We inserted two hydroxyapatite (HA)-coated implants with crystallinities of either 50% (HA-50%) or 75% (HA-75%) bilaterally into the medial femoral condyles of the knees of 16 dogs. The implants were allocated to two groups with implantation periods of 16 and 32 weeks. They were weight-bearing and subjected to controlled micromovement of 250 μm during each gait cycle. After 16 weeks, mechanical fixation of the HA-50% implants was increased threefold as compared with the HA-75% implants. After 32 weeks there was no difference between HA-50% and HA-75%. Fixation of HA-75% increased from 16 to 32 weeks whereas that of HA-50% was unchanged. HA-50% implants had 100% more bone ingrowth than HA-75% implants after 16 weeks. More HA coating was removed on HA-50% implants compared with HA-75% implants after both 16 and 32 weeks. No further loss of the HA coating was shown from 16 to 32 weeks. Our study suggests that the crystallinity of the HA coating is an important factor in its bioactivity and resorption during weight-bearing conditions. Our findings suggest two phases of coating resorption, an initial rapid loss, followed by a slow loss. Resorbed HA coating was partly replaced by bone ingrowth, suggesting that implant fixation will be durable

Impacted bone allograft is often used in revision joint replacement. Hydroxyapatite granules have been suggested as a substitute or to enhance morcellised bone allograft. We hypothesised that adding osteogenic protein-1 to a composite of bone allograft and non-resorbable hydroxyapatite granules (ProOsteon) would improve the incorporation of bone and implant fixation. We also compared the response to using ProOsteon alone against bone allograft used in isolation. We implanted two non-weight-bearing hydroxyapatite-coated implants into each proximal humerus of six dogs, with each implant surrounded by a concentric 3 mm gap. These gaps were randomly allocated to four different procedures in each dog: 1) bone allograft used on its own; 2) ProOsteon used on its own; 3) allograft and ProOsteon used together; or 4) allograft and ProOsteon with the addition of osteogenic protein-1. After three weeks osteogenic protein-1 increased bone formation and the energy absorption of implants grafted with allograft and ProOsteon. A composite of allograft, ProOsteon and osteogenic protein-1 was comparable, but not superior to, allograft used on its own. ProOsteon alone cannot be recommended as a substitute for allograft around non-cemented implants, but should be used to extend the volume of the graft, preferably with the addition of a growth factor

The management of comminuted metaphyseal fractures is a technical challenge and satisfactory outcomes of such fixations often remain elusive. The small articular fragments and bone loss often make it difficult for standard fixation implants for proper fixation. We developed a novel technique to achieve anatomical reduction in multiple cases of comminuted metaphyseal fractures at different sites by employing the cantilever mechanism with the help of multiple thin Kirschner wires augmented by standard fixation implants. We performed a retrospective study of 10 patients with different metaphyseal fractures complicated by comminution and loss of bone stock. All patients were treated with the help of cantilever mechanism using multiple Kirschner wires augmented by compression plates. All the patients were operated by the same surgeon between November 2020 to March 2021 and followed up till March 2023. Surgical outcomes were evaluated according to the clinical and radiological criteria. A total of 10 patients were included in the study. Since we only included patients with highly unstable and comminuted fractures which were difficult to fix with traditional methods, the number of patients in the study were less. All 10 patients showed satisfactory clinical and radiological union at the end of the study with good range of motion. One of the patient in the study had post-operative wound complication which was managed conservatively with regular dressings and oral antibiotics. Comminuted metaphyseal fractures might differ in pattern and presentation with every patient and there can be no standard treatment for all. The cantilever technique of fracture fixation is based on the principle of cantilever mechanism used in bridges and helps achieve good anatomical reduction and fixation. It provides a decent alternative when standard modes of fixation don't give desired result owing to comminuted nature of fractures and deficiency of bone stock

Introduction and Objective. When using radiation intraoperatively, a surgeon should aim to maintain the dose as low as reasonably achievable to obtain the diagnostic or therapeutic goal. The UK Health Protection Agency reported mean radiation dose-area-product (DAP) of 4 Gy cm2 for hip procedures. We aimed to investigate factors associated with increased radiation exposure in fixation of proximal femur fractures. Materials and Methods. We assessed 369 neck of femur fractures between April 2019 and April 2020 in one district general hospital. Fractures were classified as extracapsular or intracapsular and into subtypes as per AO classification. Data was collected on type of fractures, implants used, level of surgeon, duration of surgery and DAP. Types of fractures were subclassified as complex (multifragmentary, subtrochanteric and reverse oblique) or simple. Results. Patients with fractures fixed with DHS, short PFNA, long PFNA and cannulated screws were included. 50% of our patients were fixed with hemiarthroplasty or total hip replacement and were therefore excluded. 184 patients were included in the analysis. There was a significant association of higher DAP with fracture subtype (P=0.001), fracture complexity (P<0.001), if an additional implant was used (P=0.001), if fixation was satisfactory (P=0.002) and the operative time (P<0.001). DAP was higher in PFNA than DHS and greatest in Long PFNA. There was some evidence of association between the level of the surgeon and DAP, although this was not statistically significant (P=0.069) and remained not significant after adjusting for the variables (fracture complexity, fixation or implant used) (p=0.32). Conclusions. Increased radiation in proximal femur fractures is seen in fixation of complex fractures, certain subtypes, the type of implant used and if an additional implant was required. Seniority of surgeon did not result in less radiation exposure even when adjusting for other factors, which is in contrast to other published studies

A significant source of failure for external fixation devices is loosening of the fixation implant. As bone competence drops with ageing or disease such as osteoporosis, the risk of loosening is likely to increase. However it is not clear how fixator configuration should be adapted to minimise loosening in weaker bone. The aim of this study was to assess the effect of bone competence on the yielding of bone tissue surrounding fixation implants, and thereby inform the selection of fixator configuration to minimise loosening. External fixation of the tibial midshaft using half-pins and Illizarov wires was modelled using finite-element analysis. Half-pin configurations of two and three stainless steel and titanium pins pins were assessed. Illizarov wire configurations of two and four wires were studied, over a range of wire tensions. Bone competence was varied by changing the cortical thickness and elastic properties of the bone fragments to approximate: a) young, high-density bone, b) middle-aged, mid-porosity bone and c) old-aged, severely porous bone. Bone elastic properties were taken from a recent study of cortical bone conducted by the authors. The interaction between implants and bone was modelled with contact analysis, enabling realistic separation. Implant loosening was included using a bone-specific, strain-based yield criterion. Regions where bone tissue yielded were identified as likely sites of loosening. In all cases loading was applied to simulate a one-legged stance. Half-pin fixation. Increasing the number of half-pins from two to three produced an approximate 80% reduction of yielded bone volume in all age groups. The volume of yielded bone increased with ageing, approximately three times greater in old-aged bone than in young bone. In the young and middle-aged cases yielded bone never penetrated the full cortex. Contrastingly, the full cortex was yielded in the old-aged bone fragments for both two- and three-pin fixation. In all cases the volume of yielded bone was greater at the pin(s) nearest to the fracture gap. The use of titanium pins increased the volume of yielded bone around half-pins by approximately 1.7 times. These results suggest bone competence, number of half-pins, location of half-pins and half-pin material all significantly influence implant loosening. Illizarov wire fixation. Increasing the number of Illizarov wires reduced the volume of yielded bone by approximately 60% in all age groups. The volume of yielded bone increased with ageing by a factor of approximately 2.0 times from young to old bone. Bone yielding never progressed through the entire cortex; it reached a maximum of 70% of the cortical thickness in two-wire fixation of the old-aged bone fragment. This is a possible reason for the lower rate of loosening in Illizarov wire fixation as compared to half-pin fixation. Increasing wire tension reduced the volume of yielded bone. These results suggest that bone competence, number of wires, wire tension and wire arrangement significantly influence loosening

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

The Temporomandibular joint (TMJ) is a complex and important joint for daily activities, and the alloplastic implant is recommended as the best solution, after repeated surgeries, failed autogenous grafts, highly inflammatory metabolic arthritis, fibrous or bony ankyloses. Some complications in total TMJ replacement are associated with implant design, screw fixation failure, implant displacement, fibrous tissue formation, (Speculand, et al. 2000). Some numeric studies evaluate the number of screws needed to guarantee the good fixation and suggest a minimum of three (Ramos et al. 2015), but is a controversy conclusion. The Biomet Microfixation TMJ stock prosthesis, Jacksonville, FL, USA is one of the three or four in the market. Clinical studies published by this device between 2005 and 2015 indicate a success rate of around 84 to 91% with improvements in mouth opening, a decrease in pain score and improved quality of life. The present study analyses experimentally the load transfer of this device. The intact, clean cadaveric ramus was instrumented with four rosettes model (KFG-1-120-D17-11 L3M2S, by Kywoa Electronic Instruments Co™, Japan), one in lateral region, two in lateral region and one in lingual face. The condyle was loaded with the temporal reaction; the load was applied constant velocity of 1mm/min in three continuum phases and with three stops at 100N, 200N and 300N. Next, the Biomet microfixation implant was fixed to the same cadaveric mandibular ramus after resection. The implant was 50mm in length. It was fixed with five 6AL/4V Titanium self-tapping screws with 2.7mm diameter were long enough to establish a bi-cortical support. The screws were screwed into the bone with a torque-screwdriver a constant torque of 0.2Nm. The same rosettes were analyzed before and after implantation and the mandible displacement two. The experimental results for the mandibular ramus present a linear behavior up to 300N load in condyle, with the Biomet implant influencing strain distribution; the maximum influence was near the implant (rosette #4) is around 59%. The average vertical displacement of the mandibular ramus (300N) was measured by machine: 1.18 (±0.02) mm for the intact mandibular ramus and 1.21 (±0.02) mm for the implanted one, which represents a 2.8% differences between the experimental models and reduce of stiffness. The maximum principal strain deformation was observed in the rosette #3 with 1360µε more 20% than the intact mandible for 300N of reaction. The experimental results show that the Biomet TMJ mandibular ramus implant changes the load transfer in the ramus, compared to the intact, with its strain shielding effect. The results indicate the minimum number of screws is three to guarantee a good load transfer but the surface preparation of condyle presents an important factor

Summary. Metastatic spinal disease is a common entity of much debate in terms of ideal surgical treatment. The introduction of MIS can be a game-changer in the treatment of MSD due to less peri-operative morbidity and allowing earlier radiotherapy and/or chemotherapy. Introduction. Less invasive techniques have always been welcome for management of patients with ‘Metastatic Spinal Disorders’. This is because these patients can be poor candidates for extensive / major invasive surgery even though radiologically, there may be an indication for one. The aim of the treatment with Minimal Invasive Fixation (MIS) systems is mainly for ‘pain relief’ than to radically decrease tumour burden or to achieve near total spinal cord decompression, which could be major presentations in these patients. These procedures address the ‘spinal instability’ very well and they can address pain associated with compression fractures resulting from metastatic disease from a solid organ as well as multiple myeloma with minimal complications. These procedures can be combined with radiology and chemotherapy without much concern for wound problems in the way of infection or dehiscence. They also have a great advantage of timing of adjunct therapy closer to the index procedure. The disadvantage, however, are they do not allow thorough decompression of the spinal cord. There could also be problem in addressing patients who have severe vertebral height loss or loss of integrity of the anterior column where anterior column reconstruction may be required. There is a risk of inadequate fixation or implant loosening or failure. We aim to examine the results of MIS surgery in our department and support the rationale for its use. Patients and Methods. We prospectively collected data of patients who underwent MIS posterior instrumentation for MSD. Between June 2011 and December 2012, 10 patients presented with acute motor deficit, instability and/or threatening radiological features. Effectiveness of MIS was assessed in terms of operative parameters and clinical outcomes. Results. No patient suffered intra-operative complications. The median surgical time was 198 minutes (range: 149 – 403), median blood loss was 100 ml (range: 60 – 400). All patients maintained full neurological function and reported effective pain reduction. All patients were discharged with a median hospital stay was 13 days (range: 4 – 45) post-surgery. 9 patients started oncological treatment as planned. The median time in 7 patients who had radiotherapy post-surgery was 23 days (range: 20 – 40). Chemotherapy was initiated in 4 patients at a median of 9 days post-surgery (range: 6 – 23). No patient as yet has required open procedure due to progression of the disease. Discussion/Conclusion. We have shown that satisfactory outcomes are achievable with MIS in a selected group of patients with MSD. While our results are limited by small study size, we have been able to improve patient quality of living through minimally invasive intervention. By reducing surgical morbidity and enabling early implementation of oncological treatment, MIS has the potential to re-evaluate multi-disciplinary decision making for early surgery in MSD

The effect of zoledronic acid on bone ingrowth was examined in an animal model in which porous tantalum implants were placed bilaterally within the ulnae of seven dogs. Zoledronic acid in saline was administered via a single post-operative intravenous injection at a dose of 0.1 mg/kg. The ulnae were harvested six weeks after surgery. Undecalcified transverse histological sections of the implant-bone interfaces were imaged with backscattered scanning electron microscopy and the percentage of available pore space that was filled with new bone was calculated. The mean extent of bone ingrowth was 6.6% for the control implants and 12.2% for the zoledronic acid-treated implants, an absolute difference of 5.6% (95% confidence interval, 1.2 to 10.1) and a relative difference of 85% which was statistically significant. Individual islands of new bone formation within the implant pores were similar in number in both groups but were 69% larger in the zoledronic acid-treated group. The bisphosphonate zoledronic acid should be further investigated for use in accelerating or enhancing the biological fixation of implants to bone

We have developed a bioactive bone cement (BA cement) consisting of Bis-GMA resin and bioactive glass powder. It has high compressive and tensile strengths, a low curing temperature and its bioactivity allows it to bond directly with bone. We operated on the 18 femora of nine mongrel dogs for intercalary replacement of part of the bone by a metal prosthesis using either PMMA cement or BA cement for fixation. Three dogs were killed at each of 4, 12 and 26 weeks after surgery for the evaluation of fixation strength by a push-out test and for histological examination by Giemsa surface staining and SEM. Fixation strengths with PMMA cement at 4, 12 and 26 weeks after surgery were 46.8 ± 18.9, 50.0 ± 24.7, and 58.2 ± 28.9 kgf (mean ±SD), respectively. Those with BA cement were 56.8 ± 26.1, 67.2 ± 19.2, and 72.8 ± 22.2 kgf, respectively. Fibrous tissue intervened between bone and PMMA cement but BA cement had bonded directly to bone at 12 and 26 weeks. This suggests that BA cement will be useful in providing long-lasting fixation of implants to bone under weight-bearing conditions

Impaction allograft is an established method of securing initial stability of an implant in arthroplasty. Subsequent bone integration can be prolonged, and the volume of allograft may not be maintained. Intermittent administration of parathyroid hormone has an anabolic effect on bone and may therefore improve integration of an implant.

Using a canine implant model we tested the hypothesis that administration of parathyroid hormone may improve osseointegration of implants surrounded by bone graft. In 20 dogs a cylindrical porous-coated titanium alloy implant was inserted into normal cancellous bone in the proximal humerus and surrounded by a circumferential gap of 2.5 mm. Morsellised allograft was impacted around the implant. Half of the animals were given daily injections of human parathyroid hormone (1–34) 5 μg/kg for four weeks and half received control injections. The two groups were compared by mechanical testing and histomorphometry. We observed a significant increase in new bone formation within the bone graft in the parathyroid hormone group. There were no significant differences in the volume of allograft, bone-implant contact or in the mechanical parameters.

These findings suggest that parathyroid hormone improves new bone formation in impacted morsellised allograft around an implant and retains the graft volume without significant resorption. Fixation of the implant was neither improved nor compromised at the final follow-up of four weeks.

We used a goat model of a contaminated musculoskeletal defect to determine the effectiveness of rapidly-resorbing calcium-sulphate pellets containing amikacin to reduce the local bacterial count. Our findings showed that this treatment eradicated the bacteria quickly, performed as well as standard polymethylmethacrylate mixed with an antibiotic and had many advantages over the latter. The pellets were prepared before surgery and absorbed completely. They released all of the antibiotic and did not require a subsequent operation for their removal. Our study indicated that locally administered antibiotics reduced bacteria within the wound rapidly. This method of treatment may have an important role in decreasing the rate of infection in contaminated wounds.