The role of cryopreservation in the biomechanical properties of the intervertebral disc.

Implantation of intervertebral disc (IVD) allograft or tissue engineered disc constructs in the spine has emerged as an alternative to artificial disc replacement for the treatment of severe degenerative disc disease (DDD). Establishment of a bank of cryopreserved IVD allografts enables size matching and facilitates logistics for effective clinical management. However, the biomechanical properties of cryopreserved IVDs have not been previously reported. This study aimed to assess if cryopreservation with different concentrations of cryopreservant agents (CPA) would affect the dynamic viscoelastic properties of the IVD. Whole porcine lumbar IVDs (n = 40) were harvested and processed using various concentrations of CPA, 0 % CPA, 10 % CPA and 20 % CPA. The discs were cryopreserved using a stepwise freezing protocol and stored in liquid nitrogen. After four weeks of storage, the cryopreserved IVDs were quickly thawed at 37 °C for dynamic viscoelastic testing. The apparent modulus, elastic modulus (G'), viscous modulus (G") and loss modulus (G"/G') were calculated and compared to a fresh control group. Cryopreserved IVD without cryopreservants was significantly stiffer than the control. In the dynamic viscoelastic testing, cryopreservation with the use of CPA was able to preserve both G' and G" of an IVD. No significant differences were found between fresh IVD and IVD cryopreserved with 10 % CPA or 20 % CPA. This study demonstrated that CPAs at an optimal concentration could preserve the mechanical properties of the IVD allograft and can provide further credence for the application of long-term storage of IVD allografts for disc transplantation or tissue engineered construct applications.

Measuring performance to drive improvement: development of a clinical indicator set for general medicine.

BACKGROUND: There are delays in implementing evidence about effective therapy into clinical practice. Clinical indicators may support implementation of guideline recommendations. AIM: To develop and evaluate the short-term impact of a clinical indicator set for general medicine. METHODS: A set of clinical process indicators was developed using a structured process. The indicator set was implemented between January 2006 and December 2006, using strategies based on evidence about effectiveness and local contextual factors. Evaluation included a structured survey of general medical staff to assess awareness and attitudes towards the programme and qualitative assessment of barriers to implementation. Impact on documentation of adherence to clinical indicators was assessed by auditing a random sample of medical records before (2003-2005) and after (2006) implementation. RESULTS: Clinical indicators were developed for the following areas: venous thromboembolism, cognition, chronic heart failure, chronic obstructive pulmonary disease, diabetes, low trauma fracture, patient written care plans. The programme was well supported and incurred little burden to staff. Implementation occurred largely as planned; however, documentation of adherence to clinical indicators was variable. There was a generally positive trend over time, but for most indicators this was independent of the implementation process and may have been influenced by other system improvement activities. Failure to demonstrate a significant impact during the pilot phase is likely to have been influenced by administrative factors, especially lack of an integrative data documentation and collection process. CONCLUSION: Successful implementation in phase two is likely to depend upon an effective data collection system integrated into usual care.