CT measurements prior to computer-assisted total knee arthroplasty do not improve rotational placement of the femoral component

Purpose

The aim of this study is to determine whether computer-assisted surgery (CAS) can gain more precision by utilizing information from pre-operative computed tomography (CT).

Methods

Sixty-five patients undergoing total knee arthroplasty in 2008 were included. On pre- and post-operative CT, epicondylar and posterior condylar lines were drawn and the posterior condylar angle between these two lines measured. During the surgery, epicondylar and posterior condylar lines were also registered before and after CAS-guided cuts were made. CAS was used to fix the orientation of the cutting guide on the distal femur at 3° of external rotation from the posterior condylar line.

Results

There was no correlation between CT measurements and CAS measurements. All orientations of the lines (relative to the horizontal) and angles measured using CT were significantly different (p?<?0.05).

Conclusion

No relationship was found between pre-operative CT measurements and peri-operative CAS measurements used to orient the femoral component. Data obtained from CT cannot be used peri-operatively with CAS to improve rotational setting of the femoral component.

Level of evidence

Therapeutic study, Level II.     

Native rotational knee kinematics are lost in bicruciate-retaining total knee arthroplasty when the tibial component is replaced

Purpose

To compare the kinematics between native knees and knees that have undergone bicruciate-retaining (BCR) total knee arthroplasty (TKA) with cruciate-retaining (CR) TKA converted from BCR TKA in the same whole-body cadaveric specimen using a navigation system and, if differences exist, to investigate the point at which normal kinematics are lost during the procedure.

Methods

The rotational kinematics throughout passive flexion of the native knee and of knees after meniscectomy, femoral replacement, BCR TKA, or CR TKA were assessed in nine fresh frozen cadavers using an image-free navigation system.

Results

The rotational kinematic pattern of a knee after BCR TKA was different from that of a native knee, especially in the early flexion phase, and was similar to that after CR TKA. Screw-home movement was not observed after BCR TKA, but still occurred after meniscectomy or femoral replacement with intact cruciate ligaments and an intact tibial articular surface.

Conclusion

The rotational kinematics of the native knee are not always preserved after BCR TKA. Native rotational kinematics are preserved after meniscectomy and femoral replacement, but are lost after tibial replacement in BCR TKA. Surgeons should pay close attention to maintain the anteroposterior stabilizing function of the ACL in BCR TKA, rather than to restore the native rotational kinematics.

     

Accuracy of anatomical references used for rotational alignment of tibial component in total knee arthroplasty

Purpose  

This study aimed to research which was the most reliable of the four techniques based on local anatomic markers used to determine tibial component rotation in total knee arthroplasty, and whether the markers varied in knees with varus deformity.     

The anterior trochlear line as a reference for femoral component positioning in total knee arthroplasty

Purpose  

A new radiographic method using the anterior and posterior femoral condyles as a landmark to determine the rotational alignment of the femoral component in TKA had been developed.     

Variability of the location of the tibial tubercle affects the rotational alignment of the tibial component in kinematically aligned total knee arthroplasty

Purpose

Our experience with computer plans of kinematically aligned total knee arthroplasty showed that the anteroposterior (AP) axis of the tibial component when viewed in an axial plane did not consistently intersect either the medial border or the medial 1/3 of the tibial tubercle. The purposes were (1) to determine the variability in the mediolateral location of the tibial tubercle with respect to the medial tibia on the magnetic resonance image (MRI) of the knee and (2) to determine whether the AP axis of the kinematically aligned tibial component intersects either the medial border or the medial 1/3 of the tibial tubercle.

Methods

One hundred and fifteen knees in 111 consecutive subjects treated with total knee arthroplasty were studied. The mediolateral location of the tibial tubercle was measured from a magnetic resonance image (MRI) of the knee. The distances between the AP axis of the tibial component and the medial border of the tibial tubercle and between the AP axis and the medial 1/3 of the tibial tubercle were measured from a computer plan of the reconstructed knee.

Results

On the MRI, the medial border of the tibial tubercle varied 15 mm from the medial border of the tibia. On the computer plan, the AP axis of the tibial component in an axial view of the tibia did not intersect either the medial border (p < 0.0001) or the medial 1/3 of the tibial tubercle (p < 0.0001). In 70 and 86 % of knees, the mediolateral distance of the AP axis of the tibial component was 2 mm or greater from the medial border of the tibial tubercle and the medial 1/3 of the tibial tubercle, respectively, which causes a clinically meaningful error in rotation of 5° or more.

Conclusions

Because the mediolateral location of the tibial tubercle varies, the medial border and medial 1/3 of the tibial tubercle are not reliable landmarks when the goal is to kinematically align the rotation of the tibial component on the tibia.

Level of evidence

IV.     

Computer-assisted revision of total knee arthroplasty

Revision total knee prosthesis still remains a difficult procedure. Particularly, challenging is the restoration of the joint line to a normal position and the attainment of correct lower limb alignment and healthy bone support for the implants. Computer assistance improves accuracy during the implantation of primary total knees. The goal of this study was to evaluate the usefulness of computer assisted surgery (CAS) in total knee prosthesis revision. We revised 15 NKII total knee arthroplasties with the Navitrack system and compared the mechanical alignment and the joint line level on pre- and postoperative radiographs. After revision, the joint line position was restored. The knee with the revision prosthesis was aligned in the frontal plan with implants fixed perpendicularly to the mechanical axis. It is possible to correctly revise knee prosthesis with computer assistance only and without having to use a conventional ancillary. We had a permanent control of the joint line position and have performed the revision surgery following the same steps as in a primary implantation.     

全膝置换术中股骨假体旋转参照轴的影像学比较研究

目的比较全膝置换术中确定股骨假体旋转对线的参照方法———股骨上髁轴与Whiteside′s线的准确性,旨在为国人的人工膝关节手术技术提供实验依据,以减少术后髌股关节并发症的发生率。方法选择80例正常人(年龄19～42岁,男女各半)的膝关节作为研究对象,应用螺旋CT扫描(层厚0.5mm)获取股骨远端精确的横断面图像,通过测量比较股骨上髁轴、Whiteside′s线与股骨后髁轴之间的关系,运用统计学方法分析其准确性。结果股骨上髁轴与股骨后髁轴的夹角(股骨后髁角)为男性6.7°±1.5°,女性6.4°±1.8°,Whiteside′s线与股骨后髁轴的夹角为男性7.2°±3.1°,女性7.8°±3.2°。性别之间无显著性差异(P>0.05)。结论股骨上髁轴作为股骨假体旋转对线的参照较为恒定可靠,而Whiteside′s线的变异度较大、重复性较差。国人的股骨后髁角比西方人大,术中如以股骨后髁轴外旋3°来放置股骨假体,容易出现假体内旋。     

Computer-assisted surgery can reduce blood loss after total knee arthroplasty

The aim of this study was to compare blood loss and transfusion requirements in patients undergoing computer-assisted total knee arthroplasty (TKA) and patients operated with conventional instrumentation with intra-medullar guides. A prospective randomized study of 87 patients undergoing a TKA assigned to conventional technique (n = 44) or computer-assisted surgery (n = 43) was conducted. All patients were operated by the same surgeon and in all cases a cemented arthroplasty and deep recovery drainage were used. Both groups were comparable in all variables except for duration of ischemia, which was 13.7 min higher in the computer-assisted group. Blood loss due to drainage was higher in the conventional technique group (613 vs. 447 ml), as was the number of patients in which blood from the blood recovery system was reinfused (53 vs. 23%). Those patients undergoing computer-assisted surgery experienced less bleeding than those operated with the conventional technique. However, hemoglobin drop and allogenic transfusion rate were not statistically different in both groups.     

Evaluation of tibial rotational alignment in total knee arthroplasty: a cadaver study

Various techniques exist for establishing tibial rotational alignment during total knee arthroplasty (TKA). The purpose of this study is to establish the most precise and reproducible method to assess tibial component rotational alignment during TKA by comparing the flexion-extension technique (ROM) and the Posterior-lateral Corner Locked Technique (PLCL). Twenty posterior stabilized TKAs were performed on cadavers. The rotation angles of the tibial components obtained using the two techniques were evaluated. The tibial component rotation axis obtained using the ROM technique and the PLCL method averaged, respectively, 0.35° (±4.2°) externally rotated and 0.34° (±3°) internally rotated to the Akagi line. No significant differences between the two methods were found and a high correlation exists between the two techniques (Pearson’s coefficient = 0.88). The ROM and PLCL techniques are both precise and reproducible methods to assess tibial component rotation during TKA. However, while the ROM technique is dependent on the correct positioning of the femoral component and the soft tissue balancing, the PCLC method is easier if a complete visualization of the posterior-lateral corner of the cut tibial plateau is achieved.     

The medial border of the tibial tuberosity as an auxiliary tool for tibial component rotational alignment during total knee arthroplasty (TKA)

Purpose

The objective of this study was to quantify the amount of ensuing internal rotation of the tibial component when positioned along the medial border of the tibial tubercle, thus establishing a reproducible intraoperative reference for tibial component rotational alignment during total knee arthroplasty (TKA).

Methods

The angle formed from the tibial geometric centre to the intersection of both lines from the middle of the tibial tuberosity and its medial border was measured in 50 patients. The geometric centre was determined on an axial CT slice at 10 mm below the lateral tibial plateau and transposed to a slice at the level of the most prominent part of the tibial tuberosity. Similar measurements were taken in 25 patients after TKA, in order to simulate the intraoperative appearance of the tibia after making its proximal resection.

Results

This angle was found to be similar (n.s.) in normal and post-TKA tibiae [median 20.4° (range 15°–24°) vs. 20.7° (range 16°–25°), respectively]. In 89.3 % of the patients, the angle ranged from 17° to 24°. No statistical difference (p n.s.) was found between women and men in both normal [median ?20.7° (range 16°–25°) vs. 19.9° (range 15°–24°)] and post-TKA tibiae [median 21.4° (range 19°–24°) vs. 20° (range 16°–25°)].

Conclusion

This study found that in 90 % of the patients, the medial border of the tibial tuberosity is internally rotated 17°–24° in relation to the line connecting the middle of the tuberosity to the tibial geometric centre. Since this anatomical landmark may be more easily identifiable intraoperatively than the commonly used “medial 1/3”, it can provide a better quantitative reference point and help surgeons achieve a more accurate tibial implant rotational position.

Level of evidence

Cohort and case control studies, Level III.

     

Early revision for isolated internal malrotation of the femoral component in total knee arthroplasty

Purpose

In this prospective study, we determined whether corrective surgery for isolated rotational malalignment of femoral prosthesis components would benefit patients previously treated with total knee arthroplasty. The symptoms, amount of malrotation and type of constraint necessary for the revision prosthesis were investigated.

Methods

Seventy-two patients were screened with computed tomography; of these, 14 had isolated internal malrotation of the femoral component with no other malpositions and were included in the study. A complete exchange arthroplasty with the correction of the malrotated femoral component was performed within 3?years of primary arthroplasty. Mean follow-up was 57?months.

Results

At the time of revision, patients suffered either from instability in flexion with good range of motion (ROM) (flexion ≥90°) and pain on the lateral side of the distal femur and proximal tibia (n?=?8) or from stiffness with pain on the medial side of the proximal tibial and poor ROM (flexion <90°) (n?=?6). One patient showed no patellar maltracking, six patients, patellar tilt and six patients, patellar subluxation. Median internal rotation of the femoral component was 7.1° (4.1–10.0°). A condylar-type revision implant with a posterior-stabilized insert was used in all patients. The corrective surgery resulted in an increase in the mean Knee Society Score from 52/65 to 85/84 points and an improvement in the mean Hospital for Special Surgery knee score from 63 to 83 points.

Conclusions

Correction of isolated internal malrotation of the femoral component ≥4° improves patient outcome.     

How to assess femoral and tibial component rotation after total knee arthroplasty with computed tomography: a systematic review

Purpose

One of the most important factors leading to revision of total knee arthroplasties (TKA) is malrotation of femoral and/or tibial component. Rotation measurements performed on radiographs are limited and less reliable compared to 2D computed tomography (CT). Nowadays, 2D-CT and 3D-CT can be distinguished in measuring rotation of the TKA components. The aim of this systematic review is to determine the most reliable CT techniques in measuring rotation of the TKA components and to investigate possible cut-off points that can be used in the clinician’s decision for a possible revision of the TKA.

Methods

A search of PubMed, Embase, the Cochrane Central Register of Controlled Trials and Web of Science was performed up to April 2015. Final selections of 12 articles were used in this systematic review.

Results

3D-CT, compared to 2D-CT, is more reliable and shows a high level of intra- and interobserver reliability. Femoral component rotation is measured using the component’s posterior condylar line or inner pegs in relation to the epicondylar axis. Five different techniques were used to measure tibial component rotation. The posterior border of the tibial component in relationship to the geometric centre and tibial tubercle was most frequently used.

Conclusion

This systematic review shows a strong preference for 3D-CT to determine the component’s rotation following a TKA. The literature shows consensus on the reference points of the femoral component. In measurements of the tibial component, various techniques are used with similar results. No clear cut-off point for revision of malrotated TKA components can be stated because of limited evidence.

Level of evidence

III.

     

The femoral sulcus in total knee arthroplasty

The position of the femoral sulcus relative to the midline of the distal femoral resection in total knee arthroplasty (TKA) was studied to determine if centralized placement of the femoral component on the distal femur was justified in terms of aligning the prosthetic sulcus with the native femoral sulcus. The location of the femoral sulcus was studied in 112 consecutive patients undergoing TKA. The mean sulcus position was 0.7 mm lateral to the midline of the distal femoral resection (SD 1.4, 95% CI, 0.5–1.0 mm). However, the variation in sulcus positions ranged from 4 mm medial to 4 mm lateral to the midline. The mean sulcus position in valgus knees was 1.0 mm lateral to the midline (SD 1.8), and that in varus knees was 0.7 mm lateral to the midline (SD 1.2) (P = 0.501). It appears prudent to centre the femoral component on the native sulcus rather than the midline of the distal femoral resection, so as to ensure accurate alignment of the prosthetic sulcus with the native sulcus and to encourage normal patella tracking.     

Increased flexion position of the femoral component reduces the flexion gap in total knee arthroplasty

Background

The symmetry and equality of the flexion and extension gap are essential for successful endoprosthetic knee arthroplasty. Cruciate ligament sparing endoprosthetic designs are implanted with a measured resection technique, so that the posterior bone resection corresponds to the posterior condyle thickness. However, this correlation only applies if the sagittal alignment is set at 0°. The aim of the present study was therefore to investigate the extent to which the flexion gap is influenced by a flexed implantation of the femoral component.

Methods

The implant geometry of all available sizes of the knee systems Columbus, e.motion (Aesculap), PFC Sigma (DePuy), Natural Knee II, Innex, Nexgen LPS Flex and Gender (Zimmer), and TC Plus (Smith &; Nephew) was recorded. Based on this data, a virtual implantation of the femoral component with a sagittal alignment between 0° and 5° of flexion was simulated. The resulting flexion gaps were calculated depending on the component alignment. The relationships between component alignment (in degrees) and flexion gap (in mm) were documented for every implant.

Results

The narrowing of the flexion gap with increasing flexion was more or less linear in the range investigated and was dependent on the system used and the implant size. A narrowing of the flexion gap by 1?mm resulted from 2° (1.9°–2.3°) flexion in the e.motion prosthesis, 1.9° (1.6°–2.4°) in the Columbus, 1.6° (1.5°–1.8°) in the PFC Sigma, 2.0° (1.7°–2.4°) in the Nexgen LPS Flex and Gender, 1.7° (1.6°–1.8°) in the Innex, 2.2° (1.5°–2.6°) in the TC Plus and 2.0° (2.0°–2.1°) in the Natural Knee.

Conclusions

Even a small flexion of the femoral component leads to a reduction of the flexion gap and thus potentially to limited mobility in the measured resection technique. On the other hand, in navigation-assisted implantation, slight flexion of the component can possibly be used to adjust the flexion gap smoothly.

Level of evidence

II.     

Tibial component positioning in total knee arthroplasty: bone coverage and extensor apparatus alignment

Correct positioning of the tibial component in total knee arthroplasty (TKA) must take into account both an optimal bone coverage (defined by a maximal cortical bearing with posteromedial and anterolateral support) and satisfactory patellofemoral tracking. Consequently, a compromise position must be found by the surgeon during the operation to simultaneously meet these two requirements. Moreover, tibial tray positioning depends upon the tibial torsion, which has been shown to act mainly in the proximal quarter of the tibia. Therefore, the correct application of the tibial tray is also theoretically related to the level of bone resection. In this study, we first quantified the torsional profile given by an optimal bone coverage for a symmetrical tibial tray design and for an asymmetrical one. Then, for the two types of tibial trays, we measured the angle difference between optimal bone coverage and an alignment on the middle of the tibial tubercule. Results showed that the values of the torsional profile given by the symmetrical tray were more scattered than those from the asymmetrical one. However, determination of the mean differential angle between the position providing optimal bone coverage and the one providing the best patellofemoral tracking indicated that the symmetrical prosthetic tray offered the best compromise between these two requirements. Although the tibiofemoral joint is known to be asymmetric in both shape and dimension, the asymmetrical tray chosen in this study was found to fulfill this compromise with more difficulty. Received: 8 November 1996 Accepted: 7 April 1997