Bilateral symmetrical periprosthetic (mirror) fractures of knee fixed with dual plating technique

Abstract

Introduction

Periprosthetic fracture following total knee arthroplasty is a potentially serious condition. Here we report a case of bilaterally symmetrical (mirror) fracture of supracondylar area following trivial trauma.

Presentation of case

Both fractures were OTA 33A2 and according to Rorabeck classification they were type II. Both fractures were fixed by dual plating technique using non locking plates. Intra operative fracture site biopsy revealed marked osteopenia and hence the patient was treated for osteoporosis.

Discussion

Both fractures united well at 14 weeks. At final follow up of 6 years there were no radiological signs of implant loosening and the patient was able to walk without any aids and had a range of 80° and 60° flexion in the right and left knees respectively.

Conclusion

We conclude that in the pre locking plate's era such difficult case has been successfully managed by dual plating technique.

1. Introduction

Incidence of periprosthetic fracture following total knee arthroplasty is gradually increasing, and management of such fractures can be challenging for orthopaedic surgeons. Management options of such fractures vary from conservative management to revision arthroplasty. The aim of treatment in fractures of the distal femur proximal to total knee arthroplasty is to achieve a painless and stable knee without significant residual malalignment. Choice of treatment depends on condition of the knee prosthesis (loose or well fixed), the fracture pattern, quality of bone stock, presence of any other implant in the proximal femur and general physical condition of the patient. A review of 415 cases, reported a nonunion rate of 9%, fixation failure in 4%, an infection rate of 3% and revision surgery rate of 13%.¹ Open reduction and internal fixation allows anatomical reconstruction and early rehabilitation of the patient.

Here we document a case of bilaterally symmetrical periprosthetic fracture of distal femur following trivial trauma managed successfully by dual plating technique, which to our knowledge was not much used for the management of such fractures even in the pre locking plate's era. A case of bilaterally symmetrical (mirror) fracture around total knee arthroplasty to our knowledge is not documented so far in the literature.

2. Case report

A 55 year old male complained of bilateral knee pain following a trivial trauma. He was operated for osteoarthritis knee 1 year before with total knee arthroplasty on both knees. On clinical examination both knees were tender in the suprapatellar area and gentle examination revealed abnormal mobility and crepitus. X-rays confirmed the diagnosis of bilateral periprosthetic fractures. Surprisingly both looked almost similar (OTA 33A2) and according to Rorabeck classification they were type II (Figs. 1 and 2). Open reduction and internal fixation was planned as the implant appeared to be well seated without any loosening. To avoid excessive damage to the surrounding soft tissues and to make sure the local biology is preserved to a maximum extent the fracture was approached through the previous midline incision, medial para petellar arthrotomy and fixed with both medial and lateral plates. A second medial plate was used in both knees to prevent late varus collapse. Surrounding soft tissues were handled carefully and no bone graft was used. Intra operative scrapings from the fracture site were sent for histopathological examination (HPE), as the fractures followed a trivial trauma which revealed significant osteopenia The post operative protocol included non weight bearing and knee bending on the side of the bed was allowed from day 2 onwards. Post operatively once the patient was pain free DEXA scan was done to evaluate bone mineral density which revealed osteoporosis with a T-score of −2.6. Weight bearing was allowed only after 14 weeks when the signs of union appeared on X-rays. Keeping in view that the fracture occurred following trivial trauma the HPE revealing osteopenia and a post surgery BMD of −2.6, the patient was treated for osteoporosis. The treatment of osteoporosis included calcium supplementation from post operative day 1 onwards. However the patient was put on once monthly oral bisphosphonate ibandronate 150 mg only after 8 weeks since they might interfere with the process of union. The patient was also put on strontium ranelate 2 g sachet once daily. Both medications were taken by the patient for 12 months. Bone mineral density done at 12 months follow up revealed osteopenia with a T-score of −1.9 for spine and hip sites.

Fig. 1.

X-ray of the right knee showing displaced supracondylar periprosthetic fracture.

Fig. 2.

X-ray of the left knee showing displaced supracondylar periprosthetic fracture quiet similar to that of the right knee as in Fig. 1.

At final follow up of 6 years both fractures have united well, there were no radiological signs of implant loosening (Figs. 3 and 4) and the patient was able to walk without any aids and had a range of 80° and 60° flexion in the right and left knees respectively.

Fig. 3.

AP views of both knees at 6 year follow up showing well united fractures with implants in situ.

Fig. 4.

Lateral views of both knees at 6 year follow up showing well united fractures with implants in situ.

3. Discussion

Incidence of distal femoral metaphyseal periprosthetic fractures associated with total knee replacement has been reported to range between 0.3% and 2.5%.^2,3 Majority of these fractures occur following minor trauma after a simple fall. Other causes include road-traffic accidents, seizures and forced manipulation of a stiff knee. There are many risk factors which can predispose to these fractures. These include osteoporosis, anterior femoral notching, rheumatoid arthritis, steroid therapy, neurological diseases, previous revision arthroplasty and local osteolysis and infection.⁴

Treatment options varying from conservative management to revision total knee arthroplasty have been well documented in the literature.⁴ Open reduction and internal fixation allows anatomical reconstruction and early rehabilitation of the patient. However, achieving rigid internal fixation could be technically demanding in osteopenic and comminuted bones. Before the advent of locking plates, these fractures were managed with conventional plating techniques. Healy et al. treated 20 fractures with open reduction and internal fixation using a variety of different implants including blade plate, condylar screw and condylar buttress plates. They performed bone grafting in 15 patients and achieved union in 18 patients. Two patients, who did not have bone graft at the time of index surgery, needed reoperation with bone grafting to achieve union.⁵ Moran et al. treated 15 patients with condylar screw and plates, blade plates and buttress plates. Of these 15 patients, 2 developed malunion and 3 nonunion at the fracture site requiring further surgery.⁶ Though a few studies have shown that supracondylar nails are superior to plating techniques, it is not possible to use a supracondylar nail in a very distal fracture, as it may not provide any fixation to the distal screws.

Our case was also operated during that era when the locking plates were not available in our country. However, sticking to the basic principles we achieved union on both sides. There was mild residual varus deformity post operatively, but the dual plating has prevented from further varus collapse and nonunion. However, this residual varus had no effects on the implant survival at a follow up of 6 years. The strength of our report is documentation of successful management of a rare pattern of bilaterally symmetrical peri prosthetic fracture in an osteoporotic patient with a long follow up of 6 years. Treatment of supracondylar periprosthetic fractures of femur remains a significant challenge to the treating surgeons. Here we report a case of bilaterally symmetrical supracondylar periprosthetic fractures, successfully treated with double plating technique. With this experience we conclude that in the pre locking plate's era such difficult case has been successfully managed by sticking to the basic principles of osteosynthesis.

Author's contributions

AVGR, CT, PK and VKR were the team of surgeons who operated upon the patient. AKM and DR were involved in the follow up care of the patient. AVGR, AKM, VKR and DR were actively involved in preparation of the manuscript.

Conflict of interest

None.

Funding

None.

Ethical approval

Written informed consent was obtained from the patient for publication of this case report and accompanying images.