Introduction

Although total knee arthroplasty (TKA) is generally considered successful, 16–30% of patients are dissatisfied. There are multiple reasons for this, but some of the most frequent reasons for revision are instability and joint stiffness. A possible explanation for this is that the implant alignment is not optimized to ensure joint stability in the individual patient. In this work, we used an artificial neural network (ANN) to learn the relation between a given standard cruciate-retaining (CR) implant position and model-predicted post-operative knee kinematics. The final aim was to find a patient-specific implant alignment that will result in the estimated post-operative knee kinematics closest to the native knee.

Objectives

Implant-related infection is one of the most devastating complications in orthopaedic surgery. Many surface and/or material modifications have been developed in order to minimise this problem; however, most of the in vitro studies did not evaluate bacterial adhesion in the presence of eukaryotic cells, as stated by the ‘race for the surface’ theory. Moreover, the adherence of numerous clinical strains with different initial concentrations has not been studied.

Purpose: To analyse prolonged combinations of oral intracellular-effective antibiotics plus two-stage exchange surgery for treatment of chronic THA and TKA infections.

Materials and Methods: Definition of infected case: more than 3 months from surgery; multiple positive intraoperative cultures and/or active fistulae.

33 patients were treated from 1996 to 2002: 8 THA, 5 hip hemiarthroplasties, 20 TKA.

Bacteriology: 24 Staphylococci of which 16 were methycillin-resistant, 7 multi-resistant Gram-negative, 2 Cory-nebacteriae; 7 polymicrobian.

Antibiotic therapy: two simultaneous oral antibiotics, selected according to bacterial sensitivity and intracel-lular effectiveness (rifampin, ofloxacin, ciprofloxacin, levofloxacin, trimethoprim-sulfamethoxazole, fosfomicin, linezolid, doxiciclin), were used on an outpatient basis (between 1st and 2nd surgery, and after 2nd surgery until serological normalization). Patients received intravenous antibiotics and were in-hospital only for one week after surgery.

Surgery: two-stage exchange with 2nd stage delayed until clinical and serological normalization.

Healing of infection: absence of clinical, serological and radiological evidence of infection along all follow-up.

Prospective follow-up: 24-96 months.

Results: Healing of infection: 32/33 patients (97%).

Treatment failure: 1 patient (TKA) (3%).

THA: 8/8 infections healed: 1 Girdlestone patient (1st stage of exchange) rejected reimplantation; 7 two-stage exchange (good/excellent objective and subjective result).

Hip hemiarthroplasty: 5/5 infections healed: 3 Girdlestone (1st stage of exchange surgery, 2nd stage rejected because of hemiplegia or Alzheimer); 2 two-stage exchange (good/excellent objective and subjective result).

TKA: 19/20 infections healed: 3 resection-arthroplasty (1st stage of exchange surgery, 2nd stage rejected because of Buerger, cirrhosis or Alzheimer); 17 two-stage exchange (15 good/excellent objective and subjective results, 1 patient needed a debridement 2 months after 2nd surgery because of prolonged aseptic drainage and healed uneventfully, 1 failure described).

Conclusions: Prolonged combinations of oral intracellular-effective antibiotics associated with two-stages exchange surgery is a promising alternative for treating deep chronic THA and TKA infections. Longer follow-up and larger series are necessary.