Femoral Bow Predicts Postoperative Malalignment in Revision Total Knee Arthroplasty

Diaphyseal bowing may compromise axial alignment in revision total knee arthroplasty (TKA). 277 patients undergoing revision TKA were evaluated for coronal bowing and hip–knee–ankle (HKA) axis. The mean femoral bow was 1.52° ± 0.18° varus (− 10.1° to + 8.4°). The mean tibial bow was 1.25° ± 0.13° valgus (− 5.9° to + 10°). HKA axis averaged 3.08° ± 0.35° varus preoperatively compared to 0.86° ± 0.25° varus postoperatively. Inter-rater and intra-rater reliability was high. Femoral bow greater than 4° significantly correlated with postoperative HKA axis malalignment (r = 0.402, P = 0.008). 39.7% of patients deviated 3° or greater from a neutral mechanical axis with a significant difference in femoral bow (0.94° ± 0.31°, P = 0.003). Diaphyseal bowing clearly has an important effect on postoperative limb alignment in revision TKA.     

The Influence of Preoperative Deformity on Valgus Correction Angle: An Analysis of 503 Total Knee Arthroplasties

We prospectively studied variations in valgus correction angle (VCA) and the influence of preoperative limb deformity on VCA in 503 consecutive total knee arthroplasties done in 393 patients. The percentage of limbs that had VCA values less than 5° was 10.9%, and that with VCA values greater than 7° was 44.9%. The percentage of limbs with VCA greater than 7° was significantly more in varus knees, and that with VCA less than 5° was significantly more in valgus knees; preoperative deformity showed a significant correlation with VCA. Choosing a fixed-routine VCA of 5° to 7° may cause an unacceptable planning error that may be minimized by individualizing VCA or using computer navigation.     

Varus Gonarthrosis Predisposes to Varus Malalignment in TKA

Postoperative alignment is a predictor for long-term survival of total knee arthroplasty (TKA). The purpose of this study was to evaluate whether or not preoperative deformities predispose to intraoperative malposition of TKA components. A retrospective radiographic analysis of 53 primary TKA cases was performed. Preoperative AP hip to ankle and lateral knee radiographs were compared with postoperative views to evaluate component positioning. The following angles were measured: the hip–knee–ankle (HKA) angle expressing the mechanical axis of the leg, the mechanical lateral distal femur angle (mLDFA), the medial proximal tibia angle (MPTA), the posterior distal femur angle (PDFA), and the posterior proximal tibia angle (PPTA). Postoperative measurement of the HKA revealed 34.0% of the cases had a deviation of >±3° from neutral alignment. Sixteen knees (30.2%) were in varus and, with one exception, all presented with severe varus gonarthrosis prior to surgery with a mean tibiofemoral angle of 12.4° compared with 1.0° of valgus in the optimally aligned group. Patients (93.3%) with preoperative valgus malalignment showed optimal postoperative HKA. Odds ratios for malalignment of TKA for varus knees in comparison with valgus knees were 7.1 for HKA, 2.4 for MPTA, 4.9 for PDFA, and 1.7 for PPTA. The overall number of outliers in the presented data corresponds well with reports from other authors using different implants and guide systems. The presented data indicate that patients with preoperative varus alignment have a higher risk of postoperative implant malposition than patients with valgus alignment. The data supports that preoperative varus deformity predisposes to varus malposition of TKA. The risk for intraoperative malposition is significantly lower in valgus knees.     

Accuracy of Image-Free Computer Navigated Total Knee Arthroplasty Is Not Compromised in Severely Deformed Varus Knees

In severe varus knee deformity, image-free computer navigated total knee arthroplasty (TKA) may result in a malaligned knee. The aim of this study was to compare the results of 17 severe varus knees (≥ 20°) and 81 varus knees (< 20°) that underwent image-free computer navigated TKA and analyze postoperative malalignment. Computer navigated TKA was performed according to standard protocol, and component angles and mechanical axes were evaluated postoperatively with weight bearing full-length standing radiographs. All severe varus knees were corrected to within 3° of neutral lower limb alignment despite having a mean preoperative varus deformities of 22.4°. Neutral alignment was obtained in 88.9% of the varus group (mean preoperative varus deformity of 11.7°), without significant difference between the two groups. No significant difference was found in either the femoral or tibial component angles, or in the frequency of complications. Severity of varus deformity did not affect the accuracy of image-free computer navigated TKA.     

Tibia Valga Morphology in Osteoarthritic Knees: Importance of Preoperative Full Limb Radiographs in Total Knee Arthroplasty

Osteoarthritis of the knee is associated with deformities of the lower limb. Tibia valga is a contributing factor to lower limb alignment in valgus knees. We evaluated 97 valgus knees and 100 varus knees. Long-leg films were taken in weight bearing with both knees in full extension. For valgus knees, 52 knees (53%) had a tibia valga deformity. Average tibia valgus deformation was 5.0°. For varus knees, there was only 1 case of tibia valga (1%), with a deformation of 2.5°. The aim of this study was to assess the prevalence of primary tibia valga in valgus and varus knees and understand how it affects our approach to total knee arthroplasty (TKA). We recommend having full-leg length films when planning for TKA in valgus knees.     

Computer-Assisted Total Knee Arthroplasty for Arthritis With Extra-articular Deformity

Forty extra-articular deformities (22 femoral and 18 tibial) in 34 patients (mean age, 63.1 years) were studied. Mean coronal extra-articular deformity was 9.3°; mean preoperative limb alignment was 166.7°. Three limbs underwent simultaneous corrective osteotomy; the rest were treated with intra-articular correction during computer-assisted total knee arthroplasty (TKA). Mean postoperative limb alignment was 179.1°. At a mean follow-up of 26.4 months, the Knee Society knee score improved from a mean preoperative score of 49.7 to 90.4 points postoperatively; function score improved from 47.3 to 84.9 points. Computer-assisted TKA is a useful alternative to conventional TKA for knee arthritis with extra-articular deformity where accurate restoration of limb alignment may be challenging because of the presence of a deformed tibia or femur or in the presence of hardware.     

The Impact of Coronal Alignment on Revision in Medial Fixed-Bearing Unicompartmental Knee Arthroplasty

BackgroundTo better define the optimal alignment target for medial fixed-bearing unicompartmental knee arthroplasty (UKA), this study compares the postoperative mechanical alignment of well-functioning UKAs against 2 groups of failed UKAs, including revisions for progression of lateral compartment osteoarthritis (“Progression”) and revisions for aseptic loosening or subsidence (“Loosening”).MethodsFrom our prospective institutional database of 3351 medial fixed-bearing UKAs performed since 2000, we identified 37 UKAs revised for Progression and 61 UKAs revised for Loosening. Each of these revision cohorts was matched based on age at surgery, gender, body mass index, and postoperative range of motion with unrevised UKAs that had at least 10 years of follow-up and a Knee Society Score of 70 or greater without subtracting points for alignment (“Success” groups). Postoperative alignment was quantified by the hip-knee-ankle (HKA) angle measured on long-leg alignment radiographs.ResultsThe mean HKA angle at 4-month follow-up for the Progression group was 0.3° ± 3.6° of valgus compared to 4.4° ± 2.6° of varus for the matched Success group (P < 0.001). For the Loosening group, the mean HKA angle was 6.1° ± 3.1° of varus versus 4.0° ± 2.7° of varus for the matched Success group (P < 0.001).ConclusionsPatients with well-functioning UKAs at 10 years exhibited mild varus mechanical alignment of approximately 4°, whereas patients revised for progression of osteoarthritis averaged more valgus and those revised for loosening or subsidence averaged more varus. The optimal mechanical alignment for medial fixed-bearing UKA survival with contemporary polyethylene is likely slight varus.     

Does Calipered Kinematically Aligned TKA Restore Native Left to Right Symmetry of the Lower Limb and Improve Function?

Background

Kinematically aligned total knee arthroplasty (KA TKA) strives to restore the native left to right symmetry of the lower limb; however, the reproducibility of achieving this target is unknown. The present study determined the proportion of patients with left to right symmetry and the improvement in patient-reported function after calipered KA TKA.

Effect of Total Knee Arthroplasty on Coronal Alignment of the Ankle Joint

BackgroundThe effect of total knee arthroplasty (TKA) on the ankle joint is not entirely clear. The purpose of this study is to assess postoperative changes in the coronal alignment of the ankle joint in patients undergoing TKA for various degrees of knee deformity.MethodsThis retrospective study included 107 patients who had undergone TKA for primary osteoarthritis. In all cases, preoperative coronal alignment deformity of the knee was corrected in an attempt to restore the native mechanical axis of the knee. Patients were stratified into 3 groups according to the degree of knee coronal alignment correction achieved intraoperatively: group 1 (<10° varus/valgus correction, n = 60), group 2 (≥10° varus correction, n = 30), and group 3 (≥10° valgus correction, n = 17). Knee/ankle alignment angles were measured on full-length, standing anteroposterior imaging preoperatively and postoperatively and included the following: hip-knee-ankle angle, tibial plafond inclination (TPI), talar inclination (TI), and tibiotalar tilt angle.ResultsSignificant changes in ankle alignment, specifically with regard to TPI (9.5° ± 6.9°, P < .01) and TI (8.8° ± 8.8°, P = .03) were noted in the ≥10° valgus correction group compared to the other 2 groups. Regardless of the degree of knee deformity correction, TKA did not lead to significant changes in the tibiotalar tilt angle.ConclusionA correction of ≥10° in a genu valgum deformity can affect ankle joint alignment, leading to alterations in TPI and TI. These findings need to be taken into consideration in assessing candidates for TKA as a possible cause of postoperative ankle pain.     

Does Residual Varus Alignment Cause Increasing Varus Laxity at a Minimum of Five Years After Total Knee Arthroplasty?

Background

The purpose of this study is to investigate whether varus-valgus laxity of cruciate-retaining (CR) total knee arthroplasty (TKA) changes between 1 year and >5 years after surgery based on postoperative limb alignment.

Does axial limb rotation affect the alignment measurements in deformed limbs?

The long-term outcome of total knee arthroplasty and femoral or tibial osteotomy is related to the ability of the surgeon to achieve the desired alignment based on preoperative planning. This study evaluates the effect of axial rotation on measured tibiofemoral angles and the angle formed between the anatomic and mechanical axes of the femur in lower extremities with valgus and varus deformities. A comparison study of the measured tibiofemoral angles indicated a statistically significant effect in models with severe vagus or varus deformity when rotated 10 degrees internally or externally. In the second part of the study, the measured angle between the anatomic and mechanical axes of the femur never varied by more than 1 degree, despite a 40 degrees are of rotation. The results of the study indicate the tibiofemoral angle measurements are more sensitive to axial limb rotation in lower extremities with valgus or varus deformity than are normally aligned limbs. In preoperative planning of total knee arthroplasty, the measured angle between the anatomic and mechanical axes of the femur is less effected by limb rotation, regardless of the degree of valgus or varus deformity.     

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.     

The relationship between postoperative ligament balance and preoperative varus deformity in total knee arthroplasty.

We hypothesize that in knees with severe varus deformities, varus-valgus ligament imbalance tends to remain postoperatively after total knee arthroplasty. The purpose of this study was to evaluate the correlation between preoperative varus deformity and postoperative ligament balance quantitatively measured by stress radiograph using Telos SE in total knee arthroplasty. In this study, 44 knee arthroplasties in 32 patients were evaluated. We defined the angle in varus and valgus stress as "varus angle" and "valgus angle," and the sum of varus angle and valgus angle as "sum of varus-valgus angle." There was a significant correlation between preoperative lateral femoral angle and varus angle (p < 0.0001, r = 0.56), which means that postoperative ligament imbalance tends to remain in knees with preoperative varus deformities. There was a significant correlation between the postoperative period and the sum of varus-valgus angle, which suggests that knees with total knee arthroplasty have potential to increase laxity postoperatively.     

Implant Survival and Function Ten Years After Kinematically Aligned Total Knee Arthroplasty

Background

Alignment in the varus or valgus outlier range of the tibial component, knee, and limb might adversely affect the long-term results of kinematically aligned total knee arthroplasty (TKA) particularly when patients are selected without restricting the degree of preoperative varus-valgus and flexion deformity.

Alignment in Medial Fixed-Bearing Unicompartmental Knee Arthroplasty: The Limb Has a Leg Up on the Component

BackgroundTo assess how implant alignment affects unicompartmental knee arthroplasty (UKA) outcome, we compared tibial component alignment of well-functioning UKAs against 2 groups of failed UKAs, revised for progression of lateral compartment arthritis (“Progression”) and aseptic loosening (“Loosening”).MethodsWe identified 37 revisions for Progression and 61 revisions for Loosening from our prospective institutional database of 3351 medial fixed-bearing UKAs performed since 2000. Revision cohorts were matched on age, gender, body mass index, and postoperative range of motion with “Successful” unrevised UKAs with minimum 10-year follow-up and Knee Society Score ≥70. Tibial component coronal (TCA) and sagittal (TSA) plane alignment was measured on postoperative radiographs. Limb alignment was quantified by hip-knee-ankle (HKA) angle on long-leg radiographs. In addition to directly comparing groups, a multivariate logistic regression examined how limb and component alignments were associated with UKA revision.ResultsIn the Progression group, component alignment was similar to the matched successes (TCA 3.6° ± 3.5° varus vs 5.1° ± 3.5° varus, P = .07; TSA 8.4° ± 4.4° vs 8.8° ± 3.6°, P = .67), whereas HKA angle was significantly more valgus (0.3° ± 3.6° valgus vs 4.4° ± 2.6° varus, P < .001). Loosening group component alignment was also similar to the matched successes (TCA 6.1° ± 3.7° varus vs 5.9° ± 3.1° varus, P = .72; TSA 8.4° ± 4.6° vs 8.1° ± 3.9°, P = .68), and HKA was significantly more varus (6.1° ± 3.1° varus vs 4.0° ± 2.7° varus, P < .001). Using a multivariate logistic regression, HKA angle was the most significant factor associated with revision (P < .001).ConclusionIn this population of revised UKAs and long-term successes, limb alignment was a more important determinant of outcome than tibial component alignment.Level of EvidenceLevel III case-control study.     

全膝关节置换术中股骨内髁滑移截骨治疗伴有关节外畸形的膝内翻

目的：探讨股骨内髁滑移截骨术（medial condyle sliding osteotomy, MCSO）在全膝关节置换术中纠正患者内翻膝关节外畸形的临床疗效。方法通过回顾性研究2013年1月至2015年12月在第三军医大学附属西南医院关节外科中心于全膝关节置换术中采用MCSO在关节内纠正股骨侧的关节外内翻畸形的12例患者,统计该组患者手术前后的股骨远端外侧力线角（mechanical lateral distal femoral angle, mLDFA）、髋-膝-踝（hip?knee?ankle, HKA）角、疼痛视觉模拟量表（visual analogue scale, VAS）评分及美国膝关节协会（American Knee Society, AKS）综合评分系统中的膝评分和功能评分等,评价MCSO纠正关节外的内翻畸形的效果。结果本组患者随访6~40个月,无感染、骨折、假体松动、截骨不愈合等并发症发生。本组患者手术前后的mLDFA分别为117.4°±4.7°、91.6°±1.4°;手术前后的HKA角分别为167.2°±9.8°、179.6°±1.6°;手术前后的VAS评分分别为（6.4±1.1）分、（1.8±1.5）分;手术前后的AKS膝评分分别为（60.2±17.6）分、（92.6±9.4）分;手术前后的AKS功能评分分别为（69.4±21.3）分、（87.6±14.9）分。手术前后以上指标的差异均有统计学意义（均P＜0.05）。结论在合并关节外畸形的内翻膝的关节置换手术中,采用MCSO技术可以正确纠正内翻力线,更容易实现伸屈间隙平衡,达到满意的手术疗效。能有效避免对膝关节后内侧和内侧组织结构的过度松解,从而避免单纯依赖软组织松解而导致的屈曲位内侧间隙松弛及髌股关节对位不良等问题。     

Risk factors of post-operative malalignment in fixed-bearing medial unicompartmental knee arthroplasty

Purpose

The purpose of this study was to identify risk factors of post-operative malalignment in medial unicompartmental knee arthroplasty (UKA) using multivariate logistic regression.

Methods

We retrospectively enrolled 92 patients who had 127 medial UKAs. According to post-operative limb mechanical axis (hip-knee-ankle [HKA] angle), 127 enrolled knees were sorted into acceptable alignment with HKA angle within the conventional?±?3 degree range from a neutral alignment (n?=?73) and outlier with HKA angle outside?±?3 degree range (n?=?54) groups. Multivariate logistic regression was used to analyse risk factors including age, gender, body mass index, thickness of polyethylene tibial insert, pre-operative HKA angle, distal femoral varus angle (DFVA), femoral bowing angle (FBA), tibial bone varus angle (TBVA), mechanical distal femoral and proximal tibial angles, varus and valgus stress angles, size of femoral and tibial osteophytes, and femoral and tibial component alignment angles.

Results

Pre-operative DFVA, TBVA and valgus stress angle were identified as significant risk factors. As DFVA increased by one degree, malalignment was about 45 times probable (adjusted OR 44.871, 95 % CI 2.608–771.904). Shift of TBVA and valgus stress angle to a more varus direction were also significant risk factors (adjusted OR 13.001, 95 % CI 1.754–96.376 and adjusted OR 2.669, 95 % CI 1.054–6.760).

Conclusions

Attention should be given to the possibility of post-operative malalignment during medial UKA in patients with a greater varus angle in pre-operative DFVA, TBVA and valgus stress angle, especially with a greater varus DFVA, which was the strongest predictor for malalignment.

     

Alignment of computer-assisted total knee arthroplasty in patients with altered hip center

This study aimed to determine limb and component alignment after computer-assisted total knee arthroplasty in 30 patients (32 limbs) with an altered hip center due to a prior hip implant or deformed femoral head. There were no outliers greater than ±3° in the postoperative coronal alignment of the limb and the femoral component in relation to the altered hip center. Two limbs (8%) were more than ±3° for coronal alignment of the femoral component in relation to the anatomical hip center and 96% of limbs had less than 2° deviation in relation to the altered hip center. Computer-navigated total knee arthroplasty results in accurate restoration of lower limb and component alignment in patients with prior hip implants or deformed femoral heads where accurate restoration of alignment may be challenging due to altered hip center.     

Evaluating distal femoral torsion and posterior condylar line reliability for adjusting femoral component rotation in TKA,Egyptian population radiographic study

BackgroundFemoral component rotational alignment is critical for successful TKA. The primary study objective is to measure the preoperative distal femoral torsion (DFT) of an Egyptian patient’s cohort using a seated posteroanterior (PA) knee radiograph. The secondary objectives are to check the intraoperative reliability of using the posterior condylar line (PCL) as a reference for rotation and to measure postoperative component rotation using the same radiographic technique.Methods100 arthritic knees, 22 males, 78 females, 95 Varus and five valgus. A long anteroposterior radiograph [Hip to knee to ankle (HKA)] for coronal alignment assessment, and the anatomical posterior condylar angle (aPCA) between the anatomical transepicondylar axis (aTEA) and the PCL was measured in the seated PA knee radiographs for evaluating the DFT and component rotation. Intraoperative rotation was adjusted to 3° external rotation to the PCL.ResultsHKA improved from a preoperative mean 170.4° ± 6.2 to a postoperative mean 178.3° ± 1.5 (p < 0.005). DFT was internal in all knees; the mean aPCA was −4.5 ± 2.4 (0° to −9°), femoral component rotation significantly changed to a mean aPCA of −3.6 ± 2.3 (0° to −7°) (p = 0.005). Acceptable intraoperative patellar tracking in 94%, and patellar subluxation needed a lateral retinacular release in 2% (two valgus knees). The preoperative DFT was not affected by sex or direction of coronal deformity; more external DFT noticed in severe varus deformity.ConclusionsAll keens had an internal DFT not affected by sex, or coronal deformity direction. Using PCL as a guide to adjust femoral component rotation is a valid technique in our population.