Mechanical axis-derived femoral component rotation in extramedullary total knee arthroplasty: a comparison between femoral transverse axis and transepicondylar axis

Purpose  

Correct rotational alignment of the femoral component is paramount to the success of total knee arthroplasty, but debate continues as to which method is the most reliable. The purpose of this study was to evaluate mechanical axis-derived rotational axis of the femoral component using an extramedullary femoral alignment guide system.     

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.     

Outpatient surgery for unicompartmental knee arthroplasty is effective and safe

Purpose

There has been increasing interest in accelerated programs for knee arthroplasty. We examined the efficacy and safety of an outpatient surgery (OS) pathway in patients undergoing unicompartmental knee arthroplasty (UKA).

Methods

This case–controlled study evaluates patients operated for UKA in an OS pathway (n = 20) compared to rapid recovery (RR), the current standard (n = 20). We investigated whether patients could be discharged on the day of surgery, resulting in comparable or better outcome by means of adverse events (AEs) in terms of pain (numerical rating scale, NRS), incidences of postoperative nausea and vomiting (PONV) and opiate use (<48 h postoperatively), complication and readmission rates (<3 months postoperatively). Patient-reported outcome measures (PROMS) were obtained preoperatively and 3 months postoperatively.

Results

Postoperative pain (NRS > 5) was the most common reason for prolonged hospital stay in the OS pathway. Eighty-five per cent of the patients were discharged on the day of surgery, whereas 95 % of the patients were discharged on postoperative day 3 in the RR pathway. Overall, median pain scores in both pathways did not exceed a NRS score of 5, without significant differences (RR vs. OS) in the number of patients with PONV (4 vs. 2) and opiate use (11 vs. 9) <48 h postoperatively. At 3 months postoperatively, no significant differences were found for AEs and PROMS between both pathways.

Conclusion

The results of this study illustrates that an OS pathway for UKA is effective and safe with acceptable clinical outcome. Well-established and adequate standardized protocols, inclusion and exclusion criteria and a change in mindset for both the patient and the multidisciplinary team are the key factors for the implementation of an OS pathway.

Level of evidence

Case–control study, Level III.

     

Cam impingement of the posterior femoral condyle in unicompartmental knee arthroplasty

Purpose

There has been much emphasis on the importance of cam impingement, which is a cause of pain and knee hyperflexion restriction in unicompartmental knee arthroplasty (UKA). This study aimed to correlate cam impingement in the posterior femoral condyle with an α-angle showing the severity of the impingement.

Methods

The study groups consisted of 87 knees of 74 patients operated on with phase 3 medial Oxford UKA. Postoperatively, Group A (68 knees, 78.2 %) had no remnant of cam lesion; Group B (19 knees, 21.8 %) had cam lesion remnants. In Group C (18 knees, 20.7 %), which is a subgroup of Group A, cam lesions seen preoperatively were cleaned and not seen postoperatively.

Results

The mean increase in active flexion was 20.4° (±7.3°) in Group A, 9.7° (±6.1°) in Group B and 20.8° (±7.3°) in Group C. The difference between Group A and Group B and between Group B and Group C was statistically significant (p < 0.001, p < 0.001). The mean decrease of α-angle was 11.2° (±4.1°) in Group B, and 31.1° (±3.4°) in Group C. The difference was statistically significant (p < 0.001). Mean Oxford Knee Scores were 24 preoperatively, 41 postoperatively in Group A; 22 preoperatively, 38 postoperatively in Group B; and 24 preoperatively, 40 postoperatively in Group C. The differences were not significant.

Conclusions

Posterior condylar cam lesion is an impingement which limits hyperflexion and may be an early clinical finding prior to bearing dislocation and wear. The α-angle is a marker showing the severity of this cam lesion. This problem can be overcome using intraoperative fluoroscan views during cam excison and replacing the femoral component in 105° knee flexion.

Level of evidence

II.     

Fracture of the femoral component of a Brigham unicompartmental knee: a case report

We report the failure of a femoral component in a unicompartmental knee replacement 6 years after implantation. The implant fractured 15 mm from the anterior tip, and scanning electron microscopy confirmed fatigue to be the cause of failure. The clinical and laboratory findings are presented, and the causes and implications of this mode of implant failure are discussed.     

Early migration of the cemented tibial component of unicompartmental knee arthroplasty: a radiostereometry study

Purpose

Unicompartmental knee arthroplasty has good clinical results but high revision rates. A unicompartmental knee arthroplasty design features an all-polyethylene and conforming tibial component, and we hypothesized that this may put at risk its fixation. Implant-to-bone micromotion was measured together with relevant clinical outcomes.

Methods

The migration of the tibial component in twenty patients was measured at 3, 6, 12 and 24 months, using standard radiostereometry, along with the relevant clinical outcomes using the IKS scoring system.

Results

The eighteen arthroplasties at 24 months were found successful, with very good functional (mean 87.7; SD 15.4) and knee scores (mean 94.8; SD 10.1). The means and the standard deviations of the maximum total point motion (MTPM) for the four follow-ups were, respectively, as small as 0.4 ± 0.1 mm, 0.6 ± 0.2 mm, 0.6 ± 0.3 mm and 0.7 ± 0.3 mm, an average over all patients but one. In this knee, these were 1.6, 2.1, 2.4 and 2.2 mm, therefore not at high risk of aseptic loosening according to the literature. Only one knee was found at this risk, having the MTPM from 12 to 24 months of 0.5 mm, and the component moving and sinking medially, and rising laterally.

Conclusion

At 2-year follow-up, a successful implant-to-bone fixation can be achieved in conforming all-polyethylene cemented tibial component together with excellent clinical outcomes.

Level of evidence

Prognostic studies, Level I.     

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。     

Tibial component alignment and risk of loosening in unicompartmental knee arthroplasty: a radiographic and radiostereometric study

Purpose

Unicompartmental knee arthroplasty (UKA) has shown a higher rate of revision compared with total knee arthroplasty. The success of UKA depends on prosthesis component alignment, fixation and soft tissue integrity. The tibial cut is the crucial surgical step. The hypothesis of the present study is that tibial component malalignment is correlated with its risk of loosening in UKA.

Methods

This study was performed in twenty-three patients undergoing primary cemented unicompartmental knee arthroplasties. Translations and rotations of the tibial component and the maximum total point motion (MTPM) were measured using radiostereometric analysis at 3, 6, 12 and 24 months. Standard radiological evaluations were also performed immediately before and after surgery. Varus/valgus and posterior slope of the tibial component and tibial–femoral axes were correlated with radiostereometric micro-motion. A survival analysis was also performed at an average of 5.9 years by contacting patients by phone.

Results

Varus alignment of the tibial component was significantly correlated with MTPM, anterior tibial sinking, varus rotation and anterior and medial translations from radiostereometry. The posterior slope of the tibial component was correlated with external rotation. The survival rate at an average of 5.9 years was 89 %. The two patients who underwent revision presented a tibial component varus angle of 10° for both.

Conclusions

There is correlation between varus orientation of the tibial component and MTPM from radiostereometry in unicompartmental knee arthroplasties. Particularly, a misalignment in varus larger than 5° could lead to risk of loosening the tibial component.

Level of evidence

Prognostic studies—retrospective study, Level II.     

Native femoral sulcus as a guide for the position of the femoral component in primary total knee arthroplasty

A prospective randomized study was conducted to evaluate the effects of using the native femoral sulcus as a guide for the positioning of the femoral component in primary total knee arthroplasty (TKA), especially for patellar tracking. Between 2000 and 2002, 420 cases of primary TKA were collected. All the TKAs were performed with the same approach. The cases were randomly separated into two groups. In group 1 (consisting of 202 knees), the femoral insertion of the posterior cruciate ligament and the midline of the lateral–medial femoral condyles were used as a guide for the midline position of the femoral component; while in group 2 (consisting of 218 knees), the native femoral sulcus was used as the guide for the femoral component. Intraoperatively, no thumb technique was used to check the patellar tracking. In group 1, 16 knees (7.9%) received lateral retinacular releases, while none received lateral retinacular release in group 2 (P<0.0001). The average (range) follow-up period was 40 (30–56) months. In postoperative radiographic evaluation, two knees (1%) of lateral tilting of the patella were noted in group 1; while two knees (0.91%) of lateral tilting of the patella were noted in group 2 (P=0.751). In conclusion, native femoral sulcus could be a very effective and simple guide for the medial-lateral position of the femoral component, especially for patellar tracking.The prostheses used in this series were all Nexgen LPS-FLEX PCL Substituting (Zimmer, Warsaw) prostheses.     

Medial patellofemoral ligament reconstruction for patellar maltracking following total knee arthroplasty is effective

Purpose

Maltracking of the patella after total knee arthroplasty (TKA) remains a well-recognized problem. The medial patellofemoral ligament (MPFL) has shown to be important for patellar stabilization and reconstructions of the MPFL have already shown excellent functional outcomes for patellar instability of the native knee. Nevertheless, there is only limited literature on using an MPFL reconstruction for correction of patellar maltracking after TKA. In this retrospective study, a consecutive case series was evaluated.

Methods

Between 2007 and 2010, nine patients (nine knees) with anterior knee pain and symptomatic (sub)luxations of the patella after primary or revision TKA were treated by reconstruction of the MPFL in combination with a lateral release. In two cases, an additional tibial tuberosity transfer was performed, due to insufficient per-operative correction. Pre-operative work-up included a CT scan to rule out component malrotation and disorders in limb alignment. Pre- and post-operative patellar displacement and lateral patellar tilt were measured on axial radiographs. Clinical outcome was evaluated using the visual analogue scale (VAS) satisfaction, VAS pain, dislocation rate and Bartlett patella score.

Results

Median patellar displacement improved from 29 mm (0–44) to 0 mm (0–9) post-operatively. Median lateral patellar tilt was 45° (23–62) pre-operative and changed to a median 15° (?3 to 21) post-operative. Median VAS satisfaction was 8 (5–9) and only one patient reported a subluxing feeling afterwards. The Bartlett patella score displayed a diverse picture.

Conclusions

Patellar maltracking after primary or revision TKA without malrotation can effectively be treated by MPFL reconstruction in combination with a lateral release. Only in limited cases, an additional tibial tuberosity transfer is needed.

Level of evidence

IV.     

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.     

股骨滑车轴作为全膝置换股骨旋转截骨轴线的可靠性评估

目的 研究股骨滑车轴( trochleare line,TL)作为全膝置换股骨假体旋转对位标志的可靠性. 方法 对89例正常成人膝关节CT扫描,在横断面图像上定位外科经股骨上髁轴(surgical transepicondylar axis,STEA)、股骨后髁轴(posterior condylar line,PCL)和TL.测量TL相对于STEA旋转的角度(TSA)、TL相对于PCL旋转的角度(TPA)、PCL相对于STEA旋转的角度(PCA),比较它们相对STEA的可靠性. 结果 TSA为(6.77±3.12)°、TPA为(4.22±2.64)°、PCA为(2.95±1.77)°,三种角度2×2析因分析性别、左右差异均无统计学意义(P＞0.05),秩和检验( HC=66.837,P＜0.01)结果 提示三组角度总体分布不同.TSA的变异系数较小,但标准差较大(3.12°).结论 TL仅可作为股骨假体旋转对位的辅助性标志.     

The anterior surface of the femur as a new landmark for femoral component rotation in total knee arthroplasty

Femoral component rotation is very important in avoiding complications and maximizing knee function following total knee arthroplasty. There is continuing debate over the most accurate axis to select intraoperatively to obtain the best results. There is considerable doubt over the ability of commonly used bony landmarks to produce a line parallel to the flexion–extension axis of the femur, either due to anatomical variation or due to poor reproducibility of the axes. Computer navigation was used to accurately measure the relative rotation indicated intraoperatively between bony landmarks, including a previously uninvestigated axis on the anterior surface of the femur. Measurements were taken during 193 total knee arthroplasties. There was a significant association between the Whiteside’s Line and the axis on the anterior surface of the femur. The Posterior Condlylar Axis was extremely variable when compared with the other measurements, with a wide range centered on a mean value of 4.1° internally rotated to the perpendicular of Whiteside’s Line. There were significant differences in both the Posterior Condylar Axis and Anterior Femoral Axis when comparing varus and valgus knees. The Posterior Condylar Axis was shown to be an inconsistent measurement in comparison to other bony landmarks, particularly in valgus knees. The strong correlation between the Whiteside’s Line and the Anterior Femoral Axis raises the possibility that the Anterior Femoral Axis maybe a useful landmark in identifying correct femoral component rotation.     

High rate of implant loosening for uncemented resurfacing-type medial unicompartmental knee arthroplasty

Purpose

To determine the medium-term implant survivorship, the clinical results and the failure mechanisms of a novel unicompartmental arthroplasty for uncemented resurfacing of the medial tibio-femoral compartment.

Methods

Seventy-six consecutive patients were prospectively evaluated with a mean final follow-up of 6 years (SD 5.3 months). In 44 patients, the diagnosis was osteoarthritis, and in 32 patients, it was avascular necrosis of the medial femoral condyle. The Hospital for Special Surgery Score was used for objective clinical evaluation, and a self-administered visual analogue scale was used to quantify residual pain at each observation point. Implant survivorship was determined assuming revision for any reason as endpoint.

Results

Nineteen patients were revised (6 with osteoarthritis and 13 with avascular necrosis of the medial femoral condyle). The mean interval time from index surgery to revision was 11.2 months (SD 4.66 months). Implant survivorship was higher in patients with osteoarthritis with respect to those with avascular necrosis of the medial femoral condyle (p = 0.018). Aseptic loosening was the most frequent failure mechanism. Femoral component loosening was reported in five patients and tibial component loosening was reported in other six patients. Assuming revision for any reason as endpoint, an implant survivorship of 74.3 % at 6-year follow-up was determined. In the remaining 57 patients, satisfactory clinical results were obtained. Hospital for Special Surgery Score and visual analogue scale for residual pain showed significant improvements (p < 0.03 and p < 0.045, respectively).

Conclusions

At the present time, the standard cemented implants and the conventional designs for unicompartmental knee replacement still represent the optimal solution. The authors do not recommend the widespread use of this technique.

Level of evidence

IV.

     

Kinematics of the knee after unicompartmental arthroplasty is not the same as normal and is similar to the kinematics of the knee with osteoarthritis

Purpose

It is common to assert that restoration of normal knee kinematics is essential for the best functional result after knee arthroplasty. Previous studies using the progression of the geometric centre axis have suggested that kinematics after unicompartmental arthroplasty is markedly different from the normal. For this study, the transepicondylar axis was used because this axis is closer to the flexion axis and should be a better reference for motion. The following hypothesis was tested: the transepicondylar axis would again show that the postoperative kinematics does not restore normal motion and is closer to that before replacement.

Methods

Seventeen osteoarthritic knees were tested before and after unicompartmental arthroplasty using a three-dimensional to two-dimensional registration technique tracking the transepicondylar axis to calculate translation and rotation of this axis. Results were compared for the seventeen knees before and after arthroplasty and were compared to the normal knee as measured in our previous study.

Results

Similar motion patterns in the pre- and postoperative knees were shown but both the pre- and postoperative motion were markedly different from the normal knee.

Conclusions

This result supported our hypothesis. The clinical relevance is that medial unicompartmental arthroplasty cannot restore the motion of the knee to normal in the living knee. Therefore, it would be expected that the patient for unicompartmental knee might not feel normal. It may not be possible depending on ligaments alone to restore the knee to normal, and the changes in the articular shapes and the surgical procedure may also be necessary.

Level of evidence

IV.     

Computer-assisted surgery improves rotational positioning of the femoral component but not the tibial component in total knee arthroplasty

Purpose

Computer-assisted surgery (CAS) may facilitate better positioning of total knee arthroplasty (TKA) along the coronal and lateral axes; however, there are doubts as to its usefulness in the rotational plane.

Methods

This is a prospective study of 95 TKAs comparing two groups: the CAS group and the standard equipment group. The series comprises 95 cases. A radiography of the lower limb and computer tomographies (CTs) of the femoral condylar region, the proximal end of the tibia and the ankle were performed to measure rotational angulation. A month after TKA surgery, the radiography and the CTs were repeated to analyze the position of the prosthetic components in the rotational plane.

Results

In the coronal axis, both CAS and mechanical technique improved femoro-tibial alignment, but when there are preexisting deformities ≥4°, CAS obtains better results. A strong correlation (R = 0.94, p = 0.001) was observed between the mean rotational axis measured with CT in the tibial plateau and that measured from the axis of the ankle. The mean initial femoral rotation of the complete series was 6.7° and 2.7° at 1-month follow-up (p < 0.001). In the standard instrumentation group, the femoral rotation went from 6.8° to 2.3°, whereas in the CAS group the femoral rotation went from 6.5° to 3.1° (p = 0.039), which is very close to the ideal 3° angle of external rotation. Tibial rotation changed by 5.28° for the entire patient population, but no differences were found when comparing CAS and standard instrumentation.

Conclusion

CAS improves frontal alignment in TKA, especially in the presence of preoperative deformities. In the femoral component, navigation most closely replicated the ideal 3° external rotation of the femoral component, but tibial rotation did not differ when comparing CAS to standard instrumentation.

Level of evidence

II.     

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.