Does injectable platelet-rich fibrin enhance healing in intracapsular femoral neck fractures: A preliminary study

INTRODUCTION

Intracapsular femoral neck fractures in physiologically young individuals require osteosynthesis with multiple cannulated cancellous screws (CCS) fixation. It is estimated that almost one-third of these cases do not unite after operative stabilization.¹ This may result in locomotor disability necessitating revision surgery (for example; muscle pedicle bone grafting, valgus osteotomy, and total hip arthroplasty).² Such a high incidence of non-union in these young individuals poses a therapeutic challenge for orthopedic surgeons. Studies on the possible use of biologics in reducing non-union incidence are sparse.

Various researchers have explored biological modalities to enhance fracture healing. Platelet-rich plasma (PRP) has been used extensively in orthopedics,³ including in intracapsular femoral neck fracture.⁴ Platelet-rich fibrin (PRF) is a newer biological modality among platelet concentrates. It contains a dense fibrin-network, platelets, leukocytes, cytokines, structural glycoproteins, and growth factors like TGF-beta, platelet-derived growth factor, and vascular endothelial growth factor.⁵ PRF mixed with bone grafts has been reported in dental surgery to fill alveolar defects.⁶ However, its possible benefit has been explored sparsely in orthopedics.^7,8 Dallari et al. (2016) reported using PRF in an aseptic non-union of the tibia with encouraging results.⁹ In sharp contrast to PRP, the preparation of PRF doesn’t need specialized anticoagulant vials, which makes it easier to prepare even in peripheral areas of developing nations. Its results are superior to PRP in managing dental alveolar defects.¹⁰ The recently introduced ‘injectable’ PRF (iPRF) has been shown to achieve higher platelet count¹¹ and regenerative potential among other platelet concentrates and has shown influence on the migration/ proliferation/ differentiation of human-osteoblasts in an in vitro study.¹²

We prospectively studied the radiological and clinical outcomes of iPRF in the treatment of femoral neck fractures that underwent closed reduction and internal fixation with multiple cannulated lag screws.

MATERIAL AND METHODS

This prospective comparative study was carried out on consecutive patients presenting with femoral neck fractures between September 2018 and May 2019 in a tertiary care, teaching referral institute attached to a medical college. Clearance from the Institutional Ethics Committee was granted. CTRI registration was done before enrolling patients.

The patients presenting with femoral neck fractures were enrolled, considering the following inclusion criteria: (1) duration since injury <3 weeks; (2) age group between 18 to 55 years; and (3) unilateral, isolated, non-comminuted femoral neck fracture. The patients with pathological fractures, metabolic bone disease, immunocompromised state, and systemic infections were excluded from the study. We also excluded the patients with platelet count <130 × 10⁹/L, or those on any drug that can alter the platelet quantity/ quality. These cases were classified according to Anatomical, Garden, and Pauwels classifications. They were randomized into two groups based on odd-even number fashion: the odd-numbered patients were kept in group A and received iPRF during operative fixation; even-numbered patients were categorized in group B and underwent operative fracture-fixation without iPRF. A total of 22 patients (11 belonging to each group) were evaluated [Figure 1]. The sample size was calculated based on an article by Samy et al.⁴ (2016).

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Figure 1:

Consolidated standards of reporting trials flow diagram of the study.

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All the patients underwent closed reduction and internal fixation using three CCSs by lateral approach in the supine position on the radiolucent fracture table. Garden’s alignment index was used to assess the quality of reduction as per standard operating procedure¹³ in groups A and B. In group A, the CCSs were initially advanced only till the fracture site. The iPRF was prepared in the operation theatre, for which 20 mL of the patient’s venous blood was withdrawn, taking all aseptic precautions. The blood was transferred into two sterile plain vials (Generic,15 ml centrifuge tube) and centrifuged at 3300 rpm for 2 minutes in a Generic centrifuge machine.¹⁴ It resulted in the separation of blood into two layers: the upper iPRF layer and a lower red blood cells (RBC) clot layer [Figure 2a]. The iPRF was aspirated (usually 5 to 6 mL) using a 16 to 18- gauge cannula needle and syringe [Figure 2b], avoiding aspiration of the lower RBC clot layer [Figure 2c]. This iPRF was injected within 5 to 10 minutes of preparation at the fracture site after putting screws to the fracture site and removing the respective guide-wire sequentially, using an infant feeding tube passed through each of the CCS [Figure 3a-e]. Following this, each screw was sequentially advanced, and precaution was taken not to compress the fracture site till iPRF had been injected through all three screws. Internal rotation of the operative limb and tilting the operative table towards the opposite side were done to prevent the backflow of iPRF. All these patients were kept non-weight-bearing for 12 weeks. The sutures were removed after 2 weeks. The patients were followed at 1.5, 3, 4.5, 6, 9, 12, 18, and 24 months after the surgery for clinical and radiological assessment. Radiological healing was assessed by consensus between an orthopedic surgeon and radiologist blinded on group allocation. The decision was based on anteroposterior and lateral radiographic views to see the fracture line, continuity of medial/ lateral/ superior/ inferior cortices of the femoral neck, varus collapse, and screw backout. The fracture was considered united on radiographs when cortical continuity was established, and the fracture line was not visible. However, it’s a challenge to determine the healing of these fractures on radiographs alone. Non-contrast computed tomography was used whenever there was doubt about fracture healing on radiographs.

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Figure 2:

Preparation of iPRF (a) Centrifuge vial showing an upper layer of iPRF separated from lower clotted RBC layer, (b) iPRF being aspirated using a wide bore needle and syringe; (c) iPRF is ready for application at the fracture site. iPRF: Injectable platelet rich fibrin, RBC:

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Figure 3:

(a) Instillation of iPRF at the fracture site using an infant feeding tube passed through CCS, (b) CCS advanced till fracture site and guide wire removed to instill iPRF, (c) CCS was advanced after instilling iPRF, (d) final antero-posterior and, (e) lateral views showing all 3 CCS in satisfactory position. iPRF: Injectable platelet rich fibrin, CCS: Cannulated cancellous screws.

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The patients were clinically assessed using the Visual analogue scale (VAS) for pain, Harris hip score (HHS) for function, and surgical site examination for clinical signs of infection.

The analysis was done using SPSS version 25 for Windows. Qualitative data were analyzed using the Chi-Square test and Fisher Exact test, and quantitative data were analyzed using Student’s t-test and Mann-Whitney U test. A p-value<0.05 was considered statistically significant.

RESULTS

The differences in age, gender, and duration since injury between the groups were not statistically significant (p>0.05). The patients were operated on at a mean of 2.63 days (range; 1 day to 5 days) in group A and 3.09 days (range; 2 days to 6 days) in group B (p=0.44). The difference in the fracture morphology between the two groups was not significant statistically for the Anatomical type (p=1), Garden type (p=0.38), and Pauwels type (p=0.2). However, group A had a mean Pauwels angle of 55.45 ± 9.23 degrees (range; 41 degrees to 66 degrees) as opposed to 45.72 ± 10.98 degrees (range; 25 degrees to 60 degrees) for group B and this difference was significant (p<0.05) [Table 1]. The mean blood platelet count was 330 ± 69 × 10⁹/L. (range; 280 × 10⁹/L. to 420 × 10⁹/L.). Group A had early radiological healing with a mean duration of 4.63 ± 0.77 months (range; 3-6 months), which was less than the mean value of 5.59 ± 0.66 months (range; 4.5-6 months) in group B (p<0.05) [Table 2], despite having a significantly higher mean Pauwels angle than group B. At 4.5 months follow-up, 9 out of 11 patients had radiological healing in group A compared to 3 out of the 11 in group B (p<0.05). Eventually, two patients in group B and none in group A had non-union [Figure 4a-c]. These patients had an undisplaced, transcervical, and Pauwels type 2 femoral neck fracture. These patients were treated by valgus osteotomy and angled blade plate fixation. One of these patients developed femoral head osteonecrosis and underwent uncemented total hip replacement later. None of the patients showed any evidence of implant failure till the last follow-up.

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Figure 4:

(a) Antero-posterior view radiograph of a 25-years-old male patient who sustained intracapsular fracture neck of femur right side and was assigned to Group A, (b) radiograph obtained at 2 weeks after surgery (CRIF with 3 CCS and iPRF); and (c) follow-up radiographs at 12 months after surgery showing fracture union without any evidence of osteonecrosis of femoral head and the patient is still under follow-up. CRIF: Closed reduction & internal fixation, iPRF: Injectable platelet rich fibrin, CCS: Cannulated cancellous screws.

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Clinically, the difference between mean VAS was not statistically different between the two groups at 12 months follow-up (p=0.47), though the patients of group A perceived less pain (mean VAS = 2.73 ± 1.01) in comparison to group B at 3 months follow up (mean VAS =4.18 ± 1.08) (p=0.01) [Table 3]. The mean HHS was 94.09 ± 3.59 (range; 88 to 98) and 84.36 ± 17.58 (range; 35 to 95) for groups A and B, respectively, at 24 months follow-up (p=0.006) [Table 3]. None of the patients in either group had surgical site infections.

DISCUSSION

Intracapsular femoral neck fractures are treated by osteosynthesis using multiple CCSs in physiologically young individuals. Non-union in these cases remains high despite improved surgical fixation techniques, which range between 10 to 30%.¹ Various authors have emphasized the improvement in fracture biomechanics to enhance fracture healing, which includes fracture fixation configuration,¹⁵ positive medial cortex buttress support,¹⁶ and valgus osteotomy.¹⁷ The biomechanical advantage of valgus osteotomy in patients having high Pauwels angle is well described but poses challenges in conversion into future arthroplasty if required.

With the advent of molecular biology and understanding of fracture environment, newer treatment modalities have been proposed to enhance fracture healing. Biologics/ biological response modifiers such as bone marrow aspirate,¹⁴ and platelet-rich concentrates like PRP^4,18 and PRF⁶ are being extensively studied for the healing of soft tissue and bones. Platelets secrete growth factors that initiate healing by enhancing tissue healing, fibroblast-mitogenesis, angio-genesis, macrophage-activation, and cell-proliferation.

Experimental studies in rat models have shown promising PRF results in treating long-bone femoral fractures.⁷ Six of 9 animal studies have reported the advantages of PRF on orthopedics [Table 4].^7,8,19-25 Recently, BMA and PRP have been used to treat the aseptic non-union of long bones and femoral neck fractures.

The use of PRP with internal fixation in femoral neck fractures has been reported to enhance union rates (93.3% in the test group as compared to 83.3% in the other group).⁴ All the clinical studies on the use of PRF in orthopedics have been summarized in Table 5.^9,26-34

Recently introduced iPRF forms a three-dimensional fibrin network with a greater quantity of entrapped platelets, leukocytes, and growth factors than PRP and PRF. It has also shown greater enhancement in tissue healing. However, its potential clinical role in fractures, especially the femoral neck, which poses problems in healing is yet to be established.

In the present study, we evaluated iPRF in femoral neck fracture healing following surgical fixation. There were a few limitations of the study. Firstly, our study had a small cohort, and patients were distributed heterogeneously as tertiary-level referral institutes tend to receive patients with severe and complex fracture patterns. Secondly, we did not evaluate iPRF for its platelet count and injected it directly. This was done because we did not have the facility of counting platelets in the operation theatre, and transport of iPRF to the hematology lab would have resulted in the solidification of its injectable liquid form into a gel within 5-10 minutes. The mean blood platelet count was 330 ± 69 × 10⁹/L in our study.

However, this is the first study to evaluate the use of iPRF in femoral neck fracture patients. In our study, we used an infant feeding tube to deliver iPRF to the fracture site, which probably served as advantageous in addition to the technique used by Samy et al. (2016). Also, The PRF tends to solidify into a gel-like substance, preventing its backflow from the fracture site as compared to PRP.⁴ Approximately one-third of these fractures may not unite.¹ The mean duration of the bony union in our study was 5.03 ± 0.8 months. The union time was lower in the iPRF group [Table 2]. The healing time in the control group was comparable to data in available literature for standard treatment. Zhou et al.³⁵ (2007) observed an average of 6.5 months of union time in their study on femoral neck fractures treated by CCS. Lin et al.³⁶ (2010) reported an average union time of 7.1 ± 1.2 months in their study as they used percutaneous autogenous bone marrow grafting in femoral neck fractures. Dewei et al.³⁷ (2014) reported union in displaced neck femur fractures with a vascularized bone graft at 18.5 weeks. Yu et al.³⁸ (2013) observed a healing time of 4.4 months and 6 months in the case and control group of neck of femur fractures treated with vascularized bone grafting. Lin et al.³⁶ (2010) conducted a study on autologous bone marrow grafting in femoral neck fractures, which had 1 type 1, 6 type 2, 12 type 3, and 11 type 4 fractures based on Garden’s classification. Zhou et al.³⁵ (2007) classified their patients into 15 type 1, 16 type 2, and 11 type 4 neck of femur fractures where the bone marrow was instilled along with internal fixation by CCS. In our study, the PRF group had a significantly higher Pauwels angle, suggesting an unstable fracture morphology and disadvantage in healing compared to the control group [Table 1]. A higher Pauwels angle is associated with lower healing potential due to increased shear as compared to compressive forces at the fracture site. All these patients were operated on after 24 hours of injury with a mean interval of 2.57 ± 1.04 days (range; 2 days - 6 days). Samy et al.⁴ (2016) performed surgery within 24 hours on their patients with femoral neck fractures treated by CCS and PRP.

Platelet-rich concentrates have shown efficacy for pain relief in various studies. Singh et al.³⁹ (2019) observed a decrease in VAS score on injecting PRP in hip osteoarthritis. VAS score guides as a prognostic factor in hip fracture patients during rehabilitation.⁴⁰ Group A patients had less pain and better function than the other group, but the difference was not statistically significant (except for VAS score at 3 months) [Table 3].

CONCLUSION

iPRF may help femoral neck fractures heal in physiologically young individuals. The present pilot study may prove to be a steppingstone for a multi-institutional randomized controlled trial with a larger sample size, which may establish its role in routine clinical practice.