Stem Implantation Research Articles

Optimizing the Clinical Fit of Auditory Brain Stem Implants

To develop and implement a new audiological fitting procedure for auditory brain stem implants (ABIs), based on an efficient algorithm, and to compare it with two procedures presently used in clinical practice. First, the different procedures were compared by using computer models and simulations with normal-hearing subjects (N = 4). This allows for an analysis of the accuracy of the procedures in a way that is not possible when testing ABI users. The root-mean-square error between the order estimated by the procedure and the true order was calculated. In addition, ABI users (N = 2) were tested with the new procedure to see if it could be successfully applied in clinic. The degree of variability of their results across runs and sessions was analyzed. The tests of the normal-hearing subjects showed that our proposed procedure required significantly fewer trials (22 on average) than procedures presently used in clinic (with 76 and 234 trials on average for the two other procedures tested) to produce the same degree of accuracy. Computer modeling also demonstrated this advantage. Additional testing showed this advantage was maintained under a variety of conditions relevant to the clinic. The two patients tested were able to use this procedure with success, even though they were poor at discriminating the pitch of electrodes. The patients showed results consistent with having about 4 to 5 discriminable groups of electrodes with the 12 to 14 electrodes tested. The proposed procedure requires fewer trials to produce a clinically useful result and is well tolerated in the clinic. An additional advantage is that it allows testing to be broken down into several "blocks," each containing a small number of trials. If the variability between blocks is small, information can be combined across blocks to increase the accuracy of the result. If the variability is large, perhaps between blocks on different days, this may reflect a significant change in the percepts generated by the implant, and signal to the clinician that a significant alteration in the fitting is required. We recommend its use in ABI user fitting and in cochlear implant fitting when pitch ranking is problematic.

Time saving during acrylic bone cement setting in femoral stem implantation of hip arthroplasty: A prospective, double-blind, randomised study

In order to reduce the final stages of cementing time and intra-operative time, we analysed the behaviour pattern of a quick-setting cement. Quick-setting cement permits easy and adequate manipulation, which reduces surgical time and also the technical problems caused by waiting for setting to be completed. In order to verify the efficacy of faster cement, a double-blind randomised study was carried out comparing a type of traditional cement with quick-setting cement. Two groups of 20 patients were compared. The results show that the fast cement reduces setting time by an average of one minute and 55 seconds (p < 0.01) and presents similar manipulation characteristics to those of conventional cement. (Hip International 2005; 15: 143-8).

Surface arthroplasty in shoulder arthritis

Use of a resurfacing arthroplasty in shoulder arthritis has the advantage of bone preservation. It diminishes the risk of periprosthetic fractures of the humeral shaft by avoiding the stress concentration effect associated with stemmed implants. Revision or, when rarely needed, arthrodesis may be undertaken more easily since the bone stock has been maintained. The largest studies to date have concluded that the indications for this surface replacement are the same as those for the conventional stemmed prostheses, namely osteoarthritis, rheumatoid arthritis, avascular necrosis, instability arthropathy, posttraumatic arthropathy, and cuff arthropathy. The best results have been achieved in primary osteoarthritis. Results for other indications are comparable with those for stemmed prostheses with a similar follow-up and case mix. Use in cuff tear arthropathy has yielded successful outcomes consistent with the limited goals in these patients, similar to those with use of available stemmed implants but with technical advantages. The implant is not suitable where the humeral head is insufficient or in four-part fractures. In such cases, a stemmed implant should be used. Access to the glenoid is more difficult with this technique because of humeral head retention resulting in a greater propensity to perform hemiarthroplasty.

Insertion of an expandable cement restrictor reduces intramedullary fat displacement

The insertion of an intramedullary cement restrictor can lead to the same pathophysiologic reactions that are well described as fat embolism syndrome after cement and stem implantation. Fat and marrow are forced into the draining veins of the femur. In this study, we compared the extrusion of intramedullary contents produced by the insertion of a commonly used gelatin (Biostop G/IMSET) and a new expandable cement restrictor (REX Cement Stop) in 7 paired, fresh-frozen femora. A further 9 pairs were used to evaluate the function of a custom-made application instrument, which allowed for suction during plug (Biostop G/IMSET) insertion. The oversized restrictor produced, on average, twice as much fat as the expandable restrictor ( P = 0.0156). The gelatin plug with additional suction was not associated with reduced fat extrusion, because the suction device in its current design failed because of obstruction in most cases. The expandable restrictor showed favorable characteristics and has the potential to reduce the risk of fat embolism.

Treatment of periprosthetic femoral fractures associated with total hip arthroplasty

Periprosthetic femoral fractures represent a heterogeneous type of injury with a variety of treatment options. By retrospectively analysing our data, the results of different therapeutic procedures are compared and, reviewing previously published cases, suggestions for the management have also been developed. This study is based on the analysis of records and radiograph series of 43 patients (50 procedures) with periprosthetic fractures. 22 patients could be followed-up using the Harris Hip Score at an average of 4.8 years after injury. Factors predisposing to fractures were found in 41 patients, only 9 fractures were due to an adequate trauma. According to the classification of Johansson et al., 15 fractures of type I and type II each and 20 fractures of type III were treated. In 23 cases open reduction and internal fixation (ORIF) with a plate was used, 10 fractures were stabilised by minimal osteosynthesis, in 8 cases a modular prosthesis for bone replacement was used, 6 times a revison stem was implanted, and in 2 fractures osteosynthesis of the femur could only be accomplished after the complete removal of implants. The mean Harris Hip Score was 69.9 points at the follow-up examination. Local surgical complications were more often observed than general. Due to their different clinical presentations periprosthetic fractures need to be managed individually and in most cases operatively. Internal fixation with a plate proved to give the best functional results for stable stem implants. Loosening stems have to be replaced by revision implants with long stems for intramedullary fixation. Alternative osteosynthetic techniques and additive minimal osteosynthesis can be favoured in special cases. Modular prostheses for bone replacement are reserved for fractures with extensive bone loss.

Die Therapie der Schenkelhalsfraktur beim alten Menschen: Komplikationen nach operativer Versorgung

Einleitung: Schenkelhalsfrakturen beim alten Menschen sind an größeren unfallchirurgischen Kliniken mittlerweile tägliche Routine. Ob die Indikation zum Hüftgelenkersatz oder zur Osteosynthese besteht, ergibt sich aus dem biologischen Alter des Patienten und dem Frakturtyp. Material und Methoden: In einem Zeitraum von 6,5 Jahren (1/96 bis 6/02) wurden an unserer Klinik 452 ältere Patienten (Alter > 64 Jahre, Median 82 Jahre) mit einer Schenkelhalsfraktur (80 % medial, 20 % lateral) operativ versorgt. Von diesen erhielten 389 primär eine prothetische Versorgung (250 Totalendoprothesen, 139 Duokopfprothesen), die übrigen 63, vorwiegend lateralen Frakturen wurden osteosynthetisch (44 × dynamische Hüftschraube, 19 × Schraubenosteosynthese) versorgt. Alle Komplikationen wurden prospektiv erfasst. Ergebnisse: Die Komplikationsrate beim endoprothetischen Hüftgelenksersatz war gering. 31 Patienten (von 389) erlitten 35 Komplikationen. Bei der Primärversorgung erlitten 2 Patienten eine Schaftsprengung. Postoperativ kam es bei 20 Patienten zu einer Prothesenluxation, Reluxationen fanden sich dann im weiteren Verlauf bei 11 (der 20) Patienten, 4 mussten mittelfristig reoperiert werden. 7 Hämatome/Serome und 3 Infekte mussten operativ revidiert werden. Lediglich 3 Patienten (93, 96 und 97 Jahre alt) verstarben innerhalb der ersten beiden Wochen postoperativ. Bei den 63 osteosynthetisch versorgten Patienten musste bei 4 Patienten im weiteren Verlauf bei Ausbruch der Implantate eine Prothese implantiert werden. Bis zu 80 % der Patienten waren im weiteren Verlauf gehfähig, davon gut die Hälfte alleine oder mit fremder Hilfe außerhalb des Hauses. 15 % der Patienten waren im Rollstuhl mobilisierbar, lediglich weniger als 5 % blieben auf Dauer bettlägerig. Fazit: Bei den instabilen Schenkelhalsfrakturen des älteren Patienten ist der endoprothetische Ersatz in zementierter Technik die Methode der Wahl. Die Indikation zur osteosynthetischen Versorgung ist nur gegeben, wenn postoperativ eine Vollbelastung erlaubt werden kann.

Photoelastic and thermoelastic measurement of stress on the proximal femur before and after implantation of a hip prosthesis with retention of the femoral neck.

This study demonstrated the improved medial support and the transfer of load onto the retained neck of the femur using seven fresh frozen femurs. Results confirm the reliability of the thermoelastic stress analysis method, which is comparable to the photoelastic surface coating method, but with greater sensitivity. The loading pattern after stem implantation shows a homogeneous transfer of force onto the preserved femoral neck. After femoral neck removal, an inhomogeneous increase of the intertrochanteric compression loading was observed. Therefore, improved biomechanical conditions are created for a permanently stable implantation of stem prostheses with retention of the femoral neck.

Skull base trauma: Diagnosis and management

The singular anatomical relationship of the base of the skull is responsible for the particular problems that may arise after injury. Extensive dural laceration and severe neurovascular damage may accompany skull base injuries. Trauma to the anterior skull base is frequently related to the paranasal sinuses, and trauma to the middle and the posterior skull base usually affects the petrous bone. Injury to the anterior fossa including the paranasal sinuses may produce CSF leakage, damage the olfactory nerves, optic nerves, and orbita contents. Fractures may affect the carotid canal, injure the internal carotid artery and result in carotid-cavernous fistula. Trauma to the petrous bone may cause facial palsy and deafness, and CSF leakage with otorrhoea or paradoxal rhinoliquorrhoea. Trauma to the posterior fossa may lacerate the major venous sinuses, and affect the cranio-cervical stability. Each one of these injuries will need a particular strategy. Decision making for management as a whole must consider all aspects, including the fact that these injuries frequently involve polytraumatized patients. Decisions regarding the timing of surgery and the sequence of the surgical procedures must be made with great care. Modern surgical techniques and recent technologies including functional preservation of the olfactory nerves in frontobasal trauma, visual evoked potentials, assisted optic nerve decompression, facial nerve reconstruction, interventional technique for intravascular repair of vascular injuries, and recent developments in cochlea implants and brain stem implants, all contributed significantly to improve outcome and enhance the quality of life of patients. This article reviews basic principles of management of skull base trauma stressing the role of these advanced techniques. [Neurol Res 2002; 24: 147-156]

Rehabilitation of hearing and communication functions in patients with NF2.

Most patients with neurofibromatosis type 2 (NF2) lose hearing either spontaneously or after removal of their neurofibromas. The patient may benefit from conventional hearing aids if, due to modern microsurgery and intraoperative monitoring the integrity of the cochlea and the 8th nerve is preserved. With lost auditory function but preserved electrical stimulibility of the 8th nerve a cochlear implant may be appropriate. But if the patients have no remaining 8th nerve to stimulate, there is no benefit from cochlear implants. Until some years ago, vibrotactile aids, lip-reading, and sign language have been the only communication modes available to these patients. With auditory brain stem implants it is now possible to bypass both the cochlea and the 8th nerve and to stimulate the cochlear nucleus directly. Stimulation of the devices produces useful auditory sensations in almost all patients. Testing of perceptual performance indicated significant benefit from the device for communication purposes, including sound-only sentence recognition scores and the ability to converse on the telephone. Also lip-reading is significantly improved with brain stem implants. The successful work of an auditory brainstem program center depends very much on the close interdisciplinary collaboration between the Departments of Neurosurgery and ENT-surgery. In the future new developments like speech processing strategies and new designed electrodes accessing the complex tonotopic organization of the cochlear nucleus may further improve rehabilitation in these patients who would have been deaf some years ago.

Results of operative therapy of periprosthetic femur shaft fractures in total hip endoprostheses

Periprosthetic femoral shaft fracture represents an uncommon but potentially devastating complication associated with total hip arthroplasty. The treatment should result in complete union of the fracture and at the same time guarantee stability of the implant. 15 patients treated between 1992 to 1998 were analysed. Clinical and radiographic follow-up averaged 30 months (6-79 months) in 13 cases. Two patients died regardless of the fracture. The method of treatment depended on the intraoperative stability of the prosthesis and in addition on the fracture type (Bethea). In 5 cases of intraoperative stability of the prosthesis plate fixation was performed. Plate fixation was complicated by fixation failure combined with a recurrent fracture in two cases leading to shift to a long stem prosthesis. Ten cases of fractures associated with loose stems were treated with a new prosthesis using a long stem system. In these cases an uncomplicated healing of the fracture was achieved with adequate stability in radiographic examinations. The average Harris score was 70 (26-93). For fractures near the femoral stem or in case of implant loosening we recommend the shift to a long stem prosthesis. Also in fractures distally from the femoral stem tip we prefer now long stem implants rather than plate fixation to avoid large exposure of the femoral shaft and resultant complications.

Advantages of the Retrosigmoid Approach in Auditory Brain Stem Implantation

From April 1997 to December 1999, six patients (five men and one woman), ranging in age from 22 to 37 years with neurofibromatosis type 2 (NF2) were operated on via the classic retrosigmoid-transmental (RS-TM) approach for removal of a vestibular schwannoma (VS) (tumor size from 12 to 40 mm) and for auditory brain stem implantation (ABI). After tumor removal, the floor of the lateral recess of the fourth ventricle and the convolution of the dorsal cochlear nucleos were reached, and the ABI was inserted. More recently, an ABI was implanted via the retrosigmoid approach in a 4-year-old boy with a cochlear malformation (common cavity) associated with cochlear nerve aplasia. Electrically evoked auditory brain stem responses (EABRs) and neural response telemetry (NRT) were performed to verify the correct positioning of the inserted electrodes. No major complications related to ABI were observed. ABI has been activated to date in five of the NF2 patients. Auditory sensations with various numbers of electrodes were evoked in all patients. We consider the RS-TM approach the route of choice for ABI insertion in patients with NF2 and good hearing, offering a chance of hearing preservation, and in patients with complete cochlear ossification, severe head trauma and cochlear fracture, or nerve disruption, or a combination of these. A new indication for ABI implantation via the RS approach is presented by patients with bilateral cochlear nerve aplasia.

Effect of surgical technique and use of a rigid centralizing device on stem positioning and geometric reconstruction in the sagittal plane during total hip replacement in canine cadavers

Abstract Objective To determine the effect of surgical technique and use of a rigid centralizing device on stem positioning and geometric reconstruction in the sagittal plane during total hip replacement in dogs. Sample Population Bilateral femurs from 8 adult mixed-breed canine cadavers. Procedure Femurs were prepared for femoral stem implantation, using 4 variations in technique. Proximal femoral reconstruction and femoral stem positioning were evaluated on radiographs. Results Implants evaluated in this study accurately reconstructed displacement of the femoral head of the intact canine femur in the sagittal plane. Centralization of the distal aspect of the stem was optimized by use of an undersized femoral stem. Ostectomy at the level of the lesser trochanter resulted in the smallest diaphysis-to-implant angle. Anteversion and retroversion of implants significantly decreased the distance between the distal tip of the implant and the adjacent cortex, compared with normoversion. The centralizing device significantly increased the minimum distance between the distal tip of the implant and adjacent cortex but did not improve the odds of actually centralizing the tip of the implant. Conclusions and Clinical Relevance Malpositioning of implants in the sagittal plane may be minimized through ostectomy at the lesser trochanter and use of an undersized implant positioned in normoversion. Use of a polymethylmethacrylate centralizing device will help eliminate contact between the implant tip and adjacent cortex. Implantation of an undersized femoral component, avoidance of substantial anteversion or retroversion, and use of a rigid centralizing device are recommended when using the prosthesis described-for total hip replacement of dogs. (Am J Vet Res 1999;60:1126–1135)

Peripheral Pulmonary Artery Stenosis: Acute and Mid‐term Results of High Pressure Balloon Angioplasty

Surgical angioplasty for branch pulmonary arterial stenosis (BPAS) is associated with a low success rate and a high mortality rate. The success rate of balloon angioplasty using low pressure balloon catheters is about 60%. Little data are available on the success rate using high‐pressure balloon (HPB) catheters. Therefore, our goal is to report the procedural and mid‐term success rates using HPB catheters for the treatment of BPAS and those factors associated with success. 38 patients (25 boys/13 girls) with BPAS underwent at least one attempt (48 procedures) of balloon angioplasty using HPB catheters. Their median age was 1.1 years (range, 0.1–22.1 year), and their median weight was 9.6 kg (range, 3.7–61 kg). Thirty patients (79%) had BPAS following surgical intervention for their cardiac defects (mostly post tetralogy of Fallot), and eight (21%) patients had the BPAS associated with Williams syndrome (2 patients), Alagille syndrome (one patient), unoperated tetralogy of Fallot (one patient), and congenital BPAS (4 patients). Twenty‐six procedures involved the left pulmonary artery (LPA), and 22 procedures involved the right pulmonary artery (RPA). The overall acute success rate was 56% (27 of 48 vessels). The mean ± SD of the gradient across the stenotic segment decreased from 37 ± 20 to 23 ± 20 mmHg (P &lt; 0.001), and the diameter of the narrowest segment improved from 3.5 ± 1.6 to 5.7 ± 2.5 mm (P &lt; 0.001). The median RV/AO pressure ratio decreased from 0.64 to 0.52 (P = 0.009). The median ratio of balloon size to the diameter of the narrowest segment was 2.67 (range, 1.3–7.8). Lesion location (RPA) was associated with higher acute success rate (P = 0.03), but not with mid‐term outcome. Acute (P = 0.006) and mid‐term (P = 0.04) success were related to balloon diameter to vessel diameter ratio. At mid‐term follow‐up (median interval 2.5 years), 16 vessels (33%) were widely patent. Complications included perforation of a small branch pulmonary artery in one patient, resulting in hemoptysis with complete recovery. One patient developed pulmonary artery hypertension; two patients developed an aneurysm of the dilated segment; one patient developed femoral vein thrombosis; and one patient had a paradoxical embolus associated with a cerbrovascular accident. There were no procedure‐related deaths. We conclude that BPAS is challenging to treat. The use of HPB angioplasty may avoid surgery or the permanence of stem implantation and should be the first intervention for this condition in the pediatric patient. Other interventions should be reserved for refractory stenosis.

The Effect of Tibial Stem Design on Component Micromotion in Knee Arthroplasty

Rigid body mechanics with computer data acquisition and analysis techniques were used to determine the three-dimensional motions of any point on the tibial component of a total knee arthroplasty. Three stem configurations were compared: (1) no stem; (2) short stem (40 mm); and (3) long stem (75 mm). In addition, three loading conditions were analyzed for each stem configuration: (1) central loading; (2) posterior loading; and (3) medial loading. The longer stem implants were associated with increased micromotion, especially under eccentric loading. Cemented implants seemed to have more stable fixation, compared with noncemented implants. It was thought that the increased motion was secondary to a toggling of the implant under load, secondary to uneven medullary cortical contact. Overall, the results indicated that short and long stems do not enhance initial fixation with cemented or cementless implantation in routine knee arthroplasty.

Antiplatelet Versus Warfarin Therapy: Platelet, Neutrophil, and Thrombus Deposition for Intracoronary Stents in a Porcine Model

Antiplatelet therapy may offer an advantage over warfarin in reducing adverse clinical events after intracoronary stem implantation. The mechanism of this effect has not been elucidated but platelet adhesion may play a predominant role in the process of subacute stent thrombosis. This study compared the effect on platelet, neutrophil, and thrombus deposition of three different anticoagulation regimens (aspirin/warfarin vs aspirin/ticlopidine vs aspirin alone) after intracoronary stenting in juvenile swine. Thirty stents were deployed in 15 juvenile farm swine randomized to one of 3 anticoagulation protocols: aspirin 325 mg/day; aspirin 325 mg/day and ticlopidine 500 mg/day; aspirin 325 mg/day and warfarin 0.1 mg/kg/day. Autologous platelets were labeled using 111Indium‐oxime and a slotted tube metal stent was deployed using a high pressure balloon. Platelet deposition in the stented segment was determined at 24 hours. Each segment was analyzed by light microscopy to document an injury score; mean and maximum thrombus deposition per strut were measured; and neutrophils were counted on each metal strut and in the vessel wall. Platelet deposition at 24 hours was significantly higher in the aspirin/warfarin group (3.69 ± 1.16 ± 108 plts/cm2) than in the aspirin/ticlopidine (1.74 ± 0.45 ± 108 plts/cm2, P = 0.0009) or aspirin (2.42 ± 2.13 ± 108 plts/cm2, P = 0.03) groups. There was no significant difference between the aspirin and aspirin/ticlopidine groups (P = 0.9). Mean thrombus area per strut was significantly greater in the aspirin/warfarin group (0.027 ± 0.006 mm2) compared to the aspirin/ticlopidine group (0.017 ± 0.002 mm2, P = 0.002). The majority of the thrombus (79%) but minority of neutrophils (24%) were found on the stent struts. In this coronary stent model, warfarin given with aspirin was associated with greater thrombogenicity and more platelet deposition than either aspirin/ticlopidine or aspirin alone.

In‐Hospital Results of the Wiktor Stent in Acute Myocardial Infarction

Background: Coronary angioplasty has been established as the preferred method of treatment for patients with acute myocardial infarction when they are admitted to a hospital with skilled interventional cardiologists and personnel well‐trained in cardiac catheterization techniques. Nevertheless, the possibilities of artery reocclusion, recurrent ischemia, and high rates of late restenosis have made some investigators believe that coronary stenting could be a better mechanical reperfusion technique than conventional balloon angioplasty. Methods: We reviewed the in‐hospital results of patients who received a Wiktor coronary stent implant during primary or rescue angioplasty for acute myocardial infarction within 6 hours of either the onset of pain or the recurrence of symptoms after thrombolytic administration. We excluded patients in shock and those whose symptoms were produced by an acute occlusion after an angioplasty procedure. Quantitative coronary analysis of the lesions treated were performed by automatic border detection using the on‐line DCI system by Phillips or off‐line CMS system by Medis. Results: Thirty‐three patients, aged 59 ± 13 years (79% male), received one or more coronary stents (41 stents were implanted) for treatment of acute myocardial infarction during primary angioplasty (30) or rescue angioplasty (3) after the onset of symptoms. Twenty‐nine of the patients were in Killip Class I (patients in shock were excluded). The infarct related artery was the left anterior descending in 19 patients (58%), the right coronary artery in 12 (36%), and the left circumflex in 2 (6%). Twenty‐seven patients (82%) had TIMI 0‐1 flow on the initial angiography. After stent implantation 100% of the patients had TIMI III (85%) or TIMI II (15%) flow. The minimal luminal diameter of the infarct related artery increased from 0.22 ± 0.38 mm before the procedure to 2.99 ± 0.48 mm after stem implantation. Most of the patients (27 [84%]) received antiaggregation therapy‐after the procedure. There was no mortality or reinfarction, although one patient had an embolic stroke. There were no cases of acute or subacute thrombosis of the stent. Conclusion: Use of the Wiktor stent during angioplasty for acute myocardial infarction is followed by immediate angiographic and in‐hospital clinical results comparable to results obtained with other types of stent. This stent is particularly useful in curved lesions and those with an important collateral branch arising from the lesion. If the angiographic result is optimal, the patient can be managed with antiaggregant therapy after stent implantation.

Reinforcement of PMMA bone cement with a continuous wire coil – a canine femur study

The hoop and axial strains present due to loading after femoral stem implantation in canine femurs, implanted with and without a wire coil surrounding the distal tip were investigated. One stem served as the control without wire coil while the other was experimental reinforced with a wire coil. Both stems were implanted by identical methods. Ideally, the wire coil should serve to reduce the hoop and axial strains present in the distal tip of the arthroplasty. The strains were measured using 90 degrees rosette strain gages. Though the coil's position was altered slightly during implantation usable results were still obtained. At a maximum load of 44.5 N there were 32 and 19% reduction in the hoop and axial strains for the reinforced stem and the control, respectively. This experiment presents a striking difference between the control and reinforced hip arthroplasties. Equally important is that this study confirms the trends in hoop and axial strain behavior demonstrated in other works utilizing a wire coil reinforcement scheme. The simple method of applying a continuous wire coil may help to reduce the loosening of femoral stem of total hip arthroplasty by reducing strains at the tip of the stem due to the strengthening of the cement mantle.

Biomechanical and histological analysis of an HA coated, arc deposited CPTi canine hip prosthesis.

The interfacial shear strength and bone tissue response was investigated for an arc deposited (AD) commercially pure titanium implant surface, with (AD/HA) and without (AD) plasma-sprayed hydroxyapatite (HA) coating. Ten purpose bred coonhounds received bilateral femoral stem implantation (AD and AD/HA) in the proximal femurs (hemiarthroplasty). The femoral prosthesis consisted of a modular CoCr alloy head, modular Ti-6Al-4V neck, and a 10-mm diameter cylindrical Ti-6Al-4V femoral stem. The AD surface had 30-35% greater surface roughness than the AD/HA surface. The HA coating had a purity greater than 90% and a crystallinity greater than 65%. After 6, 12, and 24 weeks, the implants were retrieved and analyzed with mechanical testing, qualitative and quantitative histology, and electron microscopy. The AD/HA implants had equivalent interfacial shear strengths to the AD implants at all time periods. The AD/HA implants had significantly greater linear bone contact than the AD implants. The 6-week implants had significantly thicker cortical bone than the 12- and 24-week implants. The HA coating was very stable in vivo, evidenced by no thickness reduction at any time period. Qualitatively, the AD/HA implants primarily had bone contacting the implant surface with little fibrous tissue present, and the AD implants had bone and fibrous tissue contacting the implant surface. The electron microscopy analysis showed that the mechanically tested implants exhibited a mixed failure mode at the bone, HA coating, and titanium interfaces.

Suppression of Leafminer (Coleoptera: Buprestidae) Populations on Turkey Oak (Fagaceae) Using Implants of Acephate

Herbivory by leafmining insects is notoriously difficult to manipulate for ecological studies because eggs and larvae generally cannot be moved easily among plants without damaging plant tissue and killing larvae. We report on the effectiveness of stem implants of acephate (O,S dimethyl acetylphosphoramidothioate)for protecting turkey oak, Quercus laevis Walter,foliage from leafminer, Brachys tesselatus F., herbivory. Implanting acephate capsules into the stem of turkey oak trees before budbreak significantly reduced overall leafminer damage (both adult foliage feeding and larval mining) without any evident negative effects on tree acorn production (number and weight of acorns). This technique is currently being used to examine long–term costs of leafminer herbivory on growth and reproduction of turkey oak. It is likely that a similar approach can be used to manipulate leafminer densities for ecological studies on other tree species, as has been shown for herbivores on conifers and numerous crop species.

Effectiveness of acephate implants in protecting cones from insect damage in some conifer forests of Northeastern China

Stem implants of acephate were tentatively used to control cone and seed insects in Northeastern China in 1993. Experiments considered in a Siberian larch seed orchard and mother-tree stands of Korean pine and Korean spruce that promising control of major cone pests, including cone flies, cone-worms and seed-worms, was obtained in all of the conifer species but treatment did not reduce significantly damage due to seed chalcids. Acephate implants did not seem to affect seed germination.