Purpose

Radiostereometric Analysis (RSA) is a well developed imaging technique used to estimate implant fixation of orthopaedic implants in randomized clinical trials. The precision of RSA depends on a number of factors including image quality related to the individual modality properties. This study assesses the precision of RSA with a novel Digital Radiography (DR) system compared to a CR imaging system using different imaging techniques. Additionally, the study assesses the precision of locating beads embedded in a modified spine pedicle screw.

Purpose: Deciding how to allocate scarce surgical resources is a worldwide issue. These decisions can be especially difficult when considering procedures aimed primarily at improving functional quality of life, such as lower extremity joint replacement (LEJR) surgery, and those procedures that can be perceived primarily as life preserving but should also have an impact on physical function, such as coronary artery bypass graft (CABG) surgery. A comparison of the functional outcomes of these two different procedures may provide further evidence to guide resource allocation decisions. The purpose of this study is to compare patient-reported functional outcomes following CABG and LEJR surgery using standardized, validated outcome metrics.

Method: A retrospective review of prospectively collected pre and post-operative health related quality of life (SF-36) measures from patients undergoing elective CABG and elective LEJR surgery in an academic surgical center. The sample included 112 CABG patients who were matched with LEJR patients based on gender and age.

Results: The mean age in the CABG group was 63 years, in the LEJR group 64 years. Seventy eight percent (78%) of the patients were male. Pre-operatively, CABG patients reported statistically higher (p< 0.05) Physical Functioning, less Bodily Pain, and superior Physical Component summary SF-36 scores compared to the LEJR group. However, their pre-operative General Health scores were statistically lower. Surgery resulted in a general improvement in all SF-36 scales and summary scores for all patients, with statistically significant improvements in Bodily Pain and General Health Scores occurring in both groups. Interestingly, the improvement in Bodily Pain score was greater for the LEJR group than the CABG group, whereas the improvement in General Health Score was greater in the CABG group. However the pre-operative pattern of statistically better Physical Functioning, Bodily Pain and Physical Component summary SF-36 scores in the CABG group, and superior General Health scores in the LEJR group remained following surgery.

Conclusion: It appears that, despite being matched for age and gender, significant pre-operative general health differences exist between CABG and LEJR patients that persist post-operatively. While surgery does result in significant improvements for both groups, CABG patients enjoy greater improvement in General Health scores while LEJR patients benefit from greater improvements in Bodily Pain scores. Further research is currently underway to examine how these differences are reflected in disease-specific scores and in health care resource utilization.

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: Implant retrieval analysis provides valuable information to researchers, clinicians and manufactures about the in vivo wear characteristics. Wear analysis can quantify visible damage on retrieved UHMWPE bearing surfaces used in total knee arthroplasty (TKA). Various researchers have developed wear scores to help provide insight into the modes of prosthetic failure. Four scoring methods are compared in order to determine their inter-rater reliability.

Method: A cohort of 60 retrieved G2, Smith & Nephew/Richards, TKA implants were analyzed by two observers using four scoring techniques. The scoring methods used had been developed by Hood, Wasielewski, Currier, and Brandt. The intraclass correlation coefficient (ICC) was used in assessing the inter-rater reliability.

Results: The ICC demonstrated significant correlation between raters (P< 0.05). Hood’s method produced a correlation of 0.89, Wasielewski’s method 0.83, Currier’s method 0.58, and Brandt’s method 0.82. All but Currier’s method had excellent correlation between raters.

Conclusion: The analysis techniques for articular surface wear for total knee bearings by Hood, Brandt, and Wasielewski showed excellent inter rater reliability; however currier’s method was only fair. One common issue among all these methods is that the scoring systems do not identify or assign differentiating weights to clinically relevant wear modalities to capture inferior implants designs. A new wear analysis technique that is efficient and assigns clinical severity weights to wear modes in TKA bearings should be investigated.

Purpose: The accuracy and precision for shoulder radio-stereometric analysis (RSA) is not as well documented as for hip and knee replacement implants. Shoulder replacement glenoid component have a relatively high rate of aseptic loosening when compared to primary hip and knee replacement components. The purpose of this study is to validate our marker based RSA system for a shoulder phantom using computed radiography.

Method: A Sawbones humerus was surgically prepared with a total shoulder implant by an experienced orthopaedic surgeon. A pegged glenoid component (3 pegs) previously marked with 7 tantalum beads was cemented into a Sawbones scapula. The glenoid component was mounted to a 32mm thick acrylic plate. The simulated humerus with implant was fixed to a linear translation stage. The stage was able to move in 0.010 mm increments with an accuracy of 0.002 mm. The Humeral component was then incrementally moved along the x, y, and z axis from 0 to 0.050, 0.100, 0.150, 0.200, 1.000 mm with duplicates taken at each increment. This examination was performed a total of 3 times. From these 9 RSA exams, the accuracy and precision of the UmRSA Digital Measure V6.0 RSA system was determined from 90 pairs of linear displacements.

Results: The standard deviation of the total average error for the X, Y, Z axis were 0.023, 0.022, and 0.070 mm respectively. The accuracy for phantom shoulder model using computer radiography was 0.008 mm in the medial direction, 0.007 mm in the superior direction and 0.019 mm in the anterior direction. The corresponding precision measurements were 0.005, 0.005, 0.015 mm.

Conclusion: This preliminary assessment of accuracy and precision of a shoulder phantom model illustrates that marker based RSA is a useful system to monitor the micro-motion of total shoulder designs.