The stability of the elbow following excision of the radial head and transection of the annular ligament

Summary 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° and 32.8° respectively, with an elbow flexion about 70°. Isolated excision of the radial head caused slight varus and external rotatory instability of 4.8° and 10.4° respectively, with an elbow flexion about 40°. 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.     

Elbow joint laxity after experimental radial head excision and lateral collateral ligament rupture: efficacy of prosthetic replacement and ligament repair

The objectives of this experimental study were to investigate the effect of radial head excision and lateral collateral ligament (LCL) division on elbow joint laxity and to determine the efficacy of radial head prosthetic replacement and LCL repair. Valgus, varus, internal rotation, and external rotation of the ulna were measured during passive flexion-extension and application of a 0.75-Nm torque in 6 intact cadaveric elbows and after (1) either excision of the radial head or division of the LCL, (2) removal of both constraints, (3) isolated radial head prosthetic replacement, (4) isolated LCL repair, and (5) radial head replacement combined with LCL repair. Isolated radial head excision increased varus (mean, 4.8 degrees) and external rotatory laxity (mean, 7.1 degrees), as did isolated LCL division (mean, 14.1 degrees for varus; mean, 14.7 degrees for external rotation). After removal of both constraints, varus and external rotatory laxities were increased by 19.0 degrees and 20.1 degrees, respectively, compared with the intact specimens. Isolated radial head replacement reduced mean varus laxity to 14.6 degrees and mean external rotatory laxity to 14.8 degrees. Isolated LCL repair normalized varus laxity but resulted in a 2.9 degrees increase in external rotatory laxity. The combined procedures restored laxity completely. The radial head is a constraint to varus and external rotation in the elbow joint, functioning by maintaining tension in the LCL. Still, removal of both constraints induces severe laxity, and in this case, prosthetic replacement may substitute for the constraining capacity of the native radial head. The combination of LCL repair and radial head replacement restores laxity completely, but an isolated LCL repair performs almost as well, probably by compensating for the ligamentous tension lost from radial head excision.     

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.     

Ligamentous stabilizers against posterolateral rotatory instability of the elbow.

BACKGROUND: The lateral ulnar collateral ligament, the entire lateral collateral ligament complex, and the overlying extensor muscles have all been suggested as key stabilizers against posterolateral rotatory instability of the elbow. The purpose of this investigation was to determine whether either an intact radial collateral ligament alone or an intact lateral ulnar collateral ligament alone is sufficient to prevent posterolateral rotatory instability when the annular ligament is intact. METHODS: Sequential sectioning of the radial collateral and lateral ulnar collateral ligaments was performed in twelve fresh-frozen cadaveric upper extremities. At each stage of the sectioning protocol, a pivot shift test was performed with the arm in a vertical position. Passive elbow flexion was performed with the forearm maintained in either pronation or supination and the arm in the varus and valgus gravity-loaded orientations. An electromagnetic tracking device was used to quantify the internal-external rotation and varus-valgus angulation of the ulna with respect to the humerus. RESULTS: Compared with the intact elbow, no differences in the magnitude of internal-external rotation or maximum varus-valgus laxity of the ulna were detected with only the radial collateral or lateral ulnar collateral ligament intact (p > 0.05). However, once the entire lateral collateral ligament was transected, significant increases in internal-external rotation (p = 0.0007) and maximum varus-valgus laxity (p < 0.0001) were measured. None of the pivot shift tests had a clinically positive result until the entire lateral collateral ligament was sectioned. CONCLUSIONS: This study suggests that, when the annular ligament is intact, either the radial collateral ligament or the lateral ulnar collateral ligament can be transected without inducing posterolateral rotatory instability of the elbow.     

Elbow joint kinematics after excision of the radial head.

The contribution of the radial head to elbow joint kinematics was studied in 7 osteoligamentous elbow preparations. During unloaded flexion and extension, radial head excision induced a maximum varus displacement of 1.6 degrees with 20 degrees of joint flexion and a maximum external rotation of 3.2 degrees at 110 degrees of flexion. With application of a 0.75-Nm load, radial head excision induced a maximum laxity of 3.3 degrees at 20 degrees of flexion in forced varus and a maximum laxity of 8.9 degrees at 10 degrees of flexion in forced external rotation. No laxity was observed in forced valgus or internal rotation. The results were independent of the rotation of the forearm. This study indicates that the radial head acts as stabilizer to the elbow joint in forced varus and in forced external rotation. The results suggest that fractures of the radial head cannot be treated by simple excision without altering the basic kinematics of the elbow joint.     

Posterolateral rotatory instability of the elbow

Posterolateral rotatory instability of the elbow is a three-dimensional displacement pattern of abnormal external rotatory subluxation of the ulna coupled with valgus displacement on the humeral trochlea. This pattern causes the forearm bones to displace into external rotation and valgus during flexion of the elbow. Injury to the lateral ulnar collateral ligament allows abnormal supination of the ulna on the humerus. The radial head, being locked in the sigmoid (radial) notch of the proximal ulna by the annular ligament, subluxates posterior to the capitellum. The abnormality is usually posttraumatic and presents with locking, snapping, clicking, catching, and recurrent dislocation of the elbow. The clinical diagnosis is suspected from history and confirmed by the physical examination, which includes the posterolateral rotatory instability test. This test often is best performed under fluoroscopy or general anesthesia. Usually the instability is managed with either a repair of the ligament or an isometric reconstruction using a tendon graft.     

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.     

Tardy posterolateral rotatory instability of the elbow due to cubitus varus

BACKGROUND: Cubitus varus has long been considered merely a cosmetic deformity. The purpose of this paper is to demonstrate a causal relationship between cubitus varus and instability of the elbow. METHODS: In twenty-four patients (twenty-five limbs) with a cubitus varus deformity following a pediatric distal humeral fracture or resulting from a congenital anomaly (three limbs of two patients), tardy posterolateral rotatory instability of the elbow developed approximately two to three decades after the deformity occurred. All patients presented with lateral elbow pain and recurrent instability. The average varus deformity was 15 degrees (range, 0 degrees to 35 degrees ). Surgery was performed in twenty-one patients (twenty-two limbs). Treatment consisted of reconstruction of the lateral collateral ligament and osteotomy in seven limbs, ligament reconstruction alone in ten, osteotomy alone in four, and total elbow arthroplasty in one. RESULTS: In three patients, the triceps muscle was dynamically stimulated intraoperatively to contract while resisting extension of the elbow. This produced posterolateral rotatory subluxation of the elbow, which was reversed by corrective osteotomy and lateral transposition of a portion of the medial head of the triceps that originally had been attached to the elongated, deformed medial aspect of the olecranon. At an average of three years (minimum, one year) after the operation, the result was good or excellent for nineteen of the twenty-two limbs that had undergone an operation; three limbs had persistent instability. CONCLUSIONS: With cubitus varus, the mechanical axis, the olecranon, and the triceps line of pull are all displaced medially. The repetitive external rotation torque on the ulna permitted by these deformities can stretch the lateral collateral ligament complex and lead to posterolateral rotatory instability. Thus, cubitus varus deformity secondary to supracondylar malunion or congenital deformity of the distal part of the humerus may not always be a benign condition and may have important long-term clinical implications. Operative correction can relieve symptoms of instability. The indications for preventive corrective osteotomy remain to be determined.     

Muscle forces and pronation stabilize the lateral ligament deficient elbow.

The influence of muscle activity and forearm position on the stability of the lateral collateral ligament deficient elbow was investigated in vitro, using a custom testing apparatus to simulate active and passive elbow flexion. Rotation of the ulna relative to the humerus was measured before and after sectioning of the joint capsule, and the radial and lateral ulnar collateral ligaments from the lateral epicondyle. Gross instability was present after lateral collateral ligament transection during passive elbow flexion with the arm in the varus orientation. In the vertical orientation during passive elbow flexion, stability of the lateral collateral ligament deficient elbow was similar to the intact elbow with the forearm held in pronation, but not similar to the intact elbow when maintained in supination. This instability with the forearm supinated was reduced significantly when simulated active flexion was done. The stabilizing effect of muscle activity suggests physical therapy of the lateral collateral ligament deficient elbow should focus on active rather than passive mobilization, while avoiding shoulder abduction to minimize varus elbow stress. Passive mobilization should be done with the forearm maintained in pronation.     

Elbow instability

An understanding of elbow instability is predicated on knowledge of the anatomy of the lateral collateral ligament complex and of the mechanism and kinematics of elbow subluxation and dislocation. The lateral collateral ligament complex is the key structure involved in recurrent elbow instability and it is virtually always disrupted in elbow dislocations that result from a fall. The ulnar part of the lateral collateral ligament complex (also known as lateral ulnar collateral ligament) is the critical portion of the ligament complex securing the ulna to the humerus and preventing posterolateral rotatory instability. The kinematics of elbow subluxation and dislocation are a three dimensional coupled motion referred to as posterolateral rotatory instability in which the forearm rotates off the humerus in valgus/external rotation during flexion from the extended position. Elbow instability is diagnosed on clinical examination by the lateral pivot-shift test, the posterolateral rotatory apprehension and drawer tests and on radiographic examination by performing stress x-rays. While the lateral pivot-shift test is difficult to perform, the posterolateral rotatory drawer test is much less difficult. The most sensitive test, however, is the posterolateral rotatory apprehension test. A positive apprehension test in a patient presenting with a history of recurrent painful clicking, snapping, clucking, or locking of the elbow should lead one directly to the suspected diagnosis of posterolateral rotatory instability. Treatment is surgical, by repair or reconstruction of the lateral collateral ligament complex, specifically the ulnar part. Deficiencies of the coronoid and/or radial head must be addressed.     

Posterolateral rotatory instability of the elbow following radial head resection

BACKGROUND: Resection is a common procedure for the treatment of comminuted fractures of the radial head. While radial head resection is associated with a high success rate when performed for appropriate indications, a number of well-defined biomechanical complications have been reported following this procedure, including proximal migration of the radius, the development of valgus deformity, and recurrent elbow instability in the acute setting. However, posterolateral rotatory instability has not previously been recognized as a complication of radial head resection. While the absence of the radial head makes the diagnosis difficult, we have identified a series of patients with posterolateral rotatory instability following radial head resection. We believe that this instability is secondary to unrecognized lateral ulnar collateral ligament deficiency. METHODS: Between November 1995 and September 2000, forty-two patients were evaluated because of elbow or forearm complaints following radial head resection. Seven patients (17%) were diagnosed with posterolateral rotatory instability on the basis of characteristic clinical and radiographic findings. RESULTS: The study group included five men and two women with a mean age of forty-two years. All seven patients had had radial head excision for the treatment of a comminuted radial head fracture at a mean of forty-four months (range, four months to sixteen years) prior to referral. All seven patients had lateral elbow pain, a sense of instability and/or weakness, and a positive lateral pivot-shift test. Posterolateral rotatory instability secondary to lateral ulnar collateral ligament insufficiency was confirmed intraoperatively in the four patients who were managed surgically. CONCLUSIONS: Clinicians should be aware that posterolateral rotatory instability may be a cause of unexplained elbow pain and instability following radial head resection. This diagnosis has implications for the prevention and treatment of this condition.     

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.     

Elbow joint instability: A kinematic model

The effect of simultaneous ulnar and radial collateral ligament division on the kinematics of the elbow joint is studied in a cadaveric model. Severance of the anterior part of the ulnar collateral ligament and the annular ligament led to significant elbow joint instability in valgus and varus stress and in forced external and internal rotation. The mean maximum laxity in valgus stress and forced external rotation were 5.7° and 13.2°. The forearms of the elbow joint specimens were transfixed in maximum pronation. During valgus and varus stress the corresponding spontaneous ulnar rotation of the specimens was recorded. The reproducibility of the instability pattern suggests that this model is suitable for evaluating stabilizing procedures aimed at correction of elbow joint instability before these procedures are introduced into patient care.     

The in vivo isometric point of the lateral ligament of the elbow

BACKGROUND: Many reports have discussed reconstruction of the lateral ulnar collateral ligament for the treatment of posterolateral rotatory instability of the elbow, but information regarding the isometric point of the lateral ligament of the elbow is limited. The purposes of the present study were to investigate the in vivo and three-dimensional length changes of the lateral ulnar collateral ligament and the radial collateral ligament during elbow flexion in order to clarify the role of these ligaments as well as to identify the isometric point for the reconstructed lateral ulnar collateral ligament on the humerus where the grafted tendon should be anchored. METHODS: We studied in vivo and three-dimensional kinematics of the normal elbow joint with use of a markerless bone-registration technique. Magnetic resonance images of the right elbows of seven healthy volunteers were acquired in six positions between 0 degrees and 135 degrees of flexion. We created three-dimensional models of the elbow bones, the lateral ulnar collateral ligament, and the radial collateral ligament. The ligament models were based on the shortest calculated paths between each origin and insertion in three-dimensional space with the bone as obstacles. We calculated two types of three-dimensional distances for the ligament paths with each flexion position: (1) between the center of the capitellum and the distal insertions of the ligaments (to investigate the physiological change in ligament length) and (2) between eight different humeral origins and the one typical insertion of the lateral ulnar collateral ligament (to identify the isometric point of the reconstructed lateral ulnar collateral ligament). RESULTS: The three-dimensional distance for the lateral ulnar collateral ligament was found to increase during elbow flexion, whereas that for the radial collateral ligament changed little. The path of the lateral ulnar collateral ligament gradually developed a detour because of the osseous protrusion of the lateral condyle with flexion. The most isometric point for the reconstructed lateral ulnar collateral ligament was calculated to be at a point 2 mm proximal to the center of the capitellum. CONCLUSIONS: The radial collateral ligament is essentially isometric, but the lateral ulnar collateral ligament is not. The lateral ulnar collateral ligament is loose in elbow extension and becomes tight with elbow flexion.     

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.     

Repairing the annular ligament is not necessary in the operation of Mason type 2, 3 isolated radial head fractures if the lateral collateral ligament is intact: Minimum 5 years follow-up

Introduction

The repair of annular ligament after open reduction and internal fixation of radial head fracture could produce the irritation or crepitation during range of motion exercise. The purpose of this study is to evaluate the significance of unrepaired annular ligament during fixation of isolated radial head fractures.

Materials and methods

Retrospectively we reviewed the twenty-five patients who underwent surgical fixation with a plate for Mason type 2, 3 isolated radial head fracture without annular ligament repair. All the radial head fracture did not have the associated injuries which could cause the elbow instabilities. The average length of follow-up was 6.9 years. The outcomes were evaluated clinically (range of motions, instabilities, pain VAS, Broberg & Murrey functional rating score, DASH score) and radiographically (bony union, arthritic change, lateral translation of the radial head, humero-ulnar angle with maximum varus stress of elbow, ulnar variance).

Results

The range of motions between affected and contralateral side were not significantly different at last follow-up. No one showed the instabilities of elbow. The mean pain VAS, Broberg & Murrey functional rating score, and DASH score were 2.7 ± 0.5, 95.3 ± 2.5, and 14.8 ± 5.3 points respectively. Bony union was observed for all cases. There was no significant difference in the lateral translation of the radial head, humero-ulnar angle with maximum varus stress of elbow, and ulnar variance between the affected and the contralateral arm.

Conclusion

The isolated role of the annular ligament seems overestimated. We scrutinize that the annular ligament repair is not essential in the operative treatment of isolated radial head fractures if the lateral collateral ligament is intact.     

Importance of a radial head component in Sorbie unlinked total elbow arthroplasty

The effects of a radial head component on total elbow arthroplasty kinematics and stability were evaluated using an anatomic design unlinked total elbow prosthesis. An electromagnetic tracking device recorded motion and varus and valgus displacements under various conditions in 10 cadaveric elbows. The motion patterns of the intact elbows and the Sorbie-Questor total elbow prostheses with a radial head component were similar, as both tended to have a valgus position in extension, varus at midflexion, and more valgus toward full flexion. Under conditions of simulated muscle loading, the maximum valgus and varus laxity of the elbow prosthesis was, on average, 8.6 degrees +/- 4.0 degrees greater than normal. Without the radial head component, however, significant kinematic disturbances and instabilities were seen. The varus and valgus displacements were 13.3 degrees +/- 5.5 degrees greater than the intact elbows. One total elbow arthroplasty without a radial head dislocated during testing. Increasing the muscle loading across the elbow significantly enhanced dynamic stability of the total elbow arthroplasties, especially in the extension half of elbow motion where instability is greatest. However, this dynamic enhancement of stability was seen only in those elbows in which the radial head component had been implanted. The radial head component is an important stabilizer, particularly in extension for this prosthesis, and possibly for other unlinked total elbow prostheses. Although instability of unlinked prostheses depends on the prosthetic design, the use of a radial head replacement may be an important factor in preventing such instability. Perhaps even more importantly, a radial head component balances the load distribution across the articulation, which could decrease stress on the ulnohumeral articulation and therefore possibly reduce polyethylene wear, osteolysis, and loosening.     

Effectiveness of the lateral unilateral dynamic external fixator after elbow ligament injury

BACKGROUND: The optimum management of ligamentous injuries of the elbow is not known. Use of dynamic external fixators has been advocated to stabilize the joint while maintaining motion, but there are no published data to corroborate their efficacy. The purpose of this study was to test the hypothesis that a laterally applied unilateral dynamic external fixator is capable of stabilizing and restoring normal kinematics to elbows with varying degrees of soft-tissue injury. METHODS: Six fresh-frozen cadaveric upper extremities, from donors who were an average of seventy-six years of age at the time of death, were tested in a custom apparatus with an electromagnetic tracking device to analyze the kinematic behavior. Testing began with an injury of either the lateral or the medial collateral ligament, which was followed by a second test with an injury to the ligament on the contralateral side of the joint. In each test, the varus-valgus displacement and the forearm rotatory displacement were measured through the arc of elbow flexion under three loading conditions (hand weight alone, hand weight plus 3.5 N, and hand weight plus 7 N). After each test (with each injury), a unilateral external fixator was applied from the lateral aspect of the elbow, and the same measurements were conducted under the three loading conditions across the elbow joint. RESULTS: With varus stress testing, both after injury of the medial collateral ligament alone and after injury of the lateral collateral ligament and extensor mass alone, the laterally applied unilateral dynamic external fixator was capable of maintaining the displacements within the laxity envelope of an uninjured elbow. With valgus stress testing, after either lateral or medial ligamentous injury, the fixator was unable to maintain displacements within the normal laxity envelope when a 7-N load was applied to the elbow. When both medial and lateral injuries were present, the lateral fixator maintained varus displacement within normal limits, but valgus displacement was consistently maintained within normal limits only when no additional load was applied to the forearm. CONCLUSIONS: A lateral dynamic elbow external fixator is capable of maintaining varus displacements within normal limits in the presence of medial and lateral collateral ligament injuries and with a 7-N load added to the limb. However, valgus displacement is only consistently maintained within normal limits if no additional displacement force is added to the weight of the hand and forearm. The maintenance of valgus displacement is more sensitive to additional load and specifically to the extent of medial soft-tissue injury.     

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.     

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.