John S. Xenos

The tibiofibular syndesmosis. Evaluation of the ligamentous structures, methods of fixation, and radiographic assessment.

Twenty-five fresh-frozen cadaveric specimens were used to evaluate the role of the syndesmotic ligaments when the ankle is loaded with external rotation torque. An apparatus was constructed that allowed pure external-rotation torque to be applied through the ankle with the foot in neutral flexion. The apparatus provided solid fixation of the tibia while allowing free movement of the fibula in all planes. The syndesmotic ligaments were incrementally sectioned, and direct measurements of anatomical diastasis were made. Mortise and lateral radiographs were made at each increment under both loaded (5.0 newton-meters) and unloaded conditions. After all structures of the syndesmosis had been divided, the syndesmosis was reduced and was repaired with one or two screws. The strength of the repair was measured with incremental increases in torque of 1.0 newton-meter. The radiographs were measured by three independent observers in a blind fashion. In order to evaluate intraobserver error, each observer was randomly given forty radiographs to reinterpret. Diastasis and rotation were found to be related to the amount of injury of the ligament (p < 0.0001). After the entire syndesmosis had been divided, application of a 5.0-newton-meter torque resulted in a mean diastasis of 7.3 millimeters. The subsequent repair of the anterior tibiofibular ligament with suture failed at a mean of 2.0 newton-meters (range, 1.0 to 6.0 newton-meters) of torque. Repair with two screws was found to be stronger than repair with one, with the first construct failing at a mean of 11.0 newton-meters (range, 5.0 to 15.0 newton-meters) and the second, at a mean of 6.2 newton-meters (range, 2.0 to 10.0 newton-meters) (p = 0.0005). Failure of the screw fixation was not associated with the maximum previous diastasis (p = 0.13). Measurements of anatomical diastasis were compared with measurements made on the mortise and lateral radiographs. Measurements on the stress mortise radiographs had a weak correlation with diastasis (r = 0.41, p < 0.0001). However, measurements on the stress lateral radiographs had a higher correlation (r = 0.81, p < 0.0001). Additionally, interobserver correlation was significantly higher for the measurements on the lateral radiographs (r = 0.87, p < 0.0001) than for those on the mortise radiographs (r = 0.56, p < 0.0001). Intraobserver correlation for the three observers was poor with regard to the measurements on the mortise radiographs (r = 0.12, 0.42, and 0.25). The respective correlations for the measurements on the lateral radiographs were r = 0.81, 0.90, and 0.89.(ABSTRACT TRUNCATED AT 400 WORDS)

The Porous-coated Anatomic Total Hip Prosthesis, Inserted without Cement. Results after Five to Seven Years in a Prospective Study.

The results of 100 primary arthroplasties with a porous-coated anatomic total hip prosthesis that were performed consecutively in ninety-one patients were followed prospectively for five to seven years after the operation or until death. Clinical Harris hip ratings and anteroposterior and lateral radiographs were made preoperatively, several times in the first postoperative year, and at annual intervals thereafter. Average sequential hip ratings were maintained between 92 and 93 points during the follow-up interval. Pain in the thigh, which did not limit function, was recorded at the yearly examinations from the first to the fifth year. After one year, 18 per cent of the thighs were painful, and in succeeding years, 19 per cent, 23 per cent, 26 per cent, and 15 per cent were painful. Radiographs demonstrated that the fixation of the femoral component was by ingrowth of bone in 94 per cent of the hips, by stable fibrous fixation in 1 per cent, and by unstable fibrous fixation in 5 per cent, according to the criteria of Engh et al. By five years, 6 per cent of the acetabular components had migrated, and 5 per cent of the femoral components had subsided. Two acetabular components had been revised, and one revision of a femoral component was pending. The evaluated device was an early-generation prosthesis that was designed for insertion without the use of cement. Further study is necessary to determine the long-term durability of the prosthesis-bone interface.

The Porous-Coated Anatomic Total Hip Prosthesis, Inserted without Cement. A Prospective Study with a Minimum Ten Years of Follow-up*

One hundred consecutive primary total hip arthroplasties performed with use of a porous-coated anatomic total hip prosthesis, fixed without cement, in ninety-one patients were followed prospectively for a minimum of ten years. At the time of the most recent follow-up, twenty patients (twenty-three hips) had died and seventy-one patients (seventy-seven hips) were living. The average age of the living patients was sixty-six years (range, thirty-two to ninety-two years), and their average Harris hip score was 84 points (range, 33 to 100 points). Twelve percent (nine) of the seventy-seven hips were found to be associated with pain in the thigh when the patients were specifically questioned by the examiner. Eleven hips were revised during the follow-up period. Only the acetabular component was revised in six hips, only the femoral component was revised in one hip, and both the femoral and the acetabular components were revised in four hips. Of the ten acetabular revisions, one was performed because of acute dissociation of the component and eight, because of a combination of polyethylene wear, osteolysis, and loosening; the tenth acetabular revision consisted of exchange of the liner and curettage and bone-grafting of the osteolytic area. Of the five femoral revisions, two were performed because of loosening and three, because of extensive osteolysis of the proximal aspect of the femur. Including the revised components, twelve acetabular components and five femoral components had radiographic evidence of aseptic loosening. Acetabular osteolysis occurred in seventeen hips. Femoral osteolysis occurred in thirty-nine hips: in the proximal aspect of thirty-one hips, in the distal aspect of four, and in both the proximal and the distal aspect of four. The durability of the femoral fixation documented in this study is especially encouraging in view of the fact that this was our initial experience with devices fixed without cement and that a so-called first-generation femoral component was used. However, the study also demonstrated that not all acetabular components fixed without cement function well over the long term and that specific design considerations (adequate initial fixation, congruency between the liner and the shell, an optimum shell-liner capturing mechanism, and a smaller femoral head) are warranted.

Radiographic definition of pelvic osteolysis following total hip arthroplasty

BACKGROUND Radiographs are the standard clinical tool used to monitor patients with pelvic osteolysis after total hip arthroplasty; however, previous reports have questioned the value and accuracy of this method. With use of a cadaveric model, we investigated the accuracy of radiographs in determining the location and size of periacetabular osteolysis. METHODS We implanted total hip arthroplasty components in eight cadaveric hips and made four radiographs of each hip from different views. We then removed the components and created two pelvic defects in each hip. We measured the volume of each defect, reimplanted the components, and made another set of radiographs. The defects were then enlarged two more times, with the volume measured and another set of radiographs made each time. In total, 128 radiographs were made of forty-eight lesions. An orthopaedist who was blinded to the location of the lesions assessed the radiographs with regard to the presence and size of osteolytic lesions. RESULTS The overall sensitivity for the detection of osteolysis on a single radiograph was 41.5%, and the overall specificity was 93.0%. Sensitivity was dependent on the location and size of the lesions but not on the radiographic view. Sensitivity ranged from 72% for lesions in the ilium to </=15% for lesions in the ischium and acetabular rim. The detection rate for lesions with a volume of >10 cm (3) was significantly higher than that for smaller lesions (p < 0.001). When all four radiographic views of one lesion were analyzed together, sensitivity increased to 73.6%. Despite the low sensitivity, specificity remained high, indicating that once osteolysis is evident radiographically, the likelihood that a lesion truly exists is high. Additionally, we found that the extent of osteolysis was substantially underestimated on radiographs. CONCLUSIONS The use of radiographs to assess and monitor osteolysis has both limitations and merits. Using multiple views, an experienced orthopaedist identified only 73.6% of pelvic lesions. However, once a pelvic osteolytic lesion is evident radiographically, the likelihood that it truly exists is high.

Results of porous-coated anatomic total hip arthroplasty without cement at fifteen years: a concise follow-up of a previous report.

Abstract: The purpose of this study was to update the results of a prospective series of primary cementless total hip arthroplasties after a minimum of fifteen years of follow-up. It is one of the first studies of cementless total hip arthroplasties followed for a minimum of fifteen years.One hundred consecutive Porous Coated Anatomic (PCA) total hip replacements were implanted between October 1983 and January 1986. Fifty-five patients (sixty-four hips) that were alive at a minimum of fifteen years postoperatively are the focus of the present study. At this time of follow-up, at an average of 15.6 years (range, fifteen to seventeen years) after the total hip arthroplasty, 17% (seventeen hips) of the entire cohort and 23% (fifteen hips) of the living cohort had undergone revision because of loosening of the acetabular component or osteolysis. Seven percent (seven hips) of the entire cohort and 6% (four hips) of the living cohort had undergone revision for loosening of the femoral component or osteolysis. Only four femoral stems had been revised for isolated loosening (without osteolysis).The PCA femoral component proved to be durable at a minimum of fifteen years postoperatively, while the acetabular component was less durable.Level of Evidence: Therapeutic study, Level IV (case series [no, or historical, control group]). See Instructions to Authors for a complete description of levels of evidence.

Osteoporosis and anterior femoral notching in periprosthetic supracondylar femoral fractures: a biomechanical analysis.

Background: This biomechanical study was designed to evaluate the predictive ability of dual-energy x-ray absorptiometry, cortical bone geometry as determined with computed tomography, and radiography in the assessment of torsional load to failure in femora with and without notching.Methods: Thirteen matched pairs of cadaveric femora were randomized into two groups: a notched group, which consisted of femora with a 3-mm anterior cortical defect, and an unnotched group of controls. Each pair then underwent torsional load to failure. The ability of a number of measures to predict femoral torsional load to failure was assessed with use of regression analysis. These measures included dual-energy x-ray absorptiometry scans of the proximal and the distal part of the femur, geometric measures of both anterior and posterior cortical thickness as well as the polar moment of inertia of the distal part of the femur as calculated on computed tomography scans, and the Singh osteoporosis index as determined on radiographs.Results: The torsional load to failure averaged 98.9 N-m for the notched femora and 143.9 N-m for the controls; the difference was significant (p < 0.01). Although several variables correlated with torsional load to failure, distal femoral bone-mineral density demonstrated the highest significant correlation (r = 0.85; p < 0.001). Moreover, multiple regression analysis showed that a combination of distal femoral bone-mineral density and polar moment of inertia calculated with the posterior cortical thickness (adjusted r 2 = 0.79; p < 0.001) had the strongest prediction of torsional load to failure in the notched group. The addition of other measures of cortical bone geometry, proximal femoral bone-mineral density, or radiographic evidence of osteopenia did not significantly increase the models predictive ability.Conclusions: Femoral notching significantly decreases distal femoral torsional load to failure and is best predicted by a combination of the measures of distal femoral bone-mineral density and polar moment of inertia. Together, these values account for the amount of bone mass present and the stability provided by the cortical shell architecture.Clinical Relevance: Femoral notching during total knee arthroplasty decreases distal femoral torsional load to failure. By examination of femoral bone density and distal femoral geometry, the relative decrease in torsional load to failure can be predicted and appropriate precautions taken.

Second-generation Porous-coated Cementless Total Hip Arthroplasties Have High Survival

We retrospectively reviewed 157 consecutive total hip arthroplasties performed with Prodigy® stems and Duraloc® cups to see whether design modifications made to these components would improve their clinical performance as compared with first-generation porous-coated components. At an average of 6.7 years postoperatively, 145 hips were available for followup. The data suggested encouraging clinical and radiographic performances for these second-generation components. With only two hips (1.4%) in this population being revised, survivorship analysis was 99% 5 years postoperatively. Bone ingrowth was evident in 99% of the stems, and all cups were stable at last followup. Large osteolytic lesions were observed in three acetabula and seven femurs with all femoral lesions being confined to the proximal Gruen Zones 1 or 7. Polyethylene wear averaged 0.10 ± 0.14 mm/year. Ninety-eight percent of patients reported satisfaction with the procedure, and 7% reported activity-limiting pain. Early followup of the Prodigy-Duraloc® combination in primary cementless total hip arthroplasties showed the Prodigy® stem had similarly good clinical results compared with its predecessor, the AML stem, and the Duraloc® cup was superior to its first-generation predecessor, the anatomic medullary locking cup with Acetabular Cup System (ACS) liner. Level of Evidence:Therapeutic Level III (retrospective cohort). See the Guidelines for Authors for a complete description of levels of evidence.