JAAOS: Treatment of proximal ulnar fractures Wang Tao, Department of Orthopedics, Affiliated Hospital of Qinghai University
The treatment of proximal ulnar fractures can sometimes be difficult due to the more complex anatomy of the ulna. With the increasing understanding of the anatomy of the elbow joint as well as biomechanical aspects, some new advances in the treatment of this injury have come in. A detailed preoperative evaluation is critical, as failure to restore the normal anatomy of the proximal ulna can often result in significant impairment of postoperative function of the elbow. Treatment options include anatomic plates, intramedullary devices, and strong tension band materials. For a given fracture, x-rays and CT images, including three reconstructions, must be carefully analyzed in order to determine the most appropriate treatment plan. Coronoid fractures, hawkbone fractures, and associated elbow instability may affect the indication for a particular internal fixation device. In-depth knowledge of the anatomical details and biomechanical features of the proximal ulna is beneficial to improve its clinical outcome. Recent concepts such as the dorsal angulation of the proximal ulna, the importance of the anteromedial aspect of the coronoid process, and the medial fracture mass of the hawkbone have had a large impact on treatment.
Treatment of elbow fracture dislocations often presents some special challenges due to the complex anatomy of the elbow joint and the many important vascular and neurological accompaniments surrounding it. In addition, the thinner coverage of the soft tissues requires more careful intraoperative manipulation and careful postoperative management. Poorly repositioned proximal ulnar fractures may lead to many complications, such as contracture, instability, post-traumatic arthritis, and functional impairment [1-4]. Many fractures require surgical fixation for early activity to reduce complications such as joint stiffness, elbow instability, and post-traumatic arthritis [5].
Anatomy
The elbow, as a trochoid joint, consists of three joints: the proximal ulnar radial joint, the humeral radial joint, and the humeral ulnar joint. The stability of the elbow joint depends on the coherence of the individual bony structures as well as the surrounding soft tissues. The coronoid process is an important stabilizing structure that acts as a bony barrier to prevent posterior axial displacement of the ulna [6, 7]. The medial collateral ligament, especially the anterior bundle, is the most dominant structure against valgus stress in the elbow joint, while the lateral collateral ligament of the ulna prevents rotational displacement [3, 8]. The radial head is generally considered a relatively minor structure for countering valgus and postero-lateral rotational stresses [8, 9]. The ulnar eminence and coronoid process form the greater sigmoid notch, which is associated with the humeral talus. The small sigmoid notch, located on the lateral aspect of the proximal ulna, is associated with the radial head and forms the proximal ulnar radial joint. The large sigmoid notch has a transverse “bare area” on the articular surface, separating the hawk’s beak from the coronoid process, and the entire articular surface is covered with hyaline cartilage except for the bare area [10].
The morphology of the proximal ulna is highly variable, especially its angulation in the coronal and ulnar positions. The physiological curvature of the sagittal plane of the proximal ulna is called the proximal ulna dorsal angulation (PUDA) [11, 12].PUDA is present in 96% of the population, and for individuals, the degrees are highly correlated between the left and right elbow (r=0.86) [11]. The mean PUDA is approximately 6° and is usually located 5 cm distal to the tip of the hawk. It has been shown that the PUDA interacts with the total joint mobility (ROM) of the elbow joint, and the greater the dorsal valgus angle, the greater the endpoint of elbow extension decreases significantly [12].Puchwein et al [13] studied the mean proximal ulnar valgus angle, which is the angle of intersection between the axis of the hawser and the axis of the mid ulna, and is approximately 14° ± 4°. The authors also found that the mean anteflexion angle was 6° ± 3°. In clinical practice, to better guide surgical treatment, it is necessary to take x-rays of the healthy elbow, which are useful to determine the normal anatomical morphology of the proximal ulna, especially for these anatomical features where individual differences are evident [11, 14, 15].
The hawser prevents the ulna from shifting forward relative to the distal humerus [16, 17]. The triceps tendon terminates on the posterior bony surface of the ulnar hawkbone, while a layer of muscle tissue on the deep side of the tendinous tissue terminates directly at the hawkbone [18]. The net sagittal of the major muscles of the elbow, mainly including the triceps, biceps and brachialis all point dorsally (Figure 1). The intact coracobrachialis counteracts posterior displacement and inversion stress [19]. The coronoid process consists of the tip, the body, the anteromedial and anterolateral sides, and the elevated nodes [3]. The anterior bundle of the medial collateral ligament ends at the elevated tuberosity. The humerus muscle and anterior joint capsule are attached to the bony surface distal to the tip of the coronoid process, with a small amount of bony coronoid proximally and a large portion covered with cartilage located within the joint capsule [20].
Figure 1 This schematic shows the net vector of elbow muscle forces pointing dorsally (arrows). The eminence acts as a support to prevent the ulna from shifting forward (red line). The coronoid process primarily counteracts the posterior displacement of the ulna and acts as a support against inversion stress (blue line). The lateral ulnar collateral ligament (or ulnar bundle of the lateral collateral ligament) is also attached to the proximal ulna. The stop is located on the lateral side of the proximal ulna at the posterior rotator crest, just adjacent to the radial notch of the ulna and this crest.
Mechanism of injury
Fractures of the proximal ulna are usually the result of direct or indirect violence to the elbow joint and are mostly low-energy injuries, accounting for approximately 21% of all proximal forearm fractures [21]. Fractures of the tip of the coronoid are seen as a result of the constant accumulation of external rotation violence and the impact of the coronoid with the talus. If all structures are normal on radiographs except for a simple coronoid tip fracture, the possibility of later self-repositioning of the elbow dislocation or subluxation should be considered. The triad of terror is caused by superimposed violence of valgus and postero-lateral [22, 23]. The so-called triad mostly consists of a coronoid fracture, radial head fracture and elbow dislocation such that the lateral collateral ligament is injured. In addition, elbow inversion and posterior medial rotation violence can lead to anteromedial coronoid fractures [19]. The characteristics of the injury depend on the direction of rotation, with posterior rotational stresses leading to the terror triad, whereas anterior rotational violence leads to injuries that are mostly medial rotational instability after internal rotation.
Direct violence to the hawkbone usually results in comminuted fractures, whereas indirect injuries, such as avulsion fractures due to triceps contraction, tend to have transverse or oblique fracture types [16]. Comminuted fractures of the hawkbone may be accompanied by an intermediate fracture mass involving the articular surface, which is sometimes difficult to detect. Adequate knowledge of this type of intermediate fracture mass is crucial to restore the flatness of the humeral ulnar articular surface and to prevent a large sigmoid notch from developing a medically induced stenosis that could lead to impingement.
Diagnostic evaluation
A complete history and thorough physical examination are important for any patient with upper extremity trauma. Patients with proximal ulnar fractures typically have localized pain and swelling, and many have significant deformity in appearance. Range of motion (ROM) of the joint is mostly significantly decreased, and hawkbone fractures usually have limited extension of the elbow. Careful evaluation of vascular nerve function may reveal some combined injuries. In patients with high-energy injuries and fracture dislocations, special attention should be paid to the possibility of soft tissue as well as vascular-neural structural injuries. Careful examination of the soft tissues of the skin can sometimes provide useful clues to the status of deeper structures, and the condition of the soft tissue coverage is a very important consideration for the timing of surgery. Although fascial spacer syndrome is relatively uncommon in these injuries, severe swelling may be present if a proximal ulnar fracture is combined with a more distal forearm fracture.
For simple noncomminuted fractures, a positive and lateral view of the elbow is usually sufficient. Any discordance of the humero-ulnar or humero-radial joints should be noted on the radiograph and all possible fracture fragments should be identified. The radiocapitellar ratio (RCR) can be measured on lateral films to evaluate the alignment of the radial head (Figure 2).The RCR is the ratio of the minimum distance between the axis of the radial head and the center of the humeral tuberosity to the diameter of the humeral tuberosity. The RCR is a useful measurement when evaluating the displacement of the radial head relative to the humeral tuberosity. A poor alignment is determined if the value of RCR is outside the normal range of -5% to 13% [24].
PUDA and RCR are closely related. In an unpublished biomechanical study, we found that the presence of 5° of poor alignment of the PUDA can lead to subluxation of the radial head in the brachioradialis joint [25]. Therefore, in some complex fractures, it is important to take contralateral elbow radiographs in order to evaluate the patient’s normal PUDA, because a straight locking plate can usually alter the normal anatomical relationship and thus prevent successful repositioning of the brachioradial joint.
CT should be performed if the fracture is comminuted, if an intermediate fracture mass is present, or if an anteromedial coronoid fracture is suspected, and the indications for CT examination are broad. We believe that CT examination as well as 3D reconstruction can help to determine more accurately the type of fracture and the displacement of the fracture mass, which is helpful for preoperative development of a rational surgical plan.
Figure 2 The alignment of the radial head is measured by the humeral to radial ratio (RCR) on lateral views. the RCR is the ratio of the minimum distance between the axis of the radial head and the center of the humeral tuberosity to the diameter of the humeral tuberosity. a, make a plumb line of the articular surface through the center of the radial head; b, draw a circular outline of the humeral tuberosity and measure its diameter; c, determine the center of the humeral tuberosity (+); d, measure the plumb line of the radial head and the center of the humeral tuberosity the minimum distance between it and the center of the humeral tuberosity.
Fracture system
There are many ways to describe the staging of proximal ulnar fractures, and the ideal fracture staging system should be able to guide treatment decisions and determine the ultimate prognosis.
Hawk’s-beak fractures
Morrey [26] proposed a Mayo staging of hawkbone fractures based on the stability of the elbow joint, fracture displacement, and degree of comminution. type I is a fracture with no or mild displacement; type II, a displaced fracture but good elbow stability; and type III hawkbone with a large fracture mass on the articular surface and elbow instability. Each type is further divided into two subtypes, A and B, representing noncomminuted and comminuted fractures, respectively [16, 27].
The Schatzker subtype divides hawkbone fractures into six types [16, 28] (Figure 3) and includes the presence of intermediate fracture masses in a few fracture types, such as type II and III fractures of the Mayo subtype [26] and type B and D fractures of the Schatzker subtype [28].
Figure 3 illustrates the Schatzker’s typology of hawkbill fractures. type A, A, simple transverse fracture; type B, B, transverse fracture with central articular surface collapse; type C, C, simple oblique fracture; type D, D, comminuted hawkbill fracture; type E, E, oblique fracture with the fracture line located distal to the glide cut; type F, F, hawkbill fracture with radial head fracture, usually combined with a medial collateral ligament tear. (Reprinted from Hak DJ, Golladay GJ: Olecranon fractures: Treatment options. J Am Acad Orthop Surg 2000;8[4]:266-275.)
Coronal fractures
In 1989, Regan and Morrey [29] classified coronoid fractures into three types, mainly from lateral views: type I “avulsion” fractures of the coronoid tip; type II involving ≤50% of the coronoid height; and type III >50% of the coronoid. type III fractures were subdivided into type A Type III fractures are subdivided into type A, without elbow dislocation, and type B, with elbow dislocation.
O’Driscoll et al. later proposed a second typing method, based on the anatomical site of the coronoid fracture on CT, which was more descriptive. This anatomical typing system divides the coronoid process into three main parts: the tip, the anteromedial side, and the base. Fractures of the coronoid tip are divided into two subtypes: fracture fragments ≤2 mm and >2 mm (Figure 4).
Figure 4 illustrates the O’Driscoll subtype of coronoid fractures [23]. a, type 1; b, type 2, type 2 is subdivided into 1, 2, and 3 subtypes, with correspondingly increasing severity of anteroinferior coronoid fractures. c, type 3, type 3 is divided into two subtypes, with the first subtype being a non-fracture of the base of the coronoid and the second subtype being a fracture of the base of the coronoid in combination with an eagle’s beak. Figures A and B show axial images of the proximal elbow, showing a cross-section of the radial neck and radial head (dotted line embedded in the figure) and the lower edge of the articular surface. The three components of the coronoid process (tip, anteromedial surface, and elevated node) are visible in this cross-section.
The importance of this point is rarely emphasized in the literature for cases where both the hawk and coronoid processes are fractured.O’Driscoll et al [23] briefly described this combined injury in the second subtype of type 3 of their typing system. The treatment of this complex elbow injury to achieve the desired outcome depends largely on careful preoperative planning (Figure 5).
Figure 5 Complex fracture involving the coronoid process, hawk’s beak, and radial head. a, CT sagittal image showing a complex fracture involving the hawk’s beak and coronoid process, type 3, subtype 2 with reference to the O’Driscoll classification; b, lateral view of the fracture showing that the case in figure A was anatomically repositioned and fixed with a locking plate.
Monteggia fracture
Monteggia injury was first described in 1814 as a fracture of the proximal ulna with dislocation of the radial head [30].Monteggia injury disrupts the proximal radioulnar joint (PRUJ), thereby dislocating the radial head from the humeral tuberosity as well as the ulna. Type I, anterior dislocation of the radial head with anterior angulation of the proximal ulna fracture; type II, posterior dislocation of the radial head with posterior angulation of the proximal ulna fracture; type III, lateral or anterolateral dislocation of the radial head with proximal ulna fracture. type IV anterior dislocation of the radial head with proximal ulna and proximal radius fractures [3].Jupiter et al [32] modified the Monteggia fracture Bado staging was modified by subdividing type II fractures and describing the morphology of proximal ulnar fractures. type IIA fractures are located in the greater sigmoid notch; type IIB fractures are located in the proximal epiphysis distal to the coronoid process; type IIC are diaphyseal fractures; and type IID comminuted fractures of the proximal end of the ulna [33].
Treatment
As stated in the AO principles of fracture treatment, the main goals of fracture fixation are anatomic repositioning, stable fixation, protection of soft tissues, and early joint movement to prevent associated complications [34].
Non-operative treatment
Non-operative treatment of coronoid fractures is indicated for elbow joint stability, fractures with a simple coronoid tip ≤2 mm, or small fractures involving <15% of the coronoid height [19]. After a short period of elbow braking, joint mobility exercises are started as early as possible. Simple coronoid fractures are often associated with ligamentous injury; therefore, early in rehabilitation, the elbow joint should be routinely evaluated for coherent joint relationships to determine the presence of instability.
Conservative treatment is rarely an option for coracoid fractures, but nonoperative treatment is also possible if the patient is not a candidate for surgical treatment or if the patient is not demanding and the fracture has no displaced elbow extension device intact [16]. In these patients, close observation is very important to clarify whether the anatomic position of the fracture is maintained and whether the healing process is smooth. The elbow joint should be fixed in maximum flexion to prevent gaps in the fracture end, which are usually larger between 45° and 90°. Any upper extremity weight-bearing and active elbow extension should be avoided until complete bony healing is confirmed. For patients with good compliance, voluntary assisted joint mobility exercises should be routinely performed four times a day beginning 2 weeks postoperatively, though. However, immobilization with a long-arm removable splint may also be applied until imaging shows fracture healing.
Surgery
Most dislocations of hawk and Monteggia fractures in adults should be fixed with anatomic internal fixation. A common surgical approach for proximal ulnar fractures is shown in Figures 6 and 7.
Figure 6 Flow chart for the treatment of hawkbone fractures. c-arm: imaging fluoroscopy, C-arm; IF: compression screw between fracture blocks; ORIF: incision and reduction internal fixation; RCR: humeral to radial ratio.
a, the plate must be shaped with reference to the contralateral dorsal angle of the proximal ulna.
Figure 7 Flow chart based on O’Driscoll staging for coronoid fractures. lcl: lateral collateral ligament; ORIF: incision-reduction internal fixation; PUDA: proximal dorsal ulnar angle; ST: subtype.
Hawk’s-eye fracture
Isolated, simple noncomminuted transverse hawkbone fractures are usually fixed with the option of posterior tension band wire (TBW).TBW creates a dynamic compression force on the fracture end [35]. However, TBW is contraindicated for comminuted fractures and certain oblique fractures. TBW is also generally inappropriate if the hawk’s-beak fracture is located distal to the bare area and involves the base of the coronoid process. two smooth kerf pins (1.6 mm or 2 mm) are used to cross the fracture line from the proximal end of the hawk’s-beak and penetrate the anterior ulnar cortex [16, 36]. After breaching the second cortical layer, the Kirschner pin should be appropriately retracted to avoid damaging the surrounding soft tissues. One or two 18-gauge wires are passed deep through the triceps tendon, and then a 2-mm transverse bone hole is drilled at least 2 cm away from the fracture line at the dorsal distal fracture end of the ulna and penetrated in an “8” shape. The Kirschner pin is then bent in the opposite direction of the tension band and tapped deep into the triceps tendon. In addition, intramedullary screws can be used for longitudinal fixation.
This treatment has recently been challenged by Wilson et al. who concluded that preshaped plate fixation of transverse hawk fractures creates greater compressive stress on the fracture end. In addition, TBW has a greater risk of secondary displacement compared to plate fixation, and the need to remove internal fixation after TBW is more common.
Crush fractures or oblique fractures, if tension bands are applied, may lead to excessive compression of the large sigmoid notch, and joint surface narrowing may occur. More importantly, tension band structures do not provide adequate stability for complex fractures. In these particular cases, fixation must be achieved by interfracture screws as well as plates for anatomic repositioning and strong fixation. Steel plate fixation is usually performed using a straight posterior incisional approach. For complex fractures of the elbow joint, the authors recommend placing the patient in the lateral or supine position. The triceps stop must be protected intraoperatively, and the internal fixation can be placed directly on the surface of the tendon.
In addition, a small longitudinal incision can be made in the tendon to conceal the wire or plate. In some cases, where small or comminuted fracture fragments are present, suture fixation with Krackow or small tendon sutures may be used to reconstruct the triceps tendon stop. Comminuted fractures of the articular surface must be anatomically repositioned to minimize fissures and steps in the articular surface, avoiding large sigmoid notch stenosis and minimizing the risk of early osteoarthritis.
For comminuted fractures, we strongly recommend internal fixation with bone grafting. The joint cavity is thoroughly flushed prior to internal fixation to remove any bone debris that may remain. If an intermediate fracture mass is present, the “home run screw” technique usually results in a fairly satisfactory anatomical repositioning of the articular surface for internal fixation [38] (Figure 8). If the articular surface is crushed, it is necessary to expose the articular surface directly. The lateral approach to the elbow joint can be used as an alternative to a straight posterior incisional approach. The lateral collateral ligaments must be protected intraoperatively to avoid secondary joint instability. To better visualize and fix the small embedded or displaced intra-articular fracture fragments, the proximal fracture fragment of the hawkbone can be flipped if necessary. As many interfracture screws as possible are applied in a distal to proximal sequence to reposition and fix the individual fracture blocks and reconstruct the articular surface.
Figure 8 Lateral views (A) and sagittal CT (B) show the presence of an intermediate fracture block in the hawkeye fracture.C, Lateral images after internal fixation. The intermediate fracture mass, which can be clearly shown on sagittal CT (Figure B), is difficult to detect on radiographs (Figure A).
In some rare cases, the hawk fracture cannot be anatomically repositioned for internal fixation. Severely comminuted fractures (e.g., Schatzker type D) and open fractures with bone defects may not be amenable to the usual surgical approach. The proximal fracture fragment of the triceps tendon attachment should be preserved as much as possible. Sometimes the distal and proximal fracture ends can also be trimmed with an occlusal forceps, and the articular surface is made flat [39]. Then plate screws are used for fixation. In the bare area, some degree of bone loss is also acceptable. In order to avoid relative shortening of the proximal ulna simply posterior to the cortex, appropriate bone grafting should be considered. After strong posterior cortical fixation, the gap existing in the bare area of the non-articular surface is also gradually filled with fibrous tissue and stabilization is achieved. To further enhance the stability of the fixation, tendon sutures can be used for suture fixation through the triceps stop and the distal fracture end of the bone tunnel. The management of hawk bone defects is based on relevant biomechanical studies, such as the minimum amount of bone that needs to remain to maintain its stability. an et al [17] concluded that removal of no more than 50% of the hawk would not result in complete instability of the elbow joint.
Recently there have been new studies based on more complex biomechanical models that have improved our understanding of this issue. One of these studies showed that the removal of only 12.5% of the hawse is sufficient to alter the stability of the elbow joint [40]. However, this study also found that removing no more than 75% of the hawser did not result in severe elbow instability [40]. When performing reconstruction of the triceps tendon stop on the bony surface, it should be fixed as dorsally as possible to increase the length of the triceps. However, even in the ideal position, this can result in a 24% loss of length [41]. It is worth noting that all biomechanical studies assume that all other structures of the elbow joint are intact. Obviously, unless the hawk fracture is completely unreconstructable, hawk removal should be avoided.
Coronoid fractures
Coronoid fractures can be visualized and fixed through a posterior, medial, or lateral approach. A posterior skin incision with separation of the lateral flap allows simultaneous management of the lateral collateral ligament injury, and preoperative planning for surgical management of the radial head is well suited [42]. The coronoid process can usually be revealed anteriorly from the radial head, or the coronoid fracture can be managed prior to placement of a prosthesis after radial head resection. The forearm should be placed in a rotated anterior position intraoperatively to protect the posterior interosseous nerve. Larger coronoid tip fractures may be fixed with compression screws or threaded kerf pins. Fixation can be performed anterior to posterior or posterior to anterior under x-ray or arthroscopic surveillance. If the fracture is comminuted or the fracture fragment is too small to allow for screw placement, a suture fixation technique should be considered, in which the anterior joint capsule near the coronoid process is sutured to the fracture fragment for better stability. A bone tunnel is created by drilling a hole from the dorsal ulnar cortex into the fracture bed and passing a suture through it, taking care that two bone tunnels should be drilled and a knot tied between the two holes for fixation. The bone tunnel should avoid the dorsal bone crest and be biased medially or laterally so that the suture material does not agitate the soft tissue. If drilling from the medial side, care should be taken to protect the ulnar nerve.
Anteromedial coronoid fractures can usually be exposed through a medial approach to the joint, and the skin incision can be chosen medially or posteriorly [43]. The ulnar nerve is first revealed in the elbow canal, released in situ, and retracted posteriorly to avoid injury to this nerve. An “L” shaped incision is made distally and proximally to separate the flexor-anterior muscle group from the medial epicondyle of the humerus, preserving the medial collateral ligament. The joint capsule is dissected and then fixed anatomically with screws under direct vision or, if desired, with a supporting plate [3, 44] (Figure 9). Alternatively, a longitudinal split of the flexor-pronator muscle group can be performed anterior to the ulnar nerve to reveal it.
Figure 9 A, orthopantomogram of the elbow showing a large fracture of the anteromedial aspect of the coronoid process (arrow), which is easily missed; B, lateral view showing elbow instability and an abnormal humeral to radial ratio; C, postoperative lateral view showing that after repositioning through the medial approach, microplate screws were applied for fixation and the medial and lateral ligaments were repaired with bone anchors.
The coronoid process is critical to the stability of the elbow joint, and even small fracture fragments may have a significant impact on the biomechanics of the elbow joint. Tough fixation techniques must be applied to larger fracture fragments to re-establish their stability and to maximize the possibility for bony healing.
Complex fractures
Combined coronoid fractures are challenging to treat for proximal ulnar fractures. The patient is placed in the lateral or prone position and the procedure is performed using a posterior approach. The proximal fracture fragment of the hawk’s beak is turned proximally in conjunction with the triceps stop to expose the coronoid fracture fragment. It is useful to apply a surgical strategy of resetting the fracture block from distal to proximal. The coronoid fracture block is repositioned in the flexed elbow position. The soft tissues on the medial and lateral sides of the hawk are appropriately peeled and anatomic repositioning of the fracture fragment is confirmed under direct vision. The lateral collateral ligaments must be preserved intraoperatively or repaired before the end of surgery to maintain elbow stability. A fracture is usually present in the elevated tuberosity, and lifting the elevated tuberosity reveals other coronoid fracture fragments. Special care should be taken to protect the ulnar nerve when exposing any medial fracture fragments. The intra-articular fracture fragment is fixed with interfracture screws or threaded kerf pins. Finally, the hawkbone fracture block is reset and fixed with a plate posterior to the ulna and hawkbone (Figure 5). If poor alignment of the humerocarpal joint is suspected, the PUDA on the contralateral elbow radiograph should be measured to restore the normal angle of the proximal ulna.
Postoperative management
The postoperative rehabilitation program for humeral fractures depends mainly on the state of the soft tissues and the stability of the fixation. For patients with good compliance, if the fixation is secure, braking can be applied for one week to promote wound healing and control swelling, and then joint mobility exercises can be started as early as possible. After imaging confirms bony healing, passive joint mobility exercises, muscle strength training, and weight bearing are allowed. Patients with poor skin and soft tissue conditions may be immobilized with a hinged brace and limited to posterior extension until the wound heals. Flexion is gradually allowed with reference to a controlled ratio (e.g., 15° increase per week), depending on the rate of soft tissue recovery. If strong fixation is not available, joint mobility exercises should be appropriately delayed and elbow braking may take 2 weeks or more.
Lessons learned
Good preoperative planning is essential in the face of a proximal ulnar fracture (Table 1). In order to restore the normal anatomic shape of the articular surface of the elbow, anatomic repositioning and exact fixation of each fracture fragment is necessary. Simple fractures can be treated with tension bands or plate screws; relatively complex fractures are usually limited to plate screws. Coronal fractures can be visualized through a medial, posterior (via the fracture end of the hawser), or lateral approach. In order to obtain an anatomic repositioning of the articular surface fracture block, the intermediate fracture block needs to be fixed first to create a relatively simple fracture that facilitates the repositioning and fixation of the proximal fracture block.
Non-anatomic reconstruction of the proximal ulna can result in poor alignment or dislocation of the humeral radial joint. Fixation of the proximal fracture fragment in a flexed position can lead to narrowing of the greater sigmoid notch and consequent restriction of motion. Improper positioning of the internal fixation can also lead to limitation of motion or ulnar nerve symptoms. Poorly positioned screws or clincher pins can impair motion and damage the articular cartilage surfaces. Intraoperative fluoroscopy is helpful in evaluating the final fracture reduction and the position of the internal fixation. The stability of the fracture fixation is checked by full range of joint motion of the elbow joint, whether the internal fixation interferes with joint motion, and to determine whether the articular surface is uneven. The movement of the elbow joint must be smooth and free of abnormalities such as scraping and popping.
Results
Clinical outcomes of internal fixation of hawk fractures were described in a number of case series with small sample sizes (Table 2). On average, there was a loss of approximately 30° of humeral ulnar joint motion after plate screw internal fixation and, of course, there was an improvement in joint motion after removal of the internal fixation [45-47,49,50].Removal of the internal fixation was required in 18-62% of cases and was the most common complication of hawkbone fractures. The majority of patients had excellent Mayo elbow function scores [45-47,49]. Patients with plate fixation of hawkbone fractures had shoulder-arm-hand dysfunction scores (DASH) and QuickDASH scores between 9 and 17 [45-47,49]. In studies with long-term follow-up, post-traumatic arthritis was seen in 21%-48% of patients [49,50].After reviewing the relevant orthopaedic literature, Anderson et al. found a higher rate of internal fixation removal in TBW (11%-82%) than in plate systems (0-20%).
Approximately 58% of the anterior medial aspect of the coronoid process protrudes from the proximal ulnar trunk, a feature that makes the anterior medial aspect of the coronoid process more susceptible to injury as well [51].Doornberg and Ring [52] confirmed the importance of exact fixation of the anterior medial aspect of the coronoid process, which can otherwise affect elbow stability, leading to inversion instability, early osteoarthritis, and moderate or poor Broberg-Morrey scores.
In conclusion
Proximal ulna fractures can be challenging even for very experienced surgeons. It is critical to clarify and then try to restore the unique proximal ulnar anatomy of each patient. A thorough evaluation of the injured limb and associated imaging data is necessary to arrive at an accurate diagnosis, develop an appropriate preoperative plan, and obtain a favorable treatment outcome. Studies related to clinical outcomes have shown a high incidence of postoperative complications, including associated conditions due to internal fixation or post-traumatic arthritis. From a methodological point of view, surgical decisions must be made taking into account the need to restore the anatomy and biomechanics of the elbow joint to the greatest extent possible. Further research and improvement of surgical techniques and internal fixation devices would certainly be helpful to improve the clinical outcome of these complex fractures.