Fluoroscopic and Computed Tomographic Analysis of Knee Kinematics During Very Deep Flexion After Total Knee Arthroplasty

We examined the relative motion of femoral and tibial total knee arthroplasty components and the difference between 2 different tibial inserts (9 flat types and 7 dish types) in patients sitting in very deep flexion. X-ray, fluoroscopic examination, and computed tomography were used to analyze liftoff, and rotation. During seiza-style sitting, one knee (11%) with the flat insert lifted off on the medial side and 5 knees (71%) with the dish-type insert showed liftoff. The tibial internal rotation angles were 17.2° ± 4.1° (flat type) and 11.7° ± 3.1° (dish type) (P < .05). The flat type showed less liftoff at the medial side and more internal rotation. For very deep flexion, components that tolerate larger rotational freedom are favorable.     

Effect of Balanced Gap Total Knee Arthroplasty on Intraoperative Laxities and Femoral Component Rotation

The gap technique could lead to undesirable rotation of the femoral component in some knees. Using a navigation system, femoral component external rotations and varus-valgus laxities at 0° and 90° of flexion were measured intraoperatively in 44 patients. Significant improvements were observed at a minimum follow-up of 4 years with regard to clinical and radiologic outcomes. The balanced gap technique in total knee arthroplasty provided good intraoperative alignments and laxities of knees at 0° and 90°. However, increased femoral component external rotation was found to be correlated with increased varus alignment at 90° of knee flexion. This study shows that excessive external rotation of the femoral component during flexion gap balancing using the balanced gap technique in total knee arthroplasty can be avoided by additional soft tissue balancing guided by navigation.     

Intramedullary vs extramedullary femoral alignment guides: a 15-year follow-up of survivorship

The influence of intramedullary (IM) and extramedullary (EM) femoral cutting guides on survivorship of total knee arthroplasty was studied in 6726 total knee arthroplasty guided by either an IM (4993 knees) or EM (1733 knees) system. Fifteen-year survivorship of the 2 cohorts showed no statistically significant difference (EM 97.9% vs IM 98.5%; P = .2500, log rank). Medial bone collapse comprised the highest proportion of all failure modes for both groups (0.35% vs 0.40%, respectively, P = .6731, Cox regression). Mean tibiofemoral (overall) anatomical alignment was statistically more accurate in the IM group (IM 4.6° [±2.2°] valgus vs EM 5.1° [±3.1°] valgus; P < .0001). The mean tibial alignment was 90.5° (±3.0) and 90.3° (±2.2) (P = .0077). The EM group had a significantly larger tibial component alignment variance (SD²) than the IM group. No statistical difference in postoperative Knee Society scores, pain, or stair-climbing abilities was found. The choice of either alignment system should be determined by the patient's anatomy; however, the overall alignment is not as precise using the extramedullary system.     

Bone anatomy and rotational alignment in total knee arthroplasty

The purpose of the current study was to investigate the bone anatomy in determining the rotational alignment in total knee arthroplasty using computed tomography. Axial images of 109 knees in 83 patients with varus osteoarthritis who had total knee arthroplasty were analyzed. On the images of the distal femur and the proximal tibia, a baseline for the anteroposterior axis of each component was drawn based on the epicondylar axis for the femur and the medial (1/3) of the tibial tuberosity for the tibia. The angle between these two lines was analyzed as the rotational mismatch between the components when they were aligned to the anatomic landmarks of each bone. Fifty-four knees (49.5%) had an angle of 5 degrees or greater and 13 knees (11.9%) had an angle of 10 degrees or greater. There was a tendency to align the tibial component in external rotation relative to the femoral component. The results indicated that the landmarks of each bone were the intrinsic cause of the rotational mismatch in knees with varus osteoarthritis. Surgeons doing total knee arthroplasties should be aware of this and check the rotational mismatch between the components. When it is present, the tibial component should be realigned to match the femoral component rotation to minimize problems caused by the mismatch.     

老年性骨关节炎行人工膝关节置换术后 假体旋转对线的定量分析

目的根据不同解剖标志利用CT扫描定量测量人工膝关节置换术后股骨和胫骨假体的旋转对线。方法 2004年对21位合并膝内翻畸形(35个膝)老年性骨关节炎患者(平均年龄73.3岁,范围:60～81岁)行人工膝关节置换手术,术中采用后稳定型固定平台膝关节假体,以股骨后髁轴外旋截骨确定股骨假体旋转定位,综合参考胫骨平台最大覆盖率和胫骨后髁轴确定胫骨假体旋转定位。术后7年进行随访,内容包括病史采集、物理检查,KSS评分和功能评分,负重位膝关节正侧位X光片、髌骨轴位片以及膝关节CT扫描。在CT扫描图像上,根据股骨内外上髁轴(SEA)测量股骨假体旋转角度,分别根据股骨内外上髁轴和胫骨结节内侧1/3测量胫骨假体旋转角度,并以此测算假体的联合旋转角度和旋转不匹配程度。结果对35个膝关节随访7年结果显示,未出现感染、假体透亮带、髌骨脱位或半脱位、髌骨骨折、假体松动等,KSS临床评分平均91分,功能评分平均83分。股骨假体、胫骨假体旋转角度、联合假体旋转角度均呈正态分布;股骨假体平均旋转角度为(3.02±3.88)°;胫骨假体相对于胫骨结节内侧1/3明显处于内旋位(平均17°),相对于SEA旋转角度平均0°,参考两个标志测量的胫骨假体旋转角度之间有显著差异(P=0.000);相对于SEA确定的假体联合旋转角度平均(2.99±7.90)°,相对于胫骨结节内侧1/3确定的假体联合旋转角度平均(-2.64±8.39)°,参考两个参考标志测定假体联合旋转角度之间有显著差异(P=0.005),股骨和胫骨假体旋转不匹配最大程度在10°度左右。结论与胫骨结节内侧1/3做比较,股骨内外上髁轴(SEA)更适合作为CT定量测量人工膝关节置换术后股骨和胫骨假体旋转对线的标志;胫骨平台最大覆盖率和胫骨后髁轴可以作为胫骨假体旋转定位的参考轴线,但具有较大的个体差异性。     

Change in tibiofemoral rotational alignment during total knee arthroplasty

Background

Rotational mismatch between femoral and tibial components has been recognized as a risk factor of unsuccessful total knee arthroplasty (TKA), but a main cause of rotational mismatch is uncertain. This study aims to evaluate rotational alignment of the knee by measuring both component rotation and version of the knee in TKA.

Method

Fifty-one TKAs (mean age 73.7 years) were included in this study. The three dimensional, weight-bearing knee alignment was measured before and after TKA. A transepicondylar axis was referenced to femoral component rotation, and an anteroposterior axis of the tibia (middle of posterior cruciate ligament attachment to medial border of patella tendon attachment) was referenced to tibial component rotation. Knee rotational angle was defined as the angle between these two axes.

Result

The mean preoperative knee rotation angle of 9.7° (±8.5°) internal rotation was significantly reduced to 1.8° (±7.3°) external rotation after TKA. Twenty-one of 51 knees (41 %) exhibited rotational mismatch (>10°) preoperatively, and this number was reduced to eight knees (16 %) post-TKA. The femoral component was rotationally aligned within 5° of neutral in all knees, while rotational alignment of the tibial component showed a high degree of variability (range 20.7° internal rotation to 17.2° external rotation).

Conclusion

Rotational malposition of the tibial component was considered to be a main factor of rotational mismatch of the knee after TKA.     

A simple guide for rotational alignment of the tibial component in knee arthroplasty

A guide system was designed for use in conjunction with knee arthroplasty instruments. A pin is guided into the upper tibial cortex parallel to the sagittal axis of the femoral component with the patella in its normal position and the knee at 20° of flexion. The holes and/or slots for the tibial component using the appropriate drill guide can now be made, with the patella displaced totally for exposure of the cut tibial surface, to allow correct rotational alignment of the prosthesis in the tibia.     

A simple guide for rotational alignment of the tibial component in knee arthroplasty

A guide system was designed for use in conjunction with knee arthroplasty instruments. A pin is guided into the upper tibial cortex parallel to the sagittal axis of the femoral component with the patella in its normal position and the knee at 20 degrees of flexion. The holes and/or slots for the tibial component using the appropriate drill guide can now be made, with the patella displaced totally for exposure of the cut tibial surface, to allow correct rotational alignment of the prosthesis in the tibia.     

Femoral Rotation in Ligament Balanced Knee Arthroplasty : A Prospective Clinical Study

Rotational alignment of the femoral component is an important factor to achieve beneficial results in total knee arthroplasty. Femoral rotation pre versus post surgery was prospectively assessed in 40 patients who underwent ligament balanced knee arthroplasty. Computerized tomography of the knee was performed before and after the surgery to determine the femoral rotation. In 36 out of 40 patients the rotation of the femoral implants differed compared to the preoperative femur (P > 0.001). After surgery the rotational alignment of the femoral component ranged from − 3° (internal rotation) to 7° (external rotation). Increased external rotation was found in 33 out of 40 patients ranging from 1° to 7°. These results highlight the importance of individually determined femoral rotation in ligament balanced knee arthroplasty.     

Medial torsion of the tibia in Japanese patients with osteoarthritis of the knee

To assess the reliability of the landmarks for the rotationally neutral alignment of the tibial component in total knee arthroplasty for Japanese patients, the rotational position of the medial (1/3) of the tibial tuberosity relative to the femoral epicondylar line (Angle TT) and that relative to the center of the ankle (Angle TT-AA) were measured in 24 knees with medial femorotibial osteoarthritis and in 28 normal knees by computed tomography. Angle TT-AA shows the degree of medial torsion of the tibia. The range of Angle TT and that of Angle TT-AA each was greater than 40 degrees. The position of the tibial tuberosity and degree of medial torsion of the tibia varied by individual. In patients with severe medial torsion, the internal rotation of the foot is extreme if the medial (1/3) of the tibial tuberosity is used for the rotationally neutral alignment of the partially constrained tibial component. In the treatment specifically of patients from East Asian countries, medial torsion of the tibia should be taken into account in total knee arthroplasty to ensure proper patellar tracking and proper rotation of the foot in knees with medial femorotibial osteoarthritis.     

Varus tibial joint line obliquity: a potential cause of femoral component malrotation.

In 60 consecutive total knee arthroplasties done in 52 patients with primary osteoarthritis and varus or neutral tibiofemoral alignment, the posterior condylar angle was calculated intraoperatively and averaged 3.98 degrees (range, 0 degrees-9 degrees). Eighteen knees had a posterior condylar angle value less than 3 degrees whereas 27 knees had a posterior condylar angle value of 5 degrees or greater. Final rotational alignment of the femoral component was set parallel to the transepicondylar axis. Only one of these 60 knees required a lateral retinacular release for proper patellar tracking during the knee arthroplasty. When compared with three previously defined angles measured on the radiographs taken preoperatively, only the tibial plateau-tibial shaft angle values were correlated significantly with the value of the posterior condylar angle. As the tibial varus joint line obliquity increased, there was a distinct tendency for the transepicondylar axis to be rotated more externally relative to the posterior condylar axis. This variance suggests that the use of the posterior condylar axis as a rotational reference is inappropriate in many knees with arthritis with varus or neutral tibiofemoral alignment. In particular, varus tibial joint line obliquity of more than 4 degrees increases the likelihood of femoral component malrotation when the posterior femoral condyles are used to reference femoral component rotation.     

Central Implantation of the Femoral Component Relative to the Tibial Insert Improves Clinical Outcomes in Fixed-Bearing Unicompartmental Knee Arthroplasty

BackgroundThe direct relationship between clinical outcomes and femoral component positioning relative to a tibial insert remains unknown. We determined whether the femoral component position relative to the tibial insert could affect clinical outcomes after fixed-bearing unicompartmental knee arthroplasty (UKA).MethodsThe femoral component position relative to the tibial insert of 66 patients with anteromedial osteoarthritis and osteonecrosis of the knee who underwent fixed-bearing UKA was assessed at 2 weeks postoperatively. We classified patients according to the contact point of the femoral component with the tibial component: group M (medial), 18 knees; group C (central), 30 knees; and group L (lateral), 18 knees. Patient-derived clinical scores using the 2011 Knee Society Score were also assessed preoperatively and at 2 years postoperatively and compared among the 3 groups using the analysis of variance.ResultsThe average 2-year postoperative “symptom” and “patient satisfaction” scores based on the 2011 Knee Society Score were significantly higher in group C than in group M or group L.ConclusionCentral implantation of the femoral component relative to the tibial insert plays an important role in decreasing pain and could result in better patient satisfaction after fixed-bearing UKA at 2 years postoperatively. Surgeons should set the femoral component at the center relative to the tibial insert for better patient satisfaction and higher active knee flexion after fixed-bearing UKA.     

Internal Rotation of Femoral Component Affects Functional Activities After TKA—Survey With The 2011 Knee Society Score

The 2011 Knee Society Knee Scoring System (KSS) was developed as a new patient-derived outcome measure to better characterize satisfaction, expectations, and physical activities after total knee arthroplasty. The rotational alignment of the femoral and tibial components was assessed with computed tomography in 75 patients (92 knees), and its effect on the scores of the KSS was evaluated. Internal rotation of the femoral component relative to the surgical epicondylar axis significantly decreased the score of functional activities and slightly decreased the score of satisfaction. Femoral component malrotation did not affect the scores of symptoms and expectations. Tibial component malrotation did not affect any of the scores of the 2011 KSS. Surgeons should avoid internal rotation of the femoral component to preserve functional activities.     

三维骨建模系统在人工全膝关节置换时旋转对位的作用

目的 为了进行人工全膝关节置换时假体旋转对位的量化研究,探讨三维骨建模的计算机辅助手术系统对量化操作的精确性和有效性. 方法 2002年11月 - 2003年6月,采用三维骨建模 Ceravision 系统对 21 例 21 膝保守治疗无效的三间隔骨性关节炎患者行人工全膝关节置换术.男5例5膝,女16例16膝;年龄64～79岁,平均 72.4 岁.左膝10例,右膝11例.主要临床表现为膝关节疼痛和活动受限.病程2～10年.14例膝内翻,7例膝外翻.根据相关的临床体检、影像学和导航系统资料,对术中假体旋转对位量值,并对术后3个月膝关节活动度、膝关节松弛度和髌骨稳定性进行分析. 结果 全部患者术后切口均Ⅰ期愈合.21 例患者均获随访12～16个月,平均13.3个月.术中股骨假体旋转对位内旋 1°～外旋 5°,胫骨假体旋转对位内旋 0°～外旋5°.其中膝内翻患者,股骨假体旋转对位外旋 1°～外旋5°,胫骨假体旋转对位外旋2°～外旋5°膝外翻患者,股骨假体旋转对位内旋1°～外旋4°,胫骨假体旋转对位内旋0°～外旋 4°.术后3个月膝关节活动度,最大屈膝度为 105～130°,平均 115°;膝关节额面松弛度,内侧 0.2～0.5 cm,平均 0.27 cm,外侧 1.0～2.5 cm,平均 1.7 cm.无膝痛、髌骨失稳和脱位等并发症发生. 结论 应用三维骨建模的计算机辅助手术系统,可针对患者个体精确地进行假体旋转对位.     

Is the Anterior Tibial Tuberosity a Reliable Rotational Landmark for the Tibial Component in Total Knee Arthroplasy?

To analyze the morphology of the tibial plateau, we studied 100 computed tomographic scans of arthritic knees and measured the mediolateral (ML) and anteroposterior (AP) dimensions as well as their aspect ratio using 3 reference axes of rotation: transepicondylar axis (TEA), posterior tibial margin (PTM), and anterior tibial tuberosity (ATT) axis. Relative to the TEA, the PTM was internally rotated by 1.6° ± 5.1°, and the ATT externally rotated by 14.8° ± 7.2°. The AP and ML dimensions and aspect ratio differ significantly when the reference axis was ATT compared with PTM or TEA and variations were greater while using ATT axis. Our data demonstrate (1) that design of the tibial component restricts the choice of rotational alignment and (2) that ATT is not a reliable landmark for rotation of the tibial component.     

Component rotation and anterior knee pain after total knee arthroplasty.

All patients undergoing cruciate-retaining primary total knee arthroplasty for degenerative osteoarthritis at one center were studied prospectively. Clinical and radiographic followup was obtained at a minimum 5 years in 102 knees in 73 patients. Patients were asked specifically about the presence of the pain in the anterior aspect of the knee in the vicinity of the patella and rated the severity of the pain on a visual analog scale. Significant anterior knee pain rating at least 3 of 10 on the visual analog scale was present in 16 knees (13 patients). Eleven patients with 14 symptomatic knees agreed to undergo computed tomography scanning to accurately determine the rotation of the tibial and femoral components. The epicondylar axis and tibial tubercle were used as references using a previously validated technique. A control group of 11 asymptomatic patients (14 knees), matched for age, gender, and length of followup also underwent computed tomography scanning. All patients in both groups had normal axial alignment. There was a highly significant difference in tibial component rotation between the two groups with the patients with anterior knee pain averaging 6.2 degrees internal rotation compared with 0.4 degrees external rotation in the control group. There also was a significant difference in combined component rotation with the patients with anterior knee pain averaging 4.7 degrees internal rotation compared with 2.6 degrees external rotation in the control group. There was no significant difference in the degree of radiographic patellar tilt or patellar subluxation between the two groups. Patients with combined component internal rotation were more than five times as likely to experience anterior knee pain after total knee arthroplasty compared with those with combined component external rotation. Component malrotation is a significant factor in the development of anterior knee pain after total knee arthroplasty.     

Preoperative Templating and Computer-Assisted Total Knee Arthroplasty for Arthritic Valgus Knee

We reported the functional outcomes, component alignment and optimal thickness of the tibial inserts and joint line changes of 21 arthritic valgus knee deformities using preoperative templating and computer-assisted total knee arthroplasty(TKA). The osseous cut was modified using a novel preoperative templating technique. Soft tissue balance and component implantation were implemented with the aid of a computed tomography-free navigation system. The arthritic valgus knees had clinical, and functional improvement of the knee Society scores and Lysholm scores postoperatively, at an average of 37.8 ± 7.2 months. The mean anatomic axis (15.2° ± 4.5° vs. 6.1° ± 1.4°) and mechanical axis (8.3° ± 5.2° vs. 0.28° ± 1.6°) were also significantly improved postoperatively. The mean thickness of tibial inserts and joint line changes was 10.7 ± 1.46 mm and 0.1 ± 1.4 mm. This computer-assisted technique with preoperative radiographic templating is an alternative strategy to improve TKA results in arthritic valgus knees.     

Accelerometer-Based,Portable Navigation vs Imageless,Large-Console Computer-Assisted Navigation in Total Knee Arthroplasty : A Comparison of Radiographic Results

Computer-assisted surgery (CAS) systems improve alignment accuracy in total knee arthroplasty (TKA) but have not been widely implemented. Eighty knees underwent TKA using an accelerometer-based, portable navigation device (KneeAlign 2; OrthAlign Inc, Aliso Viejo, California), and the radiographic results were compared with 80 knees performed using a large-console, imageless CAS system (AchieveCAS; Smith and Nephew, Memphis, Tennessee). In the KneeAlign 2 cohort, 92.5% of patients had an alignment within 3° of a neutral mechanical axis (vs 86.3% with AchieveCAS, P < .01), 96.2% had a tibial component alignment within 2° of perpendicular to tibial mechanical axis (vs 97.5% with AchieveCAS, P = .8), and 94.9% had a femoral component alignment within 2° of perpendicular to the femoral mechanical axis (vs 92.5% with AchieveCAS, P < .01). The mean tourniquet time in the KneeAlign 2 cohort was 48.1 ± 10.2 minutes vs 54.1 ± 10.5 minutes in the AchieveCAS cohort (P < .01). Accelerometer-based, portable navigation is as accurate as large-console, imageless CAS systems in TKA.     

Femoral Anterior Tangent Line of the Osteoarthritic Knee for Determining Rotational Alignment of the Femoral Component in Total Knee Arthroplasty

Several reference axes have been used to establish femoral rotational alignment during total knee arthroplasty. The current study examined the configuration of the anterior surface of the femur immediately proximal to the trochlea as an alternative rotational landmark. An analysis of computed tomographic images of 150 knees with osteoarthritis indicated that the configuration of the surface is mostly flat or slightly depressed, and the line tangential to the surface (femoral anterior tangent line; FAT line) was consistently determined to be 12.2° ± 3.6° internally rotated to the transepicondylar axis. This value was relatively constant and as reliable as the femoral anteroposterior axis for determining rotational alignment. In addition, the FAT line was not affected by the degree of the varus-valgus deformity of the osteoarthritic knees.     

Effect of rotational malposition of the femoral component on knee stability kinematics after total knee arthroplasty

Excessive external rotation of the femoral component can cause an abnormally tight popliteus tendon complex, which induces loss of rotational laxity of the knee in the late phase of knee flexion after total knee arthroplasty. This study evaluated the effect of popliteus tendon release on rotational and varus—valgus laxity of implanted knees with an excessively externally rotated femoral component. Rotational and varus—valgus laxity was measured with a knee kinematics testing device before and after total knee arthroplasty. External rotational positions of the femoral component of 5° and 8° were compared, and the effects of popliteus tendon release on rotational and varus—valgus laxity were evaluated. To further investigate this question, the effect of a conforming articular design was compared with that of a flat tibial surface. External rotational position of 5° did not change rotational or varus—valgus laxity of the knee. With an 8° external rotational position, however, external rotational laxity significantly decreased in knees with a conforming surface at angles of 30°, 45°, 60°, and 90°. After popliteus tendon release, external rotational laxity significantly improved at 90° flexion and was identical to that of the normal knee. Internal rotational range was similar before and after popliteus tendon release. Popliteus tendon release did not affect the varus—valgus laxity (stability) with either articular surface.