Of the 124 patients, 41.9% (n=52) were male (p=0.072) (Table 1). The mean age was 63 years and the median age was 68 years with a range between 15 years and 101 years. There was a classic bimodal distribution with a higher proportion of patients between 15-40 years and 50-90 years sustaining distal femoral fractures (Fig. 2). There were a total of 125 fractures with 52.8% (n=66) on the left, 45.6% (n=57) on the right and 0.8% (n=1) bilateral. Although not statistically significant, men were more likely to be younger than women when sustaining these injuries with a median age of 66 years compared with a median age of 71 years (p=0.55). Men had 65.6% (n=21) of the associated injuries cohort.

Fig. (2). Gender and Age at time of Injury.

Mechanism of injury was classified as high energy (fall from >2m, road traffic collision, assault and penetrating injury) or low energy (fall from<2m).

When unspecified injuries were excluded there was a statistically significant difference between sex and mechanism of injury. High-energy trauma was more likely in men (M: 70.5%, n=31 vs. F: 29.5%, n=13) and low-energy trauma more likely in women (M: 17.3%, n=9 vs F: 82.7%, n=43) (p<0.0001).

The most common mechanism of injury was falling (48.4%, n=60) followed by motor vehicle incidents (26.6%, n=33), assaults (1.6%, n=2) and penetrating injuries (0.8%, n=1). Twenty-eight patients had non-specified injuries or other injuries not coded for within our search parameters (Fig. 3). Of the 60 patients who fell, the majority did so from ground level (86.7%, n=52). Falling from greater than a two meter height occurred in eight patients (13.3%). The 33 motor vehicle incidents were due to pedestrian vs car (21.2%, n=7), cyclist vs car (15.2%, n=5), motorbike vs. car (27.3%, n=9), multicar collision (3.0%, n=1) or unspecified (33.3%, n=11).

Fig. (3). Gross distribution of mechanism causing distal femoral fractures.

Fracture type consisted of 65 (52.0%) type 33-A, 38 (30.4%) type 33-B and 22 (17.6%) type 33-C configurations as seen in Table 1. Subgroup analysis revealed 33-A1, A2, A3, B1, B2, B3, C1, C2, C3 to comprise 51 (40.8%), 5 (4.0%), 9 (7.2%), 18 (14.4%), 15 (12.0%), 5 (4.0%), 4 (3.2%), 7 (5.6%) and 11 (8.8%) patients respectively (Fig. 4). Involvement of the knee joint was present in 60 patients (48.0%).

Fig. (4). Distribution of Injury Pattern according to AO/OTA Classification System .

The majority of patients had an inpatient stay of less than two weeks when censored at either discharge or death. The longest inpatient stay was 95 days (Fig. 5).

Fig. (5). A graph displaying the length of inpatient stay censored at either death or discharge .

Associated injuries were documented in 32 (25.8%) patients. Thirty (93.8%) of these patients had a second fracture elsewhere.

In total, 92 (73.6%) fractures underwent operative management (Fig. 6). There were 27 (21.6%) fractures managed conservatively for various reasons including undisplaced stable fractures, extreme frailty and poor pre-morbid function. Six (4.8%) patients had missing operative records. Our experience determined the use of locking plates to be the most common intervention occurring in 59 (64.1%) operations. Other operative approaches include IM nailing (18, 19.6%), screws (10, 10.9%), IM nail and screws (2, 2.2%), external fixation (2, 2.2%) and TKR (1, 1.1%).

Fig. (6). A graph demonstrating the different management options for treating distal femoral fractures.

The MTC in this study is estimated to service a population of around three million in London [12]. This is likely to be an underestimate given the high commuter population and presence of three other MTC hospitals within London. Had the population remained static over a five year and two month period, our study indicates distal femoral fractures that present to MTC status hospitals have an incidence of 8/million/year in an area covering one quarter of Greater London. This figure remains crude. It also does not cover patients who may have presented directly to Trauma Unit hospitals within the catchment area of MTC. It does, however, highlight the relative rarity of such fractures compared to proximal femoral fractures [13].

Court-Brown and Caesar classified common fractures into eight age-sex distribution curves (A to H) [2]. According to their study, the epidemiology of distal femoral fractures follows curve E (unimodal distribution in elderly females). Our study demonstrates a distribution more akin to curve A. This finding echoes a study by Pietu et al. that determined their population of 177 patients with distal femoral fractures at 12 hospitals in France [14]. The mean and median age seen in our experience is similar to that seen in other epidemiological studies [15, 16]. Fifty-eight percent of the patients in our study were female. This is lower than the 73.1% (n=147) females seen in a similar study of 201 distal femoral fractures by Ng et al. [17]. Although not discretely reported, Kolmert and Wulff graphically display a much higher proportion of female patients than male patients with this fracture pattern [15]. Baron et al. analyzed data from 5% of the U.S. medicare population for fractures that occurred between the years 1986-1990 [18]. They demonstrated that the rate ratio of lower femoral fractures increased between the ages of 70 to 89 in both men and women. The rate ratio was almost double in women of ages 85-89 compared to men within the same age range. Their findings suggest that elderly women in developed countries are more likely to be affected by distal femoral fractures. Our study exclusively disaggregated patients according to biological sex as this approach conforms to previous studies within this domain. Whether gender based differences exist remains a question especially with the use of estrogen and testosterone hormonal therapies for patients identifying to a different gender than their biological sex. Estrogen and testosterone play a role in bone biology and are related to bone stock [19]. However, any potential association between these therapies and the epidemiology of distal femoral shaft fractures is an area for possible future research.

Our study determines that high-energy mechanisms dominate the male population (70.5%, n=31) whilst low-energy trauma dominated the female population (82.7%, n=43). This was statistically significant (p<0.0001). These findings are consistent with reported literature elsewhere [3].

Our study found that fracture patterns 33-A1, 33-B1 and 33-B2 were the most common. Smith et al. determined 33-A1 and 33-C1 to be the most common in their study of 105 distal femoral fractures across four MTCs [20]. It is difficult to draw comparisons as patients below the age of 50 years were excluded from their analysis thus different etiology and patient populations can explain the variation. Pietu et al. also agrees with type 33-A1 being the most prevalent [14]. Our experience of intra-articular involvement (48.0%) is similar to what has previously been described elsewhere [2, 14, 20].

The majority of distal femoral fractures are managed operatively in adults. Even in elderly patients, non-operative management of displaced fractures is associated with poor outcomes due to increased risk of pressure ulcers, pneumonia, deep vein thrombosis and knee stiffness [21]. Butt et al. studied 42 elderly patients with displaced distal femoral fractures [22]. They concluded that operative management provided superior results compared to conservative management. Our figure of 73.6% requiring operation includes patients who had undisplaced fractures or were too systemically unwell to undergo operation. It is similar to the operation rate for distal femoral fractures at four other MTC in the UK [20]. Plate fixation dominated fixation techniques that reflect improved technology and mimics practice at other centers [10].

The link between low-case volume and increased risk of post-operative complications has been shown in the context of total hip arthroplasty [23]. This tentatively supports the case for patients with distal femoral fractures to be cared for in specialized trauma units with higher case loads and more experience. Further study into the epidemiology of distal femoral fractures at trauma units and smaller community hospitals is needed before definitive conclusions can be made.

Once operative management has been decided, obtaining the correct imaging is crucial. Initial anteroposterior (AP) and lateral radiographs of the knee and distal femur are important and provides valuable information about the injury (Figs. 7 and 8). Fractures around the distal femur are typically shortened and rotated and therefore traction radiographs can be helpful. High-energy injuries mandate radiographs of the pelvis and ipsilateral hip in order to exclude the presence of fractures proximal to the knee.

All distal femoral fractures with intra-articular comminution and extension should undergo a Computer Tomography (CT) scan with 2D and 3D reconstructions. This will readily identify a coronal plane fracture (Hoffa fracture) (Fig. 9) that usually requires independent interfragmentary screw fixation. It also provides invaluable information on fracture configuration, size of bony comminution and bone stock (Figs. 10, 11 and 12) determining whether internal fixation is achievable. Current implant designs allow internal fixation in increasingly distal fracture configurations and primary distal femoral replacement is rarely performed.

Fig. (7). Use of plain radiographs to determine fracture configuration, size of bony comminution and bone stock; Anteroposterior Radiograph.

Fig. (8). Use of plain radiographs to determine fracture configuration, size of bony comminution and bone stock. Lateral Radiograph.

Fig. (9). CT Scan in Sagittal Section showing a coronal plane fracture of distal femur (Hoffa Fracture).

Fig. (10). Use of CT Scan to determine fracture configuration, size of bony comminution and bone stock; Coronal Section.

Fig. (11). Use of CT Scan to determine fracture configuration, size of bony comminution and bone stock; Sagittal Section.

Fig. (12). Use of CT Scan to determine fracture configuration, size of bony comminution and bone stock; Horizontal Section.

The AO/OTA classification mentioned previously highlights what fixation modality is required. Completely undisplaced 33-A1.1 fractures can be managed non-operatively with the affected limb placed in either a long leg cast or a hinged knee brace, however operative stabilisation is recommended to allow for early motion and rehabilitation. All other 33-A1, A2 and A3 fractures should be treated surgically unless the patient is medically unfit for an operation. For all 33-A fractures the option of closed reduction and minimally invasive submuscular fixation exists. Fixation devices in these circumstances are dynamic condylar screws (DCS), less invasive stabilization systems (LISS) or locked condylar plates (LCP) [24, 25]. Depending on the fracture pattern, retrograde IM nailing may also be used once closed reduction is achieved. In our experience, patients presenting with a ‘floating knee’ (concomitant ipsilateral tibial shaft fracture) should be managed with IM nailing as this allows access to both operation sites through a single incision. If an open approach is necessary, placement of a condylar locking compression plate or angled blade plate is standard practice. The use of these techniques in extra-articular distal femoral fractures has been well described in the literature previously [26].

For fractures with intra-articular extension (33-B and 33-C), open reduction and internal fixation with restoration of the articular surface and the relationship of the distal articular segment to the femoral shaft is recommended. Preference is for fixation utilizing an anatomically contoured lateral locking plate for angular stability. This offers a more biomechanically stable construct under physiological loading and is particularly helpful in osteoporotic bone [16]. A combination of partially threaded cancellous, cortical and headless compression screws are utilized in the metaphyseal portion to achieve articular congruity. Occasionally a headless compression screw buried in the articular cartilage is required in the sagittal plane to hold a coronal plane fracture. In newer generation multidirectional locking plates the locking screws can be directed through an arc of 20 degrees. This allows the surgeon to precisely direct screws thus avoiding metal conflict with other areas of distal fixation and thereby increasing stability with multi-planar fixation producing reliable results (Figs. 13 and 14) [27].

Fig. (13). Use of multidirectional locking plate and multidirectional screws to achieve stable fixation; Anteroposterior Radiograph.

Utilizing a radiolucent table that allows unobstructed fluroscopy of the whole femur is recommended. Place the patient in supine position with a bolster under the ipsilateral hip allowing the leg to lie in neutral rotation. Prepare and drape the entire leg. Use a radiolucent triangle under the thigh to help position the leg. Use a sterile tourniquet to allow access to the shaft of the femur. It is important to ensure unobstructed high quality AP and lateral imaging is achievable before starting the case.

Utilize a direct lateral approach for most intra-articular distal femoral fractures. Distally curve the incision anteriorly and incorporate a lateral parapatellar arthrotomy. The advantages of this approach include the ease of plate application, the ability to reduce the metaphyseal component and it’s extensile nature. To visualize the medial articular surface the approach can be extended distally to sublux the patella medially and the option to perform a tibial tubercle osteotomy can allow complete visualization of the articular surface in the complex 33-C2 and 33-C3 fractures.

Fig. (14). Use of multidirectional locking plate and multidirectional screws to achieve stable fixation; Lateral Radiograph.

In treating 33-C2 and 33-C3 fractures a pre-operative CT and adequate articular exposure is the key to accurate reduction. Indirect or percutaneous reduction and fixation techniques are not recommended because the goal of treatment is achieving anatomical reduction of the joint cartilage and stable fixation to allow early joint mobilization and rehabilitation. Hoffa fragments are addressed first by placing pointed reduction clamps perpendicularly across the fracture within the exposure. Upon achieving anatomical reduction the fragment is provisionally held with Kirschner wires (K-wires). At least two AP interfragmentary compression screws are used to control rotational forces and should be placed away from the weight bearing area of the articular cartilage. The screw heads must be countersunk below the cartilage surface to avoid impinging on the patella. Use variable pitch headless compression screws or countersunk partially threaded cancellous screws. Following fixation of Hoffa fractures, each condylar segment must be de-rotated and reduced using multiple k-wires or a pointed reduction clamp. Due to the trapezoidal nature of the distal femur and occasional loss of bone the reduction can appear anatomical at one point but mal-reduced at another point. Once anatomical reduction has been achieved, an interfragmentary compression screws should be inserted from lateral to medial to compress the femoral condyles. Care must be taken to place these screws anteriorly or posteriorly to avoid screw conflict with the distal locking screws of the plate.

Once stable fixation of the articular segment has been achieved, it is reduced and fixed to the femoral shaft. In simple fracture patterns direct visualization with lag screw fixation or compression plating can be utilized. In more complex fracture patterns (AO 33-C2 and 33-C3) with metadiaphyseal comminution (Figs. 10 and 11) the goals of treatment are to restore length, rotation and alignment of the distal articular surface to the shaft of the femur with minimal disruption to the fracture fragments. This reduces the risk of devascularisation, subsequent non-union and implant failure. Here a pre-contoured lateral distal femoral locking plate is used to bridge the area of metadiaphyseal comminution. Use a plate length that spans three times the length of comminution. In restoring the coronal alignment of the femur the pre-contoured plate can be useful once the plate is “reduced” onto the bone. Length, rotation and sagittal alignment can be more difficult to restore and is achieved through manual traction and manipulation of the distal segment with large diameter k-wires or a 5mm Schantz pin to joystick. A femoral distractor placed proximally in the shaft and into the distal articular block can be helpful to maintain traction, restore rotation and maintain sagittal alignment long enough to allow plate application to restore coronal alignment.

As with all articular fractures, early range of motion and rehabilitation is key to preserving joint function. Therefore lower extremity range-of-motion exercises and gait training are advocated to commence on the first post-operative day. This rapidly progresses towards a physical therapy exercise program to improve knee range of motion and quadriceps function. Most patients are fitted with a hinge knee brace during the first 6 weeks of ambulation. For the complex 33-C2 and 33-C3 fractures, toe-touch weight bearing is recommended for 10 to 12 weeks. Sutures are removed at two weeks and patients are seen for clinical examination and radiographs at 6 weeks. Patients are radiographically assessed again at 12 weeks for evidence of callous and whether weight bearing can commence. Subsequent review is required every two to three months until clinical and radiographic union is achieved.

The use of hospital coding records to derive cases for this study runs the risk of omissions. Incomplete electronic medical records can also affect elements of data collection. To ensure completeness of data capture, several different hospital databases were used to identify and independently confirm cases. As an unblinded observational study, there is risk of unintentional bias in interpreting radiographs. As mentioned previously, sex-based analysis was conducted in disaggregated data. There is the assumption that any differences between gender and biological sex are irrelevant in the context of sustaining distal femoral shaft fractures.