Efficacy of pulse oximetry for early diagnosis of pulmonary embolism after total knee arthroplasty.

INTRODUCTION: Early diagnosis and aggressive treatment of pulmonary embolism (PE) are crucial for preventing severe complications after total knee arthroplasty (TKA). This study aimed to examine the efficacy of measuring oxygen saturation (SpO2) using a pulse oximeter for early diagnosis of PE after total knee arthroplasty (TKA). MATERIALS AND METHODS: We consecutively examined 1645 patients who underwent TKA between January 2015 and November 2019. Postoperative SpO2 was measured with a pulse oximeter, which was stopped if SpO2 was maintained at ≥ 95% until postoperative day 2 (POD2). To diagnose PE, computed tomographic pulmonary angiography (CTPA) was performed for specific indications, including persistently low SpO2 < 95% (group 1), sudden decrease in SpO2 (group 2), and decrease in SpO2 after POD3 with presenting symptoms (group 3). Also, we divided the patients into unilateral, simultaneous and sequential TKA groups and compared the results with specific statistical techniques. RESULTS: Of the 1645 patients who underwent TKA, there were 20 patients with PE (1.2%), and symptomatic PE was observed in only 4 patients (0.24%). CTPA was performed in 58 (3.5%) patients, of whom 20 were diagnosed with PE. In groups 1 (n = 34), 2 (n = 21), and 3 (n = 3), CTPA was performed 2.4, 2.6, and 8.3 days after TKA, respectively, and 12, 8, and 0 patients were diagnosed with PE, respectively. Of the 782, 416, and 447 unilateral, simultaneous, and sequential (done in same admission with interval 1 or 2 weeks) patients with TKA, 38, 18, and 2 received CTPA, and 13, 6, and 1 were diagnosed with PE, respectively. All patients diagnosed with PE have persistently low SpO2 < 95% (group 1), or sudden decrease in SpO2 (group 2) until POD2. Of the patients diagnosed with PE, SpO2 decreased without the presentation of symptoms in 16 patients (11 and 5 from groups 1 and 2, respectively) and with the presentation of symptoms, such as mild dyspnea and chest discomfort, in 4 patients (1 and 3 from groups 1 and 2, respectively). CONCLUSIONS: Measuring SpO2 using a pulse oximeter until POD2 was an effective method for early diagnosis of PE after TKA. No case of morbidity or mortality was observed after early diagnosis with early stage CTPA and management of PE. We recommend measuring SpO2 with a pulse oximeter for early diagnosing of PE in TKA.

The Incidence Rate, Microbiological Etiology, and Results of Treatments of Prosthetic Joint Infection following Total Knee Arthroplasty.

Periprosthetic joint infection (PJI) remains among the most challenging and costly complications. PJI rates vary from 0.39% to 3.9% after total knee arthroplasty (TKA). This study aimed to identify the causative microorganisms involved and to report our experience of subsequent treatment of PJI following over 7000 TKAs performed over 19 years. A retrospective study was conducted on 4547 patients (7019 cases) from March 2000 to September 2019. The incidence rate of PJI was 0.5%. Gram-positive bacteria accounted for 88.8% (n = 16) of the 18 cases, and S. aureus was the most commonly isolated pathogen (n = 7, 38.8%). There were six cases of MSSA and one case of MRSA. Streptococcus species (n = 7, 38.8%) also showed the same pattern. The CoNS species (n = 2, 11.1%) and Gram-negative bacteria (n = 1, 5.5%) were also reported. Candida species were isolated from 1 patient (5.5%). Successful I&D and implant retention (DAIR procedures) was achieved at the final follow-up in 19 patients (82.6%). The incidence of causative microorganisms was different for each PJI onset type. The overall infection rate of PJI was less than 1%. Although the success rate of DAIR procedures is lower than the two-stage exchange arthroplasty in this study, it is possible to achieve acceptable success rates if DAIR procedures are carefully selected considering the virulence of the microorganism, duration since symptom onset, and early-onset infection.

Joint Replacement Surgery in Patients with Rheumatoid Arthritis in South Korea: Analysis of a Large National Database.

Background: We aimed to investigate the current trend of joint replacement surgery incidence in patients with rheumatoid arthritis (RA) in South Korea and to compare the incidence of joint replacement surgery in each affected joint. Methods: We performed this big data analysis to investigate the current trend of joint replacement surgery incidence in patients with RA in South Korea and to compare the incidence of joint replacement surgery in each affected joint. This retrospective study was based on data from the Korea National Health Insurance claims database. Results: The prevalence of RA increased every year (0.13% in 2008, 0.25% in 2016). The number of newly diagnosed patients increased from 29,184 in 2010 to 38,347 in 2016. The incidence rate of joint replacement surgery in patients with RA increased from 0.72% in 2010 to 4.03% in 2016. The knee (68.3%) was the most commonly replaced joint. The relative risk (RR) of additional joint replacement surgery was highest for the shoulder joint (RR,1.454; 95% confidence interval, 0.763-2.771). The median time from diagnosis to surgery was the shortest in the elbow joint (379 days) and the longest in the shoulder joint (955 days). The median time for each joint was short in order of the elbows, ankles, hips, knees, and shoulders (p < 0.01). Conclusions: The most frequently and initially replaced joints were different, but the prevalence and incidence of RA, as well as those of joint replacement surgery, have recently increased in South Korea. Joint replacement surgery in RA was the highest for the knee joint. The median time from diagnosis to surgery was shortest for the elbow, followed by the ankle, hip, knee, and shoulder. Regardless of whether patients are symptomatic, evaluation of large joints such as the knee, elbow, ankle, and hip should be considered from an early stage.

Combined PCL and PLC Reconstruction Improves Residual Laxity in PCL Injury Patients with Posterolateral Knee Laxity Less Than Grade III.

PURPOSE: To compare the short-term clinical and radiologic outcomes of combined posterior cruciate ligament (PCL) and posterolateral complex (PLC) reconstruction to those of isolated PCL reconstruction (PCLR) for patients with posterolateral knee laxity less than grade III. MATERIALS AND METHODS: We retrospectively reviewed 49 patients (51 knees) who underwent PCLR between January 2008 and December 2015. Patients with a minimum follow-up of 24 months were included and divided into two groups (group A, isolated PCLR; group B, combined PCL and PLC reconstruction). Clinical outcomes were evaluated as the International Knee Documentation Committee (IKDC) subjective, Lysholm, and Tegner activity scale scores. Radiologic outcomes were also assessed using the side-to-side differences in posterior tibial translation via stress radiographs. RESULTS: A total of 30 cases were analyzed. There were no significant differences in the Lysholm and Tegner activity scale scores between the two groups preoperatively and at the final follow-up. However, group B showed a higher IKDC subjective score compared to group A at the final follow-up (group A, 72.8±8.9; group B, 77.7±10.1; p<0.05). Regarding the radiologic outcomes, group B also showed a significantly less side-to-side difference in posterior tibial translation compared to group A at the final follow-up (group A, 4.8±2.3 mm; group B, 3.8±2.1 mm; p<0.05). CONCLUSION: Combined PCL and PLC reconstruction resulted in improved clinical and radiologic outcomes than isolated PCLR in patients who have less than grade III posterolateral laxity of the knee. In cases of PCL rupture with ambiguous PLC injury, combined PCL and PLC reconstruction may help to improve posterior residual laxity of the knee.

Mortality of septic knee arthritis in Korea: risk factors analysis of a large national database.

This study aimed to analyze the risk factors for mortality of septic knee arthritis in Korea through a large nationwide data research. The National Health Insurance Service-Health Screening database was used to analyze 89,120 hospitalizations for septic knee arthritis between 2005 and 2018. In-hospital, thirty-day, and ninety-day mortality, and their association with patient's demographic factors, various comorbidities (i.e., cerebrovascular disease, congestive heart failure, and myocardial infarction) and Charlson Comorbidity Index (CCI) were assessed. Secondary outcomes of complications (osteomyelitis, knee arthroplasty, recurrence) were analyzed. The number of hospitalization with septic knee arthritis increased from 1847 cases in 2005 to 8749 cases in 2018. There was no significant difference in mortality after diagnosis of septic knee arthritis between years. The risk of mortality in patients who hospitalized with septic knee arthritis increased in comorbidities like Congestive heart failure, dementia, myocardial infarction, chronic kidney disease. Hazard ratio (HR) decreased in patients who have comorbidities such as rheumatoid arthritis, liver disease, rheumatologic disease. HR for mortality in septic knee arthritis increased in patients with CCI more than 1. The risk factors for mortality in all periods were male sex, old age, high CCI, comorbidities such as congestive heart failure, dementia, myocardial infarction, chronic kidney disease. Efforts to reduce mortality should be concentrate more on patients with these risk factors.

Incidence and risk factors analysis for mortality after total knee arthroplasty based on a large national database in Korea.

This study aimed to analyze the rates and risk factors of postoperative mortality among 560,954 patients who underwent total knee arthroplasty (TKA) in Korea. The National Health Insurance Service-Health Screening database was used to analyze 560,954 patients who underwent TKA between 2005 and 2018. In-hospital, ninety-day, and one-year postoperative mortality, and their association with patient's demographic factors and various comorbidities (ie., cerebrovascular disease, congestive heart failure, and myocardial infarction) were assessed. In-hospital, ninety-day and one-year mortality rates after TKA were similar from 2005 to 2018. The risk of in-hospital mortality increased with comorbidities like cerebrovascular disease (hazard ratio [HR] = 1.401; 95% confidence interval [CI] = 1.064-1.844), congestive heart failure (HR = 2.004; 95% CI = 1.394 to 2.881), myocardial infarction (HR = 2.111; 95% CI = 1.115 to 3.998), and renal disease (HR = 2.641; 95% CI = 1.348-5.173). These co-morbidities were also independent predictors of ninety-day and one-year mortality. Male sex and old age were independent predictors for ninety-day and one-year mortality. And malignancy was risk factor for one-year mortality. The common preoperative risk factors for mortality in all periods were male sex, old age, cerebrovascular disease, congestive heart failure, myocardial infarction, and renal disease. Malignancy was identified as risk factor for one-year mortality. Patients with these comorbidities should be provided better perioperative care.

Radiographic Prognostic Factors Relevant to Surgical Outcomes of Arthroscopic Partial Medial Meniscectomy in Elderly Patients with Mild Osteoarthritis.

The aim of this study was to investigate radiographic factors relevant to predict surgical outcomes of arthroscopic partial meniscectomy (APM) in elderly patients with mild osteoarthritis (Kellgren-Lawrence grades 1 and 2). Data of 172 consecutive patients aged >70 years who underwent arthroscopic meniscal surgery were reviewed retrospectively. The patients who met the inclusion criteria were classified into two groups based on the minimal clinically important difference value of the Lysholm knee scoring scale comparing the score of the last visit with that of the preoperative period: group 1 (with clinically significant improvement) and group 2 (without clinically important change). Radiographic factors assessed on X-ray and magnetic resonance images were evaluated using bivariate and logistic regression analyses. A total of 73 patients were included in this study. Bivariate analysis revealed that the extent of meniscus extrusion (p = 0.031), meniscus extrusion ratio (p = 0.001), and grade of meniscus degeneration (p = 0.019) were significantly different between the groups. Multivariate logistic regression analysis showed that the meniscus extrusion ratio was the most important independent predictive factor for surgical outcomes with clinically important changes (coefficient = 0.159, p = 0.009). On receiver operating characteristic (ROC) curve analysis, the cutoff point of the meniscus extrusion ratio discriminating the two groups was 34.2% (sensitivity: 79.3%; specificity: 68.6%; accuracy: 72.6%). Meniscus extrusion ratio was the most relevant predictive factor for discriminating patients with clinically important change. Meniscus extrusion ratio, with the cutoff point of 34.2%, could serve as a guide to determine whether to perform APM in elderly patients with mild osteoarthritis. This is a Level IV, therapeutic case series study.

Risk factors of postoperative complications following total knee arthroplasty in Korea: A nationwide retrospective cohort study.

BACKGROUND: The number of patients undergoing total knee arthroplasty (TKA) is gradually increasing and there is also increase in postoperative complications. The patient's demographic, socio-economic factors, hospital and clinical factors are all factors that can influence postoperative complications. The purpose of this study was to determine the risk factors associated with complications following TKA in a large national cohort. METHODS: Among patients diagnosed with primary knee arthrosis, a total of 560,954 patients older than 50 years who underwent TKA from January 1, 2005 to December 31, 2018 were included in the study. The risk of postoperative complications (surgical site infection, sepsis, cardiovascular complications, respiratory complications, pulmonary embolism, stroke, acute renal failure, periprosthetic joint infection, and periprosthetic fracture) were assessed with eight independent variables: gender, age, place of residence, household income, hospital bed size, procedure type (unilateral or bilateral, primary or revision TKA), length of stay (LOS), use of transfusion. Multivariable Cox Proportional Hazard model analysis was used. The significant predictors for complications (P < .05) were as follows. RESULTS: Surgical site infection: male, procedure type (bilateral, revision), LOS (≥35 days), transfusion. Sepsis: male, household income, procedure type (bilateral, revision), LOS (≥35 days), transfusion. Cardiovascular complications: male, age, household income, procedure type (bilateral, revision), LOS (≥35 days), transfusion. Respiratory complications: male, household income, procedure type (bilateral, revision), LOS (≥35 days), transfusion. Pulmonary embolism: male, household income, procedure type (bilateral, revision), LOS (≥35 days), transfusion. Stroke: male, age, procedure type (bilateral, revision), LOS (≥35 days), transfusion. Acute renal failure: male, household income, procedure type (bilateral, revision), LOS (≥35 days), transfusion. Periprosthetic joint infection: male, household income, procedure type (bilateral, revision), LOS (≥35 days), transfusion. Periprosthetic fracture: male, procedure type (bilateral, revision), LOS (≥35 days), transfusion. CONCLUSION: In summary, male, procedure type (bilateral, revision), LOS (≥35 days), and use of transfusion were shown to be risk factors of postoperative complications following TKA.

Osteochondral Fracture of Posterior Aspect of Lateral Femoral Condyle After Lateral Patella Dislocation: A Case Report.

CASE: A healthy 15-year-old girl presented with osteochondral fracture at the posterior aspect of the lateral femoral condyle (LFC) associated with a right patellar dislocation after a noncontact injury. The patient remained asymptomatic 18 months after the arthroscopically assisted reduction and internal fixation of the osteochondral fracture using bioabsorbable pins and was able to eventually resume her usual activities of daily living. CONCLUSIONS: This is the first report of an osteochondral fracture at the posterior aspect of the LFC after an acute patellar dislocation, successfully treated with arthroscopically assisted reduction and internal fixation using bioabsorbable pins. This rare injury and unique mechanism of injury have been discussed.

What can the radiological parameters of superior migration of the humeral head tell us about the reparability of massive rotator cuff tears?

OBJECTIVE: The interrelation and clinical utility of the parameters for superior migration of the humeral head, such as the acromiohumeral interval (AHI), inferior glenohumeral distance (IGHD), and upward migration index (UMI), in the management of massive rotator cuff tears are not clear. The objectives of this study were to identify the relation between AHI, IGHD, and UMI when measured with radiography and MRI and to determine whether superior migration can predict the irreparability of massive rotator cuff tears. METHODS: We retrospectively reviewed the files of 64 consecutive patients who underwent arthroscopic partial or complete repair for massive rotator cuff tears at our institution between August 2015 and August 2018. We recorded both radiography and MRI measurements of AHI, IGHD, and UMI, and further the tangent sign, fatty infiltration of the rotator cuff muscles, and the Patte grade. We performed correlation assessments and multiple logistic regression analysis to identify potential predictors of the reparability of massive rotator cuff tears. RESULTS: Thirty-five patients had partially reparable and 29 had completely reparable tears. Parameters measured with either radiography or MRI were highly correlated with each other. The radiographic measurements showed a moderate or low correlation with the MRI measurements. All parameters of superior migration of the humeral head on radiography and MRI, the tangent sign, fatty infiltration of the infraspinatus muscle, and the Patte grade showed significant differences between patients with partially and completely repaired tears. Among these, the independent predictors for irreparability was Patte grade = 3. CONCLUSION: The AHI, IGHD, and UMI were highly correlated when measured with either radiography or MRI, but not when comparing their radiographic with their MRI values. Furthermore, they were not independent indicators of reparability in massive rotator cuff tears.

Rupture of the Deep Femoral Artery during Proximal Femoral Nailing Following an Intertrochanteric Fracture: A Case Report.

Recently, we experienced a case where the diagnosis and management of a deep femoral artery rupture was delayed. This vascular complication occurred during the insertion of a distal interlocking screw of a proximal femoral nail for the fixation of an intertrochanteric femur fracture. A 79-year-old male patient was diagnosed with a right intertrochanteric fracture after a fall. We fixed the fracture with a proximal femoral nail (Zimmer® Natural Nail™ System). One day after the procedure, the patient complained of pain and swelling on the anteromedial side of his middle thigh followed by hypotension, anemia and prolonged thigh swelling. Computed tomography angiography was performed 7 days after the procedure. We found a pseudoaneurysm of the perforating artery caused by injury to the deep femoral artery and an intramuscular hematoma in the anterior thigh muscle. We successfully treated the pseudoaneurysm using coil embolization. Throughout the management of intertrochanteric femoral fractures, it is important to be aware and monitor signs and symptoms related to the possibility of blood vessel damage. When a patient presents with swelling and pain on the middle thigh and/or unexplained anemia postoperatively, the possibility that these symptoms are caused by an injury to the femoral artery must be considered.

Congenital anomaly of the atlas misdiagnosed as posterior arch fracture of the atlas and atlantoaxial subluxation.

Partial or complete absence of the posterior arch of the atlas is a well-documented anomaly but a relatively rare condition. This condition is usually asymptomatic so most are diagnosed incidentally. There have been a few documented cases of congenital defects of the posterior arch of the atlas combined with atlantoaxial subluxation. We report a very rare case of congenital anomaly of the atlas combined with atlantoaxial subluxation, that can be misdiagnosed as posterior arch fracture.

Detection of prefracture hip lesions in atypical subtrochanteric fracture with dual-energy x-ray absorptiometry images.

PURPOSE: To retrospectively assess how often and how early hip dual-energy x-ray absorptiometry (DXA) images show prefracture lesions in patients with atypical subtrochanteric fracture (ASF) and determine whether DXA images with assessment of prodromal symptoms could be used for early ASF prediction. MATERIALS AND METHODS: The retrospective research protocol complied with HIPAA and was institutional review board approved, with waiver of informed consent. Among 62 women with ASF, nine without hip DXA images and seven without clear documentation of prodromal symptoms were excluded. Serial DXA images of 52 hips in 46 patients were included. Among them, 33 hips were assessed with ipsilateral DXA. For this ipsilateral group, each hip was assessed for prodromal symptoms and focal cortical changes in the lateral subtrochanteric femur cortex at DXA. Overall and cumulative detection rates for prodromal symptoms, DXA, and DXA with prodromal symptoms were measured and compared with a general linear model for overall detection rate and Cox proportional hazard models for cumulative detection rate. Thirty-three representative ipsilateral images and 199 images from subjects without fractures were reviewed in random order for prefracture lesions by three musculoskeletal radiologists independently, and the performance of DXA in ASF prediction was assessed. RESULTS: Overall detection rates for DXA, prodromal symptoms, and DXA with prodromal symptoms were 61% (20 of 33), 42% (14 of 33), and 73% (24 of 33), respectively, in the ipsilateral group. Overall detection rate comparisons showed that DXA with prodromal symptoms was superior to prodromal symptoms alone (P = .0377). The cumulative detection rate curve for DXA with prodromal symptoms was also superior to that of prodromal symptoms alone (P = .0018). Sensitivity and specificity of DXA in ASF prediction ranged from 52% (17 of 33) to 58% (19 of 33) and 99% (197 of 199) to 100% (199 of 199), respectively. CONCLUSION: Assessment of hip DXA images combined with conventional assessment of prodromal symptoms enables detection of more ASFs earlier than assessment based on prodromal symptoms alone.

The treatment of nonisthmal femoral shaft nonunions with im nail exchange versus augmentation plating.

OBJECTIVES: The purpose of this study was to compare the results between exchange nailing (EN) and augmentation plating (AP) with a nail left in situ for nonisthmal femoral shaft nonunion after femoral nailing. DESIGN: : Retrospective data analysis, November 1996-March 2006. SETTING: A level I trauma center. PATIENTS: Eighteen patients with 18 nonisthmal femoral nonunions. INTERVENTION: Seven patients with 7 fractures treated for nonisthmal femoral shaft nonunions after femoral nailing with EN and 11 patients with 11 fractures treated for nonisthmal femoral shaft nonunions after nailing with AP combined with bone grafting. MAIN OUTCOME MEASURE: Union and complications. RESULTS: Five nonunions in the EN group failed to achieve union (72% failure rate), whereas all 11 pseudarthroses in the AP group obtained osseous union. Fisher exact test showed a higher nonunion rate of EN compared with AP for nonisthmal femoral shaft nonunion (odds ratio, 6.5; P = 0.002). CONCLUSIONS: AP with autogenous bone grafting may be a better option than EN for nonisthmal femoral nonunions.

Comparison of the proximal chevron and Ludloff osteotomies for the correction of hallux valgus.

BACKGROUND: Although several studies have described good results of proximal chevron and Ludloff osteotomies, there have been no studies comparing the results of these two techniques at a single institution. MATERIALS AND METHODS: We consecutively evaluated 46 patients who underwent proximal chevron osteotomies and 52 patients who underwent Ludloff osteotomies. Patients were evaluated by preoperative and postoperative weight bearing radiographs and the American Orthopaedic Foot and Ankle Society (AOFAS) hallux MP score. RESULTS: Both groups had similarly high AOFAS scores and good correction by radiographic parameters. No statistically significant differences were found with respect to correction of hallux valgus angle (HVA) and intermetatarsal angle (IMA) between the two groups. Significant shortening of the first metatarsal was found after Ludloff osteotomy (p < 0.05). At 6 weeks after surgery, the pain subscore was significantly lower in the proximal chevron group than in the Ludloff group (p < 0.05). CONCLUSIONS: The proximal chevron and Ludloff osteotomies yielded equivalent clinical and radiological results. The Ludloff osteotomy with lag screw fixation is more stable and does not require postoperative hardware removal, although it is technically demanding and has a tendency toward greater shortening of the first metatarsal.

The treatment of reverse obliquity intertrochanteric fractures with the intramedullary hip nail.

BACKGROUND: Reverse obliquity intertrochanteric fractures have been recognized as having unique anatomic and mechanical characteristics. Even though some clinical reports regarding intramedullary hip nailing for reverse obliquity intertrochanteric fracture show favorable results, there has been no clinical report of intramedullary hip nailing regarding the clinical significance of the lesser trochanteric fragment which differentiates Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association (AO/OTA) 31-A3.3 from A3.1 and A3.2. METHODS: We retrospectively reviewed the clinical results of 46 cases of reverse obliquity or transverse intertrochanteric fracture treated with intramedullary hip nails. Twenty-five fractures were fixed with proximal femoral nail (PFN), and 21 fractures were fixed with intertrochanteric subtrochanteric nail. RESULTS: Among 40 patients, followed up for more than 6 months, 22 31-A3.3 fractures (84.6%) out of 26 and all 14 A3.1 or A3.2 fractures were healed after the first operation. The complications were four cases of fixation failure and one case of femoral shaft fracture after fall. They occurred in the A3.3 type fracture, which were fixed with the PFN. The mean union time was longer in the A3.3 group (5.98 months, range 3-17 months) compared with that in the A3.1 or A3.2 group (4.65 months, range 3-9 months) (p = 0.048). Two cases of reciprocal migration of two screws (Z-effect) required exchange of the femoral neck screw to a shorter one in the PFN group. The amount of sliding of the femoral neck screw of the PFN (6.8 mm, range 0.3 mm-16.5 mm) was greater than that of the intertrochanteric subtrochanteric nail lag screw (1.89 mm, range: 0.2 mm-4.6 mm) (p = 0.012). Statistical analysis showed that the type of implant PFN, fracture subtype (31-A3.3), and old ages (more than 65 years old) significantly prolonged the union time (p < 0.05). CONCLUSION: The lesser trochanteric fragment and posteromedial defect in 31-A3.3 fracture seems to play an important role in the stability after intramedullary hip nailing. The causes of fixation failure in the PFN group were associated with excessive sliding of femoral neck screw, which was aggravated by toggling motion in the 31-A3.3 fractures.

Correction of lag screw guide pins inappropriately placed during intramedullary hip nailing.

INTRODUCTION: Lag screw position is one of the most important controllable factors in trochanteric fracture fixation. However, it is sometimes difficult to handle the lag screw guide pin during intramedullary hip nailing. In this study, causes of guide pin shift and correction of malposition were investigated. METHODS: The movements of guide pins during fracture fixation were traced fluoroscopically using 35 embalmed, mainly anteverted femora, angles were measured in the anteroposterior and lateral planes and necessary corrections calculated. RESULTS: In the proximal anteverted femur, posterior correction of an inappropriately placed guide pin in the lateral plane led to an inferior shift in the anteroposterior fluoroscopic view, and vice versa. Mean anteversion, alpha, beta, and beta' angles were 13.1 degrees (5-29 degrees ), 10.9 degrees (4-18 degrees ), 4.6 degrees (0-10 degrees ) and 4.4 degrees (0-9 degrees ), respectively. The beta' angle was directly proportional to the anteversion angle only, i.e. Y=0.27X+0.65 (R(2)=0.79), p<0.001. CONCLUSIONS: In the proximal anteverted femur, guide pin shift in the anteroposterior fluoroscopic view occurred during correction of pin position in the lateral plane. The amount of shift was directly related to the amount of anteversion.

High concentrations of pamidronate in bone weaken the mechanical properties of intact femora in a rat model.

PURPOSE: Bisphosphonates have been used to treat osteoporosis for more than ten years. However, complications associated with long-term administration of bisphosphonates, such as nonunion after pelvic insufficiency fracture or osteonecrosis of the jaw, have been recently reported in the literature. We investigated the relationships among the mechanical properties of the intact rat femur as well as healing fracture calluses and the intraosseous concentration of pamidronate (ICP), after long-term administration of pamidronate in a rat osteoporosis model. MATERIALS AND METHODS: We performed bilateral ovariectomy in 25 3-month-old female Sprague-Dawley rats. Beginning three months after ovariectomy, disodium pamidronate (0.5 mg/kg) was injected every month. After the six-month administration period, the left femoral shaft was fractured using the closed fracture technique. Five weeks after fracture, 23 rats were euthanized and both femora were removed. We checked the mechanical properties of the intact (right) and fractured (left) femora using a three-point bending technique. Intraosseous concentration of pamidronate was checked by high-performance liquid chromatography. RESULTS: The mean ICP was 61.8+/-15.7 ng/mg of bone. High ICP decreased the ultimate load to failure, stiffness, and ultimate stress of the intact femora (p=0.015, 0.027, 0.039, respectively). There was a tendency to decrease the ultimate load to failure in the healing callus when the ICP increased (p= 0.183). High ICP decreased the bone mineral density of the femoral head (p=0.005). CONCLUSION: High concentrations of pamidronate in intact bone decreased the bone mineral density and weakened the mechanical strength of the rat femora. The mechanical strength of the early healing callus was not correlated with concentration of pamidronate in the bone.

Anterior or posterior obliquity of the lag screw in the lateral view--does it affect the sliding characteristics on unstable trochanteric fractures?

We investigated the sliding pattern characteristics of proximal fragment in 16 proximal femur models of 31-A2.1 type trochanteric fractures fixed with dynamic hip screw system under load. In eight models, the lag screw was inserted with an anterior-to-posterior vector within the neck and the head of femur (group 1). The other eight had a posterior-to-anterior vector (group 2). A force of 500 N (30 cycles) was applied to the fracture fragment-plate complex using the Instron 6022. No significant difference was noted in the sliding distance between the two groups (p=0.17). However, the mean angle of rotation of the proximal fragment was twice as great in group 1 (16+/-3.7 degrees ) than that in group 2 (8.1+/-1.5 degrees ) (p<0.001). In group 1, early eccentric contact in the anterior aspect of the intertrochanteric area caused internal rotation of the proximal fragment. Breakage of the anterior cortex of the lateral wall was noted in five out of the eight cases in group 1 and no case in group 2 (p=0.026). Fracture of the anterior cortices significantly threatened the integrity of the lateral wall in group 1.