In the current prospective, randomized study, two different materials of the same total knee arthroplasty (TKA) system - cobalt-chromium (CoCr) and titanium-nitride (TiN) - are going to be compared with regards to postoperative outcome. Two-hundred patients are planned to be included in the study over a 4-year period, randomly assigned to either the CoCr- or TiN-implant-group. In order to ensure double-blinding, patients will not be informed about the group they had been assigned to. Moreover, no identifying information of the implant used will be written on documents later accessible to nurses and/or physicians at follow-up appointments. Consequently, surgeons of the respective patients will be excluded from study-specific examination of patients. Despite range of motion (ROM), questionnaires (visual analogue scale - VAS; Western Ontario and McMaster Universities Osteoarthritis Index - WOMAC, Forgotten Joint Score - FJS; Knee Society Scoe - KSS) will be used to assess the postoperative outcome. Furthermore, metal ion levels (cobalt, chrom, molybdenum, titanium) in the blood stream of patients will be measured at scheduled follow-up appointments. It is expected that there will not be a measureable difference between the two coating-groups with regards to ROM, functionality, and metal-ion levels over time.
Rationale The present double-blinded study was planned in order to assess whether differences in materials - using one otherwise similar TKA system - would have an effect on postoperative patient outcome. Moreover, metal ion levels will be measured in the blood stream preoperatively (as reference) and upon follow-up, based on previous observations that metal ion levels are increased in serum following TKA, without any relevant influence on outcome. Aims The aim of the present prospective study is to assess whether differences in tribological pairings - i.e. TiN-coating in comparison to CoCr-alloy using a frequently implanted total knee endoprosthesis (ACS® System, Implantcast GmbH, Buxtehude, Germany) - have an effect on postoperative range of motion (ROM) and patient satisfaction, reflected by Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Forgotten Joint Score (FJS), Knee Society Score (KSS), Visual Analogue Scale (VAS). Moreover, metal ion levels will be tested in both groups to monitor their concentration in the blood stream, usually reflecting physiological abrasion. Endpoints The primary endpoint of the current study is the functional outcome of patients with TKA on a CoCrMo- basis in comparison to a TiN-coated implant. The secondary endpoint is the measurement of metal ion levels in the blood stream and their potential dynamics over time. Methods Two-hundred patients will be prospectively included in the study over a 4-year period, with 100 being randomly assigned to group A (TiN-coating) and 100 to group B (CoCr-alloy). Random assignment will be carried out via an automatic randomisation system run by a local study nurse. Pre- and postoperatively, range of motion (ROM), visual analogue scale (VAS) score and specific questionnaires - i.e. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Forgotten Joint Score (FJS), Knee Society Score (KSS) - will be ascertained (Table 1) in order to allow comparison of potential differences between group A and B during follow-up. Furthermore, preoperatively, at 6 months, 12 months, 24 months and 60 months, metal ion levels (cobalt, chromium, molybdenum, titanium) in the blood stream will be measured in each patient (6ml tubes). Measurements of metal ion levels will be performed at an external institution. The phase of active recruiting is planned for 4 years, with 50 patients being included per year on average. With the last patients anticipated to being included at the end of the 4th year, their follow-up will be finished 9 years after study initiation. Randomisation and Blinding All patients will be informed prior to potential study participation whether or not to they would like to participate, clarifying that refusal will not have any negative impact on further treatment. In case patients agree to participate, they will be randomly assigned to either group A or B. Double-blinding will be made possible by not informing patients whether they had been allocated to group A or B and by not directly revealing information about the implant type used on medical records that will later be accessible to the study nurse and/or physicians during clinical examinations at follow- up. Therefore, it will be necessary to exclude those surgeons participating in the surgeries of the respective patients from examining them during follow-up, in order to maintain blinding. Prior to follow-up appointments, surgeons who had not participated in surgeries of the respective patients will thus be informed by the study nurse in order to perform clinical examination, radiological follow-up and questionnaires. Expected Results As patients receive the identical orthopaedic implant during an identical surgical procedure for comparable indications, it is expected that the differences in alloy (i.e. TiN vs. CoCr) will not have a measurable effect on postoperative patient outcome. Neither there is expected to be a difference in metal ion levels in the blood stream over time between groups.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
TiN-alloy based TKA implanted for knee osteoarthritis.
CoCr-coating based TKA implanted for knee osteoarthritis.
Department of Orthopaedics and Trauma, Medical University of Graz, Austria
Graz, Austria
Change of Postoperative functional outcome - ROM with goniometer
Range of motion (ROM), assessed with goniometer approved for medical issues
Time frame: Preoperatively, postoperative week 6, month 12, month 24, month 60.
Change of Postoperative functional outcome - pain
VAS score (Visual Analogue Scale; 0 = no pain, 10 = severe pain)
Time frame: Preoperatively, postoperative week 6, month 12, month 24, month 60.
Change of Postoperative functional outcome - Western Ontario and McMaster Universities Arthritis Index (WOMAC)
Assessed by Western Ontario and McMaster Universities Arthritis Index (WOMAC). This index ranges from 0 to 100 points and is based on items pain, physical function and joint stiffness. Lower values indicating better outcomes, whilst higher values point towards worse outcome. Higher scores on the WOMAC indicate a worse outcome
Time frame: Preoperatively, postoperative week 6, month 12, month 24, month 60.
Change of Postoperative functional outcome - FJS
Forgotten Joint Score (FJS) with a scale ranging from 0 to 100, where a high value indicates a better outcome
Time frame: Preoperatively, postoperative week 6, month 12, month 24, month 60.
Change of Postoperative functional outcome - Knee Society Score (KSS)
Knee society score (KSS) is built up by two scores, i.e. "Functional Score" (3 items) and "Knee Score" (7 items), both ranging from 0 to 100 points. The lower the values, the worse the outcome.
Time frame: Preoperatively, postoperative week 6, month 12, month 24, month 60.
Change of Metal ion levels in blood stream
Measurement of titanium, cobalt, chromium, molybdenum in blood stream at specific time-points.
Time frame: Preoperatively, month 6, month 12, month 24, month 60.
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