Are metal ion levels a useful trigger for surgical intervention?

The purpose of this study was to determine if cobalt and chromium ion levels can predict soft tissue damage at total hip revision. This study included 90 metal-on-metal total hip patients with preoperative cobalt and chromium ion levels. Tissue damage noted at revision surgery was graded on a 4-point scale. Sensitivity, specificity, and predictive values were calculated for various threshold values. Receiver operating characteristic analysis was conducted. Using 7 ppb as a threshold, cobalt and chromium ion levels had poor sensitivity and specificity (Co, 65% and 56%; Cr, 29% and 75%). Positive predictive values for cobalt and chromium were only 48% and 26% respectively. The area under the curve was 0.37 for cobalt and 0.44 for chromium. The length of time to revision significantly correlated with tissue damage (P = .001). Ion levels are unreliable predictors of periarticular soft tissue damage and should not be used in isolation as surgical intervention triggers.

Staphylococcus aureus nasal decolonization in joint replacement surgery reduces infection.

UNLABELLED: Surgical site infections (SSIs) with Staphylococcus aureus are a recognized adverse event of hip and knee replacements. We evaluated the impact of a program to detect S. aureus nasal carriers before surgery with preoperative decolonization (using mupirocin twice daily for 5 days prior to surgery) of carriers. Nasal swab samples were obtained from patients prior to surgery from 8/1/2003 through 2/28/2005. Samples were tested using real-time PCR technology to detect S. aureus. The group that developed S. aureus SSI was compared to a combined concurrent and historical control for one year following the operation. S. aureus caused 71% of SSIs in the combined control groups. Of the 1495 surgical candidates evaluated, 912 (61.0%) were screened for S. aureus; 223 of those screened (24.5%) were positive and then decolonized with mupirocin. Among the 223 positive and decolonized patients, three (1.3%) developed a SSI. Among the 689 screen-negative patients, four (0.6%) developed SSIs for an overall rate of 0.77%. Among the 583 control patients who were not screened or decolonized, 10 (1.7%) developed S. aureus SSIs. SSIs from other organisms were 0.44% and 0.69%, respectively. LEVEL OF EVIDENCE: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Venous thromboembolism following major orthopedic surgery: what is the risk after discharge?

Guidelines recommend thromboprophylaxis for at least 10 days to prevent venous thromboembolism in patients undergoing high-risk orthopedic surgery, such as total hip arthroplasty (THA) or total knee arthroplasty (TKA). Furthermore, the recently updated ACCP guidelines also recommend extending the duration of thromboprophylaxis for 28 to 35 days following THA or hip fracture surgery as the risk for venous thromboembolism persists for up to 3 months after surgery. Extended-duration thromboprophylaxis (up to 6 weeks) with low-molecular-weight heparin is significantly more effective in preventing venous thromboembolism in orthopedic surgery patients than the recommended practice of at least 10 days. Extended-duration thromboprophylaxis may require risk stratification to identify high-risk patients. Current risk-assessment models have limitations and are not specific to orthopedic surgery patients; therefore, improvements may facilitate the use of extended-duration thromboprophylaxis in high-risk patients, thereby reducing the burden of venous thromboembolism.

Growth of an intrapelvic pseudotumor associated with a metal-on-metal total hip arthroplasty after revision arthroplasty causing a femoral nerve neuropathy.

The development of pseudotumors is not uncommon with metal-on-metal total hip arthroplasty. Pseudotumors that dissect into the retroperitoneal space can cause symptoms of nerve compression. We describe a case of a 53-year-old male with a metal-on-metal total hip arthroplasty who developed mild symptoms of a femoral nerve neuropathy 6 years postoperatively. Revision arthroplasty to a ceramic-on-polyethylene articulation and debridement of the pseudotumor was performed. Postoperatively, the patient's femoral neuropathy progressed and a repeat magnetic resonance imaging showed an increase in size of the pseudotumor despite the removal of the offending metal-on-metal articulation. The patient subsequently underwent a laparoscopic excision of the retroperitoneal pseudotumor. By 17 months post laparoscopic excision of the pseudotumor, the patient's motor deficits resolved, however, sensory deficits persisted in the anteromedial thigh.

Femoral version: definition, diagnosis, and intraoperative correction with modular femoral components.

Normal femoral version contributes to the inherent stability of the hip joint. Abnormal version is found in a variety of hip diseases afflicting children and adults. At the time of reconstruction for end-stage hip disease, maintaining proper femoral version in conjunction with acetabular version allows for hip stability and unimpeded functional range of motion. In those instances where femoral version is significantly abnormal, a means of correction at time of surgery is necessary. Non-modular femoral components allow for minor adjustments in version at time of surgery. To accommodate significant versional abnormalities, the modular S-ROM (DePuy Orthopaedics Inc, Warsaw, Ind) was introduced in 1984. In a series of 156 primary S-ROM total hip arthroplasties, the ability to correct for abnormal version resulted in excellent clinical results with no incidence of hip instability and excellent range of motion.

Effects of sterilization on the Tekscan digital pressure sensor.

Investigations into the effects of sterilization on a new biomechanical pressure sensor are necessary before contemplating in vivo use. Ten, designated Experimental, "K-Scan" digital pressure sensor arrays were sterilized with ethylene oxide gas (EtO), and their ability to accurately and reproducibly measure an applied load of 2225 N (500 lb) was assessed. Simultaneously, 10 un-sterilized sensor arrays, designated Control, were assessed. Each array was loaded 10 times inside a two-dimensional curved surface, and all arrays exhibited high reproducibility (coefficients of variation<2.0%). Following sterilization, the Experimental sensors showed a 22.2% average decrease in recorded force, a statistically significant difference from the pre-sterile data (p<0.002). However, when the Experimental sensors were re-calibrated post-sterilization, they showed only a 0.1% average decrease in recorded force, not a statistically significant difference (p>0.05, beta<0.05). Following 1-week storage, trial 2 data of the Control sensors showed a less dramatic yet significant 3.4% average decrease in recorded force when compared to trial 1 data (p<0.02). Control trial 2, once re-calibrated, showed a 0.5% average decrease in recorded force, not a statistically significant difference (p>0.05, beta<0.05). Results suggest that, following EtO sterilization, accurate and reproducible pressure measurements can be obtained from K-Scan sensors when calibration is performed at time of use.

Early failure of a proximally cemented, distally uncemented total hip arthroplasty.

This investigation prospectively studied a consecutive series of 22 proximally cemented, distal cementless, femoral components with a minimum follow-up time of 24 months. The prosthesis was a titanium, proximally cemented, femoral component with a distal press-fit fluted design. Five hips (23%) developed aseptic mechanical loosening at an average of 46.2 months and required revision. The technique required excessive removal of cancellous bone leading to a suboptimal bone-cement interface. The early failure rates of this prosthesis are unacceptably high for a contemporary hip design. To the best of our knowledge, no clinical studies have reported on the stability and longevity of this new proximal cementing technique incorporated with a distal press-fit femoral design.