Cy Frank

Modelling the Behaviour of Ligaments : A technical Note

Experimental observations suggest that during a ligament tensile strain test, water and glycosaminoglycans are exuded. Many attempts have been tried to model this behaviour using continuum mechanics. We have investigated this unique behaviour and have established three mechanisms which may contribute to the experimental observations: the slackness of the fibres before stretching can lead to a decrease in volume upon straightening; a Poissons ratio higher than 0.5 from the axial to the lateral direction (as recorded in the literature [Hewitt, J., Guilak, F., Glisson, R. and Parker Vail, T. (2001) “Regional material properties of the human hip joint capsule ligaments”, Journal of Orthopaedic Research 19(3), 359–364]) due to the very high level of anisotropy of the tissue; and an osmotic pressure, with a certain level of anisotropy, that causes the swelling of the tissue before loading [Thornton, G.M., Shrive, N.G. and Frank, C.B. (2001) “Altering ligament water content affects ligament pre-stress and creep behaviour”, Journal of Orthopaedic Research 19(5), 845–851]. There may be other mechanisms that also contribute in the observed fluid exudation on tensile loading.

Validation of a prediction model to estimate health utilities index Mark 3 utility scores from WOMAC index scores in patients with osteoarthritis of the hip.

OBJECTIVE To examine the validity of a newly developed prediction model translating osteoarthritis (OA)-specific health-related quality of life (HRQL) scores measured using the Western Ontario and McMaster Osteoarthritis Index (WOMAC) into generic utility-based HRQL scores measured using the Health Utilities Index Mark 3 (HUI3). METHODS Preintervention data from 145 patients with hip OA and complete WOMAC and HUI3 baseline assessments from the Alberta Hip Improvement Project study were used to validate three utility prediction models. These models were estimated using data from a previous study of knee OA patients. Predictive performance was assessed using the mean absolute prediction error (MAE) criterion and several other criteria. RESULTS The validation sample appeared healthier (on the basis of the HUI3 and WOMAC) than the subjects used toestimate the prediction models. Nevertheless, the validation sample outperformed the predictive performance of the model sample. The results from the validation sample support the conclusions from the original study in that the primary model identified during model development (a model using WOMAC subscales, their interactions, their square terms, age, OA duration, their square terms, and gender) performed better on the MAE criterion than competing models. CONCLUSION These results support the external validity of the prediction model for the retrospective estimation of HUI3 utility scores for use in economic evaluation.

Evaluating the primary‐to‐specialist referral system for elective hip and knee arthroplasty

RATIONALE, AIMS AND OBJECTIVES Persistently long waiting times for hip and knee total joint arthroplasty (TJA) specialist consultations have been identified as a problem. This study described referral processes and practices, and their impact on the waiting time from referral to consultation for TJA. METHODS A mixed-methods retrospective study incorporating semi-structured interviews, patient chart reviews and observational studies was conducted at three clinic sites in Alberta, Canada. A total of 218 charts were selected for analysis. Standardized definitions were applied to key event dates. Performance measures included waiting times percentage of referrals initially accepted. Voluntary (patient-related) and involuntary (health system-related) waiting times were quantified. RESULTS All three clinics had defined, but differing, referral processing rules. The mean time from referral to consultation ranged from 51 to 139 business days. Choosing a specific surgeon for consultation rather than a next available surgeon lengthened waits by 10-47 business days. Involuntary waiting times accounted for at least 11% of total waiting time. Approximately 40-80% of the time patients with TJA wait for surgery was in the consultation period. Fifty-four per cent of new referrals were initially rejected, prolonging patient waits by 8-46 business days. CONCLUSIONS Our results suggest that variation in referral processing led to increased waiting times for patients. The large proportion of total wait attributable to waiting for a surgical consultation makes failure to measure and evaluate this period a significant omission. Improving referral processes and decreasing variation between clinics would improve patient access to these specialist referrals in Alberta.

Estimating the Burden of Osteoarthritis to Plan for the Future

With aging and obesity trends, the incidence and prevalence of osteoarthritis (OA) is expected to rise in Canada, increasing the demand for health resources. Resource planning to meet this increasing need requires estimates of the anticipated number of OA patients. Using administrative data from Alberta, we estimated OA incidence and prevalence rates and examined their sensitivity to alternative case definitions.

Repetitive activity alters perfusion of proximal interphalangeal joints of the human hand.

ObjectiveTo examine whether competitive volleyball players show any difference in perfusion of their proximal interphalangeal (PIP) joints compared with a healthy group of subjects. Also to assess the viability of a dual wavelength laser Doppler imager (LDI) in making these measurements. SettingPhysiology laboratory. ParticipantsTen active volleyball players who had experienced repetitive finger joint injury and 12 age- and sex-matched normal control subjects. Main Outcome MeasuresUsing a modified LDI incorporating a near- infrared (850 nm) laser as well as a standard red (633 nm) laser, scans were performed over the dorsum of the hands of the volleyball players and the control group. ResultsHigher perfusion values were obtained with the 850-nm laser than with the red 633-nm laser. When referenced to adjacent skin blood flow, perfusion over PIP joints of volleyball players was found to be significantly higher than that in control subjects (p = 0.00012; n = 10–12). ConclusionsThe higher perfusion values obtained using the 850-nm laser suggest that the longer wavelength laser is measuring perfusion in a greater volume of tissue, which could include subcutaneous structures. Volleyball players have significantly higher perfusion over the PIP joints, which is unlikely to be due to differences in skin perfusion over the two regions but is more likely to be related to hyperemia of the underlying PIP joints. The reason for increased PIP perfusion is not clear; it may represent ongoing tissue inflammation due to repeated injury, or it could be an adaptive response to the stresses placed on these joints by this type of repetitive activity. Clinical RelevanceNear-infrared laser Doppler imaging has the potential to provide a noninvasive clinical assessment of finger joint injuries.

Synovial Fluid Stimulates the Proliferation of Rabbit Ligament: Fibroblasts In Vitro

This study was designed to test the hypothesis that synovial fluid may be inhibitory to cell proliferation. The effects of bovine synovial fluid (SF) and hyaluronic acid (HA) on the proliferation of normal rabbit medial collateral ligament (MCL), anterior cruciate ligament (ACL), and MCL scar cells were therefore investigated. Cell lines established from rabbit tissues were plated, incubated, and allowed to attach before treatment with varying concentrations of SF, HA, and a balanced salt solution (BSS). The BSS group was added as a control to observe the effects of media dilution alone on cell proliferation. Cell numbers from each group were quantified at 24, 48, 72, and 96 hours. Results showed that for all cell types, cell proliferation during the log phase of growth was significantly stimulated by SF. Maximum stimulation occurred in 20% SF with stimulation decreasing at higher concentrations of SF. HA had virtually no effect on scar and ACL cells, and only a slight stimulatory effect on MCL cells. Media dilution had no effect on scar cells and began to inhibit cell proliferation of ACL and MCL cells only at high dilutions. These findings suggest that low concentrations of bovine SF stimulate proliferation of rabbit ligament and scar fibroblasts in vitro by a mechanism that appears not to involve HA. Even in high concentrations, SF was not inhibitory to proliferation. The implications of these findings to ligament healing and normal ligament physiology require further investigation.

Patient factors in referral choice for total joint replacement surgery.

Background:Although the option of next available surgeon can be found on surgeon referral forms for total joint replacement surgery, its selection varies across surgical practices. Objectives:Objectives are to assess the determinants of (a) a patient’s request for a particular surgeon; and (b) the actual referral to a specific versus the next available surgeon. Methods:Questionnaires were mailed to 306 consecutive patients referred to orthopedic surgeons. We assessed quality of life (Oxford Hip and Knee scores, Short Form-12, EuroQol 5D, Pain Visual Analogue Scale), referral experience, and the importance of surgeon choice, surgeon reputation, and wait time. We used logistic regression to build models for the 2 objectives. Results:We obtained 176 respondents (response rate, 58%), 60% female, 65% knee patients, mean age of 65 years, with no significant differences between responders versus nonresponders. Forty-three percent requested a particular surgeon. Seventy-one percent were referred to a specific surgeon. Patients who rated surgeon choice as very/extremely important [adjusted odds ratio (OR), 6.54; 95% confidence interval (CI), 2.57–16.64] and with household incomes of

Continuous Quality Improvement Program for Hip and Knee Replacement

90,000+ versus <

Technical Issues in Using Robots to Reproduce Joint Specific Gait

30,000 (OR, 5.74; 95% CI, 1.56–21.03) were more likely to request a particular surgeon. Hip patients (OR, 3.03; 95% CI, 1.18–7.78), better Physical Component Summary-12 (OR, 1.29; 95% CI, 1.02–1.63), and patients who rated surgeon choice as very/extremely important (OR, 3.88; 95% CI, 1.56–9.70) were more likely to be referred to a specific surgeon. Conclusions:Most patients want some choice in the referral decision. Providing sufficient information is important, so that patients are aware of their choices and can make an informed choice. Some patients prefer a particular surgeon despite longer wait times.

Synovial fluid does not inhibit collagen synthesis: Bovine cruciate ligament studied in vitro

Improving quality of care and maximizing efficiency are priorities in hip and knee replacement, where surgical demand and costs increase as the population ages. The authors describe the integrated structure and processes from the Continuous Quality Improvement (CQI) Program for Hip and Knee Replacement Surgical Care and summarize lessons learned from implementation. The Triple Aim framework and 6 dimensions of quality care are overarching constructs of the CQI program. A validated, evidence-based clinical pathway that measures quality across the continuum of care was adopted. Working collaboratively, multidisciplinary experts embedded the CQI program into everyday practices in clinics across Alberta. Currently, 83% of surgeons participate in the CQI program, representing 95% of the total volume of hip and knee surgeries. Biannual reports provide feedback to improve care processes, infrastructure planning, and patient outcomes. CQI programs evaluating health care services inform choices to optimize care and improve efficiencies through continuous knowledge translation.