切开复位内固定治疗移位的桡骨头骨折

【摘要】  ［目的］探讨切开复位内固定治疗成人移位桡骨头骨折的手术技术。［方法］本组移位桡骨头骨折26例，Mason Ⅱ型16例，Ⅲ型6例，Ⅳ型4例。22例用肘后外侧Kocher切口，另外4例用肘后正中切口以便同时处理合并的尺骨近端骨折。复位后用微型钢板螺钉固定，并使内固定物不妨碍关节活动。［结果］随访平均32月，无骨间后神经损伤及感染发生，26例骨折均顺利愈合。按照Broberg和Morrey肘部评分标准，优17例，良9例。［结论］切开复位内固定治疗移位桡骨头骨折可取得满意疗效，术中应注意以下方面：（1）保护、修复尺骨外侧副韧带；（2）防止损伤骨间后神经；（3）努力达到解剖复位；（4）固定既要坚强可靠，又要不阻碍关节的运动。

【关键词】  桡骨头； 骨折； 内固定

    Correspondence:WANG Hong-chuan,M.D.Tel:022-28336412，

    E-mail:hongchuanwang@hotmail.com.cnFractures of the radial head are relatively common fractures, accounting for 33% of elbow fractures in adults［1］.  Although radial head resection once was widely practiced, radial head resection is associated with delayed complications, such as pain and decreased strength of injuried eclow［2］. This follow-up observation of 26 patients demonstrated satisfying restoration of elbow function, who underwent internal fixation of displaced radial head fractures from January 2003 and June 2005. The purpose of this article is to explore the surgical techniques of open reduction and internal fixation of displaced radial head fractures in adults.

    Materials and Methods

    Patients

    Twenty-six displaced radial head fractures were all closed fractures. There were sixteen male patients and ten female patients with an average age of thirty-eight years (range, seventeen to fifty-six years). Fourteen injuries were the result of a fall from a highter stair or during sports activity, or a bicycle accident; seven, a motor-vehicle accident; five, a fall from a standing ground.According to the Mason classification system［1］, sixteen patients had a Type-II fracture, six patients Type-III fracture, four patients Type-IV fracture. Injuries of the ipsilateral upper extremity were as follows: four radial head fractures were associated with proximal ulna fracture, three were associated with fracture of the coronoid, one was associated with fracture of the humeral medial epicondyle, eight were associated with rupture of the medial collateral ligament. In addition, lesions of the cartilage of the humeral capitellum were identified in two cases during operations. The mean time from the injury to surgery were 4.2 days (range, two to seven days).

    Operative Technique

    A standard posterolateral Kocher approach was used in twenty-two cases, and a midline posterior skin incision were used in other four cases in order to address both the radial head fractures and the associated proximal ulna fractures in one incision. The interval between anconeus and extensor carpi ulnaris was identified and divided to expose the underlying radiohumeral joint capsule. The capsule was incised anterior to the lateral ulnar collateral ligament, and fracture of the radial head was exposed. The articular surface was reduced under direct visualization and held temporarily with 1mm K-wires. For the radial head with a partial articular fracture, definitive fixation was achieved using either 1.5- or 2.0-mm mini-fragment screws. For nine cases whose fractures extended into the radial neck, mini-fragment L- or T-shaped plates （AAP company, Germany）were applied to provide excellent fixation. The mini-fragment plates were carefully contoured and placed in the safe zone so as not to interfere with the proximal radioulnar joint in pronation or supination. During operation of reduction and fixation, pronating and supinating forearm may make it convenient to perform reduction and fixation of radial head fractures. In three patients, bone graft from the lateral epicondyle were used to fill defects in the area of the neck. After completing fixation, the forearm was taken through a full pronation and supination to ensure any implants not to  impinge on the proximal radioulnar joint. The ruptured lateral collateral ligament were repaired in three patients. The incision of the joint capsule was repaired at the time of closure, but the sutured capsule shouldn't be so overlapped and tight as to limit full pronation and supination of forearm. Four of the ulnar fractures and three of coronoid fractures were also reduced and fixed. For one patient whose elbow continued to be unstable after bony fixation and ligament repair, a hinged external fixator (Orthofix, Italy) was applied.

    Postoperative Management

    After operation, place the elbow in a well-padded posterior splint in 90° flexion.One day after surgery, active range of motion typically began with gentle elbow and forearm motion. Two weeks after surgery, the immobilization was discontinued, and active mobilization exercises were initiated. For Mason type III and IV radial head fractures, the upper limb was placed in a hinged orthosis for 4 to 6 weeks after surgery, which may limit the range of motion to the safe zone initially and advance the range over a few weeks.

    Results

    The twenty-six patients were followed-up for an average of thirty-two months (range, twenty-four to fifty-four months). There was no case with the posterior interosseous nerve injury or wound infection after surgery. At 13 weeks (range, ten to sixteen weeks), the fractures healed radiographically with no failure of fixation or collapse of the radial head. Nine patients with plate fixation and four patients with screws fixation alone had implants removed after six to eleven months. According to the system of Broberg and Morrey1, the average score was 95 points (range, 82 to 100 points), and the result were rated as excellent in seventeen patients, good in nine(Fig1、2).

    Fig.1  Preoperative radiographs demonstrating comminuted fracture of the radial head  Fig.2  Anteroposterior (a) and lateral (b) radiographs of the elbow at 3-month follow-up demonstrated healing of the fracture

    Discussion

    Displaced radial head fractures are often associated with other injuries of the elbow. van Riet  reported that 71 (64.5%) of 110 displaced radial head fractures had concomitant elbow lesions, including coronoid fracture, elbow dislocation, medial collateral ligament injuries and so on［3］.  As recent biomechanics studies have demonstrated, the radial head resists both valgus forces at the elbow and longitudinal forces transmitted along the forearm. The radial head becomes a more important stabilizer when the medial collateral ligament rupture or other elbow injuries occur［4］.  Long-term follow-ups after radial head excision have often revealed poor results of the elbow or wrist, including pain, joint instability, proximal radial translation, decreased strength, osteoarthrosis, and cubitus valgus［5］.  These delayed complications also reflect the important effect of the radial head on elbow stability. As a result, indications for excision of the radial head are becoming more limited, and internal fixation of displaced radial head fractures is now more widely practiced. As a recent study showed, open reduction and internal fixation of displaced radial head fracture can obtain more satisfactory elbow motion, greater muscle strength and better joint function than radial head resection［6］.  This clinic results also suggest that internal fixation of displaced radial head fractures can lead to successful results.

    The lateral ulnar collateral ligament originates from the center of the lateral epicondyle, and inserts at the tubercle of the supinator crest of the proximal ulna. It is the ulnar part of the lateral ligament complex of the elbow. Because recent studies suggest it is the most important in preventing posterolateral rotatory instability of the elbow, it is referred to as the lateral ulnar collateral ligament (LUCL) to highlight its function［7］.When exposing of the radial head, it is important to incise the capsule anterior to the lateral ulnar collateral ligament in order to preserve LUCL. To gain better visualization, the anterior capsular flap may be released from the epicondyle, but the posterior capsular flap including LUCL should not be released. When rupture of LUCL is identified, it should be carefully repaired after bony fixation in order to maintain joint stability(Fig.3).

    The posterior interosseous nerve (PIN) passes over the front of the anterolateral portion of the radiohumeral joint capsule and then enters the supinator muscle continuing to run dorsolaterally, so it is prone to injury during operation. Care should be taken to prevent iatrogenic injury of PIN according to four tips below: (1) The forearm is kept in full pronation during the dissection, which moves the nerve away from the operative field. (2) If more distal exposure is required, the supinator may be divided at its most posterior origin, so PIN becomes slack and moves forwards with the supinator, which places PIN in safer situation. (3)  If a plate is required, dissection is performed subperiosteally along dorsolateral part of the proximal radial shaft with the forearm pronated. But the bicipital tuberosity is the distal limit of dissection and placing plate. Anything distal to that structure endangers the posterior interosseous nerve. Placing less than 3.5 cm plate does not place PIN at significant risk for structural injury［8］.(4) Particular attention was paid to avoid vigorous or prolonged retraction anteriorly which is common cause of injury of PIN.Fig.3  The lateral ligaments complex of the elbow. LUCL, lateral ulnar collateral ligament; RCL, radial collateral ligament.

    Since the radial head fracture involves both radiohumeral joint and proximal radioulnar joint, anatomic reduction of it should be obtained. But accurate reduction of comminuted fracture of the radial head is technically challenging. Some tips below help to successfully reconstruct comminuted fracture of the radial head: (1) The anatomic feature of the radial head should be realized, that is, with the forearm in neutral position, the radial head is thickest in the medial portion where it articulates with the radial notch of the ulna. The radial head is slightly shorter in the lateral portions, where it is surrounded by the annular ligament. (2) For Mason type III fracture, the radial shaft separates from the radial head and loses support of the radial notch of ulna, so the proximal radial shaft is prone to displace medially as a result of the interosseous membrane's traction. During reduction, care should be taken to correct this medial displacement of the proximal radial shaft. (3) When there is bone defect in the radial neck, the fracture is prone to remain valgus or varus malformation. This malformation should be carefully corrected.

    Both achieving rigid fixation and avoiding impingement on the proximal radioulnar joint are two important requirements for fixing the radial head fracture. Prominent hardware may impinge on joints if placed incorrectly, leading to limitation in motion and pain postoperatively. So particular attention should be paid to some points below: (1) Screws should be countersunk in order to place screw heads below the articular surface and avoid impingement on the radial notch of ulna. (2) Inserting screw further after being countersunk should be taken in account, so overlong screw shouldn’t be chosen lest screw penetrate the opposite articular surface. (3) If plate fixation is used, the plate should be placed in the "safe zone" of the radial head, which is the lateral part of the radial head when the arm is in neutral rotation. If the boundaries of the safe zone are not violated, then plates can be used without fear of causing impingement on the proximal radioulnar joint and limiting rotation of forearm［9］.In addition, since the "safe zone" is the nonarticular portion of the radial head and is a distinct area that has minimal cartilage, careful inspection can identify the safe zone by its absence of cartilage.

    More than two or three weeks of immobilization for elbow fractures greatly increases the risk of a stiff, painful elbow, so early motion is paramount for optimal outcomes after radial head fractures［10］.As a result, internal fixation of radial head fracture must afford enough stability to allow early motion. Particular attention should be paid to some points below: (1) it provides more optimal fixation to insert the tip of the screws into opposite subchondral bone on the radial head without perforating the opposite articular cartilage. (2) A screw is inserted through the distal portion of the plate (distal to the head) and is angled proximally into the head, which significantly improves stability of the construct［11］.(3) Defects in the area of the radial neck should be filled with bone graft from the humeral lateral epicondyle or olecranon. (4) For the elbow joint that continues to be unstable after bony fixation and ligament repair, a supplemental hinged external fixator may be applied to allow early mobilization while ensuring that fracture remains stable.

    In conclusion, open reduction and internal fixation of displaced radial head fractures have good outcomes, with successful performing of the requirements as follows: protecting soft tissue, anatomic reduction, and stable fixation without impinging on joint. However, when the radial head is so excessively comminuted that anatomic reduction or stable fixation is difficult to achieve, prosthetic replacement should be considered for cases with such severe associated injuries as coronoid fracture and rupture of the medial collateral ligament. For excessively comminuted radial head fracture without associated injury, resection of the radial head may be considered.

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作者单位：天津市天津医院 中国 300070