Radial head fracture accounts for one-third of elbow joint fractures. The principal cause of fracture is high energy impact transmitted from the hand and wrist during a fall (11). This occurs more commonly in energetic sports and hard physical labor. The mean age of affected patients is 45 years (12).
Treatment options for radial head fracture depend on classification, degree of soft tissue damage, dislocation and number of fragments. Isolated nondisplaced fractures, or those with displacement of less than 2 mm and without mechanical obstruction can be treated by immobilization. Comminuted fractures or those that are simple with displacement of greater than 2 mm are usually treated surgically(1). Options include open reduction and internal fixation, or radial head excision and arthroplasty. Radial head partial fracture or comminuted fracture having fewer than 3 fragments can be fixed with screws and plates(4). Severely comminuted fractures are almost impossible to fix with plates and screws, and cause a higher rate of failure of fixation, nonunion and osteonecrosis (13). This type of fracture is defined as “unsalvageable” or “unrepairable” radial head fractures (6, 14) and are usually treated by radial head resection or arthroplasty.
Deficiency in the radial head will lead to a series of complications such as valgus instability, radius proximal migration with consequent wrist pain, posterolateral rotatory instability and elbow joint dislocation. because the radial head is a secondary stabilizer of the elbow and forearm (3, 6, 15, 16). Therefore, resection of the radial head is now rarely performed and only if the patient is of advanced age and has low functional requirements.
With improvements in radial head prostheses, radial head arthroplasty has become a feasible option for treatment of comminuted radial head fractures (5). Compared with radial head resection, radial head replacement can significantly improve the stability of the elbow joint (5). If the fracture is combined with collateral ligament disruption, elbow joint dislocation, “terrible triad” injuries or Essex-Lopresti injuries, radial head replacement can provide up to 75% of valgus stability (17). Radial head replacement can significantly shorten the duration of surgery compared with ORIF. This advantage is especially important when the fracture is combined with dislocation and soft tissue rupture that requires repair during surgery. Radial head replacement appears to have fewer complications than ORIF in comminuted fracture (18).
Conversely, radial head replacement also suffers characteristic complications. The reliability of prostheses remains controversial. Periprosthetic stem lucency is common during long-term follow-up (9). The majority of lucency is asymptomatic, but some develop into stem loosening combined with varying degrees of pain. Signs of ulnohumeral arthritis in radiographs is found in 38% of patients 8 to 12 years after arthroplasty. Capitellum resorption is also not difficult to identify(19). Depending on the design of prosthesis, the total survival rate after 8–12 years varies from 0–24% (8, 19–21). Longer periods of observation are required.
Considering the uncertain long-term outcome of arthroplasty, radial head replacement should be used cautiously on patients under 50 years of age. Every effort should be made to preserve the radial head prior to resection or replacement in patients under 30 years of age. In addition, due to religious beliefs and cultural considerations, it is occasionally difficult to persuade the patient to undergo radial head resection or replacement.
Absorbable pins provide an approach to conduct ORIF of radial head fractures which cannot be fixed with metallic plates and screws. Compared with traditional screws and plates, polylactide pins have a number of unique advantages when treating severely comminuted radial head fractures. Smaller diameters (1.5 mm) allows fixation of each fragment with multiple pins from different directions. Combined with an “on-table” construction technique, the surgeon can fix a fracture with more than 4 fragments into a “ferroconcrete” structure. In our experience, this technique exhibits high error tolerance capability. In extremely conditions, fractures that have failed to be fixed with screws and plates still can be fixed with polylactide pins, even have 2.5 mm drill holes on the fragments (Fig. 5). This “ferroconcrete”-like radial head has superior robustness which can tolerate the most drastic reduction manipulation, which the screw and plate technique cannot. In addition, polylactide pins are considerably easier to handle than screws and plates. The surgeon only needs to fix the fracture with as many k-wires as required, which are then replaced with polylactide pins one by one. For screws and plates, the k-wires block the insertion of the screws such that the number and direction of k-wires is restricted, causing in the temporary fixation to be unstable.
In the present study, the duration of surgery and blood loss in both groups was not statistically different. Considering that fractures of the experimental group are clearly more comminuted than the control group (fragment numbers: 4 (SD: 0.6) and 3 (SD: 0.3), respectively; p < 0.0001), polylactide pins can also shorten the duration of surgery and reduce blood loss. Polylactide pins can easily be thermally cut into any length and placed under cortical bone and cartilage. This completely avoids the risk of joint obstruction and soft tissue irritation. Conversely, metallic screws must be sunk under the cartilage which risks over-compression (Fig. 6) and secondary fractures. Plates must be placed at a “safe-zone” on the radial head which restrict positioning and direction of screw placement (10).
A number of studies have already compared the outcome of polylactide pins with metallic fixation for the treatment of Mason type Ⅱ-Ⅲ radial head fracture. Clinical and functional scores of polylactide pins were found to be as effective as metallic fixation (22, 23). However, the majority of samples in these studies were non-comminuted or only slightly comminuted fractures. Researchers have seldom used polylactide pins to treat “unsalvageable” radial head fractures.
The present study aimed to compare the feasibility of treating severely comminuted radial head fractures using polylactide pins with metallic fixation. In the department of orthopedic of University-town Hospital of Chongqing Medical University, polylactide pins were used to treat radial head fractures with more than 4 fragments. Therefore, the injuries of patients who underwent polylactide pin fixation were more serious than those who received screw and plate fixation. A number of patients also suffered from a combination of injuries such as elbow joint dislocation, “terrible triad” injuries and collateral ligament rupture. Radial head fractures with significant instability of the elbow joint endured considerably worse outcomes than simple fractures (1, 3, 14). In order to eliminate this factor, fractures in which dislocation, “terrible triad” injuries, coronoid fractures or collateral ligament rupture had occurred were excluded. It is clear that once patients with joint instability had been excluded, there was no statistical difference in long-term function between the experimental and control group. The range of motion of the two groups was almost the same. The pronation angle of the control group appeared to be larger than the experimental group, but not statistically so.
Two to 3 patients in each group suffered complications, but there is no evidence that the complication rate of one group was greater than the other. No complications caused disability and patients were satisfied with the outcome.
Because of the limitations of metallic implants, fractures fixed with polylactide pins are more comminuted than those fixed with metallic implants. This factor affected the consistency of the samples. But since outcomes of the experimental group were similar to those of the control group, despite having more severe comminution, the conclusions remain valid. On the other hand, the number of samples in the study was small. This is in part because a large number of patients with elbow instability were excluded. In addition, follow up periods were not sufficiently long, and so long-term outcomes of this technique are unknown. We plan to add additional samples into the study and follow-up the patients for a longer period. Finally, since arthroplasty is the most commonly used technique to treat severely comminuted radial head fracture, it would be more meaningful to compare polylactide pins with radial head replacement