The aim of this prospective study was to assess safety and effectiveness of Spacer-K, a pre-formed articulating spacer made of gentamicin-impregnated acrylic bone cement. used in two-stage exchange technique for the infected total knee arthroplasty.

32 consecutive patients infected total knee arthroplasty were operated on in two centres. Infection was caused by Coagulase neg. Staphylococcus (21), Staphylococcus aureus (4), and others (4). In 3 case microorganisms were not identified. The mean implantation time of the spacer was 11 weeks (range, 7 to 28 weeks). The rehabilitation program between stages consisted in early range of motion exercises and partial weight-bearing. In one patient removal of the spacer and insertion of a molded cement block with vancomycin was necessary because of insurgence of methicillin-resistant Staphylococcus aureus.

The mean follow-up of 32 knees after removal of the spacer and insertion of the new prosthesis was 40 months (range, 24 to 75 months. The mean Knee Society functional score during spacer management was rated 75 points (range, 41 to 91 points) and was rated 87 points (range, 77 to 97 points) at latest follow-up. Preoperative range of motion improved markedly after removal of the infected prosthesis and insertion of the spacer. Neither breakage nor clinically relevant surface wear were detected. No implant-related complications were observed. Bone stock remained unchanged during the whole management process.

The Spacer-K is safe and effective for the management of the infected total knee arthroplasty.

To obtain a good outcome in TKA is mandatory to reach a balanced flexion-extension gap. That requires, during surgery, to choose the amount of bone resection and the position of the prosthetic component, mainly the femoral one. These choices are based upon some bone landmarks, but overall could be based upon a proper ligament’s tension, as a preview of ideal kinematics.> About this topic several Authors published in the last decade, but the determination of a value of ligament’s tension still remains a big issue.

So we made an hydraulic knee analyzer (HKA® ) computer integrated and we tested and validated by a cadaveric study. Aims of this study are: to validate the reproducibility, in vivo, of the results of the cadaveric study, and subsequently to evaluate the outcome between two groups of patients undergone to surgery, one by conventional technique and the other by C.A.S. The previous cadaveric study, that was done on ten fresh knees by HKA®, highlighted a relation between ligament’s tension in flexion and in extension, 4 bar vs 6 bar. Twenty patients were operated by C.A.S. (Navitrack® Centerpulse-Zimmer) and HKA®, Twenty patients were operated conventionally, by the same surgeon and utilizing the same prosthesis (Innex® Centerpulse-Zimmer). Preoperative and postoperative study was performed by: long lenghth lower limb x-ray, IKSS score and SF 36 score.

In all the C.A.S. patients it’s got a rectangular and balanced gap, both in flexion and extension, utilizing a 4 bar in flexion and 6 bar in extension, as shown in the cadaveric study.

The comparison between two groups of patients has underlined a better functional outcome in the C.A.S. group.

Two-stage exchange technique is currently considered the standard treatment for the infected total knee arthroplasty, but the clinical outcomes associated with the use of articulating bone cementspacers are not well established. Spacer-K is a pre-formed articulatingspacer made of genta-micin-impregnated acrylic cement. The aim of this prospective study was to assess safety and effectiveness of Spacer-K for the management of the infected total knee arthroplasty.

Twenty-two consecutive patients were operated on in two centres. Infection was caused by Coagulase neg. Staphylococcus (11cases), Staphylococcus aureus (3), and others (5). In 3 cases microorganisms were not identified. The mean implantation time of the spacer was 11 weeks(range, 7 to 28 weeks). The rehabilitation program between stages consistedin early range of motion exercises and partial weight-bearing. In one patient removal of the spacer and insertion of a molded cement block with vancomycin was necessary because of insurgence of MRSA.

The mean follow-up of 21 knees after removal of the spacer and insertion of the new prosthesis was 28 months (6 to 45 months). In one patient removal of the spacer and insertion of a molded cement block with vancomycin was necessary following insurgence of methi-cillin-resistant Staphylococcus aureus isolated between stages. No patient had recurrence of infection at latest follow-up. The mean Knee Society functional score during spacer management was rated 76 points (range 55 to 80 points) and was rated 86 points (range, 76 to 90 points) at latest follow-up. Preoperative range of motion improved markedly after removal of the infected pros-thesis and insertion of the spacer. Neither breakage, nor clinically relevant wear of the spacer were detected, and no complications related to the device were observed

The Spacer-K is safe and effective for the management of the infected total knee arthroplasty.

A comparative prospectic randomized study has been performed between two groups of patients, one undergone to surgery by conventional technique (A) and the other by CAS (B). In all the patients the same type of prosthesis, Innex Ucor® (Zimmer), was implanted by the same surgeon. The surgical technique has been “tibia first” with preliminary ligament balance in both groups.

In CAS technique has been utilized the Navitrack® (Orthosoft) system integrated by an hydraulic tensor, Hydraulic Knee Analyzer® (Zimmer), able to measure the applied force and the obtained space.

Evaluation criteria have been: x-ray alignment (HKA), IKSS, SF-36. Minimum follow-up has been 12 months.

The data shows a statistically significant difference in the group B related to HKA (p< 0,0001) and functional score (p= 0,009). The knee score is “non significant” but it has a “tendency value”, even if the pain score is “significant” (p=0,008). SF-36 isn’t “significant”.

The group B has shown an important reduction of clinical and radiographic outliers.

A knee functional spacer made of antibiotic-loaded acrylic cement was used for treatment of infected TKA with two-stage exchange arthroplasty procedure.

The Spacer K is a preformed articulated spacer with the characteristics of an ultra-congruent condylar knee-prosthesis, made of acrylic cement impregnated with antibiotic (gentamicin). The device, industrially pre-formed in 3 sizes (Spacer K, Tecres), with standardised mechanical and pharmacological performances, was implanted in 21 consecutive patients all affected by late (8) infection according Segawa classification. Infection was caused by CoNs (16 cases), MSSA (1), Micrococcus spp (1), Enterococcus spp. (1). In 2 cases the germ was not detected. All knees presented the integrity of extensor apparatus and of peripheral ligaments (medial), furthermore type I & II bone loss according to Engh’s classification. Mean implantation time was 12 wks. Post-op following std. rehabilitation program as with primary TKR. We evaluated: healing of infection (clinical parameters, CPR, ESR, biopsy); clinical results and functional outcome (KSS); mechanical device behaviour (breakage, wear: macro – and microscopic surface evaluation, histological examination of peri-prosthetic tissues); possible related complications (bone loss, instability or dislocation, loosening: intra- and postoperative evaluation, x-ray study). The results obtained shows that the spacer K is effective and safe.

Background: A knee functional spacer made of antibiotic-loaded acrylic cement was used for treatment of infected TKA with two-stage exchange arthroplasty procedure.

Materials and Methods: Spacer K is a preformed articulated spacer with the characteristics of an ultra-congruent condylar knee-prosthesis, made of acrylic cement impregnated with antibiotic (gentamicin). The device, industrially preformed in 3 sizes (commercial name Spacer K, Tecres), with standardised mechanical and pharmacological performances, was implanted in 20 consecutive patients affected by early (12) and late (8) infection according Segawa classification. Infection was caused by CoNs (14 cases), MSSA (2), Micrococcus spp (1), Enterococcus spp. (1). In 2 cases the germ was not detected. All knees presented the integrity of extensor apparatus and of peripheral ligaments (medial), furthermore type I & II bone loss according to Engh’s classification. Mean implantation time was 12 wks. Post-op following std. rehabilitation program as with primary TKR. We evaluated: healing of infection (clinical parameters, CPR, ESR, biopsy); clinical results and functional outcome (KSS); mechanical device behaviour (breakage, wear: macro – and microscopic surface evaluation, histological examination of peri-prosthetic tissues); possible related complications (bone loss, instability or dislocation, loosening: intra- and postoperative evaluation, x-ray study). .

Results: Minimum F.U. was 6 months, maximum 51. Healing of infection process was observed in all patients. The KSS score, after definitive reimplantation, has been excellent or good in more than 70% of patients as well as the functional score. Pain was absent but in 1 patient (mild); ROM remained unchanged between first and second stage or improved after definitive reimplantation; patients judged the result excellent or good in 85%. The walk ability was good in 60%, excellent in 15%. Seventy seven per cent of patients went on only cructh, but of these at least, one third could walk without anything. the patient’s judgement has been excellent. Neither breakage, or macroscopic wear signs were detected. No complications related to the use of the device were observed. (one case of dislocation due to pre-existing insufficiency of the extensor apparatus)

Conclusions: In a reasoned costs benefits ratio, the use of an articulated knee spacer in two-stage septic revisions should be considered the preferred option.

Introduction Antibiotic-loaded cement spacers are commonly used in the two-stage management of the infected total knee replacement (TKR). Static spacer blocks make exposure and reimplantation difficult because of soft-tissue retraction and muscle shortening. To avoid these problems, a temporary articulating moulded implant has been recently introduced in the marketplace. The device is industrially preformed in three sizes (two articulating components), has standardised mechanical and pharmacological characteristics.

Methods We present a multicentre study designed to assess the safety of the device, patients’ satisfaction and functional outcome at a minimum follow-up of six months. Twenty-four knees have been treated for TKR deep infection due to CNS (15),S.aureus (three),E.coli (one),mixed flora (two), unidentified (three). Continuous passive motion and partial/touch weight-bearing were started after surgery. Second-stage surgery was performed after normalisation of serological parameters, a minimum period of six weeks of antibiotic therapy, and a sterile aspiration of the joint. The spacer was removed and a new prosthesis was inserted in all patients. The mean implantation time of the spacer was 16 weeks (range 8 to 38).

Results Suppression of infection was observed in all patients at a minimum follow-up of six months (mean 14 months). No spacer-related complication (instability, dislodgment, severe wear, fracture) was observed. The range of motion of the knees remained unchanged between the first and second stages and improved after definitive reimplantation. The mean Knee Society Score at last-follow up was 88 points (knee score and functional score). The patients judged the result excellent (three), good (15), satisfactory (five), poor (one).

Conclusion The use of an articulating spacer in the two-stage treatment of infected TKR improves the quality of life of the patient, the ultimate range of motion, facilitates second-stage surgery and the functional recovery. Severe bone loss is a relative contraindication for articulating spacers, as these knee joints may require immobilisation during the resection time interval.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.

Introduction: A novel device for two-stage septic revision of TKA was checked to evaluate for mechanical and pharmacological properties. Methods: The articulated knee spacer is a temporary device made entirely of gentamicin bone cement industrially preformed and available in 3 sizes. It maintains joint space and motion, allowing partial weight-bearing. It provides an in situ release of antibiotic. Static and dynamic mechanical testing was performed according to ISO/DIN 14243-1. Surface rugosity was assessed according to DIN 4768. Pharmacological behaviour was evaluated according to the European Pharmacopoeia. Results: Static mechanical testing: the device resists a load > 10000N (physiological load peak = 2500N). Dynamic mechanical testing: no breakage after 500.000 cycles at 1300N (half load for physiological knee joint). Wear produced by the PMMA-PMMA coupling is not much higher than wear produced by PE-metal coupling. Surface rugosity (polishing effect) decreases of an order of magnitude after 8 weeks of implantation, and no difference is found between 8 weeks and 5 months of implantation. The in vitro gentamicin release in 7 days is around 2% of the initial amount of antibiotic and ranges from 15 mg (small) and 35 mg (large). Conclusions: The articulated knee spacer has excellent mechanical properties comparable to standard prostheses, which guarantee safety of use for the time of implantation foreseen (up to 6 months). As an ancillary property it delivers locally a high concentration of gentamicin.