Stephen Miller Howell

Stephen Miller Howell
University of California, Davis | UCD · Department of Biomedical Engineering

MD

About

284
Publications
83,644
Reads
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11,792
Citations
Additional affiliations
July 2017 - July 2018
Adventist Health Lodi Memorial Hospital
Position
  • Orthopedic Surgeon
January 1997 - December 2012
University of California, Davis
January 1990 - August 2015
University of California, Davis
Position
  • Professor of Mechanical Engineering, Orthopedic Surgeon in Private Practice
Education
September 1979 - June 1981
Northwestern University
Field of study
  • Medicine

Publications

Publications (284)
Article
Full-text available
Purpose In total knee arthroplasty (TKA) with posterior cruciate ligament (PCL) retention, the medial and lateral insert conformity that restores in vivo native (i.e., healthy) knee tibial rotation and high function without causing stiffness is unknown. The purpose was to determine whether a ball-in-socket (B-in-S) medially conforming (MC) and flat...
Article
Full-text available
The primary aim was to analyze unrestricted kinematic alignment (unKA) total knee arthroplasty (TKA) and determine the frequency of medial deviation of the prosthetic trochlear angle (PTA) of the femoral component relative to the quadriceps vector (QV) that terminates at the anterior inferior iliac spine (AIIS), and whether patients with medial dev...
Article
Full-text available
Background: The preceding study reported a 10-year follow-up of 222 kinematically aligned (KA) total knee arthroplasties (TKA) performed in 217 patients in 2007. As 35% of tibial components and 8% of limbs were in > 3° varus, the present study assessed whether this adversely affected reoperation, implant survival, and function at 16 years. Methods...
Article
Background: Although retaining the posterior cruciate ligament (PCL) is advantageous in unrestricted kinematically aligned TKA, it is often excised with a medial stabilized implant. The primary objectives were to determine whether PCL retention using an insert with ball-in-socket (B-in-S) medial conformity to maximize A-P stability promotes intern...
Article
Introduction: There are no reports as to whether the condition of the anterior cruciate ligament (ACL) adversely affects the 2 to 3 year function and reoperation risk of a kinematically aligned (KA) total knee arthroplasty (TKA) performed with posterior cruciate ligament (PCL) retention and an intermediate medial conforming (MC) insert. Methods:...
Article
Full-text available
Purpose For a new tibial insert design with ball-in-socket (B-in-S) medial conformity (MC), posterior cruciate ligament (PCL) retention, and flat lateral articular surface (B-in-S MC + PCL), this study determined whether internal tibial rotation and knee flexion were limited and clinical outcome scores were lower during weight-bearing activities re...
Article
Background: One method for assessing the accuracy of manual, patient-specific, navigational, and robotic-assisted total knee arthroplasty (TKA) instrumentation is to use a post-operative computer tomogram and determine the deviation of the femoral component alignment relative to the planned alignment in the native (i.e. healthy) contralateral dist...
Article
Peer-reviewed studies published up to May 2022 are used to provide a comprehensive understanding of unrestricted kinematically aligned total knee arthroplasty. The intent is to cultivate the curiosity of those interested in this method of personalized alignment. The rationale of unrestricted kinematic alignment is to set the femoral and tibial comp...
Article
Full-text available
Background: A concern about kinematically aligned (KA) total knee arthroplasty (TKA) is that it relies on femoral components designed for mechanical alignment (MAd-FC) that could affect patellar tracking, in part, because of a trochlear groove orientation that is typically 6° from vertical. KA sets the femoral component coincident to the patient's...
Article
PurposeVarus alignment of the tibial baseplate and limb > 3° might adversely affect baseplate fixation after total knee arthroplasty (TKA), especially for unrestricted kinematically aligned (KA) TKA which aligns a majority of baseplates in varus. The purposes of this study were to determine whether baseplate migration at 1 year (1) was significantl...
Article
Full-text available
Background: Unrestricted caliper-verified kinematically aligned (KA) TKA restores patient's prearthritic coronal and sagittal alignments, which have a wide range containing outliers that concern the surgeon practicing mechanical alignment (MA). Therefore, knowing which radiographic parameters are associated with dissatisfaction could help a surgeo...
Article
Full-text available
As the conformity of a medial ball-in-socket total knee arthroplasty (TKA) provides intrinsic anterior-posterior (A-P) stability, surgeons cannot rely on the manual examination of sagittal laxity to identify the optimal insert thickness. Instead, the present study determined whether measuring tibial axial orientation in extension and 90° flexion wi...
Article
Full-text available
Background: In total knee arthroplasty (TKA), inserts can have different levels of medial and lateral congruency determined by the acuteness of the upslopes of the anterior and posterior articular surfaces. The present study evaluated an insert with different levels of lateral congruency and a medial ball-in-socket congruency to test the hypothesi...
Article
Because model-based radiostereometric analysis (MBRSA) identifies tibial baseplate designs which increase risk of baseplate loosening, and because registration errors for computer-aided-design (CAD) models are large relative to a 6-month stability limit, 3D models more representative of the geometry of implanted baseplates are needed to minimize er...
Article
Full-text available
After starting an orthopedic practice, a surgeon with a fellowship in mechanically aligned (MA) TKA initiated this study to characterize their learning curve after they switched to unrestricted kinematic alignment (KA) TKA using manual instruments. Accordingly, the present study determined for the inexperienced (IE) surgeon the number of cases requ...
Article
Purpose: Because different targets are used for internal-external rotation, an asymmetric baseplate designed for mechanical alignment may lead to under-coverage and concomitant posterior rim loading in the lateral compartment following unrestricted kinematic alignment (KA) TKA. Recognizing that such loading can lead to premature wear and/or subsid...
Article
Full-text available
Purpose Surgeons performing total knee arthroplasty (TKA) are interested in the accuracy and time it takes to make the four femoral resections that determine the setting of the femoral component. A method for quantifying the error of each resection is the thickness, measured by a caliper, minus the femoral target. The present study tested the hypot...
Article
Full-text available
Manipulation under anesthesia (MUA) for stiffness within 6 to 12 weeks after mechanically aligned total knee arthroplasty (TKA) generally yields better outcome scores than an MUA performed later. However, the timing of MUA after unrestricted, caliper-verified, kinematically aligned (KA) TKA remains uncertain. A retrospective review identified 82 of...
Chapter
This chapter contains discussion and video links that assist the surgeon in performing calipered kinematically aligned (KA) total knee arthroplasty (TKA) with specific manual instruments, a verification worksheet, and a decision tree. The treatment of 4726 primary TKAs performed from 2009 through 2019 with KA to restore the patient’s prearthritic j...
Chapter
The discussion and video links in this chapter assist the surgeon in 1) reducing the risk of aseptic loosening of the tibial component and 2) managing both early and late tibial component failure from insert wear after calipered kinematically aligned (KA) total knee arthroplasty (TKA). The chapter draws from the author's experience in treating over...
Chapter
This chapter contains a discussion and video links to assist the surgeon in reducing the risk of stiffness and in managing stiffness after calipered kinematically aligned (KA) total knee arthroplasty (TKA). The treatment of over 5300 primary TKAs from 2006 to 2020 with the anatomic target of restoring the patient’s prearthritic femoral and tibial j...
Chapter
This chapter contains discussion and video links that assist the surgeon in (1) reducing the risk of early-onset tibiofemoral instability, and (2) managing the instability when it occurs after calipered kinematically aligned (KA) total knee arthroplasty (TKA). The chapter draws from the author’s experience treating over 1527 primary TKAs implanted...
Chapter
Full-text available
Surgical site infections (SSI) is one of the most common postoperative adverse events after total knee replacement (TKA). SSI is associated with increased length of stay, higher costs, and significant morbidity for the patient and is the most common indication for revision in TKA. SSI prevention should target all presurgical, surgical, and postsurg...
Article
Full-text available
Purpose Excision of the posterior cruciate ligament (PCL) is recommended when implanting a medial pivot (MP) total knee arthroplasty (TKA) to reduce the risk of limiting flexion by over-tensioning the flexion space. The present study determined whether PCL retention (1) limits internal tibial rotation and (2) causes anterior lift-off of the insert...
Article
Full-text available
Introduction In total knee arthroplasty (TKA), the level of conformity, a medial stabilized (MS) implant, needs to restore native (i.e., healthy) knee kinematics without over-tensioning the flexion space when the surgeon chooses to retain the posterior cruciate ligament (PCL) is unknown. Whether an insert with a medial ball-in-socket conformity and...
Article
Most medial stabilized (MS) total knee arthroplasty (TKA) implants recommend excision of the posterior cruciate ligament (PCL), which eliminates the ligament's tension effect on the tibia that drives tibial rotation and compromises passive internal tibial rotation in flexion. Whether increasing the insert thickness and reducing the posterior tibial...
Article
PurposeTibial insert conformity in total knee arthroplasty (TKA) is of interest due to the potential effect on tibiofemoral kinematics. This study determined differences in anterior–posterior movements of the femoral condyles, pivot locations, and internal tibial rotation in different arcs of flexion for two implants with different insert conformit...
Article
Full-text available
Introduction: The calipered kinematically-aligned (KA) total knee arthroplasty (TKA) strives to restore the patient's individual pre-arthritic (i.e., native) posterior tibial slope when retaining the posterior cruciate ligament (PCL). Deviations from the patient's individual pre-arthritic posterior slope tighten and slacken the PCL in flexion that...
Article
Calipered kinematically aligned (KA) total knee arthroplasty (TKA) restores the patient's prearthritic joint lines and sets internal-external rotation of the tibial component parallel to the flexion-extension (FE) plane, which is not a mechanical alignment (MA) target. Two asymmetric tibial components designed for MA set the tibial component to eit...
Article
Full-text available
Purpose The present study determined the postoperative phenotypes after unrestricted calipered kinematically aligned (KA) total knee arthroplasty (TKA), whether any phenotypes were associated with reoperation, implant revision, and lower outcome scores at 4 years, and whether the proportion of TKAs within each phenotype was comparable to those of t...
Article
Accuracy of model-based radiostereometric analysis (MBRSA) in calculating tibial baseplate migration depends on baseplate shape and orientation relative to the imaging planes. The primary objectives were to introduce a new method for determining the optimal baseplate orientation to minimize bias error during MBRSA and to demonstrate the clinical us...
Article
Patellofemoral complications following total knee arthroplasty can be traced in part to alignment of the femoral component. Kinematic alignment (KA) and mechanical alignment (MA) use the same femoral component but align the component differently. Our objective was to determine differences in trochlear morphology from native for a femoral component...
Chapter
Full-text available
This chapter presents the philosophy of kinematic alignment (KA) and the surgical technique for setting the positions of the components using ten calipered measurements, manual instruments, and nine verification checks. The adoption of KA is increasing. Four meta-analyses, three randomized trials, and a national multicenter study showed that patien...
Article
Identifying and correcting varus‐valgus (V‐V) malalignment of the tibial component is important when balancing a kinematically aligned total knee arthroplasty (TKA). Accordingly, the primary objective was to determine whether the tibial forces or V‐V laxities are more sensitive to, and thus more useful for identifying and correcting, V‐V malalignme...
Article
There are no reports of in vivo internal–external (I–E) rotational alignment and coverage of the proximal tibia after performing a best-fit method of an anatomically designed and asymmetrically shaped tibial baseplate during calipered kinematically aligned (KA) total knee arthroplasty (TKA). We hypothesized that a best-fit plane sets the anterior–p...
Article
Full-text available
Recently, personalized medicine applied here as individualized surgery, which represents the customization in insertion sites, size of the graft, tunnel placement, and graft tension for each individual patient, has been proposed. A question is whether the surgeon’s task defines the level of analysis. The alternative presented here proposes the view...
Article
Full-text available
PurposeSurgeons performing total knee arthroplasty (TKA) on the osteoarthritic valgus deformity often use a posterior stabilized (PS) and semi-constrained implants to substitute for the release of a contracted posterior cruciate ligament (PCL) instead of a cruciate retaining (CR) implant. Calipered kinematic alignment (KA) strives to retain the PCL...
Article
Full-text available
Kinematically aligned total knee arthroplasty (TKA) is a new alignment technique. Kinematic alignment corrects arthritic deformity to the patient's constitutional alignment in order to position the femoral and tibial components, as well as to restore the knee's natural tibial-femoral articular surface, alignment, and natural laxity. Kinematic knee...
Article
The objectives were to determine errors in femoral anteversion (FA), femoral offset (FO), and vertical offset (VO) with robot‐assisted total hip arthroplasty (THA) and how consistently these errors are within clinically desirable limits of ± 5° and ± 5 mm. After preoperative planning, robot‐assisted THAs were performed on twelve cadaveric specimens...
Preprint
Full-text available
Identifying and correcting varus-valgus (V-V) malalignment of the tibial component is important when balancing a kinematically aligned total knee arthroplasty (TKA). Accordingly, the primary objective was to determine whether the tibial forces or V-V laxities are more sensitive to, and thus more useful for identifying and correcting, V-V malalignme...
Article
Purpose Kinematically aligned total knee arthroplasty (KA TKA) strives to restore the native distal and posterior joint lines of the femur. Because the joint lines of a virtually planned femoral component on the native femur can serve as surrogates of those of the native femur, the present study determined position and orientation deviations of the...
Article
Revision of a medial unicompartmental knee arthroplasty (UKA) to a mechanically aligned total knee arthroplasty (MA TKA) is inferior to a primary TKA; however, revision with kinematic alignment (KA) has not been well studied. The present study determined whether patients revised with KA had a higher use of revision components, different postoperati...
Article
Purpose Kinematically aligned (KA) TKA strives to restore native limb and knee alignments without ligament release with the premise that knee function likewise will be closely restored to native to the extent enabled by the components used. This study determined differences in anterior–posterior (AP) tibial contact locations of a KA TKA performed w...
Article
Background: Closely approximating the functional flexion-extension (FE) axis of the tibiofemoral joint in 3D models of the femur is important when computing joint motions which are physiologic. The objectives were to 1) develop methods to approximate the functional FE axis based on fitting circles, a tapered cylinder, and spheres to the posterior c...
Article
Prior studies suggest kinematically aligned (KA) total knee arthroplasty (TKA) provides some clinical benefits. There are no reports of self-reported outcome measures in patients treated with a calipered KA TKA that already had a contralateral mechanically aligned (MA) TKA. We performed a retrospective study and asked the following questions: (1) W...
Article
Purpose Although patellofemoral complications after kinematically aligned (KA) TKA are infrequent, the patellar flexion angle and proximal–distal patellar contact location through flexion, and incidence of patellar loss of contact at full extension are unknown. The present study determined whether the patellar flexion angle and proximal–distal pate...
Conference Paper
Full-text available
Introduction There are concerns that postoperative varus or valgus outlier alignment of the tibial component, knee, and limb might adversely affect the long-term results of kinematically aligned (KA) TKA particularly when patients are selected without restrictions based on the severity of the preoperative varus-valgus and flexion deformities. Meth...
Article
Full-text available
Kinematic alignment performed with caliper measurements and verification checks accurately co-align the femoral and tibial components with the 3 axes and joint lines of the native knee without ligament release and without restrictions on the degree of preoperative varus, valgus, flexion, and extension deformities and the degree of postoperative cor...
Article
Background: Loss of contact between the femoral and tibial implants following total knee arthroplasty (TKA) has been related to accelerated polyethylene wear and other complications. Two methods have been used to detect loss of contact in single-plane fluoroscopy, the condylar lift-off method and the separation method. The objectives were to asses...
Article
Three dimensional models of the femur and tibia from MRI and CT are used in various studies of knee biomechanics but morphological errors occur. The objectives were to determine the morphological errors in 3D bone models from MRI and CT using clinically-adopted imaging protocols, to determine whether these errors are affected by the method of regis...
Article
Full-text available
Background Four mechanical alignment force targets are used to predict early patient-reported outcomes and/or to indicate a balanced TKA. For surgeons who use kinematic alignment, there are no reported force targets. To date the usefulness of these mechanical alignment force targets with kinematic alignment has not been reported nor has a specific...
Article
We hypothesized that a total knee arthroplasty (TKA) with an intraoperative tibial force greater than the tibial force of the native knee has signs of stiffness as measured by loss of extension and flexion, and anterior translation of the tibia. Intraoperative forces in the medial and lateral tibial compartments were measured during passive motion...
Article
Résumé Introduction Restaurer l’anatomie native fémoropatellaire lors de la réalisation d’une prothèse totale de genou (PTG) alignée cinématiquement (AC) pourrait être cliniquement bénéfique. Cette étude visait à comparer les paramètres anatomiques de la trochlée native et prothétique AC lorsque celle-ci a été planifiée et implantée (objectif 1),...
Article
Purpose Kinematic alignment (KA) and mechanical alignment (MA) position the prosthetic trochlea that guides patellar tracking differently. The present study determined whether KA or MA more closely restores the groove location and sulcus angle of the prosthetic trochlea to the native trochlea for three femoral component designs. Methods Ten 3D fem...
Article
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. Methods A retrospective revi...
Article
Background: The OrthoSensor VERASENSE knee system is a commercially available instrumented tibial insert that provides real-time intraoperative measurements of tibial contact force and contact location to guide surgeons toward improving outcomes in total knee arthroplasty (TKA). However, the device has been used contrary to the manufacturer's reco...
Conference Paper
Full-text available
The present study reviewed patients treated with kinematically aligned (KA) TKA and determined whether hitting the mechanical alignment force targets of Gustke, Jacobs, Meere, and Meneghini resulted in better patient reported outcomes and whether there is a force target for KA that separates subjects with better Oxford Knee Scores (OKS) of >34 (goo...
Chapter
Full-text available
Osteoarthritis with a varus deformity is one of the most common deformities presenting for total knee arthroplasty. At the present time, there are various options for correcting a fixed varus deformity, but it is well accepted that accurate soft tissue balance with restoration of the mechanical alignment of the knee joint is critical to a successfu...
Article
Purpose: The purposes of this study were to quantify the increase in tibial force imbalance (i.e. magnitude of difference between medial and lateral tibial forces) and changes in laxities caused by 2° and 4° of varus-valgus (V-V) malalignment of the femoral component in kinematically aligned total knee arthroplasty (TKA) and use the results to det...
Article
Full-text available
Introduction: We determined (1) the range of the hip-knee-ankle (HKA) angle in the native or pre-arthritic limbs of patients with a contralateral total knee arthroplasty (TKA); and when mechanical alignment is planned (2) the relationships between the HKA angle and the tibial width, and the relative narrowing between the medial and lateral compart...
Article
Full-text available
Background: Kinematically aligned total knee arthroplasty strives to correct the arthritic deformity by restoring the native tibial joint line. However, the precision of such surgical correction needs to be quantified in order to reduce recuts of the resection and to design assisting instrumentation. This study describes a method for novel three-d...
Article
Purpose: The purposes of this study were to quantify the increase in tibial force imbalance (i.e. magnitude of difference between medial and lateral tibial forces) and changes in laxities caused by 2° and 4° of internal-external (I-E) malalignment of the femoral component in kinematically aligned total knee arthroplasty. Because I-E malalignment w...
Article
Full-text available
Aims The aims of this study were to determine the proportion of patients with outlier varus or valgus alignment in kinematically aligned total knee arthroplasty (TKA), whether those with outlier varus or valgus alignment have higher forces in the medial or lateral compartments of the knee than those with in-range alignment and whether measurements...
Article
Purpose: Following total knee arthroplasty (TKA), high tibial forces, large differences in tibial forces between the medial and lateral compartments, and anterior translation of the contact locations of the femoral component on the tibial component during passive flexion indicate abnormal knee function. Because the goal of kinematically aligned TK...
Article
Knowledge of A-P tibial contact locations provides an objective assessment of the relative motion of the tibia on the femur following total knee arthroplasty, which can be used to compare the effects of different components, surgical techniques, and alignment goals on knee function in vivo. Both the closest point method and the penetration method h...
Conference Paper
Full-text available
INTRODUCTION: Measurements of intraoperative medial and lateral tibial compartment forces determine balance after total knee arthroplasty (TKA). Medial compartment forces are high in osteoarthritic knees with varus deformities and lateral compartment forces are high in knees with valgus deformities. Accordingly, we asked: 1) Are the medial and late...
Conference Paper
Full-text available
INTRODUCTION: A well-balanced total knee arthroplasty (TKA) is necessary for long-term success. It is unknown whether using an insert 2mm thicker than implanted increases tibial compartment forces, increases anterior position of the tibia, and decreases knee motion. Accordingly, we asked: how much does an insert 2mm thicker than implanted increase...
Article
Introduction: 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 alternative more anatomical recently promoted surgical techniques are trying to solve. This review aims at (1)...
Article
Errors during a robot-assisted THA may result in a femoral cavity with position and orientation different than planned. This can lead to a femoral component placement that inaccurately sets a patient's femoral anteversion (FA), femoral offset (FO), and vertical offset (VO). The objectives of this study were to determine the position and orientation...
Article
Purpose: Eight patients treated with kinematically-aligned (KA) total knee arthroplasty (TKA) presented with tibial component failure. We determined whether radiographic measurements and clinical characteristics are different between patients with and without tibial component failure to identify mechanisms of failure and strategies to reduce the r...
Article
Analysis of anterior–posterior (A–P) tibial contact locations following total knee arthroplasty (TKA) provides an objective assessment of the relative motion of the tibia on the femur during activities of daily living. Determining A–P tibial contact locations using single-plane fluoroscopy requires input in the form of the relative 3D position and...
Chapter
Full-text available
Kinematically aligned total knee arthroplasty (TKA) has gained interest because two randomized trials and a national multicenter study showed that patients treated with kinematic alignment reported significantly better pain relief, function, flexion, a more normal-feeling knee than mechanical alignment with a similar implant survivorship at 2, 3, a...
Chapter
Full-text available
Soft tissue balance is a measure of the relative tensions in the soft tissue restraints of the knee. The soft tissues should be considered “balanced” when they are appropriately tensioned to stabilize the joint without causing stiffness, limited motion, or pain. The native knee is inherently stable and has adequate mobility to enable individuals to...