Pertrochanteric fracture of an ankylosed hip with protrusio acetabuli treated by PFNA nail: A case report of a rare case

Abstract

Introduction

Hip fractures are the cause of significant morbidity and mortality, aggravated by the existence of an underlying hip pathology. The association of a pertrochanteric fracture with an ankylosed hip and acetabular protrusion is extremely rare. It has not been reported in the literature and the optimal management remains unknown. The surgical treatment indicated for trochanteric fractures allows patients to restore their autonomy quickly while avoiding complications.

Case presentation

We present the case of a 45-year-old patient who was followed for multiple myeloma and treated with chemotherapy. Following a fall on the pelvis, we found a pertrochanteric fracture with an ankylosed hip and acetabular protrusion. The patient was treated with a PFNA nail based on some principles to improve stabilization, with good results.

Clinical discussion

The combination of acetabular protrusion and hip ankylosis alters the biomechanics of this joint by displacing the center of rotation inward and decreasing abductor muscle tension while increasing the lever arm. Several surgical approaches have been reported on case reports with different results. No consensus has been reached for this entity because of its rarity and the absence of a large sample. The result reported for our patient could make cephalomedullary nailing a good option since it allows preservation of the gluteal musculature, early management of the patient and recovery of the pre-morbid state.

Conclusion

The lack of consensus and the changes caused by this hip condition are a challenge for orthopedists. We treated our patient with a PFNA nail based on a few principles necessary to optimize stability with a satisfactory result.

Highlights

• •We present an extremely rare case of a 45-year-old patient with a pertrochanteric fracture in an ankylosed hip with acetabular protrusion.
• •No cases have been reported in the literature and the optimal management remains unknown.
• •However, the lack of consensus and the changes caused by this hip condition are a challenge for orthopedists.

1. Introduction

The incidence of hip fractures increases with age and are the cause of significant morbidity and mortality, accentuated by the existence of ankylosis of the hip that affects the biomechanics of the joint and all adjacent joints [1], [2]. Fractures of the proximal femur in ankylosed hips are a rare and difficult presentation. Indeed, very few works have described this entity, limited to case reports with two femoral neck fractures [3], [4] and six trochanteric fractures [5], [6], [7], [8], [9], [10]. No trochanteric fractures in ankylosed hips with acetabular protrusion have been reported in the literature. Therefore, there is no consensus for management and orthopaedic surgeons are challenged by a weakened musculature and a joint that, despite osteosynthesis and consolidation, remains immobile with significant disability. This case report has been reported in line with the SCARE Criteria [11].

2. Case presentation

A 45 year old man followed in oncology for multiple myeloma under chemotherapy for 2 years, was admitted for a right hip trauma following a banal fall on the pelvis. The patient reported a marked limitation of mobility of the right hip before the trauma. Physical examination found a right lower limb shortened by 1.5 cm with pain on palpation of the right hip. Joint mobility of was limited to 10° of abduction and 15° of flexion. The standard radiograph showed a simple non-displaced pertrochanteric fracture with protrusio acetabuli and an ankylosed hip (Fig. 1). We then retained the diagnosis of a per trochanteric fracture occurring on an ankylosed hip and acetabular protrusion.

Fig. 1.

Anteroposterior radiograph showing a simple pertrochanteric fracture (red arrow) with an ankylosed hip and acetabular protrusion (white arrow).

The patient was operated on 3 days after the trauma. Osteosynthesis was performed with a PFNA cephalomedullary nail (Fig. 2). Partial weight-bearing with a walker was allowed 3 weeks after surgery. Full weight-bearing was only allowed after 6 weeks. The 8-month follow-up showed a healed fracture (Fig. 3) with hip mobility still limited to 12° abduction and 15° flexion. Walking was possible with the help of a single crutch.

Fig. 2.

Post-operative anteroposterior radiograph showing pertrochanteric fracture fixation by PFNA nail.

Fig. 3.

Anteroposterior radiograph after 8 months of surgery showing fracture consolidation.

3. Discussion

Acetabular protrusion changes the biomechanical environment of the hip. The femoral head exerts pressure on the acetabulum, which pushes inward, shifting the center of rotation inward. In some cases, the protrusion only stops when the femoral neck and greater trochanter are blocked by the acetabular rim [11], [12]. This condition limits hip mobility in all directions. Furthermore, ankylosis amplifies all the consequences caused by acetabular protrusion and makes the hemipelvis and the femoral head a single unit forming the proximal component in case of fracture [10]. This results in a higher than usual lever arm. To overcome this problem, Pato et al. [10] performed a proximal locking femoral plate osteosynthesis reinforced with a plate that extends from the iliac wing to the proximal femur. Malhotra et al. [13] performed a total hip arthroplasty and reported satisfactory results with early mobilization and improved quality of life. On the other hand, THA is associated with a high risk of intraoperative complications and requires special technical skills. It should also be kept in mind that acetabular protrusion shifts the center of rotation inward, resulting in limb shortening and reduced gluteal muscle tension by decreasing the femoral offset [14], [15]. In addition, the thinned acetabular wall and poor bone quality cannot provide adequate stability to the prosthetic implant. It is for all these conditions that THA was contraindicated for our patient. Ishimaru et al. [7] had performed gamma nail management with minimal gluteal muscle trauma and early loading.

For our patient, we opted for PFNA nail fixation, taking certain precautions to obtain better stability. First, we chose a thick nail with a diameter of 17 mm proximally (Fig. 4(a)) and 11 mm distally (Fig. 4(b)), which would fill the medullary cavity and provide close contact with the cortices (Fig. 4). Next, we chose a cervical blade (Fig. 4(c)), which recruits the cancellous bone during insertion to provide better anchorage while taking fixation on the calcar (Fig. 4(d)). To prevent rotation of the nail, distal locking was achieved statically by inserting a 4.5-mm screw (Fig. 4(e)) obliquely into an oblong hole (Fig. 4(f)) and keeping the lateral border of the cervical blade outside the femur (Fig. 4(g)). At the end of the procedure, a 5-mm end cap was inserted into the end of the nail (Fig. 4(h)), providing stability in abduction and adduction. The result was satisfactory with resumption of walking with the aid of a single crutch. We judged that prosthetic replacement could not be indicated for this patient because of the atrophy of the gluteal muscles and the advanced state of the acetabular protrusion and ankylosis, which did not give advantages to this technique over the PFNA nail in terms of results. The limitation of this study is the very small size of the patient with similar presentations, limited to case reports, which prevents comparative studies between the different techniques to manage this type of patient.

Fig. 4.

Anteroposterior radiograph (left) showing the principles used to optimize the stability of the implant (a–h), as well as an image (right) showing the components of the PFNA nail.

4. Conclusion

Hip fractures occurring in ankylosis and acetabular protrusion conditions are extremely rare and no cases have yet been reported in the literature. The optimal management remains unknown. However, the result of our patient's case could make the cephalomedullary nail an interesting option by avoiding aggression of the gluteal muscles and allowing the patient to resume weight-bearing early.

Patient consent

Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Ethical approval

The study is exempt from ethical approval in our institution.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Guarantor

Ben Bouzid Yassine, M.D.

CRediT authorship contribution statement

All authors have read and approved the final manuscript.

Declaration of competing interest

The authors declare that there is no conflict of interest.

Availability of data and materials

The datasets used and analysed during the study are available from the corresponding author.