Reverse total shoulder arthroplasty

Reverse total shoulder arthroplasty designs have gained popularity over the last few years due to their satisfactory functional results in patients with cuff‐tear arthropathy and other difficult reconstructive shoulder problems. These semiconstrained prostheses improve stability and active elevation in the absence of a functional rotator cuff by coupling a spherical glenoid component with a concave humeral component and increasing deltoid tension. Understanding the anatomy of the shoulder is critical in order to ensure secure fixation of the glenoid component, explore uncemented options for humeral component fixation, and determine the ideal soft‐tissue tension to provide the best functional outcome without increasing the risk of complications. Key anatomic elements to be considered for the successful implantation of a reverse prosthesis include the orientation and size of the glenoid vault, the scapular regions with better bone stock (coracoid, spine of the scapula), the internal geometry of the humeral medullary canal, and the effects of reverse arthroplasty on the deltoid and brachial plexus. Clin. Anat. 22:172–182, 2009. © 2008 Wiley‐Liss, Inc.     

肩胛骨关节盂的位置数据测量及其临床意义

目的 利用肩胛骨上较为明显的3个点获得关节盂的位置数据,从而分析出肱骨头和关节盂之间的力传递关系,为肩部运动障碍的治疗提供依据。 方法 选取干燥的标本68例,经过测量,计算出肩胛骨上3个可触及的点所决定的平面与关节盂中心和前两个点所决定的平面所形成的角（临界角θ）,这个临界角θ可以让我们从肩胛骨上3个明显的点获得关节盂的位置数据。 结果 经过测量,计算得到θ值的范围为(31.36±4.65)°。结论 可利用已知的θ和肩胛骨上3个较为明显的点来计算跨肩关节的力,从而为肩部运动障碍的患者优化加强锻炼的选择。     

A musculoskeletal shoulder model based on pseudo-inverse and null-space optimization

The goal of the present work was assess the feasibility of using a pseudo-inverse and null-space optimization approach in the modeling of the shoulder biomechanics. The method was applied to a simplified musculoskeletal shoulder model. The mechanical system consisted in the arm, and the external forces were the arm weight, 6 scapulo-humeral muscles and the reaction at the glenohumeral joint, which was considered as a spherical joint. The muscle wrapping was considered around the humeral head assumed spherical. The dynamical equations were solved in a Lagrangian approach. The mathematical redundancy of the mechanical system was solved in two steps: a pseudo-inverse optimization to minimize the square of the muscle stress and a null-space optimization to restrict the muscle force to physiological limits. Several movements were simulated.The mathematical and numerical aspects of the constrained redundancy problem were efficiently solved by the proposed method. The prediction of muscle moment arms was consistent with cadaveric measurements and the joint reaction force was consistent with in vivo measurements.This preliminary work demonstrated that the developed algorithm has a great potential for more complex musculoskeletal modeling of the shoulder joint. In particular it could be further applied to a non-spherical joint model, allowing for the natural translation of the humeral head in the glenoid fossa.     

喙肩弓对肩关节前上方稳定性作用的生物力学研究

目的探讨对喙肩弓进行不同程度破坏时肩关节前上方稳定性所受到的影响。方法选取新鲜成人冷冻肩关节尸体标本36个,随机平均分为3组后进行不同的处理。组1,保留完整的喙肩韧带;组2,破坏一半喙肩韧带;组3,将喙肩韧带全部破坏。然后分别将肩关节标本固定生物力学试验机上进行力学实验;对肱骨干施加轴向压力时,肱骨头向前上方移动,记录肱骨头在50 N压力时的位移距离。结果在50 N压力作用下,组1、2、3肱骨头位移距离分别为(2.50±0.59)、(5.38±0.71)、(6.49±0.81)mm。3组数据组间比较均存在明显统计学差异(P0.05)。结论喙肩弓的破坏会影响肩关节前上方的稳定性。喙肩弓的破坏程度越大,肩关节前上方的稳定性就越差。     

Humeral internal rotation osteotomy for the treatment of Erb-Duchenne-type obstetric palsy: clinical and radiographic results

OBJECTIVE:

To evaluate the functional and radiographic results in patients undergoing shoulder anterior soft tissue stretching in association with open reduction and internal rotation osteotomy to centralize the humeral head as a treatment for Erb-Duchenne obstetric palsy sequelae.

METHOD:

A total of 35 patients underwent this surgical treatment, and the mean follow-up was 4.6 years. The Mallet scale was applied before and after the surgical procedure. A total of 20 patients underwent computed tomography to assess the glenoid version and humeral head subluxation.

RESULTS:

Functional improvement was achieved, as evidenced by an increase in the Mallet scale score from 12.14 to 16.46 (p<0.001). The correction of retroversion was achieved once the glenoid version ranged from -21.4 to -12 degrees (p<0.001). The humeral head subluxation improved from 6.5 to 35.2% (p<0.001). Patients older than 6 years of age did not achieve glenohumeral joint improvement with respect to dysplastic abnormalities.

CONCLUSION:

Internal rotation osteotomy in association with the stretching of anterior soft tissues of the shoulder in patients under the age of 7 years provided improvements in the function, retroversion, and subluxation of the glenohumeral joint.     

The effect of different humeral prosthesis fin designs on shoulder stability: A computational model

Humeral prostheses commonly use a fin structure as an attachment point for the supraspinatus muscle in total shoulder arthroplasty (TSA), but these fins may cause injury to the muscle during implantation, inadvertently influencing stability. In order to prevent supraspinatus injury, the effect of different humeral prostheses on shoulder joint stability needs to be investigated. A commercially available prosthesis and two modified humeral prostheses that substituted the fin structure for 2 (2H) or 3 holes (3H) were evaluated using computational models. Glenohumeral abduction was simulated and the superioinferior/anterioposterior stability of the shoulder joint after TSA was calculated. The results revealed that the 2H design had better superioinferior stability than the other prostheses, but was still less stable than the intact shoulder. There were no obvious differences in anterioposterior stability, but the motion patterns were clearly distinguishable from the intact shoulder model. In conclusion, the 2H design showed better superioinferior stability than the 3H design and the commercial product during glenohumeral joint abduction; the three prostheses show similar results in anterioposterior stability. However, the stability of each tested prosthesis was not comparable to the intact shoulder. Therefore, as a compromise, the 2H design should be considered for TSA because of its superior stability.     

Biomechanics of the deltoideus

The objective of this study was to determine the direction of the migration engendered by the middle deltoideus on the upper end of the humerus. Eleven patients suffering from shoulder pathology underwent an MRI examination (3 mm thick slices). From these MRI slices, 3D reconstructions were obtained for each patient by using a manual data capture system (SliceOmatic^®). From this geometry, a mechanical model of the deltoideus was produced, taking into account the contacts between the latter and the following anatomical parts: supraspinatus, infraspinatus and humeral head. For the 11 shoulders, we have obtained a deltoideus showing a global resultant oriented upwards. There was, however, a component oriented downwards (at the level of the humeral head), its intensity being 40–80% less than the component oriented upwards (at the level of the deltoideus V). It is important to note that this study is valid only in the initial degrees of lateral elevation. The deltoideus is an elevator muscle of the humeral head in the glenoid, presenting nevertheless a component oriented downwards. The deltoideus would, therefore, intervene to recenter the shoulder during an abduction movement.     

人工肱骨头置换中使用胸骨针行肱骨近端骨折肩袖重建

背景：越来越多的粉碎、移位严重而无法重建的肱骨近端骨折患者需要行人工肱骨头置换,但此类患者肩袖的重建直接影响治疗效果,置换过程中往往需要良好的肩袖重建。 目的：探讨胸骨针在肱骨近端骨折人工肱骨头置换肩袖重建中的应用体会。 方法：34例肱骨近端四部分骨折患者行人工肱骨头置换时使用胸骨针修复肩袖,年龄67-78岁。人工肱骨头置换时未过分剥离骨折块与肩袖组织,保留肩袖组织与骨块相连,将胸骨针沿着肩袖大小结节表面肌腱-骨结合部环形缝合备用,可用多根,假体置入后,将肱骨大、小结节及碎骨块解剖复位,收紧胸骨针,大小结节及肩袖附着的碎骨块均原位贴在人工肱骨头下方。术中应尽可能将残余的肩袖和肌肉组织损伤进行缝合修复,并要注意缝合后的动力平衡。采用Neer标准对人工肩关节功能的恢复情况进行评价。 结果与结论：34例患者均获随访,随访时间1-3年,24例优,10例良,2例可;无关节脱位、半脱位等关节不稳情况,未见感染、神经损伤及假体松动病例。提示人工肱骨头置换过程中使用胸骨针进行肩袖修复及大小结节固定能使肩袖和大小结节接近解剖位置,并且比常规的涤纶线强度高,固定牢靠,能满足人工肱骨头置换后康复训练的需要,对肩关节的稳定性及功能恢复有重要作用。     

Glenohumeral relationship in maximum elevation

Purpose

The purpose of this study was to clarify rotational relationships between the anatomical landmarks of the glenohumeral joint in maximum elevation.

Methods

Twenty-five healthy volunteers (20 men, 5 women; mean age, 31 years) held the arm in maximum elevation in an open MRI system. In each three-dimensionally computer-generated image, elevation angle of the humerus in the plane of elevation was measured, based on the glenoid and the scapular planes. Using the equator set on the head surface by the plane parallel to the humeral axis, involving the head center and the bicipital groove, glenoid location and rotational relationships were investigated.

Results

The elevation angle was 102° ± 9° in the plane 7° ± 8° anterior to the scapular plane, and axial rotation was fixed with the glenoidal long axis parallel to the equator (within 2°). Each glenoid center located on antero-superior portion of the humeral head, and the direction from the top of the head to its location was the same as that of the shaft tilting, indicating the glenoid only translated without rotation after reaching the top of the head on the equator.

Conclusions

Before reaching maximum elevation, the glenohumeral joint would be locked in axial rotation. The position when the glenoid is on the top of the humeral head with the humeral shaft perpendicular to the glenoid is considered to be essentially the final position of elevation, above which the glenohumeral joint only translates without axial rotation even if the humerus is more elevated.     

"Floating-socket" total shoulder replacement: anatomical, biomechanical, and surgical rationale

A prosthesis based on a new concept of gleno-humeral motion has been developed and clinically tested for the past 2 years. The "floating-socket" total shoulder replacement contains a nondislocatable, dual spherical bearing system consisting of a small sphere within a larger sphere with their centers offset to provide the physiologic "floating fulcrum" for mechanically advantageous motion. This geometric configuration allows a prosthetic range of motion in excess of anatomical limits to allow soft tissue structures to limit motion rather than mechanical impingement. The device is constructed from Co--Cr--Mo alloy and RCH-1000 polyethylene such that no metal--metal contact can occur. Experimental results in a 112-lb adult male chimpanzee and six clinical cases have revealed superior fixation strength of both glenoid and humeral components, as well as functional adaptation of the prosthesis without fracture of fixturing bone or prosthetic dislocation.     

人工肱骨头置换治疗老年肱骨近端三、四部分骨折疗效分析

目的　探讨人工肱骨头置换治疗老年肱骨近端三、四部分骨折的适应症、手术方法及临床疗效。 方法　对采用人工肱骨头置换治疗的39例老年肱骨近端复杂骨折患者进行回顾性分析,其中三部分骨折15例,四部分骨折24例,采用肩关节功能Neer评分及疼痛视觉模拟评分(visual analog scale,VAS)对术后肩关节功能和术后疼痛程度等进行随访对比观察。 结果 本组病例全部得到随访,随访时间 12~32 个月,平均 24 个月,Neer 评分: 优 15 例,良 18例,可 5 例,差1例,优良率 84.6%。 结论　人工肱骨头置换治疗老年肱骨近端三、四部分骨折疗效满意,术中假体的正确植入、肩袖的有效修复、大小结节的正确重建以及个体化的早期关节功能锻炼,是确保术后疗效的关键。     

Mineralisation patterns in the subchondral bone plate of the humeral head

Purpose  

Pathologic changes of the glenohumeral joint, like a long-standing overloading or an accident often lead to severe glenohumeral osteoarthritis, and a glenohumeral joint replacement could be necessary. Joint instability and glenoid loosening are the most common post-operative complications, which can be caused by eccentric loading of the glenoid, if the humeral head is malcentered. If these malcentered cases could be identified pre-operatively, the pathologic position of the humeral head could be fixed intra-operatively and complication may be prevented. Computed tomography osteoabsorptiometry (CT-OAM) is a useful method to determine the distribution of mineralisation in the subchondral bone as a marker for the long-term loading history of a joint. The objective of this study was to gain information about the mineralisation distribution in the subchondral bone plate of the humeral head.     

Rotator cuff fatigue and glenohumeral kinematics in participants without shoulder dysfunction

CONTEXT: Researchers have established that superior migration of the humeral head increases after fatigue of the rotator cuff muscles. In these studies, the investigators used imaging techniques to assess migration of the humeral head during statically held shoulder positions. Their results may not represent the amount of superior humeral head migration that occurs during dynamic arm elevation. OBJECTIVE: To investigate the effect of rotator cuff fatigue on humeral head migration during dynamic concentric arm elevation (arm at the side [approximately 0 degrees ] to 135 degrees ) in healthy individuals and to determine the test-retest reliability of digital fluoroscopic video for assessing glenohumeral migration. DESIGN: Test-retest cohort study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty men (age = 27.7 +/- 3.6 years, mass = 81.5 +/- 11.8 kg) without shoulder disorders participated in this study. INTERVENTION(S): Three digital fluoroscopic videos (2 prefatigue and 1 postfatigue) of arm elevation were collected at 30 Hz. The 2 prefatigue arm elevation trials were used to assess test-retest reliability with the arm at the side and at 45 degrees , 90 degrees , and 135 degrees of elevation. The prefatigue and postfatigue digital fluoroscopic videos were used to assess the effects of rotator cuff fatigue on glenohumeral migration. All measurements were taken in the right shoulder. MAIN OUTCOME MEASURE(S): The dependent measure was glenohumeral migration (in millimeters). We calculated the intraclass correlation coefficient and standard error of the measurement to assess the test-retest reliability. A 2 x 4 repeated-measures analysis of variance was used to assess the effects of fatigue on arm elevation at the 4 shoulder positions. RESULTS: The test-retest reliability ranged from good to excellent (.77 to .92). Superior migration of the humeral head increased postfatigue (P < .001), regardless of angle. CONCLUSIONS: Digital fluoroscopic video assessment of shoulder kinematics provides a reliable tool for studying kinematics during arm elevation. Furthermore, superior migration of the humeral head during arm elevation increases with rotator cuff fatigue in individuals without shoulder dysfunction.     

经皮导入内固定治疗肱骨近端骨折合并肩关节前脱位的力学分析

目的　通过力学分析研究经皮导入内固定方法治疗肱骨近端骨折合并肩关节前脱位的可行性。方法　实验分二部分进行：一是用尾部加压调角空心螺纹钉按手术操作进行拉脱试验，测定将螺纹钉从肱骨头内拉出所需最小力(P(下标 min))；二是利用生物力学测试机测定志愿者单纯肩关节前脱位麻醉下牵引复位所需的最大力(P(下标 max))。实验按年龄分为A、B两组，A组25~45岁，B组＞45岁。对两组测试数据进行数据分析。结果　当尾部加压调角空心螺纹钉拧入肱骨头20 mm时，螺钉自肱骨头内拉出所需最小拉力P(下标 minA)=284N，P(下标 minB)=198N，牵引复位单纯肩关节前脱位所需最大拉力P(下标 maxA)=206N，P(下标 maxB)=195N，通过比较极值，得出P(下标 min)>P(下标 max)，即牵引复位单纯肩关节前脱位所需最大拉力小于螺钉自肱骨头内拉出的最小拉力。结论　尾部加压调角空心螺纹钉对肱骨头的固定作用可满足经皮导入内固定治疗肱骨近端骨折合并肩关节前脱位过程中的要求。     

家兔肩关节与髋关节软骨扫描电镜观察

应用扫描电镜对家兔肩关节和髋关节软骨观察发现:关节盂中央部和周围部软骨表面,分别有纤维网层和絮网层结构,甚为丰厚;髋臼的月状软骨表面,有由纤维编织而成的复杂网状结构,其中,网架纤维交错,网孔平面取向各异.肱骨头与股骨头软骨表面分别具絮网层和纤维网层结构,前者丰厚,后者细密而紧实.     

A radiographic study of hip-joint alignment after prosthetic hip arthoplasty

Postoperative hip alignment was studied on radiographs in cases of total hip arthroplasty (THA) and of Bipolar Head Prosthesis(BHP), both with MX-1. Postoperative anteroposterior-view radiographs of hip joints of patients with a normal hip joint on the unoperated side and without pelvic tilt were used. Thirty-nine THA patients (femoral neck fracture), 26 THA patients (osteonecrosis of the femoral head and osteoarthritis of the hip joint), and 34 BHP patients were selected for this study. Lines and points for measurement of 9 parameters were established on radiographs. The position of the greater trochanter upper edge is 6.5 mm (mean) superior to the femoral head center in the normal hip joint of Japanese, unlike in Caucasians. A femoral head prosthesis should be inserted so that its center and the greater trochanter upper edge are level in order to equalize leg lengths. In BHP cases, the insertion is made so that the greater trochanter upper edge is approximately 4-mm superior to the center of the prosthesis. For further securing of the stem and to equalize leg lengths, stems should be available in 11 diameters from 5-15 mm in 1-mm increments. Postoperative hip alignment in MX-1 THA cases was found to be satisfactory.     

肩部投掷运动的生物力学研究

利用高速彩色电视摄像机，对肩部投掷运动进行动态分析研究，所有资料数据通过计算机处理分析，得出运动的速度，位置和角度的变化资料，肩部的运动以额状面，水平面和矢状面的动态的线条图表示。结果表明：肩关节既是肢体和躯干的连接点，又是上肢运动的支点，是保证上肢完成三维空间活动的重要结构。在肩部的运动中，阻力，重力和肌肉的收缩力集中于肱骨轴线，通过盂肱关节面转换为与关节盂面垂直的压力和与关节盂面平行的剪力，作用于肩部活动的全过程。压力与剪力的相互转换关系，取决于肢体运动时通过盂肱关节面的应力，以及肩胛盂和肱骨之间的相     

Specimen-Specific Method for Quantifying Glenohumeral Joint Kinematics

The existing glenohumeral joint kinematic protocols are highly effective for studying in vivo shoulder kinematics but are not anatomically specific enough to address the asymmetric changes in glenohumeral joint kinematics and do not provide clear anatomic definitions for landmarks and directions. Therefore, the objective of this study was to develop an anatomically relevant and specimen-specific three-dimensional glenohumeral joint kinematic method as a new standard definition protocol for the glenohumeral coordinate systems (CSs). The in situ kinematic data of the intra-capsular glenoid-based CS of the glenohumeral joint were mathematically determined from the kinematic data of the extra-capsular CSs measured with an intact capsule. To minimize irreproducibility arising from discrepancy in initial specimen condition and error in determining CSs, several techniques were employed to determine anatomical landmarks and directions. To examine and demonstrate the details of this method, six fresh frozen cadaveric shoulders were used with a custom shoulder testing system. The accuracy and repeatability in the humeral head center (HHC) measurement were 0.44 and 0.41 mm, respectively. The inter-observer reliability for the location of the glenoid CS origin and HHC were 0.37 and 0.30 mm, respectively. The smaller anteroposterior (AP) depth of the glenoid with respect to the superoinferior (SI) depth (27.3 ± 16.5%) was significantly correlated to the larger AP/SI translation ratio of the humeral head apex (191.4 ± 43.8%, R = 0.90, p = 0.02). This study provides a glenohumeral kinematic protocol that enables the assessment of asymmetric glenohumeral kinematics determined by a precise and reproducible method using anatomic landmarks.     

Glenohumeral relationships at different angles of abduction

Purpose

The objective of this study was to clarify the relationships among anatomical landmarks of the glenohumeral joint at different angles of abduction.

Methods

Fifteen volunteers (ten men, five women; mean age 29 years) were enrolled in this study. Images of externally and internally rotated positions at 45°, 90°, and 135° of abduction in the plane 30° anterior to the trunk were taken using an open magnetic resonance imaging system. Landmarks including the glenoidal long axis with its center, bicipital groove, center of the head, and humeral shaft axis were determined. Using a line set on the surface of the head in the plane parallel to the humeral axis (including the head center and bicipital groove with its parallel and perpendicular lines), the glenoid location and rotational relationships were investigated in each position.

Results

The average angles of axial rotation were 48° ± 27° at 45º of abduction, 71° ± 20° at 90° of abduction, and 40° ± 27° at 135° of abduction. The trajectories of the glenoid center primarily extended over the anterior portion of the humeral head at 45° of abduction and over the posterior portion at 90° of abduction, while those at 135° of abduction were localized on a small upper portion of the head.

Conclusions

The glenohumeral relationships demonstrated that arm abduction might influence shoulder function through its effects on the portion of the humeral surface in contact with the glenoid during rotation and the resultant changes in the glenohumeral relationships.