Surgical technique and preliminary results of a moulded, mobile spacer for the treatment of periprosthetic joint infection of the knee

OBJECTIVE

Mobile knee spacers can be utilized in the first stage of a two-stage exchange in periprosthetic joint infection or septic arthritis of the knee to prevent soft tissue contraction, enable local antibiotic elution, and improve patient mobility. Commercially made moulds enable the surgeon to prepare a reproducible spacer design and match the preparation of the arthroplasty, which will be carried out in a second step.

INDICATIONS

Periprosthetic joint infection of the knee and severe cases of septic arthritis of the knee with advanced destruction/infiltration of the cartilage.

CONTRAINDICATIONS

Antibiotic resistance of the microbiological pathogen to available antibiotic agents, incompliant patient, large osseous defect preventing proper fixation, known allergy to polymethylmethacrylate (PMMA) or antibiotic, severe soft tissue damage with high ligament instability, especially deterioration of extensor mechanism and insufficient patella/quadricep tendon.

SURGICAL TECHNIQUE

After thorough debridement and removal of all foreign material, cutting blocks are used to shape femur and tibia to the implant design required. Using a silicone mould, PMMA with suitable antibiotics is moulded into the shape of the future implant. After polymerization, the implants are fixed onto the bone with additional PMMA without pressurize for the sake of easy removal.

POSTOPERATIVE MANAGEMENT

Partial weight bearing with no restriction of flexion/extension while spacer is in place; second stage reimplantation as soon as infection is controlled.

RESULTS

In all, 22 cases were treated, mostly with a PMMA spacer containing gentamicin and vancomycin. Pathogens were detected in 13 of 22 cases (59%). We observed two complications (9%). Twenty of 22 patients (86%) were reimplanted with a new arthroplasty; 16 of the 20 patients remained revision-free and infection-free at the last follow-up (average time to follow-up 13 months, range 1-46 months). Average range of motion in flexion and extension at follow-up was 98°.

Commercially manufactured spacers for the treatment of periprosthetic joint infection of the hip

BACKGROUND

Periprosthetic joint infection remains a common and serious complication after hip arthroplasty. To improve function and patient comfort after joint removal in two-stage revision, commercially manufactured spacers for the hip joint allow retention of the anatomical joint geometry thereby limiting soft tissue contraction and allow mobilization.

INDICATIONS

Periprosthetic joint infection of the hip, septic arthritis with severe destruction of the hip cartilage and/or bone requiring arthroplasty.

CONTRAINDICATIONS

Allergies to polymethylmethacrylate (PMMA) or antibiotics, severe hip dysplasia with insufficient cranial support, incompliant patient, large osseous defect of the acetabulum, insufficient metaphyseal/diaphyseal support of the femoral bone, resistance of the microbiological pathogen to spacer-inert antibiotic medication, inability to perform primary wound closure requiring temporary open-wound therapy.

SURGICAL TECHNIQUE

Preoperative templating on radiograph; removal of joint prosthesis and thorough debridement with removal of all foreign material; trial spacer selection and insertion and trial reduction of the joint, fixing the spacer with PMMA to the proximal femur, final reduction, radiograph and stability test.

RESULTS

Data were analyzed from patients treated between 2016 and 2021. In all, 20 patients were treated with preformed spacers and 16 with custom-made spacers. Pathogens were detected in 23 of the 36 cases (64%). Polymicrobial infections were present in 8 of 36 cases (22%). In patients who received preformed spacers, there were 6 cases of spacer-related complications (30%). Of the 36 patients (83%), 30 were reimplanted with a new implant; 3 patients died due to septic or other complications before reimplantation (8%). Average follow-up was 20.2 months after reimplantation. There were no major differences between the two groups of spacers. Patient comfort was not measured.

Two-stage exchange for PJI with co-existing cerclages for fracture: higher rates of early re-infections and difficult to treat microbes

INTRODUCTION

Periprosthetic joint infections (PJI) with osteosynthesis material for contemporaneous fractures are a challenging, yet poorly described condition. This study will analyze PJI with co-existing fractures treated with cerclages and two-stage exchange.

MATERIALS AND METHODS

Patients with and without cerclages for coexisting periprosthetic fractures, undergoing two-stage exchange for PJI of hip or knee, between 06/2013 and 02/2016, were compared concerning baseline characteristics and re-infection rate in the course of a 2 year follow-up. All patients were treated with a standardized two-stage protocol. A PJI was defined according to the EBJIS criteria. All foreign material, including cerclages, was sent in for sonication for microbiological analysis.

RESULTS

Ninety-six patients treated with two-stage exchange for PJI could be included. Co-existing fractures treated with cerclage were identified in nine patients (9.3%, study group). Diaphyseal femoral simple in five cases (AO2A3) and proximal intertrochanteric in three cases (AO1A3) were the leading fracture locations. In one patient, cerclage implantation was performed prior to prosthesis explantation, in six, during prosthesis explantation, and in two, in the course of prosthesis reimplantation. The study group showed a significantly higher rate of difficult to treat microbes (44.4%; 8.0%; p = .001), Charlson Comorbidity Index (5.4; 3.7; p = .033), relapse infections with the same microbe (22.2%; 1.1%; p = .001), and early-onset infections (< 30 days) (11.1%; 1.1%; p = .046), than the comparison two-stage exchange group without fractures. In contrast, age (72.5 study group; 68.2 comparison group; p = .224), rate of revisions for PJI in the past (55.5%; 51.7%; p = .827), and total re-infection rate (22.2%; 10.3%; p = .287) did not show a difference.

CONCLUSION

PJI with co-existing cerclages for fractures were associated with multi-resistant microbes, relapse by the same microbe and early-onset re-infections. Cerclages might be considered a potential source of re-infection during a two-stage exchange. However, statistical weaknesses and a small study group must be considered limitations of the study.

Does Treatment at a Specialized Prosthetic Joint Infection Center Improve the Rate of Reimplantation

INTRODUCTION

Two-Stage exchange arthroplasty is currently the preferred treatment method for periprosthetic joint infection (PJI). The effectiveness of this strategy in returning patients to premorbid function has recently been challenged. In a review of 18, 535 PJI knee patients, 38% did not undergo reimplantation (17). In another review of 18,156 hip and knee PJI patients, 43% did not undergo reimplantation (16). These disturbing statistics led us to ask whether treatment at a specialized prosthetic joint infection center could improve the rate of reimplantation compared to the previously noted studies from large national administrative databases.

METHODS

A retrospective review of our registry was performed to identify 390 patients who underwent a two-stage exchange after total knee arthroplasty (TKA) and total hip arthroplasty (THA) who had a confirmed chronic bacterial PJI, defined by Musculoskeletal Infection Society (MSIS) criteria, from January 2010 through December 2019. Variables included number of joints resected, number replanted, and the number not replanted.

RESULTS

Of the 390 patients undergoing 2-stage treatment, 386 of 390 (99%) were reimplanted and 4of 390 (1%) were not replanted due to medical issues.

CONCLUSION

We have shown that 2-stage treatment at a PJI Center significantly improves the rate of reimplantation. A specialized Prosthetic Joint Infection Center with experienced revision surgeons doing high volume infection procedures, complemented by infectious disease and medical consultants familiar with the special needs of PJI patients may be advantageous. A national network of such centers may have the ability to improve outcomes, standardize treatment protocols, and allow for collaborative research.

Partial two-stage exchange: an alternative method for infected total hip arthroplasty

Background

Total two-stage exchange is commonly used in clinical practice as a treatment for infected total hip arthroplasty (THA); however, this approach involves considerable limitations, including significant bone loss and severe trauma. This retrospective cohort study was conducted to evaluate clinical outcomes following the use of partial two-stage exchange (PTE) for infected THA.

Methods

We performed a retrospective analysis of 28 patients with infected THA who were treated by PTE between September 2000 and June 2019. Eligibility for PTE was limited to patients with a well-fixed femoral stem prosthesis. In the first stage of the operation, the femoral stem prosthesis was preserved; subsequently, the acetabular prosthesis, liner, and head were replaced with an antibiotic-loaded spacer. The new prosthesis was then implanted into patients and monitored for at least 3 months to ensure freedom from infection.

Results

Patients were followed for an average of 4 years (range, 2–11 years), with an overall success rate of 85.7% (24/28). The mean Harris hip score at the final follow-up was 76.2 ± 11.7 points.

Conclusions

The findings of this study suggest that PTE could be an acceptable option for a subset of patients with infected THA, offering a satisfactory infection control rate and clinical outcomes comparable to those of total two-stage exchange, but with less harm.

Difficult to treat: are there organism-dependent differences and overall risk factors in success rates for two-stage knee revision?

OBJECTIVES

Failure after two-stage procedure for periprosthetic joint infection (PJI) is a rare, but devastating complication. Some authors assume a correlation of underlying organisms and recurrence rate. Methicillin-resistant Staphylococci (MRS) and other organisms (quinolone-resistant Gram-negative bacteria, rifampicin-resistant Staphylococcus, Enterococcus, and Candida) are meant to be "difficult to treat" (DTT) with an inferior outcome for two-stage revision. In addition to the type of bacteria, some more risk factors seem to be present. The aim of this study was (1) to detect a difference of reinfection rates between reinfection-causing groups of bacteria ["difficult to treat" (DTT), "easy to treat" (ETT) and methicillin-resistant staphylococci (MRS)] after a two-stage procedure, and (2) find overall risk factors for reinfection in a standardized long (spacer insertion for at least 6 weeks) two-stage procedure for periprosthetic knee infection.

METHODS

One hundred and thirty-seven two-stage revisions for periprosthetic knee infection were performed at one tertiary referral center. Finally, 96 patients could be included for analyses. Possible risk factors (comorbidities, prior surgery, etc.) and the types of organisms were documented. Quinolone-resistant Gram-negative bacteria, rifampicin-resistant Staphylococcus, Enterococcus, and Candida were classified as "difficult to treat" (DTT). Methicillin-resistant Staphylococci were summarized as "MRS", all other organism are summarized as "easy to treat" (ETT). Statistical analyses included univariate analysis (t test, Fisher's exact test, Chi square test) and logistic regression analysis.

RESULTS

There were no statistical significant differences in recurrent infection rates between organism groups (DTT vs. ETT, p = 0.674; DTT vs. MRS, p = 0.705; ETT vs. MRS, p = 0.537). Risk factors seem to be "need of revision after first stage" (p = 0.019, OR 5.62) or completed second stage (p = 0.000, OR 29.07), numbers of surgeries (p = 0.028) and alcohol abuse (p = 0.019, OR 5.62).

CONCLUSIONS

Revision needed during or after a two-stage exchange, numbers of surgeries and alcohol abuse are risk factors for recurrence, a different recurrence rates between organism-groups cannot be shown. The absence of significant differences in recurrence rates points to the importance of the individuality of each periprosthetic infection case: a reduction of necessary surgeries (with a thorough debridement, appropriate antibiotic addition to spacers) and the control of comorbidities (alcohol abuse) appear to be essential components of a two-stage exchange.

Partial implant retention in two-stage exchange for chronic infected total hip arthroplasty

BACKGROUND

The efficacy of partial retention of well-fixed components during two-stage exchange for chronic total hip arthroplasty (THA) infection has remained unknown.

METHODS

A total of 14 patients with chronic infected THA were treated with damage control two-stage revision, including selective retention of the well-fixed femoral or acetabular component, aggressive debridement, antibiotic-laden cement spacer, antibiotic therapy, and delayed reimplantation. Indications for this treatment included chronic infected THAs with ingrown femoral or acetabular component and positive microbial growth with sensitive antibiotics. We excluded patients with acute infection; negative microbial growth; positive pathogen with high-virulence bacterial infections and multiple drug-resistant bacteria such as methicillin-resistant Staphylococcus aureus, fungi, and Mycobacterium tuberculosis; sinus formation; a prior failure for periprosthetic joint infection (PJI) treatment; and obvious bone resorption in both femoral and acetabulum side. During the study period, this represented 3.3% (14/425) of the patients treated for infected THA. Minimum follow-up was three  years. None of the 14 patients in this series were lost to follow-up. Successful treatment was defined according to a modified Delphi-based international multidisciplinary consensus.

RESULTS

No repeated debridement and recurrence of infection occurred during the study period; no patient need chronic antibiotic suppression. Successful treatment of chronic PJI was achieved in all patients. Despite the high peri-operative complication rate, no severe consequences were observed. The mean Harris Hip Score was 86 (range, 82-92; SD, 3.3).

CONCLUSIONS

The selective partial implant retention two-stage revision for chronic PJI may be a treatment option in properly selected patients with low virulence bugs.

High cure rate of periprosthetic hip joint infection with multidisciplinary team approach using standardized two-stage exchange

Background

Two-stage exchange arthroplasty is still the preferred treatment choice for chronic PJI. However, the results remain unpredictable. We analyzed the treatment success of patients with an infected hip prosthesis, who were treated according to a standardized algorithm with a multidisciplinary team approach and evaluated with a strict definition of failure.

Methods

In this single-center prospective cohort study, all hip PJI episodes from March 2013 to May 2015 were included. Treatment failure was assessed according to the Delphi-based consensus definition. The Kaplan-Meier survival method was used to estimate the probability of infection-free survival. Patients were dichotomized into two groups depending on the number of previous septic revisions, duration of prosthesis-free interval, positive culture with difficult-to-treat microorganisms, microbiology at explantation, and microbiology at reimplantation.

Results

Eighty-four patients with hip PJI were the subject of this study. The most common isolated microorganisms were coagulase-negative staphylococci (CNS) followed by Staphylococcus aureus and Propionibacterium. Almost half of the study cohort (46%) had at least one previous septic revision before admission. The Kaplan-Meier estimated infection-free survival after 3 years was 89.3% (95% CI, 80% to 94%) with 30 patients at risk. The mean follow-up was 33.1 months (range, 24–48 months) with successful treatment of PJI. There were no statistical differences in infect eradication rate among the dichotomized groups.

Conclusions

High infect eradication rates were achieved in a challenging cohort using a standardized two-stage exchange supported by a multidisciplinary approach.

Insufficient sensitivity of joint aspiration during the two-stage exchange of the hip with spacers

Background

Evaluation of infection persistence during the two-stage exchange of the hip is challenging. Joint aspiration before reconstruction is supposed to rule out infection persistence. Sensitivity and specificity of synovial fluid culture and synovial leucocyte count for detecting infection persistence during the two-stage exchange of the hip were evaluated.

Methods

Ninety-two aspirations before planned joint reconstruction during the two-stage exchange with spacers of the hip were retrospectively analyzed.

Results

The sensitivity and specificity of synovial fluid culture was 4.6 and 94.3%. The sensitivity and specificity of synovial leucocyte count at a cut-off value of 2000 cells/μl was 25.0 and 96.9%. C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) values were significantly higher before prosthesis removal and reconstruction or spacer exchange (p = 0.00; p = 0.013 and p = 0.039; p = 0.002) in the infection persistence group. Receiver operating characteristic area under the curve values before prosthesis removal and reconstruction or spacer exchange for ESR were lower (0.516 and 0.635) than for CRP (0.720 and 0.671).

Conclusions

Synovial fluid culture and leucocyte count cannot rule out infection persistence during the two-stage exchange of the hip.

Does knee revision after an articulated spacer implant provide normal gait restoration?

PURPOSE

The aim of this study was to quantitatively evaluate gait parameters in patients who underwent a revision procedure after an interval articulated spacer for septic knee prosthesis.

METHODS

Ten adult subjects underwent three-dimensional computerized gait analysis 12 months after second-stage knee revision procedure. Kinematic and kinetic parameters were acquired and compared with a normal reference population. Data were also compared with those collected in a previous study, in which the same cohort of patients underwent gait analysis 8-14 weeks after spacer implantation.

RESULTS

Kinematic and kinetic parameters did not show any significant difference between the affected and unaffected limb. Compared to normal reference population, patients treated with revision knee prosthesis showed a reduced mean gait velocity, step frequency, stride and step length, average knee range of motion, knee power and ground reaction forces. When comparing average data with those observed after spacer implant, no difference was observed in kinematic variables, while kinetic analysis demonstrated a significant improvement in knee power.

CONCLUSIONS

This study shows that 1 year after second-stage knee revision surgery, kinematic and kinetic values remain lower than those observed in a normal reference population. Only slight improvements in walking ability are shown, when analysing data in comparison with those collected after a preformed articulated knee spacer. This finding points out the long time to full functional recovery after knee revision surgery and the limited improvement of gait when compared to the one achieved at the time of spacer implant.

Activity of bone cement loaded with daptomycin alone or in combination with gentamicin or PEG600 against Staphylococcus epidermidis biofilms

Daptomycin is a promising candidate for local treatment of bone infection due to its activity against multi-resistant staphylococci. We investigated the activity of antibiotic-loaded PMMA against Staphylococcus epidermidis biofilms using an ultra-sensitive method bacterial heat detection method (microcalorimetry). PMMA cylinders loaded with daptomycin alone or in combination with gentamicin or PEG600, vancomycin and gentamicin were incubated with S. epidermidis-RP62A in tryptic soy broth (TSB) for 72 h. Cylinders were thereafter washed and transferred in microcalorimetry ampoules pre-filled with TSB. Bacterial heat production, proportional to the quantity of biofilm on the PMMA, was measured by isothermal microcalorimetry at 37 °C. Heat detection time was considered time to reach 20 μW. Experiments were performed in duplicate. The heat detection time was 5.7-7.0 h for PMMA without antibiotics. When loaded with 5% of daptomycin, vancomycin or gentamicin, detection times were 5.6-16.4 h, 16.8-35.7 h and 4.7-6.2 h, respectively. No heat was detected when 5% gentamicin or 0.5% PEG600 was added to the daptomycin-loaded PMMA. The study showed that vancomycin was superior to daptomycin and gentamicin in inhbiting staphylococcal adherence in vitro. However, PMMA loaded with daptomycin combined with gentamicin or PEG600 completely inhibited S. epidermidis-biofilm formation. PMMA loaded with these combinations may represent effective strategies for local treatment in the presence of multi-resistant staphylococci.