Bony Ingrowth Research Articles

Failure of an uncemented press-fit acetabular cup in primary total hip arthroplasty.

We reviewed fifteen primary total hip replacements performed using the uncemented, non-porous coated press-fit AcSys Shearer Cup. A modular titanium straight femoral stem with a 32mm head was used in all cases. The mean age of the group containing five males and 10 females was 66 years. Eight cups have been revised for aseptic loosening at a mean of seven years and the remaining four cups are radiologically loose. At revision surgery none of the cups showed any evidence of bony ingrowth. Our 10-year results with this cup indicate an unacceptably high failure rate of 80%. Absence of bony ingrowth and the lack of a secure locking mechanism between the polyethylene liner and the metal shell are the most important causes of failure. The use of a 32-mm diameter head and implantation of the cup in an open position contributed to this failure. Even though this cup is no longer manufactured, our experience suggests that all non-porous coated cups should be closely followed up. (Hip International 2002; 4: 371-7).

Early Outcomes of Anterior Cervical Discectomy and Fusion Using a Porous PEEK Interbody Fusion Device

Background: Recently, porous surface polyether-etherketone (PEEK) implants have been developed to interact with adjacent endplates. Our goal was to evaluate the efficacy of novel high-strength, porous PEEK interbody fusion devices for anterior cervical discectomy and fusion (ACDF) in patients with symptomatic single-level and multilevel degenerative cervical disc disease at 1 year. Methods: Fifty consecutive patients (31 women, 19 men; average age, 60 years) with degenerative cervical disc disease underwent ACDF using a porous PEEK interbody implant and plate. There were 11 1-level; 23 2-level, and 16 3-level fusions between C3 and C7. Patients were assessed at 1.5, 3, 6, and 12 months. Standardized outcome measures were used to evaluate the patient’s condition before and after surgery. Plain radiographs were used to assess fusion, bony in-growth, subsidence, and implant migration. Sagittal plane angulation was measured on neutral lateral radiographs and determined by Cobb’s criteria. Intradiscal distraction and subsidence were measured by assessing the vertical distance between the midpoints of the adjacent vertebral endplates. Results: At 12 months after surgery, all patients showed improvement in Oswestry Neck Disability Index and neck and arm pain scores. Similarly, at 12 months, all patients showed radiographic fusion. No patient demonstrated motion across the interspace on flexion-extension lateral radiographs. Sagittal plane angulation improved to an average of -6° (range, -2° to -8°) with no measurable evidence of implant migration or subsidence. Average disc space height increased more than 4 mm. No patient had measurable radiographic evidence of a pseudarthrosis or halo formation around the implant. Conclusion: One-year results in this prospective nonrandomized study show that porous-surface PEEK is a clinically viable alternative for improving osseointegration and fusion rates of interbody implants to treat degenerative cervical disc disease.

Micro-EDM induced surface modification of titanium alloy for biocompatibility

The objective of the current study is to investigate the surface modifications of an implant material Ti-6Al-4V with respect to biocompatibility after machined by micro-electro-discharge machining (micro-EDM). The machined surface characteristics were evaluated by the surface topography, crater sizes, elemental composition, and surface microhardness. It was found that micro-EDM can produce surface roughness lower than 100 microns, which is necessary on the implant surface to promote cell growth around the implant. The roughness of the machined surface can be controlled by controlling the crater sizes, as a direct relationship between crater sizes and discharge energy was observed. A porous and thick titanium oxide (TiO2) layer was observed on the machined surface, which can induce bony ingrowth into the porous structure, resulting in morphological fixation of the implants to the bone. No known toxic substances were observed on the machined surface of Ti-6Al-4V that could be harmful for human body. Moreover, slight increase in microhardness of the machined surface was observed after micro-EDM, which could be beneficial in biomedical orthodontic applications for wear resistance.

Magnesium alloy based interference screw developed for ACL reconstruction attenuates peri-tunnel bone loss in rabbits

Peri-tunnel bone loss after anterior cruciate ligament (ACL) reconstruction is often observed clinically, which may detrimentally affect tendon graft integration with surrounding bone tissue. Biodegradable magnesium (Mg) based fixators in terms of interference screws may be suitable for fixation of the tendon graft due to their favorable effects on promotion of new bone formation. However, the poor mechanical strength of Mg is still one of the major challenges for its clinical applications. The addition of alloying elements into Mg is one of the strategies to improve their mechanical properties. Here, we prepared magnesium (Mg)-(4 and 6 wt%) zinc (Zn)-(0.2, 0.5, 1 and 2 wt%) strontium(Sr) alloys and tested their potential for attenuating peri-tunnel bone loss in ACL reconstruction. The optimal (6 wt%) Zn and (0.5 wt%) Sr contents were screened with respect to the microstructures, mechanical properties and corrosion behavior of these alloys. As compared to pure Mg, Mg-6Zn-0.5Sr rods and screws showed significantly higher torque and torsional stiffness in both numerical and experimental analysis. The in vitro cyto-compatibility of Mg-6Zn-0.5Sr alloy was assessed with MTT test and fluorescence assay. The Mg-6Zn-0.5Sr interference screw was designed for fixation of the tendon graft to the femoral tunnel in a rabbit model of ACL reconstruction, with a commercially available poly-lactide (PLA) screw for comparison. In vivo high resolution peripheral quantitative computed tomography (HR-pQCT) scanning was performed to measure the degradation behavior of Mg-6Zn-0.5Sr interference screws and peri-tunnel bone quality at 0, 6, 12 and 16 weeks post-surgically. Mg-6Zn-0.5Sr interference screw was completely degraded within 12 weeks after surgery. The peri-tunnel bone loss was significantly attenuated in the Mg-6Zn-0.5Sr group when compared to the PLA group. Importantly, the bony ingrowth rapidly filled the cavity left by the complete degradation of Mg-6Zn-0.5Sr screws at 16 weeks. In histological analysis, more bone formation was observed in peri-tunnel region in the Mg-6Zn-0.5Sr group in comparison to the PLA group at 6 and 16 weeks after surgery. The femur-tendon graft-tibia complex was harvested at the end of week 6 and 16 post-operation for tensile testing. The maximum load to failure was significantly improved in the Mg-6Zn-0.5Sr group at week 16 post-operation. Therefore, our results indicate the potential clinical application of MgZnSr based interference screws in ACL reconstruction.

Additive manufactured push-fit implant fixation with screw-strength pull out.

ABSTRACTAdditive manufacturing offers exciting new possibilities for improving long‐term metallic implant fixation in bone through enabling open porous structures for bony ingrowth. The aim of this research was to investigate how the technology could also improve initial fixation, a precursor to successful long‐term fixation. A new barbed fixation mechanism, relying on flexible struts was proposed and manufactured as a push‐fit peg. The technology was optimized using a synthetic bone model and compared with conventional press‐fit peg controls tested over a range of interference fits. Optimum designs, achieving maximum pull‐out force, were subsequently tested in a cadaveric femoral condyle model. The barbed fixation surface provided more than double the pull‐out force for less than a third of the insertion force compared to the best performing conventional press‐fit peg (p < 0.001). Indeed, it provided screw‐strength pull out from a push‐fit device (1,124 ± 146 N). This step change in implant fixation potential offers new capabilities for low profile, minimally invasive implant design, while providing new options to simplify surgery, allowing for one‐piece push‐fit components with high levels of initial stability. © 2017 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of the Orthopaedic Research Society. J Orthop Res 36:1508–1518, 2018.

Response of umbilical cord mesenchymal stromal cells to varying titanium topographical signals.

A wide variety of titanium implant modifications have been developed to improve tissue- or cell-material interactions including bone bonding, implant failure, and contact osteogenesis. Osteogenesis can be stimulated by mechanobiological signals such as topography though translation of in vivo reactions to in vitro bioactivity and stem cell culture data, and vice versa, is challenging. We hypothesized that a systematic in vitro approach comparing clinically well-accepted implant surface topographical modifications could shed light on potential cell biological mechanisms provoked by submicron-, micron- or macrostructured surfaces. In this study, we investigated the response of umbilical cord derived mesenchymal stromal cells (UC-MSCs) to anodized, particle blasted, and plasma sprayed highly porous Plasmapore surfaces, which is known to promote bony ingrowth in vivo. After 21 days, UC-MSCs undergo a morphological shift from a 2D to 3D behavior on micro- or macrostructures visualized by actin-vinculin fluorescence and are able to fill the porous surfaces completely. Cell viability after 7 days was significantly decreased on the micro- and macrostructured surfaces particle blasted and Plasmapore, compared to polished controls. The analysis of osteogenic differentiation under noninduced conditions revealed a significantly elevated ALP activity on Plasmapore, indicating a beneficial effect of this macrostructured surface toward osteogenic differentiation supported by late elevated gene expression of osteopontin evaluated by qPCR. Mineralization as well as in vitro bioactivity was pronounced on anodized surfaces. Our findings point to synergistic implant modification strategies allowing early contact osteogenesis and bone ingrowth for future implant designs. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 180-191, 2018.

Magnesium (Mg) based interference screws developed for promoting tendon graft incorporation in bone tunnel in rabbits.

How to promote tendon-bone junction healing is one of the major challenging issues for satisfactory clinical outcomes in patients after ACL reconstruction. The improvement of bony ingrowth into the tendon graft-bone interface can enhance the tendon graft osteointegration. In this study, we applied Mg based interference screws to fix the tendon graft in rabbits and found the use of Mg screws could accelerate and significantly increase mineralized matrix formation at the tendon-bone interface in animals when compared to those with Ti screws. We elucidated the mechanism behind the favorable effects of Mg screws on the graft healing in both in vitro and in vivo studies from multiscale technologies. The optimized interface structure and function in Mg group may be ascribed to the improved cell migration capability, enhanced cell adhesion strength and promoted osteogenic differentiation ability of BMSCs under the stimuli of Mg ions degraded from implanted Mg screws. Our findings may help us broaden our thinking in the application potential of Mg interference screws in future clinical trials.

Early Clinical and Radiographic Outcomes of Trabecular Metal Total Ankle Using Transfibular Approach

Category: Ankle, Ankle Arthritis Introduction/Purpose: In the last two decades, total ankle replacement (TAR) has gained more acceptance as a treatment option in patients with end-stage ankle osteoarthritis. However, there is a lack of literature on TAR using a lateral transfibular approach. Therefore, we sought to report early clinical and radiographic results of a patient cohort treated with TAR using a lateral transfibular approach by a single surgeon. Methods: Fifty-five primary total ankle arthroplasties using the Zimmer trabecular metal implant were performed in 54 patients (29 men and 25 women; mean age, 67.0 years) from October 2012 to December 2014. Clinical assessment including pain evaluation and measurement of ankle range of motion was done preoperatively and at the latest follow-up. Weight-bearing radiographs were used to determine the angular alignment of the tibial and talar components and to analyze the bone-implant interface. Intraoperative and postoperative complications, revision surgeries, and failures were evaluated. Results: Implant survival was 93% at 36 months follow-up. There were 3 revisions of a tibial component due to aseptic loosening. In 10 of 55 procedures, a secondary procedure was performed during follow-up. Mean follow-up duration was 26.6 ± 4.2 months. No delayed union or non-union was observed for fibula healing. The average VAS pain score decreased significantly from 7.9 ± 1.3 to 0.8 ± 1.2. The average total range of motion increased significantly from 22.9° ± 11.8° to 40.2° ± 11.8°. Conclusion: Early results of Zimmer trabecular metal total ankle replacement demonstrated improved patient-reported outcomes and increased ankle motion at a minimum follow-up of one year. In the first 55 consecutive cases, the fibular osteotomy required for access to the ankle healed without complications. Painful early loosening requiring revision due to lack of bony ingrowth was seen in 3 of 55 cases.

Evaluation of a polyetheretherketone (PEEK) titanium composite interbody spacer in an ovine lumbar interbody fusion model: biomechanical, microcomputed tomographic, and histologic analyses

Background ContextThe most commonly used materials used for interbody cages are titanium metal and polymer polyetheretherketone (PEEK). Both of these materials have demonstrated good biocompatibility. A major disadvantage associated with solid titanium cages is their radiopacity, limiting the postoperative monitoring of spinal fusion via standard imaging modalities. However, PEEK is radiolucent, allowing for a temporal assessment of the fusion mass by clinicians. On the other hand, PEEK is hydrophobic, which can limit bony ingrowth. Although both PEEK and titanium have demonstrated clinical success in obtaining a solid spinal fusion, innovations are being developed to improve fusion rates and to create stronger constructs using hybrid additive manufacturing approaches by incorporating both materials into a single interbody device. PurposeThe purpose of this study was to examine the interbody fusion characteristic of a PEEK Titanium Composite (PTC) cage for use in lumbar fusion. Study Design/SettingThirty-four mature female sheep underwent two-level (L2–L3 and L4–L5) interbody fusion using either a PEEK or a PTC cage (one of each per animal). Animals were sacrificed at 0, 8, 12, and 18 weeks post surgery. Materials and MethodsPost sacrifice, each surgically treated functional spinal unit underwent non-destructive kinematic testing, microcomputed tomography scanning, and histomorphometric analyses. ResultsRelative to the standard PEEK cages, the PTC constructs demonstrated significant reductions in ranges of motion and a significant increase in stiffness. These biomechanical findings were reinforced by the presence of significantly more bone at the fusion site as well as ingrowth into the porous end plates. ConclusionsOverall, the results indicate that PTC interbody devices could potentially lead to a more robust intervertebral fusion relative to a standard PEEK device in a clinical setting.

Assessing agreement between preclinical magnetic resonance imaging and histology: An evaluation of their image qualities and quantitative results.

One consequence of demographic change is the increasing demand for biocompatible materials for use in implants and prostheses. This is accompanied by a growing number of experimental animals because the interactions between new biomaterials and its host tissue have to be investigated. To evaluate novel materials and engineered tissues the use of non-destructive imaging modalities have been identified as a strategic priority. This provides the opportunity for studying interactions repeatedly with individual animals, along with the advantages of reduced biological variability and decreased number of laboratory animals. However, histological techniques are still the golden standard in preclinical biomaterial research. The present article demonstrates a detailed method comparison between histology and magnetic resonance imaging. This includes the presentation of their image qualities as well as the detailed statistical analysis for assessing agreement between quantitative measures. Exemplarily, the bony ingrowth of tissue engineered bone substitutes for treatment of a cleft-like maxillary bone defect has been evaluated. By using a graphical concordance analysis the mean difference between MRI results and histomorphometrical measures has been examined. The analysis revealed a slightly but significant bias in the case of the bone volume and a clearly significant deviation for the remaining defect width But the study although showed a considerable effect of the analyzed section position to the quantitative result. It could be proven, that the bias of the data sets was less originated due to the imaging modalities, but mainly on the evaluation of different slice positions. The article demonstrated that method comparisons not always need the use of an independent animal study, additionally.

Effectiveness of acetabular revision using a metal reconstruction cage

To explore the clinical outcomes of acetabular revision using a metal reconstruction cage. Between October 2006 and October 2013, 16 patients (16 hips) underwent acetabular revision with a metal reconstruction cage. There were 4 males and 12 females, with the mean age of 62.7 years (range, 49-78 years). The time from total hip arthroplasty to revision was 3-15 years (mean, 8.2 years). The causes for revision were aseptic acetabular loosening in 15 cases, and femoral periprosthetic fracture (Vancouver type B3) in 1 case. According to the American Academy of Orthopaedic Surgeons (AAOS) classification, there were 12 cases of type III and 4 cases of type IV; according to the Paprosky classification, there were 12 cases of type IIIA and 4 cases of type IIIB. Harris score was used for hip function evaluation, and visual analogue scale (VAS) for pain in the thigh. X-ray films were taken for imaging evaluation. Healing of incision by first intention was obtained in all patients. Deep venous thrombosis occurred in 1 patient, and was cured after anticoagulation therapy. No complications of infection, neurovascular injury, and prosthetic dislocation were found. Sixteen patients were followed up 6.8 years on average (range, 2-9 years). The Harris score was significantly increased from preoperative 42.44±4.66 to 91.88±3.28 at last follow-up ( t=-106.30, P=0.00). Two patients had mild pain in the thigh, but pain disappeared at 1 year after operation. At immediate after operation, the abduction angle was 37-54° (mean, 42.9°). The distance between acetabular rotation centre and teardrop line was (33.67±12.19) mm for preoperative value and was (20.67±9.63) mm for postoperative value, showing significant difference ( t=-9.60, P=0.00). The distance between acetabular rotation centre and lateral teardrop was (34.98±12.30) mm for preoperative value and was (40.04±6.61) mm for postoperative value, showing significant difference ( t=-3.15, P=0.00). X-ray film results showed bony fusion at the osteotomy sites at 4 to 12 months after operation. No continuous radiolucent line, prosthetic dislocation, or osteolysis was found, and bony ingrowth was observed in all patients. No patient received re-revision due to prosthetic loosening. The metal reconstruction cage for acetabular revision can achieve good effectiveness for patients with serious bone defect.

The Humeral Implant in Shoulder Arthroplasty.

Humeral hemiarthroplasty, anatomic total shoulder arthroplasty, and reverse total shoulder arthroplasty all rely on a prosthetic articular surface fixed to the proximal humerus. Humeral implant designs have changed considerably as a result of improved understanding of proximal humeral anatomy and prosthetic biomechanics. Fixed, monoblock implants have been superseded by modular implants with variable inclination, offset, version, and stem length. Press-fit designs now commonly have surface coatings that allow bony ingrowth. Metaphyseal fixation is often favored over diaphyseal fixation. Both cemented and noncemented fixation continue to be used, and each of these techniques has advantages and disadvantages. Although aseptic loosening rarely requires revision, complications, such as osteolysis, stress shielding, radiolucent lines, and proximal humeral bone loss, can occur. Humeral periprosthetic fractures continue to be a disabling complication and are difficult to manage. Innovations such as short-stemmed implants, stemless implants, and platform stems are currently under clinical investigation.

Cementless total hip arthroplasty with extended sliding trochanteric osteotomy for high congenital hip dislocation: A retrospective study.

Total hip arthroplasty (THA) for high congenital hip dislocation (CHD) is technically demanding. The purpose of this retrospective study was to evaluate the results of cementless THA combined with extended sliding trochanteric osteotomy. We also assessed whether chronic low back pain was relieved after surgery.The study included 19 patients (23 hips) with high CHD treated with cementless THA using extended sliding trochanteric osteotomy technique. Clinical and radiographic outcomes were evaluated.Harris Hip Score, WOMAC score, visual analog scale for low back pain and Trendelenburg sign were significantly improved (P < 0.01) compared with the preoperative. Average limb-length discrepancy in the 15 unilateral hips was reduced from 38.2 ± 7.9 mm to 6.7 ± 4.1 mm (P < 0.01). No dislocation, deep vein thrombosis, or infection occurred. Two patients (8.7%) developed sciatic nerve palsy. One (4.3%) developed symptomatic greater trochanteric bursitis. Two (8.7%) sustained proximal femur shaft fracture during implantation of the femoral component. All femoral components showed successful bony ingrowth at the final follow-up. No stem subsidence was detected. There was no acetabular loosening. Bony union of the reattached greater trochanter was obtained in all hips. Wire breakage occurred in 3 hips (13%).Cementless THA with extended sliding trochanteric osteotomy may be appropriate options for patients with high CHD.

Initial Stability of Cemented vs Cementless Tibial Components Under Cyclic Load

BackgroundCement fixation of total knee components remains the gold standard despite resurgence in cementless fixation with the goal of long-term durable fixation. Initial stability is paramount to achieve bony ingrowth of cementless components. MethodsTwelve cemented and cementless tibial baseplates were implanted into sawbones and tested using a physiological medial-lateral load distribution for 10,000 cycles to represent 8 weeks of in vivo function. Micromotion was measured at 5 locations around the baseplate during loading. ResultsCycling had a significant effect on the change in micromotion between maximum and minimum loads at the anterior, medial, lateral, posteromedial, and posterolateral tray edge locations. A significant effect of fixation technique was detected for the anterior (P < .001), medial (P = .002), and lateral (P = .0056) locations but not for the posteromedial (P = .36) or posterolateral (P = .82) locations. Differences in micromotion between cemented and cementless components did not exceed 150 μm at any tested location. ConclusionThe micromotion experienced by cementless tibial components in the present study may indicate a lower initial mechanical stability than the cemented group. However, this difference in initial stability may be subclinical because the differences between average cemented and cementless micromotion were <150 μm at all measured locations under the loading regime implemented.

Revision total knee arthroplasty with porous-coated metaphyseal sleeves provides radiographic ingrowth and stable fixation.

Porous-coated metaphyseal sleeves are designed to fill bone defects and facilitate osseointegration when bone loss in encountered during revision total knee arthroplasty (TKA). The purpose of this study is to evaluate short-term results of porous-coated metaphyseal sleeves with regards to implant fixation and clinical outcomes. A retrospective review was conducted on 50 patients (79 sleeves-49 tibial and 30 femoral) who had a press-fit metaphyseal sleeve with revision TKA. Tibial and femoral bone loss was classified according to the Anderson Orthopaedic Research Institute (AORI) bone defect classification. Post-operative complications of infection, revision surgery, and dislocation were assessed. Follow-up radiographs were evaluated for signs of loosening using the criteria developed by the Knee Society. The median follow-up was 58.8months (range 25.8-93.0months). The bone loss classifications were 1 type 1, 30 type 2a, 2 type 2b, and 17 type 3, and with regards to the femur, 5 were type 1, 8 type 2a, 31 type 2b, and 6 type 3. At final follow-up, 41/45 (91.1%) tibial and 28/29 (96.6%) femoral sleeves showed radiographic evidence of ingrowth. Of these 69 patients, all showed radiographic evidence of bony ingrowth. Three sleeves were revised for infection and two for loosening. The re-operation rate for loosening was 5/74 (6.8%) and for any reason was 14/74 (18.9%). Modular porous-coated press fit metaphyseal sleeves fill defects and provide evidence of radiographic ingrowth. Short-term stable fixation can be achieved with sleeves, which is helpful as more patients undergo revision total knee arthroplasty with greater bone loss. Longer duration studies are needed to ascertain the survival rate of these implants. IV.

Efficacy of a modified coagulation factor substitution for total hip arthroplasty in patients with end-stage haemophilic arthropathy.

Total hip arthroplasty (THA) is an effective treatment for end-stage haemophilic arthropathy, and substitution therapy plays a key role in the success of THA. The aim of this study was to evaluate the efficacy of a modified coagulation factor substitution regime in THA. Nineteen haemophiliac patients (20 hips) who received primary cementless THA were enrolled. Based on World Federation of Haemophilia (WFH) guideline, a modified coagulation factor substitution regime was adopted. Blood loss, implant survival rates and complications were reviewed, retrospectively. The mean age at surgery was 29.7 years (15-49 years) and the mean follow-up period was 91 months (43-151 months). Mean total blood loss, external blood loss and hidden blood loss were 3543 (1494-7576), 1435 (600-3440), and 2110 ml (534-4402), respectively. Mean intraoperative blood loss and postoperative drainage were 715 (300-2000) and 713 ml (200-2950), respectively. Mean red blood cell transfusion used was 5 U (0-14). All prostheses were found to have bony ingrowth. One patient had hematoma formation in the thigh and one with a lower limb deep vein thrombosis, postoperatively. Other complications included one skin ulcer, one femur splitting fracture, and one transient neuropraxia. Intraoperative blood loss and wound drainage, in our study, were similar to that in haemophiliac patients and nonhaemophilic patients in literature. This supports the efficacy of the modified coagulation factor substitution strategy in our study.

Anterior Cruciate Ligament–Derived Stem Cells Transduced With BMP2 Accelerate Graft-Bone Integration After ACL Reconstruction

Background: Strong graft-bone integration is a prerequisite for successful graft remodeling after reconstruction of the anterior cruciate ligament (ACL) using soft tissue grafts. Novel strategies to accelerate soft tissue graft-bone integration are needed to reduce the need for bone-tendon-bone graft harvest, reduce patient convalescence, facilitate rehabilitation, and reduce total recovery time after ACL reconstruction. Hypothesis: The application of ACL-derived stem cells with enhanced expression of bone morphogenetic protein 2 (BMP2) onto soft tissue grafts in the form of cell sheets will both accelerate and improve the quality of graft-bone integration after ACL reconstruction in a rat model. Study Design: Controlled laboratory study. Methods: ACL-derived CD34+ cells were isolated from remnant human ACL tissues, virally transduced to express BMP2, and embedded within cell sheets. In a rat model of ACL injury, bilateral single-bundle ACL reconstructions were performed, in which cell sheets were wrapped around tendon autografts before reconstruction. Four groups containing a total of 48 rats (96 knees) were established (n = 12 rats; 24 knees per group): CD34+BMP2 (100%), CD34+BMP2 (25%), CD34+ (untransduced), and a control group containing no cells. Six rats from each group were euthanized 2 and 4 weeks after surgery, and each graft was harvested for immunohistochemical and histological analyses. The remaining 6 rats in each group were euthanized at 4 and 8 weeks to evaluate in situ tensile load to failure in each femur-graft-tibia complex. Results: In vitro, BMP2 transduction promoted the osteogenic differentiation of ACL-derived CD34+ cells while retaining their intrinsic multipotent capabilities. Osteoblast densities were greatest in the BMP2 (100%) and BMP2 (25%) groups. Bone tunnels in the CD34+BMP2 (100%) and CD34+BMP2 (25%) groups had the smallest cross-sectional areas according to micro–computed tomography analyses. Graft-bone integration occurred most rapidly in the CD34+BMP2 (25%) group. Tensile load to failure was significantly greater in the groups containing stem cells at 4 and 8 weeks after surgery. Tensile strength was greatest in the CD34+BMP2 (100%) group at 4 weeks, and in the CD34+BMP2 (25%) group at 8 weeks. Conclusion: ACL-derived CD34+ cells transduced with BMP2 accelerated graft-bone integration after ACL reconstruction using soft tissue autografts in a rat model, as evidenced by improved histological appearance and graft-bone interface biology along with tensile load to failure at each time point up to 8 weeks after surgery. Clinical Relevance: A primary disadvantage of using soft tissue grafts for ACL reconstruction is the prolonged time required for bony ingrowth, which delays the initiation of midsubstance graft remodeling. The lack of consistent correlation between the appearance of a “healed” ACL on postoperative magnetic resonance imaging and readiness to return to sport results in athletes being released to sport before the graft is ready to handle high-intensity loading. Therefore, it is desirable to identify strategies that accelerate graft-bone integration, which would reduce the time to biologic fixation, improve the reliability of biologic fixation, allow for accelerated rehabilitation, and potentially reduce the incidence of early graft pullout and late midsubstance failure.

Lumbar Facet Resurfacing: First Experience With the FENIX Implant.

This is a feasibility study to confirm the design, patient population, and the surgical technique for FENIX implants. This study evaluated the safety and the clinical and radiologic performance of bilaterally implanted FENIX facet resurfacing device. Facet joint osteoarthritis is responsible for up to 30% of chronic low back pain. Arthroplasty is a surgical treatment option that aims to relieve pain while maintaining or restoring motion. A total of 8 consecutive patients with proven single segmental bilateral lumbar facet joint osteoarthritis as unique pain generator received a bilateral implantation of the FENIX device. Correct device placement and mobility preservation were assessed on x-ray at 6 weeks and at 6, 12, and 24 months after implantation. Magnetic resonance imaging at 12 and 24 months after surgery assessed the bony ingrowth and computed tomography-single photon emision computed tomography was repeated at 6 months to assess evolution of the preoperative inflamed facet joints. The Oswestry disability index, pain visual analogue scale, and the need for analgesic medication were the parameters used for clinical assessment. At 24 months after surgery, 7 of the 8 patients were found to have all implants in place and all assessed parameters were found to be normal. Patients experienced significant pain relief and functionality improvement. Mobility was maintained and no Modic changes were noted, either at the index or at the adjacent levels. No "hot" lesions at the implanted levels were observed on computed tomography-single photon emision computed tomography. One of the 48 (2%) implants was found to be dislocated at 6 months follow-up. The FENIX facet resurfacing technique might be considered in the future as a surgical treatment of well-selected patients suffering from chronic low back pain because of facet joint osteoarthritis. A modification of the superior implant should provide an initial firm fixation preventing implant dislocation.

Characterization of retrieved total ankle replacement liners

Abstract This paper describes the failure analysis of two Total Ankle Replacement (TAR) devices where one device failed mechanically and the other device failed due to excessive wear and loosening. Optical and confocal imaging procedures were used to identify various failure modes. Fourier transform infrared spectroscopy was used to determine the oxidation index and crystallinity of the liners and compared them with values obtained for a shelf-aged liner which is used as a control. Regression equations were developed based on literature data to correlate oxidation index with strength of the material. 3D models of each liner were constructed to understand the damage modes at surface and sub-surface levels. Shear banding and embrittlement were observed for one of the failed liners. Both abrasive and adhesive wear were observed in the liners but they are not the dominant wear mechanisms unlike in other total joint replacement devices. Based on obtained results, the STAR™ (Scandinavian Total Ankle Replacement) device failed under higher shear and compression stresses at the bearing component resulting in fatigue-induced fracture due to higher torsion generated at the ankle joint. The Agility™ (DePuy) device showed lack of proper bony ingrowth resulting in clinical failure.

Porous tantalum biocomposites for osteochondral defect repair: A follow-up study in a sheep model.

ObjectivesWe sought to determine if a durable bilayer implant composed of trabecular metal with autologous periosteum on top would be suitable to reconstitute large osteochondral defects. This design would allow for secure implant fixation, subsequent integration and remodeling.Materials and MethodsAdult sheep were randomly assigned to one of three groups (n = 8/group): 1. trabecular metal/periosteal graft (TMPG), 2. trabecular metal (TM), 3. empty defect (ED). Cartilage and bone healing were assessed macroscopically, biochemically (type II collagen, sulfated glycosaminoglycan (sGAG) and double-stranded DNA (dsDNA) content) and histologically.ResultsAt 16 weeks post-operatively, histological scores amongst treatment groups were not statistically different (TMPG: overall 12.7, cartilage 8.6, bone 4.1; TM: overall 14.2, cartilage 9.5, bone 4.9; ED: overall 13.6, cartilage 9.1, bone 4.5). Metal scaffolds were incorporated into the surrounding bone, both in TM and TMPG. The sGAG yield was lower in the neo-cartilage regions compared with the articular cartilage (AC) controls (TMPG 20.8/AC 39.5, TM 25.6/AC 33.3, ED 32.2/AC 40.2 µg sGAG/1 mg respectively), with statistical significance being achieved for the TMPG group (p < 0.05). Hypercellularity of the neo-cartilage was found in TM and ED, as the dsDNA content was significantly higher (p < 0.05) compared with contralateral AC controls (TM 126.7/AC 71.1, ED 99.3/AC 62.8 ng dsDNA/1 mg). The highest type II collagen content was found in neo-cartilage after TM compared with TMPG and ED (TM 60%/TMPG 40%/ED 39%). Inter-treatment differences were not significant.ConclusionsTM is a highly suitable material for the reconstitution of osseous defects. TM enables excellent bony ingrowth and fast integration. However, combined with autologous periosteum, such a biocomposite failed to promote satisfactory neo-cartilage formation.Cite this article: E. H. Mrosek, H-W. Chung, J. S. Fitzsimmons, S. W. O’Driscoll, G. G. Reinholz, J. C. Schagemann. Porous tantalum biocomposites for osteochondral defect repair: A follow-up study in a sheep model. Bone Joint J 2016;5:403–411. DOI: 10.1302/2046-3758.59.BJR-2016-0070.R1.