Comparative Assessment of Primary Osteoarthritis Progression Using Conventional Histopathology, Polarized Light Microscopy, and Immunohistochemistry.

OBJECTIVE: Evaluation of collagen orientation and arrangement in articular cartilage can improve our understanding of primary osteoarthritis (OA) progression and targeted therapies. Our goal was to determine if polarized light microscopy (PLM) for collagen organization is useful in identifying early primary OA features in comparison to current standard histopathological methods. DESIGN: Osteochondral specimens from 90 total knee arthroplasty patients with relatively preserved lateral femoral condyle were scored using (1) histological-histochemical grading system (HHGS); (2) Osteoarthritis Research Society International (OARSI); (3) PLM-Changoor system for repair cartilage, scores ranging between 0 (totally disorganized cartilage) and 5 (healthy adult cartilage); and (4) new PLM system for primary OA cartilage with superficial zone PLM (PLM-SZ) and deep zone PLM (PLM-DZ) scores, each ranging between 0 (healthy adult SZ and DZ collagen organization) and 4 (total loss of collagen organization). Serial sections were stained for collagen I and II antibodies. Spearman correlation coefficients (rs) were determined. RESULTS: The associations between: (1) PLM-Changoor and HHGS or OARSI were weak (rs = -0.36) or moderate (rs = -0.56); (2) PLM-SZ and HHGS or OARSI were moderate (rs = 0.46 or rs = 0.53); and (3) PLM-DZ and HHGS or OARSI were poor (rs = 0.31 or rs = 0.21), respectively. Specimens exhibiting early and mild OA (HHGS < 5 and OARSI < 8.6) had PLM-SZ and PLM-DZ scores between 0 and 4 and between 0 and 3, respectively, and indicated new histopathological features not currently considered by HHGS/OARSI. CONCLUSIONS: PLM was effective at identifying early SZ and DZ collagen alterations that were not evident in the traditional scoring systems. Incorporating PLM scores and/or additional HHGS/OARSI features can help improve characterization of early primary OA cartilage.

Classification systems for platelet-rich plasma.

There is good scientific rationale to support the use of growth factors to promote musculoskeletal tissue regeneration. However, the clinical effectiveness of platelet-rich plasma (PRP) and other blood-derived products has yet to be proven. Characterization and reporting of PRP preparation protocols utilized in clinical trials for the treatment of musculoskeletal disease is highly inconsistent, and the majority of studies do not provide sufficient information to allow the protocols to be reproduced. Furthermore, the reporting of blood-derived products in orthopaedics is limited by the multiple PRP classification systems available, which makes comparison of results between studies challenging. Several attempts have been made to characterize and classify PRP; however, no consensus has been reached, and there is lack of a comprehensive and validated classification. In this annotation, we outline existing systems used to classify preparations of PRP, highlighting their advantages and limitations. There remains a need for standardized universal nomenclature to describe biological therapies, as well as a comprehensive and reproducible classification system for autologous blood-derived products. Cite this article: Bone Joint J 2019;101-B:891-896.

Donor-matched comparison of chondrogenic progenitors resident in human infrapatellar fat pad, synovium, and periosteum - implications for cartilage repair.

Purpose: There is a clinical need to better characterize tissue sources being used for stem cell therapies. This study focuses on comparison of cells and connective tissue progenitors (CTPs) derived from native human infrapatellar fatpad (IPFP), synovium (SYN), and periosteum (PERI). Materials and Methods: IPFP, SYN, PERI were harvested from twenty-eight patients undergoing arthroplasty. CTPs were quantitatively characterized using automated colony-forming-unit assay to compare total nucleated cell concentration-[Cell], cells/mg; prevalence-(PCTP), CTPs/million nucleated cells; CTP concentration-[CTP], CTPs/mg; proliferation and differentiation potential; and correlate outcomes with patient's age and gender. Results: [Cell] did not differ between IPFP, SYN, and PERI. PCTP was influenced by age and gender: patients >60 years, IPFP and SYN had higher PCTP than PERI (p < 0.001) and females had higher PCTP in IPFP (p < 0.001) and SYN (p = 0.001) than PERI. [CTP] was influenced by age: patients <50 years, SYN (p = 0.0165) and PERI (p < 0.001) had higher [CTP] than IPFP; patients between 60 and 69 years, SYN (p < 0.001) had higher [CTP] than PERI; patients >70 years, IPFP (p = 0.006) had higher [CTP] than PERI. In patients >60 years, proliferation potential of CTPs differed significantly (SYN>IPFP>PERI); however, differentiation potentials were comparable between all three tissue sources. Conclusion: SYN and IPFP may serve as a preferred tissue source for patients >60 years, and PERI along with SYN and IPFP may serve as a preferred tissue source for patients <60 years for cartilage repair. However, the heterogeneity among the CTPs in any given tissue source suggests performance-based selection might be useful to optimize cell-sourcing strategies to improve efficacy of cellular therapies for cartilage repair.

Primary Cells Isolated from Human Knee Cartilage Reveal Decreased Prevalence of Progenitor Cells but Comparable Biological Potential During Osteoarthritic Disease Progression.

BACKGROUND: Current decisions on cellular therapies for osteoarthritis are based primarily on clinical experience or on assumptions about preferred cell sourcing. They have not been informed by rigorous standardized measurements of the chondrogenic connective-tissue progenitors (CTP-Cs) or their intrinsic diversity of chondrogenic potential. The goal of this study was to quantitatively define the CTP-Cs resident in cartilage of different grades of osteoarthritis and to compare their concentration, prevalence, and biological potential. METHODS: Twenty-three patients who had varus malalignment of the knee and were scheduled to undergo elective total knee arthroplasty for idiopathic osteoarthritis and who had grade 1-2 osteoarthritis on the lateral femoral condyle and grade 3-4 osteoarthritis on the medial femoral condyle were recruited for study of the cartilage removed during surgery. CTP-Cs were assayed by a standardized colony-forming-unit assay using automated image-analysis software based on ASTM standard test method F2944-12. RESULTS: Cell concentration was significantly greater (p < 0.001) in grade 3-4 cartilage than in grade 1-2 cartilage. The prevalence of CTP-Cs varied widely, but it trended lower in grade 3-4 cartilage than in grade 1-2 samples (p = 0.078). The biological performance of CTP-Cs from grade 1-2 and grade 3-4 cartilage was comparable. Increased cell concentration was a significant predictor of decreased CTP-C prevalence (p = 0.002). CONCLUSIONS: Although grade 3-4 cartilage showed fewer CTP-Cs than grade 1-2 cartilage, the range of biological performance was comparable, which suggests that either may be used as a source for potent CTP-Cs. However, the biological reason for the heterogeneity of CTP-Cs in cartilage and the biological implications of that heterogeneity are not well understood and require further study. CLINICAL RELEVANCE: In order to improve the efficacy of cartilage cell therapy procedures, it is key to characterize the quality and quantity of the cells and progenitors being administered. Additionally, understanding the heterogeneity in order to select appropriate subsets of populations will improve the rigor of decisions concerning cell sourcing and targeting for pharmacological and cellular therapies.

Histopathological assessment of primary osteoarthritic knees in large patient cohort reveal the possibility of several potential patterns of osteoarthritis initiation.

OBJECTIVE: The two main objectives of the study include (1) Test the hypothesis that the lateral femoral condyle (LFC) in patients with primary OA and varus knees undergoing total knee arthroplasty (TKA) can be used as a model to better characterize varying histological features of human OA, (2) Correlate characteristic OA features using the established histopathological scoring systems (HHGS and OARSI) to understand potential histopathological patterns of OA initiation. DESIGN: Two osteochondral specimens (4×4×8mm) were collected from fifty patient's LFC at the time of TKA (total 100 specimens), who presented preserved lateral knee compartment with joint space width>2mm. Three independent readers graded the sections on three different occasions using HHGS and OARSI systems. The correlation between individual parameters of the two scoring systems and their inter- and intra-reader variability, reliability and reproducibility were estimated. RESULTS: All samples in this cohort showed abnormal histopathological features. Total histopathological scores of the LFC ranged from HHGS median=4.6 (range=0 to 11), and OARSI median=5.2 (range=0 to 19.5). The four individual sub-items of HHGS scoring system (structure, cells, safraninO staining, tidemark) were weakly correlated, with the correlation between structure and cellularity being the strongest (r=0.40). Both the scoring systems had similar repeatability and reproducibility coefficients of<21%. CONCLUSIONS: OA changes in the LFC are not confined to any one region, and maybe seen in different regions of cartilage, tidemark, subchondral bone, and/or the marrow space vascularity. These variations may point to the possibility of several potential patterns of initiation in OA.

Evaluation of rhBMP-2/collagen/TCP-HA bone graft with and without bone marrow cells in the canine femoral multi defect model.

Recombinant human bone morphogenetic protein-2, when applied to an absorbable type 1 bovine collagen sponge (rhBMP-2/ACS) is an effective therapy in many bone grafting settings. Bone marrow aspirate (BMA) has also been used as a source of transplantable osteogenic connective tissue progenitors. This study was designed to characterize the performance of a scaffold comprising rhBMP-2/ACS in which the sponge wraps around tri-calcium phosphate hydroxyapatite granules (rhBMP-2/ACS/TCP-HA) and to test the hypothesis that addition of BMA will improve the performance of this construct in the Canine Femoral Multi Defect Model. In each subject, two sites were grafted with rhBMP-2/ACS/TCP-HA scaffold loaded with BMA clot and two other sites with rhBMP-2/ACS/TCP-HA scaffold loaded with wound blood (WB). After correction for unresorbed TCP-HA granules, sites grafted with rhBMP-2/ACS/TCP-HA+BMA and rhBMP-2/ACS/TCP-HA+WB were similar, with mean percent bone volumes of 10.9 %±1.2 and 11.2 %±1.2, respectively. No differences were seen in quantitative histomorphometry. While bone formation using both constructs was robust, this study did not support the hypothesis that the addition of unprocessed bone marrow aspirate clot improved bone regeneration in a site engrafted with rhBMP-2/ACS/TCP-HA+BMA. In contrast to prior studies using this model, new bone formation was greater at the center of the defect where TCP-HA was distributed. This finding suggests a potential synergy between rhBMP-2 and the centrally placed ceramic and cellular components of the graft construct. Further optimization may also require more uniform distribution of TCP-HA, alternative cell delivery strategies, and a more rigorous large animal segmental defect model.

Age- and gender-related changes in the cellularity of human bone marrow and the prevalence of osteoblastic progenitors.

Bone marrow harvested by aspiration contains connective tissue progenitor cells which can be induced to express a bone phenotype in vitro. The number of osteoblastic progenitors can be estimated by counting the colony-forming units which express alkaline phosphatase (CFU-APs). This study was undertaken to test the hypothesis that human aging is associated with a significant change in the number or prevalence of osteoblastic progenitors in the bone marrow. Four 2-ml bone marrow aspirates were harvested bilaterally from the anterior iliac crest of 57 patients, 31 men (age 15-83) and 26 women (age 13-79). A mean of 64 million nucleated cells was harvested per aspirate. The mean prevalence of CFU-APs was found to be 55 per million nucleated cells. These data revealed a significant age-related decline in the number of nucleated cells harvested per aspirate for both men and women (P = 0.002). The number of CFU-APs harvested per aspirate also decreased significantly with age for women (P = 0.02), but not for men (P = 0.3). These findings are relevant to the harvest of bone marrow derived connective tissue progenitors for bone grafting and other tissue engineering applications, and may also be relevant to the pathophysiology of age-related bone loss and post-menopausal osteoporosis.

Osteogenic protein-1 (bone morphogenetic protein-7) in the treatment of tibial nonunions.

BACKGROUND: The role of bone morphogenetic proteins (BMPs) in osseous repair has been demonstrated in numerous animal models. Recombinant human osteogenic protein-1 (rhOP-1 or BMP-7) has now been produced and was evaluated in a clinical trial conducted under a Food and Drug Administration approved Investigational Device Exemption to establish both the safety and efficacy of this BMP in the treatment of tibial nonunions. The study also compared the clinical and radiographic results with this osteogenic molecule and those achieved with fresh autogenous bone. MATERIALS AND METHODS: One hundred and twenty-two patients (with 124 tibial nonunions) were enrolled in a controlled, prospective, randomized, partially blinded, multi-center clinical trial between February, 1992, and August, 1996, and were followed at frequent intervals over 24 months. Each patient was treated by insertion of an intramedullary rod, accompanied by rhOP-1 in a type I collagen carrier or by fresh bone autograft. Assessment criteria included the severity of pain at the fracture site, the ability to walk with full weight-bearing, the need for surgical re-treatment of the nonunion during the course of this study, plain radiographic evaluation of healing, and physician satisfaction with the clinical course. In addition, adverse events were recorded, and sera were screened for antibodies to OP-1 and type-I collagen at each outpatient visit. RESULTS: At 9 months following the operative procedures (the primary end-point of this study), 81% of the OP-1-treated nonunions (n = 63) and 85% of those receiving autogenous bone (n = 61) were judged by clinical criteria to have been treated successfully (p = 0.524). By radiographic criteria, at this same time point, 75% of those in the OP-1-treated group and 84% of the autograft-treated patients had healed fractures (p = 0.218). These clinical results continued at similar levels of success throughout 2 years of observation, and there was no statistically significant difference in outcome between the two groups of patients at this point (p = 0.939). All patients experienced adverse events. Forty-four percent of patients in each treatment group had serious events, none of which were related to their bone grafts. More than 20% of patients treated with autografts had chronic donor site pain following the procedure. CONCLUSIONS: rhOP-1 (BMP-7), implanted with a type I collagen carrier, was a safe and effective treatment for tibial nonunions. This molecule provided clinical and radiographic results comparable with those achieved with bone autograft, without donor site morbidity.

Bone cells and matrices in orthopedic tissue engineering.

The ability to harvest and manipulate osteogenic cells gives clinicians the opportunity to harness capacity of these cells for targeted regeneration and repair of skeletal tissues. Further opportunities to optimize use of cells exist in the ability to design specialized matrices that act as conductive scaffolds. Realization of the full potential of engineered matrix materials and cell-matrix composites can provide new solutions to many clinical problems in skeletal reconstruction.

Influence of stability and mechanical properties of a spinal fixation device on production of wear debris particles in vivo.

A prospective and quantitative animal study was performed to evaluate the production of wear particles from a spinal fixation device, and to test the hypothesis that the concentration of wear debris particles adjacent to spinal fixation hardware is correlated with the stiffness of the spinal fusion construct and local bone formation at the fusion site. An established canine segmental spinal fusion model with three interfacet fusions was used in this study. Several bone substitute materials were grafted to the area of the interfacet fusion. Internal fixation was performed on both sides of the spinous processes at each site using a stainless steel plate system in 19 dogs. After 12 weeks, spinal segments were excised, then 3-dimensional computerized tomography was used to measure bone volume and bone area of the individual fusion sites. The stiffness of each segment was tested using a servohydraulic materials testing machine. Biopsies were obtained from the soft tissues immediately around the plate system, and wear particles were collected and characterized using an electrical resistance particle analyzer, light and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX). Biopsies from para-spinal tissue from adjacent, unoperated spinal levels served as negative controls. Histologically, 24 of 57 specimens (42.1%) showed only fibrous tissue with no recognizable macrophages, inflammation, or debris. Fourteen of 57 specimens (24.6%), however, contained many particles that were composed of Fe, Cr, and Ni, corresponding to elements found in the fixation hardware. Another 19 specimens showed only occasional particles. The mean concentration of particles from the tissue around the plate system was 2.8 x 10(9) per gram dry tissue weight, compared to 0.5 x 10(9) particles per gram for controls (p < 0.05). Statistical analyses showed significant inverse correlation between the log particle number and stiffness (r = -0.41, p < 0.01), bone volume (r = -0.28, p < 0.05), and bone area (r = -0.34, p < 0. 05) of the corresponding segments. The concentration of particles in the tissue showed a significant inverse correlation with stiffness, bone volume, and bone area of the fusion constructs.

Bone graft materials. An overview of the basic science.

Autograft, allograft, and synthetic bone graft substitute materials play an important role in reconstructive orthopaedic surgery, and understanding the biologic effects of these materials is necessary for optimum use. Although vascularized and cancellous autograft show optimum skeletal incorporation, host morbidity limits autograft availability. Experimental studies have confirmed an immune response to allograft bone, but the clinical significance of this response in humans still is unclear. Small amounts of cancellous allograft in humans usually are remodeled completely; large allografts become incorporated by limited, surface intramembranous bone formation suggesting that these graft are primarily osteoconductive. Several synthetic skeletal substitute materials also are osteoconductive, and may show remodeling characteristics similar to allograft. Demineralized bone matrix and some isolated or synthetic proteins can induce endochondral bone formation, and therefore are osteoinductive. The extent and distribution of remodeling of bone graft materials are influenced by many factors, including the quality of the host site and the local mechanical environment (strain). Graft materials are likely to become more specialized for use in specific clinical applications, and composite preparations may soon provide bone graft materials with efficacy that equals or exceeds that of autogenous grafts.

Prosthetic knee replacement after resection of a malignant tumor of the distal part of the femur. Medium to long-term results.

We evaluated the medium to long-term results of treatment with a custom prosthetic knee replacement after wide resection of a primary malignant tumor of the distal part of the femur in forty consecutive patients. The duration of follow-up ranged from five to seventeen years (median, eight years). At the time of the latest follow-up, thirty-five (88 per cent) of the forty patients were free of disease and five (13 per cent) were alive with metastatic disease. No local recurrence was observed. Twenty early complications occurred in eighteen patients (45 per cent). Aseptic loosening of the femoral component, which necessitated a revision in eleven patients at an average of fifty-one months, was the most frequent mode of failure. The rate of prosthetic survival, as estimated with use of the Kaplan-Meier method, was 85, 67, and 48 per cent at three, five, and ten years. Univariate analysis demonstrated that the rate of prosthetic survival was significantly worse for male patients, for those in whom at least 40 per cent of the femur had been resected, for those who had had total resection of the quadriceps muscles or subtotal resection (preservation of only the rectus femoris muscle), and for those in whom a straight femoral stem had been used (p < 0.05 for all comparisons). Multivariate analysis showed that the independent adverse prognostic factors for prosthetic survival were male gender, resection of at least 40 per cent of the femur, and fixation of the femoral stem with cement. The rate of limb salvage was calculated, with use of the Kaplan-Meier method, to be 93 per cent at three years and 90 per cent at five and ten years. At the latest follow-up examination, the functional scores according to the classification system of the Musculoskeletal Tumor Society ranged from 14 to 29 points; the mean was 24 points, which represents function that is 80 per cent that of normal. The mean scores in the categories of walking supports and gait were better for the patients in whom the quadriceps muscles had been preserved than for those who had had total or subtotal resection of those muscles. Although advances in imaging and local therapy narrow the indications for an extra-articular resection of a tumor, the implant that was used in the present study continues to be used in approximately 15 per cent of patients who have a fracture or an intra-articular extension of the tumor that necessitates extensive extra-articular resection.

Aspiration to obtain osteoblast progenitor cells from human bone marrow: the influence of aspiration volume.

UNLABELLED: Bone marrow contains osteoblast progenitor cells that can be obtained with aspiration and appear to arise from a population of pluripotential connective-tissue stem cells. When cultured in vitro under conditions that promote an osteoblastic phenotype, osteoblast progenitor cells proliferate to form colonies of cells that express alkaline phosphatase and, subsequently, a mature osteoblastic phenotype. We evaluated the number of nucleated cells in bone-marrow samples obtained with aspiration from the anterior iliac crest of thirty-two patients without systemic disease. There were nineteen male patients and thirteen female patients; the mean age was forty-one years (range, fourteen to seventy-seven years). The prevalence and concentration of the osteoblast progenitor cells also were determined, by placing the bone-marrow-derived cells into tissue-culture medium and counting the number of alkaline phosphatase-positive colony-forming units. In order to assess the effect of aspiration volume, two sequential experiments were performed. In the first experiment, aspiration volumes of one and two milliliters were compared. In the second experiment, aspiration volumes of two and four milliliters were compared. The mean prevalence of alkaline phosphatase-positive colony-forming units in the bone-marrow samples was thirty-six per one million nucleated cells (95 per cent confidence interval, 28 to 47); a mean of 2400 alkaline phosphatase-positive colony-forming units was obtained from a two-milliliter aspirate. There was a significant difference among the patients with respect to the number of alkaline phosphatase-positive colony-forming units in these bone-marrow samples (p < 0.001). Seventy per cent of this variation in the prevalence was due to variation among patients, and 20 per cent was due to variation among aspirates. The number of alkaline phosphatase-positive colony-forming units in the aspirate increased as the aspiration volume increased. However, contamination by peripheral blood also increased as the aspiration volume increased. An increase in the aspiration volume from one to four milliliters caused a decrease of approximately 50 per cent in the final concentration of alkaline phosphatase-positive colony-forming units in an average sample. CLINICAL RELEVANCE: On the basis of these data, we recommend that, when bone marrow is obtained with aspiration for use as a bone graft, the volume of aspiration from any one site should not be greater than two milliliters. A larger volume decreases the concentration of osteoblast progenitor cells because of dilution of the bone-marrow sample with peripheral blood. We estimate that four one-milliliter aspirates will provide almost twice the number of alkaline phosphatase-positive colony-forming units as will one four-milliliter aspirate. In addition, these data confirm that humans differ significantly from one another with respect to the cellularity of bone marrow and the prevalence of osteoblast progenitor cells. Additional studies are necessary to determine if the number or prevalence of alkaline phosphatase-positive colony-forming units in bone marrow is a determining factor in the efficacy of an autogenous bone or bone-marrow graft and to ascertain how the number and function of alkaline phosphatase-positive colony-forming units may change as a function of factors such as age, menopausal status, and selected diseases.

Characterization of human bone marrow stromal cells with respect to osteoblastic differentiation.

Human bone marrow was harvested by means of iliac crest aspiration and cultured under conditions that promote an osteoblastic phenotype. Human bone marrow aspirates from 30 normal subjects, ages 8-80 years, with no systemic illness, yielded a mean of 92 +/- 65 x 10(6) nucleated cells per 2 ml of aspirate. The prevalence of potential osteoblastic progenitors was estimated by counting the number of alkaline phosphatase-positive colonies. This assay demonstrated a mean of 43 +/- 28 alkaline phosphatase-positive colonies per 10(6) nucleated cells, which was about one per 23,000 nucleated cells. The prevalence of these colonies was positively correlated with the concentration of nucleated cells in the original aspirate (p = 0.014) and was negatively correlated with donor age (p = 0.020). The population of alkaline phosphatase-positive colonies in this model sequentially exhibited markers of the osteoblastic phenotype; essentially all colonies (more than 99%) stained positively for alkaline phosphatase on day 9. Matrix mineralization, which was associated with the synthesis of bone sialoprotein, was demonstrated on day 17 with alizarin red S staining. On day 45, cells that were stimulated with 1,25-dihydroxyvitamin D3 synthesized and secreted osteocalcin at concentrations consistent with known osteoblastic cell lines. This model provides a useful method for the assay of progenitors of connective tissue from human subjects, examination of the effects of aging and selected disease states on this progenitor population, and investigation into the regulation of human osteoblastic differentiation.

Evaluation of collagen ceramic composite graft materials in a spinal fusion model.

Autogenous bone graft is highly effective in inducing a bone healing response in most clinical settings. However, significant morbidity can occur related to the harvest of an autograft. This makes the development of synthetic or purified nontissue bone grafting materials highly desirable. Both purified bovine Type I collagen and calcium phosphate ceramics have been proposed as promising osteoconductive bone graft substitute materials. One collagen ceramic composite, Collagraft, is approved for use in acute long bone fractures. This study evaluated composites of purified bovine Type I fibrillar collagen and a granular biphasic hydroxyapatite/tricalcium phosphate ceramic in the posterior segmental canine spinal fusion model. Materials were compared based on union score and mechanical testing in 3 separate fusion sites (L1-2, L3-4, L5-6). All composites were found to be inferior in union score to an equal volume of autogenous cancellous bone. In addition, the combination of the collagen ceramic composite with autogenous cancellous bone graft reduced the effectiveness of the autogenous bone graft significantly. These data should be a caution to the clinician who may consider use of collagen ceramic composites similar to Collagraft for spinal fusion applications.

A custom distal femoral prosthesis for reconstruction of large defects following wide excision for sarcoma: results and prognostic factors.

Between 1979 and 1986, 37 patients with sarcoma of the distal femur underwent limb salvage using a custom prosthetic knee replacement. Thirteen (35%) had early complications. Fourteen (38%) had late complications, which consisted of 6 aseptic femoral loosenings, 1 aseptic tibial loosening, 2 tibial fractures, 2 contractures, 1 femoral fracture, 1 prosthetic fracture, and 1 septic loosening. By 1988, nine patients died. Thirteen prostheses failed in 12 patients, resulting in 9 revisions, 2 above-knee amputations, and 2 Van Nes rotationplasties. The 2- and 5-year prosthetic survival rates were 82% and 57%, respectively. Twenty-two of the 26 survivors (85%) had successful limb salvage. Preventable factors were implicated in the loosening of six femoral components and in one femoral fracture. The mean Hospital for Special Surgery Knee Score was 69 (range: 62 to 86).

Evaluation of human bone morphogenetic protein 2 in a canine spinal fusion model.

The efficacy of purified recombinant human bone morphogenetic protein-2 (rhBMP-2) delivered in a porous biodegradable copolymer, poly [D,L (lactide--coglycide)] (PLGA) was evaluated using a canine posterior segmental spinal fusion model. rhBMP-2/PLGA was compared to autogenous cancellous bone and to PLGA alone. Thirty three fusion sites in 11 beagle dogs were evaluated at 12 weeks for union and mechanical strength. Union score and mechanical testing showed no difference between autogenous cancellous bone and rhBMP-2/PLGA. Union scores for autogenous cancellous bone and rhBMP-2/PLGA sites were superior to those with PLGA alone (p = 0.001 and p = 0.0007, respectively). These findings suggest that synthetic bone graft substitute materials delivering purified rhBMP-2 may be suitable for posterior spinal fusions. The use of such materials may provide efficacy equivalent to autogenous cancellous bone and avoid the morbidity associated with the harvest of autogenous graft.

Evaluation of bone-grafting materials in a new canine segmental spinal fusion model.

This paper describes a new canine segmental spinal fusion model for the comparison of bone-grafting materials. The test sites in the model are three separate posterior interfacet-interlaminar fusion sites in the lumbar spine (L1-2, L3-4, and L5-6). The outcome was assessed by scoring of the fusion sites for union and by mechanical testing of fused segments. The results from two experiments are presented. Autogenous cancellous bone was the most effective material tested and had a statistically superior score for union compared with all other materials (p = 0.01). The results with an osteoconductive matrix of collagen and ceramic alone were no better than those with the controls (no graft). However, addition of an extract of matrix-derived proteins (15-30 kDa) to the collagen-ceramic carrier appeared to improve the score for union. The inclusion of nonresorbed ceramic granules had no evident effect on the mechanical properties of fusions, with a comparable score for union. This model appears to be a sensitive and efficient method for the comparison of graft materials. Advantages over previously described models are discussed.