The biological significance of cobalt-chromium wear particles from metal-on-metal hip replacements may be different to the effects of the constituent metal ions in solution. Bacteria may be able to discriminate between particulate and ionic forms of these metals because of a transmembrane nickel/cobalt-permease. It is not known whether wear particles are bacteriocidal.

We compared the doubling time of coagulase negative staphylococcus, Staphylococcus aureus and methicillin resistant S. aureus when cultured in either wear particles from a metal-on-metal hip simulator, wear particles from a metal-on-polyethylene hip simulator, metal ions in solution or a control.

Doubling time halved in metal-on-metal (p = 0.003) and metal-on-polyethylene (p = 0.131) particulate debris compared with the control.

Bacterial nickel/cobalt-transporters allow metal ions but not wear particles to cross bacterial membranes. This may be useful for testing the biological characteristics of different wear debris. This experiment also shows that metal-on-metal hip wear debris is not bacteriocidal.

The October 2012 Foot & Ankle Roundup³⁶⁰ looks at: ankle arthrodesis in young active patients; the Bologna-Oxford total ankle replacements; significant failure and revision rates for total ankle arthroplasty; surgical treatment of Achilles tendon rupture; selective plantar fascia release; whether removal of metalwork can resolve foot pain; allografting of osteochondral lesions; distracting from osteoarthritis; and ultrasound-guided minimally invasive surgery.

We live in troubled times. Increased opposition reliance on explosive devices, the widespread use of individual and vehicular body armour, and the improved survival of combat casualties have created many complex musculoskeletal injuries in the wars in Iraq and Afghanistan. Explosive mechanisms of injury account for 75% of all musculoskeletal combat casualties. Throughout all the echelons of care medical staff practice consistent treatment strategies of damage control orthopaedics including tourniquets, antibiotics, external fixation, selective amputations and vacuum-assisted closure. Complications, particularly infection and heterotopic ossification, remain frequent, and re-operations are common. Meanwhile, non-combat musculoskeletal casualties are three times more frequent than those derived from combat and account for nearly 50% of all musculoskeletal casualties requiring evacuation from the combat zone.

Objectives

This study aimed to investigate time-dependent gene expression of injured human anterior cruciate ligament (ACL), and to evaluate the histological changes of the ACL remnant in terms of cellular characterisation.

Between 1996 and 2003, 16 patients (nine female, seven male) were treated for a primary bone sarcoma of the femur by wide local excision of the tumour, extracorporeal irradiation and re-implantation. An additional vascularised fibular graft was used in 13 patients (81%). All patients were free from disease when reviewed at a minimum of two years postoperatively (mean 49.7 months (24 to 96).

There were no cases of infection. Primary union was achieved after a median of nine months (interquartile range 7 to 11). Five host-donor junctions (16%) united only after a second procedure. Primary union recurred faster at metaphyseal junctions (94% (15) at a median of 7.5 months (interquartile range 4 to 12)) than at diaphyseal junctions (75% (12) at a median of 11.1 months (interquartile range 5 to 18)).

Post-operatively, the median Musculoskeletal Tumour Society score was 85% (interquartile range 75 to 96) and the median Toronto Extremity Salvage score 94% (interquartile range 82 to 99). The Mankin score gave a good or excellent result in 14 patients (88%).

The range of movement of the knee was significantly worse when the extracorporeally irradiated autografts were fixed by plates rather than by nails (p = 0.035).

A total of 16 (62%) of the junctions of the vascularised fibular grafts underwent hypertrophy, indicating union and loading.

Extracorporeal irradiation autografting with supplementary vascularised fibular grafting is a promising biological alternative for intercalary reconstruction after wide resection of malignant bone tumours of the femur.

The April 2012 Research Roundup³⁶⁰ looks at who is capable of being an arthroscopist, bupivacaine, triamcinolone and chondrotoxicity, reducing scarring in injured skeletal muscle, horny Goat Weed and the repair of osseous defects, platelet-derived growth factor and fracture healing, the importance of the reserve zone in a child’s growth plate, coping with advanced arthritis, hydroxyapatite and platelet-rich plasma for bone defects, and calcium phosphate and bone regeneration

An experimental sheep model was used for impaction allografting of 12 hemiarthroplasty femoral components placed into two equal-sized groups. In group 1, a 50:50 mixture of ApaPore hydroxyapatite bone-graft substitute and allograft was used. In group 2, ApaPore and allograft were mixed in a 90:10 ratio. Both groups were killed at six months. Ground reaction force results demonstrated no significant differences (p > 0.05) between the two groups at 8, 16 and 24 weeks post-operatively, and all animals remained active. The mean bone turnover rates were significantly greater in group 1, at 0.00206 mm/day, compared to group 2 at 0.0013 mm/day (p < 0.05). The results for the area of new bone formation demonstrated no significant differences (p > 0.05) between the two groups. No significant differences were found between the two groups in thickness of the cement mantle (p > 0.05) and percentage ApaPore-bone contact (p > 0.05).

The results of this animal study demonstrated that a mixture of ApaPore allograft in a 90:10 ratio was comparable to using a 50:50 mixture.

The use of autograft bone is the best option when undertaking a procedure that requires bone graft because it is osteogenic, osteoconductive and osseo-inductive. Pain, morbidity and complications associated with harvesting iliac or non-iliac sites occur in between 6% and 30% of cases. An alternative source of graft with possibly a lower morbidity is the intramedullary canal. In this study, 28 patients undergoing 30 arthrodesis procedures on the hindfoot had a mean of 48 cm³ (43 to 50) of bone harvested locally from the hindfoot or the tibial shaft by antegrade or retrograde reaming. No patient sustained a fracture of the calcaneum, talus or tibia. There was no morbidity except for one complication when the reamer breached the medial tibial cortex. This healed uneventfully.

This method of using the reamer–irrigator–aspirator system is an extension of the standard technique of intramedullary reaming of the lower limb: it produces good-quality bone graft with viable growth factors consistent with that of the iliac crest, and donor site morbidity is low. This is an efficient method of obtaining autologous bone for use in arthrodesis of the ankle or hindfoot.

We examined the mechanical properties of Vicryl (polyglactin 910) mesh in vitro and assessed its use in vivo as a novel biomaterial to attach tendon to a hydroxyapatite-coated metal implant, the interface of which was augmented with autogenous bone and marrow graft. This was compared with tendon re-attachment using a compressive clamp device in an identical animal model. Two- and four-ply sleeves of Vicryl mesh tested to failure under tension reached 5.13% and 28.35% of the normal ovine patellar tendon, respectively. Four-ply sleeves supported gait in an ovine model with 67.05% weight-bearing through the operated limb at 12 weeks, without evidence of mechanical failure.

Mesh fibres were visible at six weeks but had been completely resorbed by 12 weeks, with no evidence of chronic inflammation. The tendon-implant neoenthesis was predominantly an indirect type, with tendon attached to the bone-hydroxyapatite surface by perforating collagen fibres.

We examined whether enamel matrix derivative (EMD) could improve healing of the tendon–bone interface following reconstruction of the anterior cruciate ligament (ACL) using a hamstring tendon in a rat model. ACL reconstruction was performed in both knees of 30 Sprague-Dawley rats using the flexor digitorum tendon. The effect of commercially available EMD (EMDOGAIN), a preparation of matrix proteins from developing porcine teeth, was evaluated. In the left knee joint the space around the tendon–bone interface was filled with 40 µl of EMD mixed with propylene glycol alginate (PGA). In the right knee joint PGA alone was used. The ligament reconstructions were evaluated histologically and biomechanically at four, eight and 12 weeks (n = 5 at each time point). At eight weeks, EMD had induced a significant increase in collagen fibres connecting to bone at the tendon–bone interface (p = 0.047), whereas the control group had few fibres and the tendon–bone interface was composed of cellular and vascular fibrous tissues. At both eight and 12 weeks, the mean load to failure in the treated specimens was higher than in the controls (p = 0.009). EMD improved histological tendon–bone healing at eight weeks and biomechanical healing at both eight and 12 weeks. EMD might therefore have a human application to enhance tendon–bone repair in ACL reconstruction.

Objectives

The need for bone tissue supplementation exists in a wide range of clinical conditions involving surgical reconstruction in limbs, the spine and skull. The bone supplementation materials currently used include autografts, allografts and inorganic matrix components; but these pose potentially serious side-effects. In particular the availability of the autografts is usually limited and their harvesting causes surgical morbidity. Therefore for the purpose of supplementation of autologous bone graft, we have developed a method for autologous extracorporeal bone generation.

Objectives

Surgical marking during tendon surgery is often used for technical and teaching purposes. This study investigates the effect of a gentian violet ink marker pen, a common surgical marker, on the viability of the tissue and cells of tendon.

The success of long-term transcutaneous implants depends on dermal attachment to prevent downgrowth of the epithelium and infection. Hydroxyapatite (HA) coatings and fibronectin (Fn) have independently been shown to regulate fibroblast activity and improve attachment. In an attempt to enhance this phenomenon we adsorbed Fn onto HA-coated substrates. Our study was designed to test the hypothesis that adsorption of Fn onto HA produces a surface that will increase the attachment of dermal fibroblasts better than HA alone or titanium alloy controls.

Iodinated Fn was used to investigate the durability of the protein coating and a bioassay using human dermal fibroblasts was performed to assess the effects of the coating on cell attachment. Cell attachment data were compared with those for HA alone and titanium alloy controls at one, four and 24 hours. Protein attachment peaked within one hour of incubation and the maximum binding efficiency was achieved with an initial droplet of 1000 ng. We showed that after 24 hours one-fifth of the initial Fn coating remained on the substrates, and this resulted in a significant, three-, four-, and sevenfold increase in dermal fibroblast attachment strength compared to uncoated controls at one, four and 24 hours, respectively.

When transferring tissue regenerative strategies involving skeletal stem cells to human application, consideration needs to be given to factors that may affect the function of the cells that are transferred. Local anaesthetics are frequently used during surgical procedures, either administered directly into the operative site or infiltrated subcutaneously around the wound. The aim of this study was to investigate the effects of commonly used local anaesthetics on the morphology, function and survival of human adult skeletal stem cells.

Cells from three patients who were undergoing elective hip replacement were harvested and incubated for two hours with 1% lidocaine, 0.5% levobupivacaine or 0.5% bupivacaine hydrochloride solutions. Viability was quantified using WST-1 and DNA assays. Viability and morphology were further characterised using CellTracker Green/Ethidium Homodimer-1 immunocytochemistry and function was assessed by an alkaline phosphatase assay. An additional group was cultured for a further seven days to allow potential recovery of the cells after removal of the local anaesthetic.

A statistically significant and dose dependent reduction in cell viability and number was observed in the cell cultures exposed to all three local anaesthetics at concentrations of 25% and 50%, and this was maintained even following culture for a further seven days.

This study indicates that certain local anaesthetic agents in widespread clinical use are deleterious to skeletal progenitor cells when studied in vitro; this might have relevance in clinical applications.

Osteoarthritis (OA) is an important cause of pain, disability and economic loss in humans, and is similarly important in the horse. Recent knowledge on post-traumatic OA has suggested opportunities for early intervention, but it is difficult to identify the appropriate time of these interventions. The horse provides two useful mechanisms to answer these questions: 1) extensive experience with clinical OA in horses; and 2) use of a consistently predictable model of OA that can help study early pathobiological events, define targets for therapeutic intervention and then test these putative therapies. This paper summarises the syndromes of clinical OA in horses including pathogenesis, diagnosis and treatment, and details controlled studies of various treatment options using an equine model of clinical OA.

For the treatment of ununited fractures, we developed a system of delivering magnetic labelled mesenchymal stromal cells (MSCs) using an extracorporeal magnetic device. In this study, we transplanted ferucarbotran-labelled and luciferase-positive bone marrow-derived MSCs into a non-healing femoral fracture rat model in the presence of a magnetic field. The biological fate of the transplanted MSCs was observed using luciferase-based bioluminescence imaging and we found that the number of MSC derived photons increased from day one to day three and thereafter decreased over time. The magnetic cell delivery system induced the accumulation of photons at the fracture site, while also retaining higher photon intensity from day three to week four. Furthermore, radiological and histological findings suggested improved callus formation and endochondral ossification. We therefore believe that this delivery system may be a promising option for bone regeneration.

We attempted to characterise the biological quality and regenerative potential of chondrocytes in osteochondritis dissecans (OCD). Dissected fragments from ten patients with OCD of the knee (mean age 27.8 years (16 to 49)) were harvested at arthroscopy. A sample of cartilage from the intercondylar notch was taken from the same joint and from the notch of ten patients with a traumatic cartilage defect (mean age 31.6 years (19 to 52)). Chondrocytes were extracted and subsequently cultured. Collagen types 1, 2, and 10 mRNA were quantified by polymerase chain reaction. Compared with the notch chondrocytes, cells from the dissecate expressed similar levels of collagen types 1 and 2 mRNA. The level of collagen type 10 message was 50 times lower after cell culture, indicating a loss of hypertrophic cells or genes. The high viability, retained capacity to differentiate and metabolic activity of the extracted cells suggests preservation of the intrinsic repair capability of these dissecates. Molecular analysis indicated a phenotypic modulation of the expanded dissecate chondrocytes towards a normal phenotype. Our findings suggest that cartilage taken from the dissecate can be reasonably used as a cell source for chondrocyte implantation procedures.

Free vascularised fibular grafting has been reported to be successful for adult patients with osteonecrosis of the femoral head (ONFH). However, its benefit in teenage patients with post-traumatic ONFH has not been determined. We evaluated the effectiveness of free vascularised fibular grafting in the treatment of this condition in children and adolescents. We retrospectively analysed 28 hips in 28 patients in whom an osteonecrotic femoral head had been treated with free vascularised fibular grafting between 2002 and 2008. Their mean age was 16.3 years (13 to 19). The stage of the disease at time of surgery, and results of treatment including pre- and post-operative Harris hip scores, were studied. We defined clinical failure as conversion to total hip replacement. All patients were followed up for a mean of four years (2 to 7). The mean Harris hip score improved from 60.4 (37 to 84) pre-operatively to 94.2 (87 to 100) at final follow-up. At the latest follow-up we found improved or unchanged radiographs in all four initially stage II hips and in 23 of 24 stage III or IV hips. Only one hip (stage V) deteriorated. No patient underwent total hip replacement.

Free vascularised fibular grafting is indicated for the treatment of post-traumatic ONFH in teenage patients.

The best method of reconstruction after resection of malignant tumours of the tibial diaphysis is unknown. In the absence of any long-term studies analysing the results of intercalary endoprosthetic replacement, we present a retrospective review of 18 patients who underwent limb salvage using a tibial diaphyseal endoprosthetic replacement following excision of a malignant bone tumour. There were ten men and eight women with a mean age of 42.5 years (16 to 76). Mean follow-up was 58.5 months (20 to 141) for all patients and 69.3 months (20 to 141) for the 12 patients still alive. Cumulative patient survival was 59% (95% confidence interval (CI) 32 to 84) at five years. Implant survival was 63% (95% CI 35 to 90) at ten years. Four patients required revision to a proximal tibial replacement at a mean follow-up of 29 months (10 to 54). Complications included metastases in five patients, aseptic loosening in four, peri-prosthetic fracture in two, infection in one and local recurrence in one. The mean Musculoskeletal Tumor Society score and the mean Toronto Extremity Salvage Score were 23 (17 to 28) and 74% (53 to 91), respectively.

Although rates of complication and revision were high, custom-made tibial diaphyseal replacement following resection of malignant bone tumours enables early return to function and provides an attractive alternative to other surgical options, without apparent compromise of patient survival.

The aim of this study was to evaluate the cultivation potential of cartilage taken from the debrided edge of a chronic lesion of the articular surface. A total of 14 patients underwent arthroscopy of the knee for a chronic lesion on the femoral condyles or trochlea. In addition to the routine cartilage biopsy, a second biopsy of cartilage was taken from the edge of the lesion. The cells isolated from both sources underwent parallel cultivation as monolayer and three-dimensional (3D) alginate culture. The cell yield, viability, capacity for proliferation, morphology and the expressions of typical cartilage genes (collagen I, COL1; collagen II, COL2; aggrecan, AGR; and versican, VER) were assessed. The cartilage differentiation indices (COL2/COL1, AGR/VER) were calculated. The control biopsies revealed a higher mean cell yield (1346 cells/mg vs 341 cells/mg), but similar cell proliferation, viability and morphology compared with the cells from the edge of the lesion. The cartilage differentiation indices were superior in control cells: COL2/COL1 (threefold in biopsies (non-significant)); sixfold in monolayer cultures (p = 0.012), and 7.5-fold in hydrogels (non-significant), AGR/VER (sevenfold in biopsies (p = 0.04), threefold (p = 0.003) in primary cultures and 3.5-fold in hydrogels (non-significant)).

Our results suggest that the cultivation of chondrocytes solely from the edges of the lesion cannot be recommended for use in autologous chondrocyte implantation.