Faculty Bibliography

There has been a steady increase in the number of revision total knee arthroplasties being performed in the United States. Hinge knee prostheses are used predominantly in complex primary or revision arthroplasties, often as salvage procedures. Significant improvement of the articulation between the rotating hinge mechanism and tibial component has decreased the stresses that contributed to earlier failures in previous generation designs. Two cases of fracture of the tibial metal post in the rotating hinge of a revision total knee arthroplasty were evaluated and treated at our institution within a 1-month period. We present our experience with this construct failure and subsequent patient management

Postoperative development of heterotopic ossification can compromise the success of total hip arthroplasty (THA). Heterotopic ossification has been associated with decreased postoperative hip range of motion (ROM), potentially leading to poor patient satisfaction with outcome. Many risk factors predisposing to heterotopic ossification have been discussed in the literature, including sex, age, operative time, surgical approach, and preoperative function. The goal of this study was to examine if preoperative ROM is a risk factor for the development of severe heterotopic ossification after THA, and the impact of severe heterotopic ossification formation on the gain in ROM following THA. In a retrospective study of a single surgeon's 20-year experience, all patients who developed type III heterotopic ossification after THA were evaluated for hip ROM preoperatively and at 1-year follow-up. Total ROM was classified according to the modified Merle d'Aubigne score, and Harris Hip Scores were calculated. A statistically significant difference was found in preoperative external rotation in the study group compared to the control group (P<.001). At 1 year postoperatively, hip ROM differences were significant in external rotation (P<.001), internal rotation (P<.001), and abduction (P<.05). The modified Merle d'Aubigne score was significantly different between the groups (P<.001). Although many factors have been shown to influence the development of heterotopic ossification following THA, we found that a decrease in preoperative external rotation may point to an increased risk. Surgeons should consider this data when considering the use of prophylactic treatment to avoid the development of heterotopic ossification

Different acoustic frequencies have been used to diagnose progression of osteoarthritis, gross pathology, and wear in knee prostheses. It is possible that detailed analysis of higher frequencies could detect and quantify the smaller geometric changes (asperities) that develop in articular prosthetic wear. In this study we evaluated the feasibility of using ultrasonic emission to determine total knee arthroplasty (TKA) type and time from implantation using a simple, handheld measurement system. We examined the ultrasound emission generated by similar designs of posterior stabilized (PS) and cruciate retaining (CR) total knee prostheses and native knees of 58 patients and 10 controls. The subjects were asked to sit, rise, sit again, and take five steps while recording the acoustic data from both knees. Acoustic emission analysis examined frequency distributions and power spectrums of the recorded signals, and their relations to prosthesis type and time from implantation. We screened 44 CR and 48 PS TKAs, as well as 24 native knees. Analysis of this data suggested a possibility of differentiating between type of implants, and a relation to time since implantation. Our data suggest that we might be able to assess the status and time from implantation of a TKA by acoustic emission signals. Further in vitro analysis of the relationship of wear to ultrasonic emission data are needed for accurate quantification of arthroplasty wear. A simple, in-office screening tool for TKA patients could indicate which patients require closer follow-up and monitoring due to risk of potential problems

Splash basins are used in arthroplasty cases to wash instruments. Several studies in the literature have shown these basins being a potential source of bacterial infection. This study assesses the risk of contamination of intraoperative splash basins used to wash and store instruments. A total of 46 random clean primary arthroplasty cases (32 hips, 13 knees, and 1 unicondylar knee) were studied by taking cultures of sterile splash basins as soon as they are opened (controls) and again at wound closure after instruments and debris have come into contact with the sterile water. All cultures were taken with sterile culture swabs and sent to the laboratory for aerobic, anaerobic, and fungal culture. Outcome measured was any positive culture. A total of 92 cultures from 46 cases were tested. Only 1 (2.17%) control culture, which grew Streptococcus viridans, was positive for bacterial growth. One of 46 samples (2.17%) taken at wound closure was positive for coagulase-negative Staphylococcus. Mean time between basin opening and wound closure was 180+/-45 minutes. For the 1 infected sample taken at the conclusion of the case, it was 240 minutes. Previous studies show contamination rates as high as 74% for splash basins used intraoperatively. Our study contradicts the belief that splash basins are a high source of infection, with only 2.17% of basins showing contamination. Splash basins can be a potential source of contamination, but the risk is not as high as previously cited in the orthopedic literature

The purpose of this study was to compare fixation stability and lag screw sliding characteristics between 2 different hip-nail lag screw designs, a telescoping screwbarrel and a solid helical blade. Simulated, unstable, 4-part intertrochanteric hip fractures were created in 6 pairs of cadaveric femurs. Each nail type was randomly assigned within each femur pair. Lag screw sliding and inferior and lateral head displacements were measured following an applied static load of 750 N. Measurements were obtained before, during, and after cyclical loading with 750 N for 105 cycles. Ultimate failure strength was determined. After considering inferior head displacements, no significant differences between the 2 screw designs were found. Mean head displacement for the helical screw was 2.18 mm, compared with 1.87 mm for the telescoping screw (P = .731). A significant difference in the amount of lateral movement of the lag screws was found, however. The helical lag screws had mean lateral sliding of 2.68 mm, compared with 0.25 mm for the telescoping screws (P = .007). Neither of the lag screw constructs failed by screw cutout from the head. Both screw designs provide similar fixation strength for stabilization of 4-part intertrochanteric fractures. Both the telescoping lag screw and the helical blade facilitate fracture collapse, but the telescoping lag screw also minimizes lateral projection of the screw from the nail. This advantage may help minimize postoperative lateral soft-tissue impingement

Heterotopic ossification (HO), the development of bone outside its normal location in the skeleton, can compromise outcomes of total hip arthroplasty (THA). The etiopathogenesis of HO, though incompletely understood, involves genetic abnormalities, neurologic injury, and musculoskeletal trauma. Several systems are used to classify severity of HO after THA. Numerous risk factors for HO, including patient factors and surgical techniques, have been described. Prophylaxis against HO traditionally has involved radiation therapy or use of nonsteroidal anti-inflammatory drugs. Once formed, heterotopic bone can be managed only with surgical excision

BACKGROUND: Patellar tendinitis is one of the several differential diagnosis of anterior knee pain. The clinical diagnosis of patellar tendinitis is based on tenderness to palpation at the inferior pole of the patella. The tenderness has been noted to be maximal when the knee is extended and the quadriceps relaxed, but a definite clinical sign for diagnosis is lacking. The accuracy of two clinical signs was assesed by a two-stage study which included physical examination, MRI and a cadaveric study. MATERIALS AND METHODS: Two clinical signs, the "passive flexion-extension sign" and the "standing active quadriceps sign" were assessed in 10 consecutive patients with presumed patellar tendinitis. Five patients had an MRI, showed focal abnormality in the tendon. The location of the MRI finding corresponded, to the region of maximal tenderness. A cadaveric dissection was undertaken to describe the anatomy of the patella and the patellar tendon during these tests. RESULTS: Both tests showed a significant decrease in tenderness at the area of inflammation when the patellar tendon was under tension. The cadaveric dissection showed that when the knee is flexed to 90 degrees or when the quadriceps is tensioned the deep fibers of the tendon do not deform to anteriorly applied pressure. CONCLUSION: We suggest using these studies routinely in the evaluation of patients with anterior knee pain.

STUDY DESIGN: Retrospective case-control review. OBJECTIVE: This retrospective study explored the hypothesis that the perioperative administration of blood products is an identifiable risk factor of increased surgical site infections (SSIs) after thoracic and lumbar spine surgical procedures. SUMMARY OF BACKGROUND DATA: Surgical site infections are a significant cause of postoperative morbidity and mortality. According to the Center for Disease Control's National Nosocomial Infections Surveillance system, which monitors the rate of hospital-acquired infections in the United States, SSIs represent the third most commonly reported type of nosocomial infection, accounting for 14% to 16% of all nosocomial infections. The incidence of SSIs after spinal surgery is influenced by both preoperative and intraoperative risk factors. The relationship between blood products and SSIs has been a matter of debate for more than 2 decades. Several studies have supported the association between the use of blood products and the development of postoperative surgical site infections. METHODS: A retrospective case-control study was performed. We reviewed the charts of all patients who had undergone thoracic and/or lumbar spinal surgery at the NYU Hospital for Joint Diseases between 2002 and 2007. All patients who had developed surgical site infections following spine surgery in this 5-year period were identified. RESULTS: Data for 61 cases and 71 controls were included in this study. The analysis of the preoperative risk factors was performed for the entire population of patients. Body mass index and blood transfusions were found to be statistically significant risk factors for increased surgical site infections for this population. CONCLUSION: Our findings support current theories that blood transfusions may have modulatory effects on the immune system of the recipients. Our specific study in spine patients may contribute to the expanding literature on allogeneic blood transfusions and the risk of nosocomial infections and encourage surgeons to favor a more restrictive policy with regard to transfusions

Background: When challenged with extremity wounds that require further debridement, edema reduction and decreased bacterial content, temporarily implanting vacuum-assisted closure reticulated open-cell foam dressings is an effective adjunct for temporary wound closure and results in enhanced flap tissue survival. Methods: A retrospective review was performed in 13 consecutive patients with a lower extremity surgical wound and exposed hardware, joint, tendon or bone who received the two-stage wound closure treatment. Primary endpoints included time to closure, total wound duration, and wound closure status upon discharge. Results: Mean time from the initial procedure until definitive closure was 4 days (range, 2-8 days). Mean wound duration before the procedure was 54 days (range, 5-120 days). All 13 wounds had delayed primary closure or random pattern flap upon discharge and remained closed throughout the length of follow-up. Conclusions: Temporarily implanted vacuum-assisted closure may be a safe and effective adjunctive therapy when applied to the undersurface of newly developed flaps

STUDY DESIGN: Retrospective study of patients enrolled in a prospective randomized Food and Drug Administration trial with single level cervical disc replacement (CDR) with the ProDisc-C (Synthes, Paoli, PA). OBJECTIVE: Evaluate the segmental range of motion (ROM) in the cervical spine pre- and postoperative after CDR. SUMMARY OF BACKGROUND INFORMATION: Each cervical level is believed to have its own biomechanical characteristics, ultimately leading to different sagittal and lateral ROM. Our understanding of the factors that influence motion after CDR continues to change and expand. METHODS: One hundred sixty-four patients with single level ProDisc-C arthroplasty were evaluated radiographically using Medical Metrics (QMATM, Medical Metrics, Inc., Houston, TX). Pre- and postoperative disc height and ROM were measured from standing lateral and flexion-extension radiographs. Of these 164 patients, 44 had a CDR at C6/C7, 96 at C5/C6, 18 at C4/C5, and 6 at C3/C4. The mean follow-up was of 24 months. Statistical analysis evaluated the difference in mean ROM between the groups. RESULTS: Before surgery, C4/C5 had more sagittal ROM compared with C3/C4, C5/C6, and C6/C7 (P < 0.001.) Before surgery, C4/C5 also had more lateral ROM compared with C3/C4, C5/C6, and C6/C7 (P = 0.015). After surgery, there were no significant differences in sagittal and lateral ROM between C3/C4, C4/C5, C5/C6, and C6/C7. The delta (difference between pre- and postoperative) proved that the C4/C5 CDR actually lost sagittal ROM (-2.5 degrees ) compared with the other levels, which gained sagittal ROM, C3/C4 (0.9 degrees ), C5/C6 (1.8 degrees ), and C6/C7 (1.6 degrees ); P = 0.037. There was no significant difference in the delta lateral ROM between the segments: C3/C4, C4/C5, C5/C6, and C6/C7. CONCLUSION: CDR approximates the different segmental sagittal and lateral ROM. Although C4/C5 had negative delta ROM in the sagittal and lateral planes, it provided a satisfactory final ROM. Long-term clinical outcome studies are needed to properly evaluate if these differences could ultimately affect the patients everyday life