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.     

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.     

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

The valgus stabilizers of the elbow have been identified anatomically, but their relative importance has not been quantified. The purpose of this study was to analyze the acute changes of the torque-displacement curve to valgus stress following (a) section of the posterior portion of the medial collateral ligament; (b) excision of the radial head; (c) prosthetic replacement of the radial head; and (d) excision of the anterior portion of the medical collateral ligament. Thirty cadaver specimens underwent load-displacement testing in three positions: 0 degrees, 45 degrees, and 90 degrees of flexion. The anterior portion of the medial collateral ligament was the primary stabilizer of the elbow to valgus stress. The relative contribution of the posterior ligament was minimal. After excision of the radial head alone, the slope of the load-displacement curve decreased an average of 30%. Silicone rubber radial head replacement did not significantly improve the stability to valgus stress after radial head excision.     

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。     

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.     

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.     

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.     

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.     

The stability of the elbow following excision of the radial head and transection of the annular ligament. An experimental study

The stabilizing role of the lateral ligament complex and the radial head were investigated in ten osteoligamentous elbow preparations. The annular ligament was the prime stabilizer of the lateral aspect of the elbow. Transection of the annular ligament caused maximal varus and external rotatory instability of 13.7 degrees and 32.8 degrees respectively, with an elbow flexion about 70 degrees. Isolated excision of the radial head caused slight varus and external rotatory instability of 4.8 degrees and 10.4 degrees respectively, with an elbow flexion about 40 degrees. The lateral collateral ligament had only a minor stabilizing function of the elbow. The stability of the elbow after excision of the radial head may be improved by proper preservation of the annular ligament.     

肘关节内侧副韧带前束重建的生物力学研究

目的通过测量肘关节内侧副韧带(medial collateral ligament,MCL)前束生物力学指标,探讨前束完整及重建后对肘关节外翻稳定性的影响,评价采用人工肌腱、界面螺钉重建MCL前束疗效。方法成人完整上肢标本12具,男8具,女4具;左、右侧各6具;制成肘关节"骨-韧带"标本。采用生物力学及压敏胶片测量方法,分别测量MCL前束完整(对照组)及使用人工肌腱、界面螺钉重建后(实验组)肘关节屈曲0、30、60、90°时关节外翻松弛度、肱尺关节受力面积及肘关节内压强。结果两组在肘关节不同屈曲角度下,组内及组间关节松弛度比较,差异均无统计学意义(P>0.05)。除肘关节屈曲0°时两组肘关节压强小于其余屈曲角度(P<0.05),及对照组小于实验组(P<0.05)外,两组其余各角度组内及组间比较差异均无统计学意义(P>0.05)。除对照组内肘关节屈曲0°时肱尺关节受力面积大于其余屈曲角度(P<0.05)外,两组其余各角度组内及组间比较差异均无统计学意义(P>0.05)。结论 MCL前束对维持肘关节外翻稳定性具有重要意义,金属界面螺钉加人工肌腱重建后可即刻恢复内侧稳定。     

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.     

Release of the medial collateral ligament to improve flexion in post-traumatic elbow stiffness

Contracture of the collateral ligaments is considered to be an important factor in post-traumatic stiffness of the elbow. We reviewed the results of isolated release of the medial collateral ligament in a series of 14 patients with post-traumatic loss of elbow flexion treated between 1998 and 2002. There were nine women and five men with a mean age of 45 years (17 to 76). They were reviewed at a mean follow-up of 25 months (9 to 48). The operation was performed through a longitudinal posteromedial incision centred over the ulnar nerve. After decompression of the ulnar nerve, release of the medial collateral ligament was done sequentially starting with the posterior bundle and the transverse component of the ligament, with measurement of the arc of movement after each step. If full flexion was not achieved the posterior half of the anterior bundle of the medial collateral ligament was released. At the latest follow-up, the mean flexion of the elbow improved significantly from 96 degrees (85 degrees to 115 degrees ) pre-operatively to 130 degrees (110 degrees to 150 degrees ) at final follow-up (p = 0.001). The mean extension improved significantly from 43 degrees (5 degrees to 90 degrees ) pre-operatively to 22 degrees (5 degrees to 40 degrees ) at final follow-up (p = 0.003). There was a significant improvement in the functional outcome. The mean Broberg and Morrey score increased from a mean of 54 points (29.5 to 85) pre-operatively to 87 points (57 to 99) at final follow-up (p < 0.001). All the patients had normal elbow stability. Our results indicate that partial surgical release of the medial collateral ligament is associated with improved range of movement of the elbow in patients with post-traumatic stiffness, but was less effective in controlling pain.     

Dislocation of the elbow: an experimental study of the ligamentous injuries

The stability of human cadaveric elbow specimens was investigated using an experimental apparatus. Posterior dislocation of the elbow could only be produced when a combined valgus and external rotatory torque was applied to the specimen. None of the elbows were dislocated during varus and internal rotatory torque or in the extreme positions. In ten elbow specimens with an experimentally produced posterior dislocation, simultaneous rupture of the anterior part of the medial collateral ligament and the annular ligament were the most frequent findings. A lateral collateral ligament tear was only seen in two cases. Posterior elbow dislocation seems to be due to a combined valgus and external rotatory stress to the semiflexed elbow, resulting in a bilateral ligamentous injury.     

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.

     

A biomechanical study of stability of the elbow to valgus stress before and after reconstruction of the medial collateral ligament

The purpose of this study was to assess the stability of the elbow to valgus loads after reconstruction of the anterior bundle of the medial collateral ligament (MCL). The MCL in 14 human cadaveric elbows was exposed with a muscle-splitting approach. Each sample was secured in a materials test frame,5 N-m valgus moments were applied in 30 degrees, 60 degrees, 90 degrees, and 120 degrees of flexion, and baseline stability was measured. This sequence was performed after the anterior bundle was sectioned and again after ligamentous reconstruction was done with the Jobe technique. At 30 degrees, 60 degrees, 90 degrees, and 120 degrees of flexion, reconstruction reproduced an average of 99%, 102%, 97%, and 89%, respectively, of the stability of the intact ligament. The only significant difference between intact and reconstructed samples was at 120 degrees of flexion (P <.05). We concluded that this procedure reliably restores stability to a ruptured MCL throughout the flexion arc in the immediate postoperative period.     

Functional anatomy of the lateral collateral ligament complex of the elbow: configuration of Y and its role

A previous anatomic study has revealed that the lateral collateral ligament (LCL) complex of the elbow has a Y-shaped configuration, which consists of a superior, an anterior, and a posterior band. The LCL complex, including the annular ligament, functions as a 3-dimensional (3D) Y-shaped structure. On the basis of this concept, joint laxity after transection of the anterior band was studied in 5 normal, fresh-frozen cadaver elbows with a 3D kinematic testing apparatus. Cutting the anterior band produced significant laxity to varus torque with a mean 5.9 degree at 10 degree of elbow flexion and caused significant laxity to torque in external rotation with a mean 8.5 degree at 40 degree of flexion. No significant laxity was observed during application of valgus or internal rotational torque. Further transection of the posterior band resulted in gross instability with dislocation of the ulnohumeral joint. The laxity occurring after severance of the anterior band suggests that these fibers play a role in preservation of elbow stability against varus and external rotational torque. These results indicate that the LCL functions as a complex with a Y structure and not as an isolated linear ligament. A concept of conjoint point is hypothesized for the function of the LCL complex to restrain posterolateral rotatory instability.     

Kinematics of the ligamentous unstable elbow joint after application of a hinged external fixation device: a cadaveric study

We studied the kinematics of 8 ligamentous unstable elbow joint preparations after application of the Orthofix elbow external fixation device. Valgus, varus, external rotatory, and internal rotatory load tests were performed in lateral collateral ligament (LCL)-deficient and LCL/medial collateral ligament (MCL)-deficient joints. After placement of the fixator, the mean extension decreased significantly to 19.5 degrees +/- 7.2 degrees in the LCL-deficient joint and to 19.1 degrees +/- 6.6 degrees in the LCL/MCL-deficient joint compared with the mean extension of the intact joint, which was 10.5 degrees +/- 4.2 degrees. After application of the fixator, valgus displacement was significantly decreased by 4.0 degrees +/- 3.4 degrees in the LCL-deficient joint and by 3.6 degrees +/- 3.3 degrees in the LCL/MCL-deficient joint compared with the intact joint. External rotatory displacement was significantly decreased in the LCL-deficient joint by 4.9 degrees +/- 3.7 degrees and in the LCL/MCL-deficient joint by 5.0 degrees +/- 4.7 degrees. Internal rotatory displacement was significantly decreased by 3.3 degrees +/- 2.7 degrees in the LCL-deficient joint, but it was not significantly changed in the LCL/MCL-deficient joint. The Orthofix elbow external fixator guided elbow motion to a more varus position compared with the intact elbow and decreased the range of motion of the joint, constraining mainly extension. We conclude that the fixator stabilized the ligamentous unstable elbow joint efficiently but at the expense of changes in the normal motion pattern.     

Anatomic and histologic studies of lateral collateral ligament complex of the elbow joint

We studied the gross and histologic anatomic characteristics of the lateral collateral ligament complex of the elbow joint from 15 cadavers to demonstrate its cross-sectional anatomy. The lateral ulnar collateral ligament adheres closely to the supinator, the extensor muscles, its intermuscular fascia, and the anconeus muscle and lies posterior to the radial collateral ligament. The lateral ulnar collateral ligament itself was identified with microscopy as a slender, poor structure consisting of the thick area of the posterolateral capsuloligamentous layer and a poorer structure than the anterior bundle of the medial collateral ligament as the primary stabilizer of the elbow joint. We believe that the lateral ulnar collateral ligament contributes to rather than is a major constraint to the posterolateral rotatory instability as part of the lateral collateral ligament complex with the surrounding tissues.