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The patient’s own evaluation of function and satisfaction is a fundamental component of assessing outcomes after total knee arthroplasty (TKA). The new Knee Society Knee Score was introduced in 2012 and has been shown to be a valid and reliable instrument for measuring the outcome of TKA. This score combines an objective, physician-derived component and a patient-reported component to characterize the expectations, satisfaction, and functional activities of diverse lifestyles of contemporary patients undergoing TKA. However, in the routine clinical setting, the administration and scoring of outcome measures is often resource-intensive, as the expenditure of time and budget for outcome measurement increase with the length and complexity of the instrument used, and so a short-form assessment can help to reduce the burden the assessment of outcomes. The purposes of this study were (1) to develop a short-form version of the new Knee Society Knee Score; (2) to validate the short form against the full Knee Society Knee Score; and (3) to evaluate the responsiveness to treatment (TKA) of the new Knee Society short-form assessment. To develop the short form, data from the sample of 497 patients recruited during validation of the original long form the new Knee Society Knee Score were used. The multicenter study was approved by the institutional review boards at 15 participating medical institutions within the United States and Canada. An analytic item reduction approach was applied simultaneously but separately to preoperative and postoperative patient-reported data to select a subset of items from the original form that had good measurement properties and closely reflected the scores obtained using the original form. Expectations and satisfaction were reflected by a single item in the newly developed short form compared with a total of five satisfaction and three expectation items in the long form. The functional activities subscale was reduced from 17 to six items. An excellent correlation was demonstrated between function scores derived from the functional activities subscale of the original long-form score (17 items) and the six-item short form (r = 0.97; p < 0.01). The sample mean difference between the two scores was less than 4 points with a SD of 6.7 points. The short form was capable of discriminating clinically different groups of patients before and after TKA with virtually the same estimated effect size as the original functional activities subscale of the new Knee Society Knee Score. The Knee Society Knee Score long form is still recommended for research studies and for more sensitive measurement of the outcomes of individual patients. However, for general clinical use with large patient populations, the short form is expected to improve the rate of patient completion while also being easier to administer. In this study, we found the short-form version of the Knee Society Knee Score to be practical, valid, reliable, and responsive for assessing the functional outcome of TKA.

To evaluate the ability of computer-assisted surgery (CAS) to accurately size and determine rotational alignment of the femoral component in TKA, the author reviewed femoral component position after 50 consecutive primary TKAs using a femur-first, measured resection workflow. The computer software used allowed femoral rotation to be selected based on epicondylar axis, posterior condylar axis, or anteroposterior axis. The final femoral component size and position was determined by the surgeon to avoid anterior notching, match the posterior-medial condyle resection, and flexed to match the plane of the anterior femoral cortex. Femoral sizing was confirmed intraoperatively with a standard sizing guide. The femoral component was downsized in 52% of patients from the size recommended by the computer software. The posterior condylar axis matched the implanted rotational position of the femoral component to within 1 degrees in 64% of patients in contrast to the epicondylar axis (32%) and anteroposterior axis (26%). CAS provides information to make surgical decisions but does not replace clinical judgment. Landmark referencing may be compromised by limited surgical exposures leading to variation in implant positioning by computer software. A clear understanding of the principles of TKA is critical when using CAS to optimize implant sizing and position.

To correlate the amount of bone marrow edema (BME) calculated by magnetic resonance imaging(MRI) with clinical findings, histopathology, and radiographic findings, in patients with advanced hip osteoarthritis(OA). The study was approved by The Institutional Human Subject Protection Committee. Coronal MRI of hips was acquired in 19 patients who underwent hip replacement. A spin echo (SE) sequence with four echoes and separate fast spin echo (FSE) proton density (PD)-weighted SE sequences of fat (F) and water (W) were acquired with water and fat suppression, respectively. T2 and water:fat ratio calculations were made for the outlined regions of interest. The calculated MRI values were correlated with the clinical, radiographic, and histopathologic findings. Analyses of variance were done on the MRI data for W/(W + F) and for T2 values (total and focal values) for the symptomatic and contralateral hips. The values were significantly higher in the study group. Statistically significant correlations were found between pain and total W/(W + F), pain and focal T2 values, and the number of microfractures and calculated BME for the focal W/(W + F) in the proximal femora. Statistically significant correlations were found between the radiographic findings and MRI values for total W/(W + F), focal W/(W + F) and focal T2 and among the radiographic findings, pain, and hip movement. On histopathology, only a small amount of BME was seen in eight proximal femora. The amount of BME in the OA hip, as measured by MRI, correlates with the severity of pain, radiographic findings, and number of microfractures.

A sequential series of 366 primary total knee arthroplasties and 320 total hip arthroplasties was reviewed to determine the incidence of allogeneic transfusion. Surgery was performed under regional anesthesia and all patients had a hemovac drain for 24°. Tourniquet hemostasis in TKA was maintained through wound closure. Coumadin, SCD and TED hose were utilized for DVT prophylaxis. No additional blood conservation measures were employed. The transfusion incidence in primary TKA was 2.2% (males .6%/females 3.5%). The transfusion incidence in THA was 1.9%, (males .8%/females 2.6%). The low incidence of allogeneic transfusion in a contemporary series of primary TKA and THA, especially in males, would question the need for routine blood preservation techniques in this group of patients.

Acute lateral dislocation of the patella is a common clinical entity. The dislocation often reduces spontaneously or with the assistance of the patient or someone in attendance at the time of the injury. Very occasionally the patient presents to an emergency room with the patella still dislocated, and it is usually easily reduced at that time without an anesthetic by a physician. It is extremely rare to find an irreducible lateral dislocation of the patella, which cannot be reduced by manipulation even with a general anesthetic. A case is herein reported of an irreducible lateral dislocation of the patella that required open reduction followed by soft tissue reconstruction.

Three-hundred sixteen patients who underwent 405 primary knee replacements between January 1994 and June 1999 were reviewed for the incidence of local wound and systemic complications after unilateral and simultaneous bilateral total knee arthroplasties. A body mass index of 30 or greater was used to define obesity, and patients were divided into four groups based on obesity and whether they were undergoing unilateral or bilateral total knee arthroplasties. Preoperative and postoperative knee scores were not significantly different for any patient group. Local wound complication rates did not differ between any of the study groups. Patients who were not obese who underwent unilateral total knee arthroplasty had lower systemic complication rates (3%) than the other groups; however, there was no significant difference in complication rates between patients with obesity who underwent unilateral or simultaneous bilateral total knee arthroplasties. Based on these findings, obesity does not seem to be a contraindication to bilateral total knee arthroplasties under one anesthetic.

Linear and volumetric wear was measured in 33 tibial polyethylene inserts from three different cruciate-retaining knee systems retrieved at the time of revision surgery. Wear patterns also were evaluated and classified. Eccentric and asymmetric wear patterns were seen in 78% of inserts with flat articulating geometry versus 12% in inserts with curved anteroposterior geometry. The mean linear wear rate was .35 mm/year (range, .05-1.68 mm/year) and the mean volumetric wear rate was 794 mm3/year (range, 24-4088 mm3/year). Linear and volumetric wear rates showed a negative correlation with the length of implantation. Linear wear rates also showed a negative correlation with patient weight.

Objective. To examine the incidence, radiographic and histologic findings of medial femoral neck buttressing in a consecutive group of patients undergoing total hip arthroplasty. Design. Biomechanical parameters were evaluated on standard anteroposterior pelvic radiographs of 113 patients prior to hip replacement surgery. Demographic information on all patients was reviewed and histologic evaluation was performed on specimens obtained at the time of surgery. Results. The incidence of medial femoral neck buttressing was found to be 50% in a consecutive series of patients undergoing total hip arthroplasty. The incidence was slightly higher in women (56% vs 41%). Patients with buttressing had increased neck-shaft angles and smaller femoral neck diameters than were seen in patients without buttressing. Histologic evaluation demonstrated that the buttress resulted from deposition bone by the periosteum on the femoral neck in the absence of any evidence of femoral neck fracture. Conclusion. It would appear that femoral neck buttressing occurs in response to increased joint reactive forces seen at the hip being transmitted through the femoral neck. The increased joint reactive force can be related to the increased neck shaft angle seen in patients with buttressing.

A cell count and differential was obtained on synovial fluid samples from 79 total knee arthroplasties undergoing revision for aseptic failure over a 5-year period. The mean white blood cell count (WBC) was 782/mL (range, 11-7,200/mL). The mean percentage of monocyte cells was 87%, and the mean polymorphonuclear leukocyte (PML) cell count was 13%. Eight patients (10.4%) had leukocyte cell counts >2,000. Five knees in 4 patients with rheumatoid arthritis had PML counts >50%. There was a single postoperative infection. In patients with osteoarthritis as a primary diagnosis, a synovial WBC of

Experimental models that have been used to evaluate hip loading and the effect of hip implants on bone often use only a head load and abductor load. Anatomic considerations and in vivo measurements have lead several investigators to suggest that these models are inaccurate because they do not incorporate the loads imposed by additional muscles. The aim of this study was to evaluate the strains in the proximal and mid diaphysis of the femur for five hip loading models, one with a head load and abductor load only and four which incorporated lateral muscle loads as well. Head load to body weight load ratios were used to evaluate the physiologic accuracy of these models and strains were compared to determine the extent of strain changes as a function of model complexity. All models which incorporated additional lateral muscle loads more accurately simulated head load to body-weight load ratios than the simple abductor-only model. The model which incorporated a coupled vastus lateralis and iliotibial band load in addition to the abductor load provided the simplest configuration with a reasonable body-weight to head-load ratio.

Synovial fluid from the knees of 16 patients undergoing revision knee arthroplasty for aseptic failure was subjected to base digestion and ultrafiltration. Filtered particles were scanned using scanning electron microscopy and analyzed with an image program. Polyethylene particles were identified visually and confirmed with the use of electron diffraction spectroscopy. Averaging more than 1500 particles per patient sample, 25,148 particles were analyzed. This corresponded to a concentration of 3000 polyethylene particles per milliliter of synovial fluid. Three populations of wear debris were identified in the fluid. Small globular particles with a mean area of 75 mu 2 represented 94% of all particles observed. The particles averaged 10 mu in diameter and often were seen in clumps. Long fibrous particles with a mean area of 1164 mu 2 made up 4% of the particle population. Large rhomboidal particles with an area of 557 mu 2 were observed least commonly and comprised the remainder of the particles visualized. All three particle types were observed in each fluid sample regardless of the wear pattern of the retrieved polyethylene liner. There were no differences in absolute particle counts, particle morphologic characteristics, or particle size between patients with and without gross polyethylene wear.

Total knee arthroplasty with posterior cruciate ligament retention requires strict attention to the restoration of femoraland tibial anatomy, restoration of the joint line, and soft-tissue balancing. Component sizing and orientation are dependent on an understanding of normal knee anatomy and play a critical role in the success of the reconstruction. The results of knee arthroplasty with this technique have been excellent, and with continued refinements in prosthesis design and polyethylene manufacturing and sterilization, total knee arthroplasty with posterior cruciate ligament retention should continue to play a significant role in the management of patients with debilitating arthritis of the knee.

A review of 37 ankle arthrodesis procedures done over a 12-year period by multiple surgeons at a single institution was performed. Six different techniques were used during the study period. The initial success rate, defined as cases achieving a solid union after the index procedure, was 65%. Seven additional patients went on to a solid arthrodesis after subsequent surgical procedures, for an ultimate success rate of 84%. The initial success rate varied considerably depending on the surgical technique used, and ranged from 29% with the RAF fibular strut technique to 100% with T-plate fixation. Although there are many variables that influence the success or failure of ankle arthrodesis, in our hands rigid internal fixation gave the most predictable rate of primary union.

A biomechanical study was undertaken to evaluate the relative stability of three types of internal fixation used for ankle arthrodesis. Crossed screw fixation, RAF fibular strut fixation, and T-plate fixation were tested in 30 cadaver ankles using an MTS machine. T-plate fixation consistantly provided the stiffest construct when compared with the other types of fixation. Failure occurred by distraction of bony surfaces, posterior to the plane of fixation, in the crossed screw and RAF groups. In contrast, failure in the T-plate group occurred through compression of bone anterior to the midcoronal plane of the tibia. Although the stability of fixation is only one factor in determining the success or failure of ankle arthrodesis, the results of this study would support T-plate fixation over the other forms tested.

The Knee Society Clinical Rating System was developed in 1989 and has been widely adopted. However, with the increased demand for TKA, there is a need for a new, validated scoring system to better characterize the expectations, satisfaction, and physical activities of the younger, more diverse population of TKA patients.We developed and validated a new Knee Society Scoring System.We developed the new knee scoring system in two stages. Initially, a comprehensive survey of activities was developed and administered to 101 unilateral TKA patients (53 women, 48 men). A prototype knee scoring instrument was developed from the responses to the survey and administered to 497 patients (204 men, 293 women; 243 postoperatively, 254 preoperatively) at 15 medical institutions within the United States and Canada. Objective and subjective data were analyzed using standard statistical and psychometric procedures and compared to the Knee Injury and Osteoarthritis Score and SF-12 scores for validation. Based on this analysis, minor modifications led to the new Knee Society Scoring System.We found the new Knee Society Scoring System to be broadly applicable and to accurately characterize patient outcomes after TKA. Statistical analysis confirmed the internal consistency, construct and convergent validity, and reliability of the separate subscale measures.The new Knee Society Scoring System is a validated instrument based on surgeon- and patient-generated data, adapted to the diverse lifestyles and activities of contemporary patients with TKA. This assessment tool allows surgeons to appreciate differences in the priorities of individual patients and the interplay among function, expectation, symptoms, and satisfaction after TKA.

In 1989, The Knee Society Clinical Rating System [3] was developed as a simple, but objective scoring system to rate the knee and patient’s functional abilities such as walking and stair climbing before and after TKA. Since the scoring system did not include assessment of radiographs, The Knee Society endorsed a method to evaluate radiographs [2]. The Knee Society Clinical Rating System has been the most popular method of tracking and reporting outcomes after total and partial knee arthroplasty worldwide. However, the reliability, responsiveness, and validity of the original score have been challenged. In addition, it became clear over time that there were ambiguities and deficiencies with the original Knee Society Clinical Rating System that challenged its utility and validity in our contemporary patients, who often have expectations, demands, and functional requirements that are different from those of prior generations of patients who underwent knee arthroplasty. The Knee Society therefore embarked on a complete review of the previous system. The project started more than 3 years ago and involved Knee Society members from 18 institutions in the United States and Canada; these individuals contributed more than 500 cases of both preoperative and postoperative TKA. The magnitude of this exhaustive project involved a multidisciplinary team of arthroplasty surgeons, epidemiologists, and statisticians. The prior objective knee score was amplified from the prior Knee Society score to incorporate current knee arthroplasty clinical parameters. The functional component of the new score was developed on the basis of comprehensive inventories of the activities and observations of 101 patients at five major knee arthroplasty centers who completed a 120-item survey, which was ultimately condensed down to the current assessment tool. This assessment tool was then included in the validation process at the 18 participating centers. The final scoring system was then approved by the Knee Society Scoring Committee. The new Knee Society Knee Scoring System is both physician and patient derived. It includes versions to be administered preoperatively (Appendix 1) and postoperatively (Appendix 2). It has an initial assessment of demographic details, including an expanded Charnley functional classification [1]. The objective knee score, completed by the surgeon, includes a VAS score of pain walking on level ground and on stairs or inclines, as well as an assessment of alignment, ligament stability, and ROM, along with deductions for flexion contracture or extensor lag. Patients then record their satisfaction, functional activities, and expectations. Given the diverse activity profiles of many contemporary patients, the functional component of the score was improved to include a patient-specific survey, which evaluates features such as standard activities of daily living, patient-specific sports and recreational activities, patient satisfaction, and patient expectations. Portions of the original Knee Society Clinical Rating System have been integrated into the new version to maintain the integrity of the prior version of the Knee Society score. The new Knee Society Knee Scoring System has been developed and validated, in part, to better characterize the expectations, satisfaction, and physical activities of the younger and more diverse population of current patients undergoing TKA. The new score provides sufficient flexibility and depth to capture the diverse lifestyles and activities of our current patients. The score was validated in a thoughtful and methodical fashion confirming internal reliability and analyzed for differential item functioning [4]. The new Knee Society Scoring System is broadly applicable across sex, age, activity level, and implant type. In conclusion, the new Knee Society Scoring System is a validated and responsive method for assessing objective and subjective outcomes after total and partial knee arthroplasty, without the ambiguities of the prior scoring system. As physicians, clinical practices, and health systems become increasingly more responsible for reporting patient outcomes, the clear value of this new scoring system will become apparent. The new scoring system is available through application on the Knee Society Web site (http://www.kneesociety.org).

Biomechanical testing of orthopaedic implants in cadaver bone has provided valuable information. However, the reliability of these studies is often hampered by the wide variation in the mechanical properties of the substrate.'" Differences between samples have been attributed to vari- ations in location within the bone,',3 age, sex, and pre- existing metabolic condition~.~,~ A material with known consistent mechanical properties similar to those of human cancellous bone would provide an attractive alternative as a test substrate. Trabecular bone is made up of a porous network of connecting rods and plates. The stress-strain curve of trabecular bone under compression also has a similar appearance to that of a cellular f~am.~,~,'~ During the first phase of loading these materials exhibit a linear elastic response as the components of the material elastically compress or bend. At higher loads they begin to yield and the cell walls begin to collapse; under constant load they meet and touch. The resistance to load increases, giving rise to a final increasingly steep portion to the stress-strain curve.2Jo Daro foam (Daro Products, Butler, WI 53007) is a polyurethane foam formed by blending a resin and an isocyanate. It was originally developed to be used as a substitute for trabecular bone in mechanical testing by Hein et a1.l' Prior to polymerization the material can be poured or injected into a mold to form the desired shape and once it hardens it can be machined easily. By varying the ratio of resin to isocyanate the foam can be altered to produce a range of mechanical properties. Although it has been used by a number of other investigators in previous studies as a model for trabecular bone?,8J' the properties and preparation technique for the foams produced have not been reported. The purpose of this study was to report the mechanical properties and preparation technique for two compositions of Daro foam. In this study elastic modulus, yield, and

Pedestrians struck by motor vehicles have the highest mortality and morbidity rates of all motor-vehicle traumas. Fracture patterns and mechanisms were reviewed in a retrospective study of 115 consecutive patients. The most common fracture was tibia-fibula (39 patients), followed by pelvic (35 patients) and femur fractures (31 patients). A majority (90%) of long-bone fractures were the result of a direct-blow mechanism, and pelvic fractures were caused usually by lateral-compressive forces. Unstable pelvic and femur fractures both correlated with mortality (p less than 0.05), whereas tibia-fibula fractures (open or closed) did not. The triad of head, pelvis, and knee injuries traditionally associated with pedestrian motor-vehicle accident (MVA) victims was not found to occur with any statistical significance in this study group. Several characteristic fracture patterns were discovered: femur fractures associated with an accompanying pelvic fracture, and the ipsilateral dyad, an upper- and lower-extremity fracture on the same side, were found to occur with statistical significance (p less than 0.05). A lower extremity fracture warrants particularly close attention to the examination of the corresponding upper extremity, and a femur fracture should alert the clinician to the possibility of pelvic injury. The ipsilateral dyad has not been described previously in the literature and should be appreciated by physicians evaluating and treating pedestrian MVA victims.

The last two decades have witnessed tremendous strides in the evolution of acceptable and successful methods of prosthetic replacement for the arthritic joint. By and large, these techniques are predictable and durable, though not always to the complete satisfaction of the patient and surgeon. Despite the recent emphasis on alternative forms of implant fixation, cemented total joint replacements remain the standard by which all others are judged. In some settings, non-cemented implants appear to function as well as cemented ones in providing pain relief. The acetabular component in the hip and the femoral component in knee replacement are two such areas. This has resulted in the emergence of the "hybrid" joint replacement where one component is cemented while the other is not. The long-term function and durability of these non-cemented components remains to be seen. The future of joint replacement lies in the development of new "composite" materials which can more closely match the structural characteristics of the bone into which they are being implanted. Until we better understand and are able to prevent the disease processes which lead to total joint replacement, this area will continue to be the focus of intense research and development.

Ninety-nine patients undergoing primary total knee arthroplasty were prospectively evaluated for pre-resurfacing and post-resurfacing patellar thickness and medial patellar liftoff at 30 degrees of flexion without manual pressure on the patella. Regardless of medial patellar liftoff, no lateral releases were performed. Tibiofemoral angles, patellar tilt, and patellar congruence angles were measured preoperatively and postoperatively. There were no patellar subluxations, dislocations, or complications related to the patellofemoral joint. Patellar tilt improved from 7.9 degrees preoperatively to 3.8 degrees postoperatively. Patients with 10 mm or more of intraoperative liftoff improved from 9.9 degrees tilt preoperatively to 6.6 degrees postoperatively. Patients with no intraoperative liftoff had a change from 6.3 degrees to 2.9 degrees . Although the 2 groups were statistically different, the amount of change in alignment was not different between the groups. Patients with medial patellar liftoff at the time of arthroplasty do not appear to require lateral release to yield acceptable postoperative patellofemoral alignment.

The basic goal of fracture fixation is to stabilize the fractured bone, to enable fast healing of the injured bone, and to return early mobility and full function of the injured extremity. Fractures can be treated conservatively or with external and internal fixation. Conservative fracture treatment consists of closed reduction to restore the bone alignment. Subsequent stabilization is then achieved with traction or external splinting by slings, splints, or casts. Braces are used to limit range of motion of a joint. External fixators provide fracture fixation based on the principle of splinting. There are three basic types of external fixators: standard uniplanar fixator, ring fixator, and hybrid fixator. The numerous devices used for internal fixation are roughly divided into a few major categories: wires, pins and screws, plates, and intramedullary nails or rods. Staples and clamps are also used occasionally for osteotomy or fracture fixation. Autogenous bone grafts, allografts, and bone graft substitutes are frequently used for the treatment of bone defects of various causes. For infected fractures as well as for treatment of bone infections, antibiotic beads are frequently used.

Patients undergoing primary total knee arthroplasty (TKA) between 1989 and 1994 were evaluated preoperatively and postoperatively with the Knee Society scoring system at 3 time intervals: 1 to 2 years, 3 to 6 years, and more than 7 years. Knee prosthesis and functional scores improved statistically after TKA. At last follow-up evaluation, a statistically significant decline was found in functional knee scores that was related to an increase in numbers of patients in category C. Progression of arthritis at other sites, especially lumbar spine and hips, and cardiopulmonary problems were the most common cause of limited functional capacity. Women were found to have lower preoperative and postoperative functional scores. Patient weight, body mass index (BMI), and age at surgery showed no correlation with postoperative functional scores. The inclusion of functional categories would appear to be warranted when reporting long-term results of TKA.

A series of unicompartmental knee arthroplasty (UKA) revision to total knee arthroplasty (TKA) was compared to a group of primary TKAs performed at the same institution. The UKA revision group had a higher incidence of local wound complications and inferior clinical results as measured by Knee Society scores. When the revisions were stratified by the degree of interface constraint, knees revised with posterior cruciate ligament (PCL) substituting designs had superior knee scores that were comparable to the primary group. The use of a PCL-substituting knee design is recommended when converting a UKA to TKA.

A case of femoral component loosening secondary to impingement on an extended-lip acetabular cup liner is presented. This impingement led to the accelerated creation of particulate polyethylene wear debris. The particulate polyethylene induced an osteolytic response about the femoral component, which contributed to the failure of this component. It is recommended that intraoperative examination for impingement, especially in extension, be performed when using liners of this design.

In a prospective, multicenter study evaluating one revision knee system, 33 of 409 patients underwent morselized bone grafting for tibial and femoral defects. Fifty-four percent of defects were bicondylar and the defect volumes averaged 36 cc3. There was no difference in preoperative or postoperative knee scores between patients undergoing morselized grafting and the entire group. Radiographic evaluation showed remodeling of the grafted areas consistent with viable incorporation of the graft. The incidence of radiolucent lines, at 2 years followup, was not different between the patients who received grafting and the patients who did not receive grafting. There have been no clinical failures or reoperations in the patients who received morselized bone grafting. Morselized bone grafting seems to offer a viable alternative in the reconstruction of osseous defects in patients undergoing revision total knee arthroplasty.

Objective To review a regional experience with the treatment of snakebites. Setting Five major southern Arizona hospitals, including two Level I trauma centers. Design A review of all snakebite admissions over a five-year period was performed. Results During the period reviewed, 164 patients were admitted for snakebites. Rattlesnakes were responsible for 98 percent of identified envenomations. Thirty-six percent of the patients were transported by air to the admitting facility. Eighty percent of patients were admitted to the intensive care unit for an average of 1.6 days. Total hospital stays averaged 2.8 days. Ninety percent of patients received antivenin, usually only on the day of admission. Of those receiving antivenin, 20 percent had an anaphylactoid reaction, and 1 percent required readmission for serum sickness. Laboratory evaluation indicated abnormalities in platelet count, coagulation parameters, and fibrinogen levels, but these rarely required treatment. Thirteen percent of patients underwent surgical intervention, including a 4 percent fasciotomy rate, and a single amputation. Conclusion The use of field treatment, including "cut and suck," tourniquets, and cryotherapy, increased the likelihood of surgery. The authors concluded that the intensive care unit and helicopter transport system were overused. They recommend that established objective envenomation severity scores be used to dictate patient treatment, specifically the use of antivenin.

Numerous studies indicate that total knee arthroplasty (TKA) achieves excellent long-term success whether the posterior cruciate ligament (PCL) is saved or excised. In 13 patients, 16 PCL-retaining TKAs were identified with incapacitating instability secondary to early PCL deficiency. Patients with clinical PCL insufficiency present with a triad of subjective complaints: persistent swelling/effusions, anterior knee pain, and giving-way or instability episodes with activities of daily living. Of 13 patients, 12 had at least three postoperative visits with identical subjective complaints before PCL deficiency was diagnosed. On examination all patients exhibited effusion, posterior sag, positive quadriceps active test, and a visible anterior translation of the tibia on the femur while extending the leg from a seated, 90° flexed position. This sign has not been previously described to our knowledge but was present in all of our study patients. No patients had radiographic evidence of loosening or osteolysis. Joint aspiration was negative for infection in all patients. No patient had lateral patellofemoral maltracking. By radiographic measurement, the PCL-deficient knees had an average joint line elevation of 10.3 mm, compared with well-functioning TKAs which had an average joint line elevation of 5.0 mm. There was no correlation of PCL deficiency with excessive proximal tibial resection. Nonsurgical intervention provided no improvement in pain or instability. Six patients had improvement of pain, effusion, and stability after revision to a cruciate-substituting implant. We believe that this complication occurs more frequently than is currently being identified and should be considered in problem TKAs with normal radiographs.

Contact areas and pressures between native patellas and a prosthetic condylar design femoral component were measured at flexion angles of 30 degrees, 60 degrees, and 90 degrees. These were compared to measurements obtained with a domed all-polyethylene patellar component. Mean native patellar contact areas were found to be fourfold greater than seen with the prosthetic patellar component. Contact stresses in the native patellas were below the yield strength of articular cartilage in 80% of the contact area. By contrast, stresses measured in the prosthetic patella exceeded the yield strength of ultrahigh molecular weight polyethylene in 64% of the measured contact area. Contact areas and stresses were not significantly effected by flexion angle. Although contact areas and stresses reflect only a part of the dynamics of the patellofemoral articulation this information would support the selective retention of the native patella in total knee arthroplasty.

Recent studies have reported increased morbidity associated with bilateral simultaneous total knee arthroplasty (TKA). The purpose of this study was to evaluate the morbidity and clinical outcome associated with simultaneous bilateral TKA in contrast to unilateral TKA. All primary TKAs, either unilateral or simultaneous bilateral, performed between May 1988 and July 1993 were retrospectively reviewed. Patients were evaluated using Knee Society scores both before surgery and a minimum of 6 months after surgery. In addition to routine demographics, patients were evaluated for the incidence of both local wound and systemic complications. It is concluded that performing simultaneous bilateral TKA does not result in any significant increase in patient morbidity or compromise in postoperative function when compared with unilateral TKA.

A foam model of a protrusio acetabulum with cylindrical voids of varying diameters was used to test acetabular components for their ability to resist migration within the defect. A bipolar component, a hemispherical cup, and a hemispherical cup with peripheral rim augmentation were tested in defects with diameters ranging from 1 to 3 mm less than the major diameter of the component. The cup with peripheral rim augmentation demonstrated 20% to 40% greater resistance to migration than the hemispherical cup, depending on the extent of under-reaming, with the bipolar component consistently demonstrating the lowest load to failure. The results of this study confirm the less-than-satisfactory clinical results seen with bipolar reconstruction of protrusio acetabuli, and support the use of "fixed" cups in these settings.

Seven total knee arthroplasty systems were tested to determine contact stress patterns and contact areas using a calibrated Fuji film stress analysis technique. Knees were loaded to 2,000 N (204 kg) at 15 degrees, 60 degrees, 90 degrees, and 135 degrees flexion at 24 and 37 degrees C. Evaluation of stresses at 37 degrees C at 15 degrees and 60 degrees using an average contact stress assessment technique indicated that the LCS meniscal bearing knee system, (DePuy, Warsaw, IN), the AMK knee with a constrained insert (DePuy), and the PFC knee with a posterior-lipped insert (Johnson and Johnson, Raynham, MA) had the lowest average contact stresses (near or below 10 MPa). The PFC with a regular insert (Johnson and Johnson) the Ortholoc II (Dow Corning Wright, Arlington, TN), and the AMK with a regular insert (DePuy) had intermediate contact stresses. The AMK with a Hylamer-M insert (DePuy) and the MG II (Zimmer, Warsaw, IN) had the highest average contact stresses (near or above 20 MPa). A stress-calibrated Fuji film measurement technique has shown that an assessment of ranges of contact stress provides much more information about regions of expected wear than an assessment of average contact stresses. Testing of the tibiofemoral articulation of artificial knees revealed that all knees had some areas of contact with maximum stresses in excess of 15 MPa. As the yield strength of ultrahigh-molecular-weight polyethylene is approximately 15 MPa, all tibial inserts could wear to some extent. Peak contact stresses at four test angles of the AMK, Series 7000 (Osteonics, Allendale, NJ:) Genesis (Smith & Nephew Orthopaedics, Memphis, TN), and MG II patellofemoral articulations were high (above 30 MPa). Contact areas varied from line-shaped to bilateral circular or elliptical shapes. The LCS knee system experienced substantially lower patellofemoral contact stresses and larger contact areas. Changes in conformity of knee designs are warranted to overcome wear problems. Peak contact stresses measured from the LCS meniscal bearing tibiofemoral and patellofemoral joint were in excess of 30 MPa in some areas at low flexion angles. This design does create large areas of contact at very low contact pressures, however, and for this reason is expected to wear less than other designs.

Porous polyurethane foams were prepared from Daro foam components with a range of mechanical properties to simulate human trabecular bone. Ratios of 10.0:5.0, 10.0:7.9, and 10.0:10.0 isocyanate to resin were mixed, cured, and cut into cubes. Properties were determined from uniaxial compression to 50% of the original cube height at a strain rate of 1.2 mm/s. Electron microscopy was used to characterize the foam structure. Average compressive yield stress values, ultimate compressive stresses, and elastic moduli ranged from 4.44 to 2.79, 5.61 to 3.28, and 134.0 to 110.1 MPa, respectively, for the three formulations. The foam materials showed a similar morphology of spherical bubbles, and the average bubble size tended to decrease as the ratio of isocyanate to resin increased even though the bubble size differences were not statistically significant. The results indicate that large blocks of foam can be prepared with consistent mechanical properties simulating a range of trabecular bone properties so that implants can be tested for various patient populations.

We studied the relationship of the administration and dosage of steroids to the development of avascular necrosis of bone in 168 patients who had had a heart transplantation (156 patients) or a heart and lung transplantation (twelve patients). One hundred and forty-one of the patients were male and twenty-seven were female. The average age was forty-five years (range, seven to sixty-six years). The average duration of follow-up was forty months (range, twelve to eighty months). Avascular necrosis developed in five patients (3 per cent). The femoral head was involved in three patients (bilaterally in two and unilaterally in one), the medial femoral condyle was involved bilaterally in one, and several sites were involved in the fifth patient. The avascular necrosis was diagnosed an average of five months (range, two to eleven months) after the transplantation. In order to evaluate the influence of the dosage of the steroids on the development of avascular necrosis of bone, the doses of prednisone and Solu-Medrol (methylprednisolone) at one week, one month, six months, and one year after the transplantation were calculated for each patient. There was no association between the cumulative dose of prednisone and the development of avascular necrosis. There was, however, a strong statistical association (p = 0.005), as determined with pooled two-tailed variance analysis, between the cumulative dose of Solu-Medrol administered in the first month after the transplantation and the development of avascular necrosis.

A retrospective study of 53 patients with isolated femur fractures was performed to evaluate blood loss and transfusion incidence. Patients with other long bone fractures, abdominal, chest, mediastinal, and vascular injuries were excluded. Twenty-one patients required transfusion during the initial hospitalization averaging 2.5 units PRBCs. Admission hematocrit, preoperative and total EBL were found to be significant variables in determining transfusion. Fracture patterns, classified as high or low energy, were not found to correlate with pre- or intraoperative blood loss, incidence of transfusion, delay to surgery or duration of hospital stay. The estimated blood loss in the study group averaged 1,276 cc, stressing the significance of long bone fractures in trauma patients. Preoperative hemorrhage determined transfusion need in contrast to intraoperative blood loss.

A Weber type C ankle fracture was sequentially reproduced in 12 cadaver lower extremities and an external rotation torque was applied at each interval. The fractures were then repaired in staged fashion and the rotational stability of the mortise evaluated. Maximum external rotation of the talus within the mortise averaged 7.7 degrees in the intact ankle and increased by 311% to 31.8 degrees after creation of a Weber C injury. Rigid fixation of the fibular fracture restored 32% of the rotational stability, whereas isolated fixation of the medial malleolus reconstituted 57%. Fibular fixation combined with a syndesmotic screw restored 51% of original stability, and the addition of medial malleolar fixation improved stability to 101%. Bimalleolar fixation without a syndesmotic screw yielded 73% of the original rotational stability. The results of this study suggest that when rigid medial and lateral osteosynthesis can be achieved, syndesmotic fixation may not be necessary.

Polyethylene wear at the bearing surface of total hip prostheses can result in an inflammatory response that leads to periprosthetic osteolysis and aseptic loosening. Studies have demonstrated a reduction in wear in polyethylene with a more highly cross-linked molecular structure. The purpose of this study was to compare polyethylene wear on the basis of femoral head penetration in total hip prostheses with cross-linked polyethylene (XLPE) with those of standard polyethylene (non-XLPE). Femoral head penetration was evaluated in 74 patients. All hips were cemented stems with polished collarless prostheses and 28 mm CoCr femoral heads. Acetabular components were cementless hemispherical sockets with either XLPE or non-XLPE. The arthroplasties were performed because of degenerative joint disease in 54 hips, avascular necrosis in 8 hips, hip fracture in 4 hips, RA in 3 hips, psoriasis in 2 hips, AS in 1 hip, RA/AVN in 1 hip, and RA/fx in 1 hip. Linear polyethyelene wear was measured using the Livermore technique on standardized anteroposterior pelvic radiographs. The relationships between femoral head penetration (FHP) and implant material, gender, patient weight, and socket inclination were examined. Overall, the mean difference in FHP during the first year was not statistically significant when XLPE was compared with non-XLPE (p = .54). However, the comparison of FHP after the first year found that the FHP was lower for XLPE (p = .04). There were no significant differences in comparing FHP both during and after the first year by material and gender. The observed FHP for non-XLPE was greater than for XLPE both during and after the first year in males but only after the first year in females; however, the difference was not significant. Age has a significant negative relationship with FHP during the first year. The correlation between socket inclination and FHP was weak and not statistically significant (Rxy = .12, p = .307). These findings suggest that steady-state wear rates may be less in XLPE compared with non-XLPE after bedding-in has occurred in the first year. Bedding-in is a slow, plastic deformation in the direction of prevailing stress of the polyethylene and/or settling in of the liner. Radiographic methods for the assessment of polyethylene wear on the basis of femoral head penetration must be further developed to differentiate between plastic deformation of the polyethylene and actual polyethylene wear.

The pullout strengths of large diameter cannulated and noncannulated cancellous screws were tested in a synthetic polyurethane foam. The foam was fabricated to have mechanical properties equivalent to human cancellous bone and was characterized by compression testing before screw pullout. Long and short thread commercially available screws from four manufacturers were tested. In screws with short threads (16-22 mm), there was no difference in holding power among the four cannulated screw designs. However, the short thread noncannulated screw performed significantly better than the short thread cannulated screw with the lowest pullout strength. There were statistically significant differences in holding power among the different long thread (32-40 mm) cannulated screw designs. Additionally, the long thread noncannulated screw had better holding power than several of the long thread cannulated screws. No differences in pullout strengths between comparably sized cannulated and noncannulated screws produced by the same manufacturer were found, and all long thread screws had significantly greater holding power than all short thread screws. There was no demonstrable effect on holding power when screws were inserted with or without tapping. Thread surface area was found to be a reasonable predictor of holding power.

The pathogenesis of both Legg-Calve-Perthes disease (LCPD) and avascular necrosis (AVN) remains controversial. Evidence suggests, however, that both conditions are produced by vascular compromise in the femoral head. A patient with a previous history of LCPD at age eight subsequently developed AVN at age 46 after having a cardiac transplant for ischemic cardiomyopathy. A review of the past ten years' literature disclosed no reports of similar cases.

The biological effects of tumor necrosis factor (TNF) include the enhancement of fibroblast proliferation, the secretion of collagenase and prostaglandin E2 (PGE2) by fibroblasts, and the resorption of bone and cartilage, suggesting a role for this cytokine in arthritic conditions. To investigate this, we measured the levels of TNF in synovial fluids and evaluated its secretion by synovial fluid mononuclear cells and tissues from patients with rheumatoid arthritis, osteoarthritis, and seronegative arthritis and normals. TNF was found to be secreted in all arthritic conditions but not in normals. The levels of TNF were highest in synovial fluid and correlated with interferon-gamma (IFN-gamma) levels but not PGE2. The production of TNF was stable in a single joint for 3 to 6 months. Using immunohistochemical staining, TNF was localized to mononuclear cells in the lining layer, sublining, and perivascular areas of synovial tissue. The secretion of TNF by rheumatoid synovial fluid mononuclear cells was inhibited by PGE2, while IFN-gamma enhanced its production in those cells which were spontaneously secreting TNF. Our data suggest that TNF may play a role in various arthritic diseases.

One hundred fifteen consecutive pedestrians who were struck by motor vehicles were studied to determine the magnitude and patterns of the injuries sustained. The mortality rate was 22%, and 17 of 25 patients who died did so during the initial resuscitative efforts, primarily due to head, chest, and or abdominal injury. The average Injury Severity Score (ISS) among all patients was 20; however, it was significantly higher (46) in nonsurvivors. The majority of the victims were men (72%), and the average age of all patients was 35 years. As the patient's age increased, so did the likelihood of mortality, fractures, and prolonged hospital stay. Blood alcohol levels were measured in 85 patients, 65% of whom had detectable levels (mean, 0.25 mg/dL). There was no correlation between the presence of alcohol and mortality, ISS, head injury, or number of fractures. The most frequently injured organ system was musculoskeletal (77%), followed by head (34%), abdomen (21%), and chest (15%). The most common fractures seen were tibia-fibular (39), pelvis (35), and femur (31). Hospital stay averaged 11 days, and patients charges averaged $16,900.

A study was undertaken to evaluate the strength and ease of application of four different forms of patellar fracture fixation. Modified tension band, screw fixation, Lotke longitudinal anterior band (LAB), and Magnusson wiring were examined using a Materials Testing System. Using cadaver lower extremities, the tibia was mounted in a fixed base and the tibiofemoral joint was fixed at 36 degrees. Tension was applied to the patella through the quadriceps tendon and fracture displacement was measured with linear motion transducers. Based on the results, we recommend screw fixation for transverse patellar fractures in patients with adequate bone stock. In patients with patellar fractures with comminution and/or osteopenia, modified tension band fixation is recommended. Simple wiring techniques alone may not provide sufficient fixation to allow immediate range of motion.