Objectives

Bone void fillers are increasingly being used for dead space management in arthroplasty revision surgery. The aim of this study was to investigate the influence of calcium sulphate bone void filler (CS-BVF) on the damage and wear of total knee arthroplasty using experimental wear simulation.

Use of scaffolds for articular cartilage repair (ACR) has increased over the last years with many biomaterials options suggested for this purpose. It is known that scaffolds for ACR have to be optimally biodegradable with simultaneous promotion of chondrogenesis, favouring hyaline cartilage formation under rather complex biomechanical and physiological conditions. Whereas improvement of the scaffolds by their conditioning with stem cells or adult chondrocytes can be employed in bioreactors, “ideal” scaffolds should be capable of performing such functions directly after implantation. It was previously considered that scaffold structure and composition would be the best if it mimics the structure of native cartilage. However, in this case no clear reparative stimuli are being imposed on the scaffold area, which would drive chondrocytes activity in a desired way. In this work, we studied new xeno-free, recombinant human type III collagen-laden polylactide (PLA) mesh scaffolds, which have been designed, produced, and biomechanically optimized in vitro and in vivo validated in a porcine and equine model. The scaffolds were additionally assessed for relative performance simulated synovial fluids for both human conditions and veterinary cases. It was experimentally shown that success of the scaffolds in ACR eventually require lower stiffness than surrounding cartilage yet matching the strain compliance, different in static and dynamic conditions. This ensures an optimal combination of load transfer and oscillatory nutrients supply to the cells, which otherwise is difficult to rely on just with a passive diffusion in avascular cartilage conditions. The results encourage further development of such scaffold structures targeted on their best clinical performance rather than trying to imitate the respective original tissue. The authors would like to thank Finnish Agency for Innovation (Tekes) for providing financial support to this project. A.Z. also acknowledges Teknos Foundation (Finland) for the scholarship

Aims

The success of anterior cruciate ligament reconstruction (ACLR) depends on osseointegration at the graft-tunnel interface and intra-articular ligamentization. Our aim was to conduct a systematic review of clinical and preclinical studies that evaluated biological augmentation of graft healing in ACLR.

The June 2013 Foot & Ankle Roundup³⁶⁰ looks at: soft-tissue pain following arthroplasty; pigmented villonodular synovitis of the foot and ankle; ankles, allograft and arthritis; open calcaneal fracture; osteochondral lesions in the longer term; severe infections in diabetic feet; absorbable first ray fixation; and showering after foot surgery.

The treatment of acute full thickness chondral damage within the knee is a surgical challenge. Frequently used surgical techniques include chondroplasty, micro-fracture and chondrocyte implantation. These procedures give unpredictable functional outcomes and if the formation of neocartilage is achieved it is predominantly composed of type 1 collagen. The TruFit osteochondral plug was designed to provide a scaffold for cell proliferation into full thickness chondral defects. It is a composite polymer composed of polylactide co-glycolide, calcium sulphate and poly-glycolide fibres. It is composed of 2 layers, one with a similar trabecular network to cancellous bone and a superficial layer designed to simulate articular lining. The TruFit bone plug was analysed using micro-computed tomography. Its morphology characteristics, granulometry, mechanical performance and image guided failure were tested as well as numerical modelling to assess the permeability of TruFit. Morphological parameters of the TruFit bone plug compared favourably with those of human tissue. Under load the scaffold exhibited shear bands throughout the composite leading to a failure mechanism similar to cancellous bone. Stress relaxation rates of the scaffolds were greatly decreased under wet conditions, likely due to plasticisation of the scaffold by water. The biomechanical properties of the TruFit bone plugs are a cause for concern. The Scaffolds mechanical performance under load rapidly deteriorates in wet conditions at body temperature (the natural knee environment). This early failure will lead to defects in the articular surface where the plug has been inserted. Clinical data is sparse. This study correlates with work performed by Dockery et al & Spalding et al. These clinical studies have shown that the TruFit implant shows no evidence of bone ingrowth or osteoconductivity. It provides no subchondral support to neocartilage or tissue that was stimulated to form around the defects and surgical sites

Objectives

Osteochondral injuries, if not treated adequately, often lead to severe osteoarthritis. Possible treatment options include refixation of the fragment or replacement therapies such as Pridie drilling, microfracture or osteochondral grafts, all of which have certain disadvantages. Only refixation of the fragment can produce a smooth and resilient joint surface. The aim of this study was the evaluation of an ultrasound-activated bioresorbable pin for the refixation of osteochondral fragments under physiological conditions.

Massive segmental bone defects in long bones remain a considerable clinical challenge and are a source for significant morbidity and prolonged dysfunction for the patient. We demonstrate the successful use of resorbable polylactide membranes as a scaffold for autologous bone graft in the treatment of a 10cm traumatic femoral bone defect. A 28-year-old male was involved in a motorcycle accident vs. tree at 140k/hr. He sustained a Gustillo grade 3b intercondylar fracture of his right femur, and a 10cm piece of his femoral bone found at the scene was brought to Emergency in a sterile container. He was taken to theatre for debridement and ORIF of the intercondylar fracture, with vacuum dressing cover. Day 5 post injury the patient returned to theatre and the LISS plate was revised to correct the rotation and 3cm shortening. The 10cm cortical defect now present was filled with antibiotic cement (Palacos) and delayed primary closure was performed. Day 21 post injury the cement spacer was removed and replaced with two polylactide membrane tubes, one within the medullary canal and the other around the outside of the bone. The “neocortical” space thus produced was grafted with cancellous autograft mixed with bone morphogenic protein (OP1, Stryker). The remainder of the post-operative course was uncomplicated and the patient was discharged home 5 days later. The patient was reviewed at the 6 week and 3 month mark post injury. The femoral defect demonstrated both radiological and clinical union at the 3 month mark and full weight bearing was permitted. His range of motion at that stage was 5 to 95 degrees with no sign of infection. The use of polylactide membranes as a scaffold in the treatment of segmental long bone defects is an excellent and relatively straightforward technique. Forming a space between the 2 tubes controls cancellous graft to the site of the cortical area where it is required and the polylactide membrane then resorbs over years producing CO2 and water. This case demonstrates that the use of polylactide membranes is safe and effective in the management of segmental long bone defects

Introduction: Platelet rich plasma (PRP) has been hypothesised to be of potential benefit to articular cartilage tissue engineering, through its release of autologous growth factors. The aim of this study was to ascertain whether the addition of thrombin is required to achieve platelet activation and sustained growth factor release in-vitro, when PRP is applied to a collagen based osteochondral scaffold. Methods: Collagen/glycosaminoglycan scaffolds were fashioned, to which equal combined volumes of test substances were added (n=3): 500μl PRP; 375μl PRP + 125μl autologous thrombin (3:1); 455μl PRP + 45μl bovine thrombin (10:1). One ml of DMEM/F12 medium was added to each scaffold and changed completely at 12/24 hours, and 3/10 days, following which release of TGF-β1, PDGF-AB and bFGF were measured using ELISA. Secondly, equal sized collagen/glycosaminoglycan and polylactide co-glycolide scaffolds were fashioned to which 500μl of PRP were added (n=3). Similar conditions were followed as previously except that only PDGF-AB was assayed. Results: A similar cumulative release profile of all growth factors was found over the 10 day period. An increase in growth factor release was seen in the PRP only group at all time points with PDGF-AB in particular reaching statistical significance at all time points (p< 0.006). These findings remained apparent when a correction for volume was made (p< 0.028) suggesting a particular role of the collagen in platelet activation. This was shown in the second experiment, in which a significantly increased cumulative volume of PDGF-AB was released from the collagen/glycosaminoglycan scaffold without thrombin activation (p< 0.04). Discussion: This study shows that collagen is a potent activator of platelets, requiring no further addition to achieve satisfactory growth factor release when applied clinically. These results suggest that if PRP is combined with polymer scaffolds, it should be activated with thrombin to achieve optimum growth factor release

We studied the effects of hyperbaric oxygen (HBO) and zoledronic acid (ZA) on posterior lumbar fusion using a validated animal model. A total of 40 New Zealand white rabbits underwent posterior lumbar fusion at L5–6 with autogenous iliac bone grafting. They were divided randomly into four groups as follows: group 1, control; group 2, HBO (2.4 atm for two hours daily); group 3, local ZA (20 μg of ZA mixed with bone graft); and group 4, combined HBO and local ZA. All the animals were killed six weeks after surgery and the fusion segments were subjected to radiological analysis, manual palpation, biomechanical testing and histological examination.

Five rabbits died within two weeks of operation. Thus, 35 rabbits (eight in group 1 and nine in groups 2, 3 and 4) completed the study. The rates of fusion in groups 3 and 4 (p = 0.015) were higher than in group 1 (p < 0.001) in terms of radiological analysis and in group 4 was higher than in group 1 with regard to manual palpation (p = 0.015). We found a statistically significant difference in the biomechanical analysis between groups 1 and 4 (p = 0.024). Histological examination also showed a statistically significant difference between groups 1 and 4 (p = 0.036).

Our results suggest that local ZA combined with HBO may improve the success rate in posterior lumbar spinal fusion.

Bacterial infection in orthopaedic surgery can be devastating, and is associated with significant morbidity and poor functional outcomes, which may be improved if high concentrations of antibiotics can be delivered locally over a prolonged period of time. The two most widely used methods of doing this involve antibiotic-loaded polymethylmethacrylate or collagen fleece. The former is not biodegradable and is a surface upon which secondary bacterial infection may occur. Consequently, it has to be removed once treatment has finished. The latter has been used successfully as an adjunct to systemic antibiotics, but cannot effect a sustained release that would allow it to be used on its own, thereby avoiding systemic toxicity.

This review explores the newer biodegradable carrier systems which are currently in the experimental phase of development and which may prove to be more effective in the treatment of osteomyelitis.

Introduction: Platelet rich plasma (PRP) has been hypothesised to be of potential benefit to articular cartilage tissue engineering, through its release of autologous growth factors. The aim of this study was to ascertain whether the addition of thrombin is required to achieve platelet activation and sustained growth factor release in-vitro, when PRP is applied to a collagen based osteochondral scaffold. Methods: Collagen/glycosaminoglycan scaffolds were fashioned, to which equal combined volumes of test substances were added (n=3): 500μl PRP; 375μl PRP + 125μl autologous thrombin (3:1); 455μl PRP + 45μl bovine thrombin (10:1). One ml of DMEM/F12 medium was added to each scaffold and changed completely at 12/24 hours, and 3/10 days, following which release of TGF-β1, PDGF-AB and bFGF were measured using ELISA. Secondly, equal sized collagen/glycosaminogly-can and polylactide co-glycolide scaffolds were fashioned to which 500μl of PRP were added (n=3). Similar conditions were followed as previously except that only PDGF-AB was assayed. Results: A similar cumulative release profile of all growth factors was found over the 10 day period. An increase in growth factor release was seen in the PRP only group at all time points with PDGF-AB in particular reaching statistical significance at all time points (p< 0.006). These findings remained apparent when a correction for volume was made (p< 0.028) suggesting a particular role of the collagen in platelet activation. This was shown in the second experiment, in which a significantly increased cumulative volume of PDGF-AB was released from the collagen/glycosaminoglycan scaffold without thrombin activation (p< 0.04). Discussion: This study shows that collagen is a potent activator of platelets, requiring no further additive to achieve satisfactory growth factor release when applied clinically. These results suggest that if PRP is combined with polymer scaffolds, it should be activated with thrombin to achieve optimum growth factor release

Introduction: Platelet rich plasma (PRP) has been hypothesised to be of potential benefit to articular cartilage tissue engineering, through its release of autologous growth factors. The aim of this study was to ascertain whether the addition of thrombin is required to achieve platelet activation and sustained growth factor release in-vitro, when PRP is applied to a collagen based osteochondral scaffold. Methods: Collagen/glycosaminoglycan scaffolds were fashioned, to which equal combined volumes of test substances were added (n=3): 500μl PRP; 375μl PRP + 125μl autologous thrombin (3:1); 455μl PRP + 45μl bovine thrombin (10:1). One ml of DMEM/F12 medium was added to each scaffold and changed completely at 12/24 hours, and 3/10 days, following which release of TGF-β1, PDGF-AB and bFGF were measured using ELISA. Secondly, equal sized collagen/glycosaminogly-can and polylactide co-glycolide scaffolds were fashioned to which 500μl of PRP were added (n=3). Similar conditions were followed as previously except that only PDGF-AB was assayed. Results: A similar cumulative release profile of all growth factors was found over the 10 day period. Greater growth factor release was seen in the PRP only group at all time points with PDGF-AB in particular reaching statistical significance at all time points (p< 0.006). These findings remained apparent when a correction for volume was made (p< 0.028) suggesting a particular role of the collagen in platelet activation. This was shown in the second experiment, in which a significantly increased cumulative volume of PDGF-AB was released from the collagen/glycosaminoglycan scaffold without thrombin activation (p< 0.04). Discussion: This study shows that collagen is a potent activator of platelets, requiring no further addition to achieve satisfactory growth factor release when applied clinically. These results suggest that if PRP is combined with polylactide co-glycolide scaffolds, it should be activated with thrombin to achieve optimum growth factor release

Introduction: Biodegradable systems releasing antibiotics are promising candidates for the management of chronic osteomyelitis. Gentamicin and fluoroquinolones are the commonest antibiotics applied with these systems. The effectiveness of a new system from polymerized dilactide (PLA) with incorporated linezolid has been investigated in a rabbit model for treating osteomyelitis by methicillin-resistant Staphylococcus Aureus (MRSA).

Methods: The PLA – Linezolid system was made after thorough stirring 2gr of polymer with 100 mg of linezolid. Experimental osteomyelitis was established in 40 rabbits by a modification of the Norden model. Methicillin-resistant Staphylococcus aureus (MRSA) was applied as the test isolate. After drilling a hole in the upper right femur, the isolate was inoculated along with a thin needle working as a foreign body. After three weeks the needle was removed and cultured and PLA-Linezolid system was implanted in half of the animals. Animals were sacrificed at regular time intervals and tissue around the site of implantation was sent for histologic examination and quantitative cultures.

Results: At 2 – 4 – 6 – 8 – 10 weeks time after removal of the needle results (mean values) were as follows (Controls/PLA-Linezolid): Log10 (cfu/g) at infection site: 2.99/5.68 – 3.44/3.20 – 3.22/2.39 – 1.00/1.27 – 1.00/1.00 respectively and Δlog10 (cfu/g) compared to start: −0.05/−3.23 – 0.23/0.13 – 0.05/0.93 – 1.34/1.09 – 3.31/3.34 respectively. Histology confirmed the previous mentioned results, showing an early decrease following by late recurrence of the infectious reaction at the animals that PLA-Linezolid system was used.

Conclusions: It is concluded that the applied system achieved an early decrease of the tissue bacterial load which was not maintained until late on follow-up. This might be explained by the bacteriostatic mode of action of linezolid.

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.

A total of 11 patients (12 knees) with stable lesions of osteochondritis dissecans of the knee underwent arthroscopic fixation of the fragments using polylactide bioabsorbable pins. The site of the lesion was the medial femoral condyle in ten knees and the lateral femoral condyle in two. The mean age of the patients was 14.8 years (12 to 16). At a mean follow-up of 32.4 months (13 to 38 months) all fragments had MRI evidence of union. One patient developed early transient synovitis, which resolved with non-steroidal anti-inflammatory medication. All patients returned to sporting activities within eight months of operation and did not require a period of immobilisation

Despite worldwide clinical use of bio-absorbable devices for internal fixation in orthopaedic surgery, the degradation behaviour and tissue replacement of these implants are not fully understood.

In a long-term experimental study, we have determined the patterns of tissue restoration 36 and 54 months after implantation of polyglycolic acid and poly-laevo-lactic acid screws in the distal femur of the rabbit.

After 36 months in the polyglycolic acid group the specimens showed no remaining polymer and loose connective tissue occupied 80% of the screw track. Tissue restoration remained poor at 54 months, the amounts of trabecular bone and haematopoietic elements being significantly lower than those in the intact control group. The amount of trabecular bone within the screw track at 54 months in the polyglycolic acid group was less than in the empty drill holes (p = 0.04). In the poly-laevo-lactic acid group, polymeric material was present in abundance after 54 months, occupying 60% of the cross-section of the core area of the screw track.

When using absorbable internal fixation implants we should recognise that the degradation of the devices will probably not be accompanied by the restoration of normal trabecular bone.

Aims: Meniscus repair has become the procedure of choice for the treatment of meniscal tears whenever possible. However, problems with healing of the repaired meniscus do exist. We have assessed both clinically and with MRI the outcome of meniscal ruptures treated with bioabsorbable arrows. Methods: 74 consecutive patients with 80 longitudinal vertical meniscal tears were treated using polylactide meniscus arrows (Bionx Implants Ltd, Tampere, Finland) during a three year period. Half of the patients had an old meniscal tear (> 6 weeks). The average length of the follow-up was 25 months (range, 6–56 months). The patients who had not received secondary surgery for failed repair during the follow-up period were examined clinically and with MRI. Results: 56 out of 80 meniscal ruptures (70%) healed clinically. However, in 7 of these asymptomatic patients the MRI showed partial healing. In repairs performed in conjunction with ligament reconstruction the healing rate was higher (82%) than in the isolated tears (62%). The poorest results were seen in the very long vertical tears with luxation of the meniscus (43% healing rate). Conclusions: Bioabsorbable arrows offer a good alternative for the treatment of meniscal ruptures, but special attention should be payed on the reliability of the þxation. In long and unstable tears we suggest combined þxation techniques to be used; arrows for the þxation of the posterior horn and inside-out sutures for the corpus area

Background: Healing of segmental diaphyseal bone defects in animals can be enhanced by covering the defects with resorbable polylactide membranes. Based on the results of bone healing in defects 10 mm long in the rabbit radii, it was suggested that the membrane prevents muscle and soft tissue from invading the defect and maintains osteogenic cells and osteogenic substances within the space covered with membrane, thus promoting new bone formation. However, for bone defects larger than a critical size, bone healing did not occur when covered with polylactide membrane. Objectives: To investigate and compare bone regeneration with resorbable polylactide membrane and polylactide sponge in a 20 mm bone defect in rabbit radii. The material used was polylactide (L/DL) 80/20/1. To determine and compare the biomechanical strength of the bone fixation construct with reinforcement by membrane and sponge of such bone defect which were rendered unstable by ulnar osteotomy. Material & method: 20 mm long diaphyseal segmental defects were made in the left radii of adult New Zealand rabbits. Transverse ulnar osteotomies were made at mid-shaft to make the forearm unstable. The rabbits were divided into 4 groups. In group 1, no fixation of the bone were performed and the limbs were immobilized in a plaster for 8 weeks. In group 2, the bone defects were fixed with 1.5 AO miniplate, with 2 screws on each side of the defect. In group 3, the bone defects were fixed similarly and polylactide membranes were used to cover up the bony defect. In group 4, the bone defects were fixed similarly to group 2 and the defects were bridged by sponge of 20 mm long, 3.5 mm in diameter. In group 5, the bone defects were bridged by sponge similar to group 4 and were also covered by polylactide membrane and similar internal fixation were performed. Results: In group 1, there was bone healing bridging the bone ends. However, there was marked shortening of the limbs and all the limbs were deformed. In group 2, there were bone formation at the ends of both proximal bone stumps and distal bone stumps. There was no bone bridging the defect. In group 3,4, there were bone formation across the defect. There was more bone formation in group 4, i.e. the defects were bridged by sponge. Conclusion: Polylactide membrane and sponge promote bone regeneration in 20 mm both defects in the rabbit radii model. There was more bone formation when sponged were employed

Between 1985 and 1994, 1223 patients with malleolar fractures of the ankle were treated by open reduction and internal fixation with absorbable pins and screws, of whom 74 (6.1%) had an obvious inflammatory foreign-body reaction to the implants. Of these 74, ten later developed moderate to severe osteoarthritis of the ankle despite no evidence of incongruity of the articular surface. The implants used in these patients were made from polyglycolide, polylactide or glycolidelactide copolymer. The joint damage seemed to be due to polymeric debris entering the articular cavity through an osteolytic extension of an implant track. The ten patients had a long clinical course which included a vigorous local foreign-body reaction, synovial irritation and subsequent degeneration. At a follow-up of three to nine years, ankle arthrodesis had been necessary in two patients and is being considered for another two. The incidence of these changes in the whole series was 0.8%, which is not high, but awareness of this possible late complication is essential