We retrospectively reviewed 20 patients who were admitted to our hospital between January 2005 and October 2009 for extra-articular distal femur fracture with osteoporosis and tracked for more than 2 years. Bone mineral density was evaluated with biplanar radiographs and dual-energy X-ray absorptiometry (DEXA) scanning in the hip and lumbar spine. In all of our cases, the lowest T-score was less than -2.5 standard deviation. Of the 20, 16 patients were managed with retrograde intramedullary nailing (AIM titanium supracondylar nail, Depuy ACE, Leeds, UK). Cement augmentation or shape memory alloy (Bio-smart) was combined with retrograde intramedullary nailing in 13 patients to improve mechanical stability. We included these 13 patients in this study (Table 1). Their mean age was 79 years (range, 68 to 90 years) and all were females. Four cases were type A1 and 9 cases were type A3 according to the AO Foundation and Orthopaedic Trauma Association (AO-OTA) classification system.10) The Institutional Review Board of our hospital reviewed and approved this study.

All operations were performed by one orthopedic surgeon. The patient was placed in the supine position on a radiolucent operating table. A midline incision and medial parapatellar approach were used. A guide wire was inserted under C-arm fluoroscopy and the medullary cavity was reamed. When we inserted distal interlocking screws, we checked the bone stock quality in the distal fragment. We added cement augmentation or shape memory alloy, if rigid fixations between distal fragment and distal interlocking screws were not achieved due to configuration and location of the fracture or severe comminution. If the fracture line was located above the flare of the femoral condyle and the configuration of the fracture was spiral or long oblique, we used shape memory alloy (Fig. 1, Table 1). Even in the A3 type fracture, if the configuration of major fragments was spiral or long oblique, we applied shape memory alloy. When we applied shape memory alloy, we paid close attention to preserve periosteum and applied shape memory alloy outside of the periosteum. To improve mechanical stability of the bone implant construct and to prevent pulling out of the interlocking screw, we used cement augmentation (Figs. 2 and 3, Table 1). In the A3 type fracture with anterior cortical comminution, we also used cement augmentation (Fig. 3). From the 1st postoperative day, joint exercise using a continuous passive motion machine was started and weight bearing was allowed at the 6th postoperative week.

Postoperative assessments were done on an outpatient basis at the 4th, 8th, 12th, and 24th postoperative week and annually thereafter. Clinical fracture union was defined by bridging callus formation on the anteroposterior (AP) and lateral radiographs and pain free weight bearing. If we used cement augmentation for filling in the anterior cortex with severe comminution, we evaluated bridging callus formation in the medial and lateral cortices on the AP radiograph and posterior cortex on the lateral radiograph. The alignments of the distal femurs were measured on the postoperative 1 year radiographs (shortening, varus/valgus, antecurvatum/retrocurvatum). And the measurements were scored and assessed as showed in Table 2.11) Tegner and Lysholm activity score was used for functional assessments.12)

The postoperative follow-up period was 30 months (range, 24 to 36 months). The average time to clinical union was 13 weeks (range, 10 to 15 weeks). In the assessment of the radiographic alignment, the average score for shortening was 3.8 (range, 2 to 4). That of varus/valgus alignments was 3.4 (range, 1 to 4) and that of antecurvatum/retrocurvatum was 3.6 (range 2 to 4). In 12 of our cases, the total alignment scores were excellent. At the last follow-up, the mean range of motion was 116° (range, 110° to 125°). The average pre-injured functional score was 4.2 (range 2 to 5) and the average functional score at the 1 year postoperative time point was 2.6 (range, 1 to 5).

Postoperatively, there were no complications such as infection, neurovascular injury and implant failure. All patients were satisfied with the surgical results.

Distal femur fracture with osteoporosis is one of the unsolved problems in orthopedic and trauma surgery. The incidence of this fracture is bimodal, appearing mostly in young men and old women.13) Recently the incidence of osteoporotic knee fractures has been rising,3) and more than 50% of patients with distal femur facture occur in elderly patients.2) In the management of distal femur fracture with osteoporosis, early rehabilitation is very important for satisfactory surgical results since most are elderly patients. For early rehabilitation, mechanical stability should be maintained. There are several surgical options such as an angled blade plate, a locking plate and retrograde intramedullary nailing for stable fixation and early exercise. Open reduction and plating is advantageous in achieving anatomical reduction because a direct view of the fracture site is possible during surgery. However, there is a possibility that an invasive incision and soft tissue stripping will cause complications such as nonunion, delayed union and infection and might prevent early rehabilitation. There also have been reported several complications of healing including nonunion, delayed union, and implant failure in the management of distal femur fracture with locking plates.14) If there is severe comminution in the distal femur fracture, internal fixation with locking plate is very difficult technically.

Retrograde intramedullary nailing is a good surgical option for distal femur fracture. We can avoid invasive soft tissue dissection and minimize secondary damage of the blood circulation at the fracture site. In a previous biomechanical study, intramedullary nails had significantly higher stiffness and significantly lower micromotion across the fracture gap with axial compression than with a dynamic condylar screw or a locked condylar plate.4) Therefore, early rehabilitation is possible with the use of intramedullary nailing. However, in the osteoporotic patient with severe comminution, it is very difficult to achieve sufficient implant anchorage. In the management of distal femur fracture, distal locking has a major impact on the implant anchorage in osteoporotic bone.6) Tejwani et al.15) studied the effect of locked distal screws in retrograde nailing of osteoporotic distal femur fractures. They concluded that the locked distal screw nails exhibited less fracture collapse and anterior and medial translation of the nail at the fracture site than unlocked distal screw nails. Ito et al.16) compared distal locking with conventional locking bolts and a bladelike device with retrograde intramedullary nailing for osteoporotic supracondylar fractures. In their study, interlocking with a bladelike device was 41% stiffer and 20% stronger than that with conventional locking bolts, and there was no gross deformation in the bladelike device after biomechanical testing. If we cannot achieve mechanical stability with retrograde intramedullary nailing, we need to add procedures for rigid fixation. For this, cement augmentation has been introduced.7,8) We can not only achieve mechanical stability with cement augmentation but also prevent the interlocking screw from pulling out. Shape memory alloy is also one of the good surgical options for reinforcing a bone implant construct when we use retrograde intramedullary nailing for distal femur fracture. At cold temperatures, the nature of shape memory alloy is more flexible and it becomes hardened at body temperatures. The advantage of shape memory alloy is that it is very easy to manipulate and it can apply compression force between fractured segments.

Several previous studies5,11,17,18) reported good results with retrograde intramedullary nailing for distal femur fracture. In a series of 44 consecutive patients with 46 distal femur fractures,11) the final union rate was 95% and a mean union time was 17.5 weeks. However, there were three patients with a loss of reduction and two of them had a re-operation. Gurkan et al.17) presented 16 patients with distal femur fracture treated with retrograde locked intramedullary nailing. The mean time to union was 25 weeks and functional results using the modified Hospital for Special Surgery knee rating scale were satisfactory. However, among their series, joint range of motion was 80 degrees in four knees (24%) and below 80 degrees in one knee (6%). Bei et al.19) reported that several factors may affect knee joint function recovery including age, preoperative the American Society of Anesthesiologists classification, fracture type, reduction quality, whether or not there was continuous passive motion functional training, and postoperative complications. However there is a possibility of complication such as infection, septic arthritis of the knee, knee pain and malunion. In the meta-analysis performed by Papadokostakis et al.,20) the incidence of infection was 1.1%, and that of septic arthritis of the knee was 0.18%. The rates of knee pain and malunion were 16.5% and 5.2%. However, in our cases there were no complications such as infection, septic arthritis, deep vein thrombosis, and implant failure. Radiologic and functional results were also satisfactory.

Even though the number of patients in our study was small and the study retrospective, retrograde intramedullary nailing seems to be a good surgical option for distal femur fracture with osteoporosis. Fixation with cement augmentation and/or shape memory alloy promotes fracture healing and early rehabilitation.