Intramedullary Alignment System Research Articles

Computer-assisted versus intramedullary and extramedullary alignment system in total knee replacement: Long term follow-up

IntroductionThe aim of this work is to compare in a retrospective study, the radiological results of three series of different total knee replacements performed using Orthopilot computer-based alignment system (Group A, 31 patients), a totally intramedullary alignment system (Group B, 34 patients) and a totally extramedullary alignment system (Group C, 32 patients). Materials and methodsAt a medium follow-up of 15 years, all patients underwent call interview for clinical update. Of the 115 patients initially enrolled in the study, only 97 were available for radiological assessment. Both standing long-leg antero-posterior radiographs and lateral radiographs of the knee had been taken for every patient at 1 year-follow-up and at the last follow-up. ResultsAt the last follow-up, the mean hip-knee-ankle angle (HKA) was 179.1° (range: 176°–184°) for group A, 178.6° (range: 173°–186°) for group B and 177.8° (range: 172°–186°) for group C with no statistically significant difference among the 3 groups. The mean frontal femoral component angle (FFC) was 90.5° (range: 87°–94°) for group A, 91.05° (range: 85°–95°) for group B and 91.19° (range: 85°–96°) for group C and there was no statistically significant difference among the three groups. The mean frontal tibial component angle (FTC) was 89.9° (range: 83°–97°) for group A, 90.6° (range: 87°–95°) for group B and 90.8° (range: 86°–95°) for group C and there was no statistically significant difference among the three groups. The mean tibial component inclination in the sagittal plane was 1° (range: 3°–0°) for group A, 3.6° (range: 7°–0°) for group B and 3.1° (range: 6°–0°) for group C. Discussion and conclusionOur results demonstrated statistically significant differences between computer-assisted and extramedullary group, in favour of navigated group in terms of implant position and mechanical alignment. Computer-assisted group showed superior but not statistically significant differences compared to intramedullary alignment system in terms of implant position and mechanical alignment. We advocate the use of computer-assisted system routinely in total knee replacement. As an alternative, we suggest the use of intramedullary system.

The accuracy of intramedullary tibial guide of sagittal alignment of PCL-substituting total knee arthroplasty

Experimental and clinical studies on the accuracy of the intramedullary alignment method have produced different results, and few have addressed accuracy in the sagittal plane. Reported deviations are not only attributable to the alignment method but also to radiological errors. The purpose of this study was to evaluate the accuracy of the intramedullary alignment method in the sagittal plane using computed tomography (CT) and 3-dimensional imaging software. Thirty-one TKAs were performed using an intramedullary alignment method involving the insertion of a long 8-mm diameter rod into the medullary canal to the distal metaphysis of the tibia. All alignment instruments were set to achieve an ideal varus/valgus angle of 0° in the coronal plane and a tibial slope of 0° in the sagittal plane. The accuracy of the intramedullary alignment system was assessed by measuring the coronal tibial component angle and sagittal tibial slope angles, i.e., angles between the tibial anatomical axis and the tangent to the medial and lateral tibial plateau or the cut-surface. The mean coronal tibial component angle was 88.5°±1.2° and the mean tibial component slope in the sagittal plane was 1.6°±1.2° without anterior slope. Our intramedullary tibial alignment method, which involves passing an 8-mm diameter long rod through the tibial shaft isthmus, showed good accuracy (less than 3 degrees of variation and no anterior slope) in the sagittal plane in neutral or varus knees.

Tibial intramedullary canal axis and its influence on the intramedullary alignment system entry point in Koreans

Using computerized tomographic data and three dimensional model, we studied the influence of tibial intramedullary canal axis and other morphologic factors of the tibia on the entry point for tibial intramedullary alignment guides. Various anatomical parameters including tibial anteroposterior dimensions (AP), mediolateral dimensions (ML), aspect ratio (ML/AP), bowing and the intramedullary canal axis were studied. In addition, the entry point for the intramedullary alignment guide for primary and revision total knee arthroplasty were studied. The averaged entry point at the level of the tibial plateau was 5.7±2.2 mm anterior and 4.3±2.0 mm lateral to the classical entry point (P<.001). Furthermore, this entry point was more anterolateral in females when compared to males (P<.001). At a depth 10 mm below the tibial plateau, the entry point was on average 8.8±1.9 mm anterior and 2.9±1.9 mm lateral to the center of the cut surface. With increasing tibial varus the entry point tended to shift laterally at both levels (r=0.49) (P<.001). In Korean, the entry point for tibial intramedullary alignment systems is anterolateral to the classically described entry point. Moreover, the increment of tibial varus necessitates more lateral placement of the entry point. Intraoperatively, the entry point can be localized during primary knee arthroplasty to a point 15.9±2.8 mm anterior to and 1.2±2.8 mm lateral to the lateral tibial spine. For revision knee arthroplasty the point is on average 8.8±1.9 mm anterior and 2.9±1.9 mm lateral to the center of the cut surface of the tibia at a depth of 10 mm from the articular surface.

Coronal Bowing of the Femur and Tibia in Chinese: Its Incidence and Effects on Total Knee Arthroplasty Planning

To study the incidence of femoral or tibial bowing in the coronal plane in a Chinese population, and how it affects the accuracy of bone cuts for total knee replacement when an intramedullary alignment system is used. Standing radiographs of the entire lower limb of each patient with end-stage primary osteoarthritis of the knee were analysed. All radiographs were digitised and the extent of bowing in the coronal plane measured. A bowing was marked if an angulation was more than 2 degrees. The projected error of cutting was then calculated. Of 93 lower limbs, 58 (62%) of the femurs had marked bowing in the coronal plane; 41 (44%) had a mean lateral bowing of 5.3 (standard deviation [SD], 3.2) degrees; 17 (18%) had a mean medial bowing of 4.4 (SD, 1.9) degrees. Marked tibial bowing in the coronal plane was less common (30 tibias, 32%). If a cutting error of more than 2 degrees was considered unacceptable, significantly more unacceptable cuts would ensue in the groups with marked bowing (p=0.003 for femurs and p<0.001 for tibia, respectively). The incidence of femoral or tibial bowing in the coronal plane was high in a Chinese population with end-stage osteoarthritis of the knee. This phenomenon may increase bone cut errors in total knee replacement if an intramedullary alignment system is used and the extent of bowing is not recognised.

Laboratory Evaluation of Alignment and Kinematics in a Unicompartmental Knee Arthroplasty Inserted With Intramedullary Instrumentation

The purposes of this study were to evaluate the reliability of intramedullary (IM) instrumentation for unicompartmental total knee replacement and to assess the stability characteristics of the knee after implantation of a relatively unconstrained articular surface. Five adult, human cadaver lower extremities including hip, knee, and ankle were used to evaluate IM alignment. Five adult, fresh-frozen knee specimens were used to evaluate knee kinematics. Long anterioposterior roentgenograms were used to evaluate valgus angle and position of the center of the knee relative to the mechanical axis of the lower extremity. IM instrumentation returned the knee to normal alignment in all cases. The greatest valgus angle change was 3 degrees, and the position of the center of the knee relative to the mechanical axis was not significantly altered. Knee kinematics after unicompartmental knee replacement followed the predicted pattern of normal stability in extension and had slightly less varus-valgus laxity at 30 degrees (p less than 0.01), 45 degrees (p less than 0.01), and 60 degrees (p less than 0.05), and less anteroposterior displacement at 45 degrees (p less than 0.01) and 60 degrees (p less than 0.05). This study offers encouraging evidence that unicompartmental knee replacement with unconstrained components can restore normal knee kinematics, and that alignment can be restored with a high degree of accuracy with an intramedullary alignment system.

Fatal fat embolism following total condylar knee arthroplasty

Although fatality from fat emboli syndrome following total knee arthroplasty has been reported, most cases occurred following the insertion of hinged prostheses and few are documented with detailed pathology. The authors present the case of a 75-year-old patient with long-standing rheumatoid arthritis who underwent a total condylar type total knee arthroplasty procedure using an intramedullary femoral alignment system and expired 6 hours following surgery. On autopsy he had multiple organ involvement with fat emboli. Especially with the present use of intramedullary alignment systems and the increasing numbers of one-stage bilateral total knee arthroplasty procedures the potential for this problem must be recognized so that early therapy can be instituted.

人工膝関節置換術におけるＩｎｔｒａｍｅｄｕｌｌａｒｙ ｓｙｓｔｅｍとＥｘｔｒａｍｅｄｕｌｌａｒｙ ｓｙｓｔｅｍの比較検討

Proper bone resection is an essential step for performing total knee replacement arthroplasty. Many instrumentation systems have been developed to enable the surgeon to properly place and align the components. The purpose of this study was to determine whether an intramedullary (IM) or extramedullary (EM) alignment system is more accurate for performing proximal tibial resection.Twenty-three patients (29 knees) having Whiteside total knee arthroplasty with IM system and 28 patients (34 knees) having Miller/Galante total knee arthroplasty with EM system were examined in this study. The tibial cutting angle in the frontal and sagittal plane in the IM group was compared with those in the EM group according to postoperative roentgenograms.In the frontal plane, although the mean cutting angle between both groups was not statistically significant, the IM group proved more accurate than the EM group. In the sagittal plane, the mean cutting angle between both groups was statistically significant at the 0.01 level and here also the IM group was more accurate.The results observed in this study would suggested that the IM alignment system is more appropriate for performing proximal tibial resection.

A Comparative Study of Extramedullary and Intramedullary Alignment Systems in Total Knee Arthroplasty

A prospective study was performed to compare the alignment after total knee arthroplasty (TKA) using two different alignment systems: an intramedullary system versus an extramedullary system. These two systems were alternately used to make the distal femoral resection in 50 patients. There was little difference between the two systems in achieving appropriate valgus of the distal femoral cut and a correct angle of tibiofemoral valgus.