Background
Fractures of the isolated distal femoral condyle in the coronal plane were first described by Hoffa in 1904 [
1]. This condition is rare and accounts for less than 1% of all femoral fractures, as it typically results only from high-velocity injuries [
2,
3]. Despite this low incidence, Nork and colleagues recently reported a 38% incidence of coronal plane supracondylar-intercondylar distal femoral fractures in adults [
4]. This type of fracture has been reported to involve the lateral condyle more commonly [
5], but fractures of the medial condyle have also been described [
6]. Some authors have postulated that these fractures result from direct impact with the knee in a flexed position, while others have attributed the fracture to simultaneous vertical shear and twisting forces [
5,
7].
Operative treatment has been recommended for patients with condylar femoral fractures because surgical fixation provides stable restoration of the articular surface and facilitates early range of motion [
5]. In recent years, several small series of cases were reported on outcomes after open reduction and internal fixation (ORIF) of Hoffa fractures [
2‐
4,
6,
7]. Most of these cases were fixated using lag-screws for isolated Hoffa fractures, although the strength of this fixation may be insufficient for the comminuted fragments at the supracondylar distal femur region. Given that this is a rare type of fracture, the coronal fracture line that crosses the condyle to the supracondyle of distal femur has not been described by typical AO/OTA or Letenneur classification [
8,
9]. Accurate recognition of these injuries will assist with planning the surgical approach and determining the optimal implants for fixation. Furthermore, the use of Ni-Ti Alloy for the treatment of distal femur fractures has not been evaluated.
The goal of the study was to analyze the radiological and functional outcomes of patients after surgical treatment of comminuted coronal plane supracondylar-condylar femoral fracture using Ni-Ti arched shape-memory connector (ASC) and partially threaded cancellous screws (PTCS). We also reviewed the literature to highlight the importance of accurately detecting these fractures as well as describe the role of early and rigid internal fixation on patient outcomes.
Discussion
A comminuted condylar fracture of the distal femur, associated with a coronal split of both the condyle and supracondyle is a challenge to diagnosis and treat. Most cases present with an obviously swollen knee joint, haemarthrosis and pain; however, the diagnosis is best made by radiographs. Displaced condylar fragments can be seen on lateral radiographs, but minimally displaced or even undisplaced fractures in the coronal plane can be easily missed. Computerized Tomography (CT) scans should be performed cases in which these fractures are suspected based on clinical presentation and mechanism of injury.
Coronal plane supracondylar-condylar femoral fractures are intra-articular and inherently unstable. Most authors conclude that conservative treatment, including closed reduction and cast immobilization or prolonged traction, places the patient at risk for displacement of fracture fragments and future nonunion [
15‐
18]. A long period of immobility time can result in joint stiffness, poor joint physical function and subsequent osteoarthritis [
19]. Based on these potential poor prognostic factors, these fractures should be treated via open or arthroscopic reduction and internal fixation. A midline incision with a medial/lateral parapatellar arthrotomy is the most common approach reported. Direct lateral approach with or without osteotomy of the Gerdy tubercle and posterior-based approaches have also been described [
20,
21]. Holmes et al [
18] proposed a standardized surgical approach to the fracture and rigid fixation with optimally positioned lag screws placed perpendicularly to the fracture plane. They reported that an ipsilateral parapatellar approach provided optimal visualization of the fracture and the articular surface as necessary to achieve a perfect anatomic reduction and rigid internal fixation. This technique may benefit early and unrestricted range of motion exercises, which lowers the risk of knee joint ankylosis. We feel that either the medial parapatellar arthrotomy or direct lateral approach is appropriate, as both provide good visualization of the fracture and the articular surface. Additionally, these approaches are familiar to most orthopaedic surgeons who perform total knee replacements.
There are relatively few recommendations in the literature for fixation of coronal fractures of the posterior femoral condyles. Benirschke and Swiontkowski suggested the use of 3.5 mm cortical lag screws [
22]. Liebergall et al recommended use of 6.5 mm cancellous screws [
23]. Mize suggested that K-wires and absorbable pins are not strong enough and recommended use of 4.0 mm cancellous or similar screws [
24]. Jarit et al. reported that PA screws showed less displacement than AP screws when subjected to vertical loads [
25]. However, the PA screws need to be countersunk, which can result in cartilage damage. This was addressed in the current study using headless screws [
26], although these screws have the disadvantage of small size and length. Most of reports of these fractures include simple fractures with two or three big fragments. For comminuted fractures of the supracondylar-condylar region of the femur, using screws alone cannot provide anatomical reduction of the joint with stable internal fixation that permits early range of motion.
Recently, the Less Invasive Stabilization System has been developed to manage distal femur fractures. This system uses multiple, fixed-angle, distal locked screws and can be best thought of as a submuscular “internal” fixator [
27]. Multifragmentary fractures of the metaphysis are reduced by indirect means and stabilized by plates, which act as bridge plates; however, the metaphyseal part of the fracture is never visualized [
28]. Using the principles of minimally invasive plate osteosynthesis the plate is slid underneath the muscle and external to the periosteum [
29]. This form of closed reduction without additional traumatization of the diaphyseal area leads to improved fracture healing and improved local resistance to infection [
30]. However, surgical exposure of the site using this method is limited. This carries with it an inherent risk of postoperative malrotation and malalignment, especially in intra-articular fractures [
30,
31].
The current trend in the treatment of periarticular fractures is the use of small fragment implants that are lower profile and necessitate less periosteal and soft tissue disruption. To avoid the need for a distal femoral locking plate, we implemented ASCs as adjuvant to partially threaded cancellous screws internal fixation for comminuted coronal plane supracondylar-condylar femoral fractures.
Ni-Ti shape-memory alloy, as a functional metal material, possesses excellent properties of wear and corrosion resistance and good biocompatibility, as well as shape-memory effect. In 1990, the FDA (USA) approved this alloy for medical use. Medical applications of this material expanded and Ni-Ti shape-memory alloy was widely regarded as a “valuable biological memory material” [
32]. In the past decade, shape-memory alloys have been gradually applied to various clinical fields of practice including stomatology and orthopedics [
32,
33]. ASC has been shown to be an effective means for the treatment of humeral shaft nonunions, scaphoid waist nonunions and acetabular fractures [
10‐
14]. Despite the widespread use for a variety of fractures, no clinical studies on its use in distal femoral fractures have been reported.
Compared with other methods, ASC with associated PTCS is advantageous for the following reasons: 1) Screws fixing posterior femoral condyle fractures are usually placed through articular cartilage. The ASC can be placed at the lateral side to minimize the damage to the articular cartilage, which may reduce the development of post-traumatic arthritis (Figure
4-e). 2) As a rigid and reliable fixation method, traditional medial/lateral femoral blade plates have been used for comminuted fractures of the distal femur. However, the use of these plates requires wide exposure and greater disruption of the periosteum and soft-tissue. Minimally invasive techniques such as the Less Invasive Stabilization System may eliminate the need for a wide area of surgical exposure; however, open reduction and using the ASC for coronal supracondylar fractures may be superior considering the quality of reduction, short operation time, need for minimal soft tissue dissection, and low risk of vascular injury and blood loss. 3) The fixation material should have a modulus equivalent to that of bone. Current implant materials have higher stiffness than bone, which prevents the needed stress being transferred to adjacent bone. This biomechanical alteration can lead to excessive resorption and subsequent implant loosening through the “stress shielding effect” [
34]. ASC is a functional fixator with excellent combination of high strength and low modulus that is more akin to that of bone [
35]. In addition, due to the inherent property of shape-memory alloy, the compression arms in the device provide evenly distributed compression forces. These forces provide continuous axial compression on the fractured ends, which can be transmitted across the fracture to ensure the stable biomechanical environment that allows smooth healing of the fracture line. In our patients, fewer screws are required and full healing was achieved in 7 weeks, similar to other fixation methods [
4,
5,
7].
Although this preliminary study revealed the feasibility of using ASC for distal femoral fixation, several limitations exist. This study was retrospective, patients were not randomized to evaluate comparative effectiveness and our sample size was too small to perform statistical analysis. However this is the first report to describe the use of ASC in comminuted coronal plane supracondylar-condylar femoral fractures.
Competing interests
The authors declare that they have no conflicting interests.
Authors’ contributions
YZ, YX and SX contributed to the study concepts, literature research and manuscript preparation. CZ and YX are the guarantors of integrity of the entire study and participated in the operation and manuscript review. XZ, YT and SX participated in literature research, data acquisition and data analysis. All authors read and approved the final manuscript.