肩关节置换术后关节不稳的生物力学研究进展

肩关节是人体活动范围最大的关节,属球窝关节。正常肩关节的被动活动范围取决于喙肩弓的外形和结构,以及在关节极度旋转时的关节囊紧张程度[1]。其稳定性取决于过关节的静力性结构(包括韧带和肌腱)和动力性结构(肌肉收缩)之间复杂的相互作用,而关节面对合、关节翻转、关节腔负压及关节面的黏附和内聚作用在维持肩关节的稳定性中也起辅助作用[2]。在重建时,要想保持关节的静力和动力的微妙平衡关系是相当困难的,严重的软组织和骨质解剖改变使得在软组织松解和恢复关节方位时很难保持关节稳定性[3]。并发症包括感染、神经损伤、术中骨折、关节…     

Effects of the glenoid labrum and glenohumeral abduction on stability of the shoulder joint through concavity-compression : an in vitro study.

BACKGROUND: Although the glenohumeral joint is the most mobile articulation of the human body, it is known to exhibit ball-and-socket kinematics. Compression into the glenoid labral concavity keeps the humeral head centered. The purpose of the present study was to determine the effects of joint position on glenohumeral stability through concavity-compression. METHODS: Ten cadaveric shoulders were tested. The glenoid was mounted horizontally onto a six-component load-cell while the humerus was clamped to a vertically unconstrained slide. An x-y stage translated the load-cell with the glenoid underneath the humeral head in eight different directions. Compressive loads of 20, 40, and 60 N were applied. The tests were repeated in 0 degrees, 30 degrees, 60 degrees, and 90 degrees of glenohumeral abduction with and without the labrum. Relative translations between the glenoid and the humeral head and the forces resisting translation were recorded. Then the stability ratio, defined as the peak translational force divided by the applied compressive force, was calculated. RESULTS: The average stability ratio was higher in the hanging-arm position than it was in glenohumeral abduction. The highest stability ratio was detected in the inferior direction (59.8% 7.7%) when the labrum was intact and in the superior direction (53.3% 7.9%) when the labrum had been resected. Under both conditions, the anterior direction was associated with the lowest stability ratio (32.0% 4.4% with the labrum and 30.4% 4.1% without the labrum). Resection of the glenoid labrum resulted in an average decrease in the stability ratio of 9.6% 1.7%. With increasing compressive load, the average stability ratio slightly decreased. CONCLUSIONS: Glenohumeral stability through concavity-compression was greater in the hanging-arm position than it was in glenohumeral abduction. The average contribution of the labrum to glenohumeral stability through concavity-compression was approximately 10%, about one-half of the value previously reported. With the labrum intact, the glenohumeral joint was most stable in the inferior direction. Without the labrum, it was most stable in the superior direction. Under both conditions, it was least stable in the anterior direction. Glenohumeral joint stability through concavity-compression decreases with higher compressive loads.     

Influence of fall height and impact surface on biomechanics of feet-first free falls in children

OBJECTIVE: The objectives of our study were to assess biomechanics associated with feet-first free falls in 3-year-old children and to investigate the influence of impact surface type and fall height on key biomechanical measures associated with injury risk. METHODS: Repeatable feet-first free fall experiments were conducted in a laboratory mock-up environment using an instrumented Hybrid II 3-year-old test dummy. Impact surface type and fall height were varied to examine their influence on biomechanical measures. RESULTS: Feet-first falls from short distances (27 in.) (0.69 m) were found to have a low risk of contact-type head injury, regardless of impact surface type. When comparing different types of impact surfaces in a 27 in. (0.69 m) fall, head acceleration associated with falls onto playground foam was significantly less than that associated with falls onto wood, linoleum or padded carpet. For falls onto playground foam, femoral compressive loads and bending moments were found to significantly increase as fall height increased. CONCLUSIONS: Impact surface type and fall height were found to influence biomechanics associated with injury risk in feet-first free falls as assessed through experimental mock-ups using an instrumented child test dummy. Feet-first falls from short distances (27 in.) (0.69 m) were associated with a low risk of contact-type head injury as assessed using HIC, irrespective of impact surface type.     

肩关节外展过程中盂肱韧带长度变化的体内三维分析

下移的作用.外展60°时,中盂肱韧带稳定着盂肱关节的前方.外展120°时,下盂肱韧带前束发挥了主要的前方稳定作用.当外展至180°时,腋囊维持着盂肱关节前方的稳定,同时下盂肱韧带后束维持着下方的稳定.     

Influence of T-shift capsulorrhaphy on rotation and translation of the glenohumeral joint: An experimental study

To evaluate changes in the response of capsuloligamentous restraints to translatory forces and rotation torques caused by experimental capsulorrhaphy (T-shift modification of Bankart repair), eight cadaveric shoulders were tested. Measurements were taken in intact and vented specimens, after severance of the anterior capsule at the glenoid rim (creating an artificial Bankart lesion), T-shaped incision of the anterior capsule, and refixation of the capsule (with a standard Bankart procedure) combined with tightening by T-shift. Rotation torques and translatory forces were applied in different positions of abduction with a specifically designed mounting apparatus that had four degrees of freedom. Dynamic and static measurements were performed with a tracking sysem that had six degrees of freedom. T-shift capsulorrhaphy restored the resistance of the capsuloligamentous restraints to translatory forces in all directions. This restoration was confirmed when we compared these results with data obtained from intact joints. No significant alteration of the centering mechanism resulting from rotation torques was observed, although the extent of external and internal rotation was remarkably decreased. This T-shift modification seems to produce a symmetric reduction of the volume of the capsule without significant displacement of the humeral head.     

Anterior instability of the glenohumeral joint with humeral avulsion of the glenohumeral ligament. A review of 41 cases

We studied retrospectively a consecutive series of 547 shoulders in 529 patients undergoing operation for instability. In 41, the cause of instability was considered to be lateral avulsion of the capsule, including the inferior glenohumeral ligament, from the neck of the humerus, the HAGL lesion. In 35, the lesion was found at first exploration, whereas in six it was noted at revision of a previous failed procedure. In both groups, the patients were older on average than those with instability from other causes. Of the primary cases, in 33 (94.3%) the cause of the first dislocation was a violent injury; six (17.4%) had evidence of damage to the rotator cuff and/or the subscapularis. Only four (11.4%) had a Bankart lesion. In patients undergoing a primary operation in whom the cause of the first dislocation was a violent injury, who did not have a Bankart lesion and had no suggestion of multidirectional laxity, the incidence of HAGL was 39%.     

Translation of the humeral head on the glenoid with passive glenohumeral motion

We have demonstrated that certain passive motions of the glenohumeral joint are reproducibly accompanied by translation of the head of the humerus on the glenoid. We investigated the relationship of these translations to the position of the glenohumeral joint and to applied torques and forces in seven isolated glenohumeral joints from fresh cadavera, using a six-degrees-of-freedom position sensor and a six-axis force and torque transducer. Reproducible and significant translation occurred in an anterior direction with glenohumeral flexion and in a posterior direction with extension. We also observed translation with cross-body movement. The translation occurring with flexion was obligate in that it could not be prevented by the application of an oppositely directed force of thirty to forty newtons. Operative tightening of the posterior portion of the capsule increased the anterior translation on flexion and cross-body movement and caused it to occur earlier in the arc of motion compared with the intact glenohumeral joint. Operative tightening of the posterior part of the capsule also resulted in significant superior translation with flexion of the glenohumeral joint.     

Load-bearing capacity of the tibial component of the total condylar knee prosthesis. An in vitro study

The load-bearing capability of the tibial component of total knee prostheses is affected by the coverage of the osteotomized tibial surface by the tibial component. An anthropometric study of the proximal tibia indicated that standard total condylar tibial knee components may significantly underutilize the available weight-bearing tibial surface. The unloaded area values ranged from 6% to 43% in males and from 1% to 25% in females. An experimental study of the load-bearing capability of both standard tibial components and tibial components custom-fitted to conform to the periphery of the upper tibial surface was performed. Improvement in single load to failure with the conforming prosthesis averaged 29% in females with stemless prosthesis, 21% in females with stemmed prostheses, 41% in males with stemless prostheses, and 89% in males with stemmed prostheses. Post-test examination of the failed tibiae with conforming implants indicated failure by major fragmenting of the proximal tibia rather than cancellous bone crushing, suggesting that the maximal load-bearing ability of the upper tibial surface was more nearly being achieved. The results demonstrate the benefit to be gained by fully utilizing the available tibial surface for load transmission across the joint and suggest that use of custom-fitted tibial components has considerable merit.     

Lesions in different types of anterior glenohumeral joint dislocation. An experimental study

Three different kinds of anterior shoulder joint dislocation were studied in an experimental setup including 15 shoulder joint specimens. Lesion to the anterior-inferior part of the capsule was the most frequent finding in anterior dislocation. In anterior-superior dislocation lesions to the anterior-inferior part of the capsule and the posterior part of the cuff were equally prominent. Anterior-inferior dislocation was associated with lesions to all capsular structures including the glenohumeral ligament and both the anterior and posterior part of the cuff. From a clinical point of view, the study indicates that in some types of anterior dislocation a severe lesion of the posterior part of the capsule and cuff must also be considered.     

Recurrent disassembly of a modular humeral prosthesis. A case report.

A modular prosthesis for shoulder arthroplasty can be complicated by disassembly of the bearing surface from the humeral stem. Glenohumeral instability and increased humeral translation may be associated with this complication.     

The arterial vascularization of the humeral head. An anatomical study

In twenty-nine specimens from fresh cadavera, we performed an anatomical study of the arteries of the humeral head to determine their intraosseous distributions. A radiopaque suspension was injected into the anterior circumflex, posterior circumflex, suprascapular, thoracoacromial, or subscapular artery and then the specimens were dissected and were analyzed macroscopically, and radiographs were made in three mutually perpendicular projections. In addition, sixteen of the specimens were cut into four-millimeter slices and were studied microradiographically. The humeral head was shown to have been perfused by the anterolateral ascending branch of the anterior circumflex artery in all specimens. That vessel ran parallel to the lateral aspect of the tendon of the long head of the biceps and entered the humeral head where the proximal end of the intertubercular groove met the greater tuberosity. When the intraosseous (terminal) part of the anterolateral branch, the so-called arcuate artery, had been perfused, almost the entire epiphysis was radiopaque. The posterior circumflex artery vascularized only the posterior portion of the greater tuberosity and a small posteroinferior part of the head. Anastomoses between the different arteries were abundant, but vascularization of all of the humeral head was possible only through the anterolateral branch of the anterior circumflex artery.     

Influence of alkaline solutions on chemolitholysis and lithotripsy of uric acid stones. An in vitro study

OBJECTIVES: This study was performed to look for an improvement of therapeutic strategies with regard to the treatment of uric acid stones using artificial stones made of uric acid (BON(N)-STONES) which are comparable to their natural counterparts. MATERIALS AND METHODS: Using an experimental arrangement simulating the physiological conditions in the upper urinary tract the efficacy of different alkaline solutions and artificial urine in dissolving artificial uric acid stones (BON(N)-STONES) was investigated. The dissolution of natural uric acid stones was measured and investigations on shock wave lithotripsy (SWL) combined with initial chemolytic treatment of the stones were performed. RESULTS: The efficacy of alkaline solutions, especially THAM at a pH of 10, in dissolving artificial uric acid stones was demonstrated. The investigations on SWL showed a significant improvement on stone comminution of artificial uric acid stones after initial chemolytic treatment with THAM. CONCLUSIONS: New basics to improve dissolution of uric acid stones have been developed by performing standardized in vitro investigations. The suggestion was confirmed that stone fragility and thus SWL can be improved by varying the physical properties of uric acid stones through initial treatment with THAM solution.     

The normal glenohumeral relationships. An anatomical study of one hundred and forty shoulders.

We measured the dimensions of the humeral and glenoid articular surfaces in 140 shoulders that were representative of a given population of patients, and also evaluated several glenohumeral relationships. Ninety-six measurements were made in the shoulders of cadavera and forty-four, on magnetic resonance-imaging studies of living patients. Eighty-five per cent of the humeral measurements fell within eight fixed combinations of the radius of curvature and the thickness of the humeral head, in two-millimeter increments. The average radius of curvature of the humeral head in the coronal plane was 24 +/- 2.1 millimeters (range, nineteen to twenty-eight millimeters). The average thickness of the humeral head was 19 +/- 2.4 millimeters (range, fifteen to twenty-four millimeters). There was a wide variability in the size of the humeral head and a direct correlation between the differences in size and the heights in both men and women. The humeral articular surface was spherical in the center; however, the peripheral radius was two millimeters less in the axial plane than in the coronal plane. Thus, the peripheral contour of the articular surface was elliptical (ratio, 0.92). The radius of curvature of the glenoid, measured in the coronal plane, was an average of 2.3 +/- 0.2 millimeters greater than that of the humeral head. The average dimensions of the glenoid in the superior-inferior and anterior-posterior (lower half) directions were 39 +/- 3.5 millimeters (range, thirty to forty-eight millimeters) and 29 +/- 3.2 millimeters (range, twenty-one to thirty-five millimeters). The anterior-posterior dimension of the glenoid was pear-shaped, the lower half being larger than the top half. The ratio of the lower half to the top half was 1:0.80 +/- 0.01. There was a strong linear correlation between the lateral humeral offset and the size of the humeral head (radius of curvature and thickness). The average lateral humeral offset was 56 +/- 5.7 millimeters (range, forty-three to sixty-seven millimeters). The superior most point on the humeral articular surface was an average of 8 +/- 3.2 millimeters (range, three to twenty millimeters) cephalad to the top of the greater tuberosity. Our data show that reconstruction of the lateral humeral offset is important in optimization of the moment arm of the deltoid and rotator cuff and of the normal tension of the soft tissue after prosthetic reconstruction.     

An individualized approach for the implantation of a humeral prosthesis with the proper retroversion in fractures

We applied a new methodology in 7 patients with a fracture of the upper humeral head that required hemiarthroplasty, to implant a humeral prosthesis with an individualized posterior version. Our goal was to determine preoperatively the distance from the posterior edge of the bicipital groove where the lateral fin of the humeral prosthesis should sit, in order to reproduce the individual retroversion during surgery. Using three computed tomography scan sections of the upper humerus and image processing software, we estimated the above-mentioned distance in the sound humerus and implanted the prosthesis in each patient accordingly. The differences in retroversion between the left and right humeral heads permit a better approximation to normal applying this methodology than inserting the prosthesis in a standard retroversion. Received: 15 July 2000     

A new prosthesis for the metacarpophalangeal joint. Study of materials and biomechanics

This report discusses the Daphne prosthesis for the metacarpophalangeal joint on the basis of the mechanical, chemical and biological performance of the materials employed. The Daphne prosthesis is a mobile device. The main body is made of a new generation polymethylmetacrylate, while the hinge is made of AISI 316 L stainless steel. Biocompatibility tests were performed on the materials employed. Systemic toxicity, cytotoxicity and contact tests have given favourable results. Mechanical engineering tests have been used to investigate the performances and reliability of the selected materials. The polymethylmetacrylate used in Daphne behaves in a ductile fashion. No mechanical failures were encountered in fatigue tests after 10 million cycles.     

Conservative treatment, plate fixation, or prosthesis for proximal humeral fracture. A prospective randomized study

ABSTRACT: BACKGROUND: Proximal humerus fracture is the third most common fracture type after hip and distal radius fracture in elderly patients. A comprehensive study by Palvanen et al. demonstrated an increase in the annual fracture rate of 13.7% per year over the past 33 years. Should this trend continue, the fracture rate would triple over the next three decades. The increasing incidence of low-energy fractures raises questions about the optimal treatment in terms of functional outcome, pain, and rehabilitation time, as well as the economical impact. Despite the high incidence and costs of proximal humerus fractures, there is currently no valid scientific evidence for the best treatment method. Several publications, including a Cochrane review outline the need for high-quality, well-designed randomized controlled trials. METHODS: The study is a prospective, randomized, national multi-center trial. The hypothesis of the trial is that surgical treatment of displaced proximal humerus fractures achieves better functional outcome, pain relief, and patient satisfaction compared to conservative treatment. The trial is designed to compare conservative and surgical treatment of proximal humerus fractures in patients 60 years and older. The trial includes two strata. Stratum I compares surgical treatment with locking plates to conservative treatment for two-part fractures. Stratum II compares multi-fragmented fractures, including three- and four-part fractures. The aim of Stratum II is to compare conservative treatment, surgical treatment with the Philos locking plate, and hemiarthroplasty with an Epoca prosthesis. The primary outcome measure will be the Disabilities of the Arm, Shoulder and Hand (DASH) score and the secondary outcome measures will be the EuroQol-5D (EQ-5D) value, OSS, Constant-Murley Score, VAS, and 15D.Recruiting time will be 3 years. The results will be analyzed after the 2-year follow-up period. DISCUSSION: This publication presents a prospective, randomized, national multi-center trial. It gives details of patient flow, randomization, aftercare and also ways of analysis of the material and ways to present and publish the results.Trial registrationClinicalTrials.gov identifier: NCT01246167.