Comparison of bone screw holding strength in healthy bovine and osteoporotic human cancellous bone

Surgical Considerations for Osteoporosis, Osteopenia, and Vitamin D Deficiency in Upper Extremity Surgery

Fragility fractures as a result of osteoporosis, osteopenia, or vitamin D deficiency are some of the most common injuries encountered in orthopedics and require careful consideration when determining the appropriate management and treatment options. A thorough perioperative evaluation can identify causes of low bone mineral density allowing for initiation of appropriate therapy. Surgical treatment of these fractures can be difficult, and techniques should be employed to ensure stable fixation. It is important to understand the potential pitfalls associated with treatment of fragility fractures to prevent avoidable complications. Postoperative management is key to preventing future injuries in this unique patient population.

Charcot Neuroarthropathy: Current Surgical Management and Update. A Systematic Review

Background

Charcot neuroarthropathy of the ankle and the hindfoot is a complex clinical entity with a high risk of amputation. Charcot neuroarthropathy limb reconstruction has been proposed as a limb-salvaging procedure. However, there was a lack of information on the various available reconstruction methods, including the outcomes and complications. The present study aimed to evaluate the current literature and update on the trends regarding the surgical management of Charcot neuroarthropathy of the ankle and the hindfoot.

Methods

All data published from January 2010 to January 2020 that investigated the methods of fixation and their respective outcomes for the surgical reconstruction in Charcot neuroarthropathy were analyzed. The union rate, amputation rates, and complications associated with these techniques were taken for statistical analysis.

Results

A total of 16 studies fit the inclusion criteria of this study, with four Level-III studies and 12 Level-IV studies were included. Ten studies utilized internal fixation only; five used a combination of internal fixation and circular external fixator, whereby there are three comparative studies between internal and external fixations, and two studies applied combined technique of internal and external fixations (hybrid fixation). One study describes the usage of circular external fixation only.

Conclusions

The use of retrograde intramedullary nail as a treatment of choice in the reconstruction of Charcot neuroarthropathy ankle is recommended before an ulcer occurrence. Hydroxyapatite (HA)- coated screws are recommended for the locking mechanism to prevent migration in Charcot neuroarthropathy due to poor bony quality. Hybrid fixation is recommended for reconstruction in a condition of ulceration and more complex deformity as it provides a higher rate of limb salvage with less soft tissue irritation.

Biomechanics of Osteoporotic Fracture Care: Advances in Locking Plate and Intramedullary Nail Technology

Osteoporotic fractures are extremely common and will continue to increase. Methods of internal fixation must address challenges presented by architectural changes of weakened bone. The goals of surgery are to provide mechanically stable internal fixation with minimal biologic insult that provides rapid rehabilitation and early mobilization. Novel techniques and technology that reinforce preservation of periosteal blood supply and utilization of biomechanically stable constructs diminish failure rates. Advents in locking plate technology, intramedullary nail designs, bone augmentation, and multiple implant constructs maximize strength while mitigating axial, torsional, and bending failure modes to provide optimal patient outcomes.

Measurement of Scaphoid Bone Microarchitecture: A Computed Tomography Imaging Study and Implications for Screw Placement

PURPOSE

High bone density and quality is associated with improved screw fixation in fracture fixation. The objective of this study was to assess bone density and quality in the proximal and distal scaphoid to determine optimum sites for placement of 2 screws in scaphoid fracture fixation.

METHODS

Twenty-nine cadaveric human scaphoid specimens were harvested and scanned using micro-computed tomography. Bone density (bone volume fraction) and bone quality (relative bone surface area, trabecular number, and trabecular thickness) were evaluated in 4 quadrants within each of the proximal and distal scaphoid.

RESULTS

The proximal radial quadrant of the scaphoid had significantly greater bone volume than the distal ulnar (mean difference, 33.2%) and distal volar quadrants (mean difference, 32.3%). There was a significantly greater trabecular number in the proximal radial quadrant than in the distal ulnar (mean difference, 16.7%) and in the distal volar quadrants (mean difference, 15.9%) and between the proximal ulnar and the distal ulnar quadrants (mean difference, 12%). There was a significantly greater bone surface area in the proximal radial and distal radial quadrants than in the distal ulnar and distal volar quadrants. There were no significant differences in trabecular thickness between the 8 analyzed quadrants CONCLUSIONS: Although there are differences in bone volume, trabecular number, and bone surface area between the proximal pole of the scaphoid and that of the distal pole, there were no significant differences in the bone quality (trabecular thickness, trabecular number, and relative bone surface area) and density (bone volume fraction) between the 4 quadrants of the proximal or distal pole of the cadaveric scaphoids studied.

CLINICAL RELEVANCE

Insertion of 2 headless compression screws can be determined by ease of surgical access and ease of screw positioning and not by differences in bone quality or density of the proximal or distal scaphoid.

Locked Plating and Advanced Augmentation Techniques in Osteoporotic Fractures

"The incidence of osteoporotic fracture is increasing with the aging US population. Because osteoporosis leads to a decrease in bone mineral density with a decrease in both trabecular and cortical bones, osteoporotic fracture presents fixation challenges with standard plate and screw constructs. Locked plating has been developed to create a fixed-angle plate-screw construct that is more resistant to failure in osteoporotic bone. Endosteal replacement, additional plates, and cement augmentation have all been demonstrated to further supplement osteoporotic fracture fixation. Technologies on the horizon to treat osteoporotic fracture include SMV screws, hydroxyapatite-coated implants, and far cortical locking screws."

The effect of screw trajectory for the reduction and association of the scaphoid and lunate (RASL) procedure: a biomechanical analysis

The purpose of this study was to determine if screw placement in the reduction and association of the scaphoid and the lunate (RASL) procedure affected the ability of the scapholunate joint to withstand force. After completely disrupting of the scapholunate ligament in 29 fresh-frozen cadaveric wrists, we placed the RASL screw either distal or proximal to the lateral aspect of the dorsal ridge of the scaphoid and into the dorsal or volar aspect of the lunate. Specimens were subjected to repeated cycles of transcarpal axial force, mimicking clenched-fist loading, until failure. Screw placement distal to the lateral aspect of the dorsal scaphoid ridge was significantly associated with failure when examined manually, radiographically (1.8 vs. 0.5 mm) and using real-time motion capture (diastasis: 1.6 vs. 0.4 mm; Euler angle: 4.5 ° vs. 0.8 °). The lateral aspect of the dorsal ridge is a reliable radiographic landmark on the scaphoid and provides surgeons with a convenient starting point to achieve the most biomechanically stable RASL construct, and, therefore, enhances the potential for an optimal clinical outcome.

Clinical Management of Osteoporotic Fractures

PURPOSE OF REVIEW

This review examines recent literature regarding the clinical management of fragility fractures, provides insight into new practice patterns, and discusses controversies in current management.

RECENT FINDINGS

There are declining rates of osteoporosis management following initial fragility fracture. Management of osteoporotic fractures via a multidisciplinary team reduces secondary fracture incidence and improves overall osteoporotic care. Anabolic agents (abaloparatide and teriparatide) are effective adjuvants to fracture repair, and have shown positive results in cases of re-fracture in spite of medical management (i.e., bisphosphonates). For AO 31-A1 and A2 intertrochanteric hip fractures (non-reverse obliquity), no clinical advantage of intramedullary fixation over the sliding hip screw (SHS) has been proven; SHS is more cost-effective. As fragility fracture incidence continues to rise, orthopedic surgeons must play a more central role in the care of osteoporotic patients. Initiation of pharmacologic intervention is key to preventing subsequent fragility fractures, and may play a supportive role in initial fracture healing. While the media bombards patients with complications of medical therapy (atypical femur fractures, osteonecrosis of jaw, myocardial infarction), providers need to understand and communicate the low incidence of these complications compared with consequences of not initiating medical therapy.

Combined Percutaneous Iliosacral Screw Fixation With Sacroplasty Using Resorbable Calcium Phosphate Cement for Osteoporotic Pelvic Fractures Requiring Surgery

Osteoporotic sacral fractures, including acute and chronic insufficiency fractures, are increasing in frequency and present a number of management problem. Many of these patients are treated nonoperatively with relative immobility (eg, bedrest, wheelchair, or weight-bearing restrictions) and analgesics, which likely make the osteoporotic component worse. Surgery in this patient population may be desirable in some cases with the goals of improving mobility, relieving pain, and healing in an aligned position while minimizing deformity progression. However, internal fixation of the osteoporotic pelvis can be difficult. Large unicortical lag screws are the workhorse of posterior pelvic fixation, and yet fixation in cancellous bone corridors of an osteoporotic sacrum seems unlikely to achieve optimal fixation. As a result, the operative management and clinical results of these difficult injuries may not be uniformly successful. The authors present a technique for treating osteoporotic patients with a sacral fracture when operative treatment is indicated using percutaneous screw fixation combined with screw augmentation using a resorbable calcium phosphate bone substitute or "cement." The guide wire for a 7.3-mm or other large cannulated lag screw is fully inserted along the desired bony sacral corridor as is standard. The lag screw is then inserted over the wire to the depth where cement is desired. The guide wire is removed, and the aqueous calcium phosphate is injected through the screw's cannulation. For acute fractures, cement was applied to the areas distant to the fracture; whereas in insufficiency fractures, the cement was inserted along most of the screw path. The guide wire then can be reinserted and the lag screw fully inserted. The rationale for using these 2 modalities is their synergistic effect: the cannulated screw provides typical screw fixation and also a conduit for cement application. The cement augments the lag screw's purchase in osteoporotic bone, enhancing fixation strength. The authors propose that combining percutaneous screw fixation with calcium phosphate augmentation may provide an improved biomechanical environment for healing of these difficult fractures that might translate into earlier mobility, better pain control, and improved outcomes.

Suture Anchor Biomechanics After Rotator Cuff Footprint Decortication

PURPOSE

To identify the biomechanical consequences of violating the cortical shelf when preparing the greater tuberosity for suture anchor repair.

METHODS

Demographic information and bone mineral density were obtained for 20 fresh-frozen human humeri (10 matched pairs). Suture anchors were placed at a predetermined location in decorticated and non-decorticated settings after randomization. Anchors were tested under cyclic loads followed by load-to-failure testing. The number of cycles, failure mode, stiffness, and final pullout strength were recorded.

RESULTS

Nineteen specimens met the inclusion criteria for final testing. A significant difference in mean ultimate load to failure was seen between the non-decorticated specimens (244.04 ± 89.06 N/mm) and the decorticated humeri (62.84 ± 38.04 N/mm, P < .0001). Regression analysis showed positive correlations with female gender and decreased bone mineral density (P = .008 and P = .0005, respectively).

CONCLUSIONS

Decortication of the rotator cuff footprint significantly decreases the pullout strength of the suture anchor. Gender and bone mineral density also play a significant role in bone-anchor biomechanics and should be considered during repair.

CLINICAL RELEVANCE

Caution should be exercised when preparing the rotator cuff footprint before suture anchor placement because of the significant risk of early repair failure at the bone-anchor interface.

Internal fixation of osteoporotic fractures

Osteoporosis leads to bone fragility and increased risk of fracture. Despite advances in diagnosis and treatment, the prevalence continues to rise. Osteoporotic fracture treatment has a unique set of difficulties related to poor bone quality and traditional approaches, and implants may not perform well. Fixation failure and repeat surgery are poorly tolerated and highly undesirable in this patient population. This review illustrates the most recent updates in internal fixation, implant design, and surgical theory regarding treatment of patients with osteoporotic fractures.

Conservative treatment of a femoral neck fracture following nail removal

With increased longevity, the management of fragility fractures in the elderly is becoming more frequent. In particular, hip fractures have considerable importance due to the significant morbidity and mortality. A 67-year-old woman underwent intramedullary nail (IMN) removal inserted for a pertrochanteric fracture that had occurred 20 months earlier. This was indicated due to continuous discomfort related to the protruding apex of the implant over the great trochanter. Due to pain persistence two days after surgery, a computed tomography (CT) scan was performed, documenting a minimally displaced impacted subcapital femoral neck fracture. Conservative management with close radiographic follow-up was conducted. After six months, the patient had returned to previous daily activities and a satisfactory range of motion was achieved without pain on walking. The purpose of our paper is to discuss the decision of removing hardware in the elderly osteoporotic patient and to analyze the possibility to conservatively treat an impacted minimally displaced subcapital fracture occurring after the removal of an IMN inserted previously for the treatment of a trochanteric fracture. In the elderly population with decreased bone quality, the removal of intramedullary implants of the proximal femur should be carefully evaluated, and osteoporotic patients undergoing reduction and fixation of femoral fractures should be encouraged to start antiosteoporotic therapy (bisphosphonate, teriparatide) to reduce the risk of further bone loss. Conservative treatment should be considered for the management of lesser symptomatic minimally displaced impacted fractures, where the inherent stability of the fracture allows rapid healing without further surgical attempts.

Biomechanical considerations for surgical stabilization of osteoporotic fractures

The incidence of osteoporotic fractures has been steadily rising along with the aging of the population. Surgical management of these fractures can be a challenge to orthopedic surgeons. Diminished bone mass and frequent comminution make fixation difficult. Advancements in implant design and fixation techniques have served to address these challenges and when properly applied, can improve overall outcome. The purpose of this review is to describe fixation challenges of common osteoporotic fractures and provide options for successful treatment.

Currents of plate osteosynthesis in osteoporotic bone

Osteoporotic fractures are becoming more prevalent with ageing of populations worldwide. Inadequate fixation or prolonged immobilization after non-surgical care leads to serious life-threatening events, poor functional results and lifelong disability. Thus, a stable internal fixation and rapid initiation of rehabilitation are required for faster return of function. Conventional internal fixation attempts to achieve the exact anatomy, often with extended soft-tissue stripping and compression of the periosteum, causing disturbance of the metaphyseal and comminuted fracture's bone blood supply. This technique relies on frictional forces between bone and plate. Osteoporotic bone might not be able to generate enough torque with the screw to securely fix the plate to bone. Thus, this surgical management have resulted in increased incidence of poor results in elderly, osteoporotic patients. The newly developed locked internal fixators, locking compression plates and less invasive stabilization system, consist of plate and screw systems where the screws are locked in the plate, minimizing the compressive forces exerted between plate and bone. Thus, the plate does not need to compress the bone nor requires precise anatomical contouring of a plate disturbing the periosteal blood supply. These fixators allowed the development of the minimal invasive percutaneous osteosynthesis. Nowadays, locking plates are the fixation method of choice for osteoporotic, diaphyseal or metaphyseal, severely comminuted fractures.

Pullout Performance of Self-Tapping Medical Screws

This study investigates the effect of the pilot hole size, implant depth, synthetic bone density, and screw size on the pullout strength of the self-tapping screw using analytical, finite element, and experimental methodologies. Stress distribution and failure propagation mode around the implant thread zone are also investigated. Based on the finite element analysis (FEA) results, an analytical model for the pullout strength of the self-tapping screw is constructed in terms of the (synthetic) bone mechanical properties, screw size, and the implant depth. The pullout performance of self-tapping screws is discussed. Results from the analytical and finite element models are experimentally validated.

Failure of fracture plate fixation

Failure of fracture fixation after plating often leads to challenging surgical revision situations. Careful analysis of all patient and fracture variables is helpful in both determining the causes of the fixation failure and maximizing the success of subsequent interventions. Biologic and mechanical factors must be considered. Biologic considerations include traumatic soft-tissue injury and atrophic fracture site. Common mechanical reasons for failure include malreduction, inadequate plate length or strength, and excessive or insufficient construct stiffness. Reliance on laterally based implants in the presence of medial comminution may be a cause of fixation failure and subsequent deformity, particularly with conventional nonlocking implants. Management of dead space with cement or beads has been effective in conjunction with staged approaches. An antibiotic cement rod in the diaphysis may provide fracture stabilization. Locking full-length constructs should be considered for osteoporotic fractures.

Comparison of a new minimum contact locking plate and the limited contact dynamic compression plate in an osteoporotic fracture model

The purpose of this study was to investigate the biomechanical properties of a new minimum contact locking plate (MC-LP) compared with the limited contact dynamic compression plate (LC-DCP). Eighteen pairs of fresh human osteoporotic cadaver radii were equally divided into three groups. Each specimen was tested in each of the following force applications: anteroposterior (AP) four point bending, mediolateral (ML) four point bending, and torsion. A 10-mm gap osteotomy model was used to simulate a comminuted diaphyseal radial fracture. For each pair, one radius received a limited contact dynamic compression plate (LC-DCP) and the contralateral radius was fixed with a minimum contact locking plate (MC-LP). Specimens were tested in nondestructive four point bending and torsion on an electronic universal material testing system. The results indicate that the MC-LP system is significantly more stable than the LC-DCP system when tested in four point bending and torsion in an osteoporotic comminuted radial diaphyseal fracture model.

Mechanical evaluation of fracture fixation augmented with tricalcium phosphate bone cement in a porous osteoporotic cancellous bone model

OBJECTIVE

The purpose of this study was to examine the effects of resorbable bone cement on screw and plate-screw fracture fixation in a porous osteoporotic bone model.

METHODS

Experiment 1: Screw pullout strength was assessed for 4 sets of 4.5-mm cortical screws inserted into a synthetic osteoporotic cancellous bone model, including screws inserted without cement augmentation (control), screws augmented with tricalcium phosphate (TCP) bone cement (Norian SRS; Synthes USA, Paoli, PA), and screws augmented with polymethylmethacrylate. Experiment 2: The effects of cement augmentation on plate-screw fixation strength were examined by performing cantilever bending tests on 4 sets of 8 plate-screw constructions, including nonaugmented and TCP-augmented standard and locked screw-plate constructions in a similar bone model.

RESULTS

Experiment 1: Cement augmentation with both TCP and polymethylmethacrylate increased screw pullout strength from a porous osteoporotic cancellous bone model by about 4-fold (P < 0.05), and there was no significant difference between the 2 cements (P > 0.1). Experiment 2: Fixation strength was 1.5 times higher for locked plates compared with standard plates when neither was augmented with cement (P = 0.07). Cement augmentation with TCP improved fixation strength by 3.6 times for a standard plate-screw construction (P < 0.05) and 3.3 times for a locked plate-screw construction (P < 0.05). The most stable construction was the TCP-augmented locked plate, in which a 5-fold increase was observed compared with that of standard plates without TCP (P < 0.05).

CONCLUSIONS

This study indicates augmenting screws with TCP cement during osteosynthesis improves fixation strength in an osteoporotic cancellous bone model.

CLINICAL RELEVANCE

: In fracture situations in which osteoporotic bone makes screw and screw-plate fixation tenuous, screw augmentation with TCP cement should be considered as adjunct treatment.

Improved anchorage in osteoporotic vertebrae with new implant designs

The goal of our study was to evaluate two newly developed implant designs and their behavior in terms of subsidence in lumbar vertebral bodies under cyclic loading. The new implants were evaluated in two different configurations (two small prototypes vs. one large prototype with similar load-bearing area) in comparison to a conventional screw-based implant (MACS TL). A pool of 13 spines with a total of 65 vertebrae was used to establish five testing groups of similar bone mineral density (BMD) distribution with eight lumbar vertebrae each. In additional to BMD assessment via dual-energy X-ray absorptiometry, cancellous BMD and structural parameters were determined using a new generation in vivo 3D-pQCT. The specimens were loaded sinusoidally in force control at 1 Hz for 1000 cycles at three load levels (100, 200, and 400 N). A survival analysis using the number of cycles until failure (Cox regression with covariates) was applied to reveal differences between implant groups. All new prototype configurations except the large cylinder survived significantly longer than the control group. The number of cycles until failure was significantly correlated with the structural parameter Tb.Sp. and similarly with the cancellous BMD for three of five implants. In both large prototypes the cycle number until failure significantly correlated with the preoperative distance to the upper endplates. Although the direct relationship between bone structure or density and mechanical breakage behavior cannot be conclusively proven, all the prototypes adapted for poor bone structure performed better than the comparable conventional implant.

The mechanical behavior of locking compression plates compared with dynamic compression plates in a cadaver radius model

OBJECTIVE

The purpose of this cadaveric study was to compare the mechanical behavior of a locked compression plate, which uses threaded screw heads to create a fixed angle construct, with a dynamic compression plate construct in a cadaver radius model.

DESIGN

Mechanical study with cyclic testing and high-speed optical motion analysis.

SETTING

Biomechanics laboratory at an academic institution.

PATIENTS/PARTICIPANTS

Eighteen pairs of fresh-frozen human cadaver radii were divided into 3 groups of 6 to be tested as a group in each of the following force applications: anteroposterior (AP) bending, mediolateral bending, or torsion.

INTERVENTION

Each bone was osteotomized leaving a 5-mm fracture gap and then fixed with a plate. For each pair, 1 radius received a standard plate (limited-contact dynamic compression plates; LC-DCP), the contralateral radius was fixed with a locking compression plate (LCP), and specimens underwent cyclic loading. Normalized stiffness, average energy absorbed, and Newton-cycles to failure were calculated. In addition, a 3-dimensional, high-speed, infrared motion analysis system was used to evaluate motion at the fracture site.

MAIN OUTCOME MEASUREMENTS

Construct stiffness, fracture site motion, cycles to failure, and energy absorption. Repeated measures ANOVA were used to detect differences between groups with time.

RESULTS

In the torsion group, LCP specimens failed at 60% greater Newton-cycles than the LC-DCP (1473 vs. 918; P < 0.05). In the AP group, the LC-DCP absorbed significantly greater energy during 10,000 cycles compared with the LCP group (P < 0.05). The 2 constructs demonstrated different biomechanical behavior with time. As cycling progressed in the LC-DCP specimens under torsion testing, stiffness (measured at the actuator at the bone ends) did not change significantly; however, fracture motion (measured at the fracture surfaces) decreased significantly (P = 0.04). The LCP specimens did not display similar behavior.

CONCLUSIONS

Our findings indicated that LCP constructs may demonstrate subtle mechanical superiority compared with the LC-DCP. The LCP specimens had less energy absorption in the AP group and survived longer in the torsion group. Discordance of motion between measurement regions was observed only in the LC-DCP torsion group, and may have been caused by plate-bone slippage or bone-screw subcatastrophic failure. However, many other compared parameters were found to be similar, and the clinical significance of the few differences found between constructs mandates further investigation.

Distribution of bone mineral density with age and gender in the proximal tibia

OBJECTIVE

To investigate both the age and gender related distributions of bone mineral density in the proximal tibia, specifically in aged patients.

BACKGROUND

For surgeons to achieve stable long-term fixation of implants in the proximal tibia, the distribution of bone mineral density must first be known. The changes that occur due to age or gender can alter these distributions.

METHODS

Quantitative computed tomography and indentation testing were used to investigate 40 human tibiae (27 female, 13 male, average age 63.3 years).

RESULTS

A significant reduction in bone mineral density was found in female tibiae between the age groups of < 60 and > or =60. This difference was not found in the male groups and no other significant difference was found between consecutive age groups. A three-dimensional map of the bone mineral density of the proximal tibia is therefore presented for the groups female < 60, female > or =60 and male. Reduced bone mineral density was consistently found in the central regions, whilst the regions of highest bone quality varied from postero-lateral to postero-medial.

CONCLUSIONS

Implant fixation for fracture treatment as well as joint replacement of the proximal tibia are now able to take the regions of both high and low bone mineral density into consideration in older patients and those suffering from osteoporosis.

RELEVANCE

Knowledge regarding the regional distribution of bone mineral density in the proximal tibia is necessary in order to achieve stable primary and long-term fixation of implants. This manuscript documents the bone mineral density changes that occur with age and gender.

Expandable nail system for osteoporotic humeral shaft fractures: preliminary results

BACKGROUND

Conventional nails rely on interlocking screws for axial and rotational stability. Such screws have poor fixation in patients with poor bone quality (osteopenia). The Fixion nail does not depend on interlocking screws-axial and rotational stability is instead achieved by nail expansion. Therefore, this nail may be better suited for patients with poor bone quality who require humeral stabilization.

METHODS

The system was used to manage 25 unstable humerus shaft fractures in osteoporotic bone. An antegrade approach was used in 18 patients and a retrograde approach was used in 7 patients.

RESULTS

There were no intra- or postoperative complications. Postoperatively, all fractures were stable and had healed by week 16. The mean operative time was 35 +/- 10 minutes (+/- SD) including 1.5 +/- 0.5 minutes of fluoroscopy time.

CONCLUSION

The results of this study show that use of this nailing system is associated with minimal complications, predictable fracture healing, and excellent functional outcomes in a cohort of elderly patients with poor bone quality and humeral shaft fractures requiring stabilization. Further confirmation by larger prospective trials is necessary.

Mechanical and histomorphometric evaluations of titanium implants with different surface treatments inserted in sheep cortical bone

Improvement of the implant-bone interface is still an open problem and the interest in chemical modification of implant surfaces for cementless fixation has grown steadily over the past decade. Mechanical and histomorphometric investigations were performed at different times on implants inserted into sheep femoral cortical bone to compare the in vivo osseointegration of titanium screws ( X 3.5 x 7 mm length) with different surface treatments. After 8 weeks of implantation, the push-out force of anodized and hydrothermally treated implants (ANODIC) was significantly higher than that of machined implants (MACH) (36%, p<0.0005), whereas a decrease of 39% was observed for acid-etched implants (HF) when compared to other surface treatments. After 12 weeks of implantation, the push-out force values of HF implants were still significantly lower than those observed for MACH (-19%, p<0.01) and hydroxyapatite vacuum plasma-sprayed implants (HAVPS, -25%, p<0.0005), and the highest push-out force was found in HAVPS (p<0.001) implants. After 8 and 12 weeks of implantation, the AI of HF implants was significantly (p<0.05) lower ( approximately -25%) than that of MACH, HAVPS and ANODIC implants. In conclusion, results appear to confirm that there are no specific differences between ANODIC and HAVPS implants in terms of behavior. Moreover, although MACH implants show some surface contaminating agents, they appear to ensure good osseointegration within 12 weeks both mechanically and histomorphometrically, as do ANODIC and HAVPS implants. However, further studies are required to investigate bone hardness and mineralization around implants.

Internal fracture fixation in patients with osteoporosis

Because of the decreased holding power of plate-and-screw fixation in osteoporotic bone fractures, internal fixation can have a high failure rate, ranging from 10% to 25%. Screws placed into cortical bone have better resistance to pullout than do those placed into adjacent trabecular bone. Plates should not be used to bridge unstable regions of bony comminution in osteoporotic patients. Fixation stability is optimized by securing stable bone contact across the fracture site and by placing screws both as close to and as far from the fracture as possible. Intentional shortening can improve stability and load sharing of the fracture construct. Structural bone graft or other types of fillers can be used to fill voids when comminution prevents stable contact. Load-sharing fixation devices such as the sliding hip screw, intramedullary nail, antiglide plate, and tension band constructs are better alternatives for osteoporotic metaphyseal locations. Proper planning is essential for improved fracture fixation in this high-risk patient group.