1 Introduction

Benign lesions involving the femoral neck are not uncommon in one's clinical practice and these conditions have a high risk of pathological fracture.^1,2 Most of these lesions occur in young and active individuals.^1–3 While surgery is recommended, there is still a dilemma regarding whether to apply a fixation device or not and the choice of grafts used to augment the defect after curettage.^2–5 Literature has shown that while all authors concur on salvaging the femoral head and providing adequate disease clearance, they vary on the choice of the reconstructive modality of the curetted cavity.^1–6 While good results have been shown employing autografts with or without fixation devices, these procedures are always associated with donor site morbidity.^1,3,5 Use of allografts has traditionally been associated with slow incorporation, low immunogenicity, and increased infection rate but they have been seldom used to manage benign lesions of the proximal femur.^4,6 It is doubtful if allografts will fulfill bone incorporation of these defects after curettage. Providing adequate disease clearance by extended curettage, reconstruction of the defect with appropriate bone grafts combined with stabilization using a fixation device would help in decreasing chances of recurrence, prevent a pathological fracture and also ensure early mobilization of the patient.

We hypothesized that impaction bone grafting (IBG)⁷ – tight packing of contained cavity defect with compressed particulate bone grafts - of gamma-irradiated morselized allografts into the femoral neck after extended curettage coupled with a fixation device through a single lateral approach would benefit the patients with regards to adequate disease clearance and decreased surgical morbidity. Patients would also benefit from the restoration of the defect cavity after curettage. We employed this novel technique in managing benign lesions of the proximal femur at our institution from 2013 and we present our experience in this article.

2 Materials & methods

After obtaining approval from our Institutional review board (IRB), we retrospectively reviewed all the consecutive cases of benign lesions of the proximal femur managed with extended curettage followed by IBG of allografts and stabilization with an implant at our institution. Between 2013 and 2019, 35 consecutive patients – 21 males and 14 females - who had a biopsy proven diagnosis of a benign lesion in the proximal femur were managed using this technique (Table 1). Pain, impending pathological fracture, and a Mirels' score of 8 and above were taken as indications for surgery. Clinical decision regarding pain and discussion in a multidisciplinary meeting to decide to operate in all cases.⁸ The mean age of the study group was 23.8 years (14–41) with a median Mirels’ score of 9 (8–11) at presentation. All patients were evaluated with an anteroposterior and lateral radiograph of the affected hip joint, an MRI, and were also subjected to fluoroscopic guided needle biopsy through a lateral approach to establish a confirmatory diagnosis. The histological diagnosis was fibrous dysplasia (FD) in 17 cases (49%), aneurysmal bone cyst (ABC) in 5 (14%), chondromyxoid fibroma (CMF) in 4 (11%), chondroblastoma in 4 (11%), giant cell tumour (GCT) in 3 (9%) and simple bone cyst (SBC) in 2 (6%). The mean interval time between biopsy and surgery was 7.4 (5–14) days.

2.2

2.2 Surgical technique

All surgeries were done under spinal anaesthesia with the patient positioned in a fracture table. A prophylactic antibiotic of 1.5 g intravenous cefuroxime was given on induction. Under image intensifier guidance, the hip joint and the proximal femur are scanned and a lateral incision including the biopsy scar is taken. Through the lateral approach, dissection is made through the tensor fascia lata. After elevating the vastus lateralis anteriorly, the required portion of the lateral cortex of the proximal was exposed. By drilling the lateral cortex, a cortical window is made to gain access to the lesion. Through the window, the lesion is accessed. The window must be wide enough to allow adequate disease clearance and curetting is done until the underlying normal bone is seen. A high-speed burr (60,000 RPM) is used to burr the underlying bone in appropriate cases where it was required. Hydrogen peroxide is used as an adjuvant in all cases and a thorough wash of the underlying cavity is done. Following that the technique of IBG was used to reconstruct the curetted cavity in the proximal femur.⁷

The allografts were then morselized, packed into a metallic barrel and the graft is delivered into the cavity in the proximal femur (Fig. 1). Once the graft is delivered, a guidewire is passed through the center of the femoral neck. An 8-mm inner reamer is passed over the guide pin in the forward direction, and then reverse reaming is done while removing the reamer. A similar procedure of delivering allograft, reaming, and reverse reaming is done several times (3–4 times in our experience) until the image intensifier shows a uniform distribution of graft all around the cavity. This procedure of serial reaming and associated reverse reaming helps to distribute the allograft uniformly across the cavity. Once the graft has been adequately impacted, a dynamic hip screw with side plate fixation is done. In cases where the physis was still open, we inserted the hip screw just short of it. Curetted samples are sent for histology to re-confirm the initial diagnosis.

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Fig. 1 Lytic lesion of the femoral neck with a Mirel's score of 10 at presentation (a). Extended curettage using high-speed burr (b) followed by impaction bone grafting (c, d) of morselized allografts followed by DHS fixation (e). Radiograph taken at 3-year follow-up showing good consolidation of the cavity (f).

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In our series, tibial slices were predominantly used as allografts followed by femoral head slices in 31 cases (89%) and 4 cases (11%) respectively. In two patients who had a wide diameter of the femoral neck, we employed an additional fibular strut allograft to augment the defect. All patients had a routine physiotherapy protocol which included hip abductor strengthening exercises and non-weight mobilization walking for 4 weeks followed by a progressive increase in weight-bearing as tolerated. Patients were followed up at 3 months, 6 months, and at 1 year followed by yearly follow-ups. Radiographs were taken during each follow-up and functional outcomes were scored using Harris Hip Score (HHS) and Musculoskeletal tumour society (MSTS) score at 1 year and the last follow-up. Radiographs taken at follow-ups were assessed to see for radiolucency of the cavity filled with allografts to see for any recurrence.

Each radiograph taken during follow-up was assessed by an orthopaedic registrar and a radiology fellow to see for any signs of disease recurrence. The attenuation of allografts if any in the impacted cavity was noted for in the radiographs. All the follow-up radiographs were compared with the immediate postoperative radiograph and the scoring was done. If it was seen, then it was scored as ‘Yes’, otherwise it was scored as ‘No’. Any disagreement was settled by mutual discussion. All radiographs taken during follow-up were seen in PACS system and scoring was done.

3 Results

No patient was lost to follow-up. All 35 patients returned to full weight-bearing walking at 12.4 weeks (8–20) post-surgery. Thirty-four patients (97%) returned to unrestricted normal activity at the end of 6 months. Two patients (GCT = 1; fibrous dysplasia = 1) had a recurrence of the disease at 9 months and 12 months post-surgery, respectively. One of the patients with a diagnosis of FD had stable disease and was managed conservatively without progression of disease or aggravation of symptoms. The other patient, who had a tissue diagnosis of GCT, had a progressive increase of disease, which warranted a revision surgery involving a curettage and joint replacement as the femoral head could not be salvaged. At a mean follow-up of 41.5 months (23–80), all the remaining patients (94%), demonstrated favorable functional outcomes with a mean MSTS of 28.3 (18–30) and a mean HHS of 94.3 (66–100) at the last follow-up. All curetted samples during surgery sent for histology corresponded to the initial diagnosis made before surgery.

Radiographs showed consolidation and good incorporation of allografts with the parent bone in the remaining cases (n = 33), across all pathologies at the final follow-up (Fig. 2, Fig. 3 and Fig. 4). No patient sustained any pathological fracture or developed avascular necrosis of the femoral head.

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Fig. 2 Fibrous dysplasia involving proximal femur in a 17-year-old female (a). Post-operative radiograph showing impacted allografts (b) and complete incorporation in the radiograph taken at 30 months post-surgery (c). Patient demonstrated an MSTS score of 95 and HHS of 27 at last follow-up.

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Fig. 3 Lytic lesion of the femoral neck in a 24-year-old female (a) managed with IBG of allografts (b) and DHS fixation (c). Post-operative radiograph at 6 months (d) demonstrated lucency in the region of impacted allografts which resolved and showed incorporation at subsequent follow-up at 12 months (e). The histological samples corresponded with chondromyxoid fibroma.

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Fig. 4 Lytic lesion diagnosed as Chondroblastoma (a). Due to the wide diameter of the neck, an additional fibular allograft strut was combined along with allografts and implant during surgery. Good consolidation of the cavity and incorporation of the allograft with the parent bone seen at 2 years follow-up (b).

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Evaluation of the radiographs revealed a similar pattern of incorporation of allografts. During the 3-month follow-up, 42% (13/31) of the available radiographs showed increased lucency in the cavity of incorporated allografts and at the 6-month follow-up, 87.5% (28/32) of the available radiographs showed increased lucency compared to the initial post-operative radiograph. However, at 12 months follow-up, the radiographs showed the disappearance of lucency and good consolidation of allografts and integration to the parent bone (Fig. 3).

Two patients (6%) developed superficial infection post-surgery which healed with dressings and intravenous antibiotics. Two patients (6%) developed a temporary abductor lurch which resolved following supervised abductor-strengthening exercises. Only one patient complained about implant-related irritation during follow-up at 2 years for which implant removal gave him relief of symptoms (Fig. 5). Two patients had recurrence with one of them warranting revision surgery (Fig. 6).

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Fig. 5 Simple bone cyst in a 19-year-old female who presented with a Mirel's score at 9 during presentation (a, b). Following management with IBG of allografts, she went on to have a favorable outcome showing good incorporation into parent bone (c, d). Two years post-surgery, she had symptoms related to implant irritation (e). Following implant removal, she remained asymptomatic (f) at the latest follow-up.

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Fig. 6 Complications: GCT in a 24-year-old female had a recurrence following surgery (a). Due to an increase in the size of the lesion leading to the destruction of the femoral head (b) and an increase in symptoms, we suspected recurrence. Biopsy confirmed recurrence of GCT. To harden the lesion and aid in dissection, two doses of Denosumab were administered. We did revision surgery involving extended curettage and joint replacement (c). Recurrence of FD in a 19-year-old male seen on radiograph during follow-up (d) was managed conservatively as the patient was asymptomatic. Regular follow-up radiographs did not show any increase in the size of the lesion.

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4 Discussion

Our study shows favorable results while using allografts through impaction bone grafting to manage benign lesions of the femoral neck. To the best of our knowledge, this is the largest reported series of the use of only allografts in the management of such lesions. This is the central strength of our study. Our results show that IBG of allografts following extended curettage of benign proximal femur lesions provides adequate consolidation of the cavity and was successful in 94% of cases without any need for secondary procedures. Adding a fixation device provides better stability and also ensures favorable outcomes. Most importantly we used only a single lateral approach and the use of allografts avoided donor site morbidity associated with autograft use.

Benign lesions in the proximal femur offer extra challenges in management following curettage due to their unique anatomy. Lesions in that region significantly weaken the cortex and due to biomechanics involved in relationship with the hip joint,^11,12 there is a higher chance of fracture if not managed appropriately. Another factor that is important to be considered is that these lesions usually occur in younger individuals. Young individuals who are active need to be managed appropriately to prevent a fracture following treatment. Hence, we used an internal fixation device after extended curettage as it offers better stability and the chances of fracture are minimized. The average age of patients in our study was 23.8 years and offering a fixation device after IBG in young active patients is associated with good functional outcomes as seen in our results. The use of a fixation device also helps in early weight-bearing as seen with our patients. George et al.¹ who used only a non-vascularised fibula autograft strut to manage 17 cases, advocated their patients to unrestricted activity only around 12 months whereas in our series patients started full-weight bearing around 3 months after surgery and within 6 months, all our patients performed unrestricted activity.

The choice of grafts to reconstruct such defects has predominantly been autografts.^1,3–6 Use of fibular autograft strut,^1,4,6 use of iliac crest autografts³ and a combination of autografts and allografts⁵ have been advocated ay authors. However, autograft harvest is associated with occasional complications. Banwart et al.¹³ in their analysis of 261 consecutive patients, who underwent iliac crest harvest, reported 39% of minor complications including dysesthesia lasting more than 3 months. Fibula harvesting for usage is also associated with occasional complications.^1,14 Lenze et al. showed a 5.6% incidence of transient peroneal nerve palsy after harvesting fibula.¹⁴ The use of only allografts can be a solution to avoid donor site morbidity but has been seldom reported. One of the reasons could be the lack of availability of allografts in treating centers. The versatility of usage and plentiful supply are other important advantages associated with allografts.^15,16 The delivery of allografts into the curetted cavity in an adequate fashion can be challenging and hence the technique of IBG of morselized grafts is essential. Morselized grafts are easy to deliver into the cavity and the process of repeated reaming involved in IBG ensures tight packing of the contained cavity with grafts. This helps in the adequate reconstruction of the bone stock which is essential especially in young patients. No patient developed avascular necrosis during the latest follow-up which is also reassuring. Allografts have traditionally been shown to be associated with an increased infection rate, disease transmission, and reduced rate of incorporation.^1,17 But with newer guidelines issued and stringent processes followed with regard to bone processing and irradiation,¹⁸ there has been a decrease in the incidence of adverse reactions. Gamma irradiation is one of the safest modes of sterilization of allografts to prevent disease transmission and is safe for clinical use.¹⁹ We employed such grafts in our series and no patient reported any allograft-related adverse complications and all patients had complete incorporation of the graft. Even in two patients in our series who had a wide femoral neck, we supplemented the cavity with a fibular allograft strut before inserting the implant. Both these patients went on to have complete incorporation of the strut and also associated good functional outcomes. Allografts mainly produce an osteoconductive matrix which when surrounded by fibrovascular granulation tissue undergoes vascular and osteogenic cell invasion leading to incorporation with parent bone.^19,20 The rich vascular supply of the proximal femur is another important factor that helps in vascularisation and subsequent incorporation of allografts. However, it must be kept in mind that appropriate clearance of the disease by extended curettage is the most important factor of disease recurrence and this must be carefully and thoroughly done in each case. The two cases of recurrence in our series can mainly be attributed to the biology of the disease and probable disease clearance during the initial surgery.

The pattern of integration of allografts into parent bone as visualized in radiographs is different compared to other forms of bone grafts and substitutes. Allografts undergo creeping substitution which involves graft resorption followed by osseous incorporation. Radiographs taken during this time could show some lucency^20,21 and this should not confuse treating clinicians to mistake this for recurrence. In our series, 41.9% of available radiographs during the 3-month follow-up period and 87.5% at 6-month follow-up, demonstrated increased radiolucency compared to the immediate postoperative radiograph. However, these patients were clinically asymptomatic and were kept on routine close follow-up. Subsequently, the radiographs of these patients showed good incorporation of allografts to parent bone and patients also demonstrated good functional outcomes. CT scans have been shown to analyze graft incorporation better,^20,22 but however, the risks of associated radiation with it²³ should be taken into consideration. Also in our technique of management, the presence of an implant would result in image scatter on scanning and would hinder the radiologist from making an accurate analysis. We strongly feel that radiographs are sufficient to monitor these cases with the background knowledge regarding the pattern of incorporation of allografts.

5 Conclusion

Management of benign lesions of the femoral neck offers extra challenges as they predominantly occur in young individuals and also due to associated biomechanics of the proximal femur. IBG of allografts after extended curettage combined with an implant offers good bony consolidation of the cavity, ensures better stability, and is associated with favorable outcomes. The transient lucency of allografts seen on post-operative radiographs must not alarm clinicians with regards to recurrence and these patients must be followed-up regularly.

Funding statement

This study was funded by Ganga Orthopaedic Research & Education Foundation (GOREF).

No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.

Informed consent

All participants were informed regarding the use of their Images, and consent was obtained for their use in anonymity.

The study was performed in accordance with the ethical standards in the 1964 Declaration of Helsinki.

Ethics approval

Institutional Review Board approval was obtained for this study and the same has been attached in the Supplementary documents.

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Author contributions

RBR: Conception of the study, project administration, interpretation of data, writing of manuscript. DJ: Designed the study, Supervision, Review, and Editing of Draft. DRP: Designed the study, Review, and Editing of Draft. DA: Designed the study, suggested corrections in manuscript. PBT: Assisted in methodology and analysis of data, final approval of manuscript for submission. SR: Review and Editing of manuscript, final approval of manuscript for submission. All authors have read and approved the Manuscript.