To our knowledge, there exists no system that is universally accepted and acts as gold standard in the exact definition and description of hip joint infections. Apparently, all classification systems contribute to the treatment and prevention of these infections by requiring the physician to acknowledge and record factors affecting the multiple domains of wound healing; however, they all have pros and contras. Perhaps, it would be advisable to conduct a large multi-center study in order to record and identify all influencing parameters and different treatment strategies and, hence, establish guidelines for the management of hip joint infections. Until such a study is carried out, orthopaedic surgeons should be aware of the various infection staging systems, classify patients with hip joint infections as detailed as possible (to our opinion, most cases can be sufficiently documented according to the McPherson classification), and try to identify new possibly influencing parameters that have not been described, yet.
In contrast, when the reason for the revision hip replacement is infection or instability, the implanted components are usually very well attached to the supporting bone and the removal of the prosthesis can be quite laborious and time consuming. Great care is taken so that while removing the prosthetic implant, as little supporting bone is removed as is possible. The bone of the more senior patient is often quite osteoporotic and the process of removing the implant can result in fractures of the supporting bone, thereby greatly complicating the situation and leading to the need for a more complex implant than was originally intended. One trick that the experienced surgeon uses to extract the femoral component is to split the bone in a controlled fashion to allow access to the well-fixed stem. With the use of sophisticated burrs and other surgical instruments, the stem can be freed and the femur put back together to hold the new prosthesis.
12. Hsieh PH, Shih CH, Chang YH, Lee MD, Shih HN, Yang WE. Two-stage revision hip arthroplasty for infection: comparison between the interim use of antibiotic-loaded cement beads and a spacer prosthesis. 2004;86:1989-1997
5. Cabrita HB, Croci AT, Camargo OP, Lima AL. Prospective study of the treatment of infected hip arthroplasties with or without the use of an antibiotic-loaded cement spacer. 2007;62:99-108
A 68-year-old man presented with sepsis and a two-month history of general malaise and 18kg weight loss. His past medical history includes elective right and left hip replacements, 22 and 14 years ago, respectively. The left hip replacement was complicated with two dislocations, which were both managed with closed reduction and no complications were reported in the right hip. This is on a background of haemachromatosis with no evidence of end organ damage, thoracic shingles with no residual post-herpetic neuralgia, well-controlled gout, osteoarthritis, and a 20-pack /year history of smoking. Physical examination revealed a tender palpable mass in the left lower quadrant. Laboratory findings were as follows: haemoglobin 7.9 g/L; white cell count 8.5 x 109/L; neutrophil 6.29 x 109/L; platelet 625 x 109/L; C-reactive protein 82mg/L. CT of the chest, abdomen and pelvis identified a large left psoas abscess as seen in (Fig. 1). The psoas abscess was surgically drained and more than one litre of pus was produced. A 24 Fr 3-way catheter was inserted for irrigation of the cavity and a Yates drain was inserted in dependent position for ongoing drainage. The cavity was irrigated with normal saline twice daily, and then reduced to once daily four days post-operatively when the runoff remained clear and there was minimal residual drainage. He was empirically treated with IV Tazocin, and then switched to IV Flucloxacillin three days post-drainage, when sample cultures grew multi-sensitive Staphylococcus aureus (Table 1). He was discharged on oral Flucloxacillin 500mg three times a day and was followed up by ‘hospital in the home’ for daily irrigation post-discharge. A CT scan was performed after removal of the catheter to demonstrate resolution of the psoas abscess (Fig. 2). Two months later, a sinus developed at the left inguinal fossa over the site of drainage. This continued to drain despite management by his general practitioner with regular dressings and several courses of oral Cephalexin 500mg BD. The patient presented again several months later with a one-week history of a painful right thigh mass, which developed after he ‘pulled’ a muscle in his thigh during physiotherapy. He also complained of mild right hip pain on movement. Ultrasound was performed with the provisional diagnosis of a haematoma. Incision and drainage was performed where 450 ml of pus was drained. Cultures grew the same strain of Staphylococcus aureus as from the left psoas abscess (Table 1). A sinus formed on the right thigh also, which continued to discharge pus following the procedure. During this admission a sinogram was performed to investigate the persisting sinus from the left psoas abscess drainage site and revealed that it was communicating directly with his left total hip replacement. Interestingly he did not complain of any left hip symptoms. Radiograph of the left hip showed a small lucency at the tip of the prosthesis and below the medial calcar; the prosthesis was otherwise well fixed.
First stage revision of the left hip was performed through a posterior approach with extraction of the infected hip replacement and thorough debridement. Antibiotic impregnated (4g Vancomycin) cement spacer was inserted. Post-operatively, he was treated empirically with IV Vancomycin. The same strain of Staphylococcus aureus was isolated from left hip fluid (Table 1), and microbial sensitivity results directed the change of the antimicrobial regimen to IV Flucloxacillin. This was later changed to a two-week course of oral Dicloxacillin and Rifampicin upon normalisation of the inflammatory marker, CRP to 8.
Second stage revision of the left hip was performed three months after the first stage using the posterior approach. No sign of infection was noted in the left hip and this was confirmed with culture results (Table 1). MRI of the right hip was performed to investigate the persistent discharge from the right thigh sinus and a fluctuant right buttock mass noted during theatre. A prominent anterolateral right thigh sinus, which extended into the right hip joint could be seen. There was a large erosion posteroinferomedial to the right acetabulum, likely extending from the joint, and a very large posterior collection, mostly deep to the right gluteus maximus. Under local anaesthesia and ultrasound guidance, the right buttock collection was accessed with an 18G needle but only a small amount of blood could be aspirated. The aspirate was sent for culture; no pathogen was grown. This was most likely to represent a solidified uninfected haematoma.
The patient underwent first-stage revision of the right hip two months later. The hip joint was exposed from the posterior approach. Copious amounts of pus was seen and drained. Following thorough debridement, antibiotic impregnated (4g Vancomycin) cement spacer was again inserted. Treatment with IV Vancomycin and oral Ceftriaxone was commenced post- operatively. All specimens collected from the right hip grew the same strain of Staphylococcus aureus as before (Table 1), and IV Flucloxacillin 2g TDS was commenced according to susceptibility results. This was switched to oral antibiotics upon discharge. Eight weeks later when the patient was off antibiotics and his CRP normalized he underwent second stage revision of the right hip. Once again no sign of infection was noted in the joint. He was on IV Flucloxacillin postoperatively, which were ceased when intraoperative samples did not culture any pathogens (Table 1).
The patient received a period of inpatient rehabilitation and was discharged 13 days after surgery. Upon follow-up at six months, he remained clinically well and was mobilizing with two crutches. Pathology results were also unremarkable with normal infective and inflammatory markers. Image 3 shows the X-rays as the patient progressed through the various stages.
After radical debridement, removal of all components and taking at least five tissue samples for bacteriologic and histologic assessments, the acetabular component is cemented loosely and femoral fixation is achieved by means of a press-fit or late proximal cementation so that both are removed easily at the second stage without damaging bone stock. Postoperatively, the patient is allowed to mobilise partial weight-bearing with crutches and is discharged home when deemed safe. Antibiotic therapy tailored to the sensitivities of intraoperative cultures is continued for 4 to 6 weeks. The decision to proceed with insertion of a new prosthesis is determined if the culture of a hip aspirate performed 4 weeks after discontinuation of antibiotics is negative and inflammatory markers suggest resolution of infection (ESR ]. After the reimplantation procedure, patients are followed clinically and with ESR and CRP levels for any signs of recurring infection. Systemic antibiotics are discontinued. However, if at the second stage there is clinical evidence of ongoing infection, a repeat debridement procedure is performed with new culture specimens sent for microbiology and systemic antibiotics are adjusted accordingly. At this stage, either a repeat PROSTALAC insertion or a salvage procedure is considered after discussion of treatment options with the patient.
These infections require often demanding management procedures which can be associated with prolonged and complicated treatment courses. Classification of hip joint infections allows the orthopaedic surgeon not only to define the actual status of the infected joint, but also choose the most adequate treatment option, plan the prosthesis reimplantation in case of a hardware explantation and make any statements regarding the prognosis.
In conclusion, treatment of late chronic hip joint infections after THA is a challenging problem. The gold standard remains a two-stage revision arthroplasty using antibiotic-impregnated cement spacers which achieves an infection control rate over 90%. Articulating spacers provide the advantages of maintaining limb length and joint mobility, minimising soft-tissue contracture and scarring, and facilitating second-stage reimplantation and therefore, should be used as the first option of treatment for late chronic hip joint infections.
The major aim of a classification system for hip joint infections is to help the orthopaedic surgeon identify the acuteness or chronicity of the infection, predict the complexity of the treatment procedure and ensure that all necessary devices are available at the time of the first revision surgery as well as of further surgical interventions, if necessary. Moreover, a classification system should also permit a valid and reliable comparison of results from similar case mixes. However, due to a variety of different classification systems, there is currently no consensus as to which system is the most appropriate in reflecting the actual severity of the infection, determining the femoral or acetabular bone defects or choosing the ideal treatment procedure.
10. Hofmann AA, Goldberg TD, Tanner AM, Cook TM. Ten-year experience using an articulating antibiotic cement hip spacer for the treatment of chronically infected total hip. 2005;20(7):874-879
Primary surgical indications and antibiotic impregnation of the bone cement at the site of spacer implantation in the treatment of hip joint infections.