A morphometric study of normal and varus knees

A Simple Surgical Technique for Correction of Varus Deformity in Advanced Osteoarthritis of Knees by Medial Femoral Condylar Sliding Osteotomy-Description of Procedure and short term Outcome-A Prospective Study

Background

Advanced osteoarthritis of knees with varus deformity consists of attenuation of lateral structures with contracture of the posteromedial structures and formation of medial osteophytes. The conventional step-wise medial and posteromedial release with measured resection may sometimes hinder achievement of perfectly balanced flexion and extension gaps with maintenance of flexion stability, without the use of a constrained prosthesis. Medial femoral epicondylar sliding osteotomy tailors the balancing to the need of the kinematics of the native knee and precludes the use of a constrained implant.

Methods

15 patients with Ahlbäck Grades III through V osteoarthritic changes at Howrah Orthopaedic Hospital were included in a prospective cohort case series with a minimum period of follow-up being 12 months. Physical examination, clinical questionnaire and radiographic evaluation were done post-operatively for objectification by functional Knee Society and Oxford Knee Scores respectively.

Results and Analysis

The mean post-operative femorotibial angulation ameliorated to a value of 3.73 ± 1.58° from 18.67 ± 4.2° in the pre-operative stage. The mean overall Range of Motion of operated knee was 109.87 ± 6.86° with no residual frontal laxity and/or laxity in the coronal plane. The mean amount of resection of tibial plateau in patients with severe varus deformity was kept to a minimum, 6.56 mm from the least deficient portion of the lateral condyle. There were no complications as regards component loosening and/or surgical-site infection.

Conclusion

The main objective of balancing a severely varus-afflicted knee is to preserve as much of the Medial Collateral Ligament as possible, to retain its check rein function and not jeopardise the stability. This is ensured by distalisation and posteriorizing the medial epicondyle by an incomplete osteotomy in addition to modest tibial resection fetching a non-isometric point of knee flexion. All osteotomies united by bony union and restoration of kinematic alignment. The limitation of this study however includes the lack of long-term results, such as late instability and polyethylene wear.

Comparison of Time Taken in Conventional versus Active Robotic-Assisted Total Knee Arthroplasty

Background

Computer- and robotic-assisted total knee replacement procedures have been shown to improve the accuracy of the implant size. It also allows dynamic confirmation of the implant and limb alignment during total knee arthroplasty (TKA). The major inhibition of the arthroplasty surgeon in adapting to the robotic-assisted TKA (RA-TKA) is the extra time spent during the registration process and milling of the bone with the robot. The aim of the study was to ascertain the extra time spent during these 2 steps as compared to the conventional TKA (C-TKA).

Methods

It is a prospective study involving 30 patients each in the conventional TKA and RA-TKA operated by the same surgical team. The patients were given a choice between the C-TKA and RA-TKA and consecutive 30 cases in each group were studied by an independent observer. In the C-TKA group, the time for the application of appropriate zigs and execution of the bone cuts and soft-tissue release was recorded whereas in the RA-TKA group, the time taken for fixation of the tibial and femoral arrays and bone registration and bone milling with robot and required soft-tissue release was measured.

Results

The preoperative patient characteristics were the same in both groups. The time taken in the C-TKA and RA-TKA groups was 24.77 ± 1.92 minutes and 25.03 ± 3.27 minutes, respectively, which is statistically insignificant (p = 0.709).

Conclusions

The study findings show that RA-TKA does not take additional time than C-TKA.

Changes in the femoral varus and rotational profiles are correlated in women with varus osteoarthritic lower limbs

INTRODUCTION

Previous studies have reported the relationship between coronal alignment of the lower limbs and the rotational profile of the femur and tibia. However, the relationship between coronal alignment of the femur and tibia and their rotational profiles in patients with varus osteoarthritic knees is unclear.

METHODS

One hundred women with varus osteoarthritic knees (varus OA group) and 50 women with neutrally aligned lower limbs without osteoarthritis (non-OA group) were evaluated retrospectively. The coronal alignment and rotational profile of the femur and tibia were evaluated, and the correlation between coronal alignment and rotational profile was analyzed, respectively.

RESULTS

The femoral anteversion, posterior condylar angle of the distal femur, and tibial torsion were significantly smaller in the varus OA group than in the non-OA group. In the varus OA group, the femoral anteversion and rotational profile of the distal femur had significantly negative correlations with the degree of femoral varus, while tibial torsion was not related to the degree of tibial varus. In the non-OA group, there was no relationship between coronal alignment and rotational profiles of the femur and tibia in both the varus OA and non-OA groups.

CONCLUSION

Femoral anteversion and the rotational profile of the distal femur were negatively correlated with the degree of femoral varus in Asian women with varus osteoarthritic knees. This study enhanced the understanding of the relationship between changes in coronal alignment of the femur and tibia and their rotational profiles in patients with varus osteoarthritic lower limbs, although this study was limited by the small sample sizes and methodological quality.

Intraindividual variance of lower limb rotation in patients with bilateral knee osteoarthritis

Purpose

To determine the side-to-side difference in intraindividual rotation alignment of patients with bilateral varus-type knee osteoarthritis (OA) and compare it with control subjects.

Methods

This retrospective study enrolled 60 patients with bilateral varus-type knee OA and 50 control subjects. All cases underwent bilateral lower limb CT angiography. Bilateral femoral and tibial rotation alignment were measured, and the overall lower limb rotation was calculated by two different methods. Method 1 was calculated by subtracting angle of the femoral torsion from the tibial torsion and method 2 was determined by relative rotation of the femoral neck angle to bimalleolar angle. The intraindividual variance and differences between the two groups were analyzed.

Results

Both OA and control samples showed significant differences between right and left for all measurements. Femoral torsion for control group was 10.4 ± 5.5°, tibial torsion was -22.1 ± 6.1°, and overall leg rotation by method 1 was -15.6 ± 7.2° and method 2 was -11.7 ± 8.2°. Femoral torsion, tibial torsion, method 1, and method 2 in the patients with OA were 8.2 ± 6.3°, -18.6 ± 4.1°, -14.9 ± 7.9°, and -10.4 ± 7.6°, respectively. Patients with OA showed a more pronounced retroversion in the femur (p = 0.008) and more internal rotation in the tibia (p < 0.001). No statistical significance of both methods was found between the two groups. Patients with OA had a greater median side-to-side absolute difference in all measurements, though the differences of both two methods of overall lower limb rotation were not statistically significant.

Conclusions

The discrepancy of side-to-side differences of bilateral lower limb rotation ought to be noticed with caution in diagnosing and treating rotational deformities of the lower limb, especially for patients with bilateral knee OA.

Efficacy of the Pre-operative Three-Dimensional (3D) CT Scan Templating in Predicting Accurate Implant Size and Alignment in Robot Assisted Total Knee Arthroplasty

Background

Nearly 20% of Total knee Arthroplasty patients remain dissatisfied. This is a major concern in twenty-first century arthroplasty practice. Accurate implant sizing is shown to improve the implant survival, knee balance and patient reported outcome. Aim of the current study is to assess the efficacy of pre-operative three-dimensional (3D) CT scan templating in a robot-assisted TKA in predicting the correct implant sizes and alignment.

Materials and methods

Prospectively collected data in a single center from 30 RA-TKAs was assessed. Inclusion criterion was patients with end stage arthritis (both osteoarthritis and rheumatoid arthritis) undergoing primary TKA. Patients undergoing revision TKA and patients not willing to participate in the study were excluded. Preliminary study of ten patients had indicated almost 100% accuracy in determining the implant size and position. Sample size was estimated to be 28 for 90% reduction in implant size and position error with α error of 0.05 and beta error of 0.20 with power of study being 80. Post-operative radiographs were assessed by an independent observer with respect to implant size and position. The accuracy of femoral and tibial component sizing in the study was compared with the historic control with Chi-squared test. The p value < 0.05 was considered significant.

Results

The pre-operative CT scan 3D templating accuracy was 100% (30 out of 30 knees) for femoral component and 96.67% (29 out of 30 knees) for tibial component. The implant position and limb alignment was accurate in 100% of patients. The accuracy of femoral component and tibial component sizing is statistically significant (Chi-squared test, p value 0.0105 and 0.0461, respectively).

Conclusion

The study results show the effectiveness of pre-operative 3 D CT scan planning in predicting the implant sizes and implant positioning. This may have a potential to improve the implant longevity, clinical outcomes and patient satisfaction.

Asymmetry of Posterior Condyles in Resection Plane and Axial Curvature for Total Knee Arthroplasty

OBJECTIVE

Understanding the morphology of the distal femur is essential for improving bone-implant match in total knee arthroplasty (TKA) and understanding the mechanisms behind knee kinematics. However, little is known about the asymmetry of the posterior condyles. Thus, this study aimed to thoroughly investigate asymmetries in sizes and shapes between the medial and lateral posterior condyles before and after femoral resections during TKA in osteoarthritic (OA) knees.

METHODS

Three-dimensional femoral models of 74 OA knees were constructed using computed tomography images. The morphologic measurements of the posterior condyle pre- and post-simulated osteotomy for TKA included the radii of the posterior condyles fitted to a circle on the sagittal and axial planes of the femoral coordinate system, the inclination angle of the articular surface and resected surface, and the width and height of the resected surface. Differences in the data were assessed using Student's t-test, and correlations were evaluated using the Pearson product-moment correlation.

RESULTS

The radii of the medial posterior condyles fitted to the circle were, on average, 6 mm larger than those of the lateral condyles on the axial plane (p < 0.001) and 0.7 mm smaller than those of the lateral condyles on the sagittal plane (p = 0.046). The inclination angles of the medial and lateral posterior condyles on the axial plane were significantly different with both pre-simulated and post-simulated osteotomy, respectively (both p < 0.001). The resected plane of the lateral posterior condyles displaced opposite inclination directions between the distal and proximal portions. Neither heights or widths of the medial posterior condyles were significantly different from those of their lateral counterparts (both p > 0.107).

CONCLUSIONS

This study found asymmetrical inclination of the resected surface and coronal radii between the medial and lateral posterior condyles, which may relate to the posterolateral overhang of the lateral condyle after TKA and the progression of the knee OA. These findings provides valuable morphological information and may help improve the implant designs for TKA.

Slight femoral under-correction versus neutral alignment in total knee arthroplasty with preoperative varus knees: a comparative study

Background

This study aimed to compare the short-term clinical results of slight femoral under-correction with neutral alignment in patients with preoperative varus knees who underwent total knee arthroplasty.

Methods

The medical records and imaging data were retrospectively collected from patients who had undergone total knee arthroplasty in our hospital from January 2016 to June 2019. All patients had varus knees preoperatively. Upon 1:1 propensity score matching, 256 patients (256 knees) were chosen and divided into a neutral alignment group (n=128) and an under-correction group (n=128). The patients in the neutral group were treated with the neutral alignment. In the under-correction group, the femoral mechanical axis had a 2° under-correction. The operative time, tourniquet time and the length of hospital stay in the two groups were recorded. The postoperative hip-knee-ankle angle, frontal femoral component angle and frontal tibial component angle were measured. Patient-reported outcome measures were also compared.

Results

The operative time, tourniquet time and the length of hospital stay in the under-correction group were significantly shorter than the neutral alignment group (P<0.05). At the 2-year follow-up, the under-correction group had a larger varus alignment (P<0.05) and a larger frontal femoral component angle (P<0.05), and the frontal tibial component angles of the two groups were comparable. Compared with the neutral alignment group, the slight femoral under-correction group had significantly better patient-reported outcome measures scores (P<0.05).

Conclusion

For varus knees treated with total knee arthroplasty, alignment with a slight femoral under-correction has advantages over the neutral alignment in terms of the shorter operative time and better short-term clinical results.

Level of evidence

III

Three-dimensional morphometric differences of resected distal femurs and proximal tibias in osteoarthritic and normal knees

BACKGROUND

There is a paucity of data concerning the morphological differences of resected distal femurs and proximal tibias in osteoarthritic (OA) and normal knees. The objective of this study was to determine whether morphometric differences in the surfaces of resected distal femurs and proximal tibias exist between OA and normal knees in a Chinese population.

METHODS

Ninety-four OA knees and ninety-five normal knees were evaluated in Chinese individuals. Computed tomography was used to measure the femoral mediolateral (fML), medial anteroposterior (fMAP), lateral anteroposterior (fLAP), medial condylar width (fMCW), lateral condylar width (fLCW), medial posterior condylar curvature radii (fMCR), lateral posterior condyle curvature radii (fLCR), fML/fMAP aspect ratio, tibial mediolateral (tML), middle anteroposterior (tAP), medial anteroposterior (tMAP), and lateral anteroposterior (tLAP) tML/tMAP aspect ratio to determine the morphologic differences between OA and normal knees.

RESULTS

The average fMCW and tMAP dimensions of OA knees were larger than those of normal knees in both male and female (p <0.05). The fMAP/fML aspect ratio and tMAP/tML aspect ratio were also significantly different in both sexs (p <0.05). OA knees have an oval-shaped distal femur with a wider ML length and more spherical-shaped proximal tibiae with relatively narrow ML dimensions.

CONCLUSIONS

The study revealed the morphological differences in fMCW, tMAP, fMAP/fML and tMAP/tML between OA and normal knees in both males and females. These findings may provide guidelines that can be used to design better knee implants that are more size-matched for OA knees.

Medialization of the mechanical axis of the tibia is related to lateralization of the tibial tuberosity in knee osteoarthritis

PURPOSE

To determine whether medialization of the proximal tibia due to a varus deformity is related to lateralization of the tibial tuberosity in varus knee osteoarthritis (OA).

METHODS

A total of 120 knees that underwent osteotomies around the knee for varus knee OA were enrolled. Mechanical medial proximal tibial angle (mMPTA) was measured on radiographs. The angle between the mechanical and anatomical axes of the tibia (angle MA) and the distance between the centre of the tibial plateau and the anatomical axis (distance MA) were measured in the coronal plane on computed tomography images. The tibial tuberosity-posterior cruciate ligament (TT-PCL) distance, the distance between the midpoint of the tibial tuberosity and the centre of the tibial plateau (TT-centre distance), and the angle between the line through the midpoint of the tibial tuberosity and the centre of the tibial plateau and the anteroposterior axis (TT-centre angle) were measured in the axial plane. The correlations of these parameters were evaluated.

RESULTS

mMPTA correlated negatively with angle MA (r = -0.37, P < 0.01) and distance MA (r = -0.55, P < 0.01). Angle MA and distance MA correlated with TT-PCL distance (r = 0.39, P < 0.01, r = 0.42, P < 0.01), TT-centre distance (r = 0.35, P < 0.01, r = 0.38, P < 0.01) and TT-centre angle (r = 0.36, P < 0.01, r = 0.36, P < 0.01).

CONCLUSIONS

Medialization of the proximal tibia due to a varus deformity may induce lateralization of the tibial tuberosity.

Coronal and axial alignment relationship in Caucasian patients with osteoarthritis of the knee

Individualized pre-operative assessment of the patterns of the lower extremity anatomy and deformities in patients undergoing total knee arthroplasty seems essential for a successful surgery. In the present study, we investigated the relationship among the coronal alignment and the rotational profile of the lower extremities in the Caucasian population with end-stage knee osteoarthritis. We conducted a prospective study of 385 knees that underwent a pre-operative three-dimensional computed tomography-based model. The lower extremity alignment was determined (mechanical tibiofemoral or hip-knee-ankle angle, supplementary angle of the femoral lateral distal angle, and proximal medial tibial angle). For each case, the femoral distal rotation (condylar twist angle), the femoral proximal version, and the tibial torsion were determined. As the coronal alignment changed from varus to valgus, the femoral external rotation increased (r = 0.217; p < 0.0005). As the coronal alignment changed from varus to valgus, the external tibial torsion increased (r = 0.248; p < 0.0005). No correlation was found between the global coronal alignment and the femoral version. The present study demonstrates a linear relationship between the coronal alignment and the rotational geometry of the distal femur. This correlation also occurs with the tibial torsion. Perhaps outcomes of total knee arthroplasty surgery might be improved by addressing these deformities as well.

Increased external rotation of the osteoarthritic knee joint according to the genu varum deformity

PURPOSE

To evaluate the rotational profile of the lower extremity using computed tomography (CT) in accordance with the degree of varus deformity in medial condyle-affected knee joint osteoarthritis (OA).

METHODS

This retrospective study included 1036 patients (872 lower extremities) with end-stage knee OA. The coronal alignment of the lower extremity was measured using standing anteroposterior radiography. The CT parameters of femoral anteversion and tibial torsion were assessed in relation to the knee joint. The axes were the femoral neck axis; the distal femoral axis, which was composed of the anterior trochlear axis, the clinical transepicondylar axis, and the posterior condylar axis; the axis of the proximal tibial condyles; and the bimalleolar axis.

RESULTS

There was a tendency for increased external rotation of the knee joint parameters in relation to the hip and ankle joints as varus deformity of the lower extremity increased. The relative external rotational deformity of the knee joint in relation to the hip joint had a positive value with a good correlation. The relative external rotational deformity of the knee joint in relation to the ankle joint also demonstrated a positive value with a good correlation.

CONCLUSION

The distal femur and proximal tibia (knee joint) tended to rotate externally in relation to the hip and ankle joint, respectively, as the degree of varus deformity increased. This study identified the relationship between lower extremity varus deformity and rotational deformity of knee joints with OA.

LEVEL OF EVIDENCE

III.

Patient-specific cruciate-retaining total knee replacement with individualized implants and instruments (iTotal™ CR G2)

OBJECTIVE

Treatment of tricompartimental osteoarthritis (OA) using customized instruments and implants for cruciate-retaining total knee arthroplasty. Use of patient-specific instruments and implants (ConforMIS iTotal^TM CR G2) together with a 3D-planning protocol (iView®). Retropatellar resurfacing is optional.

INDICATIONS

Symptomatic tricompartmental OA of the knee (Kellgren-Lawrence stage IV) with preserved posterior cruciate ligament (PCL) after unsuccessful conservative or joint-preserving surgical treatment.

CONTRAINDICATIONS

Knee ligament instabilities of the posterior cruciate or collateral ligaments. Infection. Relative contraindication: knee deformities >15° (varus, valgus, flexion); prior partial knee replacement.

SURGICAL TECHNIQUE

Midline or parapatellar medial skin incision, medial arthrotomy; distal femoral resection with patient-specific cutting block; tibial resection using either a cutting jig for the anatomic slope or a fixed 5° slope. Balancing the knee in extension and flexion gap using patient-specific spacer. The final tibial preparation achieved with gap-balanced placement of the femoral cutting jigs. Kinematic testing using anatomic trial components. Final implant components are cemented in extension. Wound layers are sutured. Drainage is optional.

POSTOPERATIVE MANAGEMENT

Sterile wound dressing; compressive bandage. No limitation of the active and passive range of motion. Optional partial weight bearing during the first 2 weeks, then transition to full weight bearing. Follow-up directly after surgery, at 12 and 52 weeks, then every 1-2 years.

RESULTS

Overall 60 patients with tricompartmental knee OA and preserved PCL were treated. Mean age was 66 (range 45-76) years. Minimum follow-up was 12 months. There was 1 septic revision after a low-grade infection, 1 reoperation to replace the patellar due to patellar osteoarthritis and 3 manipulations under anesthesia (MUAs) to increase range of motion. Radiographic analyses demonstrated an ideal implant fit with less than 2 mm subsidence or overhang. The WOMAC score improved from 154.8 points preoperatively to 83.5 points at 1 year and 59.3 points at 2 years postoperatively. The EuroQol-5D Score also improved from 11.1 points preoperatively to 7.7 points at 1 year postoperatively.

Intraoperative morphometric study of distal femur in Brazilian patients undergoing total knee arthroplasty

Background

Total knee arthroplasty (TKA) is the treatment option for patients with severe osteoarthritis (OA) of the knee whose symptoms are refractory to conservative management. Unfortunately, the level of patient dissatisfaction is high, reaching up to 25%. The reasons for this dissatisfaction are multifactorial, but bone-implant mismatch significantly increases the chance of pain and functional limitation. Sex-specific prosthesis designs have been developed to overcome this issue, but their use is still controversial. The primary objective of this study was to evaluate possible sex differences in the shape of the distal femur in patients with osteoarthritis. Secondary objectives were to investigate interpersonal variability of the distal femur and to determine the number of femoral implant sizes required to meet shape variations.

Methods and findings

A cross-sectional observational study prospectively compared 294 knees of 293 patients with osteoarthritis according to sex (201 female/93 male). Six intraoperative measurements were performed on the distal femur (height and width of both lateral and medial condyles, total medial-lateral width of the femur, and intercondylar distance). Sex differences and interpersonal variability were analyzed by multiple linear regressions. Measurements were also correlated with patient height. An optimization analysis was used to estimate the number of femoral implant sizes required. There were significant sex differences in the distal femur, where men had higher values than women in all measurements. Great interpersonal variability was found. The height of the lateral condyle was correlated with patient height, but the correlation was not strong. Twenty-five femoral implant sizes were required to meet the shape variations in our sample.

Conclusions

The shape of the distal femur in patients with osteoarthritis shows great interpersonal variability, with men showing significantly higher values than women. A total of 25 different implant sizes would be necessary to adequately meet the variations observed in our study population.

Measurement of the Posterior Tibial Slope Depends on Ethnicity, Sex, and Lower Limb Alignment: A Computed Tomography Analysis of 378 Healthy Participants

Background:

There is no general consensus on the normal and pathological values for the posterior tibial slope (PTS).

Purpose/Hypothesis:

The primary aim of this study was to determine standard values for the PTS in healthy participants using 3-dimensional (3D) computed tomography (CT). A secondary aim was to determine the effect of demographic factors and coronal-plane lower limb alignment on the PTS measurement. The hypothesis was that the PTS would be significantly influenced by demographic factors and coronal-plane lower limb alignment.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

A CT-based modeling and analytics system was used to examine and measure lower limb alignment and the PTS in 378 patients (193 male and 185 female; mean age, 58.3 ± 16.4 years [range, 18-92 years]; mean body mass index, 25.0 ± 4.4 kg/m²). The lateral, medial, and global PTS were measured for each patient. All measurements were constructed using algorithm-calculated landmarks, resulting in reproducible and consistent constructs for each specimen. The results were then evaluated based on ethnicity, sex, and hip-knee-ankle (HKA) angle.

Results:

The study population comprised 219 white and 159 Asian participants. The mean global, medial, and lateral PTS were 6.3° (range, –5.5° to 14.7°; 1% with ≥12°), 6.2° (range, –4.1° to 17.2°; 3% with ≥12°), and 5.3° (range, –4.7° to 16.2°; 2% with ≥12°), respectively. The lateral (Δ = –1.0° [95% CI, 0.6°-1.6°]; P < .0001) and global (Δ = –0.5° [95% CI, 0.0°-0.8°]; P = .0332) PTS were smaller in the female subpopulation. The global PTS was greater (Δ = 1.9° [95% CI, 1.5°-2.3°]; P < .0001) in the Asian subpopulation. The mean HKA angle was 179.6° (range, 170°-190°). The HKA angle was significantly correlated with the medial and global PTS. Specimens with a genu varum knee exhibited a significantly greater global (Δ = 1.2° [95% CI, 0.8°-1.7°]; P < .0001) and medial (Δ = 1.9° [95% CI, 1.3°-2.5°]; P < .0001) PTS.

Conclusion:

The present study gives a benchmark for the physiological values of the PTS in a healthy population and highlights several factors influencing the PTS, such as ethnicity, sex, and alignment. Anatomic variants with a PTS ≥12° were very uncommon (≤3%) in our Asian and white groups and thus could be considered as pathological. The PTS is a crucial anatomic factor for anterior cruciate ligament injuries and reconstruction. A general consensus is lacking regarding the cutoff for abnormal values, thus guiding standard of care. This study investigated the dispersion of global, medial, and lateral posterior plateau tibial angles in a large population representing a range of demographic diversity.

Predicting clinical outcomes after total knee arthroplasty from preoperative radiographic factors of the knee osteoarthritis

Background

Total knee arthroplasty (TKA) is the major surgical treatment for end-stage osteoarthritis (OA). Despite its effectiveness, there are about 20% of patients who are dissatisfied with the outcome. Predicting the surgical outcome preoperatively could be beneficial in order to guide clinical decisions.

Methods

One-hundred and ten knees of 110 consecutive patients who underwent TKAs for varus knees resulting from OA were included in this study. Preoperative varus deformities were evaluated by femorotibial angle (FTA), medial proximal tibial angle (MPTA) and lateral distal femoral angle (LDFA), and classified as a severe varus (SV) or a mild varus (MV) group. The osteophyte score (OS), which we developed originally, was also calculated based on the size of the osteophytes and classified as groups with more or less osteophytes. We compared preoperative and 1-year postoperative range of motion, the Knee Society Score, and Japanese Knee injury Osteoarthritis Outcome Score (KOOS) between SV and MV groups (varus defined by FTA, MPTA, or LDFA), in each group with more or less osteophytes.

Results

When varus deformities were defined by FTA, regardless of OS, postoperative KOOS subscales and/or the improvement rates were significantly higher in the SV group than in the MV group. When varus defined by MPTA, regardless of OS, there were no significant differences in postoperative KOOS subscales between groups. However, when varus defined by LDFA, scores for pain, activities of daily living (ADL), and quality of life (QOL) on postoperative KOOS and/or the improvement rates were significantly higher in the SV group than in the MV group only in patients with less osteophytes. No significant differences were found between groups in patients with more osteophytes.

Conclusions

We classified OA types by radiographic measurements of femur and tibia in combination with OS. Postoperative patient-reported outcomes were better in patients with SV knees but were poor in patients with knees with MV deformity and less osteophytes.

The native coronal orientation of tibial plateaus may limit the indications to perform a kinematic aligned total knee arthroplasty

PURPOSE

To investigate the coronal alignment of tibial plateaus in normal and osteoarthritic knees and to simulate the effects of a tibial cut performed in total knee arthroplasty (TKA) using a kinematic alignment technique with standard instrumentation.

METHODS

The coronal alignment of tibial plateaus was measured in three groups including group 1 (reference group), 50 cadaveric tibiae showing no evidence of degenerative changes of tibial plateaus; group 2, 49 patients who underwent MR of the knee, showing no or mild degenerative changes of the knee joint and, group 3, 54 patients with knee osteoarthritis who underwent computer-assisted total knee arthroplasty.

RESULTS

The coronal alignment of tibial plateaus averaged 2.4° with no significant differences between groups. The mean coronal orientation of tibial plateaus was 3° ± 2° in men and 1.6° ± 2° in women (p = 0.03). A coronal alignment of tibial plateaus of 3° or more was found in 69 cases (45%) and 5° or more in 23 (14.7%). The simulation of a tibial cut performed with an error of 3° in varus in 15% of the subjects showing a native coronal orientation of tibial plateaus of 3° or more, led to a final tibial cut greater 6° in 13.7% of cases.

CONCLUSIONS

A coronal alignment of tibial plateaus of 3° or more in varus was found in near half of normal subjects and osteoarthritic patients. A preoperative measurement of the coronal alignment of tibial plateaus is advisable in any patients scheduled for kinematic aligned TKA. As errors in the alignment of the tibial component of 3° or more may occur using standard instrumentations, the results of this study raise questions on performing a kinematic aligned TKA with standard instrumentations.

LEVEL OF EVIDENCE

IV.

Relationship Between Coronal Alignment and Rotational Profile of Lower Extremity in Patients With Knee Osteoarthritis

BACKGROUND

We aimed at determining whether the coronal alignment of lower extremity was related to rotational geometry of distal femur, femoral anteversion, and tibial torsion in patients with knee osteoarthritis.

METHODS

A total of 422 lower extremities were divided into 3 groups according to the coronal alignment: valgus (n = 31), neutral (n = 78), and varus group (n = 313). Condylar twisting angle was measured to determine rotational geometry of distal femur as the angle between the clinical transepicondylar axis and the posterior condylar line. Femoral anteversion was assessed using the angle between a line intersecting the femoral neck and the posterior condylar line (pFeAV) and the angle between the same line and transepicondylar axis that is not affected by posterior condylar variations (tFeAV). Tibial torsion was evaluated by measuring the angle between the posterior condyles of the proximal tibia and the transmalleolar axis.

RESULTS

As the coronal alignment changed from varus to valgus, the condylar twisting angle increased (r = 0.253, P < .001; 6.6° in varus, 7.4° in neutral, and 10.2° in valgus group). Although the pFeAV also increased (r = 0.145, P = .003), the tFeAV did not change significantly (P = .218). Mean tFeAV was 4.3° in varus, 4.7° in neutral, and 6.5° in valgus group. In contrast, as the coronal alignment changed from varus to valgus, the external tibial torsion increased (r = 0.374, P < .001; 22.6° in varus, 26.3° in neutral, and 32.6° in valgus group).

CONCLUSION

The change patterns of the rotational profiles of the lower extremity according to the coronal alignment should be considered in order to obtain satisfactory rotational alignment after TKA.

Posterior tibial slope impacts intraoperatively measured mid-flexion anteroposterior kinematics during cruciate-retaining total knee arthroplasty

PURPOSE

Posterior tibial slope (PTS) for cruciate-retaining (CR) total knee arthroplasty (TKA) is usually pre-determined by the surgeon. Limited information is available comparing different choices of PTS on the kinematics of the CR TKA, independent of the balancing of the extension gap. This study hypothesized that with the same balanced extension gap, the choice of PTS significantly impacts the intraoperatively measured kinematics of CR TKA.

METHODS

Navigated CR TKAs were performed on seven fresh-frozen cadavers with healthy knees and intact posterior cruciate ligament (PCL). A custom designed tibial baseplate was implanted to allow in situ modification of the PTS, which altered the flexion gap but maintained the extension gap. Knee kinematics were measured by performing passive range of motion (ROM) tests from full extension to 120° of flexion on the intact knee and CR TKAs with four different PTSs (1°, 4°, 7°, and 10°). The measured kinematics were compared across test conditions to assess the impact of PTS.

RESULTS

With a consistent extension gap, the change of PTS had significant impact on the anteroposterior (AP) kinematics of the CR TKA knees in mid-flexion range (45°-90°), but not so much for the high-flexion range (90°-120°). No considerable impacts were found on internal/external (I/E) rotation and hip-knee-ankle (HKA) angle. However, the findings on the individual basis suggested the impact of PTS on I/E rotation and HKA angle may be patient-specific.

CONCLUSIONS

The data suggested that the choice of PTS had the greatest impact on the mid-flexion AP translation among the intraoperatively measured kinematics. This impact may be considered while making surgical decisions in the context of AP kinematics. When using a tibial component designed with "center" pivoting PTS, a surgeon may be able to fine tune the PTS to achieve proper mid-flexion AP stability.

The orientation of the surgical epicondylar axis varies in varus and non-varus knees in the coronal plane

PURPOSE

To investigate the orientations of the surgical epicondylar axis (SEA) of varus and non-varus knees in the coronal plane.

METHODS

One-hundred and sixty-two knees from 81 Chinese patients undergoing total knee arthroplasty (TKA) were retrospectively investigated. The angle between the medial side of the femoral mechanical axis and the SEA (MA-SEA), as well as the physiological valgus angle, was measured in the coronal plane using three-dimensional reconstruction. The joint line angle (JLA) and hip-knee-ankle angle (HKAA) were measured in long-leg weight-bearing radiographs. The mean of each parameter was compared between the varus (HKAA < 177.0°) and the non-varus knees (HKAA ≥ 177.0°) using an independent t test. Linear regression was used to assess the correlation between MA-SEA with JLA and HKAA.

RESULTS

A total of 42 non-varus knees (6 valgus and 36 neutral knees) and 98 varus knees were measured, as 22 knees were abandoned due to unrecognizable bony landmarks. The mean MA-SEA and JLA were significantly larger in non-varus knees (both, p < 0.01). The mean physiological valgus angle was 5.9 ± 1.0° for Chinese TKA patients and was significantly larger in varus knees (p < 0.01). There was a strong positive correlation between the MA-SEA and JLA (R ² = 0.35, p < 0.05).

CONCLUSIONS

There were significant differences in the orientation of the SEA between varus and non-varus knees, which was strongly correlated with the orientation of the femoral joint line. These findings will enhance the current knowledge of knee anatomy and should prove useful for coronal alignment in TKA.

LEVEL OF EVIDENCE

III.

Tibiofemoral joint congruence is lower in females with ACL injuries than males with ACL injuries

PURPOSE

Previous research has demonstrated that women have a higher risk of anterior cruciate ligament (ACL) injury than men. Tibiofemoral articular geometry may play a role in the occurrence of ACL tears. The purpose of this study was to analyze the gender-specific geometric characteristics differences in tibiofemoral morphology in ACL-deficient patients.

METHODS

Medial tibial slope (MTS), lateral tibial slope (LTS), medial tibial plateau concavity, medial and lateral femoral condyle convexity, and lateral plateau convexity were analyzed in 276 patients with complete ACL injuries (138 females and 138 males). Two blinded observers measured the anatomical parameters of tibiofemoral geometry with use of multiplanar CT scans. Intra- and inter-rater reliabilities were assessed and comparisons between anatomic measures were made between male and female patients.

RESULTS

The average ICC for all measurements was 0.90 (range 0.83-0.97) indicating good reliability. Male ACL injured patients demonstrated significantly greater LTS (10.5° ± 2.8) than female patients (9.6° ± 3.5°; p < 0.05). No gender difference in MTS was found (n.s.). Medial and lateral femoral condyle convexity and medial tibial plateau concavity were greater in males than females (all p < 0.05). Lateral tibial plateau convexity in females was higher than in males (p < 0.001). The medial and lateral compartments were found to be more incongruent in females than males (p < 0.01 and p < 0.001, respectively).

CONCLUSIONS

Female patients were noted to have more incongruent medial and lateral compartments than male patients. These gender-specific differences in joint morphology may contribute to graft tear risk and outcomes of ACL reconstruction; however, comparative clinical studies are needed to confirm this possibility.

LEVEL OF EVIDENCE

3.

Kinematic alignment technique for total hip and knee arthroplasty: The personalized implant positioning surgery

Conventional techniques for hip and knee arthroplasty have led to good long-term clinical outcomes, but complications remain despite better surgical precision and improvements in implant design and quality.

Technological improvements and a better understanding of joint kinematics have facilitated the progression to ‘personalized’ implant positioning (kinematic alignment) for total hip (THA) and knee (TKA) arthroplasty, the true value of which remains to be determined.

By achieving a true knee resurfacing, the kinematic alignment (KA) technique for TKA aims at aligning the components with the physiological kinematic axes of the knee and restoring the constitutional tibio-femoral joint line frontal and axial orientation and soft-tissue laxity.

The KA technique for THA aims at restoring the native ‘combined femoro-acetabular anteversion’ and the hip’s centre of rotation, and occasionally adjusting the cup position and design based on the assessment of the individual spine-hip relation.

The key element for optimal prosthetic joint kinematics (hip or knee) is to reproduce the femoral anatomy.

The transverse acetabular ligament (TAL) is the reference landmark to adjust the cup position.

Cite this article: EFORT Open Rev 2018;3:98-105. DOI: 10.1302/2058-5241.3.170022

Alignment options for total knee arthroplasty: A systematic review

In spite of improvements in implant designs and surgical precision, functional outcomes of mechanically aligned total knee arthroplasty (MA TKA) have plateaued. This suggests probable technical intrinsic limitations that few alternate more anatomical recently promoted surgical techniques are trying to solve. This review aims at (1) classifying the different options to frontally align TKA implants, (2) at comparing their safety and efficacy with the one from MA TKAs, therefore answering the following questions: does alternative techniques to position TKA improve functional outcomes of TKA (question 1)? Is there any pathoanatomy not suitable for kinematic implantation of a TKA (question 2)? A systematic review of the existing literature utilizing PubMed and Google Scholar search engines was performed in February 2017. Only studies published in peer-reviewed journals over the last ten years in either English or French were reviewed. We identified 569 reports, of which 13 met our eligibility criteria. Four alternative techniques to position a TKA are challenging the traditional MA technique: anatomic (AA), adjusted mechanical (aMA), kinematic (KA), and restricted kinematic (rKA) alignment techniques. Regarding osteoarthritic patients with slight to mid constitutional knee frontal deformity, the KA technique enables a faster recovery and generally generates higher functional TKA outcomes than the MA technique. Kinematic alignment for TKA is a new attractive technique for TKA at early to mid-term, but need longer follow-up in order to assess its true value. It is probable that some forms of pathoanatomy might affect longer-term clinical outcomes of KA TKA and make the rKA technique or additional surgical corrections (realignment osteotomy, retinacular ligament reconstruction etc.) relevant for this sub-group of patients. Longer follow-up is needed to define the best indication of each alternative surgical technique for TKA. Level I for question 1 (systematic review of Level I studies), level 4 for question 2.

Sex differences in femoral deformity determined using three-dimensional assessment for osteoarthritic knees

PURPOSE

To characterize femoral deformities and determine sex differences in varus knee osteoarthritis (OA), femoral morphology and limb alignment were evaluated by using three-dimensional (3D) assessment, comparing healthy, elderly volunteers with osteoarthritic knees.

METHODS

A total of 178 lower limbs of 169 subjects with knee osteoarthritis (136 women, 33 men; mean age 74.9 ± 5.2 years) and 80 lower limbs of 45 healthy, elderly subjects (24 women, 21 men; mean age 65 ± 4.9 years) were examined. A 3D extremity alignment assessment system was used to examine the subjects under weight-bearing conditions on biplanar long-leg radiographs using a 3D-to-2D image registration technique. The evaluation parameters were (1) femoral bowing in the coronal plane, (2) femoral bowing in the sagittal plane, (3) femoral neck anteversion, (4) hip-knee-ankle angle, and (5) femoral torsion.

RESULTS

Higher femoral lateral bowing and slightly higher femoral internal torsion in the proximal diaphysis were observed in women with OA compared with healthy subjects. No difference in the higher varus malalignment, no alteration in the femoral anterior bowing, and no difference in the lower femoral neck anteversion were found between men and women when comparing healthy and OA subjects.

CONCLUSIONS

The higher femoral lateral bowing and slightly higher femoral internal torsion in the proximal diaphysis in women are possibly a structural adaptation to mechanical use. The clinical significance is that the femoral deformities and the sex differences in knee OA have the potential to improve the understanding of the aetiology of primary varus knee OA.

LEVEL OF EVIDENCE

IV.

Referencing the sulcus line of the trochlear groove and removing intraoperative parallax errors improve femoral component rotation in total knee arthroplasty

PURPOSE

Firstly, to assess and compare the accuracy and reproducibility of the sulcus line compared to Whiteside's line. Secondly, to assess the accuracy of intraoperative techniques for using the rotational alignment of the trochlear groove to set femoral rotation. Thirdly, to assess the reproducibility of a trochlear alignment guide which removes parallax errors that occur when projecting the sulcus line onto the surface of the femur. Finally, to measure the result of combining the geometrically accurate sulcus line and the posterior condylar axis.

METHODS

Three surgeons measured eight rotational angles on ten cadaveric femora. This included Whiteside's line, the sulcus line and the techniques in which they can be referenced during surgery.

RESULTS

Relative to the anatomical epicondylar axis, the sulcus line (mean -2.8°, SD 2.0°, range -5.4° to 0.8°) had significantly lower variance (F = 5.16, p = 0.036) than Whiteside's line (mean -2.0°, SD 3.7°, range -6.0° to 3.4°). The trochlear alignment guide produced the best results of the intraoperative techniques by maintaining the accuracy of the sulcus line and projecting it onto the distal cut surface of the femur without change in rotational angle.

CONCLUSION

The sulcus line is more accurate and reproducible than Whiteside's line. Removing parallax errors during surgery improves femoral component rotation. The trochlear alignment guide produced accurate results suggesting that it may be beneficial in a clinical setting. Averaging the sulcus line and posterior condylar axis on the cut surface of the femur improved accuracy over the individual landmarks. Femoral component malrotation is a common cause of patient dissatisfaction and revision surgery. By isolating the rotational alignment of the trochlear groove using the sulcus line, and maintaining its accuracy with an intraoperative guide, we can decrease the risk of femoral component malrotation and improve patient outcomes.

A soft-tissue preserving method for evaluating the impact of posterior tibial slope on kinematics during cruciate-retaining total knee arthroplasty: A validation study

BACKGROUND

The reconstructed posterior tibial slope (PTS) plays a significant role in restoring knee kinematics in cruciate-retaining total knee arthroplasty. However, conventional methods for the investigation of PTS can be limited by sample size or prone to errors due to damages to the bone and/or soft tissues. The purpose of this study was to validate a novel method for the evaluation of the effects of PTS on knee kinematics.

METHODS

Seven computer-assisted cruciate-retaining TKAs were performed by two surgeons on healthy cadaveric knees. The implanted tibial baseplates allowed precise and easy modification of the PTS in situ. Knee kinematics were evaluated during passive full range of motion test. The evaluation was performed three times at each of the five PTSs in the order of 10°, seven degrees, four degrees, one degree, and back to ten degrees. The variability of the repeated measurements, inter-surgeon variation of the data, and test reproducibility were investigated.

RESULTS

The test method was shown to be highly repeatable (low root-mean-squared errors) and has low sensitivity to surgeon variability (ANOVA). No statistical difference was found in the knee kinematics between the first and last measurements at 10° PTS (paired t-test).

CONCLUSION

The results suggested that the developed method can be used to investigate the impact of PTS on knee kinematics without disrupting the soft-tissue environment of the knee. The use of the novel tibial baseplate allowed for adjusting the PTS without re-cutting the tibia and removing the components. The method may be applied to improve the future investigation of PTS.

Anthropometric measurements of tibial plateau and correlation with the current tibial implants

PURPOSE

The aim of the study was to make an anthropometric analysis at the resected surfaces of the proximal tibia in the Turkish population and to compare the data with the dimensions of tibial components in current use. We hypothesized that tibial components currently available on the market do not fulfil the requirements of this population and a new tibial component design may be required, especially for female patients with small stature.

METHODS

Anthropometric data from the proximal tibia of 226 knees in 226 Turkish subjects were measured using magnetic resonance imaging. We measured the mediolateral, middle anteroposterior, medial and lateral anteroposterior dimensions and the aspect ratio of the resected proximal tibial surface. All morphological data were compared with the dimensions of five contemporary tibial implants, including asymmetric and symmetric design types.

RESULTS

The dimensions of the tibial plateau of Turkish knees demonstrated significant differences according to gender (P < 0.05). Among the different tibial implants reviewed, neither asymmetric nor symmetric designs exhibited a perfect conformity to proximal tibial morphology in size and shape. The vast majority of tibial implants involved in this study tend to overhang anteroposteriorly, and a statistically significant number of women (21 %, P < 0.05) had tibial anteroposterior diameters smaller than the smallest available tibial component.

CONCLUSION

Tibial components designed according to anthropometric measurements of Western populations do not perfectly meet the requirements of Turkish population. These data could provide the basis for designing the optimal and smaller tibial component for this population, especially for women, is required for best fit.

LEVEL OF EVIDENCE

II.