Patterns of stress distribution at the proximal femur after implantation of a modular neck prosthesis. A biomechanical study.

BACKGROUND: Modular total hip arthroplasty incorporating a double taper design is an evolution offering potential advantages compared to single head-neck taper or monolithic designs. Changes in femoral offset, neck length or femoral anteversion are expected to alter the strain distribution. METHODS: We therefore analyzed the strain patterns after usage of all types of necks of a modular neck prosthesis, implanted in composite femurs. FINDINGS: The load distribution presented a repeatable pattern. Anteverted neck combinations resulted in higher stress at the anterior surface, whereas the retroverted ones at the posterior (e.g. at the middle frontal site, stress is 13.63% higher when we shifted from the long neutral neck to the long 15° anteverted neck and at the middle back site 19.73% higher when we shifted from the long neutral to the long 15° retroverted neck). Compressive stress was larger at the calcar region and exacerbated by the use of the varus neck (e.g. at the frontal 1 site stress increased by 44.01% when we used the long 8° varus neck in comparison to the long neutral neck). Anteverted neck combinations resulted in higher strain at the anterior cortex around the tip of the prosthesis. Short necks exhibited lower stress at the femoral shaft and higher at the trans-trochanteric area. INTERPRETATION: Anteverted neck combinations could be more prone to anterior thigh pain. Because of the possible risk of adaptive hypertrophy and early mechanical failure due to increased stress, the surgeon should be cautious when using necks with combined characteristics or short necks.

Bacterial wound contamination during simple and complex spinal procedures. A prospective clinical study.

BACKGROUND CONTEXT: Spinal procedures have a potential of intraoperative contamination. C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) have been used to diagnose postoperative infections after spinal surgery. However, it has not been demonstrated if there is an association between surgical site contamination and clinical manifestation of postoperative infection based on inflammatory markers and patients' clinical course. PURPOSE: The purpose of this prospective study was to evaluate the association between surgical site contamination and the development of a postoperative infection in simple and complex surgical procedures. C-reactive protein and ESR levels were observed. The correlation between their values, surgical time, type of surgical procedures, and contaminated surgical sites was investigated. STUDY DESIGN: Prospective clinical study. PATIENT SAMPLE: The study consisted of 40 patients divided into two groups. Group A included 20 patients (mean age, 46.2 years; 12 women and 8 men) who underwent an open discectomy for a lumbar herniated disc. Group B consisted of 20 patients (mean age, 67.9 years; 11 women and 9 men) who underwent a decompression and instrumented fusion for lumbar spinal stenosis. They were followed up for an average of 26.7 months (range, 11-40 months). OUTCOME MEASURES: Samples were obtained for cultures in standard time intervals during surgery. The types of bacteria cultured were evaluated, and CRP and ESR levels were measured. METHODS: Simple lumbar discectomy (Group A, 20 patients) and instrumented lumbar decompression for degenerative lumbar stenosis (Group B, 20 patients) were performed in a prospective consecutive series of patients. All patients were operated by the same surgeon in the same operating room. Surgical site preparation in each patient was done by a standard manner. Samples were obtained for cultures in standard time intervals during surgery. C-reactive protein and ESR levels were measured preoperatively on the 3rd, 7th, and 21st postoperative days, and the clinical course of each patient was recorded. RESULTS: From 40 patients, three patients in Group A and five patients in Group B, a total of eight patients (20%) had positive cultures for bacteria. There was no statistical significance between contamination and duration of surgery in both groups. None of the patients with positive intraoperative cultures developed any clinical signs of superficial or deep postoperative spinal infection, and no additional antibiotic treatment was administered. Three patients with negative cultures developed a postoperative infection. There were no differences in CRP and ESR values between patients with contamination and noncontamination in both groups. C-reactive protein and ESR levels were significantly elevated in complex procedures (Group B) than in simple procedures (Group A). Statistical analysis of CRP and ESR values in both groups and types of bacteria cultured intraoperatively are presented. CONCLUSIONS: The results of this study demonstrate that intraoperative contamination can occur during simple and complex spinal procedures. In the absence of postoperative signs of infection in patients with intraoperative contamination, there is no need of continuing antibiotic treatment. Postoperative kinetics of CRP and ESR showed to be the same in patients with and without intraoperative contamination. Higher levels of inflammatory markers were noted in complex spinal procedures where instrumentation was applied.

Computer-assisted three-dimensional correlation between the femoral neck-shaft angle and the optimal entry point for antegrade nailing.

Optimal entry point for antegrade femoral intramedullary nailing (IMN) remains controversial in the current medical literature. The definition of an ideal entry point for femoral IMN would implicate a tenseless introduction of the implant into the canal with anatomical alignment of the bone fragments. This study was undertaken in order to investigate possible existing relationships between the true 3D geometric parameters of the femur and the location of the optimum entry point. A sample population of 22 cadaveric femurs was used (mean age=51.09+/-14.82 years). Computed-tomography sections every 0.5mm for the entire length of femurs were produced. These sections were subsequently reconstructed to generate solid computer models of the external anatomy and medullary canal of each femur. Solid models of all femurs were subjected to a series of geometrical manipulations and computations using standard computer-aided-design tools. In the sagittal plane, the optimum entry point always lied a few millimeters behind the femoral neck axis (mean=3.5+/-1.5mm). In the coronal plane the optimum entry point lied at a location dependent on the femoral neck-shaft angle. Linear regression on the data showed that the optimal entry point is clearly correlated to the true 3D femoral neck-shaft angle (R(2)=0.7310) and the projected femoral neck-shaft angle (R(2)=0.6289). Anatomical parameters of the proximal femur, such as the varus-valgus angulation, are key factors in the determination of optimal entry point for nailing. The clinical relevance of the results is that in varus hips (neck-shaft angle

Solitary tibial osteolytic lesion.

We report an unusual case of solitary osteolytic tibial metastasis from a primary endometrial cancer in a 62-year-old woman. The primary cancer was treated with total abdominal hysterectomy and bilateral salpingo-oophorectomy combined with postoperative external beam radiotherapy, while the tibial metastasis was treated with an above knee amputation. The rarity of the case lies on the fact that metastases distally to the elbow and knee are uncommon and endometrial cancer rarely gives distal bone metastases and particularly solitary to the extremities.

Combined radiotherapy and indomethacin for the prevention of heterotopic ossification after total hip arthroplasty.

BACKGROUND AND PURPOSE: :Heterotopic ossification (HO) is a frequent complication following total hip arthroplasty. The aim of this study was to evaluate the efficacy of combined radiotherapy and indomethacin as compared to indomethacin alone for the prevention of HO after hip arthroplasty. PATIENTS AND METHODS: 96 patients were prospectively enrolled to receive either a single dose of postoperative radiotherapy of 7.0 Gy and indomethacin for the first 15 postoperative days or indomethacin alone for the same period. A historical group of 50 patients that received indomethacin alone served as control. Primary endpoint was the radiographic evidence of HO at 6 months. Secondary endpoints were the evaluation of factors related to HO development, side effects from each treatment, and group differences in the clinical assessment with the Merle d'Aubigné Score. RESULTS: Four patients in the combined-therapy group developed HO compared to 13 patients in the indomethacin group (p < 0.05) and 13 patients in the historical group (p < 0.05). One patient each in the combined group and the historical group developed Brooker III HO (nonsignificant difference). Duration of surgery and congenital hip disease were associated with HO development in the indomethacin groups, while age and congenital hip disease showed such an association in the combined-therapy group. The side effects and mean Merle d'Aubigné Score did not differ significantly between the three groups. CONCLUSION: Combined radiotherapy and indomethacin was more efficacious in preventing HO after total hip arthroplasty compared to indomethacin alone and should be considered for future investigation.

Transtibial versus anteromedial portal of the femoral tunnel in ACL reconstruction: a cadaveric study.

The aim of this cadaveric study was to compare the transtibial versus the anteromedial portal with respect to the anatomic femoral positioning of the ACL attachment. Ten fresh frozen cadaveric knees were included in our study. A standard arthroscopy was performed and the normal ACL was partially cut through with arthroscopic scissors leaving a small footprint of 2 mm at the anatomical insertion area on the lateral femoral condyle. The femoral tunnel was drilled through the tibial tunnel and subsequently through the anteromedial portal. Using a probe with standard magnification, we measured the distances of the two femoral tunnels from the margin of ACL footprint arthroscopically. The femurs were then dissected and we measured the distances of the two tunnels from the posterior part of the lateral femoral condyle. The median arthroscopically measured distance of the centers of transtibial femoral tunnel and of the femoral tunnel through the anteromedial portal from the margin of the femoral ACL footprint were 6.20 mm and 2.80 mm respectively. The difference was statistically significant. After femoral dissection the median distance of the centers of the transtibial femoral tunnel and the femoral tunnel performed through the anteromedial portal from the border of the articular surface at the lateral femoral condyle was 6.10 mm and 5.25 mm respectively (p<0.001). Both measurements showed that ACL reconstruction technique through the anteromedial portal is more accurate compared to the transtibial technique.

Intrinsic haemangioma of the median nerve: report of a case and review of the literature.

Intrinsic haemangioma of the median nerve is an extremely rare tumor that represents a challenge to diagnose and treat. Only a few cases have been reported in the literature. We present a 10-year-old girl who was diagnosed having an intrinsic haemangioma of the median nerve and treated with total surgical resection of the tumor, under high magnification, using microneurolysis and without the need to resect and graft the median nerve. Three years later, the patient is free of symptoms and no recurrence of the mass was noticed.