Fragment reconstruction and bone plate fixation versus bridging plate fixation for treating highly comminuted femoral fractures in dogs: 35 cases (1987-1997)

OBJECTIVE: To compare fragment reconstruction and bone plate fixation versus bridging plate fixation for treating highly comminuted (> 4 fragments) femoral fractures in dogs. DESIGN: Retrospective study. ANIMALS: 35 dogs with highly comminuted fractures of the femur. PROCEDURE: Medical records of all dogs included in this study were reviewed. Dogs had been treated with fragment reconstruction and bone plate application (n = 20) or major fragment alignment and bridging plate fixation (15). Postoperative and follow-up radiographs were evaluated. Operating and hospitalization times, bone alignment, bone healing, and complications were considered. RESULTS: There were no differences in hospitalization times, limb alignment, and complications between dogs with fractures treated with fragment reconstruction and dogs with fractures treated with bridging plate fixation. Dogs with fractures treated with bridging plate fixation had shorter operative times and faster times to radiographic evidence of bone healing. CLINICAL IMPLICATIONS: Bridging plate fixation is quicker to perform and results in faster healing than fragment reconstruction and bone plate fixation when used to treat comminuted femoral fractures.     

Fixation of canine tendons to metal

For the purpose of developing a method to attach tendons directly to the prosthesis, canine supraspinatus tendons were attached in vitro to a metallic surface, using 3 different fixation devices: a spiked polyacetal washer (Synthes), a spiked soft tissue fixation plate (Synthes), and a newly designed Enhanced Tendon Anchor (ETA), which straddled the tendon with interlocking spikes oriented at a 20-degree angle. 2 methods were used: 1) the tendon was fixed directly to the metallic surface, or 2) a bone block containing the tendon insertion was fixed to the metallic surface. The specimens were tested for initial fixation strength in tension to failure; intact bone-muscle-tendon-bone units were used as controls. Bone block fixations were stronger than direct tendon fixations when the spiked washer or the ETA was used; this was not true of the fixation plate. The ETA was stronger than the other techniques in ultimate strength in both direct tendon fixation and bone block fixation. The soft tissue fixation plate was found to be weaker than the other techniques in bone block fixation.     

Comparative evaluation of bone suture anchor to bone tunnel fixation of tibialis anterior tendon in cadaveric cuboid bone: a biomechanical investigation

A multiphase biomechanical study was performed using human tibialis anterior tendons and cuboid bones, comparing the fixation of the tendon to the bone using bone anchors and bone tunnels. Twenty-six specimens were tested for ultimate load to failure comparing Mitek Superanchor fixation with no. 1 and no. 5 braided polyethelyne suture to bone tunnel fixation. Mitek Superanchor with no. 5 suture failed at 223 N, compared with Mitek Superanchor with no. 1 suture at 134 N and bone tunnel at 143 N (P = 0.033). Mitek with no. 1 suture versus bone tunnel was not significantly different. The Mitek with no. 5 suture failed at the tendon/suture interface (75%), the Mitek with no. 1 suture failed at the suture/anchor interface (56%), and bone tunnel fixation failed most commonly by fracture of the tunnel (76%). This study is the first biomechanical analysis of the pullout strengths of bone tunnels or suture anchors in the cuboid bone. We have shown that the suture anchor has a pullout strength comparable or superior to a conventional bone tunnel in an in vitro situation. We believe it is a viable alternative to fixation of the tibialis anterior tendon to the cuboid when there is insufficient tendon length or failure of the bone tunnel.     

Norian SRS cement augmentation in hip fracture treatment. Laboratory and initial clinical results

Bone quality, initial fracture displacement, severity of fracture comminution, accuracy of fracture reduction, and the placement of the internal fixation device are important factors that affect fixation stability. New high strength cements that are susceptible to remodeling and replacement for fracture fixation may lead to improved clinical outcome in the treatment of hip fractures. Norian SRS is an injectable, fast setting cement that cures in vivo to form an osteoconductive carbonated apatite of high compressive strength (55 MPa) with chemical and physical characteristics similar to the mineral phase of bone. It can be used as a space filling internal fixation device to facilitate the geometric reconstruction, load transfer, and healing of bone with defects and/or fractures in regions of cancellous bone. Furthermore, this cement can improve the mechanical holding strength of conventional fixation devices. Use of this material potentially could improve fracture stability, retain anatomy during fracture healing and improve hip function, thus achieving better clinical outcomes. In vivo animal studies have shown the material's biocompatibility, and cadaveric studies have shown the biomechanical advantage of its use in hip fractures. Initial clinical experience (in 52 femoral neck fractures and 39 intertrochanteric fractures) showed the potential clinical use of this innovative cement in the treatment of hip fractures.     

The effect of screw insertion torque on tendons fixed with spiked washers

The long-term success of a hamstring tendon graft depends not only on the type of device that is used for fixation but also on the mechanical interlocking of the soft tissue between the fixation device and bone. The purpose of this study was to evaluate the effect of screw insertion torque on the structural properties of soft tissue fixed to bone with a spiked metal washer. Two bovine tendons, one similar in size to a human semitendinosus tendon and the other similar in size to a human gracilis tendon, were secured to a bovine femur using a figure-of-8 technique with screws and metal spiked washers. A single load to failure was applied at 25 mm/sec. A significant positive linear correlation was observed between fixation screw insertion torque magnitude and the ultimate failure load value. An increase in the fixation screw insertion torque produced an increase in the ultimate failure load value. Similarly, there was a significant positive linear correlation between fixation screw insertion torque magnitude and the average maximum linear load value. No relationship was detected between screw insertion torque magnitude and the linear stiffness values of the tendon-fixation construct, indicating that a reproducible model was used. This study demonstrates that screw insertion torque is an important variable that controls the initial strength of soft tissue fixation to bone.     

Customized staple fixation in hand and wrist surgery

Fixation of small bones in the adult and the child's hands remains a challenge. The authors present a technique of bone fixation using customized staples made intraoperatively from K-wires (0.9-1.6 mm in diameter). Their specific purpose was to provide axial alignment and rotational stability for carpal bone fixation and for epiphysiodesis in phalanges. This technique was used in 14 cases (11 adult and three paediatric). No bone shattering, implant breakage, implant loosening or infection occurred. As K-wires are quite malleable, custom sized and shaped staples which follow the bone contours could be made to give a more exact fixation. All cases had satisfactory outcomes, achieving the preoperative objectives of bony fixation. This method is safe, precise and technically easy. It is also relatively cheap and only requires simple, standard instruments.     

Intermediate clinical follow-up of a dual-radius acetabular component

In this study, 92 primary total hip arthroplasties were performed in 83 patients using a porous-coated, dual-radius, cementless, acetabular component. All hips underwent line-to-line dome reaming with press-fit implantation that was judged to have complete bone contact. This acetabular shell provides a 1-mm oversized peripheral rim, which adds excellent initial stability while allowing complete bone contact in all hips. No fractures occurred. In 83% of hips, adjunctive screw fixation was not necessary. At a minimum of 4 years, follow-up, there were no revisions, no acetabular migration, one case of acetabular erosion consistent with osteolysis, and the average Harris Hip Score was 95. The design features of this new acetabular component have provided excellent fixation with complete initial bone contact, resulting in satisfactory intermediate clinical and radiographic results. The design provides excellent peripheral stability and complete bone contact.     

Deep-frozen allogeneic cancellous bone grafts in 10 dogs: a case series

Deep-frozen, aseptically collected and processed allogeneic cancellous bone was implanted in eight dogs during the surgical repair of diaphyseal long bone fractures and in two dogs during arthrodeses. A combined allogeneic and autogeneic cancellous bone graft was used in two fractures with a segmental bone loss of more than 5 cm. Bone union occurred in five fractures and in both arthrodeses. Failure of fixation occurred in two dogs with nonunion fractures and in a third dog with an open, infected fracture. Biopsies from the fracture sites were obtained from these dogs following failure of their fracture fixation. The cancellous bone graft appeared to be in the process of normal incorporation in each case. Failure of fixation was attributed to technical or case management errors or both, in each of the three fractures that failed to achieve bony union. Frozen allogeneic cancellous bone grafts were effectively incorporated when used in the primary repair of fractures and arthrodeses. Combined autogenous and allogeneic cancellous bone grafts may be particularly useful in the repair of fractures with large segmental diaphyseal bone defects. The use of allogeneic cancellous bone grafts in nonunion fractures requires further investigation before it can be recommended.     

Bone remodeling around cementless hip implants

Bone remodeling results from the adaptation of bone to the stresses that act upon it. The insertion of an endoprosthesis into a femur changes the stress distribution within the femur, causing the bone to remodel. In this paper, we show how radiographic bone remodeling changes can be used to determine implant fixation and how bone remodeling changes can be quantitated by using dual-energy x-ray absorptiometry analysis as well as computer-assisted videodensitometry.     

Screw fixation of the olecranon after fracture or osteotomy

For 10 years prior to the availability of the Olecranon Screw described in this article, oblique fixation using a regular Sherman bone screw was employed for displaced fractures (with a suitable fragment) by engaging the anterior ulnar cortex. Internal fixation was supplemented by a split for 3 weeks. The reason for a special olecranon screw is to eliminate the necessity for additional fixation and permit early motion. No instance of non-union or important restriction of motion or serious complication has been encountered.     

The reduction of humeral fracture in pigeons with intramedullary poly (methyl methacrylate) and neutralization plate fixation

The reduction of experimental humeral fracture in pigeons was performed with intramedullary bone cement (poly (methyl methacrylate): PMMA) and neutralization plate fixation to investigate the effect on bone fracture healing and the recovery of flying ability. As a result, neither plate nor bone cement fixation held for more than 2 weeks, but not refracture was observed in any cases with both plate and bone cement. In the latter group, it was confirmed by flight tests that almost normal flying ability was recovered in 6 weeks. In pathological findings, blood supply to the fractured ends recovered within 2 weeks and no cortical bone necrosis was observed at the time except for a disturbance of endosteal callus formation. The process of fracture healing on the plate side took place slightly later than that on the non-plate side, and when much PMMA remained between the fractured ends of the cortical bone the bone formation became spongioid. In view of the quick recovery of flying ability, however, plate and bone cement fixation is considered appropriate to prevent the displacement of a humeral fracture in the pigeon.     

Biomechanical study of sternal closure using rigid fixation techniques in human cadavers

BACKGROUND: We believe rigid plate fixation may be superior to wire fixation in sternal closure, as rigid fixation used in the craniofacial skeleton has shown greater stability, lower postoperative pain, and accelerated bone healing. We hypothesize that sterna fixed with titanium plates are more stable mechanically than sterna fixed with wires. METHODS: The sterna from human cadavers were used in this two-phased study. Phase I compared wires to four-hole titanium straight plates. Phase II compared wires to four-hole titanium custom H plates. The sterna were tested biomechanically using all fixation methods. RESULTS: Phase I showed no statistically significant difference in the stiffness or lateral displacement between the wired and straight plated sterna. Phase II showed a statistically significant greater stiffness (p < 0.05) and less lateral displacement (p < 0.05) in the custom plated sterna over the wired sterna. CONCLUSIONS: Our results showed that custom titanium H plates were superior to wire fixation. Furthermore, our results established the importance of plate configuration in sternal fixation. Our study may have beneficial clinical implications, as decreased motion at the sternotomy site could mean less postoperative pain, a decreased incidence of infection, and accelerated bone healing.     

Genetic analysis of the cap5 locus of Staphylococcus aureus

BACKGROUND: Fifteen patients with femoral shaft fractures complicated by infected nonunions were treated with a two-stage protocol. METHODS: In the first stage, radical debridement was performed along with antibiotic bead chains local therapy and external skeletal fixation. In the second stage, the debrided nonunion site was repaired with bone grafting and the external skeletal fixator was used until bony union was achieved. The time between the first and second stages of treatment was 2 to 6 weeks. The debrided bone defects ranged from 0.5 to 15 cm. Autogenous iliac cancellous bone grafting was performed in 11 patients, and microvascularized osteoseptocutaneous fibular transfer was performed in 4 patients. RESULTS: Wound healing and bone union were achieved in all 15 cases. The duration of external fixation of these patients ranged from 7 to 15 months, with an average of 9 months. Minor pin-track infection was seen in seven patients. Postoperative infection after the second-stage bone grafting occurred in three patients. These three infections were arrested by limited debridement along with 2 to 4 weeks of parenteral antibiotic therapy. In one case, stress fracture occurred at 11 months after microvascularized fibular transfer; this was managed with another 5 months of external skeletal fixation. With an aggressive physical therapy program, 10 patients achieved nearly full range of knee motion and 5 patients had relevant knee flexion deficits. The follow-up averaged 58 months (range, 40-76 months); no recurrence of osteomyelitis was observed even at 76 months. CONCLUSION: We have found that our two-stage treatment with antibiotic beads local therapy, definitive external skeletal fixation, and staged bone grafting is an acceptable treatment protocol for the management of femoral diaphyseal infected nonunion. It results in rapid recovery from osteomyelitis and a predictable recovery from nonunion.     

Effects of resorbable fixation on craniofacial skeletal growth: modifications in plate size

On the basis of previous experimental work in young rabbits, modifications in the polymer fixation used (i.e., smaller plate size, change in ratio of polymer components) were studied for potential alleviation of known growth restriction in this model. Ten juvenile rabbits with metallic markers placed at the calvarial sutural junctions were plated across the left coronal suture. At 6 months of age, measurements were taken of both intermarker distances radiographically (growth) and the plates directly. Unlike previous reports, these resorbable plates permitted symmetrical frontal bone development, unaffected growth across the coronal suture, and a histologically normal underlying suture. These changes appear to be the result of elongation of the fixation plate across a growth site. These results indicate that the change in shape of resorbable fixation after initiation of degradation is more important than complete degradation of the material in rapidly growing bone sites.     

Fractures of the distal femur revisited

The treatment of supracondylar fractures is presented, including the most recent developments. The author uses the comprehensive classification of these fractures and explains the method of this classification scheme as a guide to treatment. New surgical approaches and a discussion of the surgical anatomy are presented in detail. The traditional and contemporary methods of reduction and fixation are discussed, and how the need to preserve the blood supply to the soft tissues and bone has led to the development of the modern methods. The biologic and biomechanical reasons for absolutely stable fixation for simple fractures and splinting with bridging plates, the so called bridge plating of multifragmentary fractures are explained as are the technical details of fixation. Discussed in detail are specific variations in treatment methods for the particularly difficult problem of open fractures, fractures above total knee arthroplasty, and fractures in osteoporotic bone.     

The Otto Aufranc Award. Skeletal response to well fixed femoral components inserted with and without cement

Previous studies evaluating femoral remodeling after total hip arthroplasty have used clinical radiographs and dual energy xray absorptiometry. Limitation of these techniques make it impossible to quantify the magnitude of bone loss in terms of cortical thinning and cortical bone area and bone mineral density changes. Femoral cortical bone remodeling after cemented and cementless replacement was quantified and possible determinants of bone remodeling in terms of clinical and radiographic variables were evaluated. Forty-eight anatomic specimen femora from 24 patients with unilateral cemented and cementless hip replacements were analyzed. Cortical thickness, cortical bone area, and bone mineral density was assessed in 4 quadrants at 5 discrete levels. The maximum cortical bone loss by level was at the middle section for the cemented femurs and at the midproximal and middle sections for the cementless femurs. However, if one examines individual quadrants, the proximal medial cortex still represents the specific region of maximal bone loss for both types of implant fixation. The posterior cortex had substantially more bone loss, even in the diaphyseal levels, than had been previously appreciated. A strong correlation was noted between the bone mineral density of the control femur and the percentage decrease of bone mineral density in the remodeled femur. Based on this data, it seems that the less dense the bone is before hip replacement surgery, the greater the extent of bone loss after total hip arthroplasty regardless of the fixation type.     

Preclinical testing of total hip stems. The effects of coating placement

The long-term fixation endurance of noncemented hip stems in total hip arthroplasty is subject to incompatible design goals. To reduce stress shielding and periprosthetic bone loss, proximal fixation and load transfer are indicated. However, to prevent interface motion and promote interface-bonding security, fixation preferably should be maximized over the entire stem surface. In this study, the authors questioned whether hydroxyapatite coatings could be applied in patterns that reduce bone resorption, while maintaining safe interface stress levels. For that purpose, strain-adaptive bone-remodeling theory was applied in 3-dimensional finite element models, to simulate the long-term postoperative bone resorption process. During the process, the adaptation of interface stresses was monitored, and its effects on interface failure probability evaluated. This analysis was done for a fully coated stem, a 1/3 proximally coated stem, a smooth uncoated, press-fitted stem, and a stem with 5 proximal patches of circumferential stripes. The uncoated stem reduced bone loss dramatically, but promoted interface motions and distal pedestal formation. In all cases, the gradual bone-remodeling process increased the interface security of the coated stems. Bone loss and interface failure probability were not very different for the fully and 1/3-coated stems. Stripe coating reduced bone resorption considerably, while increasing long-term interface failure probability only slightly. The investigators concluded that the initial stability and the ingrowth potential of such a stem design are likely to be inadequate.     

Principles of stable internal fixation

The results of internal fixation can be adversely affected by implant failure before union takes place. The survival of an internal fixation device depends upon load transfer from fragment to fragment. Techniques that do not provide such a load sharing between implant and bone will lead to failure of the implant. For example, absence of contact between cortices opposite the plate will increase the forces acting on the device which will either pull out, shear or break. This review focuses on the methods of applying implant to bone to achieve stable fixation and thus restore early function without sacrificing reduction and union.     

Patients treated for nonunions with plate and screw fixation and adjunctive locking nuts

Locking nuts were used as an adjunct to plate fixation in 48 procedures in 44 patients. All the procedures were done by one surgeon during a 4-year period. The patients in this study were treated for nonunion or malunion and thus had difficult technical problems, such as cortical defects or holes left from previous hardware. The use of standard implants were generally unreliable for additional fixation. The locking nuts were used as a cortical substitute in 26 instances, to create a fixed angle relationship between the plate and the screw in 14 instances, to elevate the plate off the bone to help increase vascularity in five instances, and to increase purchase in severely osteoporotic bone in three instances. Complete followup was obtained on 43 of the 44 patients. Forty of the 43 patients achieved complete union after their reconstructive procedure. Three patients had continued nonunions with eventual hardware failure and required reoperation. The use of the locking nuts enabled the surgeons to obtain stable fixation at the time of reoperation with eventual union of all of the ununited bones. The success of the use of this implant is best gauged by the fact that the surgeon could place screws effectively where cortical defects existed, allow improved purchase in osteoporotic bone, and create a fixed angle plate screw relationship that would have been difficult to do without the locking nuts.     

Review of autologous and allogeneic blood transfusion practices in patients undergoing radical hysterectomy

We investigated the short-term recuperation of bone mass during skeletal reloading after a period of unloading in young rats. One hind limb of 4-week-old rats was either unloaded irreversibly by sciatic neurectomy, or unloaded reversibly by external fixation. Other animals were sham-operated. After 9 days, the fixation-unloaded limbs were reloaded for 1-3 weeks and were compared with the hind limbs of age-matched unloaded (neurectomized) and sham-operated controls. Cortical and cancellous bone mass was measured using ashing and histomorphometry. Cortical bone mass (expressed as femoral dry and ash weight and tibial cortical bone area) was reduced in both unloaded groups and was accompanied by production of hypomineralized bone, as shown by a reduction in the percent ash of the dry weight. Cancellous bone mass (expressed as bone area and surface at the tibial metaphysis) was also reduced in both unloaded groups. Cortical bone mass deficit was greater in the fixation group than in the neurectomy group. Thereafter it increased in the neurectomy group despite a normal longitudinal growth rate, but returned to age-matched values in the reloaded group by 3 weeks. The changes in tibial cancellous bone mass were more pronounced but followed a similar pattern and normalized by 2 weeks. These data demonstrate that total unloading produced by external fixation causes a greater degree of bone mass deficit than partial unloading (produced by neurectomy); the rate of bone loss during unloading in the rat hind limb is more rapid than its recovery during reloading; and cancellous bone recuperates during the reloading phase faster than does cortical bone.