Jean-Noël Argenson

Modern unicompartmental knee arthroplasty with cement: a three to ten-year follow-up study.

Background: Unicompartmental arthroplasty is a treatment alternative when only one compartment of the knee is affected with arthritis, but the reported results of this procedure have been variable. The purpose of the present study was to evaluate the results of a modern unicompartmental knee arthroplasty performed with use of a cemented metal-backed prosthesis and surgical instrumentation comparable with that used for total knee replacement.Methods: The indications for the procedure were osteonecrosis or osteoarthritis associated with full-thickness loss of cartilage that was limited to one tibiofemoral compartment as evaluated on standing and stress radiographs. One hundred and sixty consecutive cemented metal-backed Miller-Galante prostheses in 147 patients were evaluated after a mean duration of follow-up of sixty-six months (range, thirty-six to 112 months). The mean age of the patients at the time of the index procedure was sixty-six years.Results: Three knees were revised because of progression of osteoarthritis in the patellofemoral joint (two knees) or the lateral tibiofemoral compartment (one knee). Two knees had revision of the polyethylene liner. The average Hospital for Special Surgery knee score improved from 59 points preoperatively to 96 points at the time of the review. According to Kaplan-Meier analysis, the ten-year survival rate (with twenty-nine knees at risk) was 94% ± 3% with revision for any reason or radiographic loosening as the end point.Conclusions: A modern unicompartmental knee arthroplasty is a valid alternative for patients with unicompartmental tibiofemoral noninflammatory disease. The patient selection must be strict with regard to the status of the patellofemoral joint. The preoperative planning includes stress radiographs to assess the correction of the deformity and the status of the uninvolved compartment. Continued long-term follow-up is necessary to evaluate long-term polyethylene wear.

Validation and Usefulness of a Computer-assisted Cup-positioning System in Total Hip Arthroplasty: A Prospective, Randomized, Controlled Study

BACKGROUND Malpositioning of the acetabular component during total hip arthroplasty increases the risk of dislocation, reduces the range of motion, and can be responsible for early wear and loosening. The purpose of this study was to compare computer-assisted with freehand insertion of the acetabular component. METHODS A randomized, controlled, matched prospective study of two groups of thirty patients each was performed. In the first group, cup positioning was assisted by an imageless computer-assisted surgical system based on bone morphing. In the control group, the cup was placed freehand. All of the patients were operated on by the same surgeon through an anterolateral approach. Cup anteversion and abduction angles were measured on three-dimensional computed tomography reconstructions postoperatively for each patient by an independent observer using special cup-evaluation software. RESULTS There were sixteen men and fourteen women in each group, and the mean body-mass index was approximately 25 in each group. The computer-assisted procedure took a mean of twelve minutes longer than the freehand procedure. Fifty-seven percent (seventeen) of the thirty cups placed freehand and 20% (six) of the thirty in the computer-assisted group were outside of the defined safe zone (outliers). This difference was significant (p = 0.002). There were no differences between the computer-assisted group and the freehand-placement group with regard to the mean abduction and anteversion angles, but there was a significant heterogeneity of variances, with the lowest variations in the computer-assisted group. CONCLUSIONS Use of an imageless navigation system can improve cup positioning in total hip arthroplasty by reducing the percentage of outliers.

Three-dimensional morphology of the proximal femur

In the field of uncemented hip arthroplasties, secondary biologic fixation of femoral implants depends directly on the quality of the primary stability. Metaphyseal filling and a good fit between the implant and the proximal femur improve initial stabilization and optimize the transmission of forces to the bone. Precise knowledge of the three-dimensional femoral shape is essential to the design and selection of adapted implants. Three hundred ten femurs in 300 patients suffering from primary hip osteoarthritis were analyzed by computed tomography scanning. After three-dimensional reconstruction, several measurements were extracted, and the parameters essential to the characterization of the diverse femoral morphologies encountered were identified. A new classification of the proximal femur is proposed. The consequences on the design and the preoperative selection of femoral implants are discussed.

A high flexion total knee arthroplasty design replicates healthy knee motion.

Deep flexion affects both femorotibial contact pattern and the patellofemoral articulation. The purpose of this study was to compare the patellofemoral motion of nonimplanted and implanted knees and to analyze femorotibial kinematics after total knee replacement designed for deep flexion. Three-dimensional patellofemoral kinematics were evaluated during a deep knee bend using fluoroscopy for five control patients with a healthy knee, five patients with an anterior-cruciate-ligament-deficient knee, and 20 patients who had a high flexion total knee arthroplasty. Less translation of patellofemoral contact position was seen in patients who had knee replacements than in patients with healthy knees, but the average motion and the patella tilt angles were similar to the healthy knees. On average, patients who had a total knee arthroplasty had 4.9° normal axial rotation, and all patients had at least −4.4 mm of posterior femoral rollback. The average weightbearing range of motion of the patients in the total knee arthroplasty group was 125°. In this study, patients implanted with a high-flexion knee replacement design had kinematic patterns that were similar to the healthy knee. It can be hypothesized that forces acting on the patella were not substantially increased for patients who had a total knee arthroplasty compared with the control patients.

Anatomy of the Dysplastic Hip and Consequences for Total Hip Arthroplasty

Total hip arthroplasty in dysplastic hips is challenging because of the modified anatomy of the proximal femur and acetabulum. We studied three-dimensional anatomic parameters in 247 dysplastic hips from 218 adult patients using radiographs and computed tomography, and analyzed the consequences for total hip arthroplasty. A cohort of 310 primary osteoarthritic hips was used as a control group. According to the classification of Crowe et al, 78 of the dislocated hips were graded Class I, 26 as Class II, 20 as Class III or IV, and 169 dysplastic hips had no subluxation. Compared with primary osteoarthritis, the intramedullary femoral canal had reduced mediolateral and anteroposterior dimensions. With high grade subluxations the femoral neck shaft angle decreased but with low grades, especially in Class II, the neck shaft angle increased. The proximal femur had more anteversion with individual variations ranging from 1° to 80°. The true acetabulum had a reduced anteroposterior diameter. The large individual morphologic variability across all levels of dysplastic hips suggests the femoral prosthesis cannot be chosen on the basis of the severity of the subluxation alone.

Modern unicompartmental knee arthroplasty with cement: a concise follow-up, at a mean of twenty years, of a previous report.

We previously evaluated the three to ten-year results of 160 consecutive unicompartmental knee arthroplasties that had been performed by two surgeons in 147 patients with use of the cemented metal-backed Miller-Galante prosthesis. The average age of the patients at the time of the index procedure was sixty-six years. The purpose of the present study was to report the updated results of this series after a mean duration of follow-up of twenty years. Sixty-two patients (seventy knees) were living, and seven had been lost to follow-up. Eleven knees had undergone conversion to total knee arthroplasty, three had had an addition of a patellofemoral prosthesis, and five had had polyethylene exchange. Ten knees had had revision since the three to ten-year evaluation. The reasons for revision included progression of osteoarthritis in twelve knees, aseptic loosening (which had been absent at the three to ten-year evaluation) in two knees, and polyethylene wear (which was treated with liner exchange at an average of twelve years) in five knees. The average clinical and functional Knee Society scores were 91 and 88 points, respectively, at the time of the latest follow-up. The average flexion was 127° (range, 80° to 145°). We concluded that modern cemented metal-backed unicompartmental implants, evaluated at a mean of twenty years of follow-up in patients with osteoarthritis that was limited to one tibiofemoral compartment of the knee, provided durable pain relief and long-term restoration of knee function without compromising future conversion to conventional total knee arthroplasty.

Medial unicompartmental knee replacement in the under-50s

We retrospectively reviewed 35 cemented unicompartmental knee replacements performed for medial unicompartmental osteoarthritis of the knee in 31 patients </=50 years old (mean 46, 31 to 49). Patients were assessed clinically and radiologically using the Knee Society scores at a mean follow-up of 9.7 years (5 to 16) and survival at 12 years was calculated. The mean Knee Society Function Score improved from 54 points (25 to 64) pre-operatively to 89 (80 to 100) post-operatively (p < 0.0001). Six knees required revision, four for polyethylene wear treated with an isolated exchange of the tibial insert, one for aseptic loosening and one for progression of osteoarthritis. The 12-year survival according to Kaplan-Meier was 80.6% with revision for any reason as the endpoint. Despite encouraging clinical results, polyethylene wear remains a major concern affecting the survival of unicompartmental knee replacement in patients younger than 50.

Unicompartmental knee arthroplasty for avascular osteonecrosis.

The data analyzing clinical and radiological outcomes after modern unicompartmental knee arthroplasty (UKA) for spontaneous and secondary avascular osteonecrosis are limited. We determined whether: (1) UKA for osteonecrosis was as reliable for alleviating pain and improving function (measured by Knee Society scores) as it is for osteoarthritis, (2) lower limb alignment could be restored after UKA for osteonecrosis, and (3) UKA for osteonecrosis is as durable as UKA for osteoarthritis (measured by survivorship at 12 years). We retrospectively reviewed 30 patients (31 knees) with osteonecrosis; 21 knees had spontaneous osteonecrosis and 10 had secondary osteonecrosis. Mean patient age was 71 years. Clinical and radiological evaluations were performed by an independent observer at a minimum followup of 3 years (mean, 7 years; range, 3-16 years). Reliable pain relief and function improvement were obtained in 30 knees (96%). Restoration of an appropriate lower-limb mechanical axis was achieved for 27 knees (88%). The Kaplan-Meier survivorship was 96.7% at 12 years. Our data suggest UKA is a reasonable solution for restoring clinical function and radiological lower-limb alignment for spontaneous or secondary osteonecrosis limited to one compartment of the knee, with a durable survivorship.Level of Evidence: Level IV, retrospective study. See the Guidelines for Authors for a complete description of levels of evidence.

In vivo three-dimensional determination of kinematics for subjects with a normal knee or a unicompartmental or total knee replacement.

Understanding the in vivo motions of human joints has become increasingly important. Researchers have used in vitro (cadavers), noninvasive (gait laboratories), and in vivo (fluoroscopy) approaches to assess human knee motion. Unfortunately, previous attempts have been unable to track the in vivo bearing-surface motion of the medial and lateral condyles of the normal knee in three dimensions. The objective of this study was to use fluoroscopy and computed tomography to accurately determine the three-dimensional, in vivo, weight-bearing motion of the normal knee. ### Methods Five normal knees, clinically determined to have no pain or ligamentous laxity, were analyzed. With use of computed tomography scanning, slices of the femur beginning 6 in (15.2 cm) proximal to the joint line and slices of 6 in of the proximal part of the tibia (1.0-mm slices near the bearing surfaces and 3.0-mm slices elsewhere) were obtained (Fig. 1). Three-dimensional bone models (Fig. 2-A) of each subject’s femur, tibia, patella, and fibula were recreated from the three-dimensional volume data (Fig. 2-B). Each subject was then asked to perform five weight-bearing activities—deep knee bend, normal gait, rising from a chair, sitting down in a chair, and descending stairs—while under fluoroscopic surveillance. The fluoroscopic images of each knee during each activity were downloaded to a computer workstation. The computer-generated three-dimensional models of each subject’s femur and tibia were overlaid onto the two-dimensional fluoroscopic images and subsequently were analyzed at various knee-flexion angles. For each activity, femorotibial contact paths were determined for both the medial and the lateral condyle and were plotted with respect to knee-flexion angle. Femorotibial contact anterior to the tibial midline in the sagittal plane was denoted as positive, and posterior contact was denoted as negative. Fig. 1: Computed tomography slice of a normal knee. Fig. 2-A: Three-dimensional computed-aided-design models of the normal patella, femur, tibia, and fibula generated from a …

The Outcome of Rotating-Platform Total Knee Arthroplasty with Cement at a Minimum of Ten Years of Follow-up

BACKGROUND Durable, long-term results have been reported for patients managed with first-generation mobile-bearing total knee arthroplasty. Second-generation mobile-bearing total knee arthroplasty has been introduced to enhance instrumentation, to increase flexion, and to improve functional outcome, but, to our knowledge, no long-term results are available. METHODS From May 1999 to June 2000, 116 consecutive rotating-platform total knee arthroplasties were performed by the two senior authors in 112 patients with use of the LPS-Flex Mobile cemented prosthesis, which was implanted with a measured resection technique. The patella was resurfaced in every knee. The average age of the patients at the time of surgery was sixty-nine years (range, thirty-seven to eighty-five years), and seventy-seven patients (eighty knees) were women. The predominant diagnosis was osteoarthritis. The clinical and radiographic evaluation was performed with use of the Knee Society rating system. The level of activity and patient-reported functional outcome were evaluated with use of the University of California at Los Angeles (UCLA) score and the Knee injury and Osteoarthritis Outcome Score (KOOS), respectively. RESULTS The average duration of follow-up was 10.6 years (range, ten to 11.8 years). Three patients were lost to follow-up, and five patients died of causes unrelated to knee arthroplasty. Two knees were revised, one because of infection and one because of failure of the medial collateral ligament. Kaplan-Meier survivorship analysis showed an implant survival rate of 98.3% at ten years. For the 104 patients (108 knees) who were evaluated at a minimum of ten years, the average Knee Society knee and function scores improved from 34 to 94 points and from 55 to 88 points, respectively, at the time of the latest follow-up. There was no periprosthetic osteolysis and no evidence of implant loosening on follow-up radiographs. The average knee flexion was 117° preoperatively and 128° at the time of the latest follow-up evaluation. At the time of the latest follow-up, the KOOS quality-of-life score was significantly better for patients with >125° of flexion (p = 0.00034). CONCLUSIONS This study demonstrated durable clinical and radiographic results at a minimum of ten years after total knee replacement with a second-generation, cemented, rotating-platform, posterior-stabilized total knee prosthesis. According to the functional outcome results obtained in this study, we believe that this design is a valuable option for active patients undergoing total knee arthroplasty.