Surgical Technique: Management of a Pathological Fracture in the Femoral Neck: Case Report and Literature Review

Authors: Ali Hashem, Zaid AlShammari, Ahmed Altuwaim, Nouf A. Altwaijri

Abstract

The unicameral bone cyst (UBC) is a benign lesion that affects children and adolescents between 4 and 14 years of age. They are defined by an osteolytic cavity filled with serous fluid, enclosed by a thin fibrous membrane. Moreover, they are closely associated with skeletal growth and biomechanical stresses during development. Surgical management of UBCs is crucial, particularly in weight-bearing bones, to reduce the risk of pathological fractures and maintain structural stability. These surgical procedures (such as curretage and bone grafting) aim to restore bone stability, prevent recurrence, and enhance long-term functional outcomes. Studying UBCs provides insight into the natural history and behavior of benign bone lesions, emphasizing the importance of growth and mechanical factors in skeletal pathology. This case report seeks to present our experience in managing UBCs of the proximal femur in Riyadh, Saudi Arabia, focusing on the tips needed in the surgical technique that can aid surgeons in the management of such cases.

The unicameral bone cyst (UBC) is a benign lesion that affects children and adolescents between 4 and 14 years of age.^1^ These lesions predominantly involve the metaphysis of long bones, with the proximal femur and humerus being the most frequently affected sites.^2^ The incidence rate of UBCs is around 3% of primary bone lesions.^3,4^ UBCs are characterized by an osteolytic cavity filled with serous fluid, enclosed by a thin fibrous membrane. Moreover, they are closely associated with skeletal growth and biomechanical stresses during development.^5^ Clinically, UBCs are often asymptomatic and are only detected when complications arise. Around 85% of cases are diagnosed following the onset of pain that interferes with daily activities or after a pathological fracture.^6^ For example, UBCs are implicated in nearly 40% of pathological femoral neck fractures in pediatric populations.^7^

Although UBCs carry the risk of significant complications, many resolve spontaneously after skeletal maturity.^8^ From a diagnostic perspective, radiographic imaging plays a pivotal role. Plain radiographs typically reveal a centrally located, well-defined, osteolytic lesion in the metaphysis of long bones, without evidence of periosteal reaction or soft-tissue involvement. These features help differentiate UBCs from more aggressive bone lesions.^9^ Differential diagnosis of UBCs includes aneurysmal bone cysts, benign chondroblastoma, fibrous dysplasia, or enchondroma.^3^

The etiology of UBCs remains unclear, although multiple hypotheses have been proposed. Suggested mechanisms include blocked fluid drainage within the bone, nitric oxide–mediated processes, intramedullary venous obstruction, and localized bone resorption through lytic processes.^5,8^ Despite these theories, the underlying pathophysiology remains an area of active investigation.

Surgical management of UBCs is crucial in weight-bearing bones to reduce the risk of pathological fractures and maintain structural stability. Although asymptomatic lesions may be observed, surgical intervention is often required for fractures or cases where the cyst compromises mechanical integrity. Surgical techniques such as curettage and bone grafting, with or without internal fixation are common approaches, particularly for proximal femoral cysts.^2,10^ They aim to restore bone stability, prevent recurrence, and enhance long-term functional outcomes.

Studying UBCs provides insight into the natural history and behavior of benign bone lesions, emphasizing the importance of growth and mechanical factors in skeletal pathology. This case report seeks to present our experience in managing UBCs of the proximal femur in Riyadh, Saudi Arabia, focusing on the tips needed in the surgical technique that can aid surgeons in the management of such cases.

Cases Presentation

First Case

A 5-year-old girl presented to our emergency department complaining of right hip pain and limping for 3 weeks following trauma to her right lower limb. On examination, she was noticed to have right hip pain that worsens with hip rotation. Radiographic images showed a large right femoral neck lytic lesion extending to the trochanteric area associated with a stress fracture of the femoral neck with varus displacement (Figures 1 and 2). The patient’s family were then counseled for the need for surgical intervention, and the patient was taken to the operating room for further management.

$Figure 1: A, AP view of the pelvis showing a right femoral neck multiloculated lytic lesion extending from the epiphyseal plate to the trochanteric line associated with a discontinuity of the bony cortex (stress fracture) of the femoral neck with varus displacement. B, Frog lateral view of the pelvis showing a right femoral neck multiloculated lytic lesion extending from the epiphyseal plate to the trochanteric line associated with a discontinuity of the bony cortex (stress fracture) of the femoral neck with varus displacement$

$Figure 2: Magnetic resonance imaging coronal views showing a 1.5 × 2.8 cm nonaggressive, geographic, multilobulated, expansile lesion with a well-defined and thick sclerotic margin, and amorphous mineralized matrix, localized in the intertrochanteric region of the right femur with a medial femoral neck periosteal reaction suggestive of a healing fracture.$

Surgical Technique

Through a lateral approach to the proximal femur, dissection was carried down to bone. Using a drill over the anterior cortex of the trochanteric area, we opened a window and kept the lateral cortex intact for fixation, followed by curettage of the lesion exposing the femoral medulla distally and sampling for biopsy. Afterward, three wires sized 2 mm were drilled from the lateral cortex to the femoral head and stopped 5 mm away from the subchondral bone. Then, we bent the wire in a broad curve to prevent it from recoiling and varus displacement and added a circlage wire going through the femur bone to help stabilize it (Figure 3). Finally, the area of the lesion was filled with an allograft of bone. After closure, and given the patient's age, we applied a half spica for 6 weeks (Figure 4). If the patient was older and more cooperative, we could have proceeded without the spica (see second case). At 3 months, the spica cast was removed and images were taken (Figure 5).

Figure 3: AP (A) and frog lateral (B) views of intraoperative images postfixation.

Figure 4: AP (A) and lateral (B) views showing the pelvis 6 weeks postoperatively while still on spica cast.

Figure 5: AP view of the pelvis following spica removal.

Follow-Up

During follow-up, we noticed that the patient took longer to heal with the wires gradually shifting distally in the neck because of growth, which is the advantage of using smooth wires and not screws. Images taken at 1-year follow-up are shown in Figure 6. After 2 and a half years from the surgery, the bone healed completely, and the patient was taken to the operating room for removal of the implants as shown in Figure 7. The patient was followed up at 1 year after removal (Figure 8), where the femoral neck remodeled in a normal neck shaft angle. She had no stiffness, limitation in the range of motion, pain, or limping at her latest follow-up.

Figure 6: AP (A) and lateral (B) views of the pelvis at 1-year follow-up.

Figure 7: Lateral view following removal of implant.

Figure 8: AP (A) and lateral (B) views of the hip at 1-year follow-up after removal.

Second Case

An 8-year-old boy presented to emergency department complaining of right thigh pain which started around a month before presentation. The pain was sudden, progressive, and associated with limping. On examination, the patient had an antalgic gait with limitation in range of motion at the extremes because of pain. Imaging showed a right proximal femur lytic lesion (Figures 9 and 10). Similar to the previous case, the family were counseled for surgery and the patient was taken for surgical intervention where he underwent curettage, bone grafting and Kirschner wire fixation (Figure 11). Given the patient's age and his ability to understand and follow instructions, there was no need to put him on spica. Instead, he was given instructions to avoid weight bearing over the operated side for 6 weeks, followed by partial weight bearing for 8 weeks and then full weight bearing. The patient was followed up regularly in the clinic, and he had no complaints or limitation in range of motion or pain. He was taken for removal of implants at 1.6-year follow-up (Figure 12) after complete healing was confirmed on radiographs. He had no stiffness, limitation in range of motion, pain or limping at the latest follow up.

$Figure 9: AP (A), lateral (B) views of the pelvis showing an abnormal well-defined, relatively expansile lytic lesion in the medial aspect of the right femoral neck without a definitive fracture. The lesion extends from the epiphyseal plate to the subtrochanteric area.$

$Figure 10: Magnetic resonance imaging coronal view showing a 5.0 × 2.0 × 2.2 cm well-defined, relatively expansile and lytic lesion in the right femoral neck without an associated fracture.$

Figure 11: AP (A) and frog lateral (B) views of the pelvis postfixation.

Figure 12: AP (A) and lateral (B) views of the pelvis following removal.

Third Case

A 4-year and 9-month-old boy was referred to us from another hospital with a report of progressive right hip pain for 4 months. It interfered with his daily activities; he had difficulties in standing from sitting position and was constantly limping. Examination revealed an antalgic gait with limitation in the extremes of range of motion because of pain. Imaging showed a lytic lesion of the right trochanteric area measuring 23 × 29 mm occupying more than 90% of the width of the shaft (Figures 13 and 14). Similar to the first case, the patient underwent curettage, bone grafting, Kirschner wires, and tension band fixation with half spica (Figure 15). The patient was then followed up in the clinic where the half spica was removed at 6-week follow-up. Afterward, he was allowed to weight bear as tolerated. Around 10 months postoperatively, the patient fell and sustained a transcervical fracture of the femur (Figure 16) which we decided to manage conservatively given that the wires were stable, and the patient was allowed to bear weight. Currently, the patient is 1 year postfixation (Figure 17); his fracture healed because of the stable fixation of the wires, and he is doing well. He has no complaints of pain or limitation in range of motion. He is planned for removal after making sure the bone graft is taken well, confirmation of healing and ensuring no recurrence occurred.

Figure 13: AP (A), lateral (B) views of the pelvis showing a mildly expansile, lytic lesion with endosteal thinning and an internally thin septa within the right intertrochnteric and subtrochanteric regions of the femur with a medial proximal cortical breach.

$Figure 14: Magnetic resonance imaging coronal view showing a right femoral neck expansile lesion measuring 2.3 × 1.9 cm with mild bone marrow edema. No definitive fracture seen.$

Figure 15: AP view of the pelvis showing postfixation and application of spica.

$Figure 16: AP view of the hip showing the transcervical fracture.$

Figure 17: AP (A) and lateral (B) views of the hip at 1-year follow-up.

Discussion

Different types of treatments have been suggested for UBC. For example, Scaglietti et al^11^ concluded that steroid injections are less invasive and more effective treatment than surgery. Moreover, Intramedullary decompression and bone grafting is another popular treatment that has been done with various graft materials, for example, medical-grade calcium sulfate, demineralized bone matrix, and cancellous chips.^2,10^ A recent trend in surgical treatment for symptomatic UBCs has been toward less invasive curettage and injection of a bone substitute as described by Hashemi-Nejad and Cole^12^ and Mik et al^13^ has performed a minimally invasive surgical technique, including percutaneous decompression and using medical-grade calcium sulfate pellets as a graft. They worked on 55 patients, including seven patients with proximal femur cysts. Eighty percent of patients healed after one surgery and needed no further treatment. Chigira et al^5^ have introduced the multiple drill holes method because they believe that the cause of the cysts is obstruction of venous drainage. Therefore, their method decreases this internal pressure within the cyst. They tried it on seven patients, of whom four have completely healed, two had partial recurrence after healing, and one had no response to the treatment; they believe the Kirschner wires used for drilling can help drain the cyst through the holes. Li et al^14^ have compared autogenous bone marrow injection to titanium elastic intramedullary nailing on 46 patients, including 16 on the femur. The results showed 60.9% complete healing in the autogenous bone marrow method and 69.6% in titanium elastic intramedullary nailing, with a recurrence rate of 13% in both. Zhang et al^15^ compared intramedullary nailing with curettage and bone grafting to curettage and bone grafting alone. The results showed a 90% healing rate in the first group and 68.8% in the second group, suggesting that intramedullary nailing could be added to the curettage and bone grafting as a safe and easy way to increase the rate of treatment effectiveness. Scaglietti et al^16,17^ initially described the use of steroid injection for UBCs in 1974; 8 years later, Scaglietti et al^16,18^ reported long-term favorable results with this technique. Complete cyst obliteration was observed in 55% (83 of 163) of the cases; 76% of the patients needed at least a second procedure. Others also have reported on the Scaglietti technique, with variable success rates (32% to 80%).^12,16,18,19^

Our literature review revealed most cases were managed with curettage and intralesional injections or intramedullary/plate fixation. With scarcity of similar intervention to ours mentioned in only one case which was managed by Abdel Mota'al et al^10^ with curettage and Kirschner wire fixation.

As noted by van Geloven et al,^20^ the preferred management of such condition remains unclear; however, they have stressed the importance of balancing the treatment and avoiding under treating patients to avoid potentially demanding larger interventions and their complications. Adaş et al^21^ noted that using a 120° fixed-angle low-contact locking pediatric plate is a reliable option following decompression and lesion grafting.

Li et al^22^ concluded that prompt surgical intervention of these lesions when found is preferable to prevent fractures, which have occurred in 32% of their sample, and they noted a higher chance of complications occurring in addition to prolonged surgical time and increased blood loss intraoperatively. They have used biopsy, curettage, and bone grafting with FIN or LCP-PHP with Kirschner wires to fix these lesions.^22^ Hasan and El Saleh^23^ studied the outcome of curettage without internal fixation in pediatric patients with peritrochanteric benign bone lesions and found that curettage and external immobilization is an effective management option in terms of technicality with satisfactory results with regard to local tumor control and long-term functional and radiological results.

Moreover, many UBC cases present with fractures; however, there is no treatment algorithm yet.^24^ Dorman and Pill^25,26^ recommend using a pediatric hip screw and side plate on top of the curettage and bone grafting in cases where the lateral buttress is compromised with postoperative spica application in selective cases. There are many other treatment options such as decompressing the cyst, bone grafting, and instrumentation.^24^

We chose our method for multiple reasons. First, it is a relatively angular stable fixation that prevents varus collapse of the femoral neck. Moreover, the smooth wires will not affect the epiphyseal epiphyseal plate and fixing them to the femoral shaft using tension prevents wire migration. Second, this is a rotation-stable fixation when comparing it to the elastic nail. Third, we found this to be the best way to fix cases where there is a huge cyst involving most of the femoral neck. Finally, it is a very simple and easy technique that can be done using a single incision. We hope that our case can shine a light on this mode of fixation and hope to see it implemented more in the future.