The potential of cells derived from human umbilical cord(UC) for orthopaedic cell engineering is evaluated by dissecting the UC into four distinct anatomical structures – cord lining (CL), Wharton's Jelly (WJ), umbilical cord artery (UCA) and umbilical cord vein (UCV). Cells from individual anatomical layers were grown by explant culture technique for 21 days. Tri-lineage differentiation and growth kinetics of cells from each layer were compared. Flowcytometry was done according to ISCT criteria to ascertain their surface antigen expressions. Cells from all four layers differentiated into bone, cartilage and fat. Osteogenic and chondrogenic differentiation was variable for each type of cells. All cells expressed surface antigens characteristic of mesenchymal stem cells (MSC). These cells can form a potential cell source in cell engineering to produce bone and cartilage although individual cell type needs to be characterised from each anatomical layer of UC and identify the best cell type for cell engineering.

Stem cells are a key component of regenerative medicine strategies. Particular areas of musculoskeletal application include cartilage and bone regeneration in arthritis and trauma. There are several types of stem cell and this article will focus on the adult derived cells. The review includes current issues and future developments.

Purpose

Despite the increasing interest and subsequent published literature on hip resurfacing arthroplasty, little is known about the prevalence of its complications and in particular the less common modes of failure. The aim of this study was to identify the prevalence of failure of hip resurfacing arthroplasty and to analyse the reasons for it.

Introduction: This research aims to study the efficacy and effect of Bone Marrow Stromal Stem Cell (BMSSC) implantation on healing of refractory fracture non-union.

Methods: Approved by the local Ethics Committee, twelve patients (9M and 3F), age range 38 to 76 years (mean 49.9) with non-union resistant to multiple previous attempts of treatment (mean 3.75 procedures) were treated. Four tibial and eight femoral non-union.

The patients were admitted for harvesting of stromal stem cells by bone marrow aspiration from the iliac bone. BMSSC were expanded in tissue cultures for three weeks to an average of 5 x 10⁶ cells. After successful culture the non-union site underwent decortication and BMSSC added to synthetic bone substitute (different types) on one side of the fracture (medial or lateral) according to randomisation. The side of treatment was blinded to patient, surgeons and radiologist.

Standard radiographs were taken and evaluated independently by three experienced musculoskeletal radiologists. The extent of callus formation on each side was recorded. In equivocal cases computerized tomography (CT) was also obtained.

Results: No patient developed systemic complications related to the procedure. On follow-up callus formation was present in 9 of 12 patients. Callus was more marked on the cell implantation side in 6/12 patients (50%), control side in 1/12 (8.3%) and on both sides in 2 patients. 3 patients showed no change.

Discussion: These findings suggest that implantation of BMSSC can enhance bone formation in persistent non-union. A larger randomized controlled trial will follow to test this new treatment.

Proximal femoral fractures have always been in the centre of attention in terms of their demand on the manpower and resources of the NHS. With an ageing population, the number of these fractures will continue to be a big part of the workload of all the Orthopaedic and rehabilitation units. Hence it is important to be aware of any definite variation in the incidence of proximal femoral fractures for appropriate planning of the available resources.

We carried out a study to find out whether there is a definite variation in the incidence of these fractures. The number of operated proximal femoral fractures across 31 hospitals of North-west England and Scotland were collected on a monthly basis from 1994 to 1999. This database of 27, 000 operated proximal femoral fractures was assessed statistically.

Our analysis reveals that the incidence of these fractures during December is about 17% higher than the rest of the annual mean with a 2% standard error of the mean (SEM) and in January this increase is about 22% with an SEM of 1%. These trend and pattern were observed for both intra and extra capsular fractures of neck of femur and was consistent over the five years. There was no other significant change in the incidence pattern during other months of the year.

This study, one of the largest of its kind ever carried out in Britain, proves that there is an increase in the incidence of hip fractures in the months of December and January. There should be appropriate allocation of manpower and rehabilitation facilities along with a matching reduction in the elective Orthopaedic admissions during the months of December and January to tackle this seasonal variation.

Introduction: Existing fatigue studies of ACL fixation have two disadvantages. There is no agreed standard protocol, making comparison of various studies difficult and average results are presented, disregarding data spread. This may be over-optimistic, because approximately half the fixations will not achieve the average level. The effect of data spread can be summarised using the one-sided 80/80 lower tolerance limit (LTL). This LTL indicates the strength that at least 80% of fixations will reach, with an 80% probability. It is commonly used in engineering.

We fatigue-tested a new resorbable composite screw (PLLA/tri-calcium phosphate) and a metal interference screw. We present average data and tolerance limits.

Methods: Porcine BPTB grafts (Ø=9mm) were fixed inside tibial tunnels (Ø=10mm) using composite or metal screws. Each screw was tested for static pull-out strength (n=6) and cyclic loading to failure at 330N and 415N (n=5 each level)

Means and standard deviations of pullout strength were compared. Log-log curves were fitted between force level and cycles to failure. LTLs were calculated.

Results: During static loading, all repairs failed by graft pullout or tissue failure. During cyclic loading, all except one graft fixed with composite screws failed by pullout. Grafts fixed with metal screws failed by bone fracture in 60% of the cases. A composite screw loaded at 300N would last on average 272 cycles or at least (LTL) 7 cycles. At 200N the average and LTL were 38,218 and 966 cycles. Corresponding values for the metal screw were 263 (mean) and 12 (LTL) at 300N; and 12,454 and 564 at 200N.

Discussion and Conclusions: Repairs with metal screw had higher pullout strength, but proved more prone to fatigue. Higher incidence of bone graft fracture in fatigue testing with metal screws suggests that their sharp threads act as stress risers. Fatigue testing of ACL reconstructions shows wide variation, due to several factors. Average levels are therefore over-optimistic and tolerance limits gives a better indication of screw performance. We suggest that tolerance limits should be reported in future studies.