The use of hydroxyapatite cement in secondary craniofacial reconstruction.

Sixty-one patients underwent secondary craniofacial reconstruction for contour defects using hydroxyapatite cement over a 3-year period (20-month mean follow-up). There were 56 children, aged 2.2 to 18 years (mean, 10.7 years), 21 boys and 35 girls. This is the first series of pediatric patients in whom the use of hydroxyapatite cement has been reported. There were five adults aged 21 to 46 years (mean, 32 years), 3 men and 2 women. Thirty-one patients underwent reconstruction for secondary orbitocranial defects after surgery for synostosis, 7 after surgery for hypertelorism, 10 for posttraumatic skull defects, and 13 for a variety of other facial skeletal defects. There were seven complications (11 percent), ranging from a retained drain to postoperative seromas, all of which required reoperation without loss of the contour correction. All of the complications occurred in the first 18 months of our study. There has been excellent retention of implant volume with no recurrence of contour defects to date. We have not found any visible evidence of interference with craniofacial growth over the study period. We conclude that hydroxyapatite cement is a versatile and safe biomaterial when used for the correction of secondary craniofacial contour defects in children and adults. The coupling of antibiotics with this biomaterial may have applications in the treatment of osteomyelitis.     

Experimental hydroxyapatite cement cranioplasty.

Hydroxyapatite cement is a calcium phosphate-based material that when mixed with water forms a dense paste that sets within 15 minutes and isothermically converts in vivo to a microporous hydroxyapatite implant. This cement was used to reconstruct bilateral 2.5-cm-diameter full-thickness critical-sized parietal skull defects in six cats. One side was reconstructed with 100 percent hydroxyapatite cement, and the other with a mixture of 50 percent hydroxyapatite cement and 50 percent ground autogenous bone by weight. These animals were sacrificed at 6 and 12 months after implantation. Positive and negative controls also were prepared. The anatomic contour of the soft tissue overlying all hydroxyapatite cement implants was well maintained, there were no wound infections or structural failures, and the implants were well tolerated histologically. None of the negative (unreconstructed) control defects was completely filled with repair bone, and all positive (methyl methacrylate) controls demonstrated foreign-body giant-cell formation and fibrous encapsulation of the implants. Examination of decalcified and undecalcified sections revealed progressive but variable replacement of the cement by new bone and soft tissue without a change in the shape or volume of the hydroxyapatite cement-reconstructed areas. New bone comprised 77.3 and 64.7 percent of the tissue replacing the hydroxyapatite cement and hydroxyapatite cement-bone implants, respectively. Replacement of the hydroxyapatite cement implants by new bone is postulated to occur by a combination of osteoconduction and implant resorption. These results indicate that further experimental research leading to the possible application of hydroxyapatite cement for full-thickness calvarial defect reconstruction in humans is warranted.     

Applications of a new carbonated calcium phosphate bone cement: early experience in pediatric and adult craniofacial reconstruction

Hydroxyapatite cements have recently been employed as bone substitutes in craniofacial reconstruction. They are easily applied, nonresorbable, available in unlimited quantity, and eliminate donor-site morbidity. Norian CRS (craniofacial repair system) is a new carbonated calcium phosphate paste that is unique in that it more closely resembles bone than do traditional hydroxyapatite pastes. Norian is a low-order crystalline apatite soluble at a low pH, facilitating its resorption and replacement by host bone. The cement was first used for craniofacial surgery in North America at the Children's Hospital of Philadelphia. This report presents the authors' experience with this bone substitute in both pediatric and adult craniofacial reconstruction. Sixteen adult and pediatric patients underwent craniofacial reconstruction involving the use of carbonated calcium phosphate paste for correction of defects that required from 5 to 110 g of carbonated calcium phosphate paste (mean, 28.5 g). The patients were all followed for a minimum of 14 months. Minor complications included one case of infection and two cases involving cement microfragmentation. In the authors' experience, carbonated calcium phosphate paste has proved to be an excellent alloplastic material for osseous augmentation and reconstruction in the craniofacial skeleton. Few problems were encountered using this material; no significant morbidity was encountered. Although this material seems to be promising as a bone substitute, further follow-up will be necessary to evaluate its potential role in craniofacial surgery.     

Orbital floor reconstruction using calcium phosphate cement paste: an animal study

Orbital floor defects were created in 10 New Zealand white rabbits and were reconstructed using an injectable calcium phosphate paste. These animals were euthanized at 2, 4, 8, and 12 months after implantation and were examined for biocompatibility and osteoconductivity. Grossly, implants were found to be adherent to the floor and covered with fibrous tissues. There was no sign of infection, extrusion, or migration of implant within the orbit and maxilla. The orbital floor was completely restored. Histological examination showed active new bone formation that encroached within the implant and gradually increased in density with time. Maxillary mucosa and glands were likewise reconstituted. Thin fibrovascular tissues were seen on top of and within the surface of the implant, and few to slight inflammatory cells were seen. Microradiography showed direct apposition between the new bone and the implant. These findings compare favorably with previously published reports on the biocompatibility and osteoconductivity of calcium phosphate cement. The authors believe that, together with ease of use and structural integrity, calcium phosphate paste can be useful in orbital floor reconstruction.     

Porous, block hydroxyapatite as an interpositional bone graft substitute in orthognathic surgery

Forty-six nonconsecutive patients undergoing orthognathic surgery in whom blocks of coralline, porous hydroxyapatite (Interpore-200) were used in lieu of interpositional bone grafts are the subjects of this report. Surgical procedures included inferior repositioning of the maxilla (7) and chin (12), maxillary advancements in cleft (4) and noncleft individuals (13), and transverse maxillary expansions (12). Patients included in this study were only those in whom bone grafts would have been harvested had hydroxyapatite not been available. A total of 93 anatomic sites were implanted. The complication rate attributable to the use of the implant was 4.3 percent. Follow-up period ranged from 6 to 20 months, with a mean of 9.3 months. At this time, osseous stability was confirmed cephalometrically in all but two patients undergoing maxillary expansions. The biologic behavior and mechanical properties of coralline-derived, porous, block hydroxyapatite are discussed. These implant characteristics make it a feasible bone graft substitute for interpositional use in orthognathic surgery. Proper indications for its use as well as technical details to minimize complications are stressed.     

Cranial reconstruction with computer-generated hard-tissue replacement patient-matched implants: indications, surgical technique, and long-term follow-up

The aim of this clinical study was to evaluate the effectiveness and safety of using computer-generated alloplastic (hard-tissue replacement) implants for the reconstruction of large defects of the upper craniofacial region. Fourteen patients who had large (> 150 cm2) preexisting defects of the cranium or cranio-orbital region underwent surgical reconstruction. Preoperatively, a three-dimensional computed tomographic scan was obtained from which an anatomic model was fabricated. The defect in the model was then used to create an alloplastic (hard tissue-replacement polymer) implant for reconstruction and surgical placement. At the time of surgery, the implant was secured into position with either metal or resorbable fixation. In cases where the frontal sinus was in proximity to the implant, the frontal sinus was either cranialized and covered with a pericranial flap or obliterated with hydroxyapatite cement. In cases that had been previously irradiated or infected, wide bony debridement and coverage with a vascularized muscle was initially performed, followed by implant reconstruction 6 months later. All implants fit easily into the bone defects, and only four (29 percent) required some minor adjustments to complete the fit. All patients healed uneventfully. With a minimum of 1 year follow-up (average, 3 years) in all cases, excellent contours have been maintained and all patients have remained infection-free. In large cranial defects, custom implants fabricated from porous, hydrophilic hard-tissue replacement polymer provide an exacting anatomic fit and a solid stable reconstruction. This method of reconstruction in these defects is rapid and exact, and significantly reduces operative time. Critical attention must be paid, however, to management of the frontal sinus and preexisting bone infection and the quality of the overlying soft-tissue cover.     

Use of fast-setting hydroxyapatite cement for secondary craniofacial contouring

Patients who have previously had surgical correction of major craniofacial deformities will often have residual contour deformities they wish to have improved at a later date. The development of hydroxyapatite cement has simplified these procedures. The setting time is reduced to 5 to 8 minutes by mixing the cement with a phosphate-based solution, increasing the tensile strength, and maintaining the same biocompatibility and osseoconductivity. This study includes 48 patients who presented with a variety of residual contour irregularities secondary to a craniofacial congenital anomaly or a posttraumatic defect. All but one of the patients with congenital craniofacial conditions had their initial surgical correction performed by the senior author (Magee) and had regular follow-up visits. Variable amounts of hydroxyapatite cement were used according to the size of the defect to be corrected. Five patients had a postoperative complication: two infections, one seroma, one persistent swelling, and one drain retention. Patients were followed from 6 months to 3 years (mean, 1 year 5 months). Good results were achieved in 38 patients, acceptable results with minor asymmetries were seen in seven patients, and three other patients required a second intervention to obtain a better contour. Cranioplasty with fast-setting hydroxyapatite cement is a simple and reliable procedure, with a low complication rate. Attention to simple technical and operative principles can provide excellent results.     

The biologic behavior of hydroxyapatite implanted into the maxillofacial skeleton

Eleven patients who previously had undergone elective facial osteotomy and in whom blocks of porous hydroxyapatite were implanted into osteotomy gaps later consented to open biopsy of the implant material. A total of 24 biopsies were harvested at a mean time of 10.2 months following implantation. Gross anatomic findings were recorded at the time of biopsy. Specimens were harvested from the zygomatic buttress of the maxilla (12), the piriform buttress of the maxilla (4), the maxillary interdental premolar region (2), and the anterior mandible (6). Histologic sections were examined undecalcified using a modified trichrome stain. Eight of the 11 patients were followed radiographically for a minimum of 24 months. In the absence of infection, there was rapid fibrovascular ingrowth and, provided there was contact with host bone, bone ingrowth. This was observed in 21 of 24 biopsy specimens. The extent of bone ingrowth, as judged qualitatively, was highly variable and did not correlate with the time interval from implantation, anatomic site, or surface area of bone-implant interface. A healing process involving an osteoid phase of bone maturation and suggestive of continued net bone production was consistently found. The gross anatomic, radiographic, and histologic findings are discussed and provide further insight into the biologic behavior of porous block hydroxyapatite implanted into the maxillofacial skeleton.     

Co-loading of bisphosphonates and antibiotics to a biomimetic hydroxyapatite coating

We have incorporated bisphosphonates and antibiotics simultaneously into a biomimetic hydroxyapatite implant coating aiming to use the interaction between drug-molecules and hydroxyapatite to enable local release of the two different substances to obtain a dual biological effect. A sustained release over for 43 h of antibiotics (cephalothin) was achieved without negative interference from the presence of the bisphosphonate (clodronate) which, in turn, successfully bonded to the coating surface. To our knowledge, this is the first study that indicates the possibility to simultaneously incorporate both antibiotics and bisphosphonates to an implant coating, a strategy that is believed to improve implant stability and reduce implant-related infections.     

Addressing the dosimetric impact of bone cement and vertebroplasty in stereotactic body radiation therapy

PurposeBone cement used for vertebroplasty can affect the accuracy on the dose calculation of the radiation therapy treatment. In addition the CT values of high density objects themselves can be misrepresented in kVCT images. The aim of our study is then to propose a streamlined approach for estimating the real density of cement implants used in stereotactic body radiation therapy.MethodsSeveral samples of cement were manufactured and irradiated in order to investigate the impact of their composition on the radiation dose. The validity of the CT conversion method for a range of photon energies was investigated, for the studied samples and on six patients. Calculations and measurements were carried out with various overridden densities and dose prediction algorithms (AXB with dose-to-medium reporting or AAA) in order to find the effective density override.ResultsRelative dose differences of several percent were found between the dose measured and calculated downstream of the implant using an ion chamber and TPS or EPID dosimetry. If the correct density is assigned to the implant, calculations can provide clinically acceptable accuracy (gamma criteria of 3%/2 mm). The use of MV imaging significantly favors the attribution of a correct equivalent density to the implants compared to the use of kVCT images.ConclusionThe porosity and relative density of the various studied implants vary significantly. Bone cement density estimations can be characterized using MV imaging or planar in vivo dosimetry, which could help determining whether errors in dose calculations are due to incorrect densities.     

Bone grafts impregnated with antibiotics as a tool for treating infected implants in orthopedic surgery – one stage revision results

Infection of an orthopedic implant is considered a devastating complication, necessitating its complete removal and thorough debridement of the site. Osseous defects are common in such conditions and need to be addressed before a new implant may be inserted. So far bone grafting has been contraindicated in bacterially contaminated areas and could only be performed as soon as all signs of infection have ceased. Usually long term antibiotic treatment and a multitude of surgical interventions within a period of several months is required until a definitive supply can be achieved. Allograft bone may be impregnated with high loads of antibiotics using special incubation techniques. Based on this technology 48 exchange procedures of infected orthopaedic implants were performed in a single stage, all of them without the use of bone cement. There were 37 infected hips, 8 knees and 3 infected osteosyntheses. Two hips required re-revision because of persisting infection, the remaining 46 patients stayed infect free for a period between 1 and 7 years after surgery. No adverse side effects could be found. Incorporation appeared as after grafting with unimpregnated bone grafts. Antibiotic loaded allograft bone is a powerful tool in septic revision surgery, enabling restoration of bone stock, insertion of a new implant and control of infection in a single operation.     

The influence of nano MgO and BaSO4 particle size additives on properties of PMMA bone cement

A common technique to aid in implant fixation into surrounding bone is to inject bone cement into the space between the implant and surrounding bone. The most common bone cement material used clinically today is poly(methyl methacrylate), or PMMA. Although promising, there are numerous disadvantages of using PMMA in bone fixation applications which has limited its wide spread use. Specifically, the PMMA polymerization reaction is highly exothermic in situ, thus, damaging surrounding bone tissue while curing. In addition, PMMA by itself is not visible using typical medical imaging techniques (such as X-rays required to assess new bone formation surrounding the implant). Lastly, although PMMA does support new bone growth, studies have highlighted decreased osteoblast (bone forming cell) functions on PMMA compared to other common orthopedic coating materials, such as calcium phosphates and hydroxyapatite. For these reasons, the goal of this study was to begin to investigate novel additives to PMMA which can enhance its cytocompatibility properties with osteoblasts, decrease its exothermic reaction when curing, and increase its radiopacity. Results of this study demonstrated that compared to conventional (or micron) equivalents, PMMA with nanoparticles of MgO and BaSO4 reduced harmful exothermic reactions of PMMA during solidification and increased radiopacity, respectively. Moreover, osteoblast adhesion increased on PMMA with nanoparticles of MgO and BaSO4 compared with PMMA alone. This study, thus, suggests that nanoparticles of MgO and BaSO4 should be further studied for improving properties of PMMA for orthopedic applications.     

A three-dimensional non-linear finite element study of the effect of cement-prosthesis debonding in cemented femoral total hip components.

A three-dimensional non-linear finite element analysis of a cemented femoral component in which the component was partially debonded from the cement mantle was used to assess the effects of debonding on stresses in the cement. Three cases of partial cement-metal debonding were modelled with debonding of the proximal portion of the implant down to a horizontal plane which was 35, 62.5, or 82.5 mm below the prosthesis collar. Each situation was studied under loads simulating both gait and stairclimbing. Also, complete debonding between the implant and the surrounding cement mantle was modeled for loads simulating gait. Under stair climbing loads with partial cement-mental debonding, hoop stresses of 13-18 MPa were observed in the cement at the cement-metal interface at the proximal postero-medial corner of the implant. Similarly, in stair climbing, the maximum principal stresses in the cement were also adjacent to the proximal postero-medial region of the implant. These stresses were compressive and increased from 15 MPa with fully bonded interfaces to 48 MPa with debonding down to 82.5 mm below the prosthesis collar. Under gait loads, complete debonding caused high compressive stresses up to 34.9 MPa in the cement distal to the prosthesis tip. Thus, cement failure subsequent to prosthesis debonding is likely in the proximal region in a partially debonded implant due to stair climbing loads and is likely below the prosthesis tip in a fully debonded implant due to gait loading.     

羟基磷灰石义眼台植入联合一期钛钉打孔术的效果研究

目的：探讨国产医用钛钉系统联合改良羟基磷灰石义眼台钛钉打孔术的手术效果。方法：选择32只健康家兔并将其分两组,在球内容摘除术后分别行单纯义眼台植入及义眼台植入联合一期钛钉打孔术,于2、4、6、12w时每组分别处死4只家兔,观察和评价家兔对钛钉的生物耐受性及HA植入物的血管化过程。以动物实验为基础,对87例患者行羟基磷灰石义眼台一期植入联合钛钉打孔术,随访12个月,观察其手术效果及与此术式相关的并发症,总结分析国产医用钛钉系统联合改良羟基磷灰石义眼台钛钉打孔术的手术效果及优点。结果：动物实验显示：一期钛钉植入术未发生钛钉移位、排斥,扫描电镜结果表明：2、4、6、12w时两组HA血管化过程无显著差异,6w时钛钉周围1mm范围内与其完全对应的环行区域内血管化程度没有显著差异。临床实验显示：改良术式与二期打孔术相比,义眼片活动度显著提高（P〈0．01）,差异有统计学意义（P〈0．05）。两组术后肉芽肿的发生率比较无统计学差异（P〉0．05）。结论：一期植入钛钉生物相容性好,改良术式临床效果佳,术后并发症少。     

The response of porous hydroxyapatite to contiguous tissue infection.

Two patients are presented in whom severe clinical infection developed in tissue adjacent to and contiguous with previously implanted blocks of porous hydroxyapatite. Both infections resolved with appropriate antibiotics, debridement, and drainage of infected tissues. Hydroxyapatite blocks were left in situ. This unusually favorable response of an alloplast to infection is attributable to the abundant vascular supply of this porous implant. Although reliable dogma can hardly be concluded from two clinical examples, these experiences suggest that once ingrown, porous hydroxyapatite does not behave in a fashion that is typical of foreign bodies in the midst of infection. For the first time, clinical evidence has been offered to support the experimental data that vascularized hydroxyapatite has the ability to resist infection.     

A 1-year study of osteoinduction in hydroxyapatite-derived biomaterials in an adult sheep model: part II. Bioengineering implants to optimize bone replacement in reconstruction of cranial defects

The present study investigated hydroxyapatite biomaterials implanted in critical-size defects in the calvaria of adult sheep to determine the optimal bioengineering of hydroxyapatite composites to facilitate bone ingrowth into these materials. Five calvarial defects measuring 16.8 mm in diameter were made in each of 10 adult sheep. Three defects were filled with cement paste composites of hydroxyapatite and beta-tricalcium phosphate as follows: (1) 100 percent hydroxyapatite-cement paste, (2) 60 percent hydroxyapatite-cement paste, and (3) 20 percent hydroxyapatite-cement paste. One defect was filled with a ceramic composite containing 60 percent hydroxyapatite-ceramic, and the fifth defect remained unfilled. One year after implantation, the volume of all biomaterials was determined by computed tomography, and porosity and bone replacement were determined using backscatter electron microscopy. Computed tomography-based volumetric assessment 1 year after implantation demonstrated that none of the unfilled cranial defects closed over the 1-year period, confirming that these were critical-size defects. There was a significant increase in volume in both the cement paste and ceramic implants containing 60 percent hydroxyapatite (p < 0.01). There was no significant change in volume of the remaining cement paste biomaterials. Analysis of specimens by backscatter electron microscopy demonstrated mean bone replacement of 4.8 +/- 1.4 percent (mean +/- SEM) in 100 percent hydroxyapatite-cement paste, 11.2 +/- 2.3 percent in 60 percent hydroxyapatite-cement paste, and 28.5 +/- 4.5 percent in 20 percent hydroxyapatite-cement paste. There was an inverse correlation between the concentration of hydroxyapatite and the amount of bone replacement in the cement paste for each composite tested (p < 0.01). Bone replacement in 60 percent hydroxyapatite-ceramic composite (13.6 +/- 2.0 percent) was not significantly different from that in 60 percent hydroxyapatite-cement paste. Of note is that the ceramic composite contained macropores (200 to 300 microm) that did not change in size over the 1-year period. All cement paste composites initially contained micropores (3 to 5 nm), which remained unchanged in 100 percent hydroxyapatite-cement paste. Cement paste implants containing increased tricalcium phosphate demonstrated a corresponding increase in macropores following resorption of the tricalcium phosphate component. Bone replacement occurred within the macropores of these implants. In conclusion, there was no significant bone ingrowth into pure hydroxyapatite-cement paste (Bone Source, Stryker-Leibinger Inc., Dallas, Texas) in the present study. The introduction of macropores in a biomaterial can optimize bone ingrowth for reconstruction of critical-size defects in calvaria. This was demonstrated in both the ceramic composite of hydroxyapatite tested and the cement paste composites of hydroxyapatite by increasing the composition of a rapidly resorbing component such as beta-tricalcium phosphate.     

Finite element analysis of a cemented ceramic femoral component for the assembly situation in total knee arthroplasty]

The femoral components of the total knee replacements are generally made of metal. In contrast, ceramic femoral components promise improved tribological and allergological properties. However, ceramic components present a risk of failure as a result of stress peaks. Stress peaks can be minimised through adequate implant design, proper material composition and optimum force transmission between bone and implant. Thus, the quality of the implant fixation is a crucial factor. The objective of the present study was to analyse the influence of the cement layer thickness on stress states in the ceramic femoral component and in the femur. Two- and three- dimensional finite element analyses of an artificial knee joint with cement layers of different thickness and with an unbalanced cement layer thickness between the ceramic femoral component and the femur were performed. Higher stress regions occurred in the area of force transmission and in the median plane. The maximum calculated stresses were below the accepted tensile strength. Stresses were found to be lower for cement layer thickness of <2.0 mm.     

Characteristics of a population of women with breast implants compared with women seeking other types of plastic surgery

Several previous studies have shown that breast implant patients demonstrate a number of differences compared with the general population. However, studies have not compared patients with breast implants with women receiving other types of plastic surgery, of interest because this latter group has been proposed as a comparison group for assessing the long-term health effects experienced by breast implant patients. Questionnaire data obtained from 7447 breast implant patients and 2203 patients with other types plastic surgery were collected during the course of a retrospective cohort study, to determine whether implant patients demonstrate different characteristics compared with a more restricted group of patients. In contrast to previous investigations that compared implant patients with the general population, distinctive differences with respect to family income, number of pregnancies, alcohol consumption, cigarette smoking, or histories of previous gynecologic operations or operations for benign breast disease were not found. However, implant patients were significantly more likely than other plastic surgery patients to be white, have low levels of education, have early ages at first birth, be thin, and be screened frequently for breast disease. Furthermore, implant patients reported somewhat greater use of exogenous hormones and familial histories of rheumatoid arthritis. These results support the notion that other plastic surgery patients are a more appropriate comparison group than women in the general population for studies of the health effects of breast implants; however, there continue to be distinctive characteristics possessed by breast implant patients, which need to be taken into account in an assessment of what disease effects can be uniquely attributed to silicone breast implants.     

Importance of electroroentengography and fluorography in the detection of bronchiectatic disease

During mass screening of population 54 patients were detected with suspected bronchiectatic disease. Photoroentgenography and electroroentgenography were performed in all of them, in 36 of them simultaneously with subsequent bronchography. On electroroentgenograms cellular deformity in the decreased lung, the presence of cellular and linear lucidity of bronchiectasia against a background of a gas-bubble of the stomach were referred to as signs of bronchiectatic disease. Signs of inflammatory exacerbation and symptoms of lung emphysema were revealed on photoroentgenograms as an addition to electroroentgenographic findings. Combined electrophotoroentgenography with subsequent bronchographic verification of the spread of changes is recommended in suspected bronchiectatic disease.     

Trilucent breast implants: voluntary removal following the Medical Device Agency recommendation. Report on 115 consecutive patients

In June of 2000, the U.K. Medical Device Agency recommended the removal of Trilucent implants as a precautionary maneuver in response to reports of local inflammatory reactions. This decision allowed the authors to operate on 115 consecutive patients between June of 2000 and January of 2001. On the preoperative examination, the authors found a very high incidence of rippling (66 percent), whereas capsular contracture was seen in only three patients (2.6 percent). Rippling was significantly more common in patients with subglandular implants. Five implants were found ruptured during the operation. This figure, together with the relative ease of implant breakage at removal, shows a premature deterioration of the implant shell. The authors also comment on implant bleeding, which seems common in this type of breast implant. The authors think that this is a possible cause for the rippling phenomenon, resulting from a reduction of the implant content. On the basis of these findings, the authors conclude that Trilucent implants are associated with a poor cosmetic outcome and a high rate of complications.