Review of 16 cases of aneurysmal bone cyst in the proximal femur treated by extended curettage and cryosurgery with reconstruction using autogenous nonvascularized fibula graft

Abstract

Background:

Aneurysmal bone cyst (ABC) is an aggressive benign lesion that may sometimes be difficult to treat. Lesions that occur in the proximal femur require to be addressed aggressively because of the high rate of local recurrence and the risk of fracture. Few articles report the experience of management of ABC in the proximal femur. This location presents a surgical challenge due to its anatomical and biomechanical peculiarity.

Methods:

We retrospectively reviewed 16 cases with ABC in the proximal femur that were treated in our institution between 2005 and 2014, utilizing extended curettage and liquid nitrogen as adjuvant therapy and reconstruction using nonvascularized autogenous fibular strut graft. The mean follow-up period was 50.5 months. Five cases presented as recurrent cases, while four cases presented with pathological fractures.

Results:

The functional score ranged from 70 to 90 on modified Musculoskeletal Tumor Society score with a mean score of 81.25, which is considered to be excellent function. Time for graft incorporation ranged from 10 to 12 weeks. One case got local recurrence, and one case got early surgical site infection.

Conclusions:

Extended curettage and cryotherapy represent a recommended approach for management of ABC in the proximal femur with favorable results.

Keywords

aneurysmal bone cyst cryosurgery liquid nitrogen proximal femur

Introduction

Aneurysmal bone cyst (ABC) was first described by Jaffe and Lichtenstein in 1942.¹ Nevertheless, its nature and thus optimum line of treatment are still debatable.² Despite presenting mainly as a primary lesion, secondary ABC has been suggested as a result of hemorrhagic degeneration of several lesions, including giant cell tumor, chondroblastoma, osteoblastoma, non-ossifying fibroma, fibrous dysplasia, and several other tumors.^1

–7

ABC commonly presents in the first two decades with slight female predominance. Main sites are the femur, tibia, humerus, spine, and pelvis. The tumors are usually metaphyseal and eccentric.²

Rare cases of malignant transformations of ABCs have been reported, and they were associated with the use of adjuvant radiation in treatment.⁸

As the biological behavior of ABC tends to be active to aggressive, surgical approach is the mainstay of treatment. Intralesional procedures, such as curettage with or without bone marrow injection, and bone grafting are the most commonly used treatment options. Currently, less invasive treatments, including cryotherapy, intralesional injection of calcitonin, methylprednisolone, or sclerosing agents, are commonly used.⁹

In the rare cases of indolent ABCs, spontaneous healing may occur. Patients with spontaneous healing are relatively older than typical patients with ABCs.^9
–11

Selective embolization is used in surgically inaccessible sites and as an adjuvant to surgical treatment to reduce intraoperative blood loss and facilitate curettage especially in huge lesions. The use of radiotherapy in these situations has been discarded to avoid malignant transformation.⁹

Several studies have showed the peculiar and complex vascular anatomy of the hip^12

–15 as well as the high liability to pathological fracture together with difficulty in full exposure of the lesion rendering surgical management of this lesion in the proximal femur a rather challenging procedure.¹⁶

In this study, we represent our experience in management of ABC in the proximal femur using extended curettage and liquid nitrogen (LN) as adjuvant. As far as we know, this is the largest presented series with homologous pathology and line of treatment in this peculiar location.

Methods and materials

This research has been approved by the institutional review board.

In our institute, the current protocol for management of active and aggressive benign bone lesions is to use LN as adjuvant therapy together after extended curettage, giving us the advantage of preserving as much skeletal support as possible and minimizing the need for major reconstructive techniques.

In this study, we retrospectively reviewed 16 cases with ABC of the proximal femur that were managed by this protocol. The study reviewed patients treated by this technique in our institution over the period from 2010 to 2015. These were 11 primary cases (Figure 1) and 5 recurrent cases. Ages between 7 years and 32 years. Four cases presented with pathological fractures (Figure 2).

Figure 1.

(a) Case 3: presenting X-ray of ABC involving the neck of the femur; (b) case 3: immediate postoperative X-ray showing reconstruction with fibular strut graft; and (c) case 3: last follow-up X-ray, 60 months postoperatively. ABC: aneurysmal bone cyst.

Figure 2.

(a) X-ray of case 15 presenting with pathological fracture; (b) MRI of case 15 presenting with pathological fracture; (c) case 15: postoperative X-ray after curettage, bone graft, and ostesynthesis in another hospital; (d) case 15: X-ray showing recurrence 8 months postoperatively; (e) case 15: CT scan showing recurrence 8 months postoperatively; (f) case 15: X-ray immediately postsurgery after extended curettage, applying LN and revision of fixation; (g) case 15: X-ray; last follow-up 64 months postsurgery; AP view; and (h) case 15: X-ray; last follow-up 64 months postsurgery; lateral view. LN: liquid nitrogen; AP: anteroposterior.

Inclusion criteria: Patients with primary or recurrent ABC lesions in the proximal femur with radiological findings predicting a well-contained cavity, with at least 50% of the bone circumference intact or with fine breaches that can be sealed with gel foam.

Exclusion criteria:

Lesions lying less than 5 mm from the epiphyseal plate in skeletally immature patients.

More than 50% circumference cortical destruction yielding an uncontained cavity.

The surgical technique used is discussed subsequently. Watson Jones approach¹⁷ was utilized in all cases.

Exposure

After exposure, a cortical window of the size of the longest longitudinal dimension of the tumor is made. To minimize the additional bone loss, the tumor is approached through the retained thinned or destroyed cortex. The window was made elliptical, with its axis parallel to the long axis of bone in order to reduce the stress riser effect.¹⁸

Curettage

All gross tumor tissues were removed with hand curettes. After the neoplastic tissue was curetted away from the wall of the lesion, high-speed burring was done in order to achieve an extended curettage.

Cryoablation

Before introduction of the LN, bony perforations were identified and sealed, and the surrounding skin, soft tissues, and neurovascular bundle were protected by mobilization and shielding with Gel foam.

Using the open system technique, LN was poured through a stainless steel funnel into the tumor cavity. The surrounding soft tissues were continuously irrigated with warm saline solution to decrease the possibility of thermal injury. In each cycle, LN was left in the cavity until it has completely evaporated. Each cycle lasted 1–2 min and was proportional to the volume of poured LN. Spontaneous thaw was then allowed to occur. Two freeze–thaw cycles were administered, at the end of each of which the cavity was irrigated with warm saline solution.

Reconstruction

In all cases, biological reconstruction was done using autogenous nonvascularized fibular strut graft to reconstruct the resulting defect.

Internal fixation was done in all cases as they met the criteria recommended by Jaffe¹⁹ which are those affecting at least 50% of the bone cortex of the femoral neck or with a diameter not less than 2.5 cm, tumors, tumors causing pain or deformity, and tumors likely to result in pathological fracture.

The mean time for surgery was 120 min (90–150 min), and average blood loss was 450 ml (200–700 ml).

In patients presenting with pathological fractures, we utilize a period of immobilization for 4–6 weeks to help reform a contained cavity, so as to facilitate curettage and pouring LN into the lesion without risking leakage and harming the surrounding soft tissue.

Patients were followed up every 2 weeks for the first 2 months, then monthly till union was evident, then every 3 months for the following year, and then every 6 months.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

For this type of study, formal consent is not required.

Results

The study entailed 16 cases, 6 women and 10 men. Ages of cases ranged between 7 years and 32 years with a mean age of 14.9 years.

Five cases presented as recurrent cases after being operated in other centers representing 31.25% of the cases.

Four cases presented with pathological fractures (25% of the cases). Follow-up period ranged from 24 months to 80 months, with a mean of 50.5 months.

In all cases, retrieved specimen was sent for histopathological analysis, which confirmed the diagnosis.

Time for graft incorporation ranged from 10 to 12 weeks after which graduated weight bearing was allowed.

One case got recurrence 11 months postoperatively and was treated by the same technique.

One case got surgical site infection 3 weeks postoperatively, which was treated by debridement and antibiotic according to culture and antibiotic sensitivity.

Final evaluation was done using the Musculoskeletal Tumor Society (MSTS) scoring system.²⁰

Scores ranged from 70 to 90 with a mean of 81.25, which is considered as excellent.

The mean score for primary cases was 83.6, while for recurrent cases was 76. The mean score for cases presenting with pathological fractures was 81.

Table 1 summarizes the characteristics of the cases enrolled in the study.

Table 1.

Summary of the characteristics of the patients in the study.

Case	Age (years)	Sex	Primary	Recurrent	Pathological fracture	Follow-up period (months)	Complications	Musculoskeletal Tumor Society score
1	14	F	+	−	−	66	—	80
2	32	M	+	−	−	24	—	75
3	19	M	+	−	+	60	—	75
4	12	F	+	−	−	78	Recurrence	90
5	7	M	+	−	−	26	—	90
6	11	F	+	−	−	48	—	85
7	7	M	+	−	+	38	—	90
8	29	F	+	−	−	32	Surgical site infection	70
9	12	M	+	−	+	40	—	85
10	9	M	+	−	−	68	—	90
11	14	M	+	−	−	46	—	90
12	26	M	−	+	−	70	—	70
13	14	F	−	+	−	44	—	80
14	12	M	−	+	−	47	—	80
15	10	M	−	+	+	64	—	75
16	11	F	−	+	−	58	—	75

Discussion

Surgical approach

The proper selection of the surgical approach is a cornerstone for proper exposure of any neoplastic lesion. This is particularly important for lesions in the proximal femur due to its peculiar complex anatomy.^21
–23

Wai et al.²¹ reported 11 pathological fractures of the proximal femur secondary to benign bone tumors. In all the cases, extended curettage utilizing Watson Jones approach was done. No recurrences or complications occurred, and all fractures healed soundly. In another study, Strong et al.²⁰ performed intracapsular curettage plus bone grafting in 10 patients with chondroblastoma. In five patients, an anterolateral approach was used with no recurrences, and in the other five, a lateral approach was used with a recurrence rate of 40%. Watson Jones approach has shown to provide an accessible surgical field enough to permit complete exposure of the femoral head and neck without the need for surgical dislocation and enough to perform adequate curettage of neoplastic tissue. Thus, utilization of this approach may reduce the recurrence rate.

Biological reconstruction

Many authors prefer the use of vascularized fibular graft for cavity reconstruction owing to its stable biomechanical properties as its healing does not entail resorption and creeping substitution as compared to nonvascularized graft. However, a major drawback is that it is a lengthy procedure and requires advanced microsurgical skills. On the other hand, the nonvascularized fibular strut graft provides equivalent biomechanical properties once it has healed into its bed. Commonly it regains its full strength within 6–12 months.¹⁶ In this series, graft incorporation occurred with 10–12 weeks. After that patients were allowed graduated weight bearing which proceeded to full weight bearing within 6 months. None of the patients developed implant failure or nonunion of the graft.

Recurrence rates

The biological behavior of ABC tends to be active to aggressive. Lesions that occur in the proximal femur are potentially more challenging as they carry a high risk of pathological fractures due to high biomechanical stress. They also have a high rate of recurrence.²

Simple curettage of ABC, with or without bone grafting, has been associated with relatively high recurrence rates ranging from 20% to 30%.^24
–26 Younger patients, especially before skeletal maturity, have higher recurrence rates after curettage and bone grafting than older patients;^27
–29 therefore, local adjuvants in conjunction with curettage have been advocated in younger patients.^29,30 Recurrence most often happens within 24 months after the original treatment.

The proximity of a lesion to the growth plate makes the surgeon more cautious, the curettage of the cyst more difficult, and as a result increases the risk of recurrence.²⁷

Cryotherapy in one study as an adjuvant after curettage has a recurrence rate of 12.8%.³¹ While in another review of cases, Schreuder et al.³² found that cryotherapy as an adjuvant to curettage of ABCs is associated with a local recurrence rate of 4%. The only recurrence was probably due to technique as only one cycle of cryotherapy had been used.

In our institution, cryotherapy has been adopted as standard technique for management of aggressive benign bone lesions since 2002. In this study, we had only one case of recurrence (11 months postoperative); we assume recurrence was due to overcautious curettage and due to the proximity of the lesion to the epiphysis. Revision surgery was done using the same technique with no recurrence in the follow-up.

Nononcological complications

Cryosurgery seems to be accompanied with an infection rate that differs between institutions, ranging 2% up to 25% with a mean of 4%.^33
–35 Other related complications include fractures, skin necrosis, neuropraxia, and gas embolism.³⁶ These complications are best avoided through proper soft tissue manipulation, filling gaps with gel foams, protecting important structures, and irrigating them with warm saline. Proper immobilization and prudent postoperative rehabilitation should be followed to avoid fractures resulting from osteocyte necrosis, extensive curettage, and already weakened bone.³⁶

In our series, one case got surgical site infection that was treated by debridement and antibiotic according to culture and antibiotic sensitivity, representing a rate of 6%.

Management of pathological fractures

Pathological fractures complicating ABC involving the proximal femoral area entail the combined difficulties of complete resection of the tumor tissue, reconstruction of the defect, and fixation of a fracture that has poor bone stock. The challenge that these patients being young and requiring preservation of the femoral head is also a concern.³¹

Khalifa et al.³¹ managed eight cases with pathological fractures of ABC proximal femur using extended curettage, bone grafting, and internal fixation. All fractures united (average time to union 14 weeks). No recurrence of the tumor was seen at the latest follow-up (average 18 months), with two patients having a follow-up less than 12 months. Failure of fixation occurred in one patient after fracture collapse and migration of the dynamic hip screw, but the fracture united, and the overall functional result was satisfactory. Overall results were excellent in six patients and good in two patients (using the modified HSS score).

This is comparable to functional scores of cases in our study presenting with pathological fractures, despite our different protocol in which initial immobilization for a period of 4–6 weeks was done. This allowed acquiring a contained cavity for extended curettage and cryotherapy to be done safely and efficiently.

Conclusion

ABC of the proximal femur represents a challenge to orthopedic oncologists due to anatomical, pathological, and biomechanical factors. Extended curettage and cryotherapy and reconstruction with nonvascularized fibula represent a recommended approach with good to excellent functional results.

Footnotes

Authors’ note

The authors state that the manuscript has been read and approved by all the authors and that the requirements for authorship as stated earlier in this document have been met and that each author believes that the manuscript represents honest work.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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