重建肘关节外翻稳定性的生物力学研究

目的　评价肘关节桡骨头 (radial head,RH)切除、尺侧副韧带 (medial collateral ligament,MCL )损伤以及 RH假体置换、MCL重建后的外翻稳定性。　方法　新鲜成人尸体上肢标本 12侧 ,制成肘关节“骨 -韧带”标本 ,在2 N· m的外翻力矩作用下 ,分别在肘关节 0°、30°、6 0°、90°和 12 0°伸屈时 ,测量肘关节外翻松弛度 :1完整肘关节(n=12 ) ;2 MCL切断 (n=6 ) ;3RH切除 (n=6 ) ;4 MCL切断 +RH切除 (n=12 ) ;5 RH假体置换 (n=6 ) ;6 MCL重建(n=6 ) ;7RH假体置换 +MCL重建 (n=12 )。用 SPSS 10 .0统计软件包作方差分析 ,比较各组的外翻稳定性。　结果　完整肘关节的平均外翻松弛度最小 ;RH切除后 ,外翻松弛度增大 ;单纯 MCL切断 ,外翻松弛度大于单纯 RH切除 (P<0 .0 1) ;MCL切断 +RH切除 ,外翻稳定性最差 ;行 RH假体置换 ,对稳定性有改善 ;MCL重建与完整 MCL差异无统计学意义 (P>0 .0 5 ) ;RH假体置换同时重建 MCL ,效果最好。　结论　 MCL是抵抗肘关节外翻应力最主要的因素 ,RH是次要因素。在重建肘关节的外翻稳定性方面 ,MCL的重建比 RH的假体置换更重要。在无条件行 RH假体置换时 ,修复MCL是较好的手术方式。     

Radial head fracture in the medial collateral ligament deficient elbow; biomechanical comparison of fixation, replacement and excision in human cadavers

A widely used clinical recommendation is that in the presence of medial collateral ligament injuries, two-part radial head fractures should be fixed rather than excising or replacing the radial head. Direct biomechanical data comparing fracture fixation, radial head replacement and excision in a human cadaveric elbow model, have not been previously described. Such comparison is clinically important as with the increasing availability of radial head implants and promising follow up results, the role of radial head replacement in fracture management may have to be redefined. In this study, five fresh cadaveric elbows had radial head fracture creation and medial collateral ligament division, fracture fixation, radial head replacement and excision. Valgus and varus laxity were determined using an electromagnetic tracking system. Radial head replacement leads to a similar valgus (P=0.80) [corrected] laxity as compared to radial head fixation. Radial head excision resulted in a significantly greater valgus laxity as compared to radial head fixation (P=0.02) or replacement (P=0.03). Both radial head excision and replacement led to a greater varus laxity as compared to fixation. Our results suggest that in the elbow with medial collateral ligament injury and two-part radial head fracture, fixation is overall biomechanically superior as compared to replacement and excision.     

Kinematics of partial and total ruptures of the medial collateral ligament of the elbow

In this study the kinematics of partial and total ruptures of the medial collateral ligament of the elbow are investigated. After selective transection of the medial collateral ligament of 8 osteoligamentous intact elbow preparations was performed, 3-dimensional measurements of angular displacement, increase in medial joint opening, and translation of the radial head were examined during application of relevant stress. Increase in joint opening was significant only after complete transection of the anterior part of the medial collateral ligament was performed. The joint opening was detected during valgus and internal rotatory stress only. After partial transection of the anterior bundle of the medial collateral ligament was performed, there was an elbow laxity to valgus and internal rotatory force, which became significant after transection of 100% of the anterior bundle of the medial collateral ligament and was maximum between 70 degrees to 90 degrees of flexion. No radial head movement was seen after partial or total transection of the anterior bundle of the medial collateral ligament was performed. In conclusion, this study indicates that valgus or internal rotatory elbow instability should be evaluated at 70 degrees to 90 degrees of flexion. Detection of partial ruptures in the anterior bundle of the medial collateral ligament based on medial joint opening and increased valgus movement is impossible.     

Contribution of monoblock and bipolar radial head prostheses to valgus stability of the elbow.

BACKGROUND: The purpose of this study was to evaluate the stabilizing effect of radial head replacement in cadaver elbows with a deficient medial collateral ligament. METHODS: Passive elbow flexion with the forearm in neutral rotation and in 80 degrees of pronation and supination was performed under valgus and varus loads (1) in intact elbows, (2) after a surgical approach (lateral epicondylar osteotomy of the distal part of the humerus), (3) after release of the anterior bundle of the medial collateral ligament, (4) after release of the anterior bundle of the medial collateral ligament and resection of the radial head, and (5) after subsequent replacement of the radial head with each of three different types of radial head prostheses (a Wright monoblock titanium implant, a KPS bipolar Vitallium [cobalt-chromium]-polyethylene implant, and a Judet bipolar Vitallium-polyethylene-Vitallium implant) in the same cadaver elbow. Total valgus elbow laxity was quantified with use of an electromagnetic tracking device. RESULTS: The mean valgus laxity changed significantly (p < 0.001) as a factor of constraint alteration. The greatest laxity was observed after release of the medial collateral ligament together with resection of the radial head (11.1 degrees +/- 5.6 degrees). Less laxity was seen following release of the medial collateral ligament alone (6.8 degrees +/- 3.4 degrees), and the least laxity was seen in the intact state (3.4 degrees +/- 1.6 degrees). Forearm rotation had a significant effect (p = 0.003) on valgus laxity throughout the range of flexion. The laxity was always greater in pronation than it was in neutral rotation or in supination. The mean valgus laxity values for the elbows with a deficient medial collateral ligament and an implant were significantly greater than those for the medial collateral ligament-deficient elbows before radial head resection (p < 0.05). The implants all performed similarly except in neutral forearm rotation, in which the elbow laxity associated with the Judet implant was significantly greater than that associated with the other two implants. CONCLUSIONS AND CLINICAL RELEVANCE: This study showed that a bipolar radial head prosthesis can be as effective as a solid monoblock prosthesis in restoring valgus stability in a medial collateral ligament-deficient elbow. However, none of the prostheses functioned as well as the native radial head, suggesting that open reduction and internal fixation to restore radial head anatomy is preferable to replacement when possible.     

Metallic radial head arthroplasty improves valgus stability of the elbow

The stabilizing influence of radial head arthroplasty was studied in eight medial collateral ligament deficient anatomic specimen elbows. An elbow testing apparatus, which used computer controlled pneumatic actuators to apply tendon loading, was used to simulate active elbow flexion. The motion pathways of the elbow were measured using an electromagnetic tracking device, with the forearm in supination and pronation. As a measure of stability, the maximum varus to valgus laxity over the range of elbow flexion was determined from the difference between varus and valgus gravity loaded motion pathways. After transection of the medial collateral ligament, the radial head was excised and replaced with either a silicone or one of three metallic radial head prostheses. Medial collateral ligament transection caused a significant increase in the maximum varus to valgus laxity to 18.0 degrees +/- 3.2 degrees. After radial head excision, this laxity increased to 35.6 degrees +/- 10.3 degrees. The silicone implant conferred no increase in elbow stability, with a maximum varus to valgus laxity of 32.5 degrees +/- 15.5 degrees. All three metallic implants improved the valgus stability of the medial collateral ligament deficient elbow, providing stability similar to the intact radial head. The use of silicone arthroplasty to replace the radial head in the medial collateral ligament deficient elbow must be questioned. Metallic radial head arthroplasty provides improved valgus stability, approaching that of an intact radial head.     

Valgus stability of the elbow. A definition of primary and secondary constraints

The stabilizing structures of the elbow that resist valgus stress were studied with a tracking device in a model simulating active motion and muscle activity. By varying the order of serial release of the medial collateral ligament complex and removal of the radial head, each structure's contribution to valgus stability against the effect of gravity was determined. In the otherwise intact elbow, absence of the radial head does not significantly alter the three-dimensional characteristics of motion in the elbow joint. Isolated medial collateral release, on the other hand, causes increases in abduction rotation of about 6 degrees-8 degrees in magnitude. Releasing both structures results in gross abduction laxity and elbow subluxation. This study defines the medial collateral ligament (MCL) as the primary constraint of the elbow joint to valgus stress and the radial head as a secondary constraint. This definition facilitates the proper management of patients with radial head fractures and MCL disruption. The comminuted radial head fracture uncomplicated by MCL insufficiency should be treated by excision without the need for an implant and without concern of altering the normal kinematics of the elbow.     

桡骨小头切除晚期并发症的原因及机制探讨

目的：研究桡骨小头切除后晚期并发症产生的原因、发病机制和预防措施。方法：对２８例桡骨小头切除术后进行２年以上随访。同时对２０例新鲜上肢标本进行生物力学检测。结果：发现桡骨小头切除术后的晚期并发症有肘外翻畸形、创伤性关节炎、桡尺远侧关节脱位等。肘关节内侧副韧带损伤、骨间膜撕裂伤和桡尺关节远侧脱位是桡骨小头切除术后引起或加重晚期并发症的主要原因。结论：桡骨小头切除时,应考虑上述三种组织损伤是否存在及对预后的影响;桡骨小头切除在青少年患者应视为禁忌     

Biomechanical evaluation of the elbow using roentgen stereophotogrammetric analysis

The medial collateral ligament complex is the primary constraint of the elbow to valgus forces and is composed of the anterior bundle, the posterior bundle, and a transverse part. Total and partial ruptures have been described. Clinical and radiologic examinations of medial or valgus instability of the elbow are difficult. The effect of different stages of medial collateral ligament ruptures on ulnohumeral movement in cadavers was determined to rationalize the use of physical and radiologic examinations in different stages of valgus instability in vivo. Using roentgen stereophotogrammetric analysis, motion is determined between the humerus and ulna under valgus load and between the humerus and radius during maximal pronation of the forearm after various dimensions of medial collateral ligament lesions. The increase in distance between the humerus and ulna under a 15 N valgus load varied from 2.7 mm to 9.8 mm. The increase in distance between the humerus and proximal radius with the forearm in pronation in an intact specimen and after transsection of the anterior medial collateral ligament and posterior medial collateral ligament in the anterior direction was 9.7 mm. These results suggest that detection of partial ruptures with clinical and radiologic examinations is difficult. Anterior movement of the radial head can be used as an additional parameter of valgus instability.     

Laxity of the elbow after experimental excision of the radial head and division of the medial collateral ligament. Efficacy of ligament repair and radial head prosthetic replacement: a cadaver study

We studied the stabilising effect of prosthetic replacement of the radial head and repair of the medial collateral ligament (MCL) after excision of the radial head and section of the MCL in five cadaver elbows. Division of the MCL increased valgus angulation (mean 3.9 +/- 1.5 degrees) and internal rotatory laxity (mean 5.3 +/- 2.0 degrees). Subsequent excision of the radial head allowed additional valgus (mean 11.1 +/- 7.3 degrees) and internal rotatory laxity (mean 5.7 +/- 3.9 degrees). Isolated replacement of the radial head reduced valgus laxity to the level before excision of the head, while internal rotatory laxity was still greater (2.8 +/- 2.1 degrees). Isolated repair of the MCL corrected internal rotatory laxity, but a slight increase in valgus laxity remained (mean 0.7 +/- 0.6 degrees). Combined replacement of the head and repair of the MCL restored stability completely. We conclude that the radial head is a constraint secondary to the MCL for both valgus displacement and internal rotation. Isolated repair of the ligament is superior to isolated prosthetic replacement and may be sufficient to restore valgus and internal rotatory stability after excision of the radial head in MCL-deficient elbows.     

Fractures of the capitellum

Forty intact cadaver elbows were studied to determine the contribution of the capitellum to elbow stability. With the elbow at 10 degrees of flexion, valgus motion of the elbow after capitellum excision demonstrated a minimal increase. Although some increase in valgus motion did occur after capitellum excision and radial head resection it was not until the ulnar collateral ligament was released that a severe valgus deformity was produced. In addition, isolated capitellum excisions occurring with release of the medial collateral ligament produced severe valgus motion, demonstrating the importance of medial structures to elbow stability. The cadaver study suggests excision of the capitellum in the otherwise intact elbow has little effect on valgus motion. Over the past 15 years, 17 patients with fractures of the capitellum were treated. Followup at greater than 1 year utilizing various treatment modalities is reported. Although closed reduction gave the best result, acceptable results were also obtained by open reduction and internal fixation and excision. Our clinical findings corroborated the cadaver findings in that valgus instability of the elbow only occurred when fracture of the capitellum was associated with medial ligament injuries.     

The effect of radial head fracture size on elbow kinematics and stability.

This study determined the effect of radial head fracture size and ligament injury on elbow kinematics. Eight cadaveric upper extremities were studied in an in vitro elbow simulator. Testing was performed with ligaments intact, with the medial collateral (MCL) or lateral collateral (LCL) ligament detached, and with both the MCL and LCL detached. Thirty degree wedges were sequentially removed from the anterolateral radial head up to 120 degrees . Valgus angulation and external rotation of the ulna relative to the humerus were determined for passive motion, active motion, and pivot shift testing with the arm in a vertical (dependent) orientation. Maximum varus-valgus laxity was calculated from measurements of varus and valgus angulation with the arm in horizontal gravity-loaded positions. No effect of increasing radial head fracture size was observed on valgus angulation during passive and active motion in the dependent position. In supination, external rotation increased with increasing fracture size during passive motion with LCL deficiency and both MCL and LCL deficiency. With intact ligaments, maximum varus-valgus laxity increased with increasing radial head fracture size. With ligament disruption, elbows were grossly unstable, and no effect of increasing radial head fracture size occurred. During pivot shift testing, performed with the ligaments intact, subtle instability was noted after resection of one-third of the radial head. In this in vitro biomechanical study, small subtle effects of radial head fracture size on elbow kinematics and stability were seen in both the ligament intact and ligament deficient elbows. These data suggest that fixation of displaced radial head fractures less than or equal to one-third of the articular diameter may have some biomechanical advantages; however, clinical correlation is required.     

桡骨头切除对肘关节稳定性影响的生物力学研究

目的：探讨桡骨头粉碎性骨折不同治疗方法对肘关节稳定性的影响。方法：将10个尸体标本，分别测定在其它组织无损伤时，肘内侧副韧带切断时，肘内侧副韧带和前臂骨间膜均切断时的力－位移曲线（纵向位移）及肘外翻角。结果：肘内侧副韧带切断时的纵向位移及肘外翻角均大于其它组织无损伤时；肘内侧副韧带和前臂骨间膜均切断时的纵向位移及肘外翻角均大于其它组织无损伤时和肘内侧副韧带切断时，两两间比较均有显著性差异（P＜0．001）。结论：在其它组织无损伤时，单纯桡骨头切除是安全的；合并肘内侧副韧带损伤时，可在有效修补韧带的同时作单纯头切除，必要时行假体置换；合并肘内侧副韧带和前臂骨间膜均损伤时，最好作假体置换。     

The Wrightington approach to the radial head: biomechanical comparison with the posterolateral approach

PURPOSE: The Wrightington approach to the radial head involves elevating anconeus from the proximal ulna to expose the supinator crest and then osteotomizing the bony insertion of the lateral ligament complex to the ulna. This avoids incising through the substance of the lateral ligament complex. The purpose of this study was to determine if there is any difference in laxity changes between using the posterolateral versus the Wrightington approach in performing surgery upon the radial head in a cadaveric model. METHODS: Ten cadaveric elbows had a radial head fracture created and the medial collateral ligament divided. They then sequentially had the posterolateral or Wrightington approach to the radial head, fracture fixation, head excision, and replacement. After each step, valgus and varus laxity and ulnar rotation were determined with an electromagnetic tracking system. RESULTS: After each step, there was a greater increase in valgus and varus laxity in the posterolateral group compared with the Wrightington group. After surgical exposure, radial head fracture fixation, and radial head excision, there was a statistically significant difference in the changes in rotation between the posterolateral and Wrightington approaches, with the former resulting in an increase in external and the latter an increase in internal rotation. CONCLUSIONS: These results suggest that the newly described Wrightington approach is biomechanically superior to the posterolateral approach with regard to changes in elbow laxity after surgery to the radial head.     

Functional anatomy of the ligaments of the elbow

Dissections of 10 fresh cadaver specimens revealed an important insertion of the posterior portion of the lateral collateral ligament to the ulna at the crista supinatoris. The humeral origin of the medial ligament attachments was found to lie posterior to the axis of elbow flexion; in this position a cam effect is created so that ligament tension varies with elbow flexion. The three-dimensional distance between the origin and the insertion of the anterior portion of the medial collateral ligament was found to increase slightly from extension to approximately 60 degrees of flexion; thereafter, it remained nearly constant. The distance of the posterior portion increased by about 9 mm from 60 degrees to 120 degrees of flexion. The flexion axis was shown to pass through the origin of the lateral collateral ligament, so the length of this structure was not changed during elbow flexion.     

Effects of elbow flexion and forearm rotation on valgus laxity of the elbow

BACKGROUND: Clinical evaluation of valgus elbow laxity is difficult. The optimum position of elbow flexion and forearm rotation with which to identify valgus laxity in a patient with an injury of the ulnar collateral ligament of the elbow has not been determined. The purpose of the present study was to determine the effect of forearm rotation and elbow flexion on valgus elbow laxity. METHODS: Twelve intact cadaveric upper extremities were studied with a custom elbow-testing device. Laxity was measured with the forearm in pronation, supination, and neutral rotation at 30 degrees, 50 degrees, and 70 degrees of elbow flexion with use of 2 Nm of valgus torque. Testing was conducted with the ulnar collateral ligament intact, with the joint vented, after cutting of the anterior half (six specimens) or posterior half (six specimens) of the anterior oblique ligament of the ulnar collateral ligament, and after complete sectioning of the anterior oblique ligament. Laxity was measured in degrees of valgus angulation in different positions of elbow flexion and forearm rotation. RESULTS: There were no significant differences in valgus laxity with respect to elbow flexion within each condition. Overall, for both groups of specimens (i.e., specimens in which the anterior or posterior half of the anterior oblique ligament was cut), neutral forearm rotation resulted in greater valgus laxity than pronation or supination did (p < 0.05). Transection of the anterior half of the anterior oblique ligament did not significantly increase valgus laxity; however, transection of the posterior half resulted in increased valgus laxity in some positions. Full transection of the anterior oblique ligament significantly increased valgus laxity in all positions (p < 0.05). CONCLUSIONS: The results of this in vitro cadaveric study demonstrated that forearm rotation had a significant effect on varus-valgus laxity. Laxity was always greatest in neutral forearm rotation throughout the ranges of elbow flexion and the various surgical conditions. CLINICAL RELEVANCE: The information obtained from the present study suggests that forearm rotation affects varus-valgus elbow laxity. Additional investigation is warranted to determine if forearm rotation should be considered in the evaluation and treatment of ulnar collateral ligament injuries of the elbow joint.     

Experimental elbow instability after transection of the medial collateral ligament

In 12 osteoligamentous autopsy elbow preparations, the stability of the elbow was independent of the collateral ligament with flexion of less than 20 degrees and greater than 120 degrees. The anterior part of the collateral medial ligament was the prime stabilizer of the elbow in this range of motion, i.e., the flexion range of function. The maximum valgus and internal rotatory instability after transection of the medial collateral ligament, 20.2 degrees and 21.0 degrees, respectively, were found at elbow flexions from 60 degrees to 70 degrees. Selective repair or reconstruction of the anterior part of the elbow medial collateral ligament may prove to be effective in the treatment of acute or chronic elbow instability.     

Instabilitätsrelevante Anatomie des Ellenbogens

Background

Detailed knowledge of elbow anatomy is crucial for diagnosis and therapy of instabilities around the elbow joint.

Discussion

Several anatomical structures stabilize the elbow joint. Due to its high congruency, the ulnohumeral joint protects the joint especially against varus as well as valgus stress and distraction particularly in full extension. The radiohumeral joint and proximal radioulnar joint are secondary stabilizers against valgus stress. The primary stabilizer against valgus stress is the medial collateral ligament which can be divided into an anterior and a posterior bundle. The lateral collateral ligament consists of the radial collateral ligament, the lateral ulnar collateral ligament and the annular ligament. The lateral collateral ligament in its entirety stabilizes the elbow against varus forces and posterolateral rotatory instability.

Conclusion

In addition, muscles spanning over the elbow joint are dynamic and static stabilizers via joint compression forces of the muscles and the orientation of muscle fibers that resemble those of the collateral ligaments.

     

Stability after medial collateral ligament release in total knee arthroplasty.

Six knees from cadavers were tested for change in stability after release of the medial collateral ligament with posterior cruciate-retaining and substituting total knee replacements. Load deformation curves of the joint were recorded in full extension and 30 degrees, 60 degrees, and 90 degrees flexion under a 10 N-m varus and valgus torque, 1.5 N-m internal and external rotational torque, and a 35 N anterior and posterior force to test stability in each knee. The intact specimen and posterior cruciate ligament-retaining total joint replacement were tested for baseline comparisons. The superficial medial collateral ligament was released, followed by release of the posterior cruciate ligament. The knee then was converted to a posterior-stabilized implant. After medial collateral ligament release, valgus laxity was statistically significantly greater at 30 degrees, 60 degrees, and 90 degrees flexion after posterior cruciate ligament sacrifice than it was when the posterior cruciate ligament was retained. The posterior-stabilizing post added little to varus and valgus stability. Small, but significant, differences were seen in internal and external rotation before and after posterior cruciate ligament sacrifice. The posterior-stabilized total knee arthroplasty was even more rotationally constrained in full extension than the knee with intact medial collateral ligament and posterior cruciate ligament.     

肘关节尺侧副韧带的修复重建

目的 评价桡骨头切除、尺侧副韧带(medial collateral ligament,MCL) 修复或重建手术治疗桡骨头粉碎性骨折合并MCL损伤的临床效果.方法 2000年9月-2006年4月,对18例桡骨头粉碎性骨折合并MCL损伤患者,手术行桡骨头切除的同时,对MCL采用直接缝合修复或带蒂筋膜重建治疗.其中男12例,女6例;年龄21～57岁.跌扑伤或高处坠落伤10例,交通事故伤8例.骨折按Mason分类,Ⅲ型13例,Ⅳ型5例.15例于伤后2周内手术;3例陈旧损伤,分别于伤后4、6和14个月手术.手术修复MCL4例,重建MCL14例. 结果 术后18例均获随访1～5年,平均3年.根据 Broberg 等制定的肘关节功能评定标准,优4例,良12例,可 1 例,差 1 例,优良率为 88.9%.3 例肘部轻度疼痛,1 例中度疼痛,14 例无疼痛.肘关节伸屈活动范围 110～140°,平均130°.前臂旋前 35～85°,平均 75°;前臂旋后 65～89°,平均 80°.患侧握力较健侧减少3%～28%,平均15%;伸肘力量减少8%～39%,平均30%;屈肘力量减少7%～29%,平均18%;旋前力量减少7%～31%,平均20%;旋后力量减少15%～45%,平均25%;患侧与健侧在相同外翻应力(外翻力矩2 Nm) 下X线片提携角增加 0～11°,平均 5°.以上指标患侧与健侧比较差异均有统计学意义(P<0.05). 结论 MCL 是抵抗肘关节外翻应力最主要的因素,在无条件行桡骨头假体置换时,行桡骨头切除、修复MCL 是一种有效的手术方式,但远期效果仍需随访.     

Elbow ligament strain under valgus load: a biomechanical study.

This study assessed the importance of the anterior and posterior bundles of the medial collateral ligament in the elbow by measuring in situ strain in response to valgus loads at three positions of forearm rotation throughout a full arc of motion. Strain in the anterior bundle was significantly greater than in the posterior bundle and increased with more flexion. The anterior bundle developed strain at a lower flexion angle (30 degrees) than the posterior bundle (60 degrees). Strain ratio increased with load increase for all flexion angles. Forearm position minimally affected strain. These results indicate that the anterior bundle is important in resisting a valgus load, particularly in mid-flexion, while the importance of the posterior bundle increases as the elbow approaches full flexion.