Dahuja, A¹; Khatri, K²; Kaur, R³; Bansal, K⁴; Singh, S⁵

Language: English
References: 35
Page: 298-306
PDF size: 345.17 Kb.

ABSTRACT

Introduction: fixation of unstable intertrochanteric fractures presents a significant challenge, especially in the context of osteoporosis. Intramedullary implants have been established as superior to plate constructs. Our aim is to compare the complications and clinical outcomes of the Proximal Femur Nail (PFN) and Proximal Femur Nail Antirotation-2 (PFNA2) in managing unstable intertrochanteric fractures. Material and methods: a total of 212 patients meeting inclusion and exclusion criteria underwent fixation of trochanteric fractures using either a standard PFN (n = 110) or PFNA2 (n = 102). Their intraoperative and postoperative clinical and radiographic data were evaluated along with the quality of fixation. Data analysis was performed using the student's t-test, χ² test, and Mann-Whitney U test. Results: PFNA2 demonstrated more favorable outcomes compared to PFN in terms of a better intraoperative profile, functional outcomes (PFNA2: PFN = 82:75), and fewer implant-related complications. Significant issues in the PFN group included screw back-out, guidewire breakage, and proximal protrusion of the nail tip. In contrast, locking mechanism failure and lateral screw prominence were significant problems in the PFNA2 group. Conclusion: PFNA2 is the preferred implant for managing osteoporotic unstable intertrochanteric fractures, given the bone's weak inherent tendency to secure the implant.

INTRODUCTION

Reverse oblique intertrochanteric fractures represent 2-23% of all trochanteric fractures^1,2,3,4,5 and are classified by the AO classification as AO31A3. Increasing clinical evidence supports the use of intramedullary devices for these fractures, with large national registry data from Norway recently advocating for intramedullary devices over sliding hip screws.⁵

Complications with peritrochanteric fractures primarily arise from fixation issues rather than from union or delayed union, as the peritrochanteric area consists of cancellous bone.^3,6 The strength of the fracture fragment-implant assembly depends on various factors, including bone quality, fragment geometry, reduction quality, implant design, and implant placement.^3,6 Among these factors, surgeons can directly control the quality of the reduction, the choice of implant, and its placement. The preferred type of fixation device for intertrochanteric fractures remains a subject of debate.⁵

While the Proximal Femoral Nail (PFN) has shown superiority over extramedullary devices for unstable intertrochanteric fractures, complications such as screw cut-out, back out, varus collapse, and rotational instability remain significant postoperative issues, with complication rates up to 31% reported in the literature.⁷ Introduced in 2003, the Proximal Femoral Nail Antirotation (PFNA) utilizes a helical blade instead of the conventionally used two screws, believed to provide stability, compression, and rotational control of the fracture. Theoretically, it compacts the bone during insertion into the femoral neck, thereby offering higher cut-out strength compared to other devices. This characteristic potentially reduces the chance of implant failure, especially in elderly, osteoporotic bones. This study was undertaken to compare these two types of intramedullary devices in managing unstable intertrochanteric fractures.

MATERIALS AND METHODS

Between January 2012 and June 2021, 240 adults with trochanteric fractures were operated on at our tertiary care hospital, and their data were evaluated. Patients over the age of 55 years with acute unilateral trochanteric fractures classified as AO/ASIF 31-A2 and AO 31-A3, who were independent ambulators prior to injury, were included and prospectively studied. Institutional ethical clearance was obtained (GGS/IEC/18/30). Patients with pathological fractures, open fractures, polytrauma, neuromuscular disorders, or severe cardiopulmonary insufficiency were excluded. A total of 212 patients meeting the inclusion and exclusion criteria underwent Closed Reduction and Internal Fixation (CRIF) of trochanteric fractures with either a standard Proximal Femoral Nail (PFN) (n = 110) or Proximal Femoral Nail Antirotation (PFNA2) (n = 102) as shown in demographics (Table 1). All patients provided written informed consent before the surgery.

Surgical exposures for both implants were similar, except for the techniques and instrumentation used in each system. Background and demographic variables, including age, gender, associated comorbidities, and pre-injury ambulatory status, were obtained. Fracture types were assessed and recorded as per the AO/ASIF classification system using orthogonal radiographs of the affected hip. All patients were administered spinal or epidural anesthesia and positioned supine on a fracture table prior to closed reduction of the fracture. Perioperatively, the duration of surgery, amount of blood loss, and the number of images shot on the image intensifier were recorded.

All patients received three doses of prophylactic antibiotics, including the pre-operative dose given within 30 minutes prior to the skin incision. Postoperatively, all patients received thromboprophylaxis with low molecular weight heparin for the duration of the hospital stay or the first 10 postoperative days, whichever was shorter, followed by aspirin for four weeks. All patients were allowed touch-down weight- bearing ambulation using a walking frame starting from the first postoperative day until six weeks, after which progressive weight bearing was allowed depending on the status of fracture union.

Fractures were classified using the AO alphanumeric classification⁸ after obtaining radiographs - an anteroposterior view of the pelvis with both hips and a lateral view of the affected hip. Singh's index⁹ was used to grade the radiographs for the degree of osteoporosis. Preoperative and postoperative hemoglobin levels and units of blood transfused were recorded. The operative time was documented as per the anesthesia record sheet.

The quality of reduction was assessed by comparing the neck-shaft angle of the operated hip to that of the normal hip on the anteroposterior view. A variation of less than 5 degrees from the normal side was considered a "good" reduction. Between 5 and 10 degrees of variation was considered 'acceptable', and more than 10 degrees of variation was considered "poor".¹⁰ The quality of fixation was assessed using the tip-apex distance described by Baumgaertner MR¹¹ and the Cleveland index.¹²

Clinical and radiological assessments of fracture union/complications for all patients were done pre- operatively and post-operatively at six weeks, three months, six months, and one year. Functional evaluation was conducted at 1-year post-op using the Harris Hip Score.

STATISTICAL ANALYSIS

Statistical analysis was performed using SPSS software (IBM Version 20). The statistical difference between continuous variables was assessed using the student's t-test. Categorical variables were compared using the χ² test. Statistical significance was set at a P-value of 0.05 or less. χ² and student T test used to check significance.

RESULTS

Our study consisted total of 212 patients with the demographics as shown in Table 1. There was female preponderance with 37% of osteoporotic patients. Average operative time, fluoroscopy time and blood loss were significantly lower in PFNA2 group as shown in Table 2.

The average operative time in PFNA2 group was 44 min as compared to 54 min in PFN group. Average blood loss was also lower in PFNA2 group (PFN: PFNA2; 121 ml: 91 ml). The fluoroscopy time was significantly lower in PFNA2 group.

There was no difference in the average length of hospital stay and reoperation rate in both the groups.

Implant related complications like screw back out (Figure 1), guide wire breakage (Figures 2 and 3), Z effect (Figure 4), TAD outliers (Figure 5) were more in PFN group whereas lateral screw protrusion, locking mechanism failure and barrel disengagement was more in PFNA2 group as shown in Figures 6, 7, 8 and 9. Neck shaft valgus outliers are more common in PFN group (Figure 10).

There was no difference between the two groups in terms of surgery related complications, except for early postoperative limb length discrepancy, which was significantly higher in PFN group (Table 3).

There was significant hip pain and varus malalignment in PFN group as shown in Table 4 and Figure 11. Walking aid requirement was relatively on higher side in PFN group (PFN: PFNA2; 13:9) at six months as shown in Figure 12. Persistent pain (PFN: PFN2; 23:14), limb length discrepancy (PFN: PFNA2; 11:4) and varus malalignment (PFN: PFNA2; 19:11) was significantly higher in PFN group.

Favorable results of PFNA2 over PFN in terms of better intraoperative profile, functional outcome (PFNA2: PFN = 82:75) and minimum implant related complications are shown in Figure 13.

DISCUSSION

The literature suggests that the Proximal Femoral Nail (PFN) is a reliable method for treating peritrochanteric femur fractures. However, technical complications, such as intraoperative placement issues, cut-out, and the Z-effect in screws of proximal fixation, have been reported.^10,13 The Proximal Femoral Nail Antirotation-2 (PFNA) was designed to simplify the technique and reduce implant-related complications. Replacing column screws with a helical blade increases the contact surface area between the holding device and the cancellous bone of the femoral head, enhancing stability in fracture fixation and significantly higher rotational torques, as demonstrated in biomechanical studies.^{10,14,15,16,17}

Intraoperative data favored the PFNA group compared to the PFN group, with surgical duration, blood loss, and fluoroscopy time being significantly lower, supporting findings from previous studies.^18,19 Kashid MR et al. and Xie et al. found similar functional results between PFNA and PFN, but PFNA significantly reduced surgery time, blood loss, and fluoroscopy time.^9,18,19

We observed nearly double the number of complications in the PFN group compared to the PFNA2 group, with implant-related complications constituting a significant portion, reinforcing findings from previous studies.^20,21,22,23 Gardenbroek et al. found that the risk of secondary late complications and reoperation is much higher with PFN than with the helical blade device.²⁰ Overall, implant-related complications were 34% in the PFN group.^{7,20,21,22,23}

Implant-related complications, such as screw back-out, guidewire breakage, and proximal protrusion, were more pronounced in the PFN group, whereas lateral screw protrusion and medial migration were notable in the PFNA2 group.²⁴ Lateral screw protrusion was observed in four patients in the PFNA2 group and one patient in the PFN group at the final follow-up in our study. Hu et al suggested a morphological mismatch in the Asian population between the proximal fragment of PFNA2 and the greater trochanter, leading to post-operative lateral trochanter pain.²⁴

Nikoloski et al recommended a tip apex distance (TAD) of 20-30mm for PFNA2,²⁵ observing a higher incidence of cut-through when TAD was more than 30 mm or less than 20 mm. In our study, TAD outliers (< 20 or > 30) were 9 and 11 in the PFN and PFNA2 groups, respectively, with a higher implant failure rate, which is consistent with the study by Sharma et al, who had more outliers in the PFNA2 group but fewer implant failures.²⁶ Our results, supporting the study by Sharma et al., indicate that achieving an optimal TAD is crucial, but some outliers are acceptable in the PFNA2 group (as shown in Figure 5), likely due to its inherent stability.

According to the Cleveland index, maintaining an optimal position (centre-centre, inferior-centre) of the screw is crucial for a good outcome.¹² Complications were more frequent when the screw position was suboptimal in the PFN group. When the index was centre-centre in both groups, no complications were observed, and outcomes were better, whereas five out of eight screws that were in a suboptimal position backed out. Only one case in the PFN group with an inferior-centre index showed a complication of screw back-out. Our results are consistent with other studies comparing these implant designs. Mora A et al compared PFNA with PFN and found a lower incidence of cut-out with PFNA.²⁷ Choo SK et al found less postoperative sliding with PFNA compared to PFN, like our study, which found no difference in walking capacity between patients with either implant.²⁸

Maintaining the neck-shaft angle difference between the operated and normal side to less than 5° is necessary for better outcomes.²⁹ In our study, varus malalignment and Limb Length Discrepancy (LLD) were associated with a neck shaft angle difference of 10° and 5° in the PFNA and PFN groups, respectively. Neck shaft angle outliers were more common in the PFN group (Figure 10), likely to achieve better proximal screw purchase and to avoid postoperative varus collapse, whereas outliers in TAD were more common in the PFNA group, possibly due to difficulty in differentiating between the screwdriver tip and screw head while engaged.

Limb lengthening was notably more common in the PFN group compared to the PFNA group postoperatively (19:6) and even at 1-year follow-up (11:4). No study in the literature highlights LLD between the two groups. Limb lengthening in the PFN group, which was managed with a shoe raise, was likely due to the need to accommodate two screws with better purchase in the middle and inferior part of the neck and excessive intraoperative valgus to achieve the same.

FUNCTIONAL AND RADIOLOGICAL OUTCOMES

Harris Hip Score (HHS) scores and union rates were better in the PFNA2 group (82:75) but statistically non-significant, favoring the study by Mallya et al.³⁰ Varus malalignment, persistent pain, and limb length discrepancy were significantly more common in the PFN group. Park et al and Li et al concluded that PFNA2 outperforms PFNA in terms of functional outcome and mobility scores, whereas Loo et al, from their review article of 62 patients, concluded that PFNA is a better implant for stabilizing proximal hip fractures than PFNA2.^31,32,33

A recent study by Baek SH et al demonstrated better clinical outcomes with similar surgical time in both the groups whereas in contrast our study the surgical time was significantly less in PFNA2 group though better clinical outcomes.³⁴ Our study favoured Yadav et al results which highlighted PFNA2 superiority over PFN in terms of shorter duration of surgery and lesser fluoroscopic exposure.³⁵

Limitations: This is a short-term follow-up study. Although the results suggest that PFNA2 is more cost-effective than PFN due to fewer complications, cost-effectiveness was not evaluated. Further studies should be focused on to limit the complications and if so, then how to manage them.

CONCLUSION

Our study strongly favors PFNA2 over the PFN implant in terms of fewer implant-related intraoperative, postoperative, and short-term complications, while functional outcomes are comparable in both groups. PFNA2 is the implant of choice for osteoporotic unstable intertrochanteric fractures, where the bone's inherent ability to hold the implant is weak.

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AFFILIATIONS

¹ Assoc. Prof Dept. of Orthopaedics GGS Faridkot Punjab, India.

² Assist. Prof. Dept. of Orthopaedics AIIMS Bathinda.

³ Assoc. Prof Dept. of Radiodiagnosis GGSMCH Faridkot Punjab, India.

⁴ Prof Dept. of Orthopaedics GGSMCH Faridkot Punjab, India.

⁵ Junior resident department of Orthopaedics GGSMCH.

CORRESPONDENCE

Rashmeet Kaur, MD. E-mail: dr.rashmeet@gmail.com

Received: 01-23-2024. Accepted: 02-21-2024.