A third-generation, posterior-stabilized knee prosthesis: early results after follow-up of 2 to 6 years.

Two hundred seventy-nine primary total knee arthroplasties were performed with a modular, cemented, third-generation, posterior-stabilized prosthesis. At mean follow-up of 48 months (range, 24-72 months), the outcomes of 238 knees (85%) were evaluated with the Knee Society's Knee and Functional Scoring Systems and Roentgenographic Scoring System. The mean preoperative Knee Society Knee Score was 48 points compared with 96 points at latest follow-up. There were no cases of patellar clunk, symptomatic patellar maltracking, or posterior dislocation. There was no radiographic evidence of loosening or osteolysis, and no revisions were performed or recommended for loosening, osteolysis, instability, or polyethylene wear. Three patients developed late infections. These early results support the ongoing use of this design; however, long-term studies will be required.

The influence of femoral component design in the elimination of patellar clunk in posterior-stabilized total knee arthroplasty.

Patellar clunk occurs after posterior-stabilized total knee arthroplasty and is believed to be a design-related complication. This study was undertaken to define the incidence of patellar clunk with an optimized third-generation, posterior-stabilized prosthesis. One hundred ninety three patients with 238 knees were evaluated at a minimum of 2 years after primary total knee arthroplasty with a cemented, NexGen Legacy Posterior-Stabilized prosthesis (Zimmer, Warsaw, Ind). The mean follow-up was 48 months (range, 24-72 months). No patient manifested symptoms of patellar clunk or underwent surgery for any patello-femoral problem. These results support prior evidence that femoral component design is the primary cause of patellar clunk and that modifications incorporated into this third-generation, posterior-stabilized prosthesis has eliminated the problem.

Clinical results in valgus total knee arthroplasty with the "pie crust" technique of lateral soft tissue releases.

Numerous methods for creating symmetric flexion and extension gaps during knee arthroplasty in valgus knees have been proposed, and no consensus exists about the optimal technique. The "pie crust" technique for lateral soft tissue releases has been used extensively, yet few clinical results have been published. In this study, the clinical outcomes of 24 consecutive knees in 24 patients in whom this method was used in conjunction with a cemented posterior-stabilized prosthesis were evaluated. At a mean of 54 months' (range 24-69 months) follow-up, the knees were performing well with a mean Knee Society score of 97 (range 87-100) and mean range of motion of 121 degrees (range 100 degrees -145 degrees). Importantly, there were no clinical failures or cases of postoperative instability and no cases of radiographic loosening or wear.

Blood loss and transfusion rates in bilateral total knee arthroplasty.

From 1994 to 1998, we performed 170 bilateral total knee arthroplasties (TKAs) with cemented, posterior cruciate-substituting prostheses. Blood management included preoperative autologous donation, symptom-based transfusion, and autoreinfusion devices. Perioperative allogeneic transfusion rates for patients who donated 0, 1, 2, 3, or 4 units of blood were 40.00%, 0.00%, 3.70%, 0.00%, and 3.23%, respectively. Preoperative autologous donation >2 units also resulted in lower preoperative hemoglobin levels. For bilateral TKA, a protocol of 2 preoperative autologous donation units and reinfusion of postoperative drainage reduces anemia during the preoperative and postoperative periods.

Evaluation of the anterior cruciate ligament integrity and degenerative arthritic patterns in patients undergoing total knee arthroplasty.

We prospectively reviewed 107 consecutive primary total knee arthroplasties performed over a 1-year period. Intraoperatively, the integrity of the anterior cruciate ligament (ACL), the characteristics of the intercondylar notch, and the patterns of cartilage wear were evaluated. The ACL was found to be deficient in 41 knees (39%) at the time of surgery. The ACL-deficient knee had significantly narrower intercondylar notch widths compared with knees with an intact ACL (average, 9.75 vs 16 mm, P < .01). Furthermore, patients with ACL deficiency were found to have a higher percentage of Outerbridge grade IV changes at the lateral femoral condyle, lateral tibial plateau, and patellar surfaces when compared to the ACL-intact group. An intact ACL appeared to be protective against severe patellar degeneration. In conclusion, intercondylar notch narrowing from the arthritic process can lead to attrition and rupture of the ACL. An ACL deficiency appears to be associated increased wear of the lateral femorotibial and patellofemoral joints.

Factors affecting postoperative range of motion after total knee arthroplasty.

One hundred thirty five patients with osteoarthritis who underwent total knee arthroplasty (TKA) were evaluated to determine whether specific pre- and postoperative variables were correlated with the postoperative range of motion. Age, sex, pre- and postoperative range of motion, pre- and postoperative Knee Society scores, intraoperative patellar thickness before and after resurfacing, pre- and postoperative radiographic patellar height (as determined by the Insall-Salvati and Blackburn-Peel ratios), and preoperative radiographic alignment were recorded for each patient. Regression analysis was performed to identify whether any variables were correlated with the postoperative range of motion or Knee Society scores. The only variable that was significantly correlated with postoperative range of motion was the preoperative range of motion. This study suggests that among the variables evaluated, the preoperative range of motion was the only significant predictor of postoperative range of motion.

Optimizing patellofemoral tracking during total knee arthroplasty.

Fifty-seven patients who underwent 65 primary TKAs between 1993-1994 were retrospectively studied to identify the technical challenges and pitfalls associated with patellar resurfacing and to improve patellar tracking during total knee arthroplasty (TKA). Average patient age was 69 years. All surgeries were performed by a single surgeon (J.N.I), and the same prosthesis was used in all patients. Intraoperatively, attention was paid to avoid femoral and tibial component malrotation and prevent overstuffing of the patellofemoral joint. Preoperative limb alignment was varus in 42 knees, neutral in 6 knees, and valgus in 17 knees. Average pre-resection patellar thickness measured 23.8 mm and post-resection thickness averaged 21.5 mm. No patella-prosthesis composite was thicker than the native patella. Two (3%) knees required a formal lateral release to improve patellar tracking at surgery. Average follow-up for 53 patients (61 knees) was 5 years. At latest follow-up, 4 (6%) patients reported mild anterior knee pain, 5 (7%) patients reported pain with stairs, and 2 (3%) patients had knee crepitus without pain. No dislocations or recurrent subluxations occurred. No patient required revision surgery for patellofemoral complication. Awareness of the anatomic variability, attention to component rotation, and restoration of the normal patellar height improves patellar tracking and minimizes patellofemoral instability following TKA.

A quantitative histologic comparison: ACL degeneration in the osteoarthritic knee.

Newer prosthetic total knee arthroplasty (TKA) designs as well as unicondylar TKAs spare the anterior cruciate ligament (ACL). Although success of these procedures requires near normal ACL function, little has been written about the histologic features or the arthritic ACL. This study was designed to histologically evaluate the ACL for microscopic evidence of degeneration. Nineteen ACLs were harvested from 16 different patients who underwent TKA as a result of severe osteoarthritis. Control ligaments were obtained from bone bank donors (N = 14), patients with above-knee amputations (N = 5), and cadaveric formalin-preserved knees (N = 6). Orientation was maintained for each ACL. Degenerative parameters included loose, fibrous connective tissue and myxoid and cystic occurrences, and the presence of chondroid metaplasia or calcium phosphate crystals were evaluated and scored. Forty-seven percent of the osteoarthritic group had moderate/marked degeneration, whereas no control specimen showed such changes. Seventy-two percent of the controls were considered normal, compared with only 26% of the osteoarthritic group. Both of these findings were statistically significant (P<.001). Statistical analysis revealed no gender bias either within or between groups. In the control group, no statistical difference was found between patients older than age 65 and those younger than 65. In the osteoarthritic group, however, 70% of patients younger than 65 demonstrated moderate/marked changes compared with only 22% of those older than 65 (P<.05). There also was no difference demonstrated between the 4 focal sections of the ligaments that were examined.

The impact of femoral component rotational alignment on condylar lift-off.

The surgical technique and implant design influence femoral condylar lift-off in total knee arthroplasty. With the use of the classic method of bone resection and appropriate soft tissue releases, alignment of the femoral component along the transepicondylar axis will create a symmetric and balanced flexion space. This surgical technique will reduce the incidence of condylar lift-off. If condylar lift-off does occur, it may be beneficial to have a prosthesis that is designed with a conforming frontal articulation. Reducing lift-off with a relatively conforming articulation reduces edge loading and in turn should reduce polyethylene damage.

Correlation between condylar lift-off and femoral component alignment.

The current study analyzed subjects having a total knee arthroplasty to determine the incidence of condylar lift-off and correlate lift-off with the alignment of the femoral component with respect to the transepicondylar axis. Twenty-five subjects, implanted with a posterior stabilized total knee prosthesis, were asked to do weightbearing deep knee bends while under fluoroscopic surveillance. The two-dimensional fluoroscopic images were converted into three-dimensional images using a fully automated computer model-fitting technique. Each subject then was assessed for the incidence of condylar lift-off. The five subjects having the maximum amount of lift-off were reanalyzed for comparison using computed tomography. Using digitization, the angle between the posterior femoral condylar line and the transepicondylar axis was measured and correlated with the presence of femoral condylar lift-off. The incidence of condylar lift-off was significantly less for subjects in this study compared with subjects reported in previous fluoroscopic studies. Forty percent (10 of 25) of the subjects experienced condylar lift-off. The maximum amount of lift-off was 2.3 mm and the average for subjects experiencing lift-off was 1.4 mm. There also was a distinct correlation between femoral component alignment and condylar lift-off. Using computed tomography, it was determined that 69.2% of the subjects had a correlation between condylar lift-off and malalignment of the femoral component relative to the epicondylar axis. Placement of the femoral component parallel to the transepicondylar axis seems to lessen the incidence of femoral condylar lift-off and may reduce polyethylene wear by reducing eccentric edge loading.