The trabecular metal Monoblock TKR is comprised of a porous tantalum base plate with the polyethylene liner embedded directly in the porous metal. An alternative design, the trabecular metal Modular TKR, allows polyethylene liner insertion into the locking base plate after base plate implantation, but removes the low modulus of elasticity that was inherent in the Monoblock design. The purpose of this study was to compare the fixation of the Monoblock and Modular trabeucular metal base plates in a randomised controlled trial.

Fifty subjects (30 female) were randomly assigned to receive the uncemented trabecular metal Monoblock or uncemented trabecular metal Modular knee replacement. A standard procedure of tantalum marker insertion in the proximal tibial and polyethylene liner was followed with uniplanar radiostereometric analysis (RSA) examinations immediately post-operatively and at 6 week, 3 month, 6 month, and 12 month follow-ups. The study was approved by the Research Ethics Board and all subjects signed an Informed Consent Form.

Twenty-one subjects received Monoblock components and 20 received Modular components. An intra-operative decision to use cemented implants occurred in 5 cases and 4 subjects did not proceed to surgery after enrollment. The clinical precision of implant migration measured as maximum total point motion (MTPM) was 0.13 mm (upper limit of 95% confidence interval of double exams). Implant migration at 12 months was 0.88 ± 0.64 mm (mean and standard deviation; range 0.21 – 2.84 mm) for the Monoblock group and 1.60 ± 1.51 mm (mean and standard deviation; range 0.27 – 6.23 mm) for the Modular group. Group differences in 12 month migration approached clinical significance (p = 0.052, Mann Whitney U-test).

High early implant migration is associated with an increased risk for late aseptic loosening. Although not statistically significant, the mean migration for the Modular component group was nearly twice that of the Monoblock, which places it at the 1.6 mm threshold for “unacceptable” early migration (Pijls et al 2012). This finding is concerning in light of the recent recall of a similar trabecular metal modular knee replacement and adds validity to the use of RSA in the introduction of new or modified implant designs.

Reference: Pijls, B.G., et al., Early migration of tibial components is associated with late revision: a systematic review and meta-analysis of 21,000 knee arthroplasties. Acta Orthop, 2012. 83(6): p. 614–24.

Purpose: To meet the increasing demand for arthroplasty in Canada healthcare providers are investigating efficiency improvements to maximize utilization of limited surgical resources. One target is routine annual arthroplasty follow-up for which there are no established guidelines. A previous study by the authors revealed that 52% of arthroplasty patients could be followed with standardized questionnaires and x-rays resulting in a 30% savings to the healthcare system. In this study we report the patient time, travel and financial burdens for annual follow-up at a tertiary care centre versus a hypothetical model using standardized assessment at community hospitals and a web-enabled PACS.

Method: A consecutive sample survey of elective THA and TKA patients (n=158; 99 females; 94 THA; 64 TKA; mean age=69 years) who were at least twelve months postoperative. Patient’s address, work status, mode of travel and times required for travel, physician consult, x-ray, and clinic wait were recorded. A web-based mapping application was used to determine distances from patients’ homes to the tertiary care centre and nearest community hospital. Financial burden was calculated using Statistics Canada figures for average Canadian wage and private vehicle travel costs.

Results: Sixteen patients were working at the time of the study and 149 travelled in a private vehicle. For the tertiary care centre: round-trip distance was 168 km, total time burden was 194 minutes (travel=129 minutes, clinic wait=54 minutes, time with physician=6 minutes, x-ray=5 minutes), and total financial burden per patient was $58. For the community hospital: round-trip distance was 19 km, total time burden was 39 minutes (travel=14 minutes, clinic wait=20 minutes, x-ray=5 minutes), and total financial burden was $7.

Conclusion: Utilizing community hospital resources for arthroplasty follow-up could reduce patients’ travel by 89%, financial burden by 88%, and time burden by 81%. This approach has the potential to enable the focusing of arthroplasty clinic follow-up resources only on patients reporting problems or with symptomatic x-rays thus freeing up surgeon time for surgeries. There are also the broader societal implications of reducing ‘health miles’ and the resulting carbon dioxide emissions related to health care delivery by leveraging new technologies to move information rather than people.

Purpose: Porous metal technology may have significant impacts on implant fixation and long-term survival due to their high co-efficient of friction and similarity to trabecular bone in morphology and mechanical behaviour. While promising, the in vivo mechanical behaviour and micromotion at the interface has not previously been reported on. We report on the 2-year results of an RCT using radiosterometric analysis (RSA) to asses a porous metal (PM) monoblock tibial component.

Method: Patients undergoing TKA were randomized to receive a either the PM (n=34) or the cemented tibial component (n=33). A standardized protocol was used for intra and post-operative factors. RSA exams were obtained postoperatively within 4 days of surgery and at 6, 12 and 24 months. One patient was excluded due to an intraoperative complication, and four others were lost to follow-up due to poor bead visibility or morbidity. Standard subjective outcome measures were applied.

Results: There were no revisions in either group. The PM group exhibited two distinct migration patterns. One group stabilized immediately with similar migration to the cemented cases (0.38 vs. 0.46 p=0.4). A subset of 6 PM cases demonstrated significantly higher initial migration (mean=2.01mm, p< 0.01) but appeared stable at 2 years. In addition, 3 of the 6 high migration cases manifested independent bead subsidence. This was determined to be due to PM plate deformation. Two cemented cases were considered at risk for early failure due to aseptic loosening because of RSA migration pattern. There were no differences between groups in the subjective health outcome measures.

Conclusion: A subset of PM components demonstrated high early migration followed by stabilization. It appears that some of these PM components deformed under load, most often in the posteromedial corner, perhaps as a result of malalignment or ligament imbalance. The implications of this finding are yet to be determined.

The purpose of this study was two-fold:

to examine perioperative prospective changes in pain, disability and psychosocial variables in ACL reconstructed recreational athletes over the pre-op to eight week post-op period.

All participants were recreational athletes at the time of their injuries who had patella-autograft procedure at the the Queen Elizabeth II Health Sciences Centre. Fifty-four patients (twenty-nine males; mean age = 25.4 years, SD = 8.08). Mean education was fourteen years (SD = 2.08), 32%(17) were married, 67%(36) single, and 1% was divorced. 94%(51) of the sample was Caucasian, 3%(2) Black, and 1% Asian. One quarter reported their ACL injury was due to sport-based contact, with non-contact sporting activity reported at 76%(41). All participants completed measures of pain, depression, pain catastrophizing, state anxiety pre-op, on days one and two following surgery and again at eight weeks post-op. Disability was assessed pre-op and eight weeks post-op.

Pain was varied across comparisons with preoperative pain increased twenty-four and forty-eight-hour post-op. Pain at forty-eight-hours postoperative was significantly higher than pain reported at eight-weeks post-op. Catastrophizing did not differ from the pre-op to twenty-four-hour post-op but did drop from twenty-four to forty-eight-hours and forty-eight-hours to eight-weeks post-op. Pre-op depression increased twenty-four-hour post-op, but not from twenty-four to forty-eight-hours and declined at eight-weeks. Anxiety increase pre-op to twenty-four-hours but not from twenty-four to forty-eight-hours but did drop from forty-eight-hours to eight-weeks.Disability did not change over time. Regression showed age or gender did not predict disability but forty-eight hour pain and catastrophizing did.

These data indicate that pain and psychological variables change over time of ACL recovery. Results suggest that pain and distress peek during acute post-op period. As well, post-op catastrophizing predicts disability at eight weeks post-op which may indicate that catastrophizing may be related to behaviours related to slower recovery following ACL reconstructive surgery.

The demand for knee arthroplasty (TKR) is increasing yet there are no established criteria for prioritizing patients. We investigated surgeon inter-observer reliability and factors that influenced their prioritization of patients by having three surgeons each independently consult on twelve randomly selected patients waiting for TKR. Surgeons had high reliability and were most influence by the patient’s pain and gait pattern when assigning priority. Surgeon assigned priority also correlated with common subjective outcome metrics. Formalized gait assessment may allow for more objective prioritization of patients waiting for TKR.

The purpose of this study was to investigate the inter-observer reliability of surgeons assessing the priority of patients waiting for elective total knee arthroplasty (TKR) surgery, and to assess the discriminative methodology surgeons employ when assessing patients.

Surgeon’s can reliably assign a priority to their patients waiting for TKR. Surgeons generally consider the patients pain and gait pattern when assigning priority.

Wait lists for elective TKR are increasing and the demand will continue to grow. Objective criteria for prioritizing patients would allow for rational delivery of limited surgical resources.

Surgeons have high inter-observer reliability when assigning patient priority (ICC = 0.86). Pain and gait pattern have a significant impact on the surgeon’s assessment of priority (p=0.25 and p< 0.001, respectively). The oxford twelve most closely correlated to the surgeon’s prioritization (r=0.80).

Twelve patients waiting for TKR were randomly selected from three surgeons wait lists. Each surgeon independently examined all twelve patients and recorded their assessment of the patient’s acuity (priority) on a visual analogue scale. The impact of various aspects of the patient’s presentation on the surgeon’s assessment, such as pain control, function, gait, joint contracture and radiographic appearance, were recorded. All patients completed the SF-36, Oxford twelve and WOMAC questionnaires. Linear regression and Intra-Class Correlation Coefficients were used to assess the data.

Through the complex patient-surgeon interaction during a standard consultation, surgeons are able to prioritize their patient’s with high reliability. Improved objective metrics for prioritizing patient’s may be possible by more formalized methods of gait assessment.

Purpose: The Advance Medial Pivot (MP) knee has higher congruency and postulated different kinematics than traditional posterior stabilized knee implants. This could lead to increased micromotion at the tibial component/bone interface potentially resulting in premature loosening. To investigate the stability of the MP knee we used maximum total point motion (MTPM) as determined with RSA to compare micromotion at the tibial component/bone interface between the Advance MP and PS knees.

Methods: A power calculation determined that a minimum sample size of 40 (20/group) was required. Sixty-six patients (48 females) with primary osteoarthritis of the knee were randomized to receive the Advance MP (n=36) or PS (n=30) knee. Three experienced knee surgeons followed a standardized surgical technique (PCL resection, patella resurfacing, RSA bead placement in polyethylene and tibia) and post-operative protocol (CPM as tolerated, no drains, WBAT). SF-36, WOMAC, PCS, KSCRS were administered to all patients pre-operatively and at 6, 12 and 24 months post-operatively and BMI was recorded. Within 4 days of surgery and at 6, 12 and 24 months post-operatively patients underwent bi-planar x-rays.

Results: Fifteen patients were lost to follow-up (2 infections, 1 death, 2 dropped out, 10 lost due to technical issues). There was no difference in MTPM between groups at 2 years. Physical function was better (p< 0.03) for the PS group at 6 months but there was no difference at 1 year.

Conclusions: There was no difference in MTPM between groups at 2 years post-op. The Advance PS knee appears to result in earlier post-operative improvements in physical function. The altered kinematics and increased congruency of the Advance MP knee does not seem to alter the forces at the tibial component/bone interface and therefore does not appear to be more prone to migration and premature aseptic loosening.

Funding : Other Education Grant

Funding Parties : Unrestricted grant from Wright Medical Inc.

Purpose: To investigate the stability of an uncemented Trabecular Metal (TM) tibial component we used maximum total point motion (MTPM) as determined with RSA to compare micromotion at the tibial component/bone interface between the uncemented Nexgen TM monoblock and cemented Nexgen cobalt chrome modular knee prostheses.

Methods: A power calculation determined that a minimum sample size of 40 (20/group) was required. Sixty-seven patients with primary osteoarthritis of the knee were randomized to receive the Nexgen TM monoblock (n=34; 20 female; mean age=66 years; mean BMI=32) or cobalt chrome modular (n=33; 19 female; mean age=65 years; mean BMI=33) posterior stabilized knees. Four experienced knee surgeons followed a standardized surgical technique (PCL resection, patella resurfacing, RSA bead placement in polyethylene and tibia) and post-operative protocol (CPM as tolerated, no drains, WBAT). SF-36, WOMAC, PCS, KSCRS were administered to all patients pre-operatively and at 6, 12 and 24 months post-operatively and BMI was recorded. Within 4 days of surgery and at 6, 12 and 24 months post-operatively patients underwent bi-planar x-rays.

Results: The TM group had greater initial migration but appeared stabilized at 1 year. There were 2 significant subgroups in the TM group based on migration at 6 months: one group had mean values of 2.1 mm while the other had mean values of 0.4 mm which was comparable to the modular group (0.6 mm). There was no significant migration between 6 and 12 months for both implants indicating good fixation to the proximal tibia. There were no differences between groups in the outcome measures, age and BMI.

Conclusions: There was no difference in MTPM between groups at 1 year post-op and all knees appeared well fixed to the proximal tibia by 6 months postop. The Nexgen TM monoblock tibial component seemed to be prone to greater initial migration but it does not appear to compromise long-term bony in-growth and fixation. Long-term survivorship of the TM tibial component should be the same or better than a cemented cobalt chrome tray.

Funding : Other Education Grant

Funding Parties : Unrestricted grant from Zimmer Inc.