Hydroxyapatite in revision of total hip replacements with massive acetabular defects: 4- to 10-year clinical results

(Bio)manufactured Solutions for Treatment of Bone Defects with Emphasis on US-FDA Regulatory Science Perspective

Bone defects, with second highest demand for surgeries around the globe, may lead to serious health issues and negatively influence patient lives. The advances in biomedical engineering and sciences have led to the development of several creative solutions for bone defect treatment. This review provides a brief summary of bone graft materials, an organized overview of top-down and bottom-up (bio)manufacturing approaches, plus a critical comparison between advantages and limitations of each method. We specifically discuss additive manufacturing techniques and their operation mechanisms in detail. Next, we review the hybrid methods and promising future directions for bone grafting, while giving a comprehensive US-FDA regulatory science perspective, biocompatibility concepts and assessments, and clinical considerations to translate a technology from a research laboratory to the market. The topics covered in this review could potentially fuel future research efforts in bone tissue engineering, and perhaps could also provide novel insights for other tissue engineering applications.

Minimum 10 years clinical and radiological outcomes of acetabular revisions of total hip arthroplasties with tricalcium phosphate/hydroxyapatite bone graft substitute

BACKGROUND

Aseptic loosening is the most frequent indication for revision of total hip arthroplasty. Revision arthroplasty of acetabular component is a challenge for every surgeon because they have to simultaneously deal with the reconstruction of bone defects, adequate implant geometry and stable fixation. Allografts are the most frequently used materials in reconstruction of bone loss during revision surgeries. Because of an increasing number of revision hip arthroplasties and poor availability of allografts, we decided to use bone graft substitutes in acetabular revisions.

METHODS

Between September 2005 and January 2010, 44 revision arthroplasties in 43 patients were performed with the use of bone graft substitutes for acetabular defect reconstruction in revision of total hip arthroplasty. Acetabular bone defects were classified according to Paprosky. Seventeen hips were classified as IIA, 3 hips IIB, 3 hips IIC, 10 hips IIIA and 11 hips IIIB. Acetabular bone defects were reconstructed with tricalcium phosphate/hydroxyapatite bone graft substitute - BoneSave. Clinical and radiological examination was performed after 3 months, 1 year and then annually. Harris hip score was used for clinical evaluation. Survival analysis was performed with Kaplan-Meier method with aseptic loosening as the definition of endpoint.

RESULTS

The average follow-up period is 12 (range from 10 to 15) years. During the follow-up, three patients died after 24 months because of causes not related to surgery. None of the patients was lost to follow-up. The evaluation of clinical results revealed an increase in pre-operative HHS from average 38.3 (range 25 to 55) points to average 86.3 (range 45 to 95) points at the most recent follow-up. Radiographic evaluation showed the migration of one revision cage 12 months after surgery. Revision arthroplasty performed after 14 months revealed the partial incorporation of bone graft substitute. There were not any cases of loosening of revision acetabular cup at the most recent follow up examination in the remaining 39 patients. Bone graft substitute was not absorbed in all of these patients. The survival after 10 years amounted to 97.56%.

CONCLUSION

Bone graft substitute Bone Save may be suitable for acetabular revision surgery, however preoperative bone defect is critical for success and determining of a surgical technique, so this is multifactorial in this challenge surgery.

Synthetic Bone Grafting in Aseptic Loosening of Acetabular Cup: Good Clinical and Radiological Outcomes in Contained Bone Defects at Medium-Term Follow Up

Restoring bone loss is one of the major challenges when facing hip revision surgery. To eliminate the risk of disease transmission and antigenicity of allografts and donor-morbidity of autografts, the use of synthetic bioceramics has become popular in the last decade. Our study investigated the effectiveness of impaction bone grafting (IBG) of contained acetabular defects (Paprosky 2 and 3a) using a porous ceramic-based hydroxyapatite bone substitute (Engipore, provided by Finceramica Faenza S.p.A., Faenza, Italy) mixed with a low percentage of autologous bone (obtained from reaming when available). We retrospectively assessed 36 patients who underwent acetabular revision using IBG using a porous ceramic-based hydroxyapatite bone substitute with cementless implants with a mean follow-up of 4.4 years. We evaluated, at regular intervals, patients clinically (using the Hip Harris Score and Oxford Score) and radiologically to evaluate the rate of incorporation of the graft, the presence of radiolucent lines or migrations of the cup. Clinical scores significantly improved (WOMAC improved from 49.7–67.30, and the HSS from 56–89). The rate of implants’ survival was 100% at our medium follow-up (4.4 years). We reported five cases of minor migration of the cup, and radiolucent lines were visible in seven patients at the last-follow up. The graft was well-incorporated in all patients. The results presented in this study suggest the HA bone substitute is an effective and safe bone graft when facing hip revision surgery; thus, longer follow-up studies are required.

Hydroxyapatite calvaria graft repair in experimental diabetes mellitus in rats

Among the systemic conditions that impact negatively on the planning and execution of surgical procedures, diabetes mellitus (DM) is the primary clinical condition responsible for complications. This study investigated bone formation in critical defects surgically filled with hydroxyapatite (HA) in diabetic rats. A descriptive, randomized sample and blinded analysis were conducted to test bone regeneration in critical bone defects surgically performed in rat calvaria. Twenty adult male Wistar rats were randomly divided into two groups: control, normoglycemic animals (CG); and test, streptozotocin-induced hyperglycemic animals (TG). A circular bone defect was filled with HA and maintained subperiosteally. The clinical parameters evaluated were body weight, water and food intake, fasting blood glucose, and bone alkaline phosphatase. Bone-grafted area samples were submitted for histomorphometric and stereological analysis. The TG showed a significantly higher rate of new bone formation compared with the CG, sacrificed 15 days after surgery (p < 0.0001). However, at the end of the study, there was no significant difference in the amount of bone formed between groups (p = 0.077). In parallel, with the increase in osteoblastic activity observed in the TG by the measurement of systemic bone alkaline phosphatase (p = 0.016), the analysis of polarized microscopy and stereology demonstrated a lower level collagen maturation and mineralization in the TG. Quantitatively, the TG showed significantly better results for bone gain in the first 15 days. Qualitative assessments, however, showed fewer collagen fibers and bone maturation in the TG compared with the CG both at 15 and 45 days. Therefore, the postoperative evaluation of bone grafts with HA in hyperglycemic situations should consider the systemic and local effects of this condition on the quality of bone repair, rather than identifying the filling or stability of the grafted area after the process. We conclude that clinically detectable bone repair in diabetic animal models submitted to hydroxyapatite grafts may be satisfactory in the early stages. However, hyperglycemia compromises the quality of the newly formed bone and the collagen cross-linking involved in this process.

Bone grafts and biomaterials substitutes for bone defect repair: A review

Bone grafts have been predominated used to treat bone defects, delayed union or non-union, and spinal fusion in orthopaedic clinically for a period of time, despite the emergency of synthetic bone graft substitutes. Nevertheless, the integration of allogeneic grafts and synthetic substitutes with host bone was found jeopardized in long-term follow-up studies. Hence, the enhancement of osteointegration of these grafts and substitutes with host bone is considerably important. To address this problem, addition of various growth factors, such as bone morphogenetic proteins (BMPs), parathyroid hormone (PTH) and platelet rich plasma (PRP), into structural allografts and synthetic substitutes have been considered. Although clinical applications of these factors have exhibited good bone formation, their further application was limited due to high cost and potential adverse side effects. Alternatively, bioinorganic ions such as magnesium, strontium and zinc are considered as alternative of osteogenic biological factors. Hence, this paper aims to review the currently available bone grafts and bone substitutes as well as the biological and bio-inorganic factors for the treatments of bone defect.

Risk factors for failure of revision total hip arthroplasty using a Kerboull-type acetabular reinforcement device

Background

The present study aimed to identify the risk factors associated with revision total hip arthroplasty (THA) failure using a Kerboull-type (KT) plate.

Methods

We analyzed 77 revision THAs using cemented acetabular components with a KT plate for aseptic loosening between May 2000 and March 2012. We examined the association of bone graft type, acetabular bone defects, age at the time of surgery, preoperative Japanese Orthopaedic Association (JOA) score, postoperative JOA hip score, and body mass index, with radiographic failure as the outcome.

Results

The 7.4-year radiographic failure survival rate was 81.6%. The survival rate was significantly different between the beta-tricalcium phosphate (β-TCP) group and the bulk allograft group (p = 0.019). The survival curves were also significantly different between the β-TCP group and bulk allograft group (p = 0.036). American Academy of Orthopaedic Surgeons type IV was significantly associated with radiographic failure (odds ratio [OR]: 15.5, 95% confidence interval [CI]: 1.4–175.4; p = 0.032).

Conclusions

The midterm outcomes of revision THA indicate that type of bone graft and bone defect size may affect radiographic survival rate when using a KT plate.

Effects of Laser Power Level on Microstructural Properties and Phase Composition of Laser-Clad Fluorapatite/Zirconia Composite Coatings on Ti6Al4V Substrates

Hydroxyapatite (HA) is one of the most commonly used materials for the coating of bioceramic titanium (Ti) alloys. However, HA has poor mechanical properties and a low bonding strength. Accordingly, the present study replaces HA with a composite coating material consisting of fluorapatite (FA) and 20 wt % yttria (3 mol %) stabilized zirconia (ZrO₂, 3Y-TZP). The FA/ZrO₂ coatings are deposited on Ti6Al4V substrates using a Nd:YAG laser cladding system with laser powers and travel speeds of 400 W/200 mm/min, 800 W/400 mm/min, and 1200 W/600 mm/min, respectively. The experimental results show that a significant inter-diffusion of the alloying elements occurs between the coating layer (CL) and the transition layer (TL). Consequently, a strong metallurgical bond is formed between them. During the cladding process, the ZrO₂ is completely decomposed, while the FA is partially decomposed. As a result, the CLs of all the specimens consist mainly of FA, Ca₄(PO₄)₂O (TTCP), CaF₂, CaZrO₃, CaTiO₃ and monoclinic phase ZrO₂ (m-ZrO₂), together with a small amount of θ-Al₂O₃. As the laser power is increased, CaO, CaCO₃ and trace amounts of tetragonal phase ZrO₂ (t-ZrO₂) also appear. As the laser power increases from 400 to 800 W, the CL hardness also increases as a result of microstructural refinement and densification. However, at the highest laser power of 1200 W, the CL hardness reduces significantly due to the formation of large amounts of relatively soft CaO and CaCO₃ phase.

Long-Term Outcome of Acetabular Reconstruction Using a Kerboull-Type Acetabular Reinforcement Device with Hydroxyapetite Granule and Structural Autograft for AAOS type II and III Acetabular Defects

We evaluated the clinical results of the reconstruction of acetabular bone deficiency using hydroxyapatite (HA) granules and structural autografts supported by a Kerboull-type acetabular reinforcement device at a minimum of 10 years follow-up. Between 1993 and 2003, 40 consecutive THA revisions were performed in 37 patients with a mean age of 66.4 years. The mean follow-up period was 12.8 years. Radiologically, 5 hips failed, of which 2 were revised. The survival rate of the acetabular component at 10 years was 100% in type II defects and 94.9% in the type III defects, using acetabular revision for loosening as the end point. Acetabular reconstruction with HA granules, structural autografts and a Kerboull-type acetabular reinforcement device provided satisfactory clinical and radiological results at 12.8 years postoperatively.

Phosphocalcium ceramics are efficient in the management of severe acetabular loss in revision hip arthroplasties. A 22 cases long-term follow-up study

Management of bone loss in revision total hip replacement remains a challenge. To eliminate any immunological or infectious problem and so to try to improve the long-term results obtained with allografts, the authors used synthetic ceramics as bone substitutes since 1995. We reviewed 13 of the patients of our study, we previously reported in 2005 (Schwartz and Bordei in Eur J Orthop Surg Traumatol 15: 191 2005), which was a prospective cohort of thirty-two cases of acetabular revision reconstruction, with a mean follow-up of 14.4 years yet (from 9 to 16 years). Clinical results were assessed according to Oxford scale and Postel and Merle d'Aubigne (PMA) scale. Since 2005, no specific complications were noted. The average PMA functional hip score was 14.9 (vs. 9.2 before revision) at follow-up over 9 years. Nine patients still alive in 2013 were seen again by a surgeon, which was not the operator, with a mean follow-up of 15.3 years: Their Oxford average score was 40.3. Radiological assessment affirmed a good integration of the substitutes in bone without any edging in all cases. A progressive invasion of the ceramics by bone can be seen on the X-ray. We conclude that about 15 years of average delay, which is a significant follow-up in orthopedic surgery, the outcomes without specific complications are satisfactory and allow one to go with these materials in total hip revision surgery.

Impaction grafting of the acetabulum with ceramic bone graft substitute: high survivorship in 43 patients with a mean follow-up period of 4 years

BACKGROUND AND PURPOSE

Loss of bone stock remains a challenge in revision hip surgery. Grafting with allograft is well established, but there are problems with availability, cost, infection, antigenicity, reproducibility, and stability of the created construct. BoneSave is a biphasic porous ceramic consisting of sintered 80% tricalcium phosphate and 20% hydroxyapatite. In vitro and in vivo studies, including its use mixed with allograft, have shown good results in impaction grafting. This is the first reported series of its use alone in impaction grafting of the acetabulum.

METHODS

We conducted a retrospective review of a cohort of 43 consecutive patients undergoing impaction grafting of contained acetabular defects by multiple surgeons at a single centre. All patients received uncemented acetabular components. They were followed up radiographically, together with self-reported satisfaction scale (SAPS), Oxford hip score (OHS), and Short-Form 12 (SF12) health survey. Kaplan-Meier survivorship analysis was performed with revision of the acetabular component, revision of any part of the construct, and reoperation as endpoints.

RESULTS

The fate of all cases was known. Mean follow-up was 4 years. 5 patients died during follow-up, with their constructs in situ. The survivorship of the acetabular component was 98% (95% CI: 85-100) at 7 years. 1 acetabular component was revised for infection and there was 1 radiographic acetabular failure. The median OHS was 36 (6-48), the median SF12 PCS was 36 (14-57), the median SAPS was 75 (0-100), and the median SF12 MCS was 50 (23-64). The graft material had incorporated in all 3 zones of the acetabulum in 33 out of 37 cases with complete radiographic follow-up.

INTERPRETATION

Medium-term results show that BoneSave alone is a reliable material for impaction grafting of contained defects in the acetabulum at revision surgery.

Impaction grafting of the acetabulum with ceramic bone graft substitute mixed with femoral head allograft: high survivorship in 43 patients with a median follow-up of 7 years: a follow-up report

BACKGROUND AND PURPOSE

Restoration of bone stock at revision hip surgery remains a challenge. Alternative graft materials with suitable mechanical properties for impaction grafting have been sought due to issues with infection, antigenicity, cost, and availability of allograft. We have previously presented good short-term results of the use of BoneSave, a biphasic porous ceramic bone graft substitute, consisting of sintered 80% tricalcium phosphate and 20% hydroxyapatite, in a 50:50 mix with femoral head allograft. We now present the medium-term results.

METHODS

We conducted a retrospective review of a cohort of 43 consecutive patients undergoing impaction grafting of contained acetabular defects by multiple surgeons at a single center. 34 patients received uncemented acetabular components and 9 received cemented components. Patients were followed up radiographically and with the self-reported satisfaction scale (SAPS), Oxford hip score (OHS), and the Short-Form 12 (SF12) health survey. Kaplan-Meier survivorship analysis was performed with revision of the acetabular component, revision of any part of the construct, and reoperation as endpoints.

RESULTS

The fate of all cases was known. Median follow-up of the surviving patients was 80 (69-106) months. 15 patients died during the follow-up period, 14 with their construct in situ. The survivorship of the grafted acetabulum and acetabular component was 94% (95% CI: 99-78) at 7 years. 1 patient had been revised for aseptic loosening of the acetabulum and 1 for deep infection. The mean OHS was 31 (SD 12), the mean SF12 physical-component score (PCS) was 38 (SD 13), the median SAPS was 83 (0-100), and the median SF12 mental-component score (MCS) was 55 (23-65). The graft material became incorporated in all 3 zones of the acetabulum in 23 out of 24 cases that had complete radiographic follow-up.

INTERPRETATION

These medium-term results show that BoneSave is a reliable material for impaction grafting of the acetabulum when used in conjunction with femoral head allograft.

Modular acetabular reconstructive cup in acetabular revision total hip arthroplasty at a minimum ten year follow-up

PURPOSE

Modular acetabular reconstructive cups have been introduced in an attempt to offer initial rigid fixation by iliac lag screws and ischial pegs, to support bone grafts with a flanged metal socket, and to restore original hip center in acetabular revision. The purpose of this study was to clarify minimum ten year follow-up results of this cup system with morsellised allografts in revision cases.

METHODS

We retrospectively investigated 54 acetabular revisions at a mean of 11 years (range, ten to 14 years). The indications were Paprosky's type 2B (eight hip), 2C (eight hips), 3A (23 hips), 3B (nine hips), and 4 (six hips).

RESULTS

Using aseptic loosening as the endpoints, the survival rate was 89.3 % (95 % CI 81-98). Radiographically, one type 3A hip, three type 3B hips and one type 4 hip showed aseptic loosening while no type 2 hips or no cemented cups showed loosening.

CONCLUSIONS

The modular reconstructive cups for acetabular revision showed bone stock restoration and stable implantation.

Recommendations and considerations for the use of biologics in orthopedic surgery

Reconstruction of extensive bone defects remains technically challenging and has considerable medical and financial impact on our society. Surgical procedures often require a bone/substitute graft to enhance and accelerate bone repair. Bone autografts are associated with morbidity related to bone harvesting and are limited in quantity. Alternatively, bone allografts expose the patient to the risk of transmission of infectious disease. Synthetic bone graft substitutes, such as calcium sulfates, hydroxyapatite, tricalcium phosphate, and combinations, circumvent some of the disadvantages of auto- and allografts, but have limited indications. Biomedical research has made possible the stimulation of the body's own healing mechanisms, either by delivering exogenous growth factors locally, or by stimulating their local production by gene transfer. Among all known factors having osteoinductive properties, only two bone morphogenetic proteins (for specific indications) and demineralized bone matrix have been approved for clinical use. In addition, ongoing research is exploring the efficacy of cell therapy and tissue engineering. The present report examines the composition, biological properties, indications, clinical experience and regulations of several of the biotherapeutics employed for bone reconstruction.

Bone graft substitutes in hip revision surgery: a comprehensive overview

INTRODUCTION

Total hip replacement is increasingly used to treat diseased and damaged joints. With time, some joint replacements may require revision, mainly because of instability and mechanical loosening, and this is of particularly significance to younger patients. A major problem in revision surgery is the loss of bone stock and the consequent difficulty in reconstructing a stable joint. Loss of bone stock has been widely treated using bone autografts and allografts but supplies are limited. Use of bone graft substitutes in combination with, or as a substitute for, human bone is a possible alternative.

AIM

To identify empirical studies of bone graft substitutes in hip revision surgery.

METHODS

Systematic review based on Cochrane and MOOSE methods. We searched MEDLINE and EMBASE to December 2010 with terms relating to hip replacement and bone graft substitutes, and checked key citations in ISI Web of Science and reference lists. We considered all human studies irrespective of study design.

RESULTS

Searches identified 397 articles. Screening of abstracts and full text articles identified 7 studies reporting outcomes of bone-graft substitute combined with autograft or allograft, and 6 studies reporting outcomes of bone graft substitute exclusively. One economic evaluation compared costs of femoral head banking with costs of bone graft substitutes. No randomised controlled trials evaluating bone graft substitute effectiveness were identified. Studies generally included small numbers of patients with a follow up too short to assess outcomes relating to implant survival. However, excepting those based on glass ceramic, ceramic bone graft substitutes show promise as an alternative to use of exclusive autograft or allograft. In the case of calcium phosphate ceramic bone graft substitute, potential cost savings were evident.

CONCLUSION

With increased allograft shortage, bone graft substitutes will be required in hip revision surgery. However, appropriately designed randomised controlled trials are required to compare use of existing and new bone graft substitutes with established practice. As well as prosthesis related outcomes, studies should explore the patient experience of revision hip replacement with bone graft substitute material.

Study of the osteoconductive capacity of hydroxyapatite implanted into the femur of ovariectomized rats

Osteoporosis is a global public health that affects postmenopausal women due to the deficiency of estrogen, a hormone that plays an important role in the microarchitecture of bone tissue. Osteoporosis predisposes to pathological bone fracture that can be repaired by conventional methods. However, depending on the severity and quantity of bone loss, the use of autogenous grafts or biomaterials such as hydroxyapatite might be necessary. The latter has received increasing attention in the medical field because of its good biological properties such as osteoconductivity and biocompatibility with bone tissue. The objective of this study was to evaluate using histologic and radiographic analyses, the osteogenic capacity of hydroxyapatite implanted into the femur of rats with ovariectomy-induced osteoporosis. Eighteen rats were divided into three groups with six animals in each: group nonovariectomized, bilaterally ovariectomized not receiving estrogen replacement therapy, and bilaterally ovariectomized submitted to estrogen replacement therapy. Defects were created experimentally in the distal epiphysis of the femur with a surgical drill and filled with porous hydroxyapatite granules. The animals were sacrificed 8 weeks after surgery. The volume of newly formed bone in the implant area was quantified by morphometrical methods. The results were analyzed by ANOVA followed by the Tukey test (P < 0.05). The hydroxyapatite granules showed good radiopacity. Histological analysis revealed less quantity of newly formed bone in the ovariectomized group not submitted to hormone replacement therapy. In conclusion, bone neoformation can be expected even in bones compromised by estrogen deficiency, but the quantity and velocity of bone formation are lower.

Shed blood-derived cells from total hip arthroplasty have osteoinductive potential: a pilot study

BACKGROUND

Cell therapy using autologous cells has been used in the treatment of various medical conditions. The mononuclear cell (MNC) fraction of bone marrow (BM) contains stem/progenitor cells that could contribute to osteogenesis and angiogenesis.

QUESTIONS/PURPOSES

We asked whether MNCs derived from intraoperative shed blood (SB), consisting of peripheral blood and BM, have osteoinductive and angiogenic potential.

METHODS

We harvested SB and BM from six patients undergoing THA. Isolated MNCs from SB and BM were analyzed by flow cytometry to evaluate the CD34(+) cell fraction and 1 × 10(6) cells were seeded on an interconnective porous calcium hydroxyapatite ceramic (IP-CHA) and transplanted in the backs of athymic rats. IP-CHAs without cells were transplanted as controls and all composites were harvested after 4 and 8 weeks. Osteoinductive potential was evaluated by histologic observation, immunohistochemistry, and enzyme-linked immunosorbent assay (ELISA) using anti-osteocalcin (OC) antibodies qualitatively and quantitatively. To evaluate angiogenic potential, capillary density was measured by immunohistochemistry using Isolectin B4 4 weeks after implantation.

RESULTS

We found that CD34(+) cells existed in SB-MNCs and there was a trend toward lower frequency compared with BM-MNCs. Histologic osteoinduction, OC expression, and capillary density were increased by transplantation of MNCs from SB. Similar results were achieved with MNCs from BM.

CONCLUSIONS

MNCs from SB have equivalent osteoinductive and angiogenic potential compared with those from BM.

CLINICAL RELEVANCE

SB could be an attractive source for isolation of MNCs, enhancing osteoinduction and neovascularization, to augment the reconstruction of skeletal defects.

Two-stage revision surgery for hip prosthesis infection using antibiotic-loaded porous hydroxyapatite blocks

BACKGROUND

Infection of a hip prosthesis is one of the most severe complications encountered in orthopedic practice. Two-stage reconstruction using an antibiotic-impregnated cement spacer has become a popular procedure for the treatment of this condition. However, there are some disadvantages with the use of antibiotic-loaded cement, including low biocompatibility, a very low release ratio, and the possibility of thermal damage to the antibiotic. We have developed an effective drug delivery system for osteomyelitis in which porous hydroxyapatite (HA) blocks are loaded with an antibiotic by the vacuum method. We report here a modification of this delivery system applied for the first stage of two-stage reconstruction surgery against infected hip prosthesis.

PATIENTS AND METHODS

Eight consecutive patients who developed hip prosthesis infection underwent two-stage revision total hip arthroplasty (THA) using antibiotic-loaded porous HA blocks prepared by the vacuum method. Thorough debridement and insertion of antibiotic-loaded HA blocks was performed in the first stage, followed by conversion to THA after eradication of infection in the second stage.

RESULTS

The mean interval between the stages was 16.8 weeks. There were no complications related to the use of the antibiotic-loaded HA blocks. The patients were followed up for an average of 49 months with no evidence of recurrent infection. The mean Japanese Orthopedic Association hip score improved from 45.1 before surgery to 79.6 at the latest follow-up.

INTERPRETATION

This simple approach utilizing antibiotic-impregnated HA blocks prepared by the vacuum method is considered to be effective for treatment of hip prosthesis infection.

USE OF BIOCERAMICS IN FILLING BONE DEFECTS

Objective: To present the results from using biological ceramics for filling bone defects resulting from post-traumatic or orthopedic injuries. Methods: Thirty-six patients with bone defects caused by trauma or orthopedic injury were evaluated. Nineteen patients were male (52.8%) and 17 were female (47.2%). Their ages ranged from 19 to 84 years, with a mean of 45.7 years and median of 37 years. Only patients with defects that required at least five grams of biological ceramic were included. Eighteen cases were classified as orthopedic: bone defects were observed in 11 cases of total hip arthroplasty; one case of primary total hip arthroplasty, due to coxarthrosis; five cases of femoral or tibial open wedge osteotomy; and one case of tarsal arthrodesis. There were 18 cases of trauma-related defects; uninfected pseudarthrosis, eight cases; recent fractures of the tibial plateau with compression of the spongy bone, three cases; and exposed fractures treated with external fixators, seven cases. The surgical technique consisted of curetting and debriding the injury until bone suitable for grafting was found. Biological ceramic was then used to fill the defect and some kind of fixation was applied. Results: Among the 36 patients evaluated, it was seen that 35 (97.2%) presented integration of the biological ceramic, while one case of open fracture treated with external fixation had poor integration of the biological ceramic. Conclusion: Treatment of bone defects of orthopedic or post-traumatic etiology using a phosphocalcium ceramic composed of hydroxyapatite was shown to be a practical, effective and safe method.

Total hip arthroplasty using Kerboull-type acetabular reinforcement device for rapidly destructive coxarthrosis

We studied 20 primary cemented total hip arthroplasties performed using Kerboull-type acetabular reinforcement device for rapidly destructive coxarthrosis. The average patient age at the time of surgery was 68.3 (range, 60-77) years. The mean follow-up period was 6.3 years (3.8-11.8). The mean preoperative Japanese Orthopedic Association hip score was 38.1 (16-70) vs 85.2 (70-93) at the latest follow-up. The radiographic outcome in 20 hips showed no migration or aseptic loosening. A partial radiolucent line at the cement-bone interface was noted in 2 hips (10%), but no progression occurred. There were no major complications. No patient required repeated surgery. The use of Kerboull-type acetabular reinforcement device for rapidly destructive coxarthrosis provided satisfactory 3-year to 11-year clinical and radiographic results.

The Use of Ceramics as Bone Substitutes in Revision Hip Arthroplasty

The number of grafting procedures, including those performed in primary and revision hip arthroplasty, continues to rise around the world. Demand for musculoskeletal donor tissue now outstrips supply. There is no single bone substitute that is ideal for all circumstances. Bone substitutes act as a scaffold and are usually osteoconductive. They are rarely osteoinductive; if they are, a molecular bond is formed between the graft and host bone, improving fixation and longevity. Bone graft substitutes are very rarely osteogenic. There is a growing body of clinical evidence supporting the use of bone graft substitutes in vivo for complex hip arthroplasty.

Radiological evaluation of the femoral component fixed with interface bioactive bone cement in revision total hip arthroplasty

Thirty cases whose femoral side was operated with interface bioactive bone cement technique in revision total hip arthroplasty for aseptic loosening and followed for more than 6 years were evaluated. The present study includes 2 men and 28 women with an average age at operation of 60 years. Mean postoperative follow-up period was 9 years. Rerevision of femoral component was not found. Possible loosening was observed in 1 case, using the criteria of Harris. Among 21 cases whose cementing grade was assessed as B or C in postoperative x-ray, radiolucent line at bone-cement interface has disappeared before last follow-up in 11 cases. The present study revealed that the good result was obtained using the interface bioactive bone cement technique for reconstruction of aseptic femoral loosening.

Coralline hydroxyapatite in complex acetabular reconstruction

This retrospective study examined whether a coralline hydroxyapatite bone graft substitute adequately repaired bone defects during complex acetabular reconstructions. Seventeen patients who underwent acetabular revision using Pro Osteon 500 were assessed to determine whether any cups required re-revision, whether bone had incorporated into the coralline hydroxyapatite grafts, and whether the coralline hydroxyapatite grafts resorbed with time. At latest follow-up, no cups required re-revision, but 1 had failed. Radiographic evidence of bone incorporation was observed in every coralline hydroxyapatite graft. Graft resorption was not observed.

Acetabular reconstruction using a cementless cup and hydroxyapatite granules: 3- to 8-year clinical results

We investigated 17 patients undergoing consecutive revision or conversion total hip arthroplasties with a cementless cup for acetabular bone defects. Patients were all women and the average age at the time of surgery was 61.2 years. All bone defects were filled and packed with porous hydroxyapatite (HA) granules. The average follow-up was 5.6 years (range, 3-8 years). The average Merle d'Aubigné functional hip score was 15.6 at the latest follow-up vs 11.6 before surgery. No patients needed additional revision surgery. In 4 cases in which a superior deficiency had been covered with HA granules, the cup migrated superior to the host bone but without any detrimental effect. The remaining 13 cases showed no migration of the cup. We conclude that acetabular reconstruction with a cementless cup and HA granules seems to provide encouraging intermediate results.

No positive effects of OP-1 device on the incorporation of impacted graft materials after 8 weeks: a bone chamber study in goats

BACKGROUND

Bone morphogenetic proteins (BMPs) have the potential to improve clinical outcome after hip revision surgery by improving graft incorporation and implant fixation. However, impaction of cancellous bone grafts and TCP/HA bone substitute mixed with OP-1 device in a bone chamber in goats in a previous study led to reduced fibrous tissue ingrowth after 4 weeks. New bone formation was not promoted by OP-1. In the current study we examined whether this reduction represented a final loss of ingrowth or was just a delay, and whether the reduction can be overcome and ultimately results in a better late ingrowth.

METHODS

Bone chambers with impacted allografts and impacted TCP/HA granules mixed with 2 doses of OP-1 device were implanted in proximal medial goat tibias. Impacted allografts and TCP/HA not treated with OP-1 served as controls. After 8 weeks, the incorporation was evaluated using histology and histomorphometry.

RESULTS

Histology revealed evidence of bone graft incorporation, which proceeded in a similar way in both allografts and TCP/HA, with and without the addition of OP-1. After 8 weeks, no difference in bone ingrowth was found between the OP-1 groups and their controls. It was only in the allografts that the addition of OP-1 resulted in more fibrous tissue ingrowth.

INTERPRETATION

We conclude that the previously observed delay in fibrous tissue ingrowth can be only partially overcome.

Graft incorporation after acetabular and femoral impaction grafting with washed irradiated allograft and autologous marrow

Rates of around 40% incorporation have been described when chips of irradiated cancellous allograft with retained fat were impacted with the Exeter technique. We report the results of acetabular and femoral impaction bone grafting during revision hip arthroplasty using washed irradiated allograft with autologous marrow. Eighty-five consecutive patients underwent acetabular and or femoral revision arthroplasty. Evidence of graft cortication and trabeculation was recorded on successive postoperative radiographs, over a mean period of 44 months. Ninety-six percent (49/51) and 90% (53/59) of patients showed incorporation in acetabular and femoral grafts, respectively. This was usually apparent by 6 months postoperatively. We conclude that the addition of autologous marrow to irradiated bone allograft during impaction grafting is a cheap and highly effective way of achieving graft incorporation.

High doses of OP-1 inhibit fibrous tissue ingrowth in impaction grafting

A major concern in using growth factors in impaction grafting is the potential stimulation of the osteoclastic lineage. A solution would be using an osteoconductive material resistant to resorption and providing initial stability after reconstruction. Growth factors may promote bone formation in combination with such graft materials. We determined whether OP-1 would promote the incorporation of impacted morselized allografts and tricalcium phosphate/hydroxyapatite (TCP/HA) into host bone, whether bone formation would be preceded by an initial process of accelerated resorption, and whether the response to OP-1 remodeling/incorporation would be dose-related. We performed two bone chamber studies in goats to ascertain the early effects of OP-1 dose on resorption and incorporation of impacted morselized allografts and TCP/HA. After 4 weeks, the incorporation process of impacted morselized allografts and TCP/HA was not promoted by OP-1. We observed no signs of accelerated resorption preceding bone formation. An increase in OP-1 dose resulted in an inhibition of fibrous tissue formation but OP-1 did not promote bone formation. Early failures in impaction grafting, using mixes with OP-1, might be explained by the lack of fibrous tissue ingrowth and not by increased resorption and remodeling.

Hydroxyapatite augmentation for bone atrophy in total ankle replacement in rheumatoid arthritis

Although total ankle replacement is routinely used for rheumatoid arthritis of the ankle, it has been hampered by early implant failures such as loosening and subsidence of the tibial component due to poor bone quality. To prevent this complication, total ankle replacement augmented by a specially designed hydroxyapatite coating was used in 14 patients (16 feet). Patients were reviewed after an average follow-up of 23.1 months, and the mean clinical rating scale significantly improved from 30.7/100 points preoperatively to 65.9/100 at final follow-up, especially with respect to pain relief. Radiographs taken immediately postoperatively and at final follow-up were analyzed for the position and sinking of the tibial component. The position was evaluated by measurement of the alpha and beta angles, formed by the tibial long axis and tibial component on anteroposterior and lateral radiographs, respectively. The mean alpha and beta angles were 87.4 degrees and 79.3 degrees postoperatively and 87.7 degrees and 81.0 degrees at final follow-up, respectively. No significant change was noted in either angle between the immediate postoperative views and at final follow-up, and no significant subsidence was noted. Radiographs were also assessed for the presence of a lucent zone: 1 case demonstrated a clear zone between hydroxyapatite and bone, 9 cases between hydroxyapatite and the tibial component, and 6 cases between the tibial component and bone. These results suggest that hydroxyapatite helps to secure implant fixation firmly to the bone, making it a useful augmentation for tibial bone atrophy in total ankle replacement for rheumatoid arthritis.

Bone substitution in revision hip replacement

The aim of this retrospective study was to report the preliminary results of femoral peri-prosthetic bone defect reconstruction with a synthetic bone substitute. Twenty-one revisions of the femoral component in 20 patients were evaluated. The mean age at operation was 65.7 years (range, 30 to 79 years). Preoperative femoral deficiencies were rated grade II in 7 cases and grade III in 14 cases according to the SOFCOT classification. None was rated grade IV. Femoral revision was indicated for loosening in 18 hips (including 8 septic cases), femoral osteolysis (1 hip), persistent pain (1 hip) and recurrent dislocation (1 hip). Once the loose prosthesis had been removed, calcium phosphate ceramic (CPC) granules (14 cases) or ceramic granules + cancellous allograft (5 cases) or autograft (2) were firmly impacted in the femoral canal. The stem was standard and always cemented using modern cementing technique. At a mean follow-up of 36 months (range, 14 to 76 months), 90% of the hips were rated good or very good according to the Merle d'Aubigné score. Two diaphyseal femoral fractures occurred and later united. Two hips required re-revision (aseptic loosening; septic recurrence). The absence of radiological osteolysis in 17 cases suggested direct bonding between ceramic granules and bone. Stem subsidence occurred in two cases and was limited (5 and 8 mm). Femoral bone reconstruction using impacted CPC or CPC in conjunction with bone graft in revision hip replacement commonly provided restoration of the bone stock in the short to mid-term. Further long-term studies will be necessary to support this conclusion.

Reconstruction fémorale par céramique de phosphate de calcium macroporeuse impactée au cours des reprises d’arthroplastie de hanche

PURPOSE OF THE STUDY

Management of bone stock loss remains one of the most challenging problems for revision hip surgery. The aim of this retrospective study was to report the preliminary results of peri-prosthetic femoral defect reconstruction with impacted granules of calcium phosphate ceramic.

MATERIAL AND METHODS

Fourteen hips in 13 patients (3 men and 10 women) were evaluated. Age at surgery ranged from 30 to 79 years (mean 66.1 years). All revised devices had been cemented. Femoral revision was indicated for loosening in eleven hips (including six septic cases), femoral osteolysis (one hip), persistent pain (one hip), and recurrent dislocation (one hip). On the preoperative radiological evaluation, bone defects were assessed as SOFCOT grade II in seven case, and grade III in fourteen. None was rated grade IV. Once the loose prosthesis had been removed, bone graft or ceramic granules (14 cases) were firmly impacted in the femoral canal. The stem was standard and always cemented using modern cementing technique.

RESULTS

At a mean follow-up of 34 +/- 15 months (range 14-76 months), eleven of fourteen hips were rated good or very good according to the Postel-Merle-d'Aubigné score. One diaphyseal femoral fracture occurred and later united. Two hips required re-revision (one aseptic femoral loosening, one septic recurrence). Direct bonding between synthetic graft and bone was observed on standard radiographs in eleven cases. Stem subsidence occurred in two cases and was limited (mean 4.5 mm).

DISCUSSION

Femoral bone reconstruction using impacted calcium phosphate ceramic in revision hip arthroplasty provided encouraging results in the short to mid term. Femoral stock restoration was achieved in the great majority. No adverse effect related to the use of a synthetic graft was noted. Further long-term evaluation is required before wider application.

Biological and mechanical changes of the bone graft-cement interface after impaction allografting

In impaction allografting, the host bone interface may consist of morsellized allograft alone or as a composite with bone cement. The objective of this study was to investigate the temporal changes in the interface for these two materials in a rat bone chamber model. To simulate the impaired endosteal circulation after impaction allografting, bone chambers were tightened bilaterally to the endosteal surfaces of proximal tibiae of mature rats and filled with pure allograft or cement/allograft composite. The cement/allograft composite-host bone interface strength was significantly higher at 3 weeks and was higher than the allograft construct failure strength. Limited allograft, but extensive periosteal remodeling, was observed at 3 weeks which resulted in a significantly increased cortical porosity and cortical thickness. The allograft porosity decreased significantly at 6 weeks indicating extensive remodeling of the allograft bone. Little or no remodeling of the allograft particles in the cement was found. At 6 weeks a new medullary canal was formed, and the endosteal cortex was partially absorbed. Endosteal absorption resulting in medullary canal widening in revision THR may be responsible for clinically unstable stems after impaction allografting.

Impaction bone grafting with hydroxyapatite: increased femoral component stability in experiments using Sawbones

BACKGROUND

Substantial bone loss and bone defects increase the amount of allografting required in hip revision surgery. Thus, the use of a synthetic material to limit the amount of allograft tissue required for impaction grafting is desirable. We evaluated the potential of hydroxyapatite (HA) mixtures to provide initial mechanical stability to a polished tapered femoral stem.

MATERIAL AND METHODS

We determined the initial stability of a polished tapered femoral stem after reconstructing a cavitary femoral bone defect by impaction bone grafting with cement in Sawbones composite femurs. Three types of graft material were tested for their ability to improve initial rotational stability. The graft materials investigated were pure allograft, a mixture of 50% allograft and 50% hydroxyapatite (HA), and pure HA.

RESULTS

We found a statistically significant difference between the three groups as regards torsional micromotion and failure load.

INTERPRETATION

Our findings suggest that reconstruction of femoral bone defects with pure HA or a mixture of allograft and HA provides adequate initial stability for femoral revision arthroplasty using impaction grafting.

Poor results after augmenting autograft with xenograft (Surgibone) in hip revision surgery: a report of 27 cases

BACKGROUND

Surgibone Unilab is prepared from bovine bone and contains hydroxyapatite and protein. It is supposed to be immunogenically inert but the protein could be antigenic in man.

PATIENTS AND METHODS

We followed 27 patients for an average of 2.5 (1-5) years, all of whom had received Surgibone mixed with autograft to fill in defects in the acetabulum and the proximal femur in revision hip surgery.

RESULTS

In 17 patients, there was apparently complete incorporation of the bone graft within 6 months. In 3 of these patients, the graft was incorporated after 3 months. In 3 patients, however, there was no incorporation of the graft as late as 3 years after the operation. 3 other patients appeared to have a type of graft rejection (pseudoinfection). 1 other patient suffered MRSA deep infection of the prosthesis which resulted in removal of the implants 1 month postoperatively.

INTERPRETATION

Use of Surgibone xenograft in revision hip surgery, even in combination with autograft, resulted in failure and the need for rerevision in at least one quarter of the cases studied.

Potential pitfalls of radiolabel adsorption to ceramic biomaterials

The use of radiolabeled precursor molecules for the metabolic analysis of cell functions is commonplace. Tritiated thymidine, in particular, has been used to quantitate cellular proliferation in numerous cells, including osteoblasts, when cultured on various biomaterials. Our aim was to assess cellular protein synthesis and proliferation, on a range of fluoride ion-substituted hydroxyapatites. Initially, we used a classical metabolic analysis strategy with radiolabeled tracer molecules. Our results suggested that these materials supported enhanced protein synthesis and proliferation of SaOS-2 human osteoblast-like cells. However, control samples also revealed enhanced adsorption of the radiolabeled tracer. We have shown that this arises because partially fluoride ion-substituted hydroxyapatite exhibits enhanced adsorptive characteristics of radiolabeled leucine and thymidine over tissue culture plastic, hydroxyapatite, and fluoroapatite. Moreover, manual cell count data obtained through SEM analysis showed no significant difference in cell proliferation between any of the materials, further indicating that our initial results were artifacts. These results highlight the use and reporting of appropriate cell-free controls are critical in bioassays examining functional responses of cells to biomaterials, and if absent, may confound accurate data interpretation. Our findings have general implications for investigations of cell function on other novel ceramic biomaterials.

The initial stability of cemented acetabular cups can be augmented by mixing morsellized bone grafts with tricalciumphosphate/hydroxyapatite particles in bone impaction grafting

Tricalciumphosphate (TCP) and hydroxyapatite (HA) have been suggested as bone graft substitutes in a wide range of applications. In this study, the initial stability of cemented acetabular cups was determined after reconstructing a combined cavitary and segmental defect in a realistic acetabular revision surgery model. The defects were reconstructed with mixes of TCP/HA particles and human bone grafts using the bone impaction grafting technique. In comparison with defect reconstruction with human bone grafts only, cup translation and tilt decreased by 27% when mixes of bone grafts and porous TCP/HA particles were used and by 55% when mixing the bone grafts with solid TCP/HA particles. Increasing the TCP/HA ratio within the mix significantly decreased cup translation. From a biomechanical perspective, mixes of TCP/HA particles and bone grafts are an attractive alternative for morsellized bone grafts when using the bone impaction grafting technique in the reconstruction of large defects of the acetabulum.

Acetabular reconstruction using a Kerboull-type acetabular reinforcement device and hydroxyapatite granules: a 3- to 8-year follow-up study

Between 1993 and 1997, 21 consecutive revision total hip arthroplasties were performed in 20 patients using hydroxyapatite (HA) granules supported by a Kerboull-type reinforcement acetabular device. Acetabular bone loss according to the American Academy of Orthopaedic Surgeons (AAOS) system was type II for 5 hips and type III for 16 hips. Autografts were used to reconstruct the major segmental defects in 6 hips. The mean follow-up period of the series was 5 years and 4 months. No migration of the socket was seen. Slight inclination of the acetabular device was noted in 1 hip without functional deficits. The mean preoperative Merle d'Aubigné hip functional score was 9.3 versus 15.4 at the latest follow-up evaluation. Acetabular reconstruction with HA granules and a Kerboull-type acetabular device provided satisfactory 3- to 8-year clinical and radiographic results.

Acetabular defect reconstruction with impacted morsellized bone grafts or TCP/HA particles. A study on the mechanical stability of cemented cups in an artificial acetabulum model

In revision surgery of the acetabulum bone defects can be filled with impacted human morsellized bone grafts. Because of a worldwide limited availability of human bone, alternatives are being considered. In this study we compared the initial stability of acetabular cups after reconstructing a cavitary defect with various compositions of impacted tricalciumphosphate-hydroxyapatite (TCP/HA) particles and mixes of TCP/HA particles and human grafts in a realistic acetabulum model. Primary cemented cups and reconstructions with impacted human cancellous grafts were used as reference. A dynamic load displaced the acetabular cups superomedially. The primary cemented cups showed the highest stability. The cups with impacted human grafts produced the most displacement. All reconstructions with the TCP/HA particles showed a high stability of the cups. However, especially when using large TCP/HA particles this was probably due to a large amount of cement penetration. Mixing TCP/HA particles with human grafts seemed to decrease cement penetration. although still a high stability was obtained. In this perspective, we concluded that TCP/HA particles might be useful as a bone graft extender in the reconstruction of acetabular bone defects.

New bone formation around porous hydroxyapatite wedge implanted in opening wedge high tibial osteotomy in patients with osteoarthritis

A porous hydroxyapatite (highly purified synthetic Ca10(PO4)6(OH)2) wedge was inserted into the tibia in 10 knees of 7 patients with osteoarthritis of the knee who underwent high tibial osteotomy. The interface of this HA wedge with bone was histologically examined in undecalcified specimens obtained at the time of hardware removal in all 10 knees, and total incorporation of the HA into bone was observed, with no inflammatory reaction. The proportion of pores that were filled with regenerated bone within 300 microm from the interface was 71.8 +/- 10.1% (mean +/- S.D.), and it was positively correlated with the time from implantation to biopsy. Radiodensity of the HA wedge was measured during the follow-up period, and it did not change significantly within 36 months after osteotomy. Our study concluded that bone ingrowth into the HA block slowly progressed and was correlated with the passage of time.

Cancellous impaction grafting in the human femur: histological and radiographic observations in 6 autopsy femurs and 8 biopsies

6 whole postmortem femurs and 8 femoral biopsies were studied histologically, 3 months to 8 years after cancellous impaction grafting with a cemented stem for aseptic loosening. All stems were stable. Radiographs showed cortical healing in 5 cases, trabecular remodelling in 1, and trabecular incorporation in 9. There was a radiolucent line in 1 case. The histology varied. There was always a viable cortical shell around the grafted area. 1 patient showed complete bony restitution. The others still had varying amounts of remaining graft in the neo-medullary cavity, even after 8 years. The graft particles were usually embedded in dense fibrous tissue, thus forming a supporting composite tissue capable of carrying load. There was no time-dependent deterioration in the histological appearance. Radiographically, cortical healing and trabecular remodeling corresponded to viable bone. The lack of a radiolucent line said little about the viability of the tissue closest to the cement. The radiographs did not detect thin soft tissue membranes. Radiographic criteria used to assess primary total joint replacement do not necessarily apply to impaction grafting, and radiographic changes should be interpreted cautiously, especially as regards tissue viability.

Histologic and mechanical evaluation of impacted morcellized cancellous allografts in rabbits: comparison with hydroxyapatite granules

The bioactivity and mechanical properties of morcellized allografts and hydroxyapatite (HA) granules were evaluated in a rabbit model. Allografts were replaced by viable trabecular structures within 8 weeks. The yield strength and stiffness of allografts were within normal cancellous bone levels by 3 weeks and were maintained afterward. The amount of newly formed bone around HA granules was comparable to that around allografts. The yield strength and stiffness of HA granules were significantly higher than those of allografts at 3 and 12 weeks. Allografts offer the advantage of being replaced by host-bone without significant deterioration in mechanical properties over the course of remodeling. HA granules can also be used for a bone substitute given their bioactivity in bone conduction and superiority in mechanical properties to allografts.

Characterization of processed tooth hydroxyapatite for potential biomedical implant applications

In this study hydroxyapatite (HA) (100-150 microns) derived from freshly-extracted human teeth in laboratory conditions was investigated. Scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDXS), wet chemical, ion chromatographic peak method (ICP), atomic absorption, x-ray diffraction and infra-red (IR) were performed separately for HA obtained from dentine and enamel. This naturally derived HA did not differ from synthetic ones. Its production was simple when compared with other methods. Processed tooth HA could safely be used in animal subjects prior to human studies as a graft material after biocompatibility studies fully conducted.