Focal osteolysis at the junctions of a modular stainless-steel femoral intramedullary nail.

BACKGROUND: During routine follow-up of patients treated with a three-piece stainless-steel modular femoral nail, osteolysis and periosteal reaction around the modular junctions of some of the nails were noted on radiographs. The purpose of this study was to evaluate the prevalence, etiology, and clinical relevance of these radiographic findings. METHODS: Forty-four femoral fractures or nonunions in forty-two patients were treated with a modular stainless-steel femoral intramedullary nail. Seventeen nails were excluded, leaving twenty-seven intramedullary nails in twenty-seven patients for this study. All patients had had a femoral diaphyseal fracture; nineteen had had an acute fracture and eight, a nonunion. These twenty-seven patients returned for radiographs, a physical examination, assessment of functional outcomes, assessment of thigh pain with a visual analog scale, determination of serum chromium levels, and nail removal if desired. A control group of sixteen patients treated with a one-piece stainless-steel femoral intramedullary nail was evaluated with use of the same outcome measures and was compared with the group treated with the modular femoral nail with regard to prevalence of thigh pain and serum chromium levels. Twelve modular femoral nails were removed according to the study protocol. The modular nail junctions were analyzed for corrosion products, and histopathologic analysis of tissue specimens from the femoral canal was performed. RESULTS: The twenty-seven patients were seen at a mean of twenty-one months after fracture fixation; twenty-six of the twenty-seven fractures healed. Twenty-three femora had at least one of three types of abnormalities-osteolysis, periosteal reaction, or cortical thickening--localized to one or both modular junctions. Eighteen patients had severe reactions, defined as osteolysis of > or =2 mm, cortical thickening of > or =5 mm, and/or a periosteal reaction (group 1). Nine patients had mild or no reactions (group 2). Serum chromium levels in group 1 (mean, 1.27 ng/ mL; range, 0.34 to 3.12 ng/mL) were twice as high as those in group 2 (mean, 0.53 ng/mL; range, 0.12 to 1.26 ng/mL). However, this difference did not reach significance with the numbers available. The differences in serum chromium levels between group 1 and the control group with a one-piece nail (mean, 0.26 ng/mL; range, 0.015 to 1.25 ng/mL) (p<0.01) and a control group without an implant (mean, 0.05 ng/mL; range, 0.015 to 0.25 ng/ mL) (p<0.01) were significant. The level of thigh pain recorded on the visual analog scale was also significantly different between group 1 and the control group with a one-piece implant (p = 0.03). Retrieved modular nails had signs of fretting corrosion as well as stainless-steel corrosion products adherent to the junction where the osteolysis occurred. Histologic and spectrographic analysis revealed two types of corrosion products that were consistent with stainless-steel within the peri-implant tissue and were associated with a foreign-body granulomatous response. CONCLUSIONS: The presence of corrosion products at the taper junctions suggests that particulate debris was a major factor in the etiology of the radiographic findings of osteolysis, periosteal reaction, and cortical thickening. Serum chromium levels were substantially elevated in the patients with a modular femoral nail, and such levels may serve as a marker of fretting corrosion of these devices.

Radiographic fracture assessments: which ones can we reliably make?

OBJECTIVE: To identify the fracture characteristics that can be reliably assessed by analysis of plain radiographs of tibial plateau fractures. DESIGN: Radiographic review study. PARTICIPANTS: Five orthopaedic traumatologists served as observers. INTERVENTION: Observers made assessments based on the radiographs of fifty-six tibial plateau fractures. Precise definitions of the assessments to be made were agreed on by all observers. The tested assessments included raters' abilities to identify and locate fracture lines, identify the presence of fracture displacement and comminution, make quantitative measurements of displacement, and characterize qualitative features of fractures. For thirty-eight of the fractures that had a computed tomography (CT) scan available, assessments were repeated using both radiographs and CT scans. MAIN OUTCOME MEASURES: To characterize interobserver reliability, percentage agreement and kappa statistics were calculated for categorical variables, and intraclass correlation coefficients (ICC) were calculated for noncategorical variables. RESULTS: Reliability of the assessments varied widely. Determining the location of fracture lines had the greatest reliability, whereas the subjective assessments of fracture stability and energy showed the poorest reliability. Although the ICCs for quantitative measurements approached acceptable levels, the tolerance limits were extremely wide. The addition of a CT scan improved the reliability of most assessments, but not to a statistically significant degree. CONCLUSIONS: Many basic radiographic interpretations relied on in making treatment decisions are made variably by observers. Using experienced raters and precise definitions of fracture assessments does not guarantee a high level of agreement. Discrete assessments have higher interrater agreements than do more qualitative assessments. Quantitative measures have wide tolerance limits and, therefore, probably cannot be used reproducibly to classify fractures or make treatment decisions. We conclude the reliability of fracture classification is limited by raters' abilities to agree on basic radiographic assessments.

Clinical failure after posterior wall acetabular fractures: the influence of initial fracture patterns.

OBJECTIVE: To determine radiographic and clinical features that predict rapid failure after open reduction and internal fixation of posterior wall acetabular fractures. DESIGN: Retrospective radiographic review and patient follow-up study. SETTING: University hospital. PATIENTS: Forty-two patients with posterior wall acetabular fractures. INTERVENTION: Open reduction and internal fixation. MAIN OUTCOME MEASURES: Radiographs, Merle D'Aubigné scores, Musculoskeletal Functional Assessment. RESULTS: Eleven patients had complete loss of joint space by one year postinjury; eight of these individuals required reconstructive surgery. These patients more commonly had fractures with comminution of three fragments or more (p = 0.001) or fracture into the subchondral arc at the level of the acetabular roof (p = 0.045). CONCLUSION: Poor outcomes after open reduction and internal fixation are associated with certain types of posterior wall fracture patterns.

Effects of pulsed electromagnetic fields on bone healing in a rabbit tibial osteotomy model.

OBJECTIVE: The purpose of this study was to determine the effect of pulsed electromagnetic field (PEMF) exposure on healing tibial osteotomies in New Zealand White rabbits. DESIGN: One-millimeter Gigli saw osteotomies were stabilized by external fixation. One day after surgery, rabbits were randomly assigned to receive either no exposure (sham control) or thirty minutes or sixty minutes per day of low-frequency, low-amplitude PEMF. Radiographs were obtained weekly throughout the study. Rabbits were euthanized at fourteen, twenty-one, or twenty-eight days, and tibiae underwent either destructive torsional testing or histologic analysis. To determine the baseline torsional strength and stiffness of rabbit tibiae, eleven normal intact tibiae were tested to failure. RESULTS: Sixty-minute PEMF-treated osteotomies had significantly higher torsional strength than did sham controls at fourteen and twenty-one days postoperatively. Thirty-minute PEMF-treated osteotomies were significantly stronger than sham controls only after twenty-one days. Normal intact torsional strength was achieved by fourteen days in the sixty-minute PEMF group, by twenty-one days in the thirty-minute PEMF group, and by twenty-eight days in the sham controls. Maximum fracture callus area correlated with the time to reach normal torsional strength. CONCLUSION: In this animal model, low-frequency, low-amplitude PEMF significantly accelerated callus formation and osteotomy healing in a dose-dependent manner.

Vertical shear injuries: is there a relationship between residual displacement and functional outcome?

BACKGROUND: Residual vertical displacement is often cited as being related to poor outcome in patients with pelvic injuries. This study attempts to clarify the relationship between residual vertical displacement and functional outcome. METHODS: From 1982 to 1989, over 500 patients with pelvic ring injuries were treated at two Level I trauma centers. Thirty-three patients with vertical shear (Tile C) fractures and residual displacement (2-52 mm) were evaluated. Outcomes were quantified by using SF-36 Short-Form Health Survey (SF-36) and the Iowa Pelvic Score (IPS). RESULTS: There was no correlation between IPS or SF-36 scales and residual vertical displacement. The IPS correlated (p<0.05) with seven of eight SF-36 categories, excluding mental health. Patients reporting limp and leg length discrepancy also correlated with the IPS and select SF-36. CONCLUSION: Pelvic injuries showed no correlation between functional outcome and residual vertical displacement suggesting other factors. The degree of residual vertical displacement does not affect functional outcome.

Imaging techniques for evaluation of postoperative orthopedic infections.

Labeled leukocyte scintigraphy is the preferred imaging technique for the evaluation of suspected postoperative orthopedic infections. Labeled leukocyte localization returns to a normal pattern faster than MRI after bone trauma, surgical procedures, and treatment of osteomyelitis. 99mTc HMPAO labeled leukocyte scintigraphy is useful, particularly in children, because less peripheral blood volume is required for labeling. However, delayed 16-20 hour imaging is usually needed to detect low-grade osteomyelitis, and 111In WBC usually provides better images in adults. Combined 111In WBC/99mTc sulfur colloid marrow images improve the specificity for detection of osteomyelitis in regions containing active bone marrow. Simultaneous 111In leukocyte/99mTc bone SPECT imaging is usually necessary in regions such as the skull, spine, and hips, where there is overlapping bone, and soft tissues.

Rank order analysis of tibial plafond fractures: does injury or reduction predict outcome?

We investigated the effects of severity of initial injury pattern and the quality of the articular reduction on outcome of displaced intra-articular distal tibial fractures, using a series of 25 patients who were treated with articulated external fixation and limited internal fixation, which provided a spectrum of reduction quality. Outcome was assessed by clinical ankle scores and radiographic arthrosis. The results demonstrate the rank order method to be a reliable means of stratifying severity of injury and quality of reduction. Neither injury nor reduction correlated with clinical ankle score. Reduction had a significant correlation with radiographic arthrosis. We conclude that the rank order method is useful in stratification of fracture patients, and that factors other than injury pattern and quality of articular reduction are important in determining outcome of patients with this severe articular injury.

External fixation of tibial plafond fractures: is routine plating of the fibula necessary?

OBJECTIVES: To determine the advantages and disadvantages of plating an associated fibula fracture in tibial plafond fractures treated with external fixation that spans the ankle. STUDY DESIGN: Retrospective clinical review. METHODS: The incidence of treatment complications and the outcomes achieved were compared between two groups of patients with tibial plafond fractures and associated fractures of the fibula. Both groups were treated by a uniform technique of monolateral external fixation. One group, consisting of twenty-two patients with twenty-two fractures, had plate fixation of the distal fibula and the other group, thirty-one patients with thirty-two fractures, had no fibular fixation. RESULTS: The demographics of the two groups, including sex, fracture classification, and number of open fractures, were similar. The outcome of the two groups for radiographic arthrosis and clinical ankle score, measured at minimum two-year follow-up, showed no statistically significant difference. The total numbers of complications were not statistically different between the two groups (p = 0.15), but the types of complications varied. Group I had eight complications: five fibular wound infections, two fibular nonunions, and one angular nonunion. Group II had seven complications: six angular malunions and one tibial wound infection. CONCLUSION: Open reduction and internal fixation of the fibula fracture in tibial plafond fractures treated with external fixation that spans the ankle is associated with a significant rate of complications, and good clinical results may be obtained without fixing the fibula.

Use of an articulated external fixator for fractures of the tibial plafond.

We performed a prospective study of forty-nine displaced fractures of the tibial plafond in forty-eight patients managed, at three centers, with an articulated external fixator placed medially across the ankle joint. Forty ankles had interfragmental screw fixation of a reduced articular fracture, and fourteen ankles had bone-grafting. The average duration of external fixation was twelve weeks. All of the fractures healed (one after delayed bone-grafting). There were no infections in any of the operative or traumatic wounds over the tibia. Two wound infections over the fibula resolved with treatment. Eight patients were managed with antibiotics for a pin-site infection, and two patients had curettage and débridement of a pin site in the hindfoot after removal of the fixator. Thirty patients (thirty-one ankles) completed two-year data sheets at an average of thirty months after the injury. The average ankle score was 67 points. Twenty-one patients had grade-0 or 1 osteoarthrosis and nine had grade-2 or 3. One ankle had been treated with an arthrodesis. These data suggest that the prevalence of early complications associated with severe fractures of the tibial plafond and their treatment can be decreased with use of an articulated external fixator combined with limited internal fixation. We concluded that this technique of external fixation is a satisfactory technique for the treatment of these fractures.

Effects of imposed hindfoot constraint on ankle contact mechanics for displaced lateral malleolar fractures.

Contact stress distributions on the tibial plafond were mapped in a series of eight fresh-frozen cadaver specimens in which displaced lateral malleolar fractures were studied. These included gripping (a) by snugly lacing the foot in an athletic shoe, (b) by polymethylmethacrylate potting of the calcaneus alone, and (c) by potting of the calcaneus plus talus. Each of these three gripping conditions was tested both for rigid and for nearly frictionless transverse external constraint conditions. Across the series, the grip-dependent changes in contact stress distributions were found to be very minor compared with the wide interspecimen variability that was consistently present. Moreover, although contact stresses generally increased with progressive lateral fibular fragment offsets of up to 5 mm, such an effect was far more modest than that seen in previous cadaver work. The present laboratory cadaver findings suggest that the contact stress elevations occurring clinically for displaced lateral malleolar fractures are probably relatively mild and likely not directly responsible for late secondary degeneration.

Diagnosis of infection in ununited fractures. Combined imaging with indium-111-labeled leukocytes and technetium-99m methylene diphosphonate.

The results of combined scintigraphy in which indium-111-labeled leukocytes and technetium-99m methylene diphosphonate were used were compared with the results of cultures of open bone at 102 sites of delayed union or non-union, to determine the effectiveness of this combination as a preoperative indicator of osteomyelitis. There were twenty-five true-positive, fifty-nine true-negative, eleven false-positive, four false-negative, and three indeterminate interpretations, yielding, for the diagnosis of osteomyelitis, a sensitivity of 86 per cent, a specificity of 84 per cent, an accuracy of 82 per cent, a positive predictive value of 69 per cent, and a negative predictive value of 94 per cent. There were few false-negative scans; false-positive results were most likely at a metaphyseal site adjacent to a joint in which there was post-traumatic arthropathy, at the site of a failed arthrodesis, and at the site of an unstable delayed union or non-union.

Periarticular bone sites associated with traumatic injury: false-positive findings with In-111-labeled white blood cell and Tc-99m MDP scintigraphy.

The authors evaluate the reliability of combined indium-111-labeled white blood cell (WBC) and technetium-99m methylene diphosphonate (MDP) bone scan interpretations at sites of suspected periarticular osteomyelitis with radiographic evidence of adjacent traumatic arthropathy. A review of all orthopedic patients who underwent In-111 WBC-Tc-99m MDP scintigraphy over a 7-year period revealed a subset of 32 such cases that also included results of bone-biopsy cultures. Twenty-eight patients had a history of traumatic intraarticular injury, and four had periarticular fracture malunion or nonunion. Compared with intraoperative culture results, blinded In-111 WBC-Tc-99m MDP scan interpretations included four true-positive, 17 true-negative, and 10 false-positive results, and one false-negative result. The predictive values for positive and negative scans were 28% and 94%, respectively. A high prevalence of false-positive In-111 WBC-Tc-99m MDP scans may occur at periarticular sites of patients with associated traumatic arthropathy. This reduces the specificity of this technique for osteomyelitis, making culture confirmation of positive scans necessary. A negative scan is highly predictive of negative culture results at these sites.

Dynamic external fixation for stabilization of nonunions.

Twenty-five long-bone nonunions were stabilized until healing with a dynamic axial fixator (DAF). Seventeen cases were culture positive and ten had open draining wounds. Five cases had segmental gaps larger than 3 cm. In addition to the DAF, infected atrophic cases received debridement, coverage, and bone graft. Cases with segmental gaps were usually treated with massive posterolateral grafts to create a tibiofibular synostosis. Hypertrophic cases received only compression and weight bearing. Bone grafts were performed in 14 cases. The DAF was usually removed after 16-24 weeks of treatment. Twenty of the twenty-five cases were healed at DAF removal and required no further intervention. Nine of the ten hypertrophic cases healed in an average of 18.1 weeks without graft. Thirteen of 15 atrophic cases were bone grafted. Cases with segmental gaps larger than 3 cm were treated with prolonged external fixation to protect maturing grafts, but were still subject to stress fracture after fixator removal.

Postoperative bone marrow alterations: potential pitfalls in the diagnosis of osteomyelitis with In-111-labeled leukocyte scintigraphy.

Scintigraphy was used after injection of technetium-99m methylene diphosphonate (MDP) and indium-111-labeled white blood cells (WBCs) to assess for the presence of osteomyelitis in 97 patients who had undergone prior surgical procedures. Thirty-four patients with abnormal In-111-labeled WBC patterns underwent restudy with Tc-99m albumin colloid (AC). Scintigraphic findings were considered positive for osteomyelitis whenever localization of In-111-labeled WBCs exceeded Tc-99m AC activity in extent or focal intensity (discordant pattern). Ten of 12 patients with culture-proved osteomyelitis had discordant patterns; two had false-negative (concordant) patterns. The cases of 20 of 22 patients without infection who were considered to have osteomyelitis on the basis of patterns of In-111-labeled WBCs and Tc-99m MDP were reclassified correctly on the basis of concordant patterns of In-111-labeled WBCs and Tc-99m AC. Radiocolloid images improved the overall scintigraphic specificity for osteomyelitis from 59% without bone marrow imaging to 92%; sensitivity decreased from 94% to 88%.

Glenoid labrum: evaluation with MR imaging.

Fifteen patients with shoulder instability and nine asymptomatic volunteers were studied with magnetic resonance (MR) imaging. The shoulder joint was visualized by means of arthroscopy or surgery in all patients. Ten patients had abnormalities of the glenoid labrum. Two musculoskeletal radiologists interpreted the MR images of the patients and volunteers without knowledge of the clinical history or surgical results. The surgical and arthroscopic results were used as the standard of reference in symptomatic patients. Observer A achieved a sensitivity of 44.4% and a specificity of 66.7%; observer B had a sensitivity of 77.8% and a specificity of 66.7%. In addition to the poor sensitivities and specificities, there was substantial intra- and interobserver variability. Assuming that the shoulders of the asymptomatic volunteers were normal, the specificities were 100.0% and 88.9% for observers A and B respectively. In this small study, axial MR imaging was relatively insensitive and nonspecific in the evaluation of labral lesions. Further study will be necessary to determine the utility and limits of MR imaging in this regard.

Unilateral external fixation until healing with the dynamic axial fixator for severe open tibial fractures.

One hundred one cases of open tibia fractures were treated until healing with a unilateral external fixation device that permits fracture site compression with weight bearing. There were 38 type II and 63 type III (24 IIIA, 33 IIIB, six IIIC) open fractures. A standard protocol was followed including irrigation and debridement and, when necessary, flap coverage (19 cases) and bone grafting (31 cases). Fixators were applied at the first debridement and removed when the fracture was healed. All patients were permitted early partial weight bearing and progressed to full weight bearing with fixator dynamization. Ninety-six cases healed in the fixator (12-50 weeks; average, 24.6). Three of the five failures were associated with screw complications. Five patients required screw changes and 29 required oral antibiotic therapy for screw complications. Ninety-five percent of healed cases had angulation of less than 10 degrees (in any plane). There were only six fracture site infections during the course of treatment. Dynamic axial fixation may be applied at the first debridement and be used until healing in severe open tibia fractures. Change of the fixator to another treatment method is not required.

Indium-111-leukocyte/technetium-99m-MDP bone and magnetic resonance imaging: difficulty of diagnosing osteomyelitis in patients with neuropathic osteoarthropathy.

Fourteen patients (16 sites) with clinical and/or radiographic evidence of neuropathic osteoarthropathy (Charcot joints) were evaluated with combined indium-111-leukocyte (111In-WBC) and technetium-99m-methylene diphosphonate (99mTc-MDP) bone imaging for suspected osteomyelitis. Magnetic resonance (MR) images were obtained in seven patients. Using a positive bone culture as the criterion for the presence of osteomyelitis, there were four true-positive studies, six true-negative sites, and one false-negative 111In-WBC study. Five of 16 sites (31%) had false-positive 111In-WBC uptake at noninfected sites. There were four true-positive and three false-positive MR studies. All false-positives showed at least moderately abnormal findings by both techniques at sites of rapidly progressing osteoarthropathy of recent onset. In this preliminary study, both techniques appear to be sensitive for detection of osteomyelitis, and a negative study makes osteomyelitis unlikely. However, the findings of 111In-WBC/99mTc-MDP and MR images at sites of rapidly progressing, noninfected neuropathic osteoarthropathy may be indistinguishable from those of osteomyelitis.

External fixation for open tibia fractures. A management strategy.

The management of open tibia fractures with the Dynamic Axial Fixator, including the method of application and postoperative care, is described. This fixator is utilized until healing. Weight bearing and axial fracture site movement promote an early callus response. The results obtained in the first 35 cases in which it was used at our institution are presented. Thirty-three of the fractures were successfully treated until healing in the external fixator.

Mechanical analysis of the factors affecting dynamization of the Orthofix Dynamic Axial Fixator.

Loading trials were conducted to identify mechanical factors affecting dynamization of a commercially available external fixator (Orthofix) that is designed to undergo free telescopic motion when axially loaded. Angular variations between the proximal and distal screw clamps and the telescoping fixator body failed to produce fixator binding (failure to dynamize) in any of the loading trials. However, binding was produced by applying external torques in magnitudes that occasionally occur during routine ambulation. The specific torque necessary to induce binding (typically 3-4 Nm) was only a weak function of axial load magnitude, axial loading frequency, or simulated fracture stiffness. Among several geometrical variables of fixator application, only the pre-extension of the telescoping body and circumferential misalignment between proximal and distal pin clusters had an appreciable influence on the threshold binding torque. Axial fixator motions were also monitored in a small adjunct clinical series of 22 dynamized tibial fractures. The fixator dynamized appropriately in 15 cases (68%). Three patients (14%) showed evidence of fixator binding, and another four (18%) had less than predicted slider excursions. The role of several design factors implicated in torque-induced fixator binding is discussed in light of the benchtop and clinical observations.