The capitulum is located on the lateral side of the distal humerus and protrudes forward and downward. It functions largely to maintain the stability of the elbow joint [17, 18]. Capitellar fracture, with or without humeral trochlea fracture, is intra-bone. Most displaced fracture blocks have no obvious soft tissue attachment and cannot be reset by ligament reduction techniques. It is generally accepted that surgical treatment is superior to non-surgical treatment with respect to a number of clinical outcomes[19, 20].
During surgery, the comminuted small bone can and should be used to reset and fix the fracture rather than dissecting and discarding it. However, when fixation is unreliable it should be removed in order to avoid mechanical blockage of joint activity. Small bones and associated soft tissues such as articular capsules feature good blood supply, and post-surgery they participate in bone repair and accelerate fracture healing. Conversely, a small damaged fracture block exposes the fracture surface directly to the articular cavity, which can lead to traumatic arthritis, ossifying myositis and even joint instability that eventually can severely affect elbow joint function[20]. Ashwood et al. considered it very important to maintain firmness following fracture reduction, thus elbow joint small cartilage blocks should be maintained as required for reduction and internal fixation during surgery[21]. Jupiter et al. reported that elbow joint function at the humeral distal frontal plane was correlated with the recovery of normal anatomy[22]. In the current study, 24 patients with capitellar fractures were treated by vertical or parallel micro-locking plate technique. We found some advantages of this approach including stable fixation, early resumption of elbow joint activity and good functional recovery.
Selection of surgical approach to capitellar fractures treatment.
There is currently no uniform, standard guide to selecting the optimal surgical approach to treating capitular fractures. Singh et al. describes surgeries including the anterior approach to the elbow and the posterior approach to the ulnar olecranon[23]. However, the classic posterior lateral Kocher approach is used for treating most distal articular surface fractures of the humerus. In our view, the choice of surgical approach depends largely on the shape of the fracture, the direction of displacement and the surgeon's familiarity with a given approach. The anterior approach of the elbow joint is complicated and includes risk of damage to blood vessels and nerves[24]. The posterior approach of the ulnar olecranon can reveal posterior condyle fracture but entails more surgical trauma and increased probability of heterotopic ossification in the elbow joint[22]. The posterolateral Kocher approach of the elbow joint provides good exposure, relatively decreased trauma, increased safety and fewer postoperative complications[24, 25]. Sano et al. reported good clinical results using a lateral approach for fracture reduction and internal fixation inpatients with distal humeral frontal plane fractures[26]. For all 24 patients in the current study the classic lateral Kocher approach resulted in good exposure, reduction and fixation. No other surgical incisions were made and no obvious elbow instability was observed.
Assessing Dubberley B-typefracture treatment outcomes.
It is difficult to compare clinical results of different treatment methods for capitellar fractures, largely due to low incidence. However, additional factors also contribute to the difficulty of assessing outcomes. Young patients often suffer high energy injuries that usually feature combined composite injury of elbow joint structure[24]. Due to severe crushing of the fracture the joint remains unstable after simple bone structure repair. In elderly patients, most often with low energy injuries, fractures are not severely crushed but local compression and poor bone condition result in loosening of internal fixation and displacement of fractures[1]. If the small bones of the articular surface are preserved during fracture comminution, internal fixation is difficult and the fracture block is easily loosened after surgery[18]. It becomes a block in the joint that affects activity. If, however, the small bones of the articular surface are not preserved the shape of the ankle joint and the ulnar joint surface will be altered and the humeroradial and ulnar joints will not match. This will result in an unstable elbow joint and lead to traumatic osteoarthritis[18]. In our view, surgery to treat capitellar fractures with or without trochlear fracture should aim to restore a uniform match of the humeroradial and humeroulnar joint, strongly fix the fracture, maintain fixation and joint stability and restore maximum joint activity range and function. Achieving these aims depends critically on choosing the appropriate approach to internal fixation.
Fixation method and positioning.
Independent screw fixation is commonly used for internal fixation and is associated with good outcomes in previous studies[23, 27, 28]. However, it is an appropriate technique for simple fractures, such as no bone loss present or posterior comminution (Dubberley Type 1A and 2A)[28]. Sano et al. report that in the case of a capitulum of the humerus fracture with a thin fracture block, the screw thread will not fully pass the fracture line and function as a lag screw if inserted from the rear. If the fracture block is too small, the screw may damage the joint surface or cause the bone to split. Additionally, if the fracture block is too small it is difficult to seat the screw thread in the cartilage[26]. It has also been certified that the screw will damage the articular cartilage leading to cartilage necrosis or osteolysis and affect elbow joint function[21].However, this ensures only the stability and firmness of the frontal plane but not the effective fixation of a comminuted posterior condyle or incomplete humeral external condyle fracture that would permit early functional rehabilitation exercises. Studies involving greater numbers of patients and extended follow-up show that distal frontal plane and anti-sliding plate treatments do not guarantee stability and firmness of frontal plane fractures nor ability to perform early functional exercises for patients with osteoporosis[29] It therefore remained to identify a suitable approach to enhancing the stability of fixation. So, we put forward vertical and parallel techniques. First, we used a Kirschner wire and screw to fix the fracture. Then, a micro-locking plate was placed on the posterior side of the humerus for support and fixation of the lateral and posterior humerus. Finally, a micro-locking plate was used in the front of fracture for anti-glide. Our technique has several advantages over previous methods of fixation. Firstly, the 1.5 mm and 2.0 mm micro-locking system screws can meet the requirement for multiple screws on the fracture block, and the small screws can replace the Kirschner wire. Secondly, the locking plate-screw-fracture block can be completely integrated into one body in which loosening of the screw and bone plate breakage are unlikely[30]. The advantage of this approach is particularly apparent for patients with comminuted fracture or osteoporosis, requiring support and fixation that restores the original length. Thirdly, two-plane internal fixation of the distal end of the humerus using a micro-locking plate not only achieves front side anti-slip and lateral & posterior support, but also effectively covers a crushed fracture thereby guaranteeing stability and firmness and also maintaining stability and compatibility of the articular surface after reduction. It affords maximal fixation stability that promotes early rehabilitation of elbow joint active and passive flexion and extension exercises to fully restore elbow joint function. The minimal amounts of built-in material reduce irritants otherwise adversely affecting later functional exercises. Follow-up of the 24 patients in this study showed stable internal fixation, no displacement and good position of the fracture. All of the patients displayed early recovery, with satisfactory elbow function.