Aims

A novel enhanced cement fixation (EF) tibial implant with deeper cement pockets and a more roughened bonding surface was released to market for an existing total knee arthroplasty (TKA) system.This randomized controlled trial assessed fixation of the both the EF (ATTUNE S+) and standard (Std; ATTUNE S) using radiostereometric analysis.

Aims

Instability is a common cause of failure after total hip arthroplasty. A novel reverse total hip has been developed, with a femoral cup and acetabular ball, creating enhanced mechanical stability. The purpose of this study was to assess the implant fixation using radiostereometric analysis (RSA), and the clinical safety and efficacy of this novel design.

Purpose

Current practice requires all post-operative hip and knee arthroplasty patients complete a series of clinical questionnaires at each visit. The patients responses to these questionnaires are used as a clinical evaluation tool for the surgeons to assess functionality, satisfaction and pain at routine pre and post-operative visits. The recent installation of 4 touch screen computer terminals, located in the patient waiting area, has created the opportunity to have the patients complete these questionnaires by using only the touch screen entry system. This eliminates the need for clinic staff to manually enter the patients responses into the clinics database, eliminate potential data entry errors, and will significantly reduce the amount of time and paper required to prepare questionnaires for each patient. In addition to possibly increasing the volume of data we can collect in our clinic, this also allows the surgeon to have immediate access to the patients responses which can be reviewed prior to seeing the patient in the office. Our goal was to determine the overall level of patient satisfaction with using the new touch screen direct entry system, the efficiency of completion and the quality of data entry occurring from the direct entry system.

Purpose: The purpose of this study is to measure in vivo linear head penetration of a newer generation highly crosslinked liner (X3, Stryker Orthopedics) using Radiostereometric Analysis (RSA).

Method: The 12 hips (11 patients) included in this study are a subset from a larger randomized controlled trial comparing Exeter stem migration in cement mantles with and without Tobramycin. Criteria for inclusion in this subset were the use of an uncemented Trident acetabular component containing X3 polyethylene in combination with a 32 mm stainless steel femoral head. The average age was 72.7 years (range 65 to 80), and there was an equal gender distribution. RSA examinations were taken with patients lying supine at six weeks, six months, one year, and two years postoperatively. The six week examinations were used as the reference examinations for measuring head penetration. Radiographic measurements and analyses were performed with the UmRSA software suite version 6.0 (RSA Biomedical, Umea, Sweden). Head penetration was determined via edge-detection measurements of the femoral head and acetabular cup.

Results: The mean cumulative femoral head penetration at 6 months was 0.23 mm; this remained statistically unchanged both at 1 year: 0.20mm (p=0.69, 95% UCL of the difference: +0.15mm) and 2 years: 0.25mm (p=0.77, 95% UCL of the difference: +0.10mm).

Conclusion: It is generally recognized that femoral head penetration of more than 0.1 mm per year can result in osteolysis. The purpose of cross linking polyethylene is to reduce wear to below this level. The results of this study show that after an initial bedding in of approximately 0.2 mm, femoral head penetration is not detectable over the subsequent 18 months. Further follow-up is underway to confirm that this promising reduction in wear is maintained.

Purpose: While it is generally accepted that the results of revision total knee replacement (TKR) are inferior to those of primary TKR, there is little published information documenting this. The purpose of this study is to compare patient-reported functional outcomes following primary and revision total knee arthroplasty patients using standardized, validated outcome metrics.

Method: Using data from an academic arthroplasty database, we undertook a review of health related quality of life (SF-12) and disease specific measures (WOMAC) of patients undergoing either primary or revision TKR. The sample included 39 patients who had undergone revision TKR for reasons other than infection, and 39 patients who had undergone primary TKR matched by gender, age, modified Charnley classification, and number of years of follow-up. Student’s t-test was used to compare both groups. Average length of follow up was 2 years.

Results: The mean age was 65 years. Sixty percent (67%) of the patients were female.

Despite being matched by age, gender and modified Charnley classification, there were significant differences in post-operative functional scores. The revision TKR group’s mean WOMAC score was 73 (SD 17), compared to the primary group’s mean score of 84 (SD 14), p=0.002. Similarly, the revision group’s mean SF-12 PCS score was 35 (SD 8) compared to the primary group’s superior score of 44 (SD 10), p< 0.0001. There was no differences detected in post-operative SF-12 mental component scores; 49 (SD 12) for the revision group compared to 53 (SD 10) for the primary group, p=0.11.

Conclusion: This study confirms the general clinical impression that the functional results of revision TKR are inferior to primary TKR, as measured by both the WOMAC and SF-12 tools.

Purpose: The purpose of this study is to determine if the addition of Tobramycin antibiotic powder to cement for primary hip replacement surgery increases the risk of long term aseptic loosening. This was accomplished by measurement of implant micromotion with Radiostereometric Analysis (RSA).

Method: Exeter femoral stems and Trident acetabular components were implanted into 33 patients. Stems were cemented in a randomized manner with either Simplex P or Simplex T. Tantalum beads were injected into the femur to serve as reference points for RSA measurements. RSA examinations were taken with supine positioning at six weeks, six months, one year, and two years post-operatively. Radiographic measurements and analyses were performed with the UmRSA software suite version 6.0 (RSA Biomedical, Umea, Sweden). Distal migration of the stem centroid was measured at each follow-up period and the mean migration rates for both groups were determined. Non-inferiority testing of stem migration in Simplex T compared to Simplex P was accomplished using a one sided t-test, with the significance level set at 0.05. A clinically inferior additional amount of distal migration was set at 0.4mm/yr.

Results: Eleven patients were excluded from the study: seven patients either dropped out of the study or missed the six week and/or two year follow-up examinations, two patients had radiographic image quality issues, and two patients had loosening of their tantalum markers in subsequent follow-ups. Of the remaining 22 patients, eight were male and 14 were female, with an average age at time of surgery of 71.2 (range, 63–81) years. The mean total distal migrations for the Tobramycin and non-Tobramycin cement groups at two years were 0.891 and 0.732 mm, respectively; the mean stem migration rates were 0.263 and 0.179 mm/yr, respectively. The differences in total distal migration and stem migration rate were not statistically significant (P = 0.06 and UCL = 0.173, respectively).

Conclusion: The addition of Tobramycin to Simplex cement does not appear to impact the distal migration pattern for a polished tapered cemented hip stem at two years. This finding suggests that Tobramycin does not have any clinically relevant deleterious effects on the in vivo mechanical properties of Simplex cement.