Folded Free Vascularized Fibular Bone Graft for Segmental Femoral Bone Defect: a Retrospective Report


 ObjectiveVascularized fibular bone graft is an efficient method for various segmental bone defects. The objective of this report is to introduce our experience of folded free vascularized fibular bone graft for segmental femoral bone defect.Patients and methodsClinical data collected by surgeons and Hospital Information System (HIS) system were screened respectively. Cases with segmental femoral bone defect repaired by folded free vascularized fibular bone graft were collected. Clinical data including demographic characteristics, defect size, coinfection, perioperative treatment and imaging data during follow up were all collected for analysis.ResultsTwelve patients (10 males and 2 females), aged from 6 to 58, were included in this report. The defect range was 3 to 10 cm, with an average of 6.2 cm. Three cases were complicated with infection, the others were not. Folded free vascularized fibular bone graft were harvested for the reconstruction of segmental femoral bone defect. The grafts were fixed with plates in 9 cases and external fixators in 3 cases. All grafts healed uneventfully with an average healing time of 5.2 months (range 4~8 months). Internal fixation failure occurred in one case. The follow up time ranged from 15 to 130 months (average 58.3 months).ConclusionFolded free fibula graft is one of the optional methods for segmental bone defect of femur. Through this method, patients can achieve one-time operation to reconstruct the bone defect of the affected limb.


Introduction
The clinical treatment of segmental femoral bone defect is di cult. As the main load-bearing bone of lower limb, the reconstruction of bone defect needs to consider the length of bone defect, the thickness of bone and the duration of disease [1] . Generally, segmental bone defects could be managed by several methods, such as Illizarov technique, induced membrane technique and bone graft [2] . Illizarov technique, which needs a long treatment course, has been criticized for related soft tissue and neurovascular complications. Induced membrane technique can repair long femoral defect, but it needs staged operation [3] . Moreover, this method is not indicated for segmental bone defect with infection [4,5] .
Autologous bone transplantation, especially autologous bone graft with blood supply, has been proven a better solution for the treatment of segmental bone defects [6] . We have reported the complex tibial bone, soft tissue, and main artery segmental defects reconstructed by ow-through free bula osteocutaneous ap in one stage [7] . In recent years, folded free vascularized bula graft was applied to repair segmental defect of femur. And good results were achieved. Thus, we retrospectively review the cases and conduct this report.

Inclusion and exclusion criteria
Patients who met the following criteria were included: (1) patient diagnosed as femoral bone defect; (2) treated by folded free vascularized bula graft; (3) patient with complete medical history and follow-up information.
Patients were excluded for the following reasons: (1) femoral bone defect treated by other methods: including induced membrane technique, Illizarov bone transport, non-vascularized bone graft and one barrel bula graft; (2) severe infection of the limb out of control; (3) composite tissue defect; (4) incomplete medical history or follow-up information.

General information of included cases
A total of 12 cases of femoral bone segmental defect treated by folded free vascularized bula graft were included. The general information was listed in Table 1. Ten were male while two were female. The average age was 25.8 years (6 to 58). Seven cases were caused by wide resection of the tumor, three by radical debridement of posttraumatic osteomyelitis. The defects were located in the femoral shaft in 7 cases and distal femur in 3 cases. The average length of defect was 6.2 cm (3 to 10 cm). The bular vessels were anastomosed with the descending branch of the lateral circum ex femoral artery in 10 cases, and the bular vessels were anastomosed with the lateral superior genicular vessels in 2 cases.
The vessels were anastomosed end to end.

Preoperative management
After admission, routine preoperative examination, anteroposterior and lateral view lm of the femur were performed. CT and MRI were performed when necessary to identify bone tumor or in ammatory boundary. Infection status of the infectious bone defect should be determined with routine blood test, Creactive protein and erythrocyte sedimentation rate. For severe infection and poor local soft tissue conditions, multiple debridement operations are needed until the infection is controlled. Appropriate antibiotics can be selected according to the results of wound secretion culture.

Surgical technique
The patient was placed in supine position. For the femoral bone tumors, the lesions were either excised or performed with extended resection according to the nature of the lesions. For infective bone defect, rst of all, radical debridement was conducted until no obvious local in ammation exist. Bone reconstruction surgery is performed at least 3 months later. The length of femoral defect was measured. Different recipient vessels were selected according to the location of the femoral defect. If it is located in the middle or proximal femur, the descending branch of lateral circum ex femoral artery is separated. If the defect is located at the distal femur, the lateral superior genicular vessels are dissected. The recipient vessels are selected individually according to previous surgeries and local soft tissue coverage.
A longitudinal incision was made on the posterolateral side of the proximal lower leg. The gastrocnemius muscle was separated to expose the bular vessels, and the proximal end of the bula was cut off. The exor pollicis longus was exposed. The interosseous membrane was excised, and the bula was pulled outwards. The muscle sleeve of 0.5-1 cm was reserved around the periosteum. According to the length of the recipient area, the distal bula was cut off and the bular vessels were cut off.
The bony part of bula ap was broken in the middle, and the integrity and continuity of soft tissue and blood vessels were preserved. The folded graft was placed in the defect of femur. Other bone substitutes were used when necessary. The arteries and veins were anastomosed to the vessels of the recipient area successively. Great saphenous vein graft for vascular bridging was adopted when there is a vascular defect. The bony structure was xed with plate or external xator. Generally, for infectious bone defect, if there is still low-grade infection after multiple debridement, external xator should be used. If the local infection has been controlled after debridement, the plate can be selected to provide more stable xation.
For infective defect, vancomycin arti cial bone can be used to prevent infection recurrence.

Postoperative treatment
Smoking was strictly prohibited in the surrounding environment of patients, and local warmth was maintained. Anti-in ammatory, anti-vasospasm and anticoagulant therapy were given after operation. Patients began active hip and knee joint activities after operation to avoid stiffness. Immediately after the operation and every 2-3 months after the operation, the anteroposterior and lateral lms of the affected femur were reviewed to evaluate the fracture healing. The postoperative complications were recorded.

Results
Finally, twelve patients, with 10 males and 2 females, were included in this report. One patient was collected by the surgeon while the rest were retrieved from the HIS system. The demographic characteristics and the follow up information were showed in Table 1. The age range of included patients was 6 to 58 years, with an average of 25.8 years. The defect range was 3 to 19 cm, with an average of 6.2 cm. Three cases were complicated with infection, the others were not. Folded free vascularized bular bone graft were harvested for the reconstruction of segmental femoral bone defect. The grafts were xed with plates in 9 cases and external xators in 3 cases. All grafts healed uneventfully with an average healing time of 5.2 months (range 4 ~ 8 months). Internal xation failure occurred in one case. The follow up time ranged from 15 to 130 months (average 58.3 months).

Case 1
A 25-year-old man with chronic osteomyelitis of the left femur was admitted from another hospital. After several debridement operations, bone defects were left in the femur. Six months after the local infection was controlled, debridement and folded vascularized bular graft with internal xation were performed.
The peroneal vessels were anastomosed with the descending branch of lateral circum ex femoral vessels. After 8 months, the patient fell down again and felt the pain along the thigh. The X-ray showed internal xation failure. Then the reconstructive procedure, including xation exchange and iliac bone graft, were performed. Now the fracture healed well, with slightly limited knee exion. The images of this patient were showed in Fig. 1.

Discussion
This report included segmental femoral shaft defects reconstructed with folded free vascularized bula graft. The patients were followed for 15 to 130 months. All patients achieved bone union and the union time ranged from 4 to 8 months. Internal xation failure occurred in one case. No infection and other complications were recorded. Though many methods have been con rmed e cient for the management of segmental femoral bone defect, it is still challenging for the surgeons. Currently, three methods are commonly used: induced membrane technique, Illizarov technique and vascular bone graft. Induced membrane technique has been con rmed e ciently for segmental defect reconstruction [8] . The bone union rate was 87.5% for reconstruction after bone tumor resection [9] . However, the results are uncertain for infectious bone defect.
Morris [10] reconstructed 12 tibial bone defects with Masquelet technique and followed for 675 days. Bone union was achieved in only 5 patients after two-stage procedure. Five patients suffered infection and two cases required amputation. Renaud [4] also reported a similar bone union rate (8/19) for the management of septic non-union of the tibia. The additional surgery was required for 11 of the 19 cases.
Segmental femoral bone defects would also be repaired by Ilizarov bone transport. However, it is still challenging and may end in failure especially for periarticular bone defect [11] . Tong compared the Ilizarov bone transport and Masquelet technique for the management of infected bone defect of lower limb.
Patient by Ilizarov bone transport required longer external xation time but gained worse functional outcomes, even though the bone union results showed no signi cant difference [12] .
In our case series, 3 of them were infectious bone defects and the bone defect located in femoral shaft.
Thus, we chose the vascularized free bula graft for the reconstruction. On one hand, the cortical bone together with internal xation provided su cient biomechanical support for the lower limb. On the other hand, abundant blood supply of the graft enhanced the anti-in ammatory and antibacterial activity. Meanwhile, the blood supply with the graft also accelerated the healing process of end of donor and recipient which was hindered by the surrounding hypovascular brotic tissue.
Erdmann et al [13] introduced a novel ipsilateral free bula transfer for management of a segmental femoral bone defect. With this method, vessel preparation at the recipient site for microvascular anastomosis is unnecessary, while extensive exposure at the donor site is needed. It provided an optional method for the reconstruction of femoral bone defect, especially for recipient site with multiple surgeries, healthy vessels are not available.
Free vascularized bula grafts, for its high bone healing potential and biomechanically strong support, have been the effective treatments for the management of segmental bone defect longer than 6cm.
Lee [14] reported free vascularized bula grafts in 7 patients with segmental femoral bone defects after tumor resection. The defects were reconstructed with one-barrel bula ap with a lateral locking plate. Stress fracture occurred in two patients. However, bone union was obtained in all patients. The mean bone union time was 24 months, the delay union might be affected by the multimodal treatment for the tumors. No donor site complications were reported.
So, which method should we choose, the one-barrel, folded-barrel or double bula grafts? It has been reported that the incidence of stress fracture for one-barrel bula grafts ranging from 20-40% within 1 year, especially for the bone defect of lower extremity [15,16] . One-barrel bula graft provides su cient biomechanical and bone support for long bone defects including humerus, radius and ulna [17] . Double or folded bula grafts were chosen when intermediate stress loads were applied to the resection site [18] . This method did not increase the number of microvascular anastomose, however, the twice bula support greatly increases the strength of local mechanical support [14] . Liang [16] reconstructed the subtrochanteric bone defects with folded free vascularized bular grafts. All cases achieved bone union and the average bone union time was 5.4 months. The results showed that FVFG was an e cient method in achieving bone union, reducing risks of complications including stress fracture and malunion. Thus, for the reconstruction of femoral bone defects, folded or double-strut bular grafts transfer may be more appropriate by withstanding the high mechanical stress.
The conventional concept is that vascularized bone graft is best indicated for bone defects without in ammation in aseptic wounds. However, the timing of vascularized bone graft for open fractures with bone defects is still controversial [16,19] . The premise of one-stage vascularized bone graft is limited contaminated wound, the radical debridement and the effective antibiotics control. If this premise could not be achieved, it is suggested that the vascularized bone graft should be carried out after the wound healing for 3-6 months. For the management of chronic infectious bone defect, elimination of infection is the rst priority. Debridement combined with antibiotics will transform infectious bone defect into noninfectious bone defect. Three to six months after the elimination of infection, bone defects could be managed by vascularized bone graft.
This report is a retrospective review of the clinical cases. Some de ciencies should not be ignored. First, owing to the lower incidence and the diversity of the treatments, only 12 patients were included. This may primarily con rm the e ciency and safety of the folded free vascularized bula bone graft. Secondly, although rigid including and excluding criteria were followed, clinical heterogeneity including different injury factors, infection, defect range and location should also be noted. Finally, there is no control group. This is partially due to no golden standard treatment for femoral bone defect.  Table   Table 1 The general information of included cases.