Knee Arthrodesis in Severe Injured Knee Joints

In this report we present our experiences with knee arthrodesis nails as a secondary salvage procedure after severe knee injuries at a level-one trauma centre. Exemplary two cases of subtotal amputation are discussed. Both cases, of totally destroyed knee joints, were treated with a unilateral external fixator, shortening and secondary bifocal distraction osteogenesis. In one case nailing after lengthening (NAL) was performed and in the second case nailing had to be performed as fracture treatment 20 years after bony consolidation at the docking site. Figure 1: Case 1 Extensive soft tissue defect on the lower limb with a totally destroyed knee joint after a motorcycle accident. Figure 2: Case 1 – Radiograph of the total destroyed knee joint.


Introduction
In literature, Knee arthrodesis (KA) are described as a salvage procedure for various indications. They are reported after failed total knee arthroplasty (TKA), severe post-traumatic osteoarthritis in young patients, reconstruction after tumor resection, chronic sepsis and totally destroyed knee joints after severe trauma [1][2][3]. Using this technique the intramedullary nail prevents bending, refracture [4][5][6][7], subsidence [8], bowing of the regenerate bone and secondary shortening. Furthermore the time in an external frame is shortened and improves patient´s comfort and life quality during the healing phase [9].
The aim of this report is to present our experience with posttraumatic knee arthrodesis after lengthening procedures and discuss complications by presenting two exemplary cases.

Material and Methods
Both cases suffered from severe motorcycle accidents leading to severe bone loss and soft tissue damage around the knee joint. Initially, both patients were treated at our emergency department with damage control surgery. They underwent a limb salvage procedure using an external frame. In both cases leg shorting was performed to close the soft tissue defect (Figures 1-5). After this initial treatment both patients underwent bifocal callus distraction and segmental bone transport to regain lengthening. The first case, with 12 cm of bone reconstruction, consolidated in the external frame. However 20 years after the initial injury the patient sustained a grade 1 open fracture above the former docking site, which was treated initially with an external frame at an outside hospital. As the fracture did not heal, he was transferred to our hospital. After eradicating the infection by surgical debridement, stabilization with an arthrodesis nail was performed ( Figure 6).
In the second case, of 26 cm bone loss, the technique "nailing after lengthening" (NAL) was successfully used following bone elongation. The patient sustained a periprosthetic fracture at the distal end of the arthrodesis nail in a further motor vehicle accident (MVA) four years after his initial trauma. As the patient was 191 cm tall a custom made arthrodesis nail had to be manufactured, which took six weeks. Nail exchange surgery was successful and in addition bone graft retrieved from the reamer heads were added at the fracture site to improve fracture healing [10]. X-rays at latest follow-up visit showed bony healing in both cases. The patients were very satisfied with their saved limb.

Discussion
These cases demonstrate successful use of knee arthrodesis nails even in severe trauma cases as a limb salvage procedure. However, these Kuchinad et al. [6] reported a series of bone lengthening using ring fixation with secondary nailing as a salvage procedure after failed TKA. He recommended a cement coated rod to avoid pin track infection. Furthermore a ten day period between frame removal and intramedullary nailing has been recommended [15] as a safety margin to prevent infection. However, temporary cast application is not possible after bifocal tibial and femoral bone elongation. In a further study "nailing after lengthening" did not increase the risk of infection [9]. In our cases thorough wound management was applied, including antibiotics, antibiotic cement spacers and antibiotic beads. Arthrodesis nail breakage or periprosthetic fractures [16] are most uncommon [17,18]. However, these complications need meticulous treatment either by implantation of a longer nail [7] or even plating [19], depending on the location of fracture and the treated bone. Hinarejos et al. [18] reported periprosthetic fractures above and below a modular knee arthrodesis nail. In one of our cases periprosthetic fracture occurred and was finally treated with a longer arthrodesis nail.  very rare and unique patients require other treatment strategies than in cases of failed knee replacement. Alternative methods to the knee arthrodesis nail are modular nails [11], plating after lengthening [6], external frame fixation or even amputation [6].
In our cases we saw as major complication docking site problems, which were treated successfully by bone grafting. In case 1 docking site problem appeared after secondary fracture and infection. In case 2 there was a delayed consolidation after the NAL procedure. However, comparative studies between open, closed or endoscopic docking procedures did not show any difference in bony healing [12,13]. Biz et al. [14] presented a case series of non unions and re-fractures at the consolidated docking site, treated by intramedullary nailing, achieving union and complete bone healing [14].  Regarding outcome, long intramedullary nail arthrodesis as a staged arthrodesis is reported to provide a painless functional gait with low complication and reoperation rates after infected TKA [17]. A slight limb shortening is recommended for knee arthrodesis to allow easier foot clearance during walking and to prevent "overlengthening" [3]. This was considered in the pre-surgical planning, during distraction phase, nailing and re-nailing in all of our cases.

Conclusion
Intramedullary knee arthrodesis presents to be an excellent surgical procedure in secondary treatment of large bone defects. It provides good stability, maintains form and axis of the reconstructed limb and allows early weight bearing with a high rate of union. This improves the patient´s comfort and quality of life.