Stiffness post-total knee replacement: A proof of principle study investigating the effect of gene expression analysis of markers of fibrosis.

BACKGROUND: To establish proof of principle of a link between phenotypic expression and stiffness after TKR. METHODS: From 100 patients, genetic expression of markers of fibrosis was performed for 15 synovial samples from patients categorised as 'best post-operative range of movement (ROM)' and 15 samples from patients with 'worst ROM'. These markers included Matrix Metalloproteinases (MMPs), A Disintegrin and Metalloproteinases with Thrombospondin (ADAMTS) and Tissue Inhibitors of Matrix Metalloproteinases (TIMPs). Genetic marker data were compared to Oxford Knee Scores (OKS) and Pain Catastrophizing Scores (PCS). RESULTS: Quantitative markers for gene expression demonstrated more outliers in stiff compared to non-stiff knees, suggesting a greater imbalance in pro- and anti-fibrotic markers in stiff knees. Whilst there was a significant difference in the range of post-operative knee flexion (p = 0.001) and extension (p = 0.001), there was no statistically significant difference between stiff and non-stiff knees in pre-operative or post-operative OKS (p ≥ 0.06). There was no difference in the individual components of the individual PCS score items nor the PCS total scores when stiff and non-stiff knees were compared (p > 0.05). CONCLUSION: Biological factors, namely gene expression of MMPs, TIMPs and ADAMTS, may contribute towards post-TKR stiffness. This now warrants further investigation to better understand this relationship based on larger, multi-centre, cohorts. LEVEL OF EVIDENCE: Level 3.

The effect of screw taper on interference fit during load to failure at the soft tissue/bone interface.

The effect of screw geometry on the pullout strength of an anterior cruciate ligament reconstruction is well documented. The effect of a truly tapered screw has not been previously investigated. Thirty bovine knees in right and left knee pairs were collected. Superficial digital flexors from the hind legs of sheep were harvested to form a quadruple tendon graft. For each knee pair, one tendon graft was fixed using a tapered screw (n=15) and the other with a non-tapered screw (n=15). Interference screws were manufactured from stainless steel, and apart from the tapered or non-tapered profile were identical. The screws were inserted into a tibial tunnel already containing the tendon graft. The interference fit was tested by extensile load to failure tests. The insertion torque of the screws and first sign of load to failure (by pullout) of the interference fit were recorded. Results were analysed using paired t-tests. The results indicated that tapered screws have significantly higher resistance to interference failure (p=0.007) and insertion torque (p<0.001) than non-tapered screws. The improved biomechanical performance of tapered screws demonstrated in this study may translate into superior clinical results, particularly at the tibial attachment of hamstring anterior cruciate ligament reconstruction, and also of hamstring fixation to the medial femoral condyle for patella instability.

Bed exercises following total hip replacement: 1 year follow-up of a single-blinded randomised controlled trial.

This paper presents the results of a study assessing whether bed exercises after primary THR (total hip replacement) improves function or quality of life, during the first post-operative year. Sixty patients undergoing primary THR were randomised to receive either a gait re-education programme and bed exercises (Group A) or a gait re-education programme without bed exercises (Group B) post-operatively. The Iowa Level of Assistance Scale (ILOA) and Short Form-12 Health Survey (SF-12) were assessed at baseline, 3 days, 6 weeks and 1 year post-operatively. There was no statistically significant difference in either ILOA or SF-12 after 1 year between Group A or B. There was no evidence of a subgroup effect by either the surgical approach or prosthesis fixation in either ILOA or SF-12.