a clinical thoraco-scapular rhythm analysis was implemented, based on measurements in normal subjects, patients treated with an anatomical prosthesis and patients treated with an inversed delta III prosthesis. These data were compared for 10 different prosthetic treatment options. RESULTS: Muscle angle-force curves show a favourable slope in non-anatomical prosthetic designs, where the centre of rotation of the glenohumeral joint is medialized, the deltoid muscle is elongated and the humeral shaft is lateralized. On the contrary, anatomical prosthetic designs do not perform well in this computer analysis. CONCLUSIONS: From a biomechanical point of view, a shoulder prosthesis which medializes the centre of rotation, lengthens the deltoid muscle and increases the deltoid lever arm, results in a significantly more powerful abduction of the shoulder, despite complete loss of rotator cuff function. RELEVANCE: This study explains why a successful functional outcome can be expected in CTA with a reversed prosthesis.     

Influence of neck shaft angle of humerus in prosthesis design

BackgroundA better understanding of the proximal humerus is essential for anatomical reconstruction of the glenohumeral joint during prosthetic replacement. The neck-shaft angle is critical for correct calcar screw positioning when fixing a proximal humeral fracture with a locking plate. It's essential for exact implant placement and treatment of any soft-tissue or bone pathology. Improper implants cause discomfort and post-operative complications, therefore understanding the humeral neck shaft angle is fundamental in the design and manufacturing of prostheses. This study looked into the necessity regional data of the humeral neck shaft angle (NSA) and its importance in shoulder prosthesis manufacturing.MethodThis cross-sectional investigation was conducted on 300 dry cadaveric humeri of unknown gender and age that were free of damage or deformity. The Goniometer was used to measure the neck shaft angle. The data was analysed using SPSS software. The standard deviation and mean were calculated. The statistical difference between the right and left humeri was assessed using the students' t' test.ObservationsThe NSA of the humerus was 131.265.82° on average. The NSA mean values were substantially higher on the right side. A statistically significant difference between the right and left humeri was revealed by a P value of 0.001.ConclusionSuccess of the shoulder arthroplasty demands anatomical reconstruction of the normal neck-shaft angle of the humerus. Racial variations in the morphometry of the neck-shaft angle needs to be considered in prosthesis design.     

A successful reconstruction using a frozen autograft and a pedicled latissimus dorsi flap after a S12345B shoulder girdle resection in a patient with osteosarcoma

We present a case of high-grade osteosarcoma in the proximal humerus in an 8-year-old boy. Massive tumor expansion required a S12345B shoulder girdle resection according to the system of the Musculoskeletal Tumor Society. After wide resection, only a small portion of the distal humerus and none of the rotator cuff muscles would be spared. Because the humeral portion would be too short to support the stem and the soft tissue would be insufficient to cover prosthetic components, we designed a composite reconstruction using a frozen autograft and a pedicled muscle flap. At 2 years postoperatively, our patient exhibited good adaptation and had acquired fine dexterity of the upper limb. To our knowledge, this is the first report regarding a successful composite reconstruction after a S12345B shoulder girdle resection.     

Limb-sparing resections of the shoulder girdle

BACKGROUND: Limb-sparing surgeries around the shoulder girdle pose a surgical difficulty, because tumors arising in this location are frequently large at presentation, are juxtaposed to the neurovascular bundle, require en bloc resection of proportionally large amounts of bone and soft tissues, and necessitate complex resection and reconstruction. STUDY DESIGN: Between 1980 and 1997, we treated 134 patients who presented with 110 primary malignant, 12 metastatic, and 12 benign aggressive bone and soft tissue tumors of the shoulder girdle and subsequently underwent a limb-sparing resection. Reconstruction of the bone defect included 92 proximal humerus and 9 scapular prostheses. All patients were followed up for a minimum of 2 years. We summarize the principles of limb-sparing resections of the shoulder girdle, with emphasis on the surgical anatomy of the shoulder girdle, principles of resection and reconstruction, and functional outcomes. RESULTS: Function was estimated to be good or excellent in 101 patients (75.4%), moderate in 23 patients (17.1%), and poor in 10 patients (7.5%). Complications included 13 transient nerve palsies, 2 deep wound infections, and 1 prosthetic loosening. Local tumor recurrence occurred in 5 of 103 (4.9%) patients with primary sarcomas of the shoulder girdle. CONCLUSIONS: Detailed preoperative evaluation and surgical planning are essential for performing a limb-sparing resection around the shoulder girdle. Local tumor control, associated with good functional outcomes, is achieved in the majority of patients.     

Geometric analysis of selected press fit prosthetic systems for proximal humeral replacement.

The ability of a prosthetic system to replicate a wide range of normal anatomy appears dependent in part to its capacity to produce variable prosthetic geometries. Several modern designs have recently been developed in order to provide multiple prosthetic options. The purpose of this study was to compare the geometry of select press fit prosthetic systems in terms of their ability to match normal three-dimensional geometry of the proximal humerus. The anatomy of 60 humeral specimens from 30 cadavers known from CT data and computer-aided design (CAD) analysis was compared to a 1996 database of four conventional shoulder prosthetic systems (fixed inclination angle, one medial-lateral offset position per head) and one so-called anatomic system (variable inclination angles, multiple head offset positions). The prosthetic system with greatest geometric options allowed for a significantly better replication of the anatomy. Average displacement of the center of rotation was 2.1 mm compared to 9.7 mm for the other systems combined. Reduction in surface arc was 12 degrees compared to 32 degrees. The most problematic feature of conventional prosthetic systems in terms of replicating normal humeral anatomy is the gap created by the prosthetic collar and Morse taper.