James B. Benjamin

Bone marrow edema pattern in advanced hip osteoarthritis: quantitative assessment with magnetic resonance imaging and correlation with clinical examination, radiographic findings, and histopathology.

ObjectiveTo 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).Materials and methodsThe 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.ResultsAnalyses 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.ConclusionThe amount of BME in the OA hip, as measured by MRI, correlates with the severity of pain, radiographic findings, and number of microfractures.

Development of a New Knee Society Scoring System

BackgroundThe 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.Questions/purposesWe developed and validated a new Knee Society Scoring System.MethodsWe 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.ResultsWe 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.ConclusionsThe 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.

Early, incapacitating instability of posterior cruciate ligament-retaining total knee arthroplasty

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 degree 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.

AVERAGE AND PEAK CONTACT STRESS DISTRIBUTION EVALUATION OF TOTAL KNEE ARTHROPLASTIES

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.

Comparison of the subvastus and paramedian surgical approaches in bilateral knee arthroplasty

A prospective randomized study was performed on 20 patients undergoing one-stage bilateral knee arthroplasty. One knee was exposed using a standard median parapatellar arthrotomy and the other knee with a subvastus arthrotomy. All patients underwent quantitative strength testing before surgery and at 1 week, 1 month, and 3 months after surgery. The knees were also evaluated for range of motion, and patients, who were blinded as to the approach used, completed questionnaires at each evaluation period as to their preference, if any, regarding knee pain and level of function. There was no difference in the range of motion between knees exposed with the paramedian or subvastus arthrotomy at any time period. The subvastus knees demonstrated significantly greater strength at the 1-week and 1-month intervals, but there was no strength difference at the 3-month interval. There were more lateral releases performed in the paramedium knees, and three minor complications were related to the subvastus approach. Patients who expressed a preference chose the subvastus knee 4:1 over the paramedian knee. The subvastus approach offers a reasonable alternative to the paramedian arthrotomy and preserves greater quadriceps strength in the early postoperative period.

Characteristics of tumor necrosis factor production in rheumatoid arthritis

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.

Biomechanics of the wrist.

The wrist joint is a complex linkage between forearm and hand which is capable of an impressive arc of motion yet retaining a remarkable degree of stability. Carpal stability is derived from numerous intra-and intercarpal ligaments in addition to closely approximated wrist flexors and extensors. Motion occurring at the carpus is predominantly biplane--radial ulnar deviation and palmar flexion and extension. The center of motion for these planes of movement is located within the proximal and palmar pole of the capitate. When painful conditions arise at the wrist, a loss of wrist motion usually follows. Occasionally a loss of volitional control over wrist extensors is noted with the abnormal recruitment of wrist flexors with finger flexor activity. When instability and pain co-exist at the wrist, deformity can arise as a result of the inherent motor imbalance noted between the 6 wrist motors. Vector force analyses disclose that the flexor carpi ulnaris is the dominant wrist motor with the least significant force being supplied by the extensor carpi radialis longus. Although wrist motion is not essential for most activities of daily living, the preservation of wrist motion is for some individuals essential for the performance of specific occupational or recreational activities.

Safety and efficacy of bilateral 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.

Biomechanical evaluation of various forms of fixation of transverse patellar fractures

Summary: 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°. 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.

Avascular Necrosis of Bone after Cardiac Transplantation. Prevalence and Relationship to Administration and Dosage of Steroids.

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.